WO2018174117A1

WO2018174117A1 - Coating liquid for forming organic film, organic film, organic electronic device, and method for producing coating liquid for forming organic film

Info

Publication number: WO2018174117A1
Application number: PCT/JP2018/011247
Authority: WO
Inventors: 昌紀後藤; 北　弘志; 昇関根
Original assignee: コニカミノルタ株式会社
Priority date: 2017-03-23
Filing date: 2018-03-22
Publication date: 2018-09-27
Also published as: JP6933248B2; JPWO2018174117A1

Abstract

The present invention addresses the problem of providing a coating liquid for forming an organic film in which an organic compound is finely dispersed, an organic film obtained by coating the coating liquid, and an organic electronic device that comprises the organic film and is excellent in durability and conversion efficiency. The present invention also addresses the problem of providing a method for producing a coating liquid for forming an organic film. The coating liquid for forming an organic film of the present invention comprises an organic compound as a solute and at least two kinds of solvents which are a solvent (1) and a solvent (2), the coating liquid being characterized in that the solubility of the organic compound at 20°C is less than 5 mass% in the solvent (1) while 5 mass% or more in the solvent (2), and the amount of the solvent (2) contained is within the range of 1-1000 ppm by mass in relation to the total solvent amount, and the organic compound is dispersed as molecules or aggregates.

Description

Organic film forming coating liquid, organic film, organic electronic device, and method for producing organic film forming coating liquid

The present invention relates to a coating liquid for forming an organic film, an organic film, an organic electronic device, and a method for producing a coating liquid for forming an organic film. More specifically, a coating liquid for forming an organic film in which an organic compound is finely dispersed, an organic film that is the coating film, an organic electronic device having the organic film with excellent durability and conversion efficiency, and for forming an organic film The present invention relates to a method for producing a coating liquid.

Various organic electronic devices such as organic electroluminescence elements (also referred to as “organic EL elements”), organic photoelectric conversion elements, and organic transistors have been developed using organic compounds. It is spreading in various industrial and market fields.

For example, organic EL elements, which are typical examples of organic electronic devices, have started 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 derived from the use of organic compounds as electronic device materials 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 emission lifetime and further improvement in productivity, that is, cost reduction.

Among the above-mentioned ultimate problems, it seems that the performance problems of the organic EL element manufactured by the vacuum deposition method 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.

Therefore, a wet coating method (hereinafter also simply referred to as a coating method) is expected as a film forming method replacing the vacuum deposition method. The coating method has an advantage in terms of cost as compared with the vacuum evaporation method, and has an advantage that it is easy to increase the area technically.

For example, when producing an organic EL element by a coating method, it is important that an organic material forms an amorphous organic film in order to bring out the excellent characteristics of the organic EL element, but the organic material is dissolved in a solvent. In order to form an amorphous organic film using a coating solution, it is indispensable that the organic material in the coating solution is close to a single molecule and is finely dispersed.

In a coating solution using a poor solvent as a solvent for the organic material, it is difficult to finely disperse the organic compound during the coating solution, and a cluster formed by a large number of organic material molecules tends to be dispersed.

As a countermeasure, if a so-called good solvent with high solubility such as chlorobenzene is used to finely disperse the organic material, it takes time to dry the coating film due to the strong interaction between the solvent and the organic material. As a result, there are problems such as an increase in manufacturing cost, a decrease in luminous efficiency of the organic EL element, and a decrease in driving life due to the good solvent remaining after drying.

On the other hand, for example, Patent Document 1 discloses a purification method in which an organic electroluminescent material is injected into a supercritical solvent and impurities are removed using a chromatographic method. However, even when the coating liquid containing the organic material purified in this way is used, the performance improvement of the organic EL element is not sufficient.

Japanese Patent Laid-Open No. 2005-02257

The present invention has been made in view of the above-described problems and situations, and the problem to be solved includes a coating liquid for forming an organic film in which an organic compound is finely dispersed, an organic film that is the coating film, and the organic film. It is to provide an organic electronic device having excellent durability and conversion efficiency. Moreover, it is providing the manufacturing method of the coating liquid for organic film formation.

In order to solve the above-mentioned problems, the present inventor conducted an examination from the viewpoint that it is important that an organic compound forms an amorphous organic film in the process of examining the cause of the above-mentioned problem. In order to form the organic film, it is important that the organic compound as the material of the organic electronic device in the coating liquid is finely dispersed close to a single molecule or a small molecule aggregate, The present inventors have found that the problem can be solved by using a coating solution for forming an organic film using a mixed solvent of a specific ratio containing a good solvent and a poor solvent for an organic compound and having a small amount of good solvent.

That is, the above-mentioned problem according to the present invention is solved by the following means.

1. A coating solution for forming an organic film containing an organic compound as a solute and at least two kinds of solvents (1) and (2), wherein the solubility of the organic compound at 20 ° C. is 5 for the solvent (1). Less than mass%, 5 mass% or more in the solvent (2), the content ratio of the solvent (2) is in the range of 1 to 1000 mass ppm with respect to the total amount of solvent, and the organic compound Is dispersed as a molecule or an aggregate. A coating solution for forming an organic film.

2. In the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of single molecules derived from the organic compound or their aggregates obtained from small angle X-ray scattering measurement for the coating solution for forming an organic film 2. The coating solution for forming an organic film according to item 1, which has a maximum maximum peak in a region having a particle size of 5 nm or less and a half width within a range of 0.5 to 5.0 nm. .

3. An organic film, which is a coating film of the coating liquid for forming an organic film according to item 1 or 2.

4. An organic electronic device comprising the organic film according to item 3.

5. It is a manufacturing method of the coating liquid for organic film formation which manufactures the coating liquid for organic film formation of Claim 1 or Claim 2, Comprising: The said solvent (1) and the said solvent (2) are contained, and the said solvent ( A dissolution step of preparing a solvent having a content ratio of 2) in the range of 1 to 1000 ppm by mass with respect to the total amount of solvent, and dissolving the organic compound in the prepared solvent to obtain a coating solution for forming an organic film The manufacturing method of the coating liquid for organic film formation characterized by having.

6. It is a manufacturing method of the coating liquid for organic film formation which manufactures the coating liquid for organic film formation of Claim 1 or Claim 2, Comprising: After preparing the solution which melt | dissolved the said organic compound in the said solvent (2), Using the solvent (1) as a mobile phase and separating the solvent (2) by chromatography from the solution in which the organic compound is dissolved, the content ratio of the solvent (2) is reduced with respect to the total amount of solvent. A method for producing a coating liquid for forming an organic film, comprising a separation step of obtaining a coating liquid for forming an organic film within a range of 1 to 1000 ppm by mass.

7. The method for producing a coating liquid for forming an organic film according to item 6, wherein the mobile phase contains supercritical carbon dioxide.

By the above means of the present invention, a coating liquid for forming an organic film in which an organic compound is finely dispersed, an organic film that is the coating film, and an organic electronic device having the durability and conversion efficiency provided with the organic film are provided. be able to. Moreover, the manufacturing method of the coating liquid for organic film formation can be provided.

The expression mechanism or action mechanism of the effect of the present invention is not clear, but is presumed as follows.

In the coating solution for forming an organic film of the present invention, the organic compound in the coating solution contains a solvent (2) that is a good solvent for the organic compound and a solvent (1) that is a poor solvent, and contains the solvent (2). It is presumed that the organic compound can be finely dispersed because it is a mixed solvent within a specific range with a small ratio. For this reason, the organic film that is the coating film of this coating solution can be an amorphous organic film in which the organic compound is the same as the deposited film, and an organic film with good performance similar to the deposited film can be obtained. It is considered possible.

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 liquid for organic film formation 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

The coating solution for forming an organic film of the present invention is a coating solution for forming an organic film containing an organic compound as a solute and at least two solvents (1) and a solvent (2). The solvent (1) has a solubility of less than 5% by mass, the solvent (2) has a solubility of 5% by mass or more, and the content ratio of the solvent (2) is 1 to 1000 ppm by mass relative to the total amount of solvent. And the organic compound is dispersed as molecules or aggregates. This feature is a technical feature common to the claimed invention.

As an embodiment of the present invention, a particle size distribution curve of a single molecule derived from the organic compound or an aggregate thereof obtained from small angle X-ray scattering measurement for the coating solution for forming an organic film (horizontal axis: particle size) , Vertical axis: frequency distribution), the maximum maximum peak is in a region having a particle diameter of 5 nm or less, and the half-value width is in the range of 0.5 to 5.0 nm. From the viewpoint, it is preferable. Moreover, it is preferable that it is an organic film which is a coating film of the coating liquid for organic film formation.

Furthermore, the organic film of the present invention can be suitably provided in an organic electronic device.

Moreover, as a manufacturing method of the coating liquid for organic film formation which manufactures the coating liquid for organic film formation of this invention, the said solvent (1) and the said solvent (2) are contained, and the content ratio of the said solvent (2) is A production method of an embodiment having a dissolution step of preparing a solvent in the range of 1 to 1000 ppm by mass with respect to the total amount of solvent, and dissolving the organic compound in the prepared solvent to obtain a coating solution for forming an organic film It is preferable that

Furthermore, as a manufacturing method of the coating liquid for organic film formation which manufactures the coating liquid for organic film formation of this invention, after preparing the solution which melt | dissolved the said organic compound in the said solvent (2), the said solvent (as a mobile phase) 1), the solvent (2) is separated by chromatography from the solution in which the organic compound is dissolved, and the content ratio of the solvent (2) is 1 to 1000 ppm by mass with respect to the total amount of the solvent. It is preferable from the viewpoint that dispersion can be promoted that the production method has a separation step of obtaining a coating solution for forming an organic film within the range.

