JP2014060104A - Organic el element and method for manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide: an organic EL element having no luminous unevenness by forming an organic light emitting layer and a light emitting auxiliary layer in a light emitting pixel part surrounded by a partition wall using a wet film forming method and an organic light emitting medium layer high in flatness with no film thickness difference, uniform and high in accuracy within the light emitting pixel part; and a method for manufacturing the organic EL element.SOLUTION: An organic EL element comprises light emitting pixel parts surrounded by a partition wall between a first electrode formed in a pattern shape on a substrate and a patterned second electrode provided to face the first electrode, and two-dimensionally arranged. Each light emitting pixel part comprises an organic light emitting layer and a light emitting auxiliary layer, and is formed by dissolving or dispersing an organic light emitting material and a light emitting auxiliary material into a solvent and using a wet film formation method. When a film thickness of the partition wall is denoted as A and the film thickness of an organic light emitting medium layer is denoted as B, a relation of 5≤film thickness A/film thickness B≤100 is satisfied.

Description

  The present invention relates to an organic electroluminescence element (hereinafter abbreviated as an organic EL element) expected to be used for a display such as an information display terminal, and a method for producing the same.

  An organic electroluminescence display (hereinafter abbreviated as an organic EL display) includes at least an anode, an organic light emitting layer, and a cathode on a substrate, and emits light by injecting electrons and holes into the organic light emitting layer by applying an electric field between the electrodes. It consists of an organic EL element to be made.

  Since the organic EL element is a self-luminous element, it can be displayed without using a backlight like a liquid crystal display. In addition, since the element structure is simple, a thin and lightweight element can be manufactured, and active research is currently underway. A general organic EL element may include not only an organic light emitting layer but also a light emission auxiliary layer between an anode and a cathode. Examples of the light emission auxiliary layer include a hole transport layer, a hole injection layer, an electron transport layer, and an electron injection layer.

  Organic light-emitting materials used for the organic light-emitting layer of organic EL elements include low-molecular materials and high-molecular materials, and low-molecular materials are generally formed into thin films by vacuum film-forming methods (dry coating methods) such as vapor deposition. . However, when a full-color organic EL display is manufactured, for example, in the case of organic EL elements having three different colors of light emission such as R (red), G (green), and B (blue), the organic light emitting layer is a pixel. It is necessary to form a pattern every time. When patterning the organic light emitting layer by a vacuum film forming method, a vapor deposition mask having a fine pattern is used. In the method of patterning using a vapor deposition mask, there is a problem that it is difficult to obtain patterning accuracy as the substrate becomes larger. In addition, since it is a dry coating method, there is a problem that foreign matter and protrusions on the surface of the substrate cannot be sufficiently covered, and a short circuit is likely to occur. Moreover, the same problem arises also about light emission auxiliary layers other than an organic light emitting layer.

  Therefore, an attempt has been made to form an ink (coating liquid) by dissolving or dispersing an organic light emitting material in a solvent and forming a film by a wet coating method such as a coating method or a printing method. By using the wet coating method, it is possible to form a thin film uniformly and at high speed. In particular, in a manufacturing process using a large substrate, it is possible to reduce the cost of mass-produced products.

  The structure of the organic EL element using the coating type organic light emitting material is generally a structure in which anode / light emitting auxiliary layer / organic light emitting layer / cathode is laminated in this order. It can be produced by a wet coating method. Examples of wet coating methods for forming thin films include slit coating, spin coating, bar coating, dip coating, discharge coating, roll coating, and other coating methods, letterpress printing, ink jet printing, and intaglio printing. There are printing methods.

  In particular, selective film formation by the printing method is effective for coating the organic light-emitting layer so as to have three different emission colors of R (red), G (green), and B (blue) for each pixel. It is a manufacturing method.

Among various printing methods, a method using a hard printing plate such as a gravure printing method is not suitable for an organic EL element having a glass substrate. Further, in offset printing using a rubber blanket having elasticity, the rubber blanket is easily swelled by an aromatic solvent that is a solvent of the organic light emitting material, so that it is difficult to stably print with high accuracy. On the other hand, the relief printing method using a resin plate does not swell the plate seen in offset printing, and the resin has elasticity,
Printing on a glass substrate is also possible. Therefore, the relief printing method is most suitable as a method for producing an organic EL element.

  In the organic EL element produced by the relief printing method, as shown in Patent Document 1, a pixel partition that divides adjacent pixels is provided. Usually, the pixel partition is patterned by a photolithography method using a photosensitive resin. Providing a pixel partition has effects such as accurate segmentation of the pixel area and prevention of color mixing between adjacent pixels, prevention of leakage current, and reduction of irregularities such as TFT circuits and electrode lines. A protective effect for a driving element such as a provided thin film transistor can also be expected.

