JP2003115393A - Organic electroluminescence element and its manufacturing method, image display equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reducing wiring resistance in a positive electrode and to prevent aggravation of transmittance. SOLUTION: It is an organic electroluminescence element, which is constituted with at least a 1st electrode, an organic light emitting layer, and a 2nd electrode, which are laminated one by one on a substrate of optical permeable nature. The 1st electrode is constituted with a multilayer film, which is especially constituted with the multilayer film, which consists of a transparent electric conduction film and a metal film. Each film, which constitutes the multilayer film, is formed by the sputtering method. At the time of forming each the film by sputtering, all the films that constitute the multilayer films are carried out patterning using the same metal mask.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electroluminescence element (hereinafter referred to as an organic EL element), a manufacturing method thereof, and an image display device using the organic EL element.

[0002]

2. Description of the Related Art In general, an organic EL device has a transparent electrode layer on a transparent substrate having a light transmitting property, an organic light emitting layer formed of an organic EL material on the transparent electrode layer, and further on the organic light emitting layer. It is constituted as a basic constituent element with the metal electrode layer formed on the substrate, and is attracting attention as a self-luminous display element. In this organic EL element, by energizing the transparent electrode layer and the metal electrode layer, holes and electrons injected from the respective electrodes are recombined in the organic light emitting layer, and the energy at this time causes a light emitting phenomenon. . Since the light emission phenomenon is injection light emission similar to that of a light emitting diode, the light emission voltage is low at 10 V or less.

[0003]

By the way, in the image display device using the organic EL element, the wiring width of the electrode becomes smaller as the pixel becomes smaller, and as a result, in the transparent electrode layer (anode) having a particularly high resistance. There is a problem that the wiring resistance increases dramatically, a potential drop occurs with respect to the product of currents, and a large voltage is applied to the wiring itself. When a large voltage is applied to the wiring itself, an effective voltage is not applied to the organic EL element itself by that much, resulting in a loss of power consumption.

Therefore, for the purpose of suppressing the increase of the wiring resistance, a method of connecting an auxiliary electrode as disclosed in Japanese Patent No. 3162407, and Japanese Patent Laid-Open No. 2000-910.
A method of forming a light-transmitting portion and a non-light-emitting area that is not the light-transmitting portion as disclosed in Japanese Patent Publication No. 83 has been developed. However, in these methods, since it is necessary to dispose the wiring portion in a portion other than the light emitting pixel, it is not possible to dispose the light emitting pixel in the entire panel, and there is a new problem that the entire brightness is reduced. Occur. Further, since the patterns of the transparent electrode layer and the wiring portion are different, there is a problem that the manufacturing process becomes complicated.

The present invention has been proposed in view of such conventional circumstances, and an organic electroluminescence device capable of reducing the resistance of the electrode arranged on the display side of the organic light emitting layer and at the same time ensuring the light transmittance. And its manufacturing method. Another object of the present invention is to provide an image display device capable of efficiently arranging light emitting pixels and increasing brightness, and further to provide an image display device capable of simplifying a manufacturing process. The purpose is to

[0006]

In order to achieve the above-mentioned object, the organic electroluminescent device of the present invention comprises:
At least a first electrode, an organic light emitting layer on a light-transmissive substrate,
In the organic electroluminescent element in which the second electrode is sequentially laminated, the first electrode is composed of a multilayer film, particularly a multilayer film composed of a transparent conductive film and a metal film.

The first electrode disposed on the display side of the organic light emitting layer is usually a transparent electrode made of indium tin oxide (ITO) or the like. In that case, the wiring resistance is high and the loss of power consumption becomes a problem. Become. Further, if the first electrode is formed of only a metal film having a low wiring resistance, it becomes difficult to secure the light transmittance, which hinders display. In the organic electroluminescence element of the present invention, the first electrode arranged on the display side of the organic light emitting layer is a multilayer film of a transparent conductive film and a metal film, so that the wiring resistance is suppressed and the transmittance is reduced at the same time. Can also be suppressed.

The method for manufacturing an organic electroluminescent element according to the present invention is the method for manufacturing an organic electroluminescent element, wherein at least a first electrode, an organic light emitting layer and a second electrode are sequentially laminated on a light-transmissive substrate. The first electrode is a multi-layer film, and each film forming the multi-layer film is formed by a sputtering method.
Furthermore, when each film is formed by the sputtering method, patterning is performed using a metal mask.