Furthermore, it is more preferable that the mobile phase contains supercritical carbon dioxide from the viewpoint of further promoting the dispersion and shortening the production time by increasing the speed.

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.

(Outline of the coating solution for forming an organic film of the present invention)
The present invention has been studied and completed based on the following basic policies (1) to (5).
(1) The organic EL compound is preferably a low molecule (a polymer is not preferred).
(2) The film forming method is preferably a coating method (a vapor deposition method is not preferable).
(3) 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. Advantages of low molecular weight compounds over high molecular weight compounds In the formation of an organic functional layer by a wet coating method, why the use of low molecular weight compounds rather than high molecular weight compounds is desired 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 polymer compounds, in most cases, purification is performed by repeatedly performing a reprecipitation method using a good solvent and a poor solvent, and low-molecular compounds are 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. There is also a low molecular weight compound that 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”) becomes narrow, making it difficult to emit blue light. Become. 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 low molecular weight compounds, there is no necessity of linking π-conjugated systems, and aromatic compound residues that become π-conjugated units are necessary, but they can be selected arbitrarily, and can be substituted at any position easily. Blue phosphorescent dopants by deliberately adjusting the energy levels of the highest occupied orbital (HOMO), lowest unoccupied molecular orbital (LUMO), and excited triplet (T ₁ ) states Can be made as a host compound, or a compound that generates a TADF phenomenon can be constructed. In this way, any electronic state or any energy level can be intentionally designed and synthesized. The scale of scalability is the second factor

(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 weight compound Explain what is an essential problem in forming an organic functional layer by a wet coating method using a low molecular weight compound.

Almost all materials used in organic EL elements are different from Ohm's law in the inside of the organic EL element, and by carrier conduction due to space charge limited current (SCLC) according to the child law, Electrons and holes must hop between molecules. Basically, electrons hop through the LUMO energy level, and holes hop using the HOMO energy level.

That is, if adjacent molecules do not exist so that the 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, it is necessary to provide an electric field gradient by providing a potential difference between the anode and the cathode in order to keep the carriers flowing in the organic EL element. For this reason, the equivalent circuit of the organic EL element is a series connection of a diode and a resistor. 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 functional layer of the entire organic EL element is a very thin layer of about 200 nm at most, heat is conducted between the layers (films), and not only the light emitting layer but also all layers continue to be in a high temperature state. Will be. 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.

Furthermore, when this crystal exceeds the entire organic functional layer (100 to 200 nm) of the organic EL element, the anode and the cathode are short-circuited, and electric field concentration occurs there, and a large current flows in a minute region. As a result, the organic compound in the portion is thermally decomposed, and a portion that does not emit light at all, 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). Preferably there is.

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 not used a bulky, highly flexible branched alkyl group such as Japanese Patent No. 5403179 and Japanese Patent Application Laid-Open No. 2014-196258, and aromatics. By connecting only the groups to form a via aryl structure and actively increasing the number of conformations and geometric isomers due to rotational obstacles generated around the CC bond axis, or multiple molecules existing in the same layer (for example, , Host compounds and dopants) interact in various shapes and forms to increase the number of components in the film, thus increasing the entropy in the thin film state, forming a stable amorphous film, and energizing So far, we have developed groundbreaking technology that can hold it.

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. It is found that can be demonstrated. However, many problems still remain in the organic EL element with improved performance.

One of the problems is removal of the purity of the low-molecular compound, the trace amount of water adhering to the surface of the compound, the oxygen content of the solvent used, the water content, and the like.

For example, even for low-molecular compounds generally used in coating, in order to achieve the best performance, after performing column chromatography and recrystallization, sublimation purification is performed, and further organic compounds are used or stored. In some cases, after passing through a vacuum state, it is replaced with a nitrogen atmosphere. Such an organic EL element by a coating method was produced under extremely strict management excluding the adverse effects as much as possible, and it was still difficult to exceed the performance of the vapor deposition method.

In the first place, the low productivity of vacuum deposition methods has an adverse effect on the size and mass productivity of organic EL elements, that is, the cost. If performed under such strict management, the productivity is lower than the vapor deposition method, and the cost is increased.

3. Compound purification method (sublimation purification)
The advantage of low molecular weight compounds is that more purification means can be used than high molecular weight compounds, resulting in high purity. 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 adopted for organic compounds for organic EL is mainly due to the fact that the manufacturing process of the organic EL element employs the 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 (Equation 1).

-ΔG = -ΔH + TΔS (Formula 1)
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 to 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 as follows.

When A is dissolved in a solvent called B which can dissolve A at a high temperature, 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 move freely in the solution, the entropy (ΔS) is extremely large. When this high temperature solution is cooled, TΔS applied with temperature T becomes smaller than before cooling. At that time, in order to keep the cast free energy (-ΔG) constant before and after cooling, the enthalpy (-ΔH) must be increased.

That is, as the temperature decreases and TΔS decreases, A must decrease the distance from A to increase the enthalpy. The extreme state is a crystal state in which the distance between A and A is minimum, 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, what should be noted is the interaction between the solute compound A and the solvent (2). Since the compound A as a solute is dissolved by being solvated with the solvent (2), 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.

In other words, this recrystallization method can be applied only when the interaction force between AA and the interaction force between AB can be finely adjusted. Therefore, a case-by-case approach that delicately controls the molecular structure of A and the interaction between A and B is necessary, and cannot be a purification method that can be performed under universal conditions. It is.

However, this method has been used in the chemical industry for a long time since mass purification of several hundred kg or more is possible at a time when the conditions are met.

(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 mobile phase B can be changed arbitrarily. 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 changed arbitrarily, the solute that can be purified has an extremely wide range of application, and it can be used as an almost universal 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.

In other words, 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.

The means to solve 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 used exclusively in 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 it is supercritical carbon dioxide that can have various polarities in this way, the polarity of supercritical carbon dioxide formed in the 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, and as a result, both analytical and preparative products are sold. Prices have fallen and have become quite popular. Due to these characteristics and circumstances, we have used this supercritical HPLC for the purification of organic EL materials that require high purity (see 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? Usually, the solvent molecule B surrounds the solute compound A with the interaction force between A and B, and the aggregate of A is separated so that B exists around A, that is, A is an isolated single molecule. 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 will cause a big problem later.

In other words, in the vapor deposition method, when forming a thin layer (film) such as a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, etc., the compounds constituting each layer are basically formed by vacuum deposition. Lands on the substrate or the organic functional layer in the state of vaporized isolated single molecule, and 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 energy level of HOMO or LUMO is not that of a single molecule, but that of a stacked aggregate (crystalline 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, it was analyzed by small-angle X-ray scattering measurement (also referred to as “small angle X-ray scattering:“ SAXS ”) to determine how much molecular dispersion the coating solution intended to be dissolved normally is. Consider based on the results.

FIG. 1 shows the particle size distribution of the fine particles of the compound constituting the thin film produced by the vapor deposition method, and the solid line shows the particle size distribution of the fine particle of the thin film constituting compound produced by the coating method. Since both use the same compound, they can be directly compared.

The half-value width of the maximum peak of the particle size distribution of the fine particles of the compound is a particle size close to monodispersion when the deposition film thickness is about 2 nm. This indicates that since the size is one or two molecules, an amorphous film is formed by randomly arranging almost single molecules.

On the other hand, the particle size distribution of the coating film is widely distributed to about 10 nm with the maximum peak being 5 nm.

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.

Even if this coating solution is stored in a glove box under a nitrogen atmosphere for more than one week, crystals do not precipitate, and it is a so-called clear solution. The dispersion is what we misunderstood 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 water molecule is encountered only once, the exciton reacts with water and becomes a compound different from the original molecule. Even if oxygen molecules are not so serious, some kind of oxidation reaction or oxidative coupling reaction occurs. This is the most typical phenomenon of deterioration accompanied by a chemical change.

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, and there is a risk of chemical changes there. There is. That is, water molecules and oxygen molecules should not be present at all in the coating solution, and that is the premise.

However, in the industry, high-purity anhydrous solvents are very expensive and difficult to handle. After all, in order to reduce the cost by the coating method, how versatile solvents can be used as consumables. Hold the key.

6). Elemental technology according to the present invention [Coating liquid for forming an organic film]
The coating solution for forming an organic film of the present invention is a coating solution for forming an organic film containing an organic compound as a solute and at least two solvents (1) and a solvent (2). The solvent (1) has a solubility of less than 5% by mass, the solvent (2) has a solubility of 5% by mass or more, and the content ratio of the solvent (2) is 1 to 1000 ppm by mass relative to the total amount of solvent. And the organic compound is dispersed as molecules or aggregates.

In the coating solution for forming an organic film of the present invention, the organic compound in the coating solution contains a solvent (2) that is a good solvent for the organic compound and a solvent (1) that is a poor solvent, and contains the solvent (2). It is presumed that the organic compound can be finely dispersed because it is a mixed solvent within the above range with a small ratio. For this reason, the organic film that is the coating film of this coating solution can be an amorphous organic film in which the organic compound is the same as the deposited film, and an organic film with good performance similar to the deposited film can be obtained. It is considered possible.

When the content ratio of the solvent (2) is less than 1 ppm by mass with respect to the total amount of the solvent, it is difficult to finely disperse the organic compound as a solute as a molecule or an aggregate in the coating solution for forming an organic film. . Moreover, when the content ratio of the solvent (2) exceeds 1000 mass ppm with respect to the total amount of the solvent, the solvent (2) which is a good solvent tends to remain in the organic film, and the life of the organic electronic device is prolonged. It becomes difficult. Preferably, the content ratio of the solvent (2) is in the range of 1 to 100 ppm by mass, and more preferably in the range of 1 to 10 ppm by mass with respect to the total amount of the solvent.