  The film thickness of the pixel partition contributes to the film thickness of the organic light emitting layer formed by the relief printing method and the shape within the pixel. When the film formation shape of the organic light emitting layer is deteriorated, a difference in film thickness occurs in the pixel, which causes a problem of uneven emission luminance.

  In order for the organic EL element to emit light efficiently, the film thickness of the organic light emitting layer is important, and it is necessary to form a thin film of about 0.1 μm. Therefore, it is necessary to design a partition wall thickness for forming the organic light emitting layer in a desired film thickness by the relief printing method and flattening the film formation shape.

Japanese Patent Laid-Open No. 2001-155858

  The problem to solve the above problem is that the organic light emitting layer and the light emitting auxiliary layer are formed in the light emitting pixel portion surrounded by the partition wall by a wet film forming method, and the light emitting pixel has high flatness and no film thickness difference. It is to provide an organic EL device having a uniform and highly accurate organic light-emitting layer and free from light emission unevenness, and a method for manufacturing the same.

As means for solving the above-mentioned problems, the invention described in claim 1 includes a first electrode formed in a pattern on a substrate, and a second electrode provided so as to face the first electrode. An organic EL element provided with a light emitting pixel portion surrounded by a partition wall and arranged in a two-dimensional manner,
The light emitting pixel portion is composed of an organic light emitting medium layer composed of an organic light emitting layer and a light emission auxiliary layer,
The organic light emitting layer and the light emitting auxiliary layer are formed by dissolving or dispersing the organic light emitting material and the light emitting auxiliary material in a solvent and formed by a wet film forming method.
The organic EL element is characterized in that the thickness of the partition wall is A and the thickness of the organic light emitting medium layer is B, and 5 ≦ film thickness A / film thickness B ≦ 100 is satisfied.

  According to a second aspect of the present invention, the partition wall thickness is 0.5 μm ≦ film thickness A ≦ 4.0 μm, and the organic light emitting medium layer thickness is B ≦ 0.2 μm. It is an organic EL element of Claim 1 characterized by the above-mentioned.

Further, in the invention according to claim 3, the partition is formed in a horizontal direction and a vertical direction with respect to a film forming direction of a wet film forming method for forming an organic light emitting medium layer,
The film thickness of the organic light emitting medium layer is defined as film thickness B, and the film thickness of the partition provided in the direction parallel to the film forming direction of the wet film forming method for forming the organic light emitting medium layer is defined as film thickness C. The organic EL element according to claim 1, wherein ≦ film thickness C / film thickness B ≦ 100 is satisfied.

  According to a fourth aspect of the present invention, the thickness of the partition provided in a direction parallel to the film forming direction of the wet film forming method for forming the organic light emitting medium layer is 0.5 μm ≦ film thickness C ≦ 4. It is 0.0 micrometer, It is an organic EL element as described in any one of Claims 1-3 characterized by the above-mentioned.

  The invention according to claim 5 is the organic EL element according to any one of claims 1 to 4, wherein the wet film-forming method for forming the organic light emitting medium layer is a relief printing method. It is.

  The invention according to claim 6 is formed by dissolving or dispersing the organic light emitting medium layer of the organic EL element according to any one of claims 1 to 4 in a solvent of an organic light emitting material and a light emitting auxiliary material. The method of manufacturing an organic EL element is characterized in that the wet film forming method is a relief printing method.

  According to the present invention, when the organic light emitting layer and the light emission auxiliary layer are formed on the substrate using a wet film forming method, the partition wall thickness of the light emitting pixel portion formed on the patterned first electrode and the organic By optimizing the film thickness of the light emitting layer and the light emitting auxiliary layer, or by optimizing the film thickness of the pixel partition, the organic light emitting layer, and the light emitting auxiliary layer arranged in parallel to the film forming direction, The flatness of the organic light emitting medium layer shape in the pixel is improved. Therefore, the light emission luminance uniformity within the pixel is improved, and an organic EL element without light emission unevenness can be manufactured.

  In addition, since the film formation shape at a desired organic light emitting medium layer film thickness can be controlled by the film thickness of the pixel partition wall, the members necessary for film formation are particularly determined for each desired organic light emitting medium layer film thickness in the relief printing method. Since it is not necessary to prepare, the cost can be reduced.

