WO2018173553A1 - Coating film, method for producing coating film, and organic electroluminescence device - Google Patents

Abstract

Provided is a coating film comprising at least one kind of organic compound, wherein there is at least one maximum peak in a particle diameter distribution curve (horizontal axis: particle diameter, vertical axis: frequency distribution), of molecules or aggregates, obtained from small angle X-ray scattering measurement of the organic compound, and R and r below satisfy the relationship represented by equation (1). (1) R≤15r (In equation (1), R represents a particle diameter corresponding to the maximum peak showing the smallest particle diameter among the maximum peaks of the particle diameter distribution curve obtained from small angle X-ray scattering measurement, and r represents the molecular radius of the organic compound, r=(a×b)^1/2, when the molecular major axis length of the organic compound as calculated by density functional theory is 2a (nm), and the molecular minor axis length of the organic compound as calculated by density functional theory is 2b (nm).

Description

Coating film, coating film manufacturing method, and organic electroluminescence element

The present invention relates to a coating film, a manufacturing method of the coating film, and an organic electroluminescence element, and in particular, an object thereof is to provide a coating film having a small particle size of organic compound particles in the film and a manufacturing method thereof, It is to provide an organic electroluminescence device excellent in luminous efficiency and durability using the coating film.

1. Organic electronic device prevalence and current problems Electronic devices using organic compounds, such as organic electroluminescent elements (also referred to as “OLEDs”, “organic EL elements”), organic photoelectric conversion elements, and Various electronic devices such as organic transistors have been developed, and are spreading in various industrial and market fields along with their technological progress.
For example, organic EL elements, which are typical examples of organic electronic devices, have begun to be used in various fields such as displays, lighting, and indicators, and have already entered the current life together with liquid crystal displays and light emitting diodes (LEDs). From now on, we are about to enter a period of dramatic expansion.
However, in order to promote the development of organic electronic devices such as organic EL elements, many problems remain to be solved in the research and development process. In particular, various problems resulting from the use of organic compounds remain common or unique to various organic electronic devices. It can be said that these problems to be solved are ultimate problems directly connected to further improvement in performance such as quantum efficiency and light emission lifetime and further improvement in productivity, that is, cost reduction.

Among the above-mentioned ultimate issues, it seems that the performance issues have already reached a level sufficient for practical use.
On the other hand, productivity, that is, cost, has a greater problem than liquid crystal displays and light emitting diodes, and there is still much room for improvement.
In other words, improving productivity is a necessary condition for developing organic EL elements. This also applies to other organic electronic devices such as organic photoelectric conversion elements.
Thus, in the following, the problems of the prior art relating to the manufacture of organic EL elements, which are typical examples of organic electronic devices, will be described, particularly from the viewpoint of the ultimate problem relating to productivity.

2. Problems related to organic functional layer formation method First, a method for forming an organic functional layer, that is, a vacuum deposition method (also referred to as “vacuum deposition film formation method”) and a wet coating method (“wet coating method”, “wet coating”). The problem caused by the “film formation method” will be described.

2.1 Influence of moisture and oxygen on organic functional layer An organic EL element has an electron and a hole in a light emitting material (generally also referred to as “dopant”) present in a light emitting layer which is one of organic functional layers. The basic principle is that the exciton produced when the recombination occurs and emits light when returning to the ground state.
As the name suggests, this exciton is a very active chemical species that is in an excited state, so it easily reacts with water molecules and oxygen molecules, causing chemical changes or state changes such as decomposition and denaturation, and has a light-emitting property. It will decrease. That is, it is one of the factors that reduce the light emission lifetime.
That is, when an organic functional layer such as a light emitting layer is formed, it is necessary to perform it in an environment in which moisture and oxygen are strictly prevented during the formation process.
In addition, unlike an LED, in an organic EL element, the existence state of an organic compound that constitutes a light emitting layer is not a crystal but an amorphous (amorphous) condition. Therefore, in order to form a homogeneous amorphous film, it is desired that the molecular state (amorphous state) of the organic compound and the surrounding environment are constant during the film formation.
Therefore, the deposition method for the organic functional layer of the organic EL element exhibiting good performance so far is the vacuum deposition method, for the reasons such as prevention of harmful effects due to moisture and oxygen and the necessity of making the organic compound amorphous. It was due to. For organic EL displays for smartphones already mass-produced and organic EL displays used for large televisions, the vapor deposition method is employed as a method for forming the organic functional layer.

2.2 Problems of Formation of Organic Functional Layer by Vacuum Deposition Method However, when an organic EL element is produced by a vacuum deposition method, there are the following problems related to the emission color reproduction method.
Organic electroluminescence is self-luminous, and the luminescent color is uniquely determined by the luminescent material constituting the luminescent layer, so basically red (Red: R), green (Green: G), blue (Blue: B) A method (RGB side-by-side method) in which organic EL elements of respective emission colors are formed for each pixel and arrayed to form a display has been adopted.
In the case of the RGB side-by-side method, it is necessary to form a different light-emitting layer for each pixel, and in order to perform this in a large area, there is a method of forming each pixel while shifting the shadow mask for each pixel. It is common. At this time, since the formation (film formation) method of the light emitting layer or the like is a vacuum vapor deposition method, there is a decisive problem that the shadow mask is thermally expanded by the radiant heat from the vapor deposition source and causes pixel displacement.
Due to this critical problem, small to medium-sized displays for smartphones are produced in hundreds of millions of panels per year using the RGB side-by-side method. The production yield originated from the thermal deformation of the shadow mask is low, and large-scale production is not performed.
On the other hand, as another method for reproducing full color, a method (color filter method) in which white light obtained from an organic EL element is color-divided into RGB by passing through a color filter (color filter method) is employed. A large display that has already been mass-produced is an array of organic EL elements that emit white light for each pixel, and a shadow mask is not required for the color filter method, thereby improving the yield. However, the color filter method has a problem in that the advantages and characteristics of the organic EL element that can obtain light with high contrast with independent pixels cannot be fully exhibited.

2.3 Possibility of forming an organic functional layer by a wet coating method The organic functional layer constituting the organic EL element has a laminated structure of about 4 to 7 layers, and the total layer (film) thickness is about 100 to 200 nm. It is. If it is too thin, the anode and the cathode are partially short-circuited due to the surface roughness of the electrode serving as the underlayer, and a current leakage phenomenon occurs.
If the thickness is larger than this, the charge conduction mechanism of the organic EL element is different from Ohm's law, and is a space charge limited current (SCLC) according to the child law. Since it is inversely proportional to the third power of, a significant drive voltage rise occurs, resulting in a problem of increased power consumption.
The organic functional layer of an organic EL device is generally deposited by depositing a low molecular compound, but instead of the low molecular compound, a π-conjugated polymer such as polyphenylene vinylene or polyfluorene is used for carrier movement and light emission. There is also a method using a light emitting polymer (LEP) utilized for both. Since the polymer material cannot be formed by vapor deposition, the organic functional layer is produced by a wet coating method (wet film formation method, wet coating method) such as spin coating, die coating, flexographic printing, and inkjet printing.
Even for low-molecular compounds that can be deposited, it is possible to form a smooth coating film on the order of nanometers by appropriately selecting the molecular structure of the compound and the solvent to be dissolved. Minolta has announced a prototype of a phosphorescent white element that emits high-efficiency light by coating four layers of low-molecular compounds.
In view of the above circumstances, research and development for producing an organic EL element by a wet coating method (wet coating method) using a low molecular compound has been actively conducted.

There are several prior literatures on coating film forming methods that suppress the inclusion of large crystallites, but in general, the microcrystal size evaluation of the film is performed only by visual inspection, and the fine crystallography within the range that cannot be seen with the eyes. The possibility of crystal formation cannot be denied.
Furthermore, although there is a document that discloses a method for producing a vapor deposition type organic EL element including a thin film in which a diffraction peak due to microcrystals is not detected by X-ray diffraction, a low molecular coating type in which a diffraction peak due to X-ray diffraction is not detected The method for manufacturing the organic EL element remains as an unsolved problem.
In addition, it is known that a microcrystal peak is observed even in such a film in high energy, high directivity X-ray diffraction. In other words, it is suggested that the molecules are not sufficiently dispersed, and that some molecules are aggregated, resulting in the formation of domains (aggregated clusters or voids), resulting in even higher luminous efficiency (low driving voltage, etc.) ) Was not sufficient to obtain an organic EL device having a long lifetime.
For such a problem, a method of obtaining a light emitting layer for an organic electroluminescence element with few microcrystals by mixing various kinds of host materials and dopant materials is disclosed (Patent Document 1). In Patent Document 1, it is disclosed that the generation of microcrystals can be suppressed by combining a plurality of host materials and dopant materials, but the generation of microcrystals is controlled in a thin film made of a single kind of material. Whether or not is disclosed.

International Publication No. 2013/042446

The present invention has been made in view of the above-mentioned problems and situations, and the problem to be solved is that even when a single type of material is used, there are few microcrystals, in other words, the particle size of the organic compound particles in the film ( It is to provide a coating film having a small domain size), a coating film manufacturing method for manufacturing the coating film, and to provide an organic electroluminescence device excellent in luminous efficiency and durability using the coating film. It is.

In order to solve the above-mentioned problems, the present inventor, in the process of examining the cause of the above-mentioned problem, is a coating film composed of at least a single kind of organic compound molecule, and molecules or aggregates obtained from small-angle X-ray scattering measurement. A coating film having an organic compound having at least one maximum peak in a diameter distribution curve and satisfying a specific relational formula, and having a small particle size of organic compound particles in the film, and a method for producing the coating film In addition, the present inventors have found that an organic electroluminescence element excellent in luminous efficiency and durability can be provided, and have reached the present invention.
That is, the said subject which concerns on this invention is solved by the following means.
1. A coating film comprising at least a single organic compound,
Having at least one maximum peak in the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of the molecule or aggregate obtained from the small angle X-ray scattering measurement, and
The coating film containing the organic compound which the following R and r satisfy | fill the relationship represented by following formula (1).
Formula (1): R <= 15r
[In Formula (1), R represents the particle size corresponding to the maximum peak which shows a particle size with the smallest particle size among the maximum peaks of the particle size distribution curve obtained from a small angle X-ray scattering measurement. When the molecular long axis length obtained by density functional theory calculation for the organic compound is 2a (nm) and the molecular short axis length is 2b (nm), the molecular radius of the organic compound r = (A × b) represents ^1/2 . ]

2. The coating film according to claim 1, wherein R represents a particle size corresponding to a maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve.

3. The coating film according to the first or second item, wherein the frequency distribution of the maximum peak satisfying the formula (1) is 0.4 or more.

4). 4. The coating film according to any one of items 1 to 3, which satisfies the following formula (2).
Formula (2): R ≦ 8r
[In Formula (2), R and r are synonymous with R and r in said Formula (1). ]

5. The coated film according to any one of items 1 to 4, wherein a half-value width of a maximum peak satisfying the formula (1) is in a range of 0.3 to 3.0 nm.

6. The coating film as described in any one of 1st term | claim-5th item | term containing the multiple types of organic compound which satisfy | fills said Formula (1).

7). The following R ′ and r are films formed by solidifying a coating solution containing an organic compound that satisfies the relationship represented by the following formula (3), according to any one of items 1 to 6 Coating film.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ]

8). A manufacturing method of a coating film for manufacturing the coating film according to any one of items 1 to 7,
A step of preparing a coating solution containing an organic compound in which R ′ and r below satisfy the relationship represented by the following formula (3);
And a step of drying and solidifying the coating solution.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ]

9. The organic electroluminescent element which has the coating film as described in any one of Claim 1- 7 in at least 1 layer of an organic functional layer.

10. The organic electroluminescent element according to item 9, wherein the organic functional layer is a light emitting layer.

In order to facilitate understanding of the present invention, the basic policy according to the present invention and the background of research and development will be described later.
(Basic policy and background of research and development)
Based on the technical background described above, it is assumed that the technology to be employed in the method for producing a coating film of the present invention is inevitably selected as follows.
<Basic policy on manufacturing method>
(1) The organic compound is preferably a low molecular compound (a high molecular compound is not preferable).
(2) The film forming method is preferably a coating method (a vapor deposition method is not preferable).
(3) The solvent in the coating solution is preferably a general-purpose solvent (an expensive dehydrated high-purity solvent is not preferred).
(4) The dissolution is preferably in a monomolecular state (a microcrystalline dispersion is not preferred).
(5) Adsorption-desorption equilibrium is preferably used for purification of the compound (thermal equilibrium is not preferred).
First, when the basic policy as described above is adopted, creating a method that satisfies all of the policies (3) to (5) is a technical issue for the time being, and achieving it is the most valuable technology. I think there is, and I have been researching and developing the means to achieve it.
As a result, in order to achieve the “(4) Dissolution is preferably in a single molecule state”, it was considered important to disperse molecules. Examples of the method for dispersing the solute aggregate in the solution include chromatography, ultrasonic or microwave irradiation, and electrophoresis. Also, in the drying step, it is preferable to use a solvent having a solubility of solute of 5% by mass or less in order to suppress the interaction force between the solute and the solvent to a certain range or less and make the driving force for drying entropy. I found.

By the above means of the present invention, it is possible to provide a coating film in which the particle size of the organic compound particles in the film is small, a coating film manufacturing method for manufacturing the coating film, and luminous efficiency using the coating film And an organic electroluminescence element excellent in durability.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.
The present inventors have studied focusing on the material state from the application of the coating solution in which the material is dissolved until the film is formed. In other words, when the solute contained in the coating solution forms a film, what kind of state the solute is in the solution state of the coating solution and how it is solidified (coating) It is.
Compared to the coating method, in the case of the vapor deposition method, solid molecules are transformed into a gas phase by being heated in a vacuum, and the molecules move to the element substrate due to a thermal gradient. It is considered that a film is formed by transformation from a gas to a solid, and as a result, an amorphous film is formed.
From this reasoning, in order to obtain an amorphous film by the coating method, it was considered important that the molecules were highly dispersed before the film formation, that is, at the coating liquid (solution) stage. In general, it is known that a solute molecule forms a cluster in which several to several tens of tens of molecules gather in a coating solution. When a coating film is obtained in such a state, in the film formation process, It is thought that the clusters trigger the formation of microcrystals.
Specifically, as shown in FIG. 1, a solute molecule 20 forms a cluster 22 in which several molecules to several tens of molecules are gathered, and a large number of solvent molecules 21 exist around the cluster 22.
That is, molecules are highly dispersed at the coating liquid stage, that is, as shown in FIG. 11, a single solute molecule 20 (diameter 2r) is surrounded by a large number of solvent molecules 21, thereby forming a film. It is presumed that an amorphous film is formed by eliminating the cluster in the formation process.

Schematic diagram of one solute molecule present in the solvent A graph showing an example of particle size distribution curves for conventional deposited films and coated films The graph which shows an example of the particle size distribution curve in the coating film of this invention and a comparative example Schematic diagram of equipment using packed column in supercritical or subcritical chromatography Schematic diagram showing an example of a display device composed of organic EL elements Schematic diagram of display part A Schematic showing the pixel circuit Schematic diagram of passive matrix type full color display device Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element of a bulk heterojunction type Sectional drawing which shows the solar cell which consists of an organic photoelectric conversion element provided with a tandem type bulk heterojunction layer Schematic diagram of clusters of solute molecules present in the solvent

The coating film of the present invention is a coating film composed of at least one kind of organic compound, and is a particle size distribution curve of molecules or aggregates obtained from small angle X-ray scattering measurement (horizontal axis: particle size, vertical axis: frequency distribution). ) Contains at least one maximum peak, and R and r below contain an organic compound satisfying the relationship represented by the following formula (1).
Formula (1): R <= 15r
[In Formula (1), R represents the particle size corresponding to the maximum peak which shows a particle size with the smallest particle size among the maximum peaks of the particle size distribution curve obtained from a small angle X-ray scattering measurement. When the molecular long axis length obtained by density functional theory calculation for the organic compound is 2a (nm) and the molecular short axis length is 2b (nm), the molecular radius of the organic compound r = (A × b) represents ^1/2 . ]
This feature is a technical feature common to or corresponding to the invention according to the present embodiment.

As an embodiment of the present invention, the R represents a particle size corresponding to a maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. It is preferable in that it increases, that is, the homogeneity in the film increases.

Further, the frequency distribution of the maximum peak satisfying the formula (1) is 0.4 or more in that the degree of dispersion of the particle size in the coating film is high, that is, the homogeneity in the film is high. preferable.

Moreover, it is preferable that the following formula (2) is satisfied in that the particle size in the coating film can be further reduced.
Formula (2): R ≦ 8r
[In Formula (2), R and r are synonymous with R and r in said Formula (1). ]

In addition, it is preferable that the half width of the maximum peak satisfying the formula (1) is in the range of 0.3 to 3.0 nm from the viewpoint of uniform device characteristics.

In addition, it is preferable to contain a plurality of types of organic compounds satisfying the formula (1) from the viewpoint that the more solute types are, the more stable and the storage stability becomes.

Further, the following R ′ and r are films formed by solidifying a coating solution containing an organic compound that satisfies the relationship represented by the following formula (3), so that no cluster exists in the film forming process. And a coating film having a smaller particle diameter can be obtained.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ]

The method for producing a coating film of the present invention includes a step of preparing a coating solution containing an organic compound in which R ′ and r below satisfy the relationship represented by the following formula (3), and a step of drying and solidifying the coating solution It is characterized by having.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ]
By such a manufacturing method, since the molecules are highly dispersed at the coating liquid stage, it is possible to make a state in which no clusters exist in the film formation process, and it is possible to manufacture a coating film with a smaller particle size. .

The coating film of this invention is used suitably for the organic electroluminescent element which has in at least 1 layer of an organic functional layer.
Moreover, it is preferable that the organic functional layer is a light emitting layer from the viewpoint of light emitting element lifetime and light emitting efficiency.