The dispersion state of the organic compound as a solute in the coating solution for forming an organic film can be measured by small angle X-ray scattering measurement. In the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of single molecules derived from the organic compound obtained from the small-angle X-ray scattering measurement or the aggregate thereof obtained from the coating liquid for forming an organic film, It is preferable to have the maximum maximum peak in a region having a particle size of 5 nm or less, and the half width thereof is in the range of 0.5 to 5.0 nm.

<Small angle X-ray scattering measurement>
For the small-angle X-ray scattering measurement of the coating solution for forming an organic 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, preferably a high energy accelerator. Large-scale synchrotron radiation facilities such as Synchrotron Radiation Research Facility (Photon Factory), SPring-8 (Super Photoring-8 GeV), Saga Kyushu Synchrotron Light Research Center (SAGA-LS), Aichi Synchrotron Light Center A small-angle X-ray scattering apparatus using can be used.

The measurement conditions are described below.

The coating solution for forming an organic film is put into a capillary for X-ray diffraction sample (WJM-Glas / Muller GmbH) and used as a measurement sample.

Using SPring-8 synchrotron radiation as an X-ray, the coating solution for forming an organic film is irradiated at a wavelength of 0.1 nm. For measurement, a HUBER multi-axis diffractometer is used, the X-ray incident angle θ is fixed at 0.2 °, and the organic film-forming coating solution is irradiated. The detector uses a scintillation counter to adjust 2θ to 1 to 43 °. Measurement of scattered radiation up to For analysis of the obtained small angle X-ray scattering data, a 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 the 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 the above formula (A1), “λ” represents the X-ray wavelength, 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 conducting particle analysis in small angle X-ray scattering, Guinier plot is generally used.

When the particle size distribution is relatively small and the interaction between particles is small in the coating solution for forming an organic film, the scattering intensity I (q) is represented 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, with respect to 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 single molecule derived from the organic compound in the coating film or the aggregate thereof were obtained.

For details of the small angle X-ray scattering method, for example, the X-ray diffraction handbook 3rd edition (issued in 2000 by Rigaku Corporation) can be referred to.
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 and half width)
In the coating solution for forming an organic film of the present invention, a particle size distribution curve of a single molecule derived from the organic compound or an aggregate thereof obtained from small angle X-ray scattering measurement (horizontal axis: particle size, vertical axis: frequency) Distribution) has a maximum maximum peak in a region having a particle size of 5 nm or less, and its half-value width is preferably in the range of 0.5 to 5.0 nm. When the maximum maximum peak and its full width at half maximum are within the above range, the organic compound is preferably dispersed more finely in the coating solution for forming an organic film.

Even in a coating solution for forming an organic film having a plurality of organic compounds as solutes, when at least one organic compound is finely dispersed in a monomolecular form, the particle size distribution curve has a particle size of 5 nm or less. A sharp maximum peak is measured, which is preferable in view of the effects of the present invention. The lower limit of the particle size of the maximum peak of the particle size distribution curve is about 1 nm although it depends on the molecular weight of the organic compound.

The half width represents the width (nm) of the particle size distribution curve at 1/2 the peak height of the maximum peak wavelength.

The lower limit of the full width at half maximum is about 0.5 nm although it depends on the association state of the organic compound.

FIG. 2 shows an example of the particle size distribution curve for the coating solution for forming an organic film of the present invention. The solid line is the particle size distribution curve of the coating liquid for forming an organic film of the present invention, and it can be seen that it has the maximum maximum peak in the region of particle size of 5 nm or less. It turns out that it is similar to the case of the particle size distribution curve in a vapor deposition film shown in FIG. On the other hand, the coating solution for forming an organic film dissolved only with a poor solvent has a wide half-value width, shows a broad particle size distribution curve, and the value of the particle size showing a maximum peak exceeds 5 nm. It can be seen that is not finely dispersed.

Further, the particle size distribution curve of the coating solution for forming an organic film of the present invention may have a plurality of maximum peaks, but has a maximum maximum peak in a region having a particle size of 5 nm or less, and its half-value width is If it is in the range of 0.5 to 5.0 nm, the effect of the present invention can be obtained.

(Organic compounds)
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 an organic compound used in various electronic devices from the viewpoint of manifesting the effects of the present invention.

For example, when the coating solution for forming an organic film of the present invention is a coating solution for producing an organic EL element, the organic compound is a material for organic electroluminescence (hereinafter also referred to as “organic EL material”). It is preferable that The organic EL material refers to a 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 organic compounds of organic EL materials used in the light emitting layer, hole transport layer, electron transport layer, hole injection layer, electron injection material, and the like will be described later.

Moreover, when the coating liquid for forming an organic film of the present invention is a coating liquid for producing a photoelectric conversion element, the organic compound may be an organic compound contained in the organic functional layer for the photoelectric conversion element. preferable. Examples of organic compounds used in organic functional layers such as a photoelectric conversion layer, a hole transport layer, an electron transport layer, an electron injection layer, a hole injection layer, a hole block layer, and an electron block layer will be described later.

In addition, in order to use the coating liquid for forming an organic film for the application of a coating liquid for producing an organic EL element or a photoelectric conversion element, from the viewpoint of preventing functional deterioration in the coating film, It is desirable not to contain impurities.

In addition, the organic compound used as the solute is preferably a low molecular compound having a molecular weight of 3000 or less from the viewpoint that many purification means can be utilized and it can be easily purified with high purity.

<Solvent>
The coating solution for forming an organic film of the present invention is a coating solution for forming an organic film containing an organic compound as a solute and at least two solvents (1) and a solvent (2). The solvent (1) has a solubility of less than 5% by mass, the solvent (2) has a solubility of 5% by mass or more, and the content ratio of the solvent (2) is 1 to 1000 ppm by mass relative to the total amount of solvent. Is within the range.

The solubility of the solvents (1) and (2) can be determined by a solubility test in which 5% by mass of a solute is added to the solvent, stirred at 20 ° C. for 10 minutes, and examined for the presence of insoluble matter. As a result of this test, if there is an insoluble matter, it is determined that the solvent is a poor solvent (1), and if it is not a good solvent (2). Whether the specific solvent for the organic compound is the solvent (1) or the solvent (2) can be appropriately selected based on the above determination. The solvent may be an inorganic solvent or an organic solvent.

Examples of the organic solvent according to the present invention include alcohols (methanol, ethanol, diol, triol, 2,2,3,3-tetrafluoro-1-propanol (TFPO), etc.), glycols, cellosolves, and ketones. (Acetone, methyl ethyl ketone, etc.), carboxylic acids (formic acid, acetic acid, etc.), carbonates (ethylene carbonate, propylene carbonate, etc.), esters (ethyl acetate, propyl acetate, etc.), ethers (isopropyl ether, THF, etc.), amides (Such as dimethyl sulfoxide), hydrocarbons (such as heptane), nitriles (such as acetonitrile), aromatics (such as cyclohexylbenzene, toluene, xylene, chlorobenzene), alkyl halides (such as methylene chloride), amines (1 , 4-Diazabicyclo [2 2.2] octane, diazabicycloundecene or the like) and the like, lactone-based.

Examples of the inorganic solvent according to the present invention include water (H ₂ O) and a molten salt. Molten salts that can be used as inorganic solvents include, for example, metal iodide-iodine combinations such as lithium iodide, sodium iodide, potassium iodide, cesium iodide, and calcium iodide; tetraalkylammonium iodide, pyridinium iodide Iodine, imidazolium iodide and other quaternary ammonium compound iodine salt-iodine combination; lithium bromide, sodium bromide, potassium bromide, cesium bromide, calcium bromide metal bromide-bromine combination; tetraalkyl Bromine-bromine combinations of quaternary ammonium compounds such as ammonium bromide, pyridinium bromide; metal complexes such as ferrocyanate-ferricyanate, ferrocene-ferricinium ion; sodium polysulfide, alkylthiol-a Sulfur compounds such as kill disulfide; viologen dyes, hydroquinone - such as quinones and the like.

As the solvent (1), although depending on the organic compound to be used, among the above, solvents having a boiling point in the range of 50 to 180 ° C., for example, esters and alcohols can be preferably used.

As the solvent (2), although depending on the organic compound to be used, among the above, for example, hydrocarbons having high solubility in the organic compound can be preferably used.

[Method for producing coating solution for forming organic film]
The method for producing a coating liquid for forming an organic film of the present invention comprises a solvent (1) and the solvent (2), and the content ratio of the solvent (2) is within the range of 1 to 1000 ppm by mass relative to the total amount of the solvent. It is preferable to have a dissolution step of preparing a solvent that is, and dissolving the organic compound in the prepared solvent to obtain a coating solution for forming an organic film.

In the dissolution step, the organic compound can be dissolved in the solvent (1) and the solvent (2) by a known dissolution method. The temperature at the time of mixing, stirring conditions, etc. can be selected suitably, and it can melt | dissolve.

However, this method requires a large amount of the solvent (1) which is a poor solvent for the organic compound at the time of dissolution. Therefore, a mixed solvent containing the solvent (1) and the solvent (2) using the chromatography method described below. A method of preparing a coating solution for forming an organic film having a composition according to the present invention by removing the solvent (2) from is preferable. In the chromatographic method, it is possible to reduce the total amount of the solvent by using a large amount of the good solvent (2).

(Chromatography method)
In the method for producing a coating liquid for forming an organic film of the present invention, after preparing a solution in which the organic compound is dissolved in a solvent (2), the solvent (1) is used as a mobile phase and the solution in which the organic compound is dissolved is used. Separation step of obtaining a coating solution for forming an organic film in which the content ratio of the solvent (2) is in the range of 1 to 1000 ppm by mass with respect to the total amount of the solvent by separating and removing the solvent (2) by chromatography. It is preferable to have.