It is a cross-sectional schematic diagram for demonstrating the schematic structure of the organic EL element of this invention. It is an example of the top view which shows the shape at the time of forming an organic light emitting layer in the organic EL element pixel partition in embodiment of this invention. It is an example of the schematic diagram after organic EL element pixel partition formation in embodiment of this invention. It is an example of the schematic diagram after organic EL element pixel partition formation in embodiment of this invention. It is an example of the schematic diagram after organic EL element pixel partition formation in embodiment of this invention. It is a conceptual diagram of the relief printing machine for forming an organic light emitting layer and a light emission auxiliary layer in the pixel partition wall of the present invention. It is an example of the top view which shows the shape at the time of forming an organic light emitting layer in the pixel partition in the comparative example of this invention. It is an example of the top view which shows the shape at the time of forming an organic light emitting layer in the pixel partition in the comparative example of this invention.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. However, the present invention is not limited to this.

FIG. 1 is a schematic cross-sectional view for explaining an example of a schematic structure of the organic EL element of the present invention. On a substrate 101, a first electrode 102 serving as an anode, a hole transport layer 104, an organic light emitting layer 105, and a second electrode 106 serving as a cathode are provided. Thus, the structure in which the organic light emitting layer 105 is provided between the anode 102 and the cathode 106 and the light emission auxiliary layer 104 for transporting holes between the anode 102 and the organic light emitting layer 105 is provided is an organic EL element light emitting unit. This is a typical structure. Also, the anode 102
A pixel partition wall 103 is provided between the patterns to partition the light emitting pixels and to electrically insulate the pixels. In the organic EL structure in which the anode 102, the partition wall 103, the light emission auxiliary layer 104 for transporting holes, the organic light emitting layer 105, and the cathode 106 are provided on the substrate 101, the electrode and the organic light emitting layer 105 are further removed from the external environment. It is covered with a sealing body 107 for protection. The sealing body 107 includes a sealing cap 107a, an adhesive 107b, and a desiccant 107c.

  In the organic EL device of the present invention, a light emission auxiliary layer 104 is provided in addition to the organic light emitting layer 05 between the anode and the cathode. Examples of the light emission auxiliary layer 104 include a hole injection layer, an electron transport layer, an electron injection layer, and the like in addition to the above-described hole transport layer shown in FIG. These light emission auxiliary layers 104 are appropriately selected, and a plurality of them may be selected. The hole injection layer is provided between the anode and the organic light emitting layer. The electron injection layer and the electron transport layer which are the light emission auxiliary layer 104 are provided between the organic light emitting layer 105 and the cathode. In the organic EL device of the present invention, the positive hole transport layer that is the anode, the cathode, the organic light emitting layer 105, and the light emission auxiliary layer 104 may have a multilayer structure instead of a single layer structure.

  In the organic EL element of the present invention, the image driving method as an organic EL display can be applied to either a passive matrix method or an active matrix method. The passive matrix method is a method in which stripe-shaped anodes and cathodes are opposed to each other so as to be orthogonal to each other, and light is emitted at the intersection. On the other hand, the active matrix method is a so-called TFT substrate in which a thin film transistor (TFT) is formed for each pixel. By using this, light is emitted independently for each pixel. In the case of an active matrix type organic EL display, one of the anode and cathode of the organic EL element is provided for each pixel on the TFT substrate, and the other electrode is provided for the entire pixel.

  In addition, the organic EL device of the present invention is roughly classified into two types according to the method of extracting light for display. The bottom emission method for extracting emitted light from the substrate side and the emitted light from the side opposite to the substrate are extracted. Any of the top emission methods is possible. In the case of a bottom emission type organic EL element, the substrate 101 and the first electrode (anode) 102 need to have light transmittance, and in order to obtain a top emission type organic EL element, a cathode and a sealing element are required. The body needs to be light transmissive.

  In the organic EL device of the present invention, contrary to FIG. 1, a first electrode serving as a cathode, an organic light emitting layer 105, a hole transport layer, and a second electrode 106 serving as an anode are provided in this order on a substrate. Also good. When the organic light emitting layer 105 and the light emission auxiliary layer 104 such as a hole transport layer are collectively called an organic light emitting layer, in any case, the first electrode 102, the organic light emitting layer, and the second electrode 106 are formed on the substrate. Cross sections are formed in order, and pixel partitioning on a plane is performed by a separately manufactured pixel partition wall.

  Next, a method for manufacturing the organic EL element of the present invention shown in FIG. 1 will be described. However, the present invention is not limited to these.

  As the substrate 101 according to the present invention, any substrate can be used as long as it is an insulating substrate. However, in the case of the bottom emission method in which light is emitted from the substrate side, it is necessary to use a transparent substrate.

For example, a glass substrate or a quartz substrate can be used as the transparent substrate 101 described above. Further, it may be a plastic film or sheet such as polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate. By using a plastic film or sheet laminated with a metal oxide thin film, metal fluoride thin film, metal nitride thin film, metal oxynitride thin film, or polymer resin film as a substrate, moisture or gas Transmission can be reduced and the characteristics of the element can be stabilized.