When a multilayer film such as a transparent conductive film or a metal film is formed by a sputtering method, a dense film is formed. As a result, the film has a low electric resistance value. Further, if the film is dense, it is also advantageous in terms of light transmittance, and a decrease in transmittance can be suppressed. Further, when the respective films are formed by the sputtering method, if the patterning using the metal mask is adopted, all the films constituting the multilayer film can be patterned by using the same metal mask, and the manufacturing process is improved. It is simplified.

Further, in the image display device of the present invention, organic electroluminescent elements in which at least a first electrode, an organic light emitting layer and a second electrode are sequentially laminated on a light-transmissive substrate are arranged in a matrix. The first electrode of each organic electroluminescence element is composed of a multilayer film, particularly a multilayer film composed of a transparent conductive film and a metal film.

In the image display device of the present invention, the first electrode arranged on the display side of the organic light emitting layer is a multilayer film of a transparent conductive film and a metal film, so that the wiring resistance can be suppressed and the transmittance can be reduced. Since it is also suppressed, it is not necessary to connect an auxiliary electrode or provide a non-light emitting area. Therefore, the light emitting elements can be efficiently arranged, and the brightness of the panel can be increased. Further, since the wiring of the pattern different from the original electrode pattern is unnecessary, the manufacturing process is not complicated.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, an organic electroluminescence device to which the present invention is applied, a method for manufacturing the same, and an image display device will be described.

As shown in FIG. 1, the organic electroluminescence element includes an anode 2 corresponding to a first electrode, an organic EL layer 3 including an organic light emitting layer made of an organic EL material, on a substrate 1 having light transparency. The cathode 4 corresponding to the second electrode is laminated and formed, and the surface thereof is covered with a protective layer 5. The organic EL layer 3 has a three-layer structure in this example, and is arranged on the side in contact with the anode 2, the hole transport layer 3a, the organic light emitting layer 3b, and the cathode 4. It is composed of an electron transport layer 3c. In the above structure, for example, LiO may be formed between the organic EL layer 3 and the cathode 4 with a film thickness of about several angstroms. With this layer, the light emission start voltage can be lowered.

Here, the present invention is characterized in that the anode 2 is a multilayer film composed of a transparent conductive film and a metal film. For example, as shown in FIG. 2, the transparent conductive layer 2a, It is a three-layer film including a metal layer 2b and a transparent conductive layer 2c. Of course, the present invention is not limited to this, and may be, for example, a two-layer film, or a four-layer film or more. As described above, the anode 2 is usually a transparent electrode made of indium tin oxide (ITO) or the like, but in that case, the wiring resistance is high and the loss of power consumption becomes a problem. Further, if the anode 2 is formed of only a metal film having a low wiring resistance,
It becomes difficult to secure the light transmittance, which hinders display. If the anode 2 arranged on the display side of the organic EL layer 3 is a multilayer film including the transparent conductive layers 2a and 2c and the metal layer 2b as described above, the wiring resistance can be suppressed and the transmittance can be reduced. The decrease can be suppressed.

Of the multi-layered film forming the anode 2, it is preferable to use a material having a resistivity as small as possible for the metal film. Examples of such a material include Au, Ag and A.
l, Cu, Ni, Co, Fe, Mo, Nb, Pd, Pt
Etc. can be mentioned. These may be used alone, or an alloy composed of two or more kinds may be used. On the other hand, the transparent conductive film, particularly the transparent conductive film joined to the organic EL layer 3, is preferably made of an electrode material having a large work function from the vacuum level in order to efficiently inject holes. It is desirable to use a material having light transmissivity so that organic electroluminescence in the organic EL layer 3 can be taken out from the anode 2 side. From these viewpoints, specifically, indium tin oxide (ITO), indium oxide-zinc oxide (so-called IXO), SnO ₂ , Zn
O and the like can be mentioned. The IXO is composed of a hexagonal layered compound composed of an oxide of indium and zinc and indium oxide, and has the general formula In ₂ O ₃ (Zn
O) _n (n is an integer of 3 or more). Of these, ITO is preferably used from the viewpoint of productivity and controllability.

In the multilayer film used for the anode 2, it is important to design the film thickness of the metal film and the transparent conductive film which compose the multilayer film. For example, if the ratio of the thickness of the metal film to the total thickness of the multilayer film is large, the wiring resistance can be reduced, but the transmittance is significantly reduced, which hinders display. On the other hand, if the ratio of the film thickness of the metal film becomes too small, the wiring resistance will increase although there is no problem in terms of transmittance. From this viewpoint, when the thickness of the entire multilayer film (anode 2) is 85 nm to 100 nm, the thickness of the metal film is 1
The thickness is preferably 0 nm to 15 nm.