As the separation step for removing the solvent (2) by chromatography from the solution in which the organic compound is dissolved, it is preferable to use high performance liquid chromatography, supercritical or subcritical chromatography, or gel permeation chromatography. Of these, from the viewpoint of being able to produce the coating solution for forming an organic film of the present invention with high purification efficiency, promoting further dispersion, and shortening the production time by increasing the speed, supercritical or subcritical It is particularly preferred to use a chromatographic method.

At this time, it is particularly preferable that the mobile phase contains supercritical carbon dioxide. Hereinafter, the supercritical or subcritical chromatography method will be described.

(Supercritical or subcritical chromatography method)
In the supercritical fluid chromatography method, a packed column, an open column, or a capillary column can be used.

(Chromatography column)
The chromatography column is not particularly limited as long as it has a separating agent capable of separating the target substance in the sample injected into the 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. 3, for example, a supercritical fluid 11 containing an organic solvent (including carbon dioxide), a pump 12, a modifier 13, an injector 14 for injecting an organic compound to be separated, An apparatus equipped with a separation column 15, a detector 17, a pressure regulating valve 18 and the like 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. A substance changes 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 and balance. 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, it is possible to change between the liquid and the gas 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 are high-density fluids having high kinetic energy, exhibiting liquid behavior in terms of dissolving solutes, and exhibiting gas characteristics in terms of density variability. Although there are various solvent properties of supercritical fluids, it is important to have low viscosity, high diffusivity, 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 a low viscosity. Solvent molecules can be uniformly dispersed because mass transfer and concentration equilibrium are fast and the density is high like a liquid.

The supercritical or subcritical fluid according to the present invention preferably has a critical point temperature of 300 ° C. or lower from the viewpoint of suppressing decomposition of the organic compound in the coating solution.

The supercritical or subcritical fluid according to the present invention is preferably a gas under the conditions of a temperature of 20 ° C. and a pressure of 101325 Pa (1 atm). As a result, the recovery of the supercritical or subcritical fluid in the coating film becomes rapid, and when the coating liquid is dried and solidified to form a coating film, the supercritical or subcritical fluid is not left. be able to.

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. Of these, carbon dioxide can be preferably used from the viewpoints of easily producing a fluid in a supercritical or subcritical state, having a low environmental load, high stability, and low cost.

The solvent used as the 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, 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, carboxylates such as formic acid, acetic acid and trifluoroacetic acid Acid solvents, nitrogen compound solvents such as acetonitrile, pyridine, N, N-dimethylformamide, sulfur compound solvents such as carbon disulfide and dimethyl sulfoxide, water, nitric acid, sulfuric acid, etc. That.

The operating temperature of the supercritical fluid or subcritical fluid is basically not particularly limited as long as it is equal to or higher than the temperature at which the organic compound used as the solute according to the present invention is dissolved, but the supercritical fluid or subcritical fluid and solute are combined. From the viewpoint of good mixing, the use temperature is preferably in the range of 20 to 600 ° C. according to these types.

The solvent used as the supercritical fluid or subcritical fluid may be the same as the solvent (2) which is a good solvent. The content ratio of the solvent (1) and the solvent (2) in the coating solution for forming an organic film after separating the solvent (2) may be within the range defined by the present invention.

The working pressure of the supercritical fluid or subcritical fluid is basically not limited as long as it is equal to or higher than the critical pressure of the substance to be used, but if the pressure is too low, the supercritical fluid of the organic compound used as the solute according to the present invention or The solubility in the subcritical fluid may be poor, and 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 is 1 to 100 MPa. It is preferable to be within the range.

A device using a supercritical fluid or subcritical fluid is not limited as long as the coating liquid according to the present invention is a device having a function of contacting the supercritical fluid or subcritical fluid and dissolving it in 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, and a combination of a batch method and a distribution method. It is possible to use a method or the like.

In the supercritical or subcritical chromatography method according to the present invention, after the sample is injected into the mobile phase, the peak of the target substance that is the slowest elution from the column is detected among the target substances, and then the next sample is prepared. It is preferable that the next sample injection be performed before tailing of the peak of the target substance that has been slow to elute from the column and has been delayed until the injection is completed.

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 a large amount of separation target compound is subjected to a fractionation operation, the composition of the mobile phase can be changed.

The step of changing the composition of the mobile phase is to change the composition of the mobile phase containing a supercritical or subcritical fluid and a solvent. By changing the composition of the mobile phase in this step, the peak tailing decay can be accelerated. In column-adsorbed supercritical fluid chromatography, the peak shows significant tailing particularly when a preparative operation for loading a relatively large amount of the 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.

In the present invention, changing the composition in the mobile phase produces the same effect as the step gradient method in liquid chromatography, and accelerates the peak component decay by promoting the extrusion of the peak component from the column. Yes.

Supercritical or subcritical chromatography uses a highly diffusive, low viscosity supercritical or subcritical fluid, so the flow rate of the mobile phase is large 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, the composition of the mobile phase can be changed by increasing the solvent ratio in the mobile phase.

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 or subcritical chromatography apparatus, the inner diameter of the column, the type of the target substance, the composition of the mobile phase, etc. Since it is necessary to inject a large amount of solvent, the loop piping included in the solvent injection device is larger than the loop piping included in 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 the same solvent as the solvent contained in the mobile phase or a different solvent, for example. Moreover, the solvent to be injected may be one kind or two or more kinds.

In particular, a highly polar solvent is preferable in terms of further speeding up the decay of tailing. 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 be measured by a peak detected by a detector, such as an ultraviolet absorption spectrometer, usually provided in supercritical fluid chromatography.

[Organic film]
The organic film of the present invention is a film formed by drying and solidifying the coating solution for forming an organic film of the present invention. The said coating film can be used suitably for the organic functional layer which comprises an organic EL element and a photoelectric conversion element.

The coating film manufacturing method includes a step of applying the organic film forming coating solution of the present invention and a step of drying the organic film forming coating solution. In the coating step, a known coating method can be used. However, from the viewpoint that a uniform film can be easily obtained even when the area is increased and the film can be formed at a low cost, for example, an inkjet method, an extrusion coating method, a spraying method. Examples thereof include a coating method and a spin coating method.

(Application process by inkjet application method)
As a coating method of the coating liquid for organic EL, it is preferable to apply using an inkjet coating method.

As an inkjet head used in the inkjet coating method, an on-demand system or a continuous system may be used. 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 the ink droplets ejected from the head is preferably in the range of 0.5 to 100 pL, and from the viewpoint of reducing coating unevenness and increasing the printing speed, it is in the range of 2 to 20 pL. More preferred. The volume of the ink droplet can be adjusted as appropriate by adjusting the applied voltage.

The print resolution is preferably set in the range of 180 to 10000 dpi (dots per inch), more preferably in the range of 360 to 2880 dpi, taking into account the wet layer thickness, the volume of ink droplets, and the like.

In the present invention, the wet layer thickness of the wet coating film at the time of inkjet coating (immediately after coating) 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. In the range of 1 to 5 μm, the effect of the present invention is more remarkably exhibited. The wet layer thickness can be calculated from the application area, printing resolution, and ink droplet volume.

Inkjet 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.

[Organic electronic devices]
As an organic electronic device provided with the organic film which is a coating film of the coating liquid for forming an organic film of the present invention, an organic EL element, a photoelectric conversion element and a solar cell can be preferably exemplified. Thus, the organic electronic device provided with the organic film of the present invention has characteristics excellent in durability and conversion efficiency. In an organic EL element, it is excellent in luminous efficiency, and in a photoelectric conversion element and a solar cell, it is excellent in photoelectric conversion efficiency.

[Organic EL device]
The organic EL device according to the present invention includes an organic film that is a coating film of the coating liquid for forming an organic film of the present invention as an organic functional layer, and a solute in the coating liquid for forming an organic film is a material for an organic EL element. It is.

Hereinafter, the organic EL element and the material for the organic EL element will be described.

The organic EL device of the present invention has an anode and a cathode and one or more organic functional layers sandwiched between these electrodes on a substrate.

The organic functional layer includes at least a light-emitting layer. In a broad sense, the light-emitting layer refers to a layer that emits light when an electric current is applied to an electrode composed of a cathode and an anode. It refers to a layer containing an organic compound that emits light when an electric current is passed through an electrode composed of 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 a structure sandwiched between the anode and the anode.

As a compound used as a material for an organic EL element, a known organic compound generally used for an organic functional layer such as a light emitting layer, a hole injection layer, a hole transport layer, an electron injection layer, and an electron transport layer is used. Can do.

Moreover, although the preferable specific example of the layer structure of the organic EL element which has on a board | substrate below is shown below, it is not limited to these.
(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 In addition, 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.

Hereinafter, the configuration of each layer of the substrate and the organic EL element will be described in detail.

(substrate)
The substrate that can be used in the organic EL device of the present invention (hereinafter also referred to as a base, a support substrate, a base material, a support, etc.) is not particularly limited, and a glass substrate, a plastic substrate, or 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.

Further, as a substrate, in order to prevent oxygen and water from entering from the substrate side, in a test based on JIS Z 0208, the thickness is 1 μm or more and the water vapor transmission rate is 1 g / (m ² · 24 hr) (25 ° C) or less is preferable.

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.

Plastic substrates have been attracting attention in recent years because they are highly flexible, lightweight and difficult to break, and can further reduce the 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, polyether imide, polyether ketone imide, polyamide, fluororesin, nylon, polymethyl methacrylate, acrylic or polyarylate, organic-inorganic hybrid resin, etc. . 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.