  Examples of the metal oxide thin film include silicon oxide and aluminum oxide. Examples of the metal fluoride thin film include aluminum fluoride and magnesium fluoride. Examples of the metal nitride thin film include silicon nitride and aluminum nitride. Examples of the polymer resin film include acrylic resin, epoxy resin, silicon resin, and polyester resin.

  In the case of the top emission method, a coating using an opaque substrate can be performed. For example, a silicon wafer, a metal foil such as aluminum or stainless steel, a metal sheet metal plate, or the like. Moreover, it is also possible to use what laminated | stacked metal thin films, such as aluminum, copper, nickel, stainless steel, on the said plastic film and sheet | seat.

  In addition, it is more preferable to reduce the moisture adsorbed on the inside or the surface of the various substrates as much as possible by performing a heat treatment in advance. Further, in order to improve the adhesion depending on the material to be laminated on the substrate, it is preferable to use after performing surface treatment such as ultrasonic cleaning treatment, corona discharge treatment, plasma treatment, UV ozone treatment.

  Further, a thin film transistor (TFT) may be formed on the substrate to form a driving substrate. The TFT material may be an organic TFT such as polythiophene, polyaniline, copper phthalocyanine or perylene derivative, or may be amorphous silicon or polysilicon TFT. Further, a color filter layer, a light scattering layer, a light polarizing layer, or the like may be provided on either side of the substrate to form a substrate.

  Next, a first electrode 102 serving as an anode is formed on the substrate 101. As the anode forming material, metal composite oxides such as ITO (indium tin composite oxide), IZO (indium zinc composite oxide), and zinc aluminum composite oxide can be used. As a film forming method, a dry coating method can be used. For example, resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, and sputtering. Then, a photoresist can be applied to the vacuum-formed metal oxide film, exposed and developed, and processed into a pattern by wet etching or dry etching. In the case of a passive matrix organic EL element, the anode is formed in a stripe shape. In the case of an active matrix type organic EL element, the anode is patterned in a dot shape.

  After forming the anode, a pixel partition 103 is formed by photolithography using a photosensitive material between adjacent anode patterns. More specifically, it includes at least a step of applying a photosensitive resin composition to a substrate and a step of forming a pixel partition pattern by pattern exposure, development, and baking.

  As the photosensitive resin material for forming the pixel partition wall 103, either a positive resist or a negative resist can be used, and a commercially available material can be used, but it needs to have insulating properties. If the pixel partition does not have sufficient insulation, a current flows through the pixel partition to the adjacent pixel electrode, resulting in a display defect. Specific examples of the photosensitive resin material include, but are not limited to, polyimide, acrylic resin, novolac resin, and fluorene. Among these, the photosensitive polyimide is most suitable from the characteristics such as heat resistance, solvent resistance and low outgas. Further, in order to improve the display quality of the organic EL display panel and to prevent malfunction of the thin film transistor, a light shielding material may be included in the photosensitive material.

The photosensitive resin forming the pixel partition wall 103 is applied using a known coating method such as a spin coater, bar coater, roll coater, die coater, or gravure coater. Next, a pixel partition pattern is formed by pattern exposure and development.

  The pixel partition wall thickness of the organic EL element of the present invention is the thickness of the organic light-emitting layer formed by a wet film formation method in the subsequent step when the pixel partition film thickness is A (FIG. 2). 2), the film is formed so as to satisfy 5 ≦ film thickness A / film thickness B ≦ 100. At this time, both of the partition wall thickness in parallel to the film forming direction and the pixel partition wall thickness in the direction perpendicular to the film forming direction out of the two-direction partition walls partitioning each pixel satisfy the above conditions. However, the effect of the present invention can also be obtained when the pixel partition wall thickness parallel to the film forming direction satisfies the above conditions. The film thickness of the pixel partition can be made different by a method such as making a difference in the width of the pixel partition in the direction parallel to and perpendicular to the film forming direction, or using a halftone mask.

  3, 4, and 5 are schematic perspective views for explaining a part of the schematic structure of the pixel partition wall of the organic EL element of the present invention, and schematically show only the pixel partition wall formed on the substrate 110. The pixel partition includes a pixel partition 111 parallel to the film forming direction indicated by the block arrow and a pixel partition 112 perpendicular to the film forming direction along the four sides of the light emitting pixel portion 113. The pixel partition wall thickness of the organic EL device of the present invention is desirably 0.5 μm or more in order to reliably function as a partition wall that covers unevenness such as the lower electrode. In addition, the pixel partition wall thickness of the organic EL element of the present invention is preferably 4.0 μm or less in order to uniformly form an organic light emitting layer formed by a wet film forming method, but is not limited thereto. is not.

