JP4352474B2 - Method for manufacturing organic electroluminescence display element - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to an organic electroluminescence display element.
[0002]
[Prior art]
Organic electroluminescence display elements (hereinafter referred to as EL display elements) are attracting attention as self-luminous display elements that are excellent in viewing angle and response speed and are thin and light.
In general, an EL display element has a transparent electrode for extracting fluorescence on the front surface and a metal electrode on the back surface, and has an organic light emitting layer (electroluminescence layer, hereinafter referred to as EL layer) therebetween. The EL layer is often composed of a plurality of thin films such as a hole injection layer, a hole transport layer, a light emitting layer, an electron transport layer, and an electron injection layer. In some cases, a dielectric layer is provided between the electrode and the EL layer. In any case, the EL display element is a laminate of a plurality of thin films, and a method for producing the EL display element is to form a transparent electrode, an EL layer, and a metal electrode on a transparent substrate in sequence by vapor deposition or sputtering. is there.
[0003]
In many cases, ITO (Indium Tin Oxide) is used as a transparent electrode for extracting light emission of EL, but it is necessary to heat at the time of film formation. Since the EL layer is an organic material and the interface between the layers is important, thermal deterioration and melting must be avoided. On the other hand, a metal (for example, aluminum) electrode can be formed while suppressing heating of the substrate. For this reason, a transparent electrode is first provided on a transparent substrate, and an EL layer and a metal electrode are usually laminated thereon.
[0004]
The thickness of the EL layer is as thin as 1500 mm or less even when laminated. Therefore, light from the outside easily passes through the EL layer. Since the EL layer and the metal electrode are stacked on a flat substrate, the metal electrode is also flat and has a mirror surface. Therefore, external light that has passed through the EL layer is mirror-reflected by the metal electrode and returned to the front surface. Therefore, the EL display element causes a reflection of an image like a mirror, and has a problem that display visibility is remarkably impaired.
[0005]
In order to solve the problem of image reflection due to specular reflection of the metal electrode, several methods are conceivable. One is to provide an antireflection film such as a scattering plate on the front surface of the EL display element to suppress the introduction of external light and image formation to the EL display element. One is to provide a polarizing plate and a wave plate on the front surface of the EL display element to confine the reflected light of the outside light in the EL display element. In either case, some kind of optical filter is provided on the front surface of the EL display element, and the loss of EL emission and display blur due to this are inevitable problems.
[0006]
The other is to change the metal electrode to a low reflectivity material. However, in this configuration, there is an EL light emission reflection loss at the back metal electrode, and there is a problem that the light use efficiency is deteriorated. In order to increase the use efficiency of light emission, it is necessary to reflect the EL light emission by the back metal electrode and take it out to the front. The other is that both electrodes sandwiching the EL layer are transparent electrodes, and a diffuse reflector is provided on the back surface of the EL display element. In this case, since there is a distance between the light emitting unit and the reflecting plate, there is a problem of parallax and color blurring occurs. Neither method is the best solution for the image reflection problem.
[0007]
In order to efficiently extract EL light emission as a display, it is necessary to reflect the light emitted from the back surface by a metal electrode and at the same time avoid reflection of an image. For this purpose, it is effective to reduce the flatness of the metal electrode to eliminate the mirror surface. As a result, it is possible to avoid reflection of the image without reducing the reflectance.
[0008]
Since it is desirable that the EL layer and the metal electrode are in complete contact with each other to inject electrons, the flatness of the metal electrode alone cannot be reduced. Similarly, in order to inject holes, the EL layer and the transparent electrode need to be in complete contact. Therefore, in order to reduce the flatness of the metal electrode, the flatness of the entire laminate of the transparent electrode, the EL layer, and the metal electrode must be lowered. To that end, the flatness of the base may be lowered.
[0009]
However, it does not mean that the flatness of the substrate should simply be lowered. For example, the surface of a frosted glass obtained by treating the glass surface with hydrofluoric acid may be too light scattered and display may be blurred. When an appropriate pattern is formed on the glass surface by photolithography, there is a problem in that the cross-sectional shape of the pattern has corners, and if it is laminated on this, the upper and lower electrodes are likely to be short-circuited or disconnected. It is necessary to control the shape of the surface in a simpler way. Although the embossing method of embossing on the substrate surface can be considered, there is a problem that the equipment investment is expensive because a high-accuracy embossing plate and a pressing device are required to perform accurately with a large area.
[0010]
[Problems to be solved by the invention]
The present invention has been devised in view of the above problems, and an object of the present invention is to provide an EL display element that prevents reflection of an image due to specular reflection of a metal electrode and has high luminous efficiency.