Hereinafter, the present invention, its components, and modes and modes for carrying out the present invention will be described in detail. In the present application, “˜” is used to mean that the numerical values described before and after it are included as a lower limit value and an upper limit value. In the present invention, the ratios such as “%” and “ppm” are based on mass.

[Outline of Coating Film of the Present Invention]
The coating film of the present invention is a coating film composed of at least one kind of organic compound, and is a particle size distribution curve of molecules or aggregates obtained from small-angle X-ray scattering measurement (horizontal axis: particle size, vertical axis: frequency distribution). ) Contains at least one maximum peak, and R and r below contain an organic compound satisfying the relationship represented by the following formula (1).
Formula (1): R <= 15r
[In Formula (1), R represents the particle size corresponding to the maximum peak which shows a particle size with the smallest particle size among the maximum peaks of the particle size distribution curve obtained from a small angle X-ray scattering measurement. When the molecular long axis length obtained by density functional theory calculation for the organic compound is 2a (nm) and the molecular short axis length is 2b (nm), the molecular radius of the organic compound r = (A × b) represents ^1/2 . ]

As described above, the present invention has been studied and completed based on the following basic policies (1) to (5).
(1) The organic compound is preferably a low molecular compound (a high molecular compound is not preferable).
(2) The film forming method is preferably a coating method (a vapor deposition method is not preferable).
(3) The solvent in the coating solution is preferably a general-purpose solvent (an expensive dehydrated high-purity solvent is not preferred).
(4) The dissolution is preferably in a monomolecular state (a microcrystalline dispersion is not preferred).
(5) Adsorption-desorption equilibrium is preferably used for purification of the compound (thermal equilibrium is not preferred).
In the following, first, the present invention will be described from the viewpoint of the basic idea that is the basis for each of the above policies, and then specific techniques will be described.

1. Superiority of low molecular weight compounds over high molecular weight compounds In the formation of an organic functional layer by a wet coating method, the superiority of low molecular weight compounds over high molecular weight compounds will be described.
(First factor): Superiority of purity When a low molecular weight compound is compared with a high molecular weight compound (so-called polymer), the difference is well understood. First, it is preferable to apply sublimation purification to low molecular weight compounds because of their low molecular weight, and recrystallization is also desirable because of its low molecular weight distribution. In addition, high-performance liquid chromatography (HPLC) or column chromatography with low purification efficiency (low theoretical plate number) or column chromatography can be used as a method for purifying low-molecular compounds.
In the purification of a polymer compound, in most cases, the purification is performed by repeatedly performing a reprecipitation method using a good solvent and a poor solvent, and the low-molecular compound is more easily purified.
In addition, when the polymer compound is a π-conjugated polymer compound, it is necessary to use a metal catalyst or a polymerization initiator for causing a polymerization reaction, and a reactive active substituent remains at the polymerization terminal. This is one of the reasons why low molecular weight compounds can be made more pure.

(Second factor): Superiority regarding energy level peculiar to molecules Light emitting polymer (LEP) is a π-conjugated polymer when the molecular weight is increased, so that it is conjugated to stabilize the molecule. In order to expand the system, in principle, the energy level difference between the excited state of the singlet or triplet and the ground state (also referred to as “energy level gap” or “band gap”) becomes narrower. Blue light emission becomes difficult. In addition, in blue phosphorescence requiring a higher energy level (large energy level difference) than fluorescent blue light emission, it is structurally difficult for the light emitting polymer to form a transition metal complex serving as the light emitting substance. Further, even if a light-emitting polymer is used as a host, it is difficult to obtain a compound having high triplet energy (abbreviated as “high T ₁ compound”) due to the extension of the π-conjugate.

On the other hand, in the low molecular weight compound, there is no necessity to connect the π-conjugated system, and the aromatic compound residue that becomes the π-conjugated system unit is necessary, but they can be arbitrarily selected, and further, they can be substituted at an arbitrary position. Therefore, in low molecular weight compounds, the highest occupied orbital (HOMO), the lowest unoccupied molecular orbital (LUMO), and the triplet (T1) energy level can be intentionally adjusted easily. It is possible to make a blue phosphorescent substance, to use it as a host, and to construct a compound that causes the TADF phenomenon. As described above, the degree of expandability capable of intentionally designing and synthesizing an arbitrary electronic state and an arbitrary level is a factor of the second advantage of the low molecular weight compound.

(Third factor): Ease of compound synthesis Although the reason is similar to the second factor (factor), the low molecular weight compound has no limitation on the molecular structure that can be synthesized as compared with the light emitting polymer (LEP). When the main chain of a light-emitting polymer is π-conjugated, the applicable skeletons and synthesis methods are limited. However, in low molecular weight compounds, new functions are added and physical properties are adjusted (Tg, melting point, solubility, etc.). It is relatively easy to achieve by structure, and this is the third advantage of low molecular weight compounds.

2. Problems in forming an organic functional layer by a wet coating method using a low molecular compound An essential problem in forming an organic functional layer by a wet coating method using a low molecular compound will be described.
Almost all materials used for organic EL elements have to hop and move electrons and holes between molecules inside the organic EL element. Basically, electrons hop through the LUMO level, and holes hop using the HOMO level.
That is, if adjacent molecules do not exist so that π-conjugated systems overlap each other, such carrier conduction does not occur. Therefore, it is advantageous to form a molecular structure with only π-conjugated units as much as possible.
For example, when a plurality of sterically bulky substituents (sec-butyl group, tert-octyl group, triisopropylsilyl group, etc.) are substituted in one molecule in order to improve solubility in a solvent. The π-conjugated system between the molecules becomes difficult to superimpose, and the hopping movement is inhibited at the bulky substituent portion.

On the other hand, since an organic EL element constantly flows during light emission, it is 100% quantum efficient, that is, the probability of carrier recombination is 100%, and thermal deactivation is 0%. Even if it exists, since it is necessary to provide a potential difference between the anode and the cathode in order to keep the carriers flowing, the equivalent circuit of the organic EL element includes a series connection of a diode and a resistor. Become.
That is, it is also known that Joule heat is generated inside the organic EL element that is being energized and light emission, and that heat is actually generated at 100 ° C. or more inside the element, particularly in the light emitting layer where recombination occurs.
In addition, since the organic layer thickness of the entire organic EL element is an extremely thin layer of about 200 nm, heat is conducted between the layers (films), and not only the light emitting layer but all layers continue to be in a high temperature state. become.
When an organic molecule exposed to such a state exceeds its own glass transition point (Tg), it undergoes a phase transition from an amorphous state to a crystalline state.
This crystal grows gradually, and when it exceeds several tens of nm, the thickness of the compound exceeds the thickness, and functional separation by the layer as the organic EL element becomes impossible, resulting in a decrease in luminous efficiency. Will do.

Further, when the crystal exceeds the entire organic layer (100 to 200 nm) of the organic EL element, the anode and the cathode are short-circuited. Then, electric field concentration occurs in the short-circuited portion, and a large current flows in a minute region, so that the organic compound in the portion undergoes thermal decomposition, and a portion that does not emit light, a so-called dark spot is formed.
That is, the low molecular weight compound of the organic EL element is a molecule that does not have a bulky non-aromatic substituent and has a glass transition point (Tg) exceeding 100 ° C. or higher (preferably 150 ° C. or higher). I have to.
In order to construct such a molecule, the π-conjugated system is usually enlarged or the aromatic group is simply linked. However, the compound formed in the usual case has extremely low solubility in a solvent, and coating Even if it cannot be formed into a liquid or can be applied, crystal precipitation or uneven distribution of substances will occur.

As a means to eliminate this dilemma, we have developed an innovative technology that can form a stable amorphous film and maintain it even during energization (for example, Japanese Patent No. 5403179 and Japanese Patent Laid-Open No. 2014). No. 196258, etc.) Specifically, it does not have a bulky and highly flexible branched alkyl group, but connects only aromatic groups to form a via aryl structure, which occurs around the CC bond axis. By actively increasing the number of conformations and geometric isomers due to rotational obstacles, or by allowing multiple molecules (for example, host and dopant) existing in the same layer to interact in various shapes and forms. By increasing the number of components in the film, the entropy in the thin film state is increased and a stable amorphous film is formed. It is possible.

The inventors of the present invention have improved the molecular structure of low molecular weight compounds in accordance with the guidelines described above and optimized the drying conditions in the production of organic EL elements by a wet coating method. A dramatic improvement was achieved, with 95% of the device and 90% emission lifetime. As a result, even for devices using phosphorescent dopants, especially blue phosphorescent dopants, which are said to be the most difficult to improve their lifetime, the basic characteristics of coating film deposition methods are almost comparable to conventional deposition methods. Have found out that
However, many problems still remain in the organic EL element with improved performance.

Examples of such problems include removal of purity of low molecular weight compounds, trace moisture adhering to the surface of the compound, oxygen content of solvent used, water content, and the like.
In addition, for example, even in the case of a low molecular compound generally used in coating, sublimation purification is performed after column chromatography and recrystallization in order to achieve the best performance, and an organic compound is used or In storage, after passing through a vacuum state, it is used after being replaced with a nitrogen atmosphere.
Even when such an organic EL element is produced by a coating method under extremely strict management that eliminates adverse effects as much as possible, it is difficult to exceed the performance of the organic EL element produced by a vapor deposition method. there were.
Furthermore, in the first place, since the low productivity of the vapor deposition method using a vacuum has an adverse effect on the enlargement and mass productivity of the organic EL element, that is, the cost, the coating method is attracting attention. If the method is performed under such strict control, the productivity is lower than the vapor deposition method and the cost is increased.

3. About the purification method of a compound The advantage of a low molecular weight compound is that many purification means can be utilized rather than a high molecular weight compound, and it can be highly purified. However, after all, almost all of the organic compounds constituting the organic EL elements that are currently in practical use are used through purification means called sublimation purification.
Sublimation purification is a classic purification method, but the purification efficiency (theoretical plate number) is overwhelmingly smaller than purification methods such as recrystallization, column chromatography, and HPLC, and virtually no removal of metals or inorganic substances. It is used as a means for removing the solvent.
The reason why the sublimation purification method is employed in organic compounds for organic EL is mainly due to the fact that the manufacturing process of the organic EL element employs a vacuum deposition method. If even a very small amount of solvent is contained in the organic compound, the solvent in the organic compound volatilizes and lowers the degree of vacuum when placed under vacuum in the vapor deposition apparatus.
This makes continuous production impossible and becomes a manufacturing problem. For this reason, a sublimation purification method in which the solvent is completely removed during purification is employed.
Therefore, when the production method of the organic EL element is changed from the vapor deposition method to the coating method, the purification of the organic compound by the sublimation purification method is not essential for the reason described above.

(Recrystallization)
Next, let us consider the most common recrystallization method for purifying low-molecular organic compounds.
This method is a purification method based on the second law of thermodynamics (formula T1).
Formula (T1): −ΔG = −ΔH + TΔS
As the distance between substances decreases, the van der Waals force, hydrogen bond force, π-π interaction force, dipole-dipole interaction force, etc. increase, and the enthalpy (-ΔH) increases.
On the other hand, when the substance is completely dispersed in the medium, that is, when the substance is dissolved, since the substance can move freely, its disorder increases and entropy (ΔS) increases.
In the second law of thermodynamics, all the existence states shift in a direction in which the free energy (−ΔG) of the cast is kept constant or increased.

That is, purifying the compound A to be purified by recrystallization can be rationally explained by considering as follows.
When A is dissolved at a high temperature in a solvent called B which can dissolve A, A exists in a dispersed state. Therefore, the existence distance between A is large and it becomes difficult to interact with each other, so that the enthalpy (−ΔH) becomes extremely small.
On the other hand, since A can freely move around in the solution, entropy (ΔS) is extremely large. When this high temperature solution is cooled, the TΔS applied with the absolute temperature T becomes smaller than before the cooling. At that time, in order to keep the cast free energy (−ΔG) constant before and after cooling, the enthalpy (−ΔH) must be increased.
In other words, as TΔS decreases as the temperature decreases, A must decrease the distance from A to increase the enthalpy. The extreme state is a crystalline state in which the distance between A and A is minimized, and the enthalpy term (−ΔH) increases accordingly.
When the enthalpy increases in this way, the number of components in the system decreases, so the entropy becomes smaller, and the enthalpy is increased by making crystals by that amount.

Thus, the entropy term (TΔS) first decreases with a decrease in temperature, and the enthalpy (−ΔH) increases due to crystallization to compensate for this, and the entropy term further decreases due to the decrease in the number of components. Recrystallization is accomplished by repeating the thermodynamic equilibrium in which ΔS decreases with decreasing ΔS and crystallization occurs accordingly.
However, it is necessary to pay attention to the interaction between the solute A and the solvent B. Since the solute A dissolves by being solvated with the solvent B, A does not dissolve in B unless the interaction between AB is large. However, if the interaction is too large, the distance between A and A cannot be shortened enough to overcome the decrease in the entropy term that decreases due to cooling (because B intervenes between A and A). ), Resulting in no recrystallization.

That is, the purification method by recrystallization can be applied only when the interaction force between AA and the interaction force between AB can be adjusted to the conditions under which recrystallization occurs.
In such a recrystallization purification method, a large amount of purification of several hundred kg or more is possible at a time, and this method has been used for a long time in the chemical industry.

(Column chromatography)
Next, column chromatography (hereinafter also referred to as “chromatography”) will be considered.
The most typical place of column chromatography is to use fine particle silica gel as a stationary phase, adsorb compound A on the silica gel, and gradually elute it with a mobile phase (B) called an eluent.
At this time, when the interaction of the mobile phase (B) antagonizes the interaction (adsorption) between the silica gel surface and the compound A, A is an adsorption-desorption equilibrium between the silica and the mobile phase B. When the interaction with silica is small, elution is early, and when the interaction is large, elution is delayed.
At this time, since the number of theoretical plates (that is, purification efficiency) increases as the number of adsorption-desorption equilibrium reciprocations increases, the purification efficiency by the chromatographic method is proportional to the length of the stationary phase and also to the passing speed of the mobile phase. Proportional to the surface area of the stationary phase.
This is achieved by high-performance liquid chromatography, which is widely used for component analysis and quality assurance of organic compounds. It is a rare technique that can realize a high number of theoretical plates backed by this theory. This is due to the fact that

The reason why this chromatographic method is superior to recrystallization is that the polarity of the mobile phase B can be arbitrarily changed. For example, it is possible to increase the number of theoretical plates by using a gradient method in which the ratio of good solvent is gradually increased during purification as well as making the mobile phase a mixed solvent of good and poor solvents from the beginning.
In addition, since the temperature can be arbitrarily changed, the most important feature is that the applicable range of solutes that can be purified is extremely wide and can be used as a general-purpose purification method.
On the other hand, there are also disadvantages of the chromatographic method. As described above, the fundamental principle for increasing the number of theoretical plates is that the adsorption-desorption equilibrium is utilized.
For example, when the chromatographic method is performed using only the solvent B ′ (that is, a good solvent) having a strong interaction with the compound A as the mobile phase, the interaction between A and the mobile phase B ′ is greater than the interaction between A and the silica gel. If the action is strong, the number of reciprocations of adsorption-desorption equilibrium is drastically reduced and the purification effect is lowered.
That is, in order to enhance the purification effect, it is necessary to mix a large excess of the poor solvent C in addition to the good solvent B ′ to increase the number of reciprocations of adsorption-desorption equilibrium. However, in this case, the solution of the compound A purified and collected contains a large excess of C, and the biggest problem is that it must be concentrated.
For example, in order to obtain 1 g of A, the mixing ratio of the good solvent B ′ and the poor solvent C needs to be about 1:99 to 10:90, and generally the poor solvent C of about 10 L to 100 L is required. It becomes necessary. Therefore, although HPLC fractionation is applied to research and development, it is not used for mass production.

A means for solving the problem of poor solvent concentration is HPLC using supercritical carbon dioxide. Supercritical carbon dioxide is carbon dioxide converted to a supercritical fluid at high temperature and high pressure, and other substances can be made into such a supercritical fluid. Therefore, carbon dioxide is exclusively used for chromatography and extraction.
This supercritical carbon dioxide has different characteristics from ordinary fluids and liquids. That is, by changing the temperature and pressure, the polarity can be continuously changed in accordance with the polarity of the one to be dissolved.
For example, this supercritical carbon dioxide is used to selectively extract docosahexaenoic acid contained in fish heads, and sebum dissolves and adheres to cleaning special clothing that uses adhesives. The agent is achieved by making supercritical carbon dioxide, which does not dissolve, under temperature and pressure control.
Although supercritical carbon dioxide can have various polarities as described above, the polarity of supercritical carbon dioxide formed in a region of relatively low temperature and pressure is about cyclohexane or heptane. In the supercritical HPLC currently on the market, this degree of polar supercritical carbon dioxide is produced in the apparatus, mixed with a good solvent, and entered into the column. Purification is performed.
In the HPLC system using supercritical carbon dioxide, it enters the detector after passing through the column, but normally, the high temperature and high pressure state is maintained until that stage, and carbon dioxide also exists as a supercritical fluid. Thereafter, carbon dioxide becomes a gas until it is separated at room temperature and normal pressure, and it escapes itself from the solution at the time of separation. Therefore, it is not necessary to concentrate the poor solvent. At this time, it is possible to recover carbon dioxide by a carbon dioxide recovery device equipped with a gas-liquid separation mechanism or the like described in the reference literature (Volume 88, No. 10, pp. 525-528, 2010). Again, it can be used as a supercritical fluid.

Therefore, in the drug discovery industry that needs to synthesize a large number of high-purity new synthetic compounds, this supercritical HPLC has recently been actively used. Sales prices have fallen and have become quite popular.
From such characteristics and background, we have utilized this supercritical HPLC for the purification of materials for organic EL devices that require high purity (Japanese Patent No. 4389494).
As mentioned above, there are various purification methods for low-molecular-weight organic compounds amid the desire to improve the productivity of the organic EL industry, but all have advantages and disadvantages, the characteristics of the manufactured compounds, and the purity required for the compounds. Depending on the availability of the remaining solvent, an appropriate purification method is selected and used in combination.

4). About dissolution of organic EL compound First, what is dissolution? Normally, the solvent molecule B is surrounded by the interaction force between A and B by solvating the solute A, and the aggregate of A is separated so that B exists around A, that is, A is made into an isolated single molecule state. That said, it's hard to see if it really is.
For example, when A is a molecule having extremely low solubility or high crystallinity, it can be easily detected by light scattering or the like that it is not dissolved if it is a crystal having a size equal to or larger than the wavelength of visible light. However, for example, in the case of a substance having a low solubility halfway, even if the solvent molecule B surrounds the microcrystal consisting of several molecules of A, it appears to be dissolved. In an organic EL element, this may cause a big problem later.
In other words, in vapor deposition, when forming thin layers (films) such as a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer, the compounds constituting each layer are basically formed by vacuum deposition. It lands on a substrate or an organic layer in the state of vaporized isolated single molecule, which is formed into a solid thin film. Therefore, a film is basically formed by a random assembly of single molecules, and an ideal amorphous film is obtained.

On the other hand, in the case of the coating film forming method, if the coating solution is a dispersion of fine crystals of organic EL compound, it looks like it is completely dissolved, but the actual state of the resulting thin film is The thin film is a collection of microcrystals. Therefore, for example, the level of HOMO or LUMO is not that of a single molecule, but that of a stacked aggregate (microcrystalline state), which may cause a decrease in performance.
In addition, over time, the microcrystals become nuclei and grow into coarse crystals, which not only makes it impossible to separate the functions between layers, but if the crystals become large crystals that short-circuit the anode and cathode, There is a big problem of generating spots.
With regard to coating film-forming elements using low molecules, from the above-mentioned studies over the years, how to approximate the coating liquid in the initial state to a monomolecular dispersion state is the first step to achieve the same performance as the vapor deposition method. It is clear that this is a necessary condition.

Here, the molecular dispersion of the coating solution that is normally intended to be dissolved exactly is determined by small angle X-ray scattering measurement (also referred to as “SAXS”). Consider based on the analysis results.
FIG. 2 shows a particle size distribution curve (horizontal axis: particle size (nm), vertical axis: frequency distribution) of fine particles of a compound constituting a thin film prepared by a vapor deposition method, and a solid line indicates a thin film prepared by a coating method. It is a particle size distribution curve of fine particles of a constituent compound. Since both use the same compound, they can be directly compared.
In the particle size distribution width of the fine particles of the compound in the vapor deposition film formation, the particle size at the position corresponding to the maximum peak is about 2 nm, which is close to monodispersion. Since this is the size of one or two molecules, this means that an amorphous film is formed by arranging almost single molecules at random in vapor deposition.
On the other hand, in the particle size distribution of the fine particles of the compound in the coating film formation, the particle size at the position corresponding to the maximum peak is about 4.5 nm, which is wider than the particle size distribution in the vapor deposition film formation.
As mentioned above, since the same compound is used for vapor deposition and coating, the original crystallinity and cohesiveness of the compound are the same, and this difference is due to the molecular dispersion state in the state of the coating liquid, It is presumed that it was a dispersion of 5 to 10 molecules of microcrystals, not a single isolated molecule.
Although this coating solution is a so-called clear solution, we have misunderstood a dispersion of several molecular crystallites, which is found to be analyzed by X-ray, as a dissolved solution.

5). Regarding the purity of the solvent of the organic EL compound The organic EL element has a basic function of a phenomenon in which light is emitted when the light emitting material in an excited state returns to the ground state.
Further, it is necessary to transport electrons and holes through the hopping phenomenon between the electrode and the light emitting layer.
First, regarding an excited state, for example, in the case of an organic EL element doped with a light emitting material having a concentration of 5%, in order to continuously emit light at a luminance of 1000 cd / m ² , simply calculate, One dopant needs to be about 1 billion excitons. At this time, if the exciton reacts with the water molecule only once, it becomes a compound different from the original molecule. In addition, when excitons react with oxygen molecules, some kind of oxidation reaction or oxidative coupling reaction occurs. This is the most typical phenomenon of a chemical change that causes a decrease in the function of the organic EL element.
In addition to the light emitting material, the radical state is almost the same number of times, and the radical anion state and the cation radical state are active species compared to the ground state. Chemical changes that can occur.
That is, water molecules and oxygen molecules should not be present at all in the coating solution, and that is the premise.
However, industrially, a high purity anhydrous solvent is very expensive and difficult to handle. Therefore, in the end, in order to reduce the cost by the coating method, it is important how to use a general-purpose solvent as a consumable agent.

6). Elemental technology according to the present invention [Coating film]
The coating film of the present invention is a coating film composed of at least one kind of organic compound, and is a particle size distribution curve of molecules or aggregates obtained from small angle X-ray scattering measurement (horizontal axis: particle size, vertical axis: frequency distribution). ) Contains at least one maximum peak, and R and r below contain an organic compound satisfying the relationship represented by the following formula (1).
Formula (1): R <= 15r
[In Formula (1), R represents the particle size corresponding to the maximum peak which shows a particle size with the smallest particle size among the maximum peaks of the particle size distribution curve obtained from a small angle X-ray scattering measurement. When the molecular long axis length obtained by density functional theory calculation for the organic compound is 2a (nm) and the molecular short axis length is 2b (nm), the molecular radius of the organic compound r = (A × b) represents ^1/2 . ]

<Measurement of small-angle X-ray scattering>
For the measurement of small-angle X-ray scattering of the coating film of the present invention, for example, a general-purpose device such as a nanoscale X-ray structure evaluation device NANO-Viewer manufactured by Rigaku Corporation may be used, and preferably a high energy accelerator research mechanism Utilizing large synchrotron radiation facilities such as Synchrotron Radiation Research Facility (Photon Factory), SPring-8 (Super Photoring-8 GeV), Saga Prefectural Kyushu Synchrotron Light Research Center (SAGA-LS), Aichi Synchrotron Light Center A small-angle X-ray scattering apparatus can be used. The measurement conditions are shown below.

A sample is put into a capillary for X-ray diffraction sample (manufactured by WJM-Glass / Muller GmbH) to obtain a measurement sample.
Using SPring-8 radiation as X-rays, the sample is irradiated with a wavelength of 0.1 nm.
For measurement, a multi-axis diffractometer manufactured by HUBER is used, the X-ray incident angle θ is fixed at 0.2 °, and the sample is irradiated. I do.

For analysis of the obtained small angle X-ray scattering data, the particle size / hole size analysis software NANO-Solver manufactured by Rigaku Corporation is used.
When X-rays are incident on a substance, a part is scattered by an electron cloud of each atom constituting the X-ray. From a small scattering angle range (1 to 8 ° in the present invention), information at a spatial level of several nanometers to several hundred nanometers can be obtained, and structural evaluation using this is small-angle X-ray scattering.
In the small-angle X-ray scattering profile, the scattering vector q is generally used instead of the scattering angle θ. q is given by the following formula (A1).
Formula (A1): q = (4π / λ) sin θ
In formula (A1), “λ” represents the wavelength of X-rays, and “θ” represents the scattering angle.
The small region of q is called the Guinier region, and the large region is called the Porod region. From the former, larger spatial information, particle dispersion state and long-period structure, from the latter, smaller region information, high It is possible to obtain molecular polymerization state, surface shape of dispersed particles, protein structural analysis, and the like.

When performing particle analysis in small-angle X-ray scattering, a Guinier plot is generally used.
When the particle size distribution is relatively small and the interaction between particles in the matrix is small, the scattering intensity I (q) is expressed by the formula (A2).
Formula (A2): I (q) = I (0) exp (-q 2 * Rg 2/3)
In formula (A2), “I (q)” represents the scattering intensity, and “Rg” represents the radius of inertia.
This equation is called Guinier's law, and when the scattering intensity I (q) is plotted against q ² , the inclination depends on the inertia radius of the scatterer.
Therefore, in the Guinier plot, the area that shows a sharp decrease in the scattering intensity due to the increase in the scattering angle is the small-angle scattering area, and the width of the central peak is almost inversely proportional to the size of the nonuniform density area, that is, the radius of inertia of the primary particles. .
Therefore, if the scattering intensity increase / decrease behavior is applied to, for example, the Funkuchen method, tangent lines are drawn in order from the right end of the Guinier plot, and the inertia radius and the scattering intensity are calculated from the gradient of each tangent line, the primary particles are calculated from the intensity ratio. The relative ratio of the distribution of inertia radii can be obtained.
In the present invention, for the gradient (gradient) of this Guinier plot, the particle diameter / hole diameter analysis software NANO-Solver manufactured by Rigaku Corporation is used, and the hole and particle diameter analysis fitting is performed assuming that the particle geometric shape is a sphere. By performing, the particle size and particle size distribution of the molecule | numerator or aggregate which originate in the organic compound in a coating film were calculated | required.
For details of the X-ray small angle scattering method, reference can be made to, for example, the X-ray diffraction handbook 3rd edition (issued in 2000 by Rigaku Corporation).
The particle size distribution curve according to the present invention is prepared based on the measurement and analysis method of the small-angle X-ray scattering, and the horizontal axis is the axis representing the particle size and the vertical axis is the axis representing the frequency distribution. Is obtained by plotting the measured values of the frequency distribution against and plotting each plot.
Here, “frequency distribution (also simply referred to as“ distribution ”)” refers to the ratio (ie, frequency) of the relative number of particles of a specific particle size to the total number of particles measured (ie, relative to 1 / nm. Value).

(Maximum peak)
The coating film of the present invention has at least one maximum peak in the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of molecules or aggregates obtained from small angle X-ray scattering measurement.
In FIG. 3, an example of the particle size distribution curve about the coating film of this invention is shown. In the particle size distribution curve, R is the particle size at the position corresponding to the maximum peak.
Further, the particle size distribution curve of the coating film of the present invention may have a plurality of maximum peaks, but the particle size R corresponding to the position of the maximum peak indicating the minimum particle size is the above formula (1). If the relationship is satisfied, the effect of the present invention can be obtained.
Moreover, it is preferable that the particle size R represents the particle size corresponding to the maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. When the particle size R corresponding to the position of the maximum peak with the largest frequency distribution satisfies the above formula (1), the degree of dispersion of the particle size in the coating film increases, that is, the homogeneity in the film increases. The effects of the invention can be obtained effectively.

In the present invention, the “maximum peak” in the particle size distribution curve means a peak having a maximum value with a half width of 10 nm or less and a frequency distribution of 0.05 or more. That is, even if it is a peak having a maximum value in the particle size distribution curve, when the half-value width exceeds 10 nm due to variation in the particle size distribution, or when the frequency distribution is less than 0.05, It does not fall under the maximum peak of the present invention.

<Density functional theory calculation>
The molecular radius r of the organic compound obtained by density functional theory calculation according to the present invention will be described.
The molecular radius r in the present invention is calculated by DFT calculation (density functional theory calculation), the long axis length obtained in the optimized structure is 2a (nm), and the short axis length is 2b. When expressed as (nm), the geometric mean value r = (a × b) ^1/2 . For the theoretical calculation of the length of the major axis and the length of the minor axis, specifically, using Gaussian09 (Gaussian, USA), the basis function is 6-31G ^* and the exchange correlation functional is B3LYP. The major axis length and the minor axis length are obtained based on this molecular structure.
When there are a plurality of molecular radii r, the average value (r = Σr _n / n) is r.

The coating film of the present invention more preferably satisfies the following formula (2).
Formula (2): R ≦ 8r
In formula (2), R and r have the same meanings as R and r in formula (1).

In addition, the frequency distribution of the maximum peak satisfying the formula (1) is preferably 0.4 or more, more preferably 0.5 or more, and further preferably 0.6 or more. A large maximum value is considered to indicate that the degree of dispersion of the particle size in the coating film is high, and is preferable because the homogeneity in the coating film is high.

The particle size value of the maximum peak satisfying the formula (1) is preferably 10.0 nm or less, more preferably 6.0 nm or less, and further preferably 4.5 nm or less.
The smaller the maximum peak particle size value, the smaller the number of molecules contained in the aggregate, indicating that they are highly dispersed, and the device characteristics are more uniform.
Further, from the viewpoint of charge transport, the maximum peak particle size is preferably 4.0 nm or more. The reason for this is not clear yet, but is estimated as follows. Since the aggregate has a certain size, the π-π plane of the molecule is close inside the aggregate and the intermolecular distance is close, so that the charge transport rate in the aggregate is improved, It is presumed that between the aggregates, the frequency of inhibition of charge transport at the interface of the aggregates decreases because the bonding area between the aggregates increases.

The full width at half maximum of the maximum peak satisfying the formula (1) is preferably in the range of 0.3 to 3.0 nm, more preferably in the range of 0.5 to 2.0 nm, More preferably, it is in the range of ˜1.5 nm. The narrower the half-value width, the more the number of molecules contained in the aggregate is shown, and the device characteristics are more uniform, which is preferable.

The coating film of the present invention is a film formed by solidifying a coating solution containing an organic compound in which R ′ and r below satisfy the relationship represented by the following formula (3). It is preferable in that it can be in a non-existing state and can be a coating film having a smaller particle size.
Formula (3): R ′ ≦ 6r
In formula (3), R ′ represents the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. . r is synonymous with r in the formula (1).
The small-angle X-ray scattering of the coating solution can be measured in the same manner as the small-angle X-ray scattering of the coating film described above.
A means for obtaining a coating solution containing an organic compound satisfying the above formula (3) will be described in a coating film manufacturing method (coating solution preparation step) described later.

<Organic compounds>
The coating film of the present invention may be a coating film containing only one type of organic compound satisfying the relationship represented by the above formula (1) of the present invention, or may be a coating film containing a plurality of types of organic compounds. May be.
In the coating film containing a plurality of types of organic compounds, it is sufficient that at least one type of organic compound satisfies the relationship represented by the above formula (1) of the present invention. It is preferable that the relationship represented by the above formula (1) is satisfied, and it is more preferable that all kinds of organic compounds contained in the coating film satisfy the relationship represented by the above formula (1) of the present invention. preferable.

In the case of a coating film containing a plurality of types of organic compounds, the more the solute components are, the more stable it is. That is, the plurality of components of the solute include, for example, the organic compound according to the present invention and at least one other organic compound other than the organic compound when considered thermodynamically as described in JP-A-2009-505154. Are mixed Gibbs energy (ΔG _mix ), which is a value obtained by subtracting the Gibbs energy before mixing from the Gibbs energy after mixing, can be expressed as the following formula (A3).
Formula (A3): ΔG _mix = RTΣ (X _n ln (X _n ))
In the above formula (A3), R represents a gas constant. T represents an absolute temperature. _Xn represents a ratio in all components.
Here, since ΣX _n = 1, 0 <X _n <1, and ln (X _n ) <0, ΔG _mix <0. Therefore, when multiple types of solute are contained, it is thought that the effect that preservability becomes high will be acquired.

The organic compound used in the present invention is not limited to a compound of a specific type and a specific structure, but is preferably a compound used for various electronic devices from the viewpoint of the effect of the present invention.
For example, when the coating film is a coating film for producing an organic EL element, the organic compound is preferably a material for organic electroluminescence (hereinafter also referred to as “organic EL material”). The organic EL material refers to an organic compound that can be used for an organic functional layer (also referred to as “organic EL layer” or “organic compound layer”) formed between an anode and a cathode described later. In addition, a light-emitting element composed of an organic functional layer including these anode, cathode, and organic EL material is referred to as an organic EL element. Examples of compounds used as the organic EL material will be described later.
When the coating film is a coating film for producing a photoelectric conversion element, the organic compound is preferably a p-type organic semiconductor material or an n-type organic semiconductor material. Examples of compounds used as these p-type organic semiconductor materials and n-type organic semiconductor materials will be described later.

<Organic solvent>
In this invention, the organic solvent contained in the coating liquid for forming a coating film means the liquid medium which consists of an organic compound which can melt | dissolve or disperse | distribute the said organic compound based on this invention.
The liquid medium for dissolving or dispersing the organic EL device material according to the present invention includes ketones such as methylene chloride, methyl ethyl ketone, cyclohexanone, fatty acid esters such as ethyl acetate, normal propyl acetate, isopropyl acetate, isobutyl acetate, chlorobenzene, di- Halogenated hydrocarbons such as chlorobenzene, 2,2,3,3-tetrafluoro-1-propanol (TFPO), aromatic hydrocarbons such as toluene, xylene, mesitylene, cyclohexylbenzene, cyclohexane, decalin, dodecane, etc. Aliphatic hydrocarbons, n-butanol, s-butanol, t-butanol alcohols, DMF (N, N-dimethylformamide)
), DMSO (Dimethyl sulfoxide), Te tetrahydrofuran (THF), dioxane, methyl butyl ether, organic solvents such as ethers such as propylene glycol monomethyl ether and the like, from the point of suppressing the amount of solvent contained in the device, A solvent having a boiling point in the range of 50 to 180 ° C. is preferred.

In particular, in the present invention, since the interaction force between the organic compound and the organic solvent is suppressed to a certain range or less, and the driving force for drying is entropy-dominated, the solubility of the organic compound is about 0. It is preferable to use an organic solvent in the range of 001 to 5% by mass.
Generally, a solvent with high solubility is used to dissolve the solute, but a solvent with high solubility generally has a high boiling point such as chlorobenzene or glycerin, and a large amount of energy is required to dry the solvent. It is. Furthermore, the high solubility indicates that the interaction with the material that is the solute is large, and the drying load is further increased because the interaction force between the solute and the solvent is large even during drying. Also, when considering the drying process, the solvent is not removed unless the interaction between the solute and the solute overcomes the interaction between the solute and the solvent, and the enthalpy is inevitably dried with a strong intermolecular interaction enthalpy. Will be. As a result, in the coating film after drying, the intermolecular interaction force is very strong, tends to be a film having a large particle size, and aggregates are observed when the intermolecular interaction force is remarkable. Often. Therefore, by setting the solubility of the organic compound within the range of 0.001 to 5% by mass, the interaction force between the organic compound and the organic solvent can be kept below a certain range, and the driving force for drying is controlled by entropy. And a coating film containing an organic compound satisfying the above formula (1) of the present invention can be obtained.
As such an organic solvent, among the organic solvents described above, an ester solvent, an ether solvent, or the like is preferably used.

