JP2008077958A - Manufacturing method of organic el element - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of an organic EL element having no defect and no unevenness by forming a film repelling no ink and having a uniform film thickness. <P>SOLUTION: This manufacturing method of the organic EL element at least has a process to form a barrier rib pattern on a transparent substrate, and a process to form a layer by transferring hole transport ink to an region surrounded by the barrier rib by a letterpress printing method, and the surface tension of the hole transport ink is 40 mN/m or less. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to a method for manufacturing an organic EL element, and more specifically, in an organic EL element in which a hole transport layer is formed by a relief printing method, an organic EL element that emits light uniformly in each pixel without repelling or unevenness. It relates to a manufacturing method.

In an organic light emitting device, a hole transport layer made of a hole transport material and an organic light emitting layer made of an organic light emitting material are formed between two opposing electrodes. Here, these layers are collectively referred to as an organic light emitting layer. The organic light-emitting device emits light by passing a current through these organic light-emitting layers. However, the thickness of the organic light-emitting layer is important for efficient light emission, and it is necessary to form a thin film of about 100 nm. Furthermore, in order to make this a display panel, it is necessary to pattern it with high definition.

  Hole transport materials and organic light-emitting materials that form the organic light-emitting layer include low-molecular materials and high-molecular materials. In general, low-molecular materials are formed into thin films by vacuum deposition or the like, and a fine pattern mask is used at this time. However, this method has a problem that the patterning accuracy is less likely to increase as the substrate becomes larger. In addition, since the film is formed in a vacuum, there is a problem that the throughput is poor.

  Therefore, recently, a method in which a polymer material is dissolved in a solvent to form a coating solution and a thin film is formed by a wet coating method has been tried. In the case of forming an organic light emitting medium layer including an organic light emitting layer by a wet coating method using a coating material of a polymer material, the layer structure is generally a two-layer structure in which a hole transport layer and an organic light emitting layer are laminated from the anode side. Is. At this time, the organic light emitting layer is formed by dissolving or stably dispersing organic light emitting materials having respective emission colors of red (R), green (G), and blue (B) in a solvent in order to form a color panel. It is necessary to paint with organic luminescent ink.

  On the other hand, the hole transport layer is generally not patterned, but is generally applied to the entire part related to image formation of the organic EL display panel, so-called solid coating, using a coating method such as spin coating or die coating. Has been formed. 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 it was said that there is very little leakage of current outside the pixel.

  However, even if patterning for each pixel is unnecessary in the above application method, a film is also formed at a place where an adhesive for sealing is applied or a place where a driver chip is mounted. A process of wiping and removing unnecessary portions of the hole transport layer was necessary.

  Accordingly, it is very demanded to form not only the organic light emitting layer but also the charge transport layer only on the pixel electrode in order to shorten the process and cost.

  The hole transport material forming the hole transport layer is made of a polymer material such as (3,4-polyethylenedioxythiophene) (PEDOT). In order to dissolve or stably disperse a hole transport material in a solvent to obtain a hole transport ink, the concentration is as low as about 2% due to both the solubility problem of the polymer material and the necessity of forming a thin film. There is a need to.

When patterning a low-viscosity hole transport ink having a concentration of about 2%, a partition is required to prevent the ink from spreading. This can be solved by increasing the height of the insulating layer between the pixel electrodes and using it as a partition wall. As a method for forming the hole transport ink in the pixel electrode partitioned by the partition walls, an ink jet method or the like can be considered.

  In the ink jet method, ink is dropped from an ink jet nozzle onto a printing site a plurality of times, and there is a distance between the nozzle and the printing substrate, and the ink spreads to the printing site in the partition only by its own gravity. Therefore, in the ink jet method, it is difficult to transfer the ink to all the portions to be printed surrounded by the partition walls, and there is a problem that printing omission is likely to occur especially at the edge of the pixel electrode.

  A method for preventing printing omission in the ink jet method has also been devised, but in order to do so, it is necessary to sufficiently fill the opening with ink, but in order to prevent ink from overflowing from the partition wall, the partition wall is water repellent. There is a problem that the number of processes is increased. The ink dropped on the water-repellent partition wall is piled up, which leads to poor film thickness uniformity in the pixels, which causes a problem in the uniformity and stability of the display panel.

  In order to produce a full color panel with good display quality as described above, an effective pattern forming method for each layer is indispensable, but in order to be industrially useful, a thin film forming method is inexpensive and simple. Need to be.

  On the other hand, in the letterpress printing method, the convex part of the letterpress is pressed against the printing site, so that the ink is strengthened in the horizontal direction in the pixels surrounded by the partition by pressing the plate and filling the space formed by the partition with the letterpress. It is pushed out. Therefore, printing omission at the edge of the pixel electrode is unlikely to occur. In addition, letterpress printing is simple and has the advantage that the throughput is better than that of an ink jet method or the like. Therefore, the relief printing method is suitable for forming the hole transport layer from the hole transport ink.

  The letterpress printing method refers to all printing methods that use a plate whose image line portion has a convex shape, that is, a letterpress, in a broad sense, but the letterpress printing method described in the present invention uses a letterpress made of a rubber plate or a resin plate. The printing method will be shown. Also, in the printing industry, those using rubber letterpress are called flexographic printing, and those using resin letterpress are called to distinguish from resin letterpress printing, but in the present invention, both are not particularly distinguished and called letterpress printing method. To do. Currently, photosensitive rubber plates and resin plates are mainly used for the relief printing system, but the material of the relief plate is also diversified, and the distinction between photosensitive rubber plates and photosensitive resin plates. In the present invention, this distinction is not particularly provided, and both are called photosensitive resin relief plates.

  However, in order to form a uniform hole transport layer without defects and unevenness by the relief printing method and obtain a good organic EL display, since the amount of ink transferred by the relief printing method is small, once on the substrate In order to prevent the ink transferred to the ink from being repelled from the partition walls, it is necessary to make the ink composition sufficiently wet.

  In addition, the wettability of the hole transport layer ink with respect to the printing plate is also important, but it is inappropriate to adjust the wetness to an appropriate range in order to perform good printing.

  According to Patent Document 1, the surface tension can be reduced by adding a surfactant, and as a result, a film free of pinholes and repellency can be obtained. It is pointed out that the film remains on the film surface even after film formation, and when the film is laminated on the film, the adhesion between the films is weakened, and in the organic EL element composed of thin film lamination, the element characteristics and life are adversely affected. Should not be used.

  As another method for lowering the surface tension, surface tension reduction by adding methanol, ethanol, 2-propanol or the like is often performed. However, the alcohols are easily dissolved in water-soluble inks, but after the wet film is formed, the alcohol component quickly evaporates before the water, causing the dry state to become uneven in the film and causing unevenness. It was.

Known documents are described below.
Japanese Patent Laid-Open No. 2005-5020

  The present invention has been made to solve the above-mentioned problems, and the problem is to form a hole transport layer by transferring ink to the pixels delimited by the partition walls by letterpress printing. In other words, the present invention provides a method for producing an organic EL element free from defects and unevenness by forming a uniform film without ink repelling or the like.

  By the way, according to the study of the present inventor, it is possible to form a good pattern by lowering the surface tension of the hole transport ink, and further by using the hole transport ink added with an appropriate amount of an appropriate organic solvent. A positive hole transport ink could be obtained.

  The present invention has been made on the basis of such knowledge, and as the invention according to claim 1, a step of forming a partition pattern on a transparent substrate, and a hole transport by a relief printing method in a region surrounded by the partition And a step of forming a hole transport layer by transferring ink, wherein the hole transport ink is a water-soluble ink and is 20% by volume based on at least one kind of water. An organic solvent that can be mixed at the above ratio, has a vapor pressure at 20 ° C. of 3 kPa or less, and has a boiling point of 200 ° C. or less, and the total addition amount of the organic solvent is 1 to 50% by volume. The method for producing an organic EL element is characterized in that the surface tension of the hole transport ink is 40 mN / m or less.

  According to a second aspect of the present invention, there is provided a method for producing an organic EL device according to the first aspect, further comprising a reduced-pressure drying step after the transfer of the hole transport layer.

  The invention according to claim 3 is characterized in that the contact angle with respect to the photosensitive resin relief plate used in the relief printing method of the hole transport ink is 10 ° or more and 50 ° or less. It was set as the manufacturing method.

  In the method of manufacturing an organic EL device including a step of forming a hole transport layer by transferring ink by a relief printing method, there is no defect or unevenness by forming a uniform hole transport layer without ink repelling or the like. An organic EL device was obtained.

  The embodiment of the present invention will be described by taking as an example the case of producing a passive matrix type organic EL display panel. However, the present invention is not limited to these. A schematic diagram of a cross section of the organic EL display panel of the present invention is shown in FIG.

The organic EL element in the organic EL display panel is formed on the translucent substrate 1. As the translucent substrate 1, a glass substrate or a plastic film or sheet can be used. If a plastic film is used, a polymer EL element can be produced by winding, and a display panel can be provided at a low cost. As the plastic, for example, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate and the like can be used. In addition, these films have a barrier layer made of a metal oxide such as silicon oxide that exhibits water vapor barrier property and oxygen barrier property, oxynitride such as silicon nitride, polyvinylidene chloride, polyvinyl chloride, saponified ethylene-vinyl acetate copolymer. Is