[0011]
[Means for Solving the Problems]
In order to solve the above problems in the present invention, first, in claim 1, an organic electroluminescence display element comprising a plurality of anode electrodes, an organic electroluminescence layer and a cathode electrode laminated in this order on a transparent substrate. In the method, at least
(A) applying a photosensitive resin solution on a transparent substrate;
(B) drying the photosensitive resin solution to form a photosensitive resin film;
(C) on the photosensitive resin film, using a photomask in which dot-like patterns are randomly distributed in position, and exposing,
(D) heating the photosensitive resin film after exposure without developing it to cure the photosensitive resin film, and forming a dot-shaped uneven resin film on the transparent substrate;
(E) forming a transparent electrode, an EL layer, and a metal electrode in this order on the concavo-convex resin film;
It is set as the manufacturing method of the organic electroluminescent display element characterized by including these.
[0012]
2. The organic electroluminescence display element according to claim 1, wherein the dot-shaped irregularities are formed by a gentle curved surface having a dot diameter of 10 μm or less and a height of 500 mm or more . This is a manufacturing method .
[0013]
Furthermore, in Claim 3, the said dot-shaped unevenness | corrugation is formed by pattern-exposing and heat-hardening the photosensitive resin film on the said transparent substrate, The Claim 1 or 2 characterized by the above-mentioned. This is a method for manufacturing an organic electroluminescence display element .
[0014]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described.
As a result of intensive studies on a method for preventing the reflection of an image due to specular reflection of metal, the inventors of the present invention formed gentle irregularities in the form of dots on a transparent substrate to form a transparent electrode, an EL layer, and a metal electrode. It was found that the reflection of the image due to specular reflection can be prevented. Specifically, when forming a transparent electrode, an EL layer, and a metal electrode by forming randomly arranged dot-like irregularities composed of gentle curved surfaces having a dot diameter of 10 μm or less and a height of 500 mm or more Image reflection due to specular reflection of the metal electrode can be prevented.
[0015]
Specifically, first, a photosensitive resin solution is applied on the transparent substrate 201 and dried at a predetermined temperature to form a photosensitive resin film. Here, a quartz substrate, a glass substrate, a plastic substrate, etc. can be used as a transparent substrate. The physical properties of the photosensitive resin film are required to be transparent in addition to chemical stability and thermal stability. The application method of the photosensitive resin solution includes a spin coating method, a roll coating method, and a printing method, and may be appropriately selected according to the photosensitive resin solution to be used.
[0016]
Next, it exposes using the photomask which has a predetermined dot pattern on the photosensitive resin film. Here, the photomask is a pattern in which dot-like patterns are randomly distributed. The dot pattern diameter may be 10 μm or less, but is appropriately set according to the photosensitive resin used.
[0017]
Next, the exposed substrate is heated in an oven at a predetermined temperature, and the exposed photosensitive resin film is cured to form a dot-shaped uneven resin film 202 on the transparent substrate 201 (see FIG. 1). The heating condition may be a condition that the resin film is sufficiently cured.
When heated, the unexposed part becomes lower than the exposed part, and as a result, gentle irregularities of dots corresponding to the dot pattern are formed. The reason why the relative height difference occurs between the exposed portion and the unexposed portion is considered that the reaction of the photosensitive member proceeds in the exposed portion, but there are many unreacted substances in the unexposed portion, and this is evaporated by heating. The cross-sectional shape of the irregularities by this method is constituted by a sinusoidal continuous curve according to scanning electron microscope observation. The uneven step can be controlled to some extent by increasing the film thickness or increasing the amount of exposure, but can be generally controlled at 50 to 1 μm.
[0018]
Next, a transparent electrode 203 made of ITO is formed on the dot-shaped uneven resin film 202, and an EL layer (204, 205) and a metal electrode 206 are formed to produce the organic electroluminescence display element of the present invention ( (See FIG. 1).
Here, as the transparent electrode, ITO, IZO (Indium Zinc Oxide), Aluminum Zinc Oxide, or the like can be used.
As the EL layer, 9,10-diarylanthracene derivative, salicylate, pyrene, coronene, perylene, rubrene, tetraphenylbutadiene, 9,10-bis (phenylethynyl) anthracene, 8-quinolinolatolithium, tris (8- Quinolinolate) Aluminum complex (hereinafter abbreviated as Alq), N, N′-diphenyl-N, N′-bis (3-methylphenyl) -benzidine (hereinafter abbreviated as TPD), Tris (5,7-dichloro, 8-quinolinolate) ) Aluminum complex, tris (5-chloro-8quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (5-fluoro-8-quinolinolato) aluminum complex, tris (4-methyl-5-trifluoromethyl-) 8-quinolinolato) aluminum complex, (4-methyl-5-cyano-8-quinolinolato) aluminum complex, bis [8- (palatosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene , Poly-2,5-diheptyloxy-P-phenylene vinylene, or fluorescent substances and N, N ′ diaryl substituted pyrrolopyrrole compounds mentioned in JP-A-4-31488, US Pat. Nos. 5,141,671 and 4,769,292 However, it is not particularly limited to the above example. As the metal electrode, MgAg, AlLi, CuLi or the like can be used in addition to aluminum.
[0019]
【Example】
Hereinafter, the present invention will be described in detail by way of examples.