  After the pixel partition walls are formed as described above, the light emission auxiliary layer 104 is formed. As the material for forming the hole transport layer, polymer hole transport materials such as polyaniline, polythiophene, polyvinyl carbazole, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrene sulfonic acid, polythiophene oligomer materials, and other existing materials A coat can be selected from among the hole transport materials.

  These solvents for dissolving or dispersing the hole transport layer material include xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, water, etc. Or a mixed solvent thereof.

  The surface tension of the ink is desirably adjusted to 35 mN / m or less. This is because when the surface tension is greater than 35 mN / m, the liquid becomes distorted due to the surface tension immediately after the coating film is applied and the uniform flat surface is damaged. When the solvent is mainly water, a coat containing about 10 to 30% by volume of alcohol with respect to water is desirable to reduce the surface tension. If the concentration of alcohol with respect to water exceeds 30 vol%, unevenness tends to occur due to the difference in evaporation rate with water, and problems such as dispersion aggregation occur. Further, if it is 10 vol% or less, it is insufficient to lower the surface tension. The concentration of the ink using the solvent as described above is usually adjusted to include about 0.01% to 10%, preferably 0.1% to 3% solids.

  A material inked with the solvent as described above is applied to the substrate by wet coating. Examples of the wet coating method include spin coating methods, bar coating methods, dip coating methods, discharge coating methods, roll coating methods, and other coating methods, and letterpress printing methods, ink jet methods, intaglio printing methods, and the like.

  It is desirable that the film applied by the above method is quickly dried. For drying, any known heating method such as oven or hot plate may be used. When the hole transport layer is PEDOT / PSS (polythiophene / polystyrene sulfonic acid), the firing temperature of the hole transport layer is preferably heated at 130 ° C. to 230 ° C. If the firing temperature is less than 130 ° C., the firing condition is low, and there is a concern about problems such as insufficient evaporation of moisture from the hole transport layer as the light emission auxiliary layer 104. Contamination will be deteriorated by moisture. Moreover, if it is 230 degreeC or more, it is high temperature as baking conditions, and there exists a danger that the said positive hole transport layer will thermally deteriorate. It is desirable to determine the firing time in consideration of insufficient evaporation of moisture, influence on luminous efficiency, productivity, and the like. Moreover, when drying, you may dry under reduced pressure and may dry under nitrogen.

  After the step of improving the in-pixel shape of the hole transport layer that is the light emission auxiliary layer 104 by the heating, the organic light emitting layer 105 is formed. The organic light emitting layer 105 is a layer that emits light by passing an electric current. Examples of organic light emitting materials that form the organic light emitting layer include coumarin, perylene, pyran, anthrone, porphyrene, quinacridone, N, N Luminescent dyes such as' -dialkyl-substituted quinacridone, naphthalimide, N, N'-diaryl-substituted pyrrolopyrrole, iridium complex, etc. dispersed in polymers such as polystyrene, polymethylmethacrylate, polyvinylcarbazole, etc. , Polyarylene-based, polyarylene vinylene-based, polyphenylene vinylene-based, and polyfluorene-based polymer materials.

  These organic light emitting materials are dissolved or stably dispersed in a solvent to form an organic light emitting ink. Examples of the solvent for dissolving or dispersing the organic light-emitting material include toluene, xylene, acetone, anisole, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, or a mixed solvent thereof. Among these, aromatic organic solvents such as toluene, xylene, and anisole are preferable from the viewpoint of solubility of the organic light emitting material. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to organic luminescent ink as needed.

  In the present invention, the organic light emitting layer 105 is preferably formed using a relief printing method. Hereinafter, the relief printing method will be described in detail. As a relief printing plate that can be used to form part or all of the organic light emitting layer 105, it is preferable to use a water development type resin relief plate. Examples of the water-developable photosensitive resin constituting such a resin plate include a type having a hydrophilic polymer and a monomer containing an unsaturated bond, a so-called crosslinkable monomer and a photopolymerization initiator as constituent elements. In this type, polyamide, polyvinyl alcohol, cellulose derivatives and the like are used as the hydrophilic polymer. Examples of the crosslinkable monomer include methacrylates having a vinyl bond, and examples of the photopolymerization initiator include aromatic carbonyl compounds. Among these, a polyamide-based water-developable photosensitive resin is preferable from the viewpoint of printability. The convex portion (image portion) of the printing plate has a height of several tens of μm and is elastic, and the pixel partition of the substrate to be printed is at most several μm, so printing is performed by sufficiently overcoming the pixel partition. be able to.

  A printing press used for forming part or all of the organic light emitting medium layer can be used as long as it is a relief printing press using a flat plate as the substrate to be printed 607, but a printing press as shown below is desirable. FIG. 6 is a conceptual diagram of a relief printing press for producing the organic EL element of the present invention. The manufacturing apparatus includes an ink chamber 608, an anilox roll 601, and a plate cylinder 605 to which a resin relief plate 604 is attached via a cushion tape 603. The ink chamber 608 contains an organic light emitting layer forming ink. The anilox roll 601 rotates in contact with the ink supply unit of the ink chamber 608 and the plate cylinder 605.

With the rotation of the anilox roll 601, the organic light emitting layer forming ink supplied from the ink chamber 608 is uniformly held on the surface of the anilox roll 601 by the doctor blade 602, and then on the convex portion of the resin relief plate 604 attached to the plate cylinder. Transition with uniform film thickness. Further, the printing substrate 607 is fixed on a slidable substrate fixing stage (stage) 606, and the printing start position is adjusted while the position is adjusted by a position adjustment mechanism (not shown) of the pattern of the plate and the printing substrate pattern. As the plate cylinder 605 rotates, the convex portions of the resin relief plate 604 further move while in contact with the substrate 101, transfer ink to a predetermined position of the substrate 101, and pattern the organic light emitting layer 105.

  Next, after drying, a second electrode (cathode) 106 is formed. As a material for the cathode layer, a substance having high electron injection efficiency into the organic light emitting layer 105 is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface contacting the light emitting medium, and Al or Cu having high stability and conductivity is placed. You may use it, laminating | stacking. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, An alloy system with a metal element such as Al or Cu may be used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used. When the second electrode (cathode) 106 is used as a translucent electrode layer, a thin work piece of Li or Ca having a low work function is provided, and then ITO (indium tin composite oxide), indium zinc composite oxide, or zinc aluminum is used. A metal composite oxide such as a composite oxide may be laminated, or a metal oxide such as ITO may be laminated on the organic light emitting layer 105 by doping a small amount of a metal such as Li or Ca having a low work function. Good.

  The second electrode (cathode) 106 can be formed by coating using a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method, depending on the above-described materials. Although there is no restriction | limiting in particular in the thickness of the 2nd electrode (cathode) 106, About 10 nm-1000 nm are desirable. If the film thickness of the second electrode (cathode) 106 is less than 10 nm, the pinholes in the film are not sufficiently filled, causing a short circuit. On the other hand, when the thickness is larger than 1000 nm, the film forming time becomes long and the productivity is deteriorated. Note that the second electrode (cathode) 106 can be patterned by using a mask formed in a desired pattern at the time of film formation. However, in the case of the active matrix method, it is not necessary to perform patterning.

  Finally, these organic EL components are sealed using a sealing body 107 in order to protect them from external oxygen and moisture. As the sealing body 107, a sealing cap 107a having a concave portion is used, and a coating using a method in which the sealing cap 107a and the substrate 101 are bonded together with an adhesive 107b can be used. Further, a desiccant 107 c can be provided in the space sealed by the sealing cap 107 a and the substrate 101.

  A metal cap or a glass cap can be used as the sealing cap 107a. As the adhesive 107b, radical adhesives using resins such as acrylates such as ester acrylates, urethane acrylates, epoxy acrylates, melamine acrylates and acrylic resin acrylates, urethane polyesters, and cationic systems using resins such as epoxies and vinyl ethers. A coating using a photocurable resin such as an adhesive, a thiol / ene addition resin adhesive, or a thermosetting resin can be performed. Further, an ultraviolet curable epoxy adhesive can also be used. As the desiccant 107c, barium oxide or calcium oxide can be used.

  In addition to this, a barrier layer may be formed on the organic EL structure, and the barrier layer may be used as the sealing body 107. At this time, the barrier layer can be coated using silicon oxide, silicon nitride, silicon oxynitride or the like, and these are formed so as to cover the entire surface of the organic EL structure by a vacuum film forming method such as a CVD method. In addition, the organic EL element in which the barrier layer is formed can be attached to a sealing substrate through the adhesive layer 107 b to form the sealing body 107.

  Examples of the present invention and comparative examples are shown below, but the present invention is not limited thereto.

<Process for Manufacturing Printed Substrate 607>
First, as shown in FIG. 1, a substrate 101 on which a TFT circuit made of a metal, a metal oxide, and a metal nitride insoluble in water such as silicon and ITO is formed as a circuit layer on an alkali-free glass as a substrate 101. Prepared. The circuit wiring was made of Al, and the film thickness was 400 nm.

  Next, pixel partition walls were formed using a photosensitive resin on the substrate on which the TFT circuit was formed. In this embodiment, since the thickness of the organic light emitting layer 105 is 120 nm, the pixel partition wall thickness is set to 2.4 μm so that the thickness A / thickness B = 20.

First, the substrate 101 was treated with a low-pressure mercury lamp, washed by a wet process such as pure water, brush washing, and ultrasonic washing, and then positive-type photosensitive polyimide was spin coated on the entire surface. The spin coating conditions were 300 rpm for 5 seconds, 800 rpm for 20 seconds, and the height of the photosensitive material after spin coating was 3.3 μm. After spin coating, prebaking was performed at 120 ° C. for 5 minutes. The pre-baked substrate was exposed to light at an exposure amount of 200 mJ / cm ² using an i-line stepper through a photomask, and then developed. The film thickness of the pixel partition wall thus formed was 2.5 μm.

Next, PEDOT / PSS aqueous dispersion Vitron CH-8000 is 60%, ultrapure water is 20%, 1-propanol is used as the hole transport ink for forming the hole transport layer which is the light emission auxiliary layer 104. 20% was mixed to make an ink. A hole transport layer which is the light emission auxiliary layer 104 was formed on the substrate by slit coating using the above ink, and the film thickness was 50 nm. As a pretreatment, the substrate before application of the hole transport ink was irradiated with ultraviolet rays for 3 minutes using a UV / O ₃ cleaning device. In this way, a substrate to be printed 607 was produced.

<Process for producing organic light emitting layer forming ink>
The following polymeric organic light-emitting inks consisting of three colors of red, green and blue (R, G, B) were dissolved in xylene and prepared. The red light emitting ink (R) is a xylene 1 wt% solution of a polyfluorene derivative (red light emitting material manufactured by Sumitomo Chemical Co., Ltd., trade name Red 1100). The green light emitting ink (G) is a 1 wt% xylene solution of a polyfluorene derivative (green light emitting material, trade name Green 1300, manufactured by Sumitomo Chemical Co., Ltd.). The blue light-emitting ink (B) is a 1 wt% xylene solution of a polyfluorene derivative (blue light-emitting material manufactured by Sumitomo Chemical Co., Ltd., trade name Blue 1100).

<Production process of resin relief printing plate 604>
Using a nickel resin of a thickness of 250 μm as a base material for the relief printing plate 604 made of a photosensitive resin, an acrylic binder-resin solution kneaded with a black pigment is applied on the base material so that the dry film thickness is 10 μm and dried. Then, an antireflection layer was formed.

  Mainly water-soluble polyamide, dipentaerythritol hexakisacrylate as radical polymerizable monomer, 2,2-dimethoxy-1,2-diphenylethane-1-one as photopolymerization initiator (manufactured by Ciba Specialty Chemicals) A photosensitive resin composition obtained by kneading the resin is melt-coated on the surface of the substrate so that the total thickness of the plate material is 310 μm, and the photosensitive resin layer is used, and the polyvinyl alcohol solution has a dry film thickness of 1 μm. A polyethylene terephthalate film (film thickness 125 μm: manufactured by Teijin DuPont Films Ltd.) was laminated. Thereby, the photosensitive resin relief printing plate 604 was produced.

Using a synthetic quartz base chrome mask as the original pattern of the resin relief plate 604, this mask is set in a proximity exposure apparatus, and the photosensitive resin relief plate is exposed to produce a resin relief plate 604 on which a desired pattern is formed. did.

<Printing process of organic light emitting layer forming ink>
The resin relief plate 604 was fixed to the plate cylinder 605 of the sheet-fed printing apparatus via a cushion tape 603. Next, the high molecular organic light emitting ink was supplied to the ink chamber 608 and the anilox roll 601 was rotated to ink the entire surface. The anilox roll 601 was an anilox roll having a capacity of 11 cc and 600 lines / inch. Thereafter, excess ink on the anilox roll 601 was scraped with a doctor blade 602 and inked into the convex pattern portion of the resin relief printing plate 604.

  The ink for the organic light emitting layer 105 on the resin relief plate 604 that has been inked as described above is embedded in the substrate to be printed 607 in the pixel long side direction on the substrate by the relief printing apparatus shown in FIG. A total of 3 lines were formed, one line at a time. After the film formation, the film was dried in an oven at 130 ° C. for 1 hour. As a result, the thickness of the organic light emitting layer 105 in each line was 120 nm on average.

  A cathode material made of Ca and Al was deposited on the printed film by mask deposition so as to be deposited only on the pixel portion, thereby forming a second electrode (cathode) 106 having a thickness of 500 nm. Finally, in order to protect these organic EL constituents from external oxygen and moisture, they were hermetically sealed using a glass cap and an epoxy adhesive to produce an organic EL element.

  In the periphery of the display portion of the obtained organic EL element, there are a first electrode (an extraction electrode for the anode 102 and an extraction electrode for the second electrode (cathode) 106) connected to each pixel electrode. By connecting, an organic EL display panel was obtained.

  As shown in FIG. 4, an organic EL display panel was obtained in the same procedure as in Example 1 by changing the film thickness of the pixel partition 111 in the direction parallel to the film forming direction. By performing exposure, development, and baking processes through a photomask in which the width of the pixel partition wall 111 parallel to the film formation direction and the width of the pixel partition wall 112 perpendicular to the film formation direction are changed, the pixel partition wall 111 parallel to the film formation direction The film was formed so that the film thickness was 2.0 μm, and the film thickness of the vertical pixel partition 112 was 2.4 μm, and the light emission state was observed.

  When the organic EL display panel obtained as in Example 1 and Example 2 was checked for lighting display, it was confirmed that the shape of the light emitting pixel was good as shown in FIG. As a result, unevenness in light emission luminance was suppressed, and a display quality with no unevenness was obtained on the entire panel surface.

<Comparative Example 1>
In Comparative Example 1, an organic EL display panel was obtained in the same procedure as in Example 1, but the film was formed so that the pixel partition wall thickness was 3.2 μm and the organic light emitting layer 105 had an average thickness of 30 nm. The condition was observed.

  When the organic EL display panel thus obtained was lit and observed, as shown in FIG. 7, emission luminance unevenness was observed with the deterioration of the film shape of the organic light emitting layer 105 in the light emitting pixel, and the panel display. It was confirmed that the quality deteriorated.

<Comparative example 2>
In Comparative Example 2, an organic EL display panel was obtained by the same procedure as in Example 1, but the film was formed such that the pixel partition wall thickness was 0.5 μm, and the light emission state was observed.

When the organic EL display panel thus obtained was lit and observed, as shown in FIG. 8, emission luminance unevenness was observed as the shape of the organic light emitting medium layer film deteriorated in the light emitting pixels, and the panel display quality was improved. Confirmed that it gets worse.

  The above evaluation results are summarized and shown in Table 1.

101 ... Substrate 102 ... First electrode (anode)
103 ... partition wall (pixel partition wall parallel to the film forming direction)
104 ... light emission auxiliary layer 105 ... organic light emitting layer 106 ... second electrode (cathode)
107 ... Sealing body 107a ... Sealing cap 107b ... Adhesive 107c ... Drying agent 110 ... Substrate 111 ... Pixel partition 112 parallel to the film forming direction ... Film forming direction Pixel partition 113 perpendicular to the light emitting pixel portion 601... Anilox roll 602... Doctor blade 603 .. Cushion tape 604 .. Resin relief 605. ... Printed substrate 608 ... Ink chamber

Claims (6)

Between the first electrode formed in a pattern on the substrate and the second electrode provided so as to face the first electrode, a light-emitting pixel portion surrounded by a partition wall and arranged two-dimensionally is provided. An organic EL element provided,
The light emitting pixel portion is composed of an organic light emitting medium layer composed of an organic light emitting layer and a light emission auxiliary layer,
The organic light emitting layer and the light emitting auxiliary layer are formed by dissolving or dispersing the organic light emitting material and the light emitting auxiliary material in a solvent and formed by a wet film forming method.
An organic EL element characterized in that the thickness of the partition wall is A and the thickness of the organic light emitting medium layer is B, and 5 ≦ film thickness A / film thickness B ≦ 100 is satisfied.   2. The organic EL according to claim 1, wherein the partition wall thickness is 0.5 μm ≦ film thickness A ≦ 4.0 μm, and the organic light emitting medium layer thickness is B ≦ 0.2 μm. element. The partition is formed in a horizontal direction and a vertical direction with respect to a film forming direction of a wet film forming method for forming an organic light emitting medium layer,
The film thickness of the organic light emitting medium layer is defined as film thickness B, and the film thickness of the partition provided in the direction parallel to the film forming direction of the wet film forming method for forming the organic light emitting medium layer is defined as film thickness C. The organic EL element according to claim 1, wherein ≦ film thickness C / film thickness B ≦ 100 is satisfied.   The film thickness of the partition provided in a direction parallel to the film forming direction of the wet film forming method for forming the organic light emitting medium layer is 0.5 μm ≦ film thickness C ≦ 4.0 μm. The organic EL element as described in any one of 1-3.   The organic EL element according to claim 1, wherein the wet film forming method for forming the organic light emitting medium layer is a relief printing method.   A wet film-forming method for forming the organic light emitting medium layer of the organic EL element according to any one of claims 1 to 4 by dissolving or dispersing the organic light emitting material and the light emitting auxiliary material in a solvent is a relief printing method. A method for producing an organic EL element, characterized in that: