JP2008186766A - Manufacturing method of organic electroluminescent element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of uniform light emission by improving wetting-up to barrier ribs 3, in a manufacturing method of an organic electroluminescent element having at least first electrodes 2 and pixel barrier ribs 3 on a substrate 1, hole transport layers 4 and organic luminescent layers 5 between the pixel barrier ribs 3, and a second electrode 6 on upper parts thereof. <P>SOLUTION: This manufacturing method is characterized by including a process of forming the hole transport layers 4 by applying a coating liquid containing a hole transport material between the pixel barrier ribs 3 formed on the substrate 1, thereafter arranging a solution used as a solvent of the hole transport material on the surfaces of the hole transport layers 4, furthering leveling, and thereafter drying it. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for manufacturing an organic electroluminescent element used for light-emitting display of a display or other predetermined pattern.

  An organic electroluminescence element (hereinafter referred to as an organic EL element) 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 is an 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 structure is simple, a thin and lightweight device can be manufactured, and active research is currently underway. In addition, the organic EL element may include not only the organic light emitting layer but also a light emission auxiliary layer between the anode and the 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 the organic EL element include a low-molecular material and a high-molecular material. In general, a low-molecular material is formed into a thin film by a vacuum film-forming method (dry coating method) such as an evaporation method. However, when manufacturing a full-color organic EL element, it is necessary to pattern-form organic light-emitting layers having different colors of light emission such as R (red), G (green), and B (blue) for each pixel. At this time, a mask having a fine pattern is used when patterning the organic light emitting layer by a vacuum film forming method, but the patterning accuracy using a mask is less likely to increase as the substrate becomes larger. There was a problem. In addition, when the vapor deposition method is used among the vacuum film formation methods, the deposition source is usually a point shape like a pinhole or a crucible of a boat, so that the film thickness becomes uniform with respect to a large-sized substrate. There is also a problem that it is difficult to form a thin film layer.

  In contrast, recently, a polymer material is used as an organic light emitting material, and the organic light emitting material is dissolved or dispersed in a solvent to form ink (coating liquid), which is formed into a thin film by a wet coating method such as a coating method or a printing method. Methods are being tried. Since it is possible to form a thin film uniformly by using the wet coating method, it has been actively researched and developed because it is advantageous when a large substrate is used. Further, when the wet coating method is used, it is not necessary to use a vacuum apparatus, which is advantageous from the viewpoint of cost as compared with a dry coating method such as a vapor deposition method or a sputtering method.

  The structure of organic EL elements using polymer organic light-emitting materials is mainly hole transport layer / organic light-emitting layer / cathode, and all can be made by wet coating method except for electrodes such as anode and cathode. It is. 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 is a printing method. In particular, in the case where the organic light-emitting layer is patterned by coating the organic light-emitting layer with organic light-emitting layers having three different emission colors of R (red), G (green), and B (blue) for each pixel, Thin film formation by a printing method that is good at coating and patterning is considered to be most effective.

In addition, when forming the hole transport layer, which is a light emitting auxiliary layer, by a wet coating method, it is common to apply a so-called solid coating on the entire portion of the organic EL element involved in image formation without patterning, It has been formed using a coating method such as a coating method or a die coating method. This is because the film thickness of the hole transport layer is generally a thin film of 100 nm or less, and the current flowing in the thickness direction is overwhelmingly easier to flow than the current flowing in the lateral direction of the layer, so if the electrode is patterned, This is because current leaks out of the pixel very little.

  However, in the above coating method, the coating film finally becomes a film in the pixel portion while drying the partition walls separating the pixels, so that the cross-sectional shape of the pixels tends to be concave. When the concave shape is used, a portion that does not emit light appears depending on the film thickness, which ultimately leads to a decrease in the aperture ratio. Since the lifetime of an organic electroluminescent element will become short if an aperture ratio falls, improvement is desired.

  As described above, in the organic electroluminescence element formed using wet coating, the shape in the pixel is very important. As a method for bringing the shape in the pixel close to flat, according to Patent Document 1, the shape in the pixel is improved by forming the partition so as to have a shape inclined from the partition wall surface toward the electrode side. However, with this method, it is very difficult to produce an inclined part when considering the production of a high-definition display, and the possibility of implementation is low. In addition, as a process improvement plan, according to Patent Document 2, in order to eliminate the film thickness distribution due to the flow of ink at the time of drying, a method of freezing the ink and evaporating the water after freezing the ink is taken. It is necessary to gradually cool down the substrate cooling again, and at that time, the drying is gradually progressed and the possibility that the effect is produced is low. In addition, as disclosed in Patent Document 3, there is an example of trying to improve the shape in the pixel by setting the partition walls in two stages, the upper stage being liquid-repellent, and the lower stage being lyophilic. This method makes it difficult to form a layer that does not require coating, for example, a hole transport layer, because the upper part of the partition wall is liquid repellent. In addition, since it is a two-stage partition wall, the photolithography process must be performed twice and the efficiency is poor.

Known documents are described below.
JP 2004-198486 A JP 2004-55279 A JP 2004-319119 A

  In the present invention, when the light emitting auxiliary layer and the organic light emitting layer typified by the hole transport layer as described above are formed on a substrate by a wet coating method using a coating liquid, the wetting to the partition wall is improved and uniform. An object of the present invention is to obtain an organic electroluminescence device capable of emitting light smoothly.

  According to a first aspect of the present invention for solving the above-described problem, a first electrode and a pixel partition are provided on at least a substrate, a hole transport layer and an organic light emitting layer are provided between the pixel partitions, and a second electrode is provided on the top. A method for producing an organic electroluminescent element comprising: a coating liquid containing a hole transport material applied between pixel partition walls formed on a substrate to form a hole transport layer; The method of manufacturing an organic electroluminescence device is characterized by including a step of arranging a liquid to be formed on the surface of the hole transport layer, promoting leveling, and then drying.

  Invention of Claim 2 for solving the said subject is set as the manufacturing method of the organic electroluminescent element of Claim 1 characterized by the liquid used as a solvent containing water and a water-soluble solvent. .

The invention of claim 3 for solving the above-mentioned problems is that the method of arranging the liquid as a solvent is a wet coating method, and is a slit coating method, spray coating method, bar coating method, ink jet method, letterpress printing table, intaglio printing 2. The method of claim 1, wherein the method is a lithographic printing method.
Or it is set as the manufacturing method of the organic electroluminescent element of 2.

  The invention according to claim 4 for solving the above-mentioned problems is characterized in that the surface tension of the liquid serving as the solvent is 35 mN / m or less, wherein the organic electroluminescence element according to any one of claims 1 to 3 is used. This is a manufacturing method.

  According to a fifth aspect of the present invention for solving the above-mentioned problems, the height at the time of arrangement of the liquid as the solvent is a value smaller than twice the height of the pixel partition wall. It is set as the manufacturing method of the organic electroluminescent element of 1 item | term.

  In the present invention, in the method of manufacturing an organic electroluminescence device including a step of forming a hole transport layer by applying a coating liquid in pixels separated by partition walls, the holes dried in the hole transport layer formation step This is a method for manufacturing an organic electroluminescent element that can obtain an organic electroluminescent element having a good shape in a pixel by arranging a liquid as a solvent again on the transport layer and promoting leveling.

  An embodiment of a method for producing an organic EL element of the present invention will be described. However, the present invention is not limited to these.

  FIG. 1 shows a schematic cross-sectional view of an example of an organic EL element according to the present invention. The organic EL element of FIG. 1 includes an anode 2, a hole transport layer 4, an organic light emitting layer 5, and a cathode 6 on a substrate 1. An organic light emitting layer 5 is provided between the anode 2 and the cathode 6, and a hole transport layer 4 is provided between the anode 2 and the organic light emitting layer 5. A partition wall 3 is provided between the anode 2 patterns. The organic EL structure in which the anode 2, the partition wall 3, the hole transport layer 4, the organic light emitting layer 5, and the cathode 6 are provided on the substrate 1 is sealed to protect the electrode and the organic light emitting layer from the external environment. A body 7 is provided. The sealing body 7 includes a sealing cap 7a, an adhesive 7b, and a desiccant 7c.

  In the organic EL device of the present invention, a light emission auxiliary layer is provided in addition to the organic light emitting layer between the anode and the cathode. Examples of the light emission auxiliary layer include an electron injection layer, an electron transport layer and the like in addition to the hole injection layer shown in FIG. These light emission auxiliary layers are appropriately selected, but 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 are provided between the organic light emitting layer and the cathode. In the organic EL device of the present invention, the anode, cathode, organic light emitting layer, and hole transport layer may have a multilayer structure instead of a single layer structure.