First, 390 g of epoxy resin (YDPN-601: manufactured by Tohto Kasei Co., Ltd.) and 108 g of acrylic acid were dissolved in 750 g of 1,6-hexanediol acrylate, and in the presence of 0.5 g of hydroquinone and 3 g of methylethylammonium iodide. It was made to react at 100-150 degreeC for 2 hours. Subsequently, 279 g of anhydrous head acid was added and reacted at 100 to 150 ° C. for 2 hours to obtain a water-soluble photopolymerizable oligomer.
[0020]
Next, 100 parts by weight of the obtained water-soluble photopolymerizable oligomer, 40 parts by weight of a phenol novolac type epoxy resin (YDCN-602: manufactured by Toto Kasei Co., Ltd.) as a water-insoluble photopolymerizable oligomer, as a photopolymerizable monomer 20 parts by weight of trimethylolpropane triacrylate (TMP-A: manufactured by Kyoeisha Yushi Co., Ltd.), 5 parts by weight of Irgacure-651 (manufactured by Ciba Geigy) as a photopolymerization initiator, and diphenyliodonium hexafluoroantimony as a photocuring catalyst precursor A negative photosensitive resin solution was obtained by mixing 0.5 parts by weight of Nate and 0.1 parts by weight of hydroquinone as a polymerization inhibitor in 1000 parts by weight of butyl cellosolve.
[0021]
Next, the negative photosensitive resin solution was applied onto the glass substrate 201 by spin coating, and dried at 70 ° C. for 30 minutes to form a photosensitive resin film having a thickness of 1.6 μm. Using a photomask on which a dot pattern with a diameter of 8 μm is randomly arranged on one surface, the photosensitive resin film is exposed at an exposure amount of 50 mJ / cm 2 and heated at 150 ° C. for 1 hour to form a dot-shaped uneven resin film 202. Formed. When the surface of the dot-like uneven resin film 202 was observed with a scanning electron microscope, a dot-like gentle unevenness with a height of 2000 mm was formed.
[0022]
Next, 2000 mm of ITO film was formed on the dot-shaped uneven resin film 202 by a sputtering method, and a patterned transparent electrode 203 was formed by patterning by a predetermined photolithography method. When the surface of the transparent electrode 203 was observed with a scanning electron microscope, gentle uneven dots were formed reflecting the shape of the base.
[0023]
Next, an EL layer of a hole transport layer 204 made of TPD and an electron transport light-emitting layer 205 made of Alq is formed on the transparent electrode 203 by vapor deposition, and a metal electrode 206 made of an aluminum film is further formed. The entire display element was sealed with a resin to obtain an EL display element of the present invention.
[0024]
When the obtained EL display element was viewed from the transparent electrode side, no reflection of an image due to specular reflection of the metal electrode was observed. When power was applied, no short circuit or disconnection of the electrode due to unevenness was observed.
[0025]
【The invention's effect】
As described above, the EL display element of the present invention forms gentle irregularities in the form of random dots on a transparent substrate to form a transparent electrode, an EL layer, and a metal electrode. Therefore, it is possible to obtain an EL display element with excellent light emission efficiency and display quality.
In addition, since the dot-shaped gentle irregularities can be formed by exposure and heat curing of the dot pattern in which the photosensitive resin film is randomly arranged, the size and shape of the dot-shaped irregularities can be easily controlled, resulting in the mirror surface of the metal electrode The effect of preventing reflection of an image due to reflection can be optimized.
Furthermore, since the dot-like irregularities can be formed by pattern exposure and heat treatment of the photosensitive resin film, the development process is not required and can be formed by a simpler process.
[Brief description of the drawings]
FIG. 1 is a schematic partial cross-sectional view showing one embodiment of an organic electroluminescence display element of the present invention.
[Explanation of symbols]
201 …… Transparent substrate 202 …… Dotted uneven resin film 203 …… Transparent electrode 204 …… Hole transport layer 205 …… Electron injection light emitting layer 206 …… Metal electrode

Claims (3)

In the method for producing an organic electroluminescence display element comprising a plurality of anode electrodes, an organic electroluminescence layer and a cathode electrode laminated in this order on a transparent substrate,
(A) applying a photosensitive resin solution on a transparent substrate;
(B) drying the photosensitive resin solution to form a photosensitive resin film;
(C) on the photosensitive resin film, using a photomask in which dot-like patterns are randomly distributed in position, and exposing,
(D) heating the photosensitive resin film after exposure without developing it to cure the photosensitive resin film, and forming a dot-shaped uneven resin film on the transparent substrate;
(E) forming a transparent electrode, an EL layer, and a metal electrode in this order on the concavo-convex resin film;
The manufacturing method of the organic electroluminescent display element characterized by including.   2. The method of manufacturing an organic electroluminescence display element according to claim 1, wherein the dot-shaped unevenness is formed by a gentle curved surface having a dot diameter of 10 μm or less and a height of 500 mm or more.   3. The method of manufacturing an organic electroluminescence display element according to claim 1, wherein the dot-shaped irregularities are formed by pattern exposure and heat curing of the photosensitive resin film on the transparent substrate.

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