[Method for producing coating film]
As described above, the coating film of the present invention is formed by a coating method, and the particle diameter in the film is reduced, and the particle diameter in the film is reduced. As a method, it is important to disperse molecules in a solution state before film formation.
That is, the method for producing a coating film of the present invention includes a step of preparing a coating solution containing an organic compound in which R ′ and r below satisfy the relationship represented by the following formula (3), and drying and solidifying the coating solution. And a step of performing.
Formula (3): R ′ ≦ 6r
In formula (3), R ′ represents the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. . r is synonymous with r in the formula (1).
In addition, the measurement of the small angle X-ray scattering of a coating liquid can be performed about a coating liquid similarly to the X-ray small nucleus scattering measurement of the coating film mentioned above.

<Coating solution preparation process>
A coating liquid preparation process is a process of obtaining the coating liquid containing the organic compound which satisfy | fills said Formula (3). Specifically, it is preferable to disperse a mixed solution of an organic compound and an organic solvent.
The organic compound described above can be used as the organic compound, and the organic solvent described above can be used as the organic solvent.
Examples of the method for dispersing the organic compound in the solution include chromatography, ultrasonic or microwave irradiation, electrophoresis, and the like.
Examples of the chromatography include column chromatography, high performance liquid chromatography, supercritical or subcritical chromatography, gel permeation chromatography and the like, and supercritical or subcritical chromatography is particularly preferable.

<Supercritical or subcritical chromatography method>
The coating film of the present invention is preferably produced using a coating solution obtained by mixing the organic compound and the organic solvent using a supercritical or subcritical chromatography method.
In the supercritical or subcritical chromatography method, a packed column, an open column, or a capillary column can be used.

(Chromatography column)
The column is not particularly limited as long as it has a separating agent capable of separating a target substance in a sample injected into a mobile phase.
The separating agent is selected from various separating agents according to the target substance. The form of the separating agent is not particularly limited. For example, the column may be packed in a state of being supported on a particulate carrier, or may be stored in the column in a state of being supported on an integrated carrier accommodated in the column, or separated. It may be accommodated in the column as an integral molded product made of an agent.

In the method using a packed column, as shown in FIG. 4, a supercritical fluid 11 containing an organic solvent (including carbon dioxide), a pump 12, a modifier 13 if necessary, and an injector for injecting an organic compound to be separated 14, and a separation column 15, and if necessary, a detector 17 and a pressure regulating valve 18 can be used. The temperature of the column 15 is adjusted in the column oven 16. The filler can be appropriately selected from silica used in conventional chromatography methods or surface-modified silica.

In the present invention, the supercritical fluid is a substance in a supercritical state.
Here, the supercritical state will be described. Substances change between three states of gas, liquid, and solid due to changes in environmental conditions such as temperature, pressure (or volume), and this is determined by the balance between intermolecular force and kinetic energy. A phase diagram (phase diagram) shows the transition of the gas-liquid solid state with temperature on the horizontal axis and pressure on the vertical axis. The three phases of gas, liquid, and solid coexist in this state. The point at is called the triple point. When the temperature is higher than the triple point, the liquid and its vapor are in equilibrium. The pressure at this time is a saturated vapor pressure and is represented by an evaporation curve (vapor pressure line). At a pressure lower than the pressure represented by this curve, all the liquid is vaporized, and when a pressure higher than this is applied, all the vapor is liquefied. Even if the pressure is kept constant and the temperature is changed, if this curve is exceeded, the liquid becomes vapor and the vapor becomes liquid. This evaporation curve has an end point on the high temperature and high pressure side, which is called a critical point. The critical point is an important point that characterizes a substance, and the interface between gas and liquid disappears in a state where it is impossible to distinguish between liquid and vapor.
When the temperature is higher than the critical point, the transition between the liquid and the gas can be performed without causing a gas-liquid coexistence state.

A fluid that is above the critical temperature and above the critical pressure is called a supercritical fluid, and the temperature / pressure region that gives the supercritical fluid is called the supercritical region. Further, a state satisfying either the critical temperature or higher or the critical pressure or higher is referred to as a subcritical (expanded liquid) state, and a fluid in the subcritical state is referred to as a subcritical fluid. Supercritical fluids and subcritical fluids can be understood as high-density fluids having high kinetic energy, and exhibit liquid behavior in terms of dissolving solutes and gaseous characteristics in terms of density variability. Although there are many solvent properties of supercritical and subcritical fluids, it is important to have low viscosity, high diffusibility, and excellent permeability to solid materials.

For example, if the supercritical state is carbon dioxide, the critical temperature (hereinafter also referred to as Tc) is 31 ° C., the critical pressure (hereinafter also referred to as Pc) is 7.38 × 10 ⁶ Pa, and propane (Tc = 96.7). C, Pc = 43.4 × 10 ⁵ Pa), ethylene (Tc = 9.9 ° C., Pc = 52.2 × 10 ⁵ Pa), etc. Above this region, the fluid has a large diffusion coefficient and low viscosity. Since movement and concentration equilibrium are reached quickly and the density is high like a liquid, efficient separation becomes possible. In addition, recovery is quickened by using a substance that becomes a gas at normal pressure and room temperature, such as carbon dioxide. In addition, there are no various obstacles resulting from residual trace amounts of solvent that are inevitable in the purification method using a liquid solvent.

As the solvent used as the supercritical fluid or subcritical fluid, carbon dioxide, dinitrogen monoxide, ammonia, water, methanol, ethanol, 2-propanol, ethane, propane, butane, hexane, pentane and the like are preferably used. Among these, carbon dioxide can be preferably used.
A solvent used as a supercritical fluid or subcritical fluid can be used alone, or a so-called modifier (entrainer) for adjusting the polarity can be added.

Examples of modifiers include hydrocarbon solvents such as hexane, cyclohexane, benzene, and toluene, halogenated hydrocarbon solvents such as methyl chloride, dichloromethane, dichloroethane, and chlorobenzene, and alcohol solvents such as methanol, ethanol, propanol, and butanol. Ether solvents such as diethyl ether and tetrahydrofuran (THF), acetal solvents such as acetaldehyde diethyl acetal, ketone solvents such as acetone and methyl ethyl ketone, ester solvents such as ethyl acetate and butyl acetate, formic acid, acetic acid and trifluoroacetic acid Carboxylic acid solvents such as acetonitrile, pyridine, nitrogen compound solvents such as N, N-dimethylformamide, sulfur compound solvents such as carbon disulfide and dimethyl sulfoxide, water, nitric acid, sulfuric acid And the like.

The use temperature of the supercritical fluid or subcritical fluid is basically not particularly limited as long as it is higher than the temperature at which the organic compound according to the present invention is dissolved, but if the temperature is too low, the supercritical fluid or subcritical fluid of the organic compound is used. The solubility in the fluid may be poor, and if the temperature is too high, the organic compound may be decomposed. Therefore, the operating temperature range is preferably 20 to 600 ° C.

The working pressure of the supercritical fluid or subcritical fluid is basically not limited as long as it is higher than the critical pressure of the substance to be used, but if the pressure is too low, the solubility of the organic compound in the supercritical fluid or subcritical fluid If the pressure is too high, problems may occur in terms of durability of the manufacturing apparatus, safety during operation, etc., so the working pressure should be in the range of 1 to 100 MPa. preferable.

A device using a supercritical fluid or subcritical fluid is limited as long as it has a function of dissolving an organic compound in contact with the supercritical fluid or subcritical fluid into the supercritical fluid or subcritical fluid. For example, a batch method using a supercritical fluid or a subcritical fluid in a closed system, a distribution method using a supercritical fluid or a subcritical fluid circulated, a combined method combining a batch method and a distribution method, etc. Can be used.

In the supercritical or subcritical chromatography method according to the present invention, after injecting a sample into the mobile phase, before the tailing of the peak of the target substance with the slowest elution from the column ends, the following is finished. It is preferable to perform sample injection.
At this time, after injecting the sample into the mobile phase, the composition of the mobile phase may be changed, or the composition may be constant. In particular, when performing a fractionation operation of a large amount of the separation target compound, it is preferable to change the composition of the mobile phase.

The step of changing the composition of the mobile phase is to change the composition of the mobile phase containing the supercritical fluid or subcritical fluid and the solvent. By changing the composition of the mobile phase in this step, the peak tailing decay can be accelerated. In column-adsorbed supercritical fluid or subcritical chromatography, the peak shows significant tailing particularly when a preparative operation for loading a relatively large amount of a compound to be separated is performed. If the next sample is injected before this tailing decays, the tailing component will be mixed into the peak component of the next injected sample, resulting in a decrease in the purity of the separated compound and inconvenience. Therefore, it is necessary to wait for complete tailing attenuation before the next sample is injected. Therefore, the timing of the next sample injection can be accelerated by increasing the decay of tailing. However, in the present invention, the composition of the mobile phase is changed to promote the extrusion of the peak component from the column and the tailing. Can be accelerated.

Changing the composition in the mobile phase produces the same effect as the step gradient method in liquid chromatography, and accelerates the extrusion of the peak component from the column, thereby accelerating the tailing decay.
Supercritical fluid or subcritical chromatography uses a highly diffusive, low viscosity supercritical fluid or subcritical fluid, so the mobile phase has a high flow rate and the column equilibrates quickly. Therefore, even if the composition in the mobile phase changes temporarily, if the composition in the mobile phase is restored, the column will quickly return to the environment before the change. Can be injected. As a result, the amount of sample processed per hour can be increased, and the efficiency and productivity are improved.

The step of changing the composition of the mobile phase of the present invention may be performed by any technique as long as it can be performed by a supercritical or subcritical chromatography apparatus. For example, increasing the solvent ratio in the mobile phase can cause changes in the composition of the mobile phase, and significantly changing the pressure and column temperature can also change the CO ₂ density in the mobile phase. Including these, the composition of the mobile phase is changed.

Although the mobile phase already contains a solvent, a solvent injection device is installed upstream of the column and downstream of the mobile phase generator to increase the solvent ratio in the mobile phase. Can be made. The solvent injection device can be, for example, a solvent injection device including a loop pipe for holding a solvent to be injected, a flow path switching valve, and a solvent injection pump.

The loop piping used for the solvent injection device is a tube having a predetermined volume. It is preferable to have a loop pipe because the quantitativeness of sample injection is improved and a larger amount of sample can be injected. In the present invention, the volume of the loop pipe varies depending on conditions such as the type of column used in the supercritical fluid or subcritical chromatography apparatus, the inner diameter of the column, the type of the target substance, the composition of the mobile phase, etc. Therefore, it is necessary to inject a large amount of solvent into the loop piping of the solvent injection device, which is larger than the loop piping of the sample injection device and can hold a large amount of solvent.

The flow path switching valve used in the solvent injection device is not particularly limited as long as it is an openable / closable valve or cock provided in the mobile phase flow path. For example, a two-way valve or a butterfly valve may be used in combination, or a valve that switches the flow path of the mobile phase using a three-way valve may be used. As the solvent injection pump used for the solvent injection device, a high-pressure pump used for sample injection of a supercritical or subcritical chromatography device can be used.

When the solvent injection device is used, the solvent is injected by switching the flow path switching valve and sending the solvent to the mobile phase of the column by the solvent injection pump. It is preferable that the solvent is injected instantaneously with a solvent larger than the injection volume of the sample, preferably 2 times or more, more preferably 5 times or more. As the upper limit value, it is preferable to inject a solvent of 30 times or less, preferably 20 times or less, more preferably 15 times or less the injection volume of the sample. By using such a solvent injection amount, the peak tailing decay is further accelerated.

The solvent injected from the solvent injection device is not particularly limited, and may be, for example, the same solvent as that contained in the mobile phase or a different solvent. Moreover, 1 type may be sufficient as the solvent inject | poured and 2 or more types may be sufficient as it.
In particular, a highly polar solvent is preferable in that the attenuation of tailing is further accelerated. Moreover, it is preferable to use a more polar solvent compared to the solvent contained in the mobile phase.

Both the step of changing the composition of the mobile phase and the step of returning the composition of the mobile phase to before the change are preferably performed instantaneously. The instantaneous here may be a time sufficient to cause the change of the mobile phase.

The method of peak detection is not particularly limited, but the timing can usually be measured by a peak detected by a detector, such as an ultraviolet absorption spectrometer, included in a supercritical fluid or subcritical chromatography.

<Drying solidification process>
The drying and solidifying step is a step of applying and drying and solidifying the coating liquid obtained in the coating liquid preparation step.
Examples of the coating method (coating film forming method) for the coating liquid include spin coating, casting, inkjet, spraying, printing, and slot coater methods. From the standpoint that a homogeneous film is easily obtained and pinholes are less likely to be generated, a coating method such as an ink jet method, a spray method, a printing method, a slot type coater method, or the like is preferable. The method is preferably used.

<Inkjet method>
The ink jet head used in the ink jet method may be an on-demand method or a continuous method. Discharge methods include electro-mechanical conversion methods (eg, single cavity type, double cavity type, bender type, piston type, shear mode type, shared wall type, etc.), and electro-thermal conversion methods (eg, thermal Specific examples include an ink jet type, a bubble jet (registered trademark) type, an electrostatic suction type (for example, an electric field control type, a slit jet type, etc.), and a discharge type (for example, a spark jet type). However, any discharge method may be used. As a printing method, a serial head method, a line head method, or the like can be used without limitation.

The volume of ink droplets ejected from the head is preferably in the range of 0.5 to 100 pL. A range of 2 to 20 pL is more preferable from the viewpoint of reducing coating unevenness and increasing the printing speed. The volume of the ink droplet can be adjusted as appropriate by adjusting the applied voltage.

The printing resolution is preferably in the range of 180 to 10000 dpi (dots per inch), more preferably in the range of 360 to 2880 dpi, and can be appropriately set in consideration of the wet film thickness and the volume of the ink droplets.

In the present invention, the wet film thickness of the wet coating film at the time of inkjet application (immediately after application) can be appropriately set, but is preferably in the range of 1 to 100 μm, more preferably in the range of 1 to 30 μm, and most preferably 1. In the range of ˜5 μm, the effect of the present invention is more remarkable. The wet film thickness can be calculated from the application area, printing resolution, and ink droplet volume.

Ink jet printing methods include a one-pass printing method and a multi-pass printing method.
The one-pass printing method is a method for printing a predetermined printing area by one head scan. On the other hand, the multi-pass printing method is a method of printing a predetermined print area by a plurality of head scans.
In the one-pass printing method, it is preferable to use a wide head in which nozzles are arranged in parallel over a width equal to or larger than the width of a desired coating pattern. When forming a plurality of independent coating patterns whose patterns are not continuous with each other on the same base material, a wide head having at least the width of each coating pattern may be used.

In the drying and solidifying step, the interaction force between the solute (organic compound) and the solvent (organic solvent) is suppressed to a certain range or less, and the driving force for drying is entropy-dominated. It is preferable to use an organic solvent in the range of 0.001 to 5% by mass at normal temperature (25 ° C.).

[Organic EL device]
The organic EL device of the present invention is characterized by having the coating film in at least one organic functional layer.
As described later, examples of the organic functional layer include a plurality of organic functional layers such as an electron injection layer, an electron transport layer, a hole blocking layer, a light emitting layer, an electron blocking layer, a hole transport layer, and a hole injection layer. The coating film of the present invention may be used for at least one of these organic functional layers, and is not particularly limited. Among these organic functional layers, an electron transport layer, a hole blocking layer, a light emitting layer, an electron blocking layer It is preferably either a layer or a hole transport layer, and more preferably one or more of a hole blocking layer, a light emitting layer, and an electron blocking layer. In particular, the light emitting layer is preferable from the viewpoints of light emission efficiency and durability.

Details of the organic EL element will be described below.
The organic EL device of the present invention has an anode and a cathode and one or more organic functional layers (also referred to as “organic EL layer” or “organic compound layer”) sandwiched between these electrodes on a substrate. is doing.

(substrate)
There are no particular limitations on the substrate that can be used in the organic EL device of the present invention (hereinafter also referred to as a substrate, a support substrate, a substrate, a support, etc.), and a glass substrate, a plastic substrate, and the like can be used. It may be transparent or opaque. When extracting light from the substrate side, the substrate is preferably transparent. Examples of the transparent substrate preferably used include glass, quartz, and a transparent plastic substrate.

In order to prevent oxygen and water from entering from the substrate side, the substrate has a thickness of 1 μm or more and a water vapor transmission rate of 1 g / (m ² · 24 h · atm in a test based on JIS Z-0208. ) (25 ° C.) or less is preferred.

Specific examples of the glass substrate include alkali-free glass, low alkali glass, and soda lime glass. Alkali-free glass is preferable from the viewpoint of low moisture adsorption, but any of these may be used as long as it is sufficiently dried.