  In addition, the organic EL element of the present invention can be applied to both a passive matrix type organic EL element and an active matrix type organic EL element. 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 organic EL element, one of the anode and cathode electrodes is provided for each pixel on the TFT substrate, and the other electrode is provided for the entire pixel.

  The organic EL element of the present invention may be either a bottom emission type organic EL element that extracts emitted light from the substrate side or a top emission type organic EL element that extracts emitted light from the opposite side of the substrate. Absent. In the case of a bottom emission type organic EL element, the substrate and the anode need to have light transmittance, and in order to obtain a top emission type organic EL element, the cathode and the sealing body have light transmittance. There is a need.

  Moreover, in the organic EL element of this invention, you may provide in order of a cathode, an organic light emitting layer, a positive hole transport layer, and an anode on a board | substrate contrary to FIG.

  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 1 according to the present invention, any substrate can be used as long as it is an insulating substrate. In the case of a bottom emission element that emits light 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 such a substrate. Further, it may be a plastic film or sheet such as polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate. These plastic films and sheets laminated with a metal oxide thin film, a metal fluoride thin film, a metal nitride thin film, a metal oxynitride thin film, or a polymer resin film may be used as the substrate.

  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, silicone resin, and polyester resin. In the case of a top emission element, an opaque substrate can also be used. 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 substrate as much as possible by performing a heat treatment on these substrates 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. In addition, a color filter layer, a light scattering layer, a light polarizing layer, or the like may be provided on either surface of the substrate to form a substrate.

  Next, the anode 2 is formed on the substrate 1. 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 the anode 2 is formed, the partition wall 3 is formed by a photolithography method using a photosensitive material between adjacent anode patterns. More specifically, at least a step of applying the photosensitive resin composition to the substrate and a step of forming a partition wall pattern by pattern exposure, development, and baking are included.

  The photosensitive material for forming the partition wall 3 may be either a positive resist or a negative resist, and may be a commercially available one, but it needs to have insulating properties. If the partition wall does not have sufficient insulation, a current flows to the adjacent pixel electrode through the partition wall, resulting in a display defect. Specific examples of the photosensitive material include, but are not limited to, polyimide, acrylic resin, novolac resin, and fluorene. Further, for the purpose of improving the display quality of the organic EL display panel, a light shielding material may be contained in the photosensitive material.

  The photosensitive resin forming the partition walls 3 is applied using a known coating method such as a spin coater, bar coater, roll coater, die coater, or gravure coater. Next, in the step of pattern exposure and development to form the partition wall pattern, the partition wall pattern can be formed by a conventionally known exposure and development method. Regarding firing, firing can be performed by a conventionally known method using an oven, a hot plate or the like.

  The partition wall 3 desirably has a thickness in the range of 0.5 μm to 5.0 μm. By providing the partition walls 3 between adjacent pixel electrodes, the hole transport coating liquid applied on the electrode pattern is leveled and the film thickness on the partition walls is reduced, so that leakage between adjacent pixels is less likely to occur. In addition, it is possible to prevent the occurrence of a short circuit from the anode end. In addition, when the pixels are separately coated using an organic light emitting coating solution in which organic light emitting materials having different luminescent colors are dissolved or dispersed in a solvent, color mixing with adjacent pixels can be prevented. If the partition walls are too low, it is necessary to prevent the occurrence of leakage current between adjacent pixels via the hole transport layer, the prevention of short circuit, and the effect of color mixing.

  After the pretreatment, the hole transport layer 4 is formed. As a material for forming the hole transport layer 4, polymer hole transport materials such as polyaniline, polythiophene, polyvinyl carbazole, a mixture of poly (3,4-ethylenedioxythiophene) and polystyrenesulfonic acid, polythiophene oligomer materials, and others You can choose from existing 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 and the like alone or a mixture thereof. A solvent etc. are mentioned.

  The surface tension of the coating solution is preferably adjusted to 50 mN / m or less. This is because if the surface tension is greater than 50 mN / m, the liquid is generated by the surface tension immediately after the coating film is applied. When the solvent is mainly water, it is preferable to add alcohol of about 10-30 vol% with respect to water in order 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% -10%, preferably 0.1% -3% solids.

  A material that has been liquefied with the solvent as described above is applied to the substrate by a wet coating method. Examples of the wet coating method include a spin coating method, a bar coating method, a dip coating method, a discharge coating method, a roll coating method, and a printing method such as a relief printing method, an inkjet printing method, and an intaglio printing method.

It is desirable that the film applied by the above method is quickly dried. Any of known heating methods such as an oven and a hot plate may be used for drying. When the hole transport layer is PEDOT / PSS, the firing temperature of the hole transport layer is preferably heated at 130 ° C. to 230 ° C. for 10 minutes to 60 minutes. Here, when the firing temperature is less than 130 ° C., the firing conditions of the hole transport layer are low, and there is a concern about problems such as insufficient evaporation of moisture from the hole transport layer. This is because if the moisture remains in the partition walls, the light emitting material is contaminated and deteriorated by the moisture. Moreover, since the temperature is too high at 230 ° C. or higher, there is a risk that the hole transport layer is thermally deteriorated. Further, if the time is 10 minutes or less, the firing is short, so that firing is insufficient, and if the time is 60 minutes or more, the productivity is inferior, which is not preferable. Moreover, when drying, you may dry under reduced pressure and may dry under nitrogen.

  After the application of the hole transport layer, the in-pixel shape improving method of the present invention is applied. In the pixel shape improving method of the present invention, the pixel is formed by re-dissolving the dried film by promoting a leveling by disposing a liquid that can be a solvent on the hole transport layer 4 that has been dried to form a film. It is to improve the inner shape.

  The liquid arrange | positioned on the positive hole transport layer 4 is described. The liquid disposed on the hole transport layer 4 for improving the shape in the pixel is not particularly limited as long as it can dissolve or disperse the hole transport layer material. Since the transport layer material is generally often dispersed in water, the liquid to be used is preferably water or a mixed solution of water and a water-soluble solvent. By using a mixed solution with a water-soluble solvent rather than water alone, the viscosity and surface tension of the liquid can be freely controlled. Water-soluble solvents that can be used include methanol, ethanol, isopropyl alcohol, normal propyl alcohol, butanol, ethylene glycol, propylene glycol, glycerin, methyl cellosolve, ethyl cellosolve, butyl cellosolve, carbitol, diethylene glycol, methoxypropyl acetate, propylene glycol Monomethyl ether, propylene glycol monoethyl ether, acetone, methyl ethyl ketone, tetrahydrofuran, dioxane, dioxolane, dimethylformamide, N-methyl-pyrrolidone, methyl acetate, ethyl acetate and the like can be used. The mixing ratio of water and the water-soluble solvent is preferably in the range of 5-30% by volume. If the amount of the water-soluble solvent is less than 5%, the properties (surface tension, viscosity) of the liquid cannot be changed. On the other hand, if it exceeds 30%, the hole transport layer may be aggregated without being well dispersed when redissolved.

  In addition, a surfactant may be added to the above mixed solvent. The surfactant that can be used is a nonionic surfactant. By using a nonionic surfactant, the surface tension of the liquid can be reduced, and since it is nonionic, it has little influence on the membrane. Nonionic surfactants that can be used are polyoxyethylene alkyl ether, dimethicone copolyol, sucrose fatty acid ester, sucrose stearate, polyoxyethylene sorbitol tetraoleate (polyoxyethylene sorbitol tetraoleate) , Poly (oxyethylene / oxypropylene), methylpolysiloxane copolymer, polyoxyethylene octylphenyl ether, polyoxyethylene stearyl ether, polyoxyethylene stearamide, polyoxyethylene cetyl ether, polyoxyethylene polyoxypropylene glycol , Polyglycerol fatty acid ester, polyoxyethylene sorbitan monooleate, ethylene glycol monostearate, glyceryl monostearate Sorbitan monostearate, propylene glycol monostearate, polyoxyethylene glyceryl monostearate, polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitan monopalmitate, polyethylene glycol monolaurate, polyoxyethylene sorbitan monolaurate, monolaurin Acid polyoxyethylene sorbite, lauric acid diethanolamide and the like can be used. Of these, polyoxyethylene alkyl ether is preferably used. A surfactant containing polyoxyethylene alkyl ether is desirable because it can change the surface tension greatly with a small addition amount.

  Next, a method for arranging the liquid on the hole transport layer 4 will be described. One method of arranging the liquid is a wet coating method. The wet coating method to be used is preferably a method that does not give heat or vibration to the substrate at the time of application. As the wet coating method that satisfies the above conditions, the slit coating method, spray coating method, bar coating method, ink jet method, letterpress It is preferable to use any one of a printing method, an intaglio printing method, and a planographic printing method. Among these, it is more preferable to use the slit coat method and the relief printing method. By using the slit coating method, the liquid can be applied uniformly and the film thickness can be easily controlled. Moreover, the characteristic range of the liquid that can be applied is wide, and the degree of freedom of liquid selection is wide. Also, by using the relief printing method, the liquid can be placed directly on the target part, the amount of liquid to be applied can be easily controlled, and unevenness due to flow can be minimized, so that a better effect can be achieved. It is preferable because it can be obtained.

  The surface tension of the liquid to be used is desirably 35 mN / m or less. If the surface tension of the liquid is larger than 35 mN / m, the liquid is liable to be generated and repelled on the substrate. Although the smaller the surface tension of the liquid, the better.

  Here, in the liquid placement step, the height of the liquid to be placed must be lower than twice the height of the pixel partition wall 3 formed. When the liquid level is higher than twice the partition wall height, the re-dissolved hole transport layer flows on the substrate and causes unevenness.

  As described above, the organic light emitting layer 5 is formed after the step of improving the shape in the hole transport layer pixel that promotes leveling. The organic light emitting layer 5 is a layer that emits light by passing an electric current, and the organic light emitting material forming the organic light emitting layer 5 is, for example, a coumarin type, a perylene type, a pyran type, an anthrone type, a porphyrene type, a quinacridone type, N, N'-dialkyl-substituted quinacridone-based, naphthalimide-based, N, N'-diaryl-substituted pyrrolopyrrole-based, iridium complex-based luminescent dyes dispersed in polymers such as polystyrene, polymethyl methacrylate, polyvinyl carbazole, etc. And 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 coating solution. 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. In addition, a surfactant, an antioxidant, a viscosity modifier, an ultraviolet absorber, and the like may be added to the organic light emitting coating liquid as necessary.

  As a method for forming the organic light emitting layer 5, in addition to the slit coating method of the present invention, a pattern can be formed by an ink jet method, a relief printing method, an intaglio offset printing method, a relief reverse printing method, or the like.

Next, the cathode 6 is formed. As a material of the cathode layer 6, a substance having a high electron injection efficiency into the organic light emitting layer 5 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 cathode layer 6 is used as a translucent electrode layer, Li (Ca) having a low work function is provided thinly, then ITO (indium tin composite oxide), indium zinc composite oxide, zinc aluminum composite oxide, etc. A metal oxide such as ITO may be laminated on the organic light emitting layer 5 by doping a small amount of a metal such as Li or Ca having a low work function.

  Depending on the material, the cathode 6 can be formed by resistance heating vapor deposition, electron beam vapor deposition, reactive vapor deposition, ion plating, or sputtering. Although there is no restriction | limiting in particular in the thickness of a cathode, About 10 nm-1000 nm are desirable. If the film thickness of the cathode is less than 10 nm, the film pinholes 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. In addition, about patterning of a cathode, pattern formation can be performed by using a mask at the time of film-forming.

  Finally, in order to protect these organic EL constituents from external oxygen and moisture, the organic EL constituents are sealed using the sealing body 7. As the sealing body 7, the sealing cap 7a which has a recessed part can be used, and the method of bonding the sealing cap 7a and the board | substrate 1 through the adhesive agent 7b can be used. The space sealed by the sealing cap 7a and the substrate 1 can be provided with a desiccant 7c.

  A metal cap or a glass cap can be used as the sealing cap 7a. Adhesive 7b includes 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. Photocurable resins such as adhesives, thiol / ene-added resin adhesives, or thermosetting resins can be used. Further, an ultraviolet curable epoxy adhesive can also be used. As the desiccant 7c, barium oxide or calcium oxide can be used.

  In addition to this, it is possible to form a barrier layer on the organic EL structure and use the barrier layer as a sealing body. At this time, silicon oxide, silicon nitride, silicon oxynitride, or the like can be used as the barrier layer, 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. Moreover, the organic EL element in which the barrier layer is formed can be attached to a sealing substrate through an adhesive layer, and these can be used as a sealing body.