The above-mentioned multilayer film can be formed by forming a metal film or a transparent conductive film by a sputtering method. The film formed by the sputtering method is dense, has low electric resistance, and has excellent light transmittance. The metal film and the transparent conductive film forming the multilayer film can all be formed using the same metal mask, and the manufacturing process is not complicated.

On the other hand, as the constituent elements other than the anode 2, any known one can be adopted. For example, the material used for the substrate 1 may be any material as long as it can form a substrate having good flatness and has a light transmitting property. For example, a polymer material is used. be able to. Of course, a glass substrate may be used, but in particular, a flexible polymer EL substrate can be used to construct a flexible organic EL display.

Of the organic EL layer 3, the hole transport layer 3a is
It plays a role of transporting holes injected from the anode 2 to the organic light emitting layer 3b. This hole transport layer 3a
As the hole transport material used in, any known material can be used, benzine, styrylamine, triphenylamine, porphyrin, triazole, imidazole, oxadiazole, polyarylalkane, phenylenediamine, arylamine, Oxazole, anthracene, fluorenone, hydrazone, stilbene,
Alternatively, derivatives thereof, and heterocyclic conjugated monomers, oligomers, polymers and the like such as polysilane compounds, vinylcarbazole compounds, thiophene compounds and aniline compounds can be used. Specific compounds include α-naphthylphenyldiamine, porphyrin, metal tetraphenylporphyrin, metal naphthalocyanine, 4,4,4-tris (3-methylphenylphenylamino) triphenylamine, N, N, N, N- Tetrakis (p-tolyl) p-phenylenediamine, N, N,
N, N-tetraphenyl 4,4-diaminobiphenyl,
Examples thereof include N-phenylcarbazole, 4-di-p-tolylaminostilbene, poly (paraphenylenevinylene), poly (thiophenvinylene), poly (2,2-thienylpyrrole), but are not limited thereto. Not something.

The material used for the organic light-emitting layer 3b is capable of injecting holes from the anode side and electrons from the cathode side when a voltage is applied, and moves the injected charges, that is, holes and electrons, so that these holes and Any material may be used so long as it can provide a field where electrons can be recombined, high luminous efficiency, and the like. For example, an organic material such as a low-molecular fluorescent dye, a fluorescent polymer, or a metal complex. Etc. Specific examples of such a material include anthracene, naphthalene, phenanthrene, pyrene, chrysene, perylene, butadiene, coumarin, acridine, stilbene, tris (8-quinolinolato) aluminum complex, and bis (benzoquinolinolato) beryllium complex. , Tri (dibenzoylmethyl) phenanthroline europium complex, ditoluylvinylbiphenyl, α-naphthylphenyldiamine, and the like.

The electron transport layer 3c transports electrons injected from the cathode 4 to the organic light emitting layer 3b. Examples of the electron transport material that can be used for the electron transport layer 3c include quinoline, perylene, bisstyryl, pyrazine, and derivatives thereof. Specific compounds include 8-hydroxyquinoline aluminum, anthracene, naphthalene, phenanthrene, pyrene, chrysene,
Examples thereof include perylene, butadiene, coumarin, acridine, stilbene, (8-quinolinolato) aluminum complex and derivatives thereof.

In order to efficiently inject electrons, the cathode 4 is preferably made of an electrode material (metal) having a small work function from the vacuum level. Specifically, a metal having a low work function such as aluminum, indium, magnesium, silver, calcium, barium, or lithium is used alone. Alternatively, these metals may be used as alloys with other metals with increased stability.

Hole transport layer 3 constituting the organic EL layer 3
The a, the organic light emitting layer 3b, the electron transport layer 3c, and the cathode 4 can be formed by, for example, a vacuum vapor deposition method. At this time, as in the case of the multilayer film forming the anode 2, the film can be formed into a predetermined pattern by using a metal mask.

The protective layer 5 is provided to ensure the driving reliability of the organic EL element and prevent the deterioration of the organic EL element. The protective layer 5 seals the organic EL element and blocks oxygen and moisture. It has a function to do. Therefore, the material used for the protective layer 5 needs to be capable of maintaining hermeticity, and specific examples thereof include silicon oxide, silicon nitride, aluminum oxide, and aluminum nitride.

Image display is possible by arranging the organic EL elements having the above structure in a matrix on the substrate and selectively driving them, and a self-luminous image display device is constructed. In this image display device, the anode that constitutes each organic EL element is a multilayer film of a transparent conductive film and a metal film, so that the wiring resistance is suppressed, and at the same time, the reduction of the transmittance is also suppressed. There is no need to connect electrodes or provide non-light emitting areas. Therefore, the light emitting elements can be efficiently arranged, and the brightness of the panel can be increased. In addition, since the wiring having a pattern different from the original electrode pattern is unnecessary, the manufacturing process does not become complicated.

[0026]

EXAMPLES Specific examples of the present invention will be described below based on experimental results.

[0027]Fabrication of organic EL device The structure of the manufactured organic EL device is as shown in FIGS.
It is Ri. First, 200 μm thick polyester sulfo
Substrate (PES) is prepared and an anode is formed on it.
A multi-layer film using a metal mask by sputtering
did.

Next, an organic EL layer was formed on the above-mentioned anode multilayer film. The organic EL layer includes a hole transport layer, an organic light emitting layer,
The electron transport layer was formed by laminating in this order. At the time of stacking, a metal mask for forming a pattern was used and the film was formed by a vacuum deposition method. Here, 4,4,4-tris (3-methylphenylphenylamino) triphenylamine (m-MTDATA) was used for the hole transport layer. Further, α-naphthylphenyldiamine (α-NPD) was used for the organic light emitting layer. The electron transport layer contains tris (8-quinolinolato) aluminum complex (Alq3).
Was used. The thickness of the organic EL layer was 150 nm.

A cathode was formed on the organic EL layer formed as described above. Similarly to the organic EL layer, the cathode was formed by a vacuum evaporation method using a metal mask. Finally, a thickness of SiN 1 is formed so as to cover each layer formed as described above.
A protective layer of 000 nm was formed. The protective layer is reactive DC
It was formed by sputtering.

[0030]Optical thin film simulation (1) In the organic EL device having the above structure, the constitution of the anode,
Various samples were prepared by changing the film thickness. These sun
About pull, green by optical thin film simulation
The transmittance for light was examined. The results are shown in FIGS.
Note that FIG. 3 shows that when the film thickness of the metal film (Au) is 10 nm,
FIG. 4 shows the case where the film thickness of the metal film (Au) is 15 nm, and FIG.
This is the case where the film thickness of the metal film (Au) is 20 nm.

The transmittance of the green light at the central wavelength (520 nm) is, for example, in the case of only the metal film (Au 15 nm only).
It is 64.4%, whereas it is 75.8% in the case of a three-layer multilayer film, and it can be seen that the transmittance can be increased by about 11%. In the case of a multilayer film, 3
When the two-layer multilayer film is used instead of the two-layer multilayer film, the transmittance is increased, but the three-layer multilayer film is more effective.

[0032]Optical characteristics and wiring resistance FIG. 6 shows the optical characteristics of the actually formed anode. Note that the figure
In the figure, the broken line is the solid line when the ITO (150 nm) single layer is used.
Is ITO (42 nm) + Au (15 nm) + ITO (4
2 shows characteristics when a three-layer multilayer film composed of 2 nm) is formed.

When ITO is deposited at room temperature, the transmittance at the central wavelength of green light (520 nm) is 80.0%, whereas the transmittance when a three-layer multilayer film including a metal film is It was 75.3%, and the decrease in transmittance was about 5%. When a 8 cm × 154 μm striped wiring pattern was prepared, the wiring resistance was 23.3 kΩ when the ITO single layer was used, whereas the wiring resistance was 3.2 kΩ when the three-layer multilayer film was used. The wiring resistance could be reduced to about 1/7.

[0034]Optical thin film simulation (2) In the organic EL device having the above structure, the constitution of the anode,
Various samples were prepared by changing the film thickness. Different from the previous example
It is the material of the metal film that is APC (Ag,
A mixture of Pd and Cu) was used. For these samples
The green light by an optical thin film simulation.
The transmittance was measured. The results are shown in FIGS. Note that the figure
7 is a metal film (APC) having a film thickness of 10 nm, FIG.
When the film thickness of the metal film (APC) is 15 nm, FIG.
This is the case where the film thickness of the film (APC) is 20 nm.

As is clear from these figures, even when the metal film is made of APC, the transmittance can be increased due to the multilayer structure.

[0036]

As is apparent from the above description, according to the organic electroluminescence device of the present invention, the first electrode arranged on the display side of the organic light emitting layer is the multilayer film of the transparent conductive film and the metal film. Therefore, the wiring resistance can be suppressed, and at the same time, the reduction of the light transmittance can be suppressed.
Further, according to the manufacturing method of the present invention, a dense film (first electrode) can be formed, and it is possible to form an electrode having low wiring resistance and excellent light transmittance. Further, if patterning using a metal mask is adopted, the manufacturing process will not be complicated.

Further, according to the image display device of the present invention,
Since the first electrode arranged on the display side of the organic light emitting layer of each organic EL element is a multilayer film of a transparent conductive film and a metal film, the wiring resistance is suppressed, and at the same time, the decrease in transmittance is also suppressed. It is not necessary to connect auxiliary electrodes or provide non-light emitting areas. Therefore, the light emitting elements can be efficiently arranged, and the brightness of the panel can be increased. Also,
Since the wiring of the pattern different from the original electrode pattern is unnecessary, the manufacturing process is not complicated.

[Brief description of drawings]

FIG. 1 is a cross-sectional view schematically showing a configuration example of an organic EL element.

FIG. 2 is a cross-sectional view schematically showing a configuration example of an anode.

FIG. 3 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram in the case of Au 10 nm.

FIG. 4 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram in the case of Au 15 nm.

FIG. 5 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram when Au is 20 nm.

FIG. 6 is a characteristic diagram showing optical characteristics of an actually formed anode.

FIG. 7 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram when APC is 10 nm.

FIG. 8 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram when APC is 15 nm.

FIG. 9 is a characteristic diagram showing an optical thin film simulation result, and is a characteristic diagram when APC is 20 nm.

[Explanation of symbols]

1 substrate, 2 anode, 2a, 2c transparent conductive layer, 2b
Metal layer, 3 organic EL layer, 3a hole transport layer, 3b organic light emitting layer, 3c electron transport layer, 4 cathode, 5 protective layer

Claims (15)

[Claims] 1. An organic electroluminescence device comprising at least a first electrode, an organic light emitting layer, and a second electrode sequentially laminated on a light-transmissive substrate, wherein the first electrode is a multilayer film. And an organic electroluminescent device. 2. The organic electroluminescence device according to claim 1, wherein the multilayer film is composed of a transparent conductive film and a metal film. 3. The organic electroluminescence device according to claim 2, wherein the multilayer film is a three-layer film in which a transparent conductive film, a metal film, and a transparent conductive film are laminated in this order. 4. The metal film is made of Au, Ag, Al, C
3. The organic electroluminescence device according to claim 2, comprising at least one selected from u, Ni, Co, Fe, Mo, Nb, Pd and Pt. 5. The transparent conductive film is indium tin oxide,
Indium oxide-zinc oxide, indium oxide, tin oxide,
The organic electroluminescence device according to claim 2, comprising at least one selected from zinc oxide. 6. The organic electroluminescence device according to claim 1, wherein the light transmissive substrate is made of a polymer material and has flexibility. 7. A method of manufacturing an organic electroluminescence device, comprising: a light-transmissive substrate, and at least a first electrode, an organic light-emitting layer, and a second electrode, which are sequentially laminated on each other. A method for manufacturing an organic electroluminescence device, characterized in that each of the constituent films is formed by a sputtering method. 8. The method of manufacturing an organic electroluminescence device according to claim 7, wherein when forming each film by the sputtering method, patterning is performed using a metal mask. 9. The method for manufacturing an organic electroluminescence device according to claim 7, wherein the organic light emitting layer and the second electrode are formed by a vacuum vapor deposition method. 10. An organic electroluminescent element, which is formed by sequentially stacking at least a first electrode, an organic light emitting layer, and a second electrode on a transparent substrate, and is arranged in a matrix. An image display device, wherein one electrode is a multilayer film. 11. The image display device according to claim 10, wherein the multilayer film includes a transparent conductive film and a metal film. 12. The multilayer film is a transparent conductive film, a metal film,
The image display device according to claim 11, wherein the image display device is a three-layer film in which transparent conductive films are laminated in this order. 13. The metal film is made of Au, Ag, Al, C.
The image display device according to claim 11, comprising at least one selected from u, Ni, Co, Fe, Mo, Nb, Pd, and Pt. 14. The image display device according to claim 11, wherein the transparent conductive film is made of at least one selected from indium tin oxide, indium oxide-zinc oxide, indium oxide, tin oxide, and zinc oxide. . 15. The image display device according to claim 10, wherein the light transmissive substrate is made of a polymer material and has flexibility.