In recent years, plastic substrates have been attracting attention for reasons such as high flexibility, light weight and resistance to cracking, and further reduction in thickness of organic EL elements.
The resin film used as the base material of the plastic substrate is not particularly limited. For example, polyester such as polyethylene terephthalate (PET) and polyethylene naphthalate (PEN), polyethylene, polypropylene, cellophane, cellulose diacetate, cellulose triacetate (TAC) ), Cellulose acetates such as cellulose acetate butyrate, cellulose acetate propionate (CAP), cellulose acetate phthalate, cellulose nitrate, or derivatives thereof, polyvinylidene chloride, polyvinyl alcohol, polyethylene vinyl alcohol, syndiotactic polystyrene, polycarbonate , Norbornene resin, polymethylpentene, polyetherketone, polyimide, polyethersulfone PES), polyphenylene sulfide, polysulfones, polyetherimides, polyether ketone imide, polyamide, fluorine resin, nylon, polymethyl methacrylate, acrylic or polyarylates, may be mentioned organic-inorganic hybrid resin.

Examples of the organic / inorganic hybrid resin include those obtained by combining an organic resin and an inorganic polymer (for example, silica, alumina, titania, zirconia, etc.) obtained by a sol-gel reaction. Among these, norbornene (or cycloolefin-based) resins such as Arton (manufactured by JSR) or Apel (manufactured by Mitsui Chemicals) are particularly preferable. *

The plastic substrate that is normally produced has a relatively high moisture permeability and may contain moisture inside the substrate. Therefore, when using such a plastic substrate, it is preferable to provide a film (hereinafter referred to as “barrier film” or “water vapor sealing film”) that suppresses intrusion of water vapor, oxygen, or the like on the resin film.

The material constituting the barrier film is not particularly limited, and an inorganic film, an organic film, a hybrid of both, or the like is used. A film may be formed, and the water vapor transmission rate (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) measured by a method according to JIS K 7129-1992 is 0.01 g / ( m ² · 24 h) or less, and the oxygen permeability measured by a method according to JIS K 7126-1987 is preferably 1 × 10 ⁻³ mL / (m ² · 24 h · atm), and a water vapor permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

The material constituting the barrier film is not particularly limited as long as it has a function of suppressing the intrusion of elements that cause deterioration of elements such as moisture and oxygen, and examples thereof include metal oxides, metal oxynitrides, and metal nitrides. An inorganic material, an organic material, a hybrid material of both, or the like can be used.
Metal oxide, metal oxynitride or metal nitride includes silicon oxide, titanium oxide, indium oxide, tin oxide, metal oxide such as indium tin oxide (ITO), aluminum oxide, metal nitride such as silicon nitride And metal oxynitrides such as silicon oxynitride and titanium oxynitride.

Furthermore, in order to improve the brittleness of the film, it is more preferable to have a laminated structure of these inorganic layers and layers made of organic materials. Although there is no restriction | limiting in particular about the lamination | stacking order of an inorganic layer and an organic layer, It is preferable to laminate | stack both alternately several times.

The barrier membrane had a water vapor permeability (25 ± 0.5 ° C., relative humidity (90 ± 2)% RH) of 0.01 g / (m ² · 24 h) measured by a method according to JIS K 7129-1992. The following barrier film is preferable, and further, the oxygen permeability measured by a method according to JIS K 7126-1987 is 10 ⁻³ mL / (m ² · 24 h · atm) or less, and the water vapor permeability. However, it is preferable that the film has a high barrier property of 10 ⁻⁵ g / (m ² · 24 h) or less. The method of providing the barrier film on the resin film is not particularly limited, and any method may be used. Vapor deposition method, sputtering method, reactive sputtering method, molecular beam epitaxy method, cluster ion beam method, ion plating method, plasma polymerization method, atmospheric pressure plasma A polymerization method, a CVD method (chemical vapor deposition: for example, a plasma CVD method, a laser CVD method, a thermal CVD method, etc.), a coating method, a sol-gel method, or the like can be used. Of these, the method by plasma CVD treatment at or near atmospheric pressure is preferable from the viewpoint that a dense film can be formed.

Examples of the opaque substrate include metal plates such as aluminum and stainless steel, films, opaque resin substrates, ceramic substrates, and the like.

(anode)
As the anode of the organic EL element, a material having a work function (4 eV or more) metal, alloy, metal electrically conductive compound, or a mixture thereof is preferably used.
Here, the “metal conductive compound” refers to a compound of a metal and another substance having electrical conductivity, and specifically, for example, a metal oxide, a halide or the like. That has electrical conductivity.

Specific examples of such an electrode substance include a conductive transparent material such as a metal such as Au, CuI, indium tin oxide (ITO), SnO ₂ , and ZnO. The anode can be produced by forming a thin film made of these electrode materials on the substrate by a known method such as vapor deposition or sputtering.
In addition, a pattern having a desired shape may be formed on the thin film by a photolithography method, and when the pattern accuracy is not so high (about 100 μm or more), a desired shape can be formed at the time of vapor deposition or sputtering of the electrode material. A pattern may be formed through a mask.
When light emission is extracted from the anode, it is desirable that the transmittance be greater than 10%. The sheet resistance as the anode is several hundred Ω / sq. The following is preferred. Further, although the film thickness of the anode depends on the material constituting it, it is usually selected in the range of 10 nm to 1 μm, preferably 10 to 200 nm.

(Organic functional layer)
The organic functional layer (also referred to as “organic EL layer” or “organic compound layer”) includes at least a light-emitting layer. In a broad sense, the light-emitting layer is a current flowing through an electrode composed of a cathode and an anode. Specifically, it refers to a layer containing an organic compound that emits light when an electric current is passed through an electrode composed of a cathode and an anode.

The organic EL device used in the present invention may have a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer in addition to the light emitting layer as necessary, and these layers are cathodes. And the anode.
In particular,
(I) Anode / light emitting layer / cathode (ii) Anode / hole injection layer / light emitting layer / cathode (iii) Anode / light emitting layer / electron injection layer / cathode (iv) Anode / hole injection layer / light emitting layer / electron Injection layer / cathode (v) anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode (vi) anode / hole transport layer / light emitting layer / electron transport layer / cathode etc. Structure.
Further, a cathode buffer layer (for example, lithium fluoride) may be inserted between the electron injection layer and the cathode, and an anode buffer layer (for example, copper phthalocyanine) may be inserted between the anode and the hole injection layer. ) May be inserted.

(Light emitting layer)
The light emitting layer according to the present invention is a layer that emits light by recombination of electrons and holes injected from the electrode, the electron transport layer, or the hole transport layer, and the light emitting portion is in the layer of the light emitting layer. May be the interface between the light emitting layer and the adjacent layer. The light emitting layer may be a layer having a single composition, or may be a laminated structure including a plurality of layers having the same or different compositions.
The light emitting layer itself may be provided with functions such as a hole injection layer, an electron injection layer, a hole transport layer, and an electron transport layer. That is, (1) an injection function capable of injecting holes from an anode or a hole injection layer and applying electrons from a cathode or an electron injection layer when an electric field is applied to the light emitting layer, and (2) injection At least one of a transport function that moves electric charges (electrons and holes) by the force of an electric field, and (3) a light-emitting function that provides a recombination field of electrons and holes inside the light-emitting layer and connects it to light emission. A function may be added. Note that the light emitting layer may have a difference in the ease of hole injection and the ease of electron injection, and the transport function represented by the mobility of holes and electrons may be large or small. The one having a function of moving at least one of the charges is preferable.

The type of the light emitting material used for the light emitting layer is not particularly limited, and conventionally known light emitting materials for organic EL elements can be used. Such a light-emitting material is mainly an organic compound, and has a desired color tone, for example, Macromol. Symp. 125, pages 17 to 26, and the like. The light emitting material may be a polymer material such as p-polyphenylene vinylene or polyfluorene, and a polymer material in which the light emitting material is introduced into a side chain or a polymer material having the light emitting material as a main chain of the polymer. May be used. Note that, as described above, since the light emitting material may have a hole injection function and an electron injection function in addition to the light emission performance, most of the hole injection material and the electron injection material described later may be used as the light emitting material. Can be used.

In a layer constituting an organic EL element, when the layer is composed of two or more organic compounds, the main component is called a host, the other components are called dopants, and the host and dopant are used in combination in the light emitting layer of the present invention. The mixing ratio of the light-emitting layer dopant (hereinafter also referred to as light-emitting dopant) to the host compound as the main component is preferably 0.1 to less than 30% by mass.

The dopant used in the light emitting layer is roughly classified into two types, that is, a fluorescent dopant that emits fluorescence and a phosphorescent dopant that emits phosphorescence.
Representative examples of fluorescent dopants include coumarin dyes, pyran dyes, cyanine dyes, croconium dyes, squalium dyes, oxobenzanthracene dyes, fluorescein dyes, rhodamine dyes, pyrylium dyes, perylene dyes. Stilbene dyes, polythiophene dyes, rare earth complex phosphors, and other known fluorescent compounds.
In the present invention, it is preferable that at least one light emitting layer contains a phosphorescent compound.

In the present invention, a phosphorescent compound is a compound in which light emission from an excited triplet is observed, and is a compound having a phosphorescence quantum yield of 0.001 or more at 25 ° C.
The phosphorescence quantum yield is preferably 0.01 or more, more preferably 0.1 or more. The phosphorescence quantum yield can be measured by the method described in Spectroscopic II, page 398 (1992 edition, Maruzen) of Experimental Chemistry Course 4 of the 4th edition. Although the phosphorescence quantum yield in a solution can be measured using various solvents, the phosphorescence quantum yield used in the present invention only needs to achieve the above phosphorescence quantum yield in any solvent.

The phosphorescent dopant is a phosphorescent compound, and a typical example thereof is preferably a complex compound containing a group 8-10 metal in the periodic table of elements, more preferably an iridium compound or an osmium compound. , Rhodium compounds, palladium compounds, or platinum compounds (platinum complex compounds). Among them, iridium compounds, rhodium compounds, and platinum compounds are preferable, and iridium compounds are most preferable.

Examples of dopants are compounds described in the following documents or patent publications. J. et al. Am. Chem. Soc. 123, 4304-4312, International Publication Nos. 2000/70655, 2001/93642, 2002/02714, 2002/15645, 2002/44189, 2002/081488, JP 2002-280178. Gazette, 2001-181616, 2002-280179, 2002-181617, 2002-280180, 2001-247859, 2002-299060, 2001-313178 Gazette, 2002-302671, 2001-345183, 2002-324679, 2002-332291, 2002-50484, 2002-332292, 2002-83684 Publication, JP 2002-540572, JP 2002-117978, 2002-338588, 2002-170684, 2002-352960, 2002-50483, 2002-1000047 Gazette, 2002-173684 gazette, 2002-359082 gazette, 2002-17584 gazette, 2002-363552 gazette, 2002-184582 gazette, 2003-7469 gazette, special table 2002-525808. Publication, JP 2003-7471 A, JP 2002-525833 A, JP 2003-31366 A, 2002-226495, 2002-234894, 2002-2335076, 2002. -241 No. 51, No. 2001-319779, No. 2001-319780, No. 2002-62824, No. 2002-1000047, No. 2002-203679, No. 2002-343572, No. 2002-203678. No. Gazette etc.

Although the specific example of a phosphorescent dopant is given to the following, this invention is not limited to these.

Only one type of light emitting dopant may be used, or a plurality of types of light emitting dopants may be used. By simultaneously extracting light emitted from these dopants, a light emitting element having a plurality of light emission maximum wavelengths can be configured. For example, both a phosphorescent dopant and a fluorescent dopant may be added. When an organic EL element is formed by laminating a plurality of light emitting layers, the light emitting dopants contained in each layer may be the same or different, may be a single type, or may be a plurality of types. .
Furthermore, a polymer material in which the luminescent dopant is introduced into a polymer chain or the luminescent dopant is used as a polymer main chain may be used.

Examples of the host compound include those having a basic skeleton such as a carbazole derivative, a triarylamine derivative, an aromatic borane derivative, a nitrogen-containing heterocyclic compound, a thiophene derivative, a furan derivative, and an oligoarylene compound. Transport materials and hole transport materials are also suitable examples.
When applied to a blue or white light emitting element, a display device, and a lighting device, the host compound preferably has a maximum fluorescence wavelength of 415 nm or less. When a phosphorescent dopant is used, the phosphorescence of the host compound is 0- More preferably, the 0 band is 450 nm or less. As the light-emitting host, a compound having a hole transporting ability and an electron transporting ability, preventing emission light from being increased in wavelength, and having a high Tg (glass transition temperature) is preferable.

As specific examples of the light-emitting host, for example, compounds described in the following documents are suitable.
JP-A-2001-257076, 2002-308855, 2001-313179, 2002-319491, 2001-357777, 2002-334786, 2002-8860, 2002-334787, 2002-15871, 2002-334788, 2002-43056, 2002-334789, 2002-75645, 2002-338579, 2002-105445 gazette, 2002-343568 gazette, 2002-141173 gazette, 2002-352957 gazette, 2002-203683 gazette, 2002-363227 gazette, 2002-231453 gazette, No. 003-3165, No. 2002-234888, No. 2003-27048, No. 2002-255934, No. 2002-260861, No. 2002-280183, No. 2002-299060, No. 2002. -302516, 2002-305083, 2002-305084, 2002-308837, and the like.

The luminescent dopant may be dispersed throughout the layer containing the host compound or may be partially dispersed. A compound having another function may be added to the light emitting layer.

A light emitting layer can be formed by using the above-mentioned materials to form a thin film by a known method such as vapor deposition, spin coating, casting, LB, ink jet transfer, or printing. The light emitting layer formed is particularly preferably a molecular deposited film.
Here, the molecular deposition film refers to a thin film formed by deposition from the gas phase state of the compound or a film formed by solidification from the molten state or liquid phase state of the compound. Usually, this molecular deposited film and a thin film (molecular accumulation film) formed by the LB method can be distinguished from each other by a difference in aggregated structure and higher order structure and a functional difference resulting therefrom.
In this invention, it is preferable to use the phosphorescent dopant and host compound which are said luminescent materials as an organic compound which concerns on this invention. That is, the light emitting layer is formed by applying a solution containing the phosphorescent dopant and the host compound and an organic solvent by spin coating, casting, ink jet, spraying, printing, slot coating, or the like. This is preferable because a light emitting layer made of a molecular deposited film can be formed. Among these, the inkjet method is preferable from the viewpoints that a homogeneous film is easily obtained and pinholes are hardly generated.
In the coating solution containing the phosphorescent dopant, the host compound, and the organic solvent, the dissolved carbon dioxide concentration with respect to the organic solvent under an atmospheric pressure condition of 50 ° C. or less is set to 1 ppm to a saturated concentration with respect to the organic solvent. Is preferred. As a means for setting the dissolved carbon dioxide concentration within the above range, a method of bubbling carbon dioxide gas in a solution containing a phosphorescent dopant and a host compound and an organic solvent, or a supercritical fluid containing an organic solvent and carbon dioxide is used. The supercritical chromatography method used is mentioned.

In the coating solution, it is preferable that at least one of the phosphorescent dopant and the host compound satisfies the relationship represented by the above (3). More preferably, in the coating solution, both the phosphorescent dopant and the host compound satisfy the relationship represented by the above (3). As such means, it is preferable to mix the phosphorescent dopant and the host compound and the organic solvent by using the supercritical chromatography method described above.

(Hole injection layer and hole transport layer)
The hole injection material used for the hole injection layer has either a hole injection property or an electron barrier property. The hole transport material used for the hole transport layer has an electron barrier property and a function of transporting holes to the light emitting layer. Therefore, in the present invention, the hole transport layer is included in the hole injection layer.

These hole injection material and hole transport material may be either organic or inorganic. Specifically, for example, triazole derivatives, oxadiazole derivatives, imidazole derivatives, polyarylalkane derivatives, pyrazoline derivatives, pyrazolone derivatives, phenylenediamine derivatives, arylamine derivatives, amino-substituted chalcone derivatives, oxazole derivatives, styrylanthracene derivatives, fluorenone derivatives , Hydrazone derivatives, stilbene derivatives, silazane derivatives, aniline copolymers, porphyrin compounds, thiophene oligomers and other conductive polymer oligomers. Of these, arylamine derivatives and porphyrin compounds are preferred.
Among the arylamine derivatives, aromatic tertiary amine compounds and styrylamine compounds are preferable, and aromatic tertiary amine compounds are more preferable.

Representative examples of the aromatic tertiary amine compound and styrylamine compound include N, N, N ′, N′-tetraphenyl-4,4′-diaminophenyl; N, N′-diphenyl-N, N ′. -Bis (3-methylphenyl)-[1,1'-biphenyl] -4,4'-diamine (TPD); 2,2-bis (4-di-p-tolylaminophenyl) propane; Bis (4-di-p-tolylaminophenyl) cyclohexane; N, N, N ′, N′-tetra-p-tolyl-4,4′-diaminobiphenyl; 1,1-bis (4-di-p- Tolylaminophenyl) -4-phenylcyclohexane; bis (4-dimethylamino-2-methylphenyl) phenylmethane; bis (4-di-p-tolylaminophenyl) phenylmethane; N, N'-diphenyl-N, '-Di (4-methoxyphenyl) -4,4'-diaminobiphenyl; N, N, N', N'-tetraphenyl-4,4'-diaminodiphenyl ether; 4,4'-bis (diphenylamino) biphenyl N, N, N-tri (p-tolyl) amine; 4- (di-p-tolylamino) -4 '-[4- (di-p-tolylamino) styryl] stilbene; 4-N, N-diphenylamino -(2-diphenylvinyl) benzene; 3-methoxy-4'-N, N-diphenylaminostilbene; N-phenylcarbazole, as well as two fused aromatics described in US Pat. No. 5,061,569 Having a ring in the molecule, for example, 4,4′-bis [N- (1-naphthyl) -N-phenylamino] biphenyl (hereinafter abbreviated as α-NPD), 4,4 ′, 4 ″ -tris [N- (3-methylphenyl) -N-phenylamino] triphenylamine in which triphenylamine units described in Japanese Patent No. 308688 are linked in a three star burst type ( In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material.

In the present invention, the hole transport material of the hole transport layer preferably has a fluorescence maximum wavelength at 415 nm or less. That is, the hole transport material is preferably a compound that has a hole transport ability, prevents the emission of light from becoming longer, and has a high Tg.
For the hole injection layer and the hole transport layer, the above-described hole injection material and hole transport material are known from, for example, a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, a transfer method, and a printing method. This method can be formed by thinning the film.
In the present invention, the hole injection material and the hole transport material are preferably used as the organic compound according to the present invention. A solution containing the hole injecting material and the hole transporting material and an organic solvent can be formed by applying a spin coat method, a cast method, an ink jet method, a spray method, a printing method, a slot coater method, or the like. preferable. Among these, the inkjet method is preferable from the viewpoints that a homogeneous film is easily obtained and pinholes are hardly generated.

The thickness of the hole injection layer and the hole transport layer is not particularly limited, but is usually about 5 nm to 5 μm. The hole injection layer and the hole transport layer may each have a single-layer structure composed of one or more of the above materials, or a laminated structure composed of a plurality of layers having the same composition or different compositions. Also good. Moreover, when providing both a positive hole injection layer and a positive hole transport layer, although a different material is normally used among said materials, you may use the same material.

(Electron injection layer and electron transport layer)
The electron injecting layer only needs to have a function of transmitting electrons injected from the cathode to the light emitting layer, and any material can be selected from conventionally known compounds.
Examples of materials used for this electron injection layer (hereinafter also referred to as electron injection materials) include heterocyclic tetracarboxylic acid anhydrides such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, and carbodiimides. , Fluorenylidenemethane derivatives, anthraquinodimethane and anthrone derivatives, oxadiazole derivatives and the like.
In addition, a series of electron transfer compounds described in Japanese Patent Application Laid-Open No. 59-194393 is disclosed as a material for forming a light emitting layer in the publication, but as a result of investigations by the present inventors, electron injection is performed. It was found that it can be used as a material. Furthermore, in the above oxadiazole derivative, a thiadiazole derivative in which the oxygen atom of the oxadiazole ring is substituted with a sulfur atom, or a quinoxaline derivative having a quinoxaline ring known as an electron-withdrawing group can also be used as an electron injection material.

In addition, metal complexes of 8-quinolinol derivatives such as tris (8-quinolinol) aluminum (abbreviated as Alq ₃ ), tris (5,7-dichloro-8-quinolinol) aluminum, tris (5,7-dibromo-8- Quinolinol) aluminum, tris (2-methyl-8-quinolinol) aluminum, tris (5-methyl-8-quinolinol) aluminum, bis (8-quinolinol) zinc (Znq), etc., and the central metal of these metal complexes is In Metal complexes replaced with Mg, Cu, Ca, Sn, Ga, or Pb can also be used as the electron injection material.

In addition, metal-free or metal phthalocyanine, or those whose terminal is substituted with an alkyl group or a sulfonic acid group can be preferably used as the electron injection material. Similarly to the hole injection layer, an inorganic semiconductor such as n-type-Si or n-type-SiC can also be used as the electron injection material.

It is preferable that the preferable compound used for an electron carrying layer has a fluorescence maximum wavelength in 415 nm or less. That is, the compound used for the electron transport layer is preferably a compound that has an electron transport ability, prevents emission of longer wavelengths, and has a high Tg.
The electron injection layer is formed by thinning the electron injection material by a known method such as a vacuum deposition method, a spin coating method, a casting method, an LB method, an ink jet method, a transfer method, or a printing method. Can do.
In the present invention, the electron injection material is preferably used as the organic compound according to the present invention. And it is preferable to form the solution containing the said electron injection material and an organic solvent by application | coating, such as a spin coat method, the casting method, the inkjet method, the spray method, the printing method, the slot type coater method. Among these, the inkjet method is preferable from the viewpoints that a homogeneous film is easily obtained and pinholes are hardly generated.
The thickness of the electron injection layer is not particularly limited, but is usually selected in the range of 5 nm to 5 μm. The electron injection layer may have a single layer structure composed of one or more of these electron injection materials, or may have a laminated structure composed of a plurality of layers having the same composition or different compositions.

In the present specification, when the ionization energy of the electron injection layer is larger than that of the light emitting layer, it is particularly referred to as an electron transport layer. Therefore, in this specification, an electron carrying layer is contained in an electron injection layer.
The electron transport layer is also referred to as a hole blocking layer (hole blocking layer). Examples thereof include, for example, International Publication No. 2000/70655, JP 2001-313178 A, JP 11-204258 A, and the like. No. 11-204359, and “Organic EL devices and their industrialization front line (issued by NTT, Inc., November 30, 1998)”, page 237, and the like. In particular, in the so-called “phosphorescent light emitting device” using an ortho metal complex dopant in the light emitting layer, it is preferable to adopt a configuration having an electron transport layer (hole blocking layer) as in the above (v) and (vi).

(Buffer layer)
A buffer layer (electrode interface layer) may be present between the anode and the light emitting layer or the hole injection layer, and between the cathode and the light emitting layer or the electron injection layer.
The buffer layer is a layer that is provided between the electrode and the organic layer in order to lower the driving voltage and improve the light emission efficiency. “The organic EL element and the forefront of its industrialization (issued on November 30, 1998 by NTS Corporation) ) ”, Chapter 2, Chapter 2,“ Electrode Materials ”(pages 123 to 166), which includes an anode buffer layer and a cathode buffer layer.

Details of the anode buffer layer are also described in JP-A-9-45479, 9-260062, 8-28869, etc., and specific examples thereof include a phthalocyanine buffer layer represented by copper phthalocyanine, vanadium oxide. And an oxide buffer layer, an amorphous carbon buffer layer, and a polymer buffer layer using a conductive polymer such as polyaniline (emeraldine) or polythiophene.

The details of the cathode buffer layer are described in JP-A-6-325871, JP-A-9-17574, JP-A-10-74586, and the like. Specifically, a metal buffer layer typified by strontium or aluminum, Examples thereof include an alkali metal compound buffer layer typified by lithium fluoride, an alkaline earth metal compound buffer layer typified by magnesium fluoride, and an oxide buffer layer typified by aluminum oxide.

The buffer layer is desirably a very thin film, and depending on the material, the thickness is preferably in the range of 0.1 to 100 nm. Furthermore, in addition to the basic constituent layers, layers having other functions may be appropriately laminated as necessary.

(cathode)
As described above, the cathode of the organic EL element generally uses a metal having a low work function (less than 4 eV) (hereinafter referred to as an electron injecting metal), an alloy, a metal electroconductive compound, or a mixture thereof as an electrode material. Things are used.
Specific examples of such electrode materials include sodium, magnesium, lithium, aluminum, indium, rare earth metals, sodium-potassium alloys, magnesium / copper mixtures, magnesium / silver mixtures, magnesium / aluminum mixtures, magnesium / indium mixtures, aluminum / Aluminum oxide (Al ₂ O ₃ ) mixture, lithium / aluminum mixture and the like.

In the present invention, those listed above may be used as the electrode material of the cathode. However, from the viewpoint of more effectively exerting the effects of the present invention, the cathode may contain a Group 13 metal element. preferable. That is, in the present invention, as described later, the surface of the cathode is oxidized with oxygen gas in a plasma state to form an oxide film on the cathode surface, thereby preventing further oxidation of the cathode and improving the durability of the cathode. Can be made.
Therefore, the electrode material of the cathode is preferably a metal having a preferable electron injection property required for the cathode and capable of forming a dense oxide film.

Specific examples of the electrode material of the cathode containing the Group 13 metal element include, for example, aluminum, indium, a magnesium / aluminum mixture, a magnesium / indium mixture, and an aluminum / aluminum oxide (Al ₂ O ₃ ) mixture. And lithium / aluminum mixtures. In addition, the mixing ratio of each component of the said mixture can employ | adopt a conventionally well-known ratio as a cathode of an organic EL element, However It is not limited to this in particular. The cathode can be produced by forming a thin film on the organic compound layer (organic EL layer) using the electrode material described above by a method such as vapor deposition or sputtering.

Also, the sheet resistance as a cathode is several hundred Ω / sq. The film thickness is usually selected from the range of 10 nm to 1 μm, preferably 50 to 200 nm. In order to transmit the emitted light, it is preferable that either one of the anode and the cathode of the organic EL element is made transparent or semi-transparent because the light emission efficiency is improved.

[Method for producing organic EL element]
As an example of the method for producing the organic EL device of the present invention, a method for producing an organic EL device comprising an anode / hole injection layer / hole transport layer / light emitting layer / electron transport layer / electron injection layer / cathode will be described.
First, a thin film made of a desired electrode material, for example, an anode material is formed on a suitable substrate by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably 10 to 200 nm, thereby producing an anode. To do. Next, an organic compound thin film of a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a hole blocking layer, which are element materials, is formed thereon.
As described above, there are spin coating method, casting method, ink jet method, spray method, vapor deposition method, printing method, slot coating method, etc. as methods for thinning these organic compound thin films, but a homogeneous film can be obtained. In the present invention, the ink jet method is preferable because it is easy to be formed and pinholes are hardly generated, and the coating liquid according to the present invention can be used in the present invention.
Different film formation methods may be applied for each layer. When a vapor deposition method is employed for film formation, the vapor deposition conditions vary depending on the type of compound used, but generally a boat heating temperature of 50 to 450 ° C., a vacuum degree of 10 ⁻⁶ to 10 ⁻² Pa, a vapor deposition rate of 0.01 It is desirable to select appropriately within the range of ˜50 nm / second, substrate temperature of −50 to 300 ° C., and thickness of 0.1 nm to 5 μm.

After these layers are formed, a thin film made of a cathode material is formed thereon by a method such as vapor deposition or sputtering so as to have a thickness of 1 μm or less, preferably in the range of 50 to 200 nm, and a cathode is provided. Thus, a desired organic EL element can be obtained. The organic EL element is preferably manufactured from the hole injection layer to the cathode consistently by a single evacuation, but it may be taken out halfway and subjected to different film forming methods. At that time, it is necessary to consider that the work is performed in a dry inert gas atmosphere.

[Encapsulation of organic EL elements]
The organic EL element sealing means is not particularly limited. For example, after sealing the outer periphery of the organic EL element with a sealing adhesive, a sealing member is provided so as to cover the light emitting region of the organic EL element. The method of arranging is mentioned.

Examples of the sealing adhesive include photocuring and thermosetting adhesives having reactive vinyl groups such as acrylic acid oligomers and methacrylic acid oligomers, and moisture curing adhesives such as 2-cyanoacrylates. Can be mentioned. Moreover, heat | fever and chemical curing types (two-component mixing), such as an epoxy type, can be mentioned. Moreover, hot-melt type polyamide, polyester, and polyolefin can be mentioned. Moreover, a cationic curing type ultraviolet curing epoxy resin adhesive can be mentioned.

As the sealing member, a polymer film and a metal film can be preferably used from the viewpoint of reducing the thickness of the organic EL element.

In the gap between the sealing member and the light emitting region of the organic EL element, in addition to the sealing adhesive, in the gas phase and liquid phase, inert gases such as nitrogen and argon, fluorinated hydrocarbons, and silicon oil are used. Inert liquids can also be injected. Further, the gap between the sealing member and the display area of the organic EL element can be evacuated, or a hygroscopic compound can be sealed in the gap.

[Display device]
The multicolor display device using the organic EL element of the present invention is provided with a shadow mask only at the time of forming a light emitting layer, and the other layers are common, so patterning such as a shadow mask is unnecessary, vapor deposition method, casting method, A film can be formed by a spin coating method, an inkjet method, a printing method, or the like.
When patterning is performed only on the light-emitting layer, the method is not limited, but a vapor deposition method, an inkjet method, and a printing method are preferable. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.
In addition, it is also possible to reverse the production order and produce the cathode, the electron injection layer, the electron transport layer, the light emitting layer, the hole transport layer, the hole injection layer, and the anode in this order.
When a DC voltage is applied to the multicolor display device thus obtained, light emission can be observed by applying a voltage of about 2 to 40 V with the positive polarity of the anode and the negative polarity of the cathode. Further, even when a voltage is applied with the opposite polarity, no current flows and no light emission occurs. Further, when an AC voltage is applied, light is emitted only when the anode is in the + state and the cathode is in the-state. The alternating current waveform to be applied may be arbitrary.

The multicolor display device can be used as a display device, a display, and various light emission sources. In a display device or display, full-color display is possible by using three types of organic EL elements of blue, red, and green light emission.
Examples of the display device and the display include a television, a personal computer, a mobile device, an AV device, a character broadcast display, and an information display in a car. In particular, it may be used as a display device for reproducing still images and moving images, and the driving method when used as a display device for reproducing moving images may be either a simple matrix (passive matrix) method or an active matrix method.

Light sources include home lighting, interior lighting, clock and liquid crystal backlights, billboard advertisements, traffic lights, light sources for optical storage media, light sources for electrophotographic copying machines, light sources for optical communication processors, light sources for optical sensors, etc. For example, but not limited to.
Further, the organic EL element according to the present invention may be used as an organic EL element having a resonator structure.
Examples of the purpose of use of the organic EL element having such a resonator structure include a light source of an optical storage medium, a light source of an electrophotographic copying machine, a light source of an optical communication processing machine, and a light source of an optical sensor. It is not limited. Moreover, you may use for the said use by making a laser oscillation.

The organic EL device of the present invention may be used as a kind of lamp such as an illumination or exposure light source, a projection device that projects an image, or a display device that directly recognizes a still image or a moving image. (Display) may be used. The driving method when used as a display device for moving image reproduction may be either a simple matrix (passive matrix) method or an active matrix method. Alternatively, it is possible to produce a full-color display device by using two or more organic EL elements of the present invention having different emission colors.

An example of a display device composed of the organic EL element of the present invention will be described below with reference to the drawings.
FIG. 5 is a schematic diagram illustrating an example of a display device including organic EL elements.
It is a schematic diagram of a display such as a mobile phone that displays image information by light emission of an organic EL element. The display 41 includes a display unit A having a plurality of pixels, a control unit B that performs image scanning of the display unit A based on image information, and the like. The control unit B is electrically connected to the display unit A, and sends a scanning signal and an image data signal to each of the plurality of pixels based on image information from the outside. The pixels for each scanning line are converted into image data signals by the scanning signal. In response to this, light is sequentially emitted and image scanning is performed to display image information on the display unit A.

FIG. 6 is a schematic diagram of the display unit A. The display unit A includes a wiring unit including a plurality of scanning lines 55 and data lines 56, a plurality of pixels 53, and the like on a substrate. The main members of the display unit A will be described below.
FIG. 6 shows a case where the light emitted from the pixel 53 is extracted in the direction of the white arrow (downward). The scanning lines 55 and the plurality of data lines 56 in the wiring portion are each made of a conductive material, and the scanning lines 55 and the data lines 56 are orthogonal to each other in a lattice shape and are connected to the pixels 53 at the orthogonal positions (details are shown in the figure). Not shown). When a scanning signal is applied from the scanning line 55, the pixel 53 receives an image data signal from the data line 56, and emits light according to the received image data. Full color display is possible by appropriately arranging pixels in the red region, the green region, and the blue region that emit light on the same substrate.

Next, the light emission process of the pixel will be described.
FIG. 7 is a schematic diagram showing a pixel circuit. The pixel includes an organic EL element 60, a switching transistor 61, a driving transistor 62, a capacitor 63, and the like. A full color display can be performed by using red, green, and blue light emitting organic EL elements as the organic EL elements 60 for a plurality of pixels, and juxtaposing them on the same substrate.
In FIG. 7, an image data signal is applied to the drain of the switching transistor 61 from the control unit B (not shown in FIG. 7 but shown in FIG. 5) via the data line 56. When a scanning signal is applied from the control unit B to the gate of the switching transistor 61 via the scanning line 55, the switching transistor 61 is turned on, and the image data signal applied to the drain is supplied to the capacitor 63 and the driving transistor 62. Is transmitted to the gate.
By transmitting the image data signal, the capacitor 63 is charged according to the potential of the image data signal, and the drive of the drive transistor 62 is turned on. The drive transistor 62 has a drain connected to the power supply line 67 and a source connected to the electrode of the organic EL element 60, and the power supply line 67 changes to the organic EL element 60 according to the potential of the image data signal applied to the gate. Current is supplied.

When the scanning signal moves to the next scanning line 55 by the sequential scanning of the control unit B, the driving of the switching transistor 61 is turned off. However, even if the driving of the switching transistor 61 is turned off, the capacitor 63 holds the potential of the charged image data signal, so that the driving of the driving transistor 62 is kept on and the next scanning signal is applied. Until then, the organic EL element 60 continues to emit light. When the scanning signal is next applied by sequential scanning, the driving transistor 62 is driven according to the potential of the next image data signal synchronized with the scanning signal, and the organic EL element 60 emits light. That is, the organic EL element 60 emits light by providing a switching transistor 61 and a driving transistor 62, which are active elements, for each of the organic EL elements 60 of a plurality of pixels, and a plurality of pixels 53 (not shown in FIG. 6) Each organic EL element 60 emits light. Such a light emitting method is called an active matrix method.

Here, the light emission of the organic EL element 60 may be light emission of a plurality of gradations by a multi-value image data signal having a plurality of gradation potentials, or on / off of a predetermined light emission amount by a binary image data signal. But you can.
The potential of the capacitor 63 may be held continuously until the next scanning signal is applied, or may be discharged immediately before the next scanning signal is applied.

In the present invention, not only the active matrix method described above, but also a passive matrix light emission drive in which the organic EL element emits light according to the data signal only when the scanning signal is scanned.
FIG. 8 is a schematic view of a passive matrix display device. In FIG. 8, a plurality of scanning lines 55 and a plurality of image data lines 56 are provided in a lattice shape so as to face each other with the pixel 53 interposed therebetween. When the scanning signal of the scanning line 55 is applied by sequential scanning, the pixel 53 connected to the applied scanning line 55 emits light according to the image data signal. In the passive matrix method, there is no active element in the pixel 53, and the manufacturing cost can be reduced.

[Photoelectric conversion element and solar cell]
When the coating film of the present invention is a coating film for producing a photoelectric conversion element, the organic compound may be a photoelectric conversion element material such as a p-type organic semiconductor material or an n-type organic semiconductor material. preferable. In this case, the coating film can be suitably used as an organic functional layer constituting the photoelectric conversion element.
Hereinafter, the details of the photoelectric conversion element material, the photoelectric conversion element, and the solar cell will be described.

FIG. 9 is a cross-sectional view showing an example of a solar cell having a single configuration (a configuration having one bulk heterojunction layer) composed of a bulk heterojunction organic photoelectric conversion element.
In FIG. 9, a bulk heterojunction type organic photoelectric conversion element 200 has a transparent electrode (anode) 202, a hole transport layer 207, a bulk heterojunction layer photoelectric conversion section 204, an electron transport layer (or 208 and a counter electrode (cathode) 203 are sequentially stacked.

The substrate 201 is a member that holds the transparent electrode 202, the photoelectric conversion unit 204, and the counter electrode 203 that are sequentially stacked. In the present embodiment, since light that is photoelectrically converted enters from the substrate 201 side, the substrate 201 can transmit the light that is photoelectrically converted, that is, with respect to the wavelength of the light to be photoelectrically converted. A transparent member is preferred. As the substrate 201, for example, a glass substrate or a resin substrate is used. The substrate 201 is not essential. For example, the bulk heterojunction organic photoelectric conversion element 200 may be configured by forming the transparent electrode 202 and the counter electrode 203 on both surfaces of the photoelectric conversion unit 204.

The photoelectric conversion unit 204 is a layer that converts light energy into electrical energy, and includes a bulk heterojunction layer in which a p-type semiconductor material and a n-type semiconductor material that are materials for photoelectric conversion elements are uniformly mixed. Is done.
The p-type semiconductor material functions relatively as an electron donor (donor), and the n-type semiconductor material functions relatively as an electron acceptor (acceptor). Here, the electron donor and the electron acceptor are “an electron donor in which, when light is absorbed, electrons move from the electron donor to the electron acceptor to form a hole-electron pair (charge separation state)”. And an electron acceptor ", which don't just donate or accept electrons like an electrode, but donates or accepts electrons by photoreaction.

In FIG. 9, light incident from the transparent electrode 202 through the substrate 201 is absorbed by the electron acceptor or electron donor in the bulk heterojunction layer of the photoelectric conversion unit 204, and electrons move from the electron donor to the electron acceptor. Thus, a hole-electron pair (charge separation state) is formed.
The generated electric charge is caused by an internal electric field, for example, when the work functions of the transparent electrode 202 and the counter electrode 203 are different, the electrons pass between the electron acceptors and the holes are electron donors due to the potential difference between the transparent electrode 202 and the counter electrode 203. The photocurrent is detected by passing through different electrodes. For example, when the work function of the transparent electrode 202 is larger than the work function of the counter electrode 203, electrons are transported to the transparent electrode 202 and holes are transported to the counter electrode 203.
If the work function is reversed, electrons and holes are transported in the opposite direction.
In addition, by applying a potential between the transparent electrode 202 and the counter electrode 203, the transport direction of electrons and holes can be controlled.
In addition, in order to efficiently transport electrons and holes generated in the photoelectric conversion unit 204 to the transparent electrode 202 and the counter electrode 203, it is preferable to provide an electron transport layer 207 and a hole transport layer 208 as necessary.

Although not shown in FIG. 9, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, a hole injection layer, or a smoothing layer may be included.
Further, for the purpose of further improving the sunlight utilization rate (photoelectric conversion efficiency), a tandem configuration (a configuration having a plurality of bulk heterojunction layers) in which such photoelectric conversion elements are stacked may be used.

FIG. 10 is a cross-sectional view showing a solar cell composed of an organic photoelectric conversion element having a tandem bulk heterojunction layer. In the case of the tandem configuration, the transparent electrode 202 and the first photoelectric conversion unit 209 are sequentially stacked on the substrate 201, the charge recombination layer (intermediate electrode) 205 is stacked, and then the second photoelectric conversion unit 206, Next, by stacking the counter electrode 203, a tandem structure can be obtained.
Examples of materials that can be used for the above layer include n-type semiconductor materials and p-type semiconductor materials described in paragraphs 0045 to 0113 of JP-A-2015-149483.

(Bulk heterojunction layer formation method)
Examples of a method for forming a bulk heterojunction layer in which an electron acceptor and an electron donor are mixed include a vapor deposition method and a coating method (including a casting method and a spin coating method). Among these, the coating method is preferable in order to increase the area of the interface where charges and electrons are separated from each other as described above and to produce a device having high photoelectric conversion efficiency. The coating method is also excellent in production speed.

After coating, it is preferable to perform heating in order to cause removal of residual solvent, moisture and gas, and improvement of mobility and absorption longwave due to crystallization of the semiconductor material. When annealing is performed at a predetermined temperature during the manufacturing process, part of the arrangement or crystallization is microscopically promoted, and the bulk heterojunction layer can have an appropriate phase separation structure. As a result, the carrier mobility of the bulk heterojunction layer is improved and high efficiency can be obtained.
The photoelectric conversion portion (bulk heterojunction layer) 204 may be configured as a single layer in which an electron acceptor and an electron donor are uniformly mixed, but a plurality of the mixture ratios of the electron acceptor and the electron donor are changed. It may consist of layers.

Next, the electrode which comprises an organic photoelectric conversion element is demonstrated.
The organic photoelectric conversion element functions as a battery in which positive and negative charges generated in the bulk heterojunction layer are respectively taken out from the transparent electrode and the counter electrode via the p-type semiconductor material and the n-type semiconductor material, respectively. It is. Each electrode is required to have characteristics suitable for carriers passing through the electrode.

(Counter electrode)
In the present invention, the counter electrode is preferably a cathode for taking out electrons generated in the photoelectric conversion unit. For example, when used as a cathode, the conductive material may be a single layer, or in addition to a conductive material, a resin that holds these may be used in combination.
As the counter electrode material, for example, known cathode conductive materials described in JP2010-272619A, JP2014-078742A, and the like can be used.

(Transparent electrode)
In the present invention, the transparent electrode is preferably an anode having a function of taking out holes generated in the photoelectric conversion part. For example, when used as an anode, an electrode that transmits light having a wavelength of 380 to 800 nm is preferable. As the material, for example, known anode materials described in JP2010-272619A, JP2014-078742A, and the like can be used.

(Intermediate electrode)
Moreover, as a material of the intermediate electrode required in the case of a tandem configuration, a layer using a compound having both transparency and conductivity is preferable. As the material, for example, known intermediate electrode materials described in JP2010-272619A, JP2014-078742A, and the like can be used.
Next, materials other than the electrodes and the bulk heterojunction layer will be described.

(Hole transport layer and electron block layer)
The organic photoelectric conversion device according to the present invention has a hole transport layer / electron block layer intermediate between the bulk hetero junction layer and the transparent electrode in order to more efficiently extract charges generated in the bulk hetero junction layer. It is preferable to have.
As the material for the photoelectric conversion element constituting the hole transport layer, for example, known materials described in JP 2010-272619 A, JP 2014-077872 A, and the like can be used.

(Electron transport layer and hole blocking layer)
The organic photoelectric conversion device according to the present invention more efficiently extracts charges generated in the bulk heterojunction layer by forming an electron transport layer, a hole blocking layer, and a buffer layer between the bulk heterojunction layer and the counter electrode. It is preferable to have these layers.

Also, as the electron transport layer, for example, known materials described in JP 2010-272619 A, JP 2014-078742 A, and the like can be used. The electron transport layer may be a hole blocking layer having a hole blocking function that has a rectifying effect so that holes generated in the bulk heterojunction layer do not flow to the counter electrode side. As a material for forming the hole blocking layer, for example, a known material described in JP-A-2014-078742 can be used.

(Other layers)
For the purpose of improving energy conversion efficiency and improving the lifetime of the element, a structure having various intermediate layers in the element may be employed. Examples of the intermediate layer include a hole block layer, an electron block layer, a hole injection layer, an electron injection layer, an exciton block layer, a UV absorption layer, a light reflection layer, and a wavelength conversion layer.

(substrate)
When light that is photoelectrically converted enters from the substrate side, the substrate is preferably a member that can transmit this photoelectrically converted light, that is, a member that is transparent to the wavelength of the light to be photoelectrically converted. . As the substrate, for example, a glass substrate, a resin substrate and the like are preferably mentioned, but it is desirable to use a transparent resin film from the viewpoint of light weight and flexibility.
There is no restriction | limiting in particular in the transparent resin film which can be preferably used as a transparent substrate by this invention, About the material, a shape, a structure, thickness, etc., it can select suitably from well-known things. For example, known materials described in JP 2010-272619 A, JP 2014-078742 A, and the like can be used.

(Optical function layer)
The organic photoelectric conversion element according to the present invention may have various optical function layers for the purpose of more efficient light reception of sunlight. As the optical functional layer, for example, a light condensing layer such as an antireflection film or a microlens array, or a light diffusing layer that can scatter the light reflected by the counter electrode and enter the bulk heterojunction layer again can be provided. Good.

Examples of the antireflection layer, the light collecting layer, and the light scattering layer include known antireflection layers, light collecting layers, and light scattering layers described in, for example, JP2010-272619A, JP2014-078742A, and the like. Can be used.

(Patterning)
There is no particular limitation on the method and process for patterning the electrode, the power generation layer, the hole transport layer, the electron transport layer, and the like according to the present invention. For example, JP 2010-272619 A, JP 2014-078742 A, etc. The known methods described can be applied as appropriate.

(Sealing)
Moreover, since the produced organic photoelectric conversion element is not deteriorated by oxygen, moisture, or the like in the environment, it is preferable to seal not only the organic photoelectric conversion element but also an organic electroluminescence element by a known method. For example, the methods described in JP2010-272619A, JP2014-078742A, and the like can be used.

Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless there is particular notice, "mass part" or "mass%" is represented.

[Example 1]
<Preparation of solution (A)>
Under a high purity nitrogen atmosphere, a solution (A) in which 5 g of the following DP-1 was dissolved in 1 L of nPr acetate (normal propyl acetate) (Kanto Chemical Co., Ltd., dehydrated in advance) was obtained.

<Preparation of solutions (B) to (M)>
Solutions (B) to (M) were prepared in the same manner as in the preparation of the solution (A) except that nPr acetate and DP-1 were changed to the solvents and compounds shown in Table I below. All solvents used were dehydrated in advance. The materials of the compounds used are shown below.

<Processing (S1) to (S3)>
The solutions (A) to (M) prepared above were treated as shown in Table I (no treatment, (S1) to (S3)) to obtain coating solutions 1 to 34, respectively.
(S1: Preparation of coating solution by ultrasonic treatment)
The solution was sealed in a glass bottle and sonicated under the following conditions.
Equipment: Desktop ultrasonic cleaner (manufactured by ASONE)
Transmission frequency: 40 kHz
Time: 10 minutes

(S2: Preparation of coating solution by column chromatography)
The solution was subjected to column chromatography under a nitrogen atmosphere (in a glove box). The solution used for the original solutions (A) to (M) was used as the developing solution, and the eluate was concentrated under reduced pressure to adjust the solution concentration to be the same as that of the original solution.
Column: Silica gel (Fuji Silysia Chemical)

(S3: Preparation of coating solution by supercritical chromatography)
Supercritical chromatography was performed under the following conditions.
Equipment: Prep15 (Nippon Waters)
Column: Torus 2-PIC, 5 μm, 10.0 mm × 150 mm
Moving bed: carbon dioxide / acetic acid nPr = 93/7
Moving bed flow rate: 10 mL / min
Pressure: 18MPa
Temperature: 40 ° C
Detection: PDA (254 nm)

<Evaluation of coating solution>
(1) Particle size distribution analysis of small-angle X-ray scattering measurement result of coating liquid Small-angle X-ray scattering measurement was performed on the coating liquid sample obtained in Example 1, and particle size distribution analysis was performed on the obtained data. For X-rays, SPring-8 radiation was used to irradiate the coating liquid sample at a wavelength of 0.1 nm. The measurement is performed using a HUBER multi-axis diffractometer, the X-ray incident angle θ is fixed at 0.2 °, and the coating liquid sample is irradiated. The detector uses a scintillation counter to measure scattered radiation from 1 to 43 °. Went. From the obtained scattering diffraction data, a particle size distribution curve (horizontal axis particle size (nm), vertical axis: frequency distribution) was created using analysis software (particle size / hole size analysis software NANO-Solver manufactured by Rigaku Corporation).
The particle size corresponding to the maximum peak in the particle size distribution curve was calculated as R ′. In the case of having a plurality of maximum peaks, the particle diameter corresponding to the maximum peak showing the minimum particle diameter among these maximum peaks was calculated as R ′. Further, the value of n was determined by the following formula.
(Formula) n = R '/ r
In addition, r is the molecular radius r = of the organic compound when the molecular long axis length obtained by density functional theory calculation of the compound is 2a (nm) and the molecular short axis length is 2b (nm). (A × b) represents ^1/2 . ]
For the coating solution in which the maximum peak existed, the maximum peak corresponding to the particle size R ′ in each coating solution was the maximum peak with the largest frequency distribution among the maximum peaks in the particle size distribution curve.
Note that r of DP-1 was 0.86 nm (major axis length 2.28 nm, minor axis length 1.17 nm). For other compounds, r was determined in the same manner, and the value of n was calculated.
Further, the full width at half maximum of the maximum peak indicating the particle size having the smallest particle size value was calculated, and the results are shown in Table I. In addition, when the half width exceeds 10 nm or when the determination is difficult, it is indicated by x.

(2) Particle size distribution analysis of small-angle X-ray scattering measurement result of coating film Each coating solution obtained in Example 1 was formed by spin coating at 1500 rpm for 30 seconds, and then held at 80 ° C. for 30 minutes. A coating film having a thickness of 40 nm was formed on a silicon wafer to obtain a measurement sample. For X-rays, SPring-8 synchrotron radiation was used to irradiate the coating film sample with a wavelength of 0.1 nm. For measurement, a multi-axis diffractometer manufactured by HUBER is used, the X-ray incident angle θ is fixed at 0.2 °, and the coated film sample is irradiated. The detector uses a scintillation counter to measure scattered radiation from 1 to 43 °. Went. A particle size distribution curve (horizontal axis particle size (nm), vertical axis: frequency distribution) was created from the obtained scattering diffraction data using the above-described analysis software.
Moreover, the particle size corresponding to the maximum peak in the particle size distribution curve was calculated as R. In addition, when it had a plurality of maximum peaks, the particle size corresponding to the maximum peak indicating the minimum particle size among these maximum peaks was calculated as R. Further, the value of n was determined by the following formula.
(Formula) n = R / r
In addition, r is the molecular radius r = (of the organic compound when the molecular major axis length obtained by density functional theory calculation of the compound is 2a (nm) and the molecular minor axis length is 2b (nm). a × b) represents ^1/2 .
For the coating film having the maximum peak, the maximum peak corresponding to the particle size R in each coating film was the maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve.
Further, the half-value width of the maximum peak showing the smallest particle size and the frequency distribution of the maximum peak were calculated, and the results are shown in Table I. In addition, when the half width exceeds 10 nm or when the determination is difficult, it is indicated by x.

(3) Luminescence intensity measurement A quartz substrate having a size of 50 mm × 50 mm and a thickness of 0.7 mm was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. The quartz substrate was placed in a spin coater, and each (dopant) coating solution obtained in Example 1 was formed by spin coating at 1500 rpm for 30 seconds, and then held at 80 ° C. for 30 minutes to obtain a film thickness of 40 nm. A coating film was formed on a quartz substrate to obtain a measurement sample.
Each of the produced measurement samples was irradiated with ultraviolet rays having an excitation wavelength of 365 nm at 23 ° C., and the photoluminescence intensity was measured. The emission intensity of each coating film is shown in Table I with the emission intensity of the coating film obtained by solidifying the solutions (A) to (M) serving as the mother liquor being 100. Note that USB2000 (manufactured by Ocean Optics) was used for measuring the emission intensity.

[Example 2]
<Preparation of organic EL element 101>
As shown below, the anode / hole injection layer / hole transport layer / light emitting layer / blocking layer / electron transport layer / electron injection layer / cathode are laminated and sealed on the base material to form a bottom emission type organic material. An EL element 101 was produced.
(Preparation of base material)
First, an atmospheric pressure plasma discharge treatment apparatus having a configuration described in Japanese Patent Application Laid-Open No. 2004-68143 is used on the entire surface of the polyethylene naphthalate film (manufactured by Teijin DuPont, hereinafter abbreviated as PEN) on the anode forming side. Then, an inorganic gas barrier layer made of SiO _x was formed to a thickness of 500 nm. Thus, a flexible base material having a gas barrier property with an oxygen permeability of 0.001 mL / (m ² · 24 h) or less and a water vapor permeability of 0.001 g / (m ² · 24 h) or less was produced.

(Formation of anode)
A 120 nm-thick indium tin oxide (ITO) film was formed on the substrate by sputtering, and patterned by photolithography to form an anode. The pattern was such that the area of the light emitting region was 5 cm × 5 cm.

(Formation of hole injection layer)
The substrate on which the anode was formed was subjected to ultrasonic cleaning with isopropyl alcohol, dried with dry nitrogen gas, and UV ozone cleaning was performed for 5 minutes. Then, a dispersion of poly (3,4-ethylenedioxythiophene) / polystyrene sulfonate (PEDOT / PSS) prepared in the same manner as in Example 16 of Japanese Patent No. 4509787 was placed on the substrate on which the anode was formed. The 2% by weight solution diluted in (1) was applied by an ink jet method and dried at 80 ° C. for 5 minutes to form a hole injection layer having a layer thickness of 40 nm.

(Formation of hole transport layer)
Next, the base material on which the hole injection layer is formed is transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and is applied by an inkjet method using a coating liquid for forming a hole transport layer having the following composition. It dried at 130 degreeC for 30 minutes, and formed the 30-nm-thick hole transport layer.
<Coating liquid for hole transport layer formation>
Hole transport material (the following compound (60)) (weight average molecular weight Mw = 80000)
10 parts by mass Chlorobenzene 3000 parts by mass

(Formation of light emitting layer)
Next, the base material on which the hole transport layer was formed was applied by an inkjet method using a light emitting layer forming coating solution having the following composition, and dried at 120 ° C. for 30 minutes to form a light emitting layer having a layer thickness of 50 nm. . The light emitting layer forming coating solution was prepared by forming the following host coating solution and then adding the following fluorescent light emitting dopant.
<Host coating solution>
Host compound (H-1) 10 parts by mass Isopropyl acetate 2200 parts by mass <Light emitting layer forming coating solution>
Host compound (H-1) 10 parts by weight Fluorescent emission dopant (DP-1) 1 part by weight Isopropyl acetate 2200 parts by weight

(Formation of electron transport layer)
Next, the substrate on which the light emitting layer was formed was applied by an ink jet method using an electron transport layer forming coating solution having the following composition, and dried at 80 ° C. for 30 minutes to form an electron transport layer having a layer thickness of 30 nm. . <Coating liquid for electron transport layer formation>
6 parts by mass of Compound A
2,2,3,3-tetrafluoro-1-propanol (TFPO)
2000 parts by mass

(Formation of electron injection layer and cathode)
Subsequently, the substrate was attached to a vacuum deposition apparatus without being exposed to the atmosphere. Further, a molybdenum resistance heating boat containing sodium fluoride and potassium fluoride was attached to a vacuum vapor deposition apparatus, and the vacuum chamber was depressurized to 4 × 10 ⁻⁵ Pa. Thereafter, the boat was energized and heated, and sodium fluoride was deposited on the electron transport layer at 0.02 nm / second to form a thin film having a thickness of 1 nm. Similarly, potassium fluoride was vapor-deposited on the sodium fluoride thin film at 0.02 nm / second to form an electron injection layer having a layer thickness of 1.5 nm.
Subsequently, aluminum was deposited to form a cathode having a thickness of 100 nm.

(Sealing)
The sealing base material was adhere | attached on the laminated body formed by the above process using the commercially available roll laminating apparatus.
Adhesion as a sealing substrate with a thickness of 1.5 μm using a flexible aluminum foil (manufactured by Toyo Aluminum Co., Ltd.) with a thickness of 30 μm using a two-component reaction type urethane adhesive for dry lamination. An agent layer was provided, and a laminate of a polyethylene terephthalate (PET) film having a thickness of 12 μm was prepared.
A thermosetting adhesive as a sealing adhesive was uniformly applied at a thickness of 20 μm along the adhesive surface (shiny surface) of the aluminum foil of the sealing substrate using a dispenser. This was dried under a vacuum of 100 Pa or less for 12 hours. Further, the sealing substrate is moved to a nitrogen atmosphere having a dew point temperature of −80 ° C. or lower and an oxygen concentration of 0.8 ppm and dried for 12 hours or longer so that the moisture content of the sealing adhesive is 100 ppm or lower. It was adjusted.
As the thermosetting adhesive, an epoxy adhesive mixed with the following (A) to (C) was used.
(A) Bisphenol A diglycidyl ether (DGEBA)
(B) Dicyandiamide (DICY)
(C) Epoxy adduct-based curing accelerator The sealing base material is closely attached to the laminate, and a pressure roll is used at a pressure roll temperature of 100 ° C., a pressure of 0.5 MPa, and an apparatus speed of 0.3 m / second. It was tightly sealed under a pressure bonding condition of min.
The organic EL element 101 was produced as described above.

<Production of organic EL elements 102 to 110>
In the production of the organic EL element 101, the host material contained in the host coating solution is changed as shown in Table II, and the above-described S1 (ultrasonic treatment) or S3 (supercritical chromatographic treatment) treatment is performed on a part thereof. Then, organic EL elements 102 to 110 were produced in the same manner except that a fluorescent dopant (DP-1) was added to form a light emitting layer forming coating solution and a light emitting layer was formed.

<Evaluation of organic EL elements 101 to 110>
The following evaluation was performed about each organic EL element produced as mentioned above. The evaluation results are shown in Table II.
(1) Luminous efficiency measurement Luminous efficiency is measured at room temperature (25 ° C) at a constant current density of ^2.5 mA / cm ² and a spectral radiance meter CS-2000 (manufactured by Konica Minolta). Was used to measure the light emission luminance of each organic EL element, and the light emission efficiency (external extraction efficiency) at the current value was determined. The light emission efficiency of the organic EL element 101 (comparative example) was expressed as a relative value with 100.

(2) Measurement of luminous lifetime Luminous lifetime is measured by driving each organic EL element continuously under the conditions of room temperature 25 ° C and humidity 55% RH, and measuring the luminance using a spectral radiance meter CS-2000. The time (half life) during which the brightness was reduced by half was determined as a measure of life. The driving condition was set to a current value of 1000 cd / m ² at the start of continuous driving. And it represented with the relative value which sets the light emission lifetime of the organic EL element 101 (comparative example) to 100.

<Evaluation of single layer coating film>
(1) Particle size distribution analysis of small-angle X-ray scattering measurement results In (2) small-angle X-ray scattering measurement of the coating film of Example 1 above, except that the coating solution is changed to the above-described coating solution for forming a light emitting layer. After obtaining the particle size distribution curve, the particle size value R corresponding to the maximum peak in the particle size distribution curve was calculated. In addition, when it had a plurality of maximum peaks, the particle size corresponding to the maximum peak indicating the minimum particle size among these maximum peaks was calculated as R.
For the coating film having the maximum peak, the maximum peak corresponding to the particle size R in each coating film was the maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. Further, the value of n was determined, and the half-value width of the maximum peak indicating the smallest particle size and the frequency distribution of the maximum peak were calculated. The results are shown in Table II. In addition, when the half width exceeds 10 nm or the determination is difficult, it is indicated by x.

From the results shown in Table II, it can be seen that the organic EL device of the present invention is superior in luminous efficiency and luminous lifetime as compared with the organic EL device of the comparative example.

<Preparation of organic EL element 201>
In the production of the organic EL element 101, an organic EL element 201 was produced in the same manner except that the light emitting layer forming coating solution was changed to the following materials and compositions.
<Light emitting layer forming coating solution>
Host compound (H-1) 10 parts by mass
Luminescent dopant (DP-2) 1.5 parts by mass Isopropyl acetate 2200 parts by mass

<Preparation of organic EL elements 202 to 210>
In the production of the organic EL element 201, the host material contained in the light-emitting layer forming coating solution was changed as shown in Table III, and S1 (ultrasonic treatment) or S3 (supercritical chromatographic treatment) described above for a part thereof The organic EL elements 202 to 210 were produced in the same manner except that the light emitting layer was formed by performing the above-described treatment to form a light emitting layer forming coating solution.

<Evaluation of organic EL elements 201 to 210>
The following evaluation was performed about each organic EL element produced as mentioned above. The evaluation results are shown in Table III.
(1) Luminous efficiency measurement Luminous efficiency is measured at room temperature (25 ° C) at a constant current density of ^2.5 mA / cm ² and a spectral radiance meter CS-2000 (manufactured by Konica Minolta). Was used to measure the light emission luminance of each organic EL element, and the light emission efficiency (external extraction efficiency) at the current value was determined. It represents with the relative value which sets the luminous efficiency of the organic EL element 201 (comparative example) to 100.

(2) Measurement of luminescence lifetime The luminescence lifetime is measured by continuously driving each organic EL element under the conditions of room temperature 25 ° C and humidity 40% RH, and measuring the luminance using a spectral radiance meter CS-2000. The time (half life) during which the brightness was reduced by half was determined as a measure of life. The driving condition was set to a current value of 10,000 cd / m ² at the start of continuous driving. And it represented with the relative value which sets the light emission lifetime of the organic EL element 201 (comparative example) to 100.

<Evaluation of single layer coating film>
(1) Particle size distribution analysis of small-angle X-ray scattering measurement results In (2) small-angle X-ray scattering measurement of the coating film of Example 1 above, except that the coating solution is changed to the above-described coating solution for forming a light emitting layer. After obtaining the particle size distribution curve, the particle size value R corresponding to the maximum peak in the particle size distribution curve was calculated. In addition, when it had a plurality of maximum peaks, the particle size corresponding to the maximum peak indicating the minimum particle size among these maximum peaks was calculated as R.
For the coating film having the maximum peak, the maximum peak corresponding to the particle size R in each coating film was the maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. Further, the value of n was obtained, the half-value width of the maximum peak showing the smallest particle size and the frequency distribution of the maximum peak were calculated, and the results are shown in Table III. In addition, when the half width exceeds 10 nm or the determination is difficult, it is indicated by x.

From the results shown in Table III, it can be seen that the organic EL device of the present invention is superior in luminous efficiency and luminous lifetime as compared with the organic EL device of the comparative example.

<Preparation of organic EL element 301>
(Formation of anode)
Patterning was performed on a substrate (NA45 manufactured by AvanStrate Co., Ltd.) in which an indium tin oxide (ITO) film having a thickness of 100 nm was formed on a glass substrate of 100 mm × 100 mm × 1.1 mm as an anode, and then this ITO transparent electrode was provided. The transparent support substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes.

(Formation of hole injection layer)
A thin film was formed on this transparent support substrate by spin coating using a solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS) with pure water at 3000 rpm for 30 seconds. After the formation, it was dried at 200 ° C. for 1 hour to provide a hole injection layer having a thickness of 20 nm.

(Formation of hole transport layer)
The transparent support substrate is fixed to a substrate holder of a commercially available vacuum deposition apparatus, while 250 mg of α-NPD is placed in a molybdenum resistance heating boat, and 200 mg of compound A is placed in another molybdenum resistance heating boat. Attached.
Next, the pressure in the vacuum chamber was reduced to 4 × 10 ⁻⁴ Pa, and the heating boat containing α-NPD was energized and heated, and deposited on the hole injection layer at a deposition rate of 0.1 nm / second to 20 nm. The hole transport layer was provided.

(Formation of light emitting layer)
The substrate fabricated up to the hole transport layer was moved into a glove box under a nitrogen atmosphere. A light emitting layer forming coating solution having the following composition was mixed, and a thin film was formed by spin coating under conditions of 700 rpm and 25 seconds. Furthermore, drying under reduced pressure (5 hpa or less, 30 ° C., 30 minutes) was performed to form a light emitting layer having a layer thickness of 50 nm.
<Light emitting layer forming coating solution>
Host compound (H-2) 10 parts by weight Luminescent dopant (DP-2) 1.2 parts by weight Solvent (normal propyl acetate) 2200 parts by weight

(Formation of hole blocking layer)
The substrate on which the light emitting layer was formed was returned to the vacuum deposition apparatus, heated by energizing a heating boat containing the compound (H-2), and deposited on the light emitting layer at a deposition rate of 0.1 nm / second. A hole blocking layer was provided.

(Formation of electron transport layer)
Further, the heating boat containing the compound A was energized and heated, and deposited on the light emitting layer at a deposition rate of 0.1 nm / second to provide a 40 nm electron transport layer.

(Formation of cathode)
Then, 0.5 nm of lithium fluoride was vapor-deposited as an electron injection layer (cathode buffer layer), and also aluminum 110nm was vapor-deposited, the cathode was formed, and the organic EL element 301 was produced.

<Preparation of organic EL elements 302 to 315>
In the production of the organic EL element 301, organic EL elements 302 to 315 were produced in the same manner except that the host material and the solvent contained in the light emitting layer forming coating solution were changed as shown in Table IV.

<Evaluation of organic EL elements 301 to 315>
The following evaluation was performed about each organic EL element produced as mentioned above. The evaluation results are shown in Table IV.
(1) Luminous efficiency measurement Luminous efficiency is measured at room temperature (25 ° C) at a constant current density of ^2.5 mA / cm ² and a spectral radiance meter CS-2000 (manufactured by Konica Minolta). Was used to measure the light emission luminance of each organic EL element, and the light emission efficiency (external extraction efficiency) at the current value was determined. It represents with the relative value which sets the luminous efficiency of the organic EL element 301 (comparative example) to 100.

(2) Measurement of luminescence lifetime The luminescence lifetime is measured by continuously driving each organic EL element under the conditions of room temperature 25 ° C and humidity 40% RH, and measuring the luminance using a spectral radiance meter CS-2000. The time (half life) during which the brightness was reduced by half was determined as a measure of life. The driving condition was set to a current value of 10,000 cd / m ² at the start of continuous driving. And it represented with the relative value which sets the light emission lifetime of the organic EL element 301 (comparative example) to 100.

(3) Measurement of voltage change The voltage change is measured by (1) measuring the voltage at the time of measuring the luminous efficiency as the initial voltage Vs, and (2) in the measurement of the light emission lifetime, the driving voltage at the time when the luminance is halved is measured. The voltage Vf after deterioration was evaluated according to the following formula.
(Drive voltage change) = (Deteriorated voltage Vf) / (Initial voltage (Vs)) × 100
Table IV shows the change in voltage according to the following criteria. ○ is desirable.
◯: Change in drive voltage is 1.0 or more and less than 1.5 Δ: Change in drive voltage is 1.5 or more and less than 2.0 ×: Change in drive voltage is 2.0 or more

<Evaluation of single layer coating film>
(1) Particle size distribution analysis of small-angle X-ray scattering measurement results In (2) small-angle X-ray scattering measurement of the coating film of Example 1 above, except that the coating solution is changed to the above-described coating solution for forming a light emitting layer. After obtaining the particle size distribution curve, the particle size value R corresponding to the maximum peak in the particle size distribution curve was calculated. In addition, when it had a plurality of maximum peaks, the particle size corresponding to the maximum peak indicating the minimum particle size among these maximum peaks was calculated as R.
For the coating film having the maximum peak, the maximum peak corresponding to the particle size R in each coating film was the maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. Furthermore, the value of n was calculated | required and the half value width of the maximum peak which shows the particle size with the smallest particle size value, and the frequency distribution of this maximum peak were computed. Then, the value of n, the frequency distribution of the maximum peak, and the half width were evaluated according to the following criteria, and the results are shown in Table IV.

<N (= R / r)>
◎: n is less than 6.0 ○: n is less than 10.0, 6.0 or more △: n is less than 18.0, 10.0 or more ×: n is 18.0 or more <Maximum peak frequency distribution>
○: Frequency distribution of maximum peak is 0.5 or more Δ: Frequency distribution of maximum peak is 0.3 or more and less than 0.5 ×: Frequency distribution of maximum peak is less than 0.3 <Half width>
◎: Half width is less than 3.0 nm ○: Half width is 3.0 nm or more and less than 6.0 nm △: Half width is 6.0 nm or more and less than 10.0 nm X: Half width is 10.0 nm or more

From the results shown in Table IV, it can be seen that the organic EL device of the present invention is superior in terms of light emission efficiency, light emission lifetime and driving voltage as compared with the organic EL device of the comparative example.

INDUSTRIAL APPLICABILITY The present invention can be used for a coating film having a small particle size of organic compound particles in the film and a method for producing the same, and is also used for an organic electroluminescence device excellent in luminous efficiency and durability using the coating film. can do.

20 Solute molecule 21 Solvent molecule 22 Cluster 41 Display (display device)
60 Organic EL element 200 Organic photoelectric conversion element

Claims (10)

A coating film comprising at least a single organic compound,
Having at least one maximum peak in the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of the molecule or aggregate obtained from the small angle X-ray scattering measurement, and
The coating film containing the organic compound which the following R and r satisfy | fill the relationship represented by following formula (1).
Formula (1): R <= 15r
[In Formula (1), R represents the particle size corresponding to the maximum peak which shows a particle size with the smallest particle size among the maximum peaks of the particle size distribution curve obtained from a small angle X-ray scattering measurement. When the molecular long axis length obtained by density functional theory calculation for the organic compound is 2a (nm) and the molecular short axis length is 2b (nm), the molecular radius of the organic compound r = (A × b) represents ^1/2 . ] The coating film according to claim 1, wherein R represents a particle size corresponding to a maximum peak having the largest frequency distribution among the maximum peaks of the particle size distribution curve. The coating film according to claim 1 or 2, wherein the frequency distribution of the maximum peak satisfying the formula (1) is 0.4 or more. The coating film as described in any one of Claim 1- Claim 3 which satisfy | fills following formula (2).
Formula (2): R ≦ 8r
[In Formula (2), R and r are synonymous with R and r in said Formula (1). ] The coating film according to any one of claims 1 to 4, wherein a half-value width of the maximum peak satisfying the formula (1) is in a range of 0.3 to 3.0 nm. The coating film according to any one of claims 1 to 5, comprising a plurality of types of organic compounds satisfying the formula (1). The following R 'and r are films formed by solidifying a coating solution containing an organic compound that satisfies the relationship represented by the following formula (3). Coating film.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ] A manufacturing method of a coating film for manufacturing the coating film according to any one of claims 1 to 7,
A step of preparing a coating solution containing an organic compound in which R ′ and r below satisfy the relationship represented by the following formula (3);
And a step of drying and solidifying the coating solution.
Formula (3): R ′ ≦ 6r
[In formula (3), R ′ is the particle size corresponding to the maximum peak indicating the smallest particle size among the maximum peaks of the particle size distribution curve obtained from the small angle X-ray scattering measurement of the coating solution. To express. r is synonymous with r in the formula (1). ] An organic electroluminescence device having the coating film according to any one of claims 1 to 7 in at least one of the organic functional layers. The organic electroluminescent element according to claim 9, wherein the organic functional layer is a light emitting layer.

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