  Examples of the present invention will be described. An ITO (indium-tin oxide) thin film was formed on a 3-inch diagonal glass substrate by sputtering, and the ITO film was patterned by photolithography and etching with an acid solution to form pixel electrodes. The line pattern of the pixel electrode was a 133 ppi pattern in which 960 lines were formed with a line width of 40 μm, a space of 23 μm, and a line of about 60 mm.

  Next, the partition was formed as follows. A positive photosensitive polyimide was spin coated on the entire surface of the glass substrate on which the pixel electrode was formed. The spin coating condition was rotated at 150 rpm for 5 seconds and then rotated at 500 rpm for 20 seconds to form a single coating, and the partition wall height was 2.0 μm. The photosensitive material applied to the entire surface was exposed and developed by a photolithography method to form a partition having a line pattern between the pixel electrodes. Thereafter, the partition walls were baked in an oven at 230 ° C. for 30 minutes.

Next, as a hole transport ink, PEDOT / PSS aqueous dispersion Vitron CH-8000 60%, ultrapure water 20%, and 1-propanol 20% were mixed to obtain an ink. A hole transport layer was formed on the substrate by the slit coating method using the above ink, and the film thickness was 60 nm. As a pretreatment, the substrate before applying the hole transport ink was irradiated with ultraviolet rays for 3 minutes using a UV / O ₃ cleaning device manufactured by Oak Manufacturing.

  Next, as a method for improving the in-pixel shape of the hole transport layer of the present invention, a water / IPA mixed solvent was applied using a slit coating method. Water / IPA was mixed at a ratio of 4/1. The mixed solution has a viscosity of 7 cP and a surface tension of 27.4 mN / m. The coating conditions were estimated from the coating conditions with the hole transport layer ink, and adjusted so that the height of the mixed solvent was 2.5 μm. After coating, it was immediately put into a vacuum oven at 50 ° C., depressurized to 10 Pa, and dried for 10 minutes. Thereafter, it was put into an oven heated to 200 ° C. and baked for 20 minutes.

  Next, using an organic light emitting ink in which a polyphenylene vinylene derivative, which is an organic light emitting material, is dissolved in toluene to a concentration of 1%, an organic light emitting layer is formed in line with the line pattern directly above the pixel electrode sandwiched between the partition walls. A pattern was formed by an ink jet method. At this time, the thickness of the organic light emitting layer after drying was 80 nm.

  A cathode layer made of Ca and Al was formed thereon by mask evaporation using a resistance heating evaporation method in a stripe pattern perpendicular to the stripe pattern of the pixel electrode. 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.

  There are an anode side extraction electrode and a cathode side extraction electrode connected to each pixel electrode in the peripheral part of the display portion of the obtained organic EL element, and these are connected to a power source to thereby provide an organic EL display panel. Got.

  In Example 1, coating was performed using a relief printing method as a method for improving the shape of the hole transport layer in the pixel. As the letterpress plate, an AWP version manufactured by Asahi Kasei was used. As the ink to be applied, a mixed solvent of water / ethylene glycol monobutyl ether was used. The mixing ratio was 4: 1. When the viscosity of the mixed solvent was measured, it was 17.8 cP and the surface tension was 28.9 mN / m. This mixed solvent was applied directly into the pixel using a relief printing method. The coating conditions were adjusted so that the film thickness during coating was 1 μm. Others produced the organic EL element similarly to Example 1, and obtained the organic EL display panel by connecting these to a power supply.

(Comparative Example 1)
In Example 1, the hole transport coating step was performed without performing the in-pixel shape improving step of the present invention. Others produced organic EL elements in the same manner as in Example 1 and connected them to a power source to obtain an organic EL display panel.

(Comparative Example 2)
In Example 1, pure water was applied using a slit coat method as the in-pixel shape improving step of the present invention. Water had a viscosity of 1 cP and a surface tension of 72.8 mN / m. Others produced organic EL elements in the same manner as in Example 1 and connected them to a power source to obtain an organic EL display panel.

(Comparative Example 3)
In Example 1, IPA was applied using the slit coat method as the in-pixel shape improving step of the present invention. IPA had a viscosity of 2.4 cP and a surface tension of 21.4 mN / m. Others produced organic EL elements in the same manner as in Example 1 and connected them to a power source to obtain an organic EL display panel.

(Comparative Example 4)
In Example 1, as the in-pixel shape improving step of the present invention, the film thickness was adjusted to 5 μm after applying the mixed solvent of water and IPA using the slit coating method. Others produced organic EL elements in the same manner as in Example 1 and connected them to a power source to obtain an organic EL display panel.

(Comparative Example 5)
In Example 1, a mixed solvent of water and IPA was applied by using a spin coat method instead of using the slit coat method as the in-pixel shape improving step of the present invention. Others produced organic EL elements in the same manner as in Example 1 and connected them to a power source to obtain an organic EL display panel.

  The following evaluation was performed about the board | substrate and organic electroluminescent display panel in which the positive hole transport layer obtained in Example 1, 2 and Comparative Examples 1, 2, 3, 4, and 5 was formed.

(1) Confirmation of light emission state The obtained organic EL display was caused to emit light by passing an electric current, and the light emission state was visually confirmed.

(2) Evaluation of wetting The surface of the substrate after applying the hole transport layer is measured with a stylus step meter, and the range from the thickness of the central portion to the thickness of 10 nm as shown in FIG. Evaluation was made with a / b when the width was b as the flatness.

  The evaluation results are shown below.

In Table 1, 5 is very good, 4 is good, 3 is normal, 2 is bad, and 1 is very bad.

  In Example 1, after the display was created, the entire surface was turned on and the unevenness was visually observed. Further, when the flatness was measured, it was 68%, which was a good value.

  In Example 2, when the entire surface was turned on after the display was created and the unevenness was visually observed, uniform light emission without unevenness could be obtained. Further, when the flatness ratio was measured, it was 76%, indicating a very good value.

  In Comparative Example 1, when the entire surface was turned on after the display was created and the unevenness was visually observed, uniform light emission without unevenness could be obtained. Further, when the flatness ratio was measured, it was 49%, which was a very bad result.

  In Comparative Example 2, when the entire surface was turned on after the display was created and the unevenness was visually observed, it was confirmed that the unevenness caused by the liquid was generated and the display was slightly affected. Further, when the flatness was measured, it was 60%, which was better than the case without treatment.

  In Comparative Example 3, when the entire surface was turned on after the display was created and the unevenness was visually observed, uniform light emission without unevenness could be obtained. However, when looking at the inside of the pixel, it looks like a rough surface. Further, when the flatness was measured, it was 63%, which was better than that without treatment.

  In Comparative Example 4, when the entire surface was turned on after the display was created and the unevenness was visually observed, unevenness that was thought to be due to the flow of the station was observed, which affected the display. Further, when the flatness was measured, it was 70%, which was favorable.

  In Comparative Example 5, when the entire surface was turned on after the display was created and the unevenness was visually observed, unevenness was generated radially from the center, affecting the display. Further, when the flatness ratio was measured, it was 65%, which was better than that without treatment.

It is a cross-sectional schematic diagram of an example of the organic EL element which concerns on the manufacturing method of organic EL of this invention. It is explanatory drawing which showed the method of measuring the flat rate after application | coating of the positive hole transport layer which concerns on the Example of this invention.

Explanation of symbols

1: substrate 2: anode 3: partition wall 4: hole transport layer 4x: undried hole transport ink 5: organic light emitting layer 6: cathode 7: sealing body 7a: sealing cap 7b: adhesive 7c: drying agent

Claims (5)

A method for producing an organic electroluminescence device comprising at least a first electrode and a pixel partition on a substrate, a hole transport layer and an organic light emitting layer between the pixel partitions, and a second electrode on the top.
After applying a coating liquid containing a hole transport material between the pixel barriers formed on the substrate to form a hole transport layer, a liquid serving as a solvent for the hole transport material is disposed on the surface of the hole transport layer. A method for producing an organic electroluminescence device, comprising the steps of promoting leveling and then drying.   The method for producing an organic electroluminescent element according to claim 1, wherein the liquid serving as the solvent contains water and a water-soluble solvent.   The method of arranging the liquid as a solvent is a wet coating method, and is any one of a slit coating method, a spray coating method, a bar coating method, an ink jet method, a relief printing table, an intaglio printing method, and a lithographic printing method. The manufacturing method of the organic electroluminescent element of Claim 1 or 2.   The surface tension of the liquid used as a solvent is 35 mN / m or less, The manufacturing method of the organic electroluminescent element of any one of Claims 1-3 characterized by the above-mentioned.   5. The method of manufacturing an organic electroluminescence element according to claim 1, wherein the height of the liquid serving as the solvent is less than twice the height of the pixel partition wall.