¡Plastic substrates that are normally produced have 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 “gas 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 gas 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) or less and a water vapor permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

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

In order to further 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 order of an inorganic layer and an organic functional layer, It is preferable to laminate | stack both alternately several times.

The gas barrier film has 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 gas barrier film is preferable, and the oxygen permeability measured by a method according to JIS K 7126-1987 is 1 × 10 ⁻³ mL / (m ² · 24 h · atm) or less, water vapor A high gas barrier film having a permeability of 1 × 10 ⁻⁵ g / (m ² · 24 h) or less is preferable.

The method for providing the gas barrier film on the resin film is not particularly limited, and any method may be used. For example, a vacuum deposition method, a sputtering method, a reactive sputtering method, a molecular beam epitaxy method, a cluster ion beam method, an ion plate method, and the like. For example, a coating method, a plasma polymerization method, an atmospheric pressure plasma 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 atmospheric pressure or near atmospheric pressure is preferable because 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 the light emission is taken out from the anode, it is desirable that the transmittance is larger than 10%. The sheet resistance as the anode is several hundred Ω / sq. The following is preferred. Furthermore, although the layer thickness of the anode depends on the material constituting it, it is usually selected within the range of 10 nm to 1 μm, preferably 10 to 200 nm.

(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.

(Organic EL element material used for light emitting layer)
There is no restriction | limiting in particular about the kind of organic EL element material used for this light emitting layer, A conventionally well-known thing can be used as a light emitting material in an organic EL element. 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 and the other components are called dopants. The mixing ratio of the dopant of the light emitting layer (hereinafter also referred to as the light emitting dopant) to the host compound is preferably 0.1 to less than 30% by mass.

The dopants used in the light emitting layer are roughly classified into two types: fluorescent dopants that emit fluorescence and phosphorescent dopants that emit 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.

The light emitting material used in the light emitting layer according to the present invention preferably 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. Vol. 123, pages 4304 to 4312, International Publication Nos. 00/70655, 01/93642, 02/02714, 02/15645, 02/44189, 02/081488, 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 , Special Table 2002-5 No. 0572, JP-A No. 2002-117978, No. 2002-338588, No. 2002-170684, No. 2002-352960, No. 2002-50483, No. 2002-100476, No. 2002 No. 173674, No. 2002-359082, No. 2002-17584, No. 2002-363552, No. 2002-184582, No. 2003-7469, No. 2002-525808, and Japanese Patent Laid-Open No. 2003. -7471, JP 2002-525833, JP 2003-31366, 2002-226495, 2002-234894, 2002-233506, 2002-241751, 2001 319779, JP same 2001-319780, JP same 2002-62824, JP same 2002-100474, JP same 2002-203679, JP same 2002-343572, JP same 2002-203678 Patent Publication.

Specific examples of the phosphorescent dopant are given below, but the present invention is not limited thereto.

Only one kind of light emitting dopant may be used, or plural kinds of light emitting dopants may be used. By simultaneously taking out 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 light emitting dopant is introduced into a polymer chain or the light emitting 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. 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 phosphorescence maximum wavelength derived from the 0 transition is 450 nm or less. As the host compound, a compound that has a hole transporting ability and an electron transporting ability, prevents the emission of light from being increased in wavelength, and has a high Tg (glass transition point) is preferable.

As a specific example of the host compound, 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, 2002-343568, 2002-141173, 2002-352957, 2002-203683, 2002-363227, 2002-231453, 2003-3165, 2002-234888, 2003-27048, 2002-255934, 2002-260861, 2002-280183, 2002-299060, 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.

The light emitting layer can be formed by using the above-mentioned material and reducing the film thickness by a known method such as a spin coating method, a casting method, an ink jet method, or a printing method.

(Hole injection layer and hole transport layer)
An organic EL element material (hereinafter also referred to as “hole injection material”) used for the hole injection layer has either a hole injection property or an electron barrier property. In addition, an organic EL element material (hereinafter also referred to as “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 (MTDATA) in which triphenylamine units described in No. 308688 are linked in three starburst types In addition, inorganic compounds such as p-type-Si and p-type-SiC can also be used as the hole injection material.

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.

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. 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 for organic EL elements used in this electron injection layer (hereinafter also referred to as “electron injection materials”) include heterocyclic rings such as nitro-substituted fluorene derivatives, diphenylquinone derivatives, thiopyran dioxide derivatives, naphthalene perylene, and the like. Examples include tetracarboxylic anhydride, carbodiimide, 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 a preferable material for an organic EL element used for the electron transport layer has a fluorescence maximum wavelength at 415 nm or less. That is, the organic EL element material used for the electron transport layer is preferably a compound that has an electron transport ability, prevents the emission of light from becoming longer, 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.

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 made of one or more of these electron injection materials, or may have a laminated structure made up of a plurality of layers having the same composition or different compositions.

In the present specification, when the ion injection 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), and examples thereof include International Publication No. 00/70655, Japanese Patent Laid-Open No. 2001-313178, Japanese Patent Laid-Open No. 11-204258, No. 11-204359 and “Organic EL devices and their industrialization front line (November 30, 1998, issued by NTS Corporation)”, 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 hole injection layer and between the cathode and the light emitting layer or electron injection layer. The buffer layer is a layer provided between the electrode and the organic functional layer in order to lower the driving voltage and improve the luminous efficiency. “The organic EL element and the forefront of its industrialization (November 30, 1998, NTS Corporation) Issue) ”, Chapter 2,“ Electrode Materials ”(pages 123 to 166), in detail, and includes an anode buffer layer and a cathode buffer layer.

The details of the anode buffer layer are described in JP-A-9-45479, JP-A-9-260062, JP-A-8-288069, and the like. As a specific example, a phthalocyanine buffer layer represented by copper phthalocyanine And an oxide buffer layer typified by vanadium oxide, 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, metals represented by strontium, aluminum and the like. Examples thereof include a buffer layer, 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 the cathode of the organic EL element, a metal having a low work function (less than 4 eV) (hereinafter referred to as an electron injecting metal), an alloy, a metal electrically conductive compound, or a mixture thereof is 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 injecting 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 functional layer by depositing 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 following is preferable, and the thickness is usually selected in 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 of manufacturing organic EL element]
As an example of the method for producing an 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, and an electron injection layer containing the above-described organic EL element material is sequentially formed thereon.

As a method for thinning these organic compound thin films, in the present invention, the coating method is particularly preferable in that the coating liquid for forming an organic film of the present invention can be used as the coating liquid.

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 the boat heating temperature is 50 to 450, the degree of vacuum is 10 ⁻⁶ to 10 ⁻² Pa, and the vapor deposition rate is 0.01. It is desirable to select appropriately within the range of ˜50 nm / second, the substrate temperature of −50 to 300 ° C., and the 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 may be produced in the middle and subjected to a different film formation method. 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.

In the case of patterning only the light emitting layer, the method is not limited, but is preferably a vapor deposition method, an inkjet method, or a printing method. In the case of using a vapor deposition method, patterning using a shadow mask is preferable.

It is also possible to reverse the production order to produce a cathode, an electron injection layer, an electron transport layer, a light emitting layer, a hole transport layer, a hole injection layer, and an 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 sources. In the display device and display, full-color display is possible by using three types of organic EL elements of red, green, and blue light emission.

Display devices and displays include televisions, personal computers, mobile devices, AV devices, teletext displays, information displays in automobiles, and the like. 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 according to 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 that directly recognizes a still image or a moving image. It may be used as a device (display). 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 including the organic EL element according to the present invention will be described below with reference to the drawings.

FIG. 4 is a schematic view showing an example of a display device composed of 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. 5 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. 5 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. 6 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.

6, an image data signal is applied to the drain of the switching transistor 61 from the control unit B (not shown in FIG. 6 but shown in FIG. 4) via the data line 56. When a scanning signal is applied from the control unit B to the gate of the switching transistor 61 through the scanning line 55, the driving of 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 the transmission of 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 as active elements for the organic EL elements 60 of the plurality of pixels, and a plurality of pixels 53 (not shown in FIG. 6). FIG. 5)) 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.

Further, 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 an organic EL element emits light according to a data signal only when a scanning signal is scanned.

FIG. 7 is a schematic view of a passive matrix display device. In FIG. 7, 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 a material for a photoelectric conversion element is used as the solute in the coating liquid for forming an organic film, the organic film that is the coating film of the coating liquid for forming an organic film is preferably used as an organic functional layer constituting the photoelectric conversion element. be able to.

Hereinafter, details of the photoelectric conversion element material, the photoelectric conversion element, and the solar cell will be described.

FIG. 8 is a cross-sectional view showing an example of a solar cell having a single configuration (a configuration in which the bulk heterojunction layer is one layer) composed of a bulk heterojunction type organic photoelectric conversion element.

In FIG. 8, 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 an electron transport layer) on one surface of a substrate 201. 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 does not simply donate or accept electrons like an electrode, but donates or accepts electrons by a photoreaction.

In FIG. 8, light incident from the transparent electrode 202 through the substrate 201 is absorbed by the electron acceptor or the 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.

In addition, if the magnitude of 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.

Although not shown in FIG. 8, other layers such as a hole blocking layer, an electron blocking layer, an electron injection layer, and a hole injection layer may be included.

Also, a tandem configuration (a configuration having a plurality of bulk heterojunction layers) in which such photoelectric conversion elements are stacked may be used for the purpose of further improving the sunlight utilization rate (photoelectric conversion efficiency).

FIG. 9 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 the material that can be used for the layer as described above include n-type semiconductor materials and p-type semiconductor materials described in paragraph numbers [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 application, it is preferable to perform heating in order to cause removal of residual solvent, moisture, and gas, and improvement of mobility and absorption of long wave by 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 part (bulk heterojunction layer) 204 may be configured as a single layer in which the electron acceptor and the 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 electrodes constituting the organic photoelectric conversion element will be described.

In the organic photoelectric conversion element, positive and negative charges generated in the bulk heterojunction layer are taken out from the transparent electrode and the counter electrode via the p-type organic semiconductor material and the n-type organic semiconductor material, respectively, and function as a battery. To do. 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 and JP2014-078742A 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 materials, for example, known anode materials described in JP2010-272619A and JP2014-078742A 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 JP 2010-272619 A and JP 2014-078742 A can be used.

Next, materials that constitute components other than the electrode and the bulk heterojunction layer will be described.

(Hole transport layer and electron block layer)
The organic photoelectric conversion element of the present invention has a hole transport layer / electron block layer in 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 a material for the photoelectric conversion element constituting the hole transport layer, for example, known materials described in JP 2010-272619 A and JP 2014-078742 A can be used.

(Electron transport layer, hole blocking layer)
The organic photoelectric conversion device of 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 in the middle of the bulk heterojunction layer and the counter electrode. Therefore, it is preferable to have these layers.

For the electron transport layer, for example, known materials described in JP 2010-272619 A and JP 2014-078742 A can be used. Further, the electron transport layer may be a hole blocking layer having a hole blocking function having a rectifying effect that prevents holes generated in the bulk heterojunction layer from flowing to the counter electrode side. Such an electron transport layer is also called a hole blocking layer, and it is preferable to use an electron transport layer having such a function. As a material for forming the hole blocking layer, for example, known materials described in JP2010-272619A and JP2014-078742A 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.

The transparent resin film that can be preferably used as the transparent substrate in the present invention is not particularly limited, and the material, shape, structure, thickness, and the like can be appropriately selected from known ones. For example, known materials described in JP2010-272619A and JP2014-078742A can be used.

(Optical function layer)
The organic photoelectric conversion element of the present invention may have various optical functional layers for the purpose of more efficient 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 otherwise indicated, "mass part" or "mass%" is represented.

<< Compounds used in Examples >>
The structures of the compounds used in the following examples are shown.

The following solvents were used. All solvents used were dehydrated in advance.

Ethyl acetate (Et acetate): manufactured by Kanto Chemical Co., Ltd. Special grade ethyl acetate n-propyl acetate (nPr acetate): manufactured by Kanto Chemical Co., Ltd. Special grade n-propyl acetate Isobutyl acetate (iBu acetate): Special grade produced by Kanto Chemical Co., Ltd. Isobutyl acetate Chlorobenzene: Kanto Chemical Co., Ltd., special grade chlorobenzene Toluene: Kanto Chemical Co., Ltd., special grade toluene Xylene: Kanto Chemical Co., Ltd., special grade m-xylene TFPO: Tokyo Chemical Industry Co., Ltd. 2,2,3,3 -Tetrafluoro-1-propanol [Example 1]
<< Preparation of coating solution for organic film formation >>
<Preparation of coating solution 1-1 for forming an organic film>
A stirrer and n-propyl acetate as a solvent (1) are placed in a 100 mL beaker, and the stirrer is heated to 85 ° C. with stirring. A-1 is 0.6% by mass as a host compound, and Ir is a luminescent dopant. -14 was added to a concentration of 0.2% by mass, and the stir bar was subsequently stirred to dissolve. After confirming dissolution visually, the stirring bar was stopped, the temperature was returned to room temperature (25 ° C.), and the mixture was left for 30 minutes.

<Preparation of organic film forming coating solutions 1-2 to 1-4>
In the same manner as in the preparation of the coating solution 1-1 for forming an organic film, using the solvent (1) and the solvent (2) listed in Table I, the concentration of the solvent (2) becomes the concentration shown in the table. Organic film forming coating solutions 1-2 to 1-4 were prepared so that A-1 and Ir-14 had the same concentration as the organic film forming coating solution 1-1.

<Preparation of organic film forming coating solution 1-5>
Using a solution prepared in the same manner as the coating solution 1-3 for forming an organic film, and using nPr acetate as a poor solvent (solvent (1)) as a developing solution under a nitrogen atmosphere (in the glove box), the following description Then, the eluate was concentrated under reduced pressure, so that the concentration of the solvent (2) and the concentrations of A-1 and Ir-14 were 0.6% by mass and 0.2% by mass, respectively. Thus, an organic film forming coating solution 1-5 was obtained. The concentration of the obtained solvent (2) was the concentration shown in Table I.

Column: Silica gel (Fuji Silysia Chemical)
<Preparation of organic film forming coating solution 1-6>
A stirrer and chlorobenzene as a solvent (2) were placed in a 100 mL beaker, and the stirrer was heated to 85 ° C. with stirring. A-1 was 0.6% by mass as a host compound, and Ir-14 was 0 as a dopant. The mixture was added to a concentration of 2% by mass, and the stirring bar was subsequently stirred to dissolve. After confirming dissolution visually, the stirring bar was stopped, the temperature was returned to room temperature (25 ° C.), and the mixture was left for 30 minutes.

Thereafter, as shown below, this solution was used as a mobile phase with nPr, which is a poor solvent (solvent (1)), and supercritical carbon dioxide, and a good solvent (solvent (2)) by supercritical chromatography. ) Is separated and removed with nPr acetate, which is a poor solvent (solvent (1)), so that the concentrations of A-1 and Ir-14 are 0.6% by mass and 0.2% by mass, respectively. Thus, an organic film forming coating solution 1-6 was obtained.

(Supercritical chromatography conditions)
Equipment: Prep15 (Nippon Waters)
Column: Torus 2-PIC (particle size 5 μm, inner diameter 10.0 mm × length 150 mm)
Mobile phase layer: carbon dioxide: acetic acid nPr = 93: 7
Mobile phase bed flow rate: 10 mL / min
Pressure: 18MPa
Temperature: 40 ° C
Detection: PDA (254 nm)
<Preparation of coating solutions 1-7 to 1-12 for forming an organic film>
In the preparation of the coating liquid 1-6 for forming an organic film, the kind of the host compound as the solute, the good solvent (solvent (2)), and the poor solvent (solvent (1)) are changed as shown in Table I to obtain an organic film Similar to the preparation of the coating solution for forming 1-6, the solvent (1) (poor solvent) shown in Table I from nPr acetate and supercritical carbon dioxide as the mobile phase was used, and the solvent ( 2) Solvent (1) (poor solvent) so that the concentrations of A-1 and Ir-14 are 0.6% by mass and 0.2% by mass, respectively, after separating and removing (good solvent) Thus, coating solutions 1-7 to 1-12 for forming an organic film were obtained.

<< Evaluation of coating solution for organic film formation >>
Each coating liquid was subjected to the following evaluations (1) and (2). These results are shown in Table I below.

(1) Small-angle X-ray scattering measurement and particle size distribution analysis For each of the organic film forming coating solutions 1-1 to 1-12, an X-ray diffraction sample capillary (manufactured by WJM-Glas / Muller GmbH) ) To obtain a measurement sample. For X-rays, SPring-8 synchrotron radiation was used to irradiate the coating solution sample with a wavelength of 0.1 nm 1 mm. 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 scatter 2θ from 1 to 43 °. Line measurements were taken. A particle size distribution curve was created from the obtained scattering diffraction data using the above-described analysis software.

Here, in FIG. 2, as a result of the particle size distribution curve, the particle size distribution curve of the organic film forming coating solution 1-8 of the present invention and the particle size of the organic film forming coating solution 1-1 of the comparative example are shown. Distribution curves are indicated by solid lines and broken lines, respectively. When the particle size has a maximum peak at 5 nm or less and the half width is in the range of 0.5 to 5.0 nm, the organic compound is considered to be finely dispersed in the coating solution.

Similarly, with respect to other coating solutions for forming an organic film, the particle size distribution curve was obtained, the particle size showing the maximum maximum peak and the half value width thereof were obtained, and are shown in Table I.

Each coating solution for forming an organic film had one peak maximum and was attributed to being derived from the host depending on the particle size range.

(2) Measurement of concentration of solvent (2) in coating solution for forming organic film The concentration of solvent (2) in the coating solution for forming an organic film was measured by gas chromatography. Specifically, the measurement was performed by an absolute calibration curve method using Porapack Type S GC Bulk Packing Material (Mesh 80-100) manufactured by Waters Corporation as a column packing material.

When separated by supercritical chromatography, the solvent (2) was efficiently removed and its concentration was in the range of 1-10 ppm. In Table I, it is indicated as “> 1 ppm”. In Table I, chromatography is abbreviated as “chromatography” in the column for preparing coating solutions.

Next, an organic EL element provided with an organic film, which is a coating film of the coating liquid for forming an organic film of the present invention, as an organic functional layer was produced by a coating method. In the following examples, an organic EL element is produced by a spin coating method. However, the present invention is not limited to this, for example, by other coating methods such as an ink jet method, a die coating method, and a flexographic printing method. An organic functional layer may be produced.

<< Production of organic EL element >>
<Preparation of organic EL element 1-1>
A first electrode layer (anode), a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, an electron injection layer, and a cathode are sequentially formed on the flexible film, and then sealed to form an organic EL. Element 1-1 was produced. In forming the light emitting layer, the coating solution for forming an organic film of the present invention was used.

(1.1) Production of gas barrier flexible film As a flexible film, a polyethylene naphthalate film (a film made by Teijin DuPont Co., Ltd., hereinafter abbreviated as PEN) on the entire surface on the side where the first electrode is formed. An inorganic gas barrier film made of SiOx is continuously formed to a thickness of 500 nm on a flexible film using an atmospheric pressure plasma discharge treatment apparatus having a configuration described in JP-A-2004-68143. A gas barrier flexible film having an oxygen permeability of 0.001 mL / (m ² · day · atm) or less and a water vapor permeability of 0.001 g / (m ² · day) or less was produced.

(1.2) Formation of first electrode layer 120 nm thick ITO (indium tin oxide) is formed by sputtering on the gas barrier flexible film produced as described above, and patterned by photolithography. 1st electrode layer (anode) was formed.

The pattern was such that the light emission area was 50 mm square.

(1.3) Formation of hole injection layer The patterned ITO substrate was ultrasonically cleaned with isopropyl alcohol, dried with dry nitrogen gas, and subjected to UV ozone cleaning for 5 minutes. A solution obtained by diluting poly (3,4-ethylenedioxythiophene) -polystyrene sulfonate (PEDOT / PSS, Bayer PAl 4083) to 70% with pure water on this substrate at 3000 rpm for 30 seconds. After film formation by spin coating, the film was dried at 200 ° C. for 1 hour to provide a hole injection layer having a layer thickness of 30 nm.

(1.4) Formation of hole transport layer This substrate was transferred to a nitrogen atmosphere using nitrogen gas (grade G1), and the compound (HT-1) (Mw = 80000) as a hole transport material was replaced with chlorobenzene. A solution dissolved in 0.5% was formed by spin coating at 1500 rpm for 30 seconds, and then kept at 160 ° C. for 30 minutes to form a hole transport layer having a layer thickness of 30 nm.

(1.5) Formation of Light-Emitting Layer A coating liquid 1-1 for forming an organic film as a host compound-containing composition was formed by spin coating at 1500 rpm for 30 seconds, and then held at 120 ° C. for 30 minutes. Each light emitting layer having a thickness of 40 nm was formed.

Incidentally, during the application, the coating liquid was applied with dry air while maintaining the environmental temperature at 40 ° C.

(1.6) Formation of Electron Transport Layer Subsequently, 20 mg of the compound (ET-1) was dissolved in 4 mL of 2,2,3,3-tetrafluoro-1-propanol (TFPO) at 1500 rpm, After forming the film by spin coating in 30 seconds, it was held at 120 ° C. for 30 minutes to form an electron transport layer having a layer thickness of 30 nm.

(1.7) Formation of electron injection layer and cathode Subsequently, the substrate was attached to a vacuum deposition apparatus without being exposed to the atmosphere. In addition, a molybdenum resistance heating boat containing sodium fluoride and potassium fluoride is attached to a vacuum evaporation system, and the vacuum chamber is depressurized to 4 × 10 ⁻⁵ Pa, and then the boat is energized and heated. A thin film having a layer thickness of 1.0 nm is formed on the electron transport layer at a rate of 0.02 nm / second with sodium fluoride, and then a layer thickness of 1.5 nm on the sodium fluoride at a rate of 0.02 nm / second in the same manner. The electron injection layer was formed.

Next, 100 nm of aluminum was vapor-deposited to form a cathode.

(1.8) Sealing Next, as a sealing member, a polyethylene terephthalate (PET) film (12 μm thickness) is bonded to a flexible aluminum foil (made by Toyo Aluminum Co., Ltd.) having a thickness of 30 μm for dry lamination. A laminate (adhesive layer thickness 1.5 μm) was prepared using an agent (two-component reaction type urethane adhesive).

Next, on the aluminum (cathode) surface, as a sealing adhesive, the following thermosetting adhesive is uniformly applied to the sealing surface (shiny surface) of the sealing member with a thickness of 20 μm using a dispenser. It was applied to. This was dried under a vacuum of 100 Pa or less for 12 hours. Further, it 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 was adjusted to 100 ppm or lower.

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 Next, the sealing member is closely attached and arranged so as to cover the joint portion of the extraction electrode and the electrode lead, and the thickening condition using the pressure roll, the pressure roll temperature 120 ° C., The organic EL element 1-1 was produced by tightly sealing at a pressure of 0.5 MPa and an apparatus speed of 0.3 m / min.

<Production of organic EL elements 1-2 to 1-12>
In the formation of the light emitting layer in the method for producing the organic EL element 1-1, the organic EL element was similarly prepared except that the organic film forming coating liquid 1-1 was changed to the organic film forming coating liquids 1-2 to 1-12. 1-2 to 1-12 were produced.

(Solubility test)
For each of the organic compounds A-1 to A-3, a 5% by mass solution is prepared using each solvent, and each solution is stirred for 10 minutes at 20 ° C. using a stir bar. The presence or absence was confirmed. As a result, it was confirmed that the solubility of nPr acetate, iBu acetate and Et acetate was less than 5% by mass, and the solubility of chlorobenzene, toluene and xylene was 5% by mass or more.

Similarly, a 5 mass% solution was prepared for each of the organic compounds Ir-14 using each solvent, and each solution was stirred for 10 minutes at 20 ° C. using a stirrer to visually check the insoluble matter. The presence or absence was confirmed. As a result, it was confirmed that the solubility of nPr acetate, iBu acetate and Et acetate was less than 5% by mass, and the solubility of chlorobenzene, toluene and xylene was 5% by mass or more.

<< Evaluation of organic EL elements >>
The following evaluations (1) to (3) were performed on the organic EL elements 1-1 to 1-12. These results are shown in Table I below.

(1) Evaluation of luminous efficiency Each of the organic EL devices produced above was allowed to emit light at room temperature (about 25 ° C.) under a constant current condition of ^2.5 mA / cm ² , and the emission luminance immediately after the start of emission was determined as spectral radiance. The total was measured using CS-2000 (manufactured by Konica Minolta).

Next, the relative light emission luminance was calculated with the light emission luminance of the organic EL element 1-1 of the comparative example as 100, and this was used as a measure of the light emission efficiency (external quantum yield). The larger the value, the better the luminous efficiency.

(2) Evaluation of continuous drive stability (light emission lifetime) Each organic EL element is wound around a cylinder having a radius of 5 cm, and then continuously driven in a state where each organic EL element is bent, and the above-mentioned spectral radiance meter CS-2000 is used. The luminance was measured, and the time (LT ₅₀ ) during which the measured luminance was reduced by half was determined. The driving condition was set to a current value of 4000 cd / m ² at the start of continuous driving.

In Table I below, the LT ₅₀ of the organic EL element 1-1 is set to “100”, and the LT ₅₀ of each of the other organic EL elements is shown as a relative value to this, and this is used as a measure of continuous drive stability. In Table I below, the larger the value, the better the continuous drive stability (long life).

(3) Evaluation of Mobility Production of Single Charge Device As shown below, a single charge device that flows only holes, a so-called hole-only device (HOD) was produced for confirmation of hole transportability.

<Production of HOD-1>
In the same manner as in the production of the organic EL element 1-1, after the electron transport layer was produced, an electron blocking layer was provided as follows instead of the electron injection layer.

The substrate on which the electron transport layer was formed was attached to a vacuum deposition apparatus. After depressurizing the vacuum chamber to 4 × 10 ⁻⁴ Pa, molybdenum oxide having a thickness of 10 nm was deposited as an electron blocking layer.

Finally, hole-only device HOD-1 was fabricated by depositing aluminum to form a cathode having a thickness of 100 nm.

<Production of HOD-2 to HOD-12>
Similarly to the production of HOD-1, for the organic EL elements 1-2 to 1-12, after producing the electron transport layer, an electron blocking layer and a cathode are formed instead of the electron injection layer to form HOD-2 to HOD. -12 was produced.

<Evaluation of single charge device>
When evaluating the obtained single charge devices HOD-1 to HOD-12, the aluminum electrode side of each device after fabrication was covered with a glass case, and a 300 μm thick glass substrate was used as a sealing substrate. An epoxy photo-curing adhesive (Lux Track LC0629B manufactured by Toagosei Co., Ltd.) is applied as a sealing material, and this is placed on the cathode so as to be in close contact with the transparent support substrate and irradiated with UV light from the glass substrate side. It was cured, sealed and evaluated.

(Measurement of current density)
The current-voltage characteristics were measured for each manufactured single charge device. The current density was calculated from the current value when 5 V was applied. For the measurement, a 6430 type sub-femtoamper remote source meter manufactured by KEITHLEY was used. In the table, the current density of HOD-1 of the device comparative example is shown as a relative value with 100, and this is used as a measure of mobility. In Table I, the corresponding organic EL element is shown as the mobility of HOD.

In the above evaluation of the single charge elements HOD-1 to HOD-12, no light emission was observed, and it was confirmed that the evaluation related to the movement of the single charge was performed.

The above results are shown in Table I.

As shown in Table I above, the organic EL device of the present invention had good results in luminous efficiency and luminous lifetime. On the other hand, the organic EL element of the comparative example was inferior in any item. This is considered to be because the organic compound contained in the light emitting layer is dispersed in an amorphous state, as can be seen from the high hole mobility of the organic film used in the organic EL device of the present invention. It is done.

Moreover, the organic EL element of the present invention has good light emission efficiency and light emission lifetime, and therefore can be suitably used for a display device and a lighting device.

[Example 2]
<< Production of organic photoelectric conversion element >>
<Preparation of organic photoelectric conversion element 2-1>
The transparent electrode patterned on the glass substrate was cleaned in the order of ultrasonic cleaning with surfactant and ultrapure water, followed by ultrasonic cleaning with ultrapure water, dried with nitrogen blow, and finally UV ozone cleaning. .

On this transparent substrate, Baytron P4083 (manufactured by Starck Vitec), which is a conductive polymer, was spin-coated at a thickness of 30 nm, and then dried by heating at 140 ° C. in the air for 10 minutes to form a hole transport layer. .

After this, the substrate was brought into the glove box and worked in a nitrogen atmosphere. First, the substrate was heat-treated at 140 ° C. for 3 minutes in a nitrogen atmosphere. A solution was prepared by dissolving 1.5 mass% of plexcores OS2100 manufactured by Plextronics as a p-type semiconductor material and 1.5 mass% of E100 (PCBM) manufactured by Frontier Carbon as an n-type semiconductor material in chlorobenzene. A bulk heterojunction layer was formed by spin-coating at 500 rpm for 60 seconds and then at 2200 rpm for 1 second while being filtered through a .45 μm filter and allowed to stand at room temperature (25 ° C.) for 30 minutes.

Next, as a hole blocking material B-1, a coating liquid for forming an organic film in which batocuproine (BCP) manufactured by Aldrich is mixed with 2,2,3,3-tetrafluoro-1-propanol at a ratio of 0.5% by mass. Spin coating was performed at 1500 rpm using 2-1 to form a 10 nm thick hole blocking layer.

Next, the substrate on which the series of organic functional layers was formed was placed in a vacuum deposition apparatus without being exposed to the atmosphere. The element was set so that the shadow mask with a width of 2 mm was orthogonal to the transparent electrode, and the inside of the vacuum deposition apparatus was depressurized to 10 ⁻³ Pa or less, and then 100 nm of Al was deposited. Finally, the heating for 30 minutes was performed at 120 degreeC, and the comparative organic photoelectric conversion element 1 was obtained. The vapor deposition rate was 2 nm / second, and the size was 2 mm square.

The obtained organic photoelectric conversion element 1 was sealed using an aluminum cap and a UV curable resin (manufactured by Nagase ChemteX Corporation, UV RESIN XNR5570-B1) in a nitrogen atmosphere, and then taken out into the atmosphere.

<Preparation of organic photoelectric conversion element 2-2>
In the production of the organic photoelectric conversion element 2-1, a 10 nm thick hole blocking layer was prepared using the organic film forming coating liquid 2-2 prepared as follows instead of the organic film forming coating liquid 2-1. An organic photoelectric conversion element 2-2 was produced in the same manner as the organic photoelectric conversion element 2-1, except that was formed.

<Preparation of organic film forming coating solution 2-2>
A stirrer and chlorobenzene as a solvent (2) are placed in a 100 mL beaker, and the stirrer is heated to 85 ° C. while stirring so that the concentration of B-1 as a hole blocking compound is 0.5% by mass. Then, the stirring bar was stirred and dissolved. After confirming dissolution visually, the stirring bar was stopped, the temperature was returned to room temperature (25 ° C.), and the mixture was left for 30 minutes.

Thereafter, as shown below, this solution was subjected to supercritical chromatography using TFPO, which is a poor solvent (solvent (1)), and supercritical carbon dioxide as a mobile phase, and a good solvent (solvent (2)). ), And then prepared with TFPO which is a poor solvent (solvent (1)) so that the concentration of B-1 is 0.5% by mass, and coating liquid 2-2 for forming an organic film Got.
The concentration of the solvent (2) in the organic film forming coating solution 2-2 was measured in the same manner as in Example 1, and the results are shown in Table II.

(Supercritical chromatography conditions)
Equipment: Prep15 (Nippon Waters)
Column: Torus 2-PIC (particle size 5 μm, inner diameter 10.0 mm × length 150 mm)
Mobile phase layer: carbon dioxide: TFPO = 93: 7
Mobile phase bed flow rate: 10 mL / min
Pressure: 18MPa
Temperature: 40 ° C
Detection: PDA (254 nm)
(Solubility test)
Prepare a 5% by mass solution for each of the organic compounds B-1 using each solvent, stir each solution for 10 minutes at 20 ° C. using a stirrer, and visually check for insolubles. did. As a result, it was confirmed that the solubility of TFPO was less than 5% by mass and the solubility of chlorobenzene was 5% by mass or more.

<< Evaluation of coating solution for organic film formation >>
With respect to the coating liquids 2-1 and 2-2 for forming the organic film prepared in the same manner as in Example 1, (1) small-angle X-ray scattering measurement and particle size distribution curve were obtained, and the particle size showing the maximum maximum peak was determined. The full width at half maximum was determined and shown in Table II.

<< Evaluation of organic photoelectric conversion element >>
About each organic photoelectric conversion element, conversion efficiency, a fill factor, and durability were evaluated, respectively.

(Evaluation of conversion efficiency and fill factor)
The organic photoelectric conversion element produced above is irradiated with light having an intensity of 100 mW / cm ^{2 from} a solar simulator (AM1.5G filter) manufactured by Spectrometer Co., Ltd., and a mask having an effective area of 4.0 mm ² is overlaid on the light receiving portion. , Short-circuit current density Jsc (mA / cm ² ), open circuit voltage Voc (V), and fill factor FF were measured at four light receiving portions formed on the same element, and the average value was obtained. Further, the photoelectric conversion efficiency η (%) was obtained from Jsc, Voc, and FF according to Equation 1.

Formula 1 Jsc (mA / cm ² ) × Voc (V) × FF = η (%)
In Table II, relative values were determined with the conversion efficiency and the curve factor of the organic photoelectric conversion element 2-1 of Comparative Example as 100, and this was used as a measure of the curve factor and the light emission efficiency. The larger the value, the better.

From the above, it can be seen that a highly efficient organic photoelectric conversion element can be produced using the coating liquid of the present invention.

(Durability evaluation)
Solar simulator (AM1.5G) light was irradiated at an irradiation intensity of 100 mW / cm ² , voltage-current characteristics were measured, and initial conversion efficiency was measured. Further, assuming that the initial conversion efficiency at this time is 100, the conversion efficiency after 100 hours of irradiation with 100 mW / cm ² irradiation intensity with the resistance connected between the anode and the cathode was evaluated, and the relative reduction efficiency was calculated. .

Formula 2 Relative reduction efficiency (%) = (1−conversion efficiency after exposure / conversion efficiency before exposure) × 100
The results are shown in Table II. In Table II, a relative value with the relative reduction rate of the organic photoelectric conversion element 2-1 of the comparative example as 100 was obtained, and this was used as a measure of durability. The larger the value, the better the durability.

From Table II, when the organic film, which is the coating film of the coating liquid for forming an organic film of the present invention, is applied to the hole blocking layer of the organic photoelectric conversion element, the curve factor is improved and the photoelectric conversion efficiency is high. I understand that. Further, it can be seen that the relative reduction efficiency indicating durability is lower than that of the comparative example, and the durability is high.

The coating solution for forming an organic film of the present invention has an organic compound finely dispersed, and an organic electronic device provided with the coating film has excellent durability and conversion efficiency, and is suitable for organic electroluminescence elements and organic photoelectric conversion elements. Can be applied.

DESCRIPTION OF SYMBOLS 11 Supercritical fluid 12 Pump 13 Modifier 14 Injector 15 Column 16 Column oven 17 Detector 18 Pressure control valve A Display part B Control part 41 Display 53 Pixel 55 Scan line 56 Data line 60 Organic EL element 61 Switching transistor 62 Drive transistor 63 Capacitor 67 Power line 200 Organic photoelectric conversion element 201 Substrate 202 Transparent electrode (anode)
203 Counter electrode (cathode)
204 Photoelectric conversion part of bulk heterojunction layer 205 Charge recombination layer (intermediate electrode)
206 Second photoelectric conversion unit 207 Hole transport layer 208 Electron transport layer (buffer layer)
209 First photoelectric conversion unit

Claims

An organic film-forming coating solution containing an organic compound as a solute and at least two solvents (1) and (2),
The solubility of the organic compound at 20 ° C. is less than 5% by mass in the solvent (1),
The solvent (2) is 5% by mass or more, the content ratio of the solvent (2) is in the range of 1 to 1000 ppm by mass with respect to the total amount of the solvent, and
A coating solution for forming an organic film, wherein the organic compound is dispersed as molecules or aggregates.
In the particle size distribution curve (horizontal axis: particle size, vertical axis: frequency distribution) of single molecules derived from the organic compound or their aggregates obtained from small angle X-ray scattering measurement for the coating solution for forming an organic film 2. The coating solution for forming an organic film according to claim 1, which has a maximum maximum peak in a region having a particle size of 5 nm or less and a half-value width in a range of 0.5 to 5.0 nm. .
An organic film, which is a coating film of the coating liquid for forming an organic film according to claim 1 or 2.
An organic electronic device comprising the organic film according to claim 3.
A method for producing an organic film forming coating solution for producing the organic film forming coating solution according to claim 1,
A solvent containing the solvent (1) and the solvent (2) and having a content ratio of the solvent (2) in the range of 1 to 1000 ppm by mass with respect to the total amount of the solvent is prepared. The manufacturing method of the coating liquid for organic film formation which has a melt | dissolution process which melt | dissolves the said organic compound and obtains the coating liquid for organic film formation.
A method for producing an organic film forming coating solution for producing the organic film forming coating solution according to claim 1,
After preparing a solution in which the organic compound is dissolved in the solvent (2), the solvent (1) is used as a mobile phase, and the solvent (2) is separated by chromatography from the solution in which the organic compound is dissolved. An organic film-forming coating solution comprising a separation step of obtaining a coating solution for forming an organic film having a content ratio of the solvent (2) in the range of 1 to 1000 ppm by mass with respect to the total amount of the solvent Manufacturing method.
The method for producing a coating liquid for forming an organic film according to claim 6, wherein the mobile phase contains supercritical carbon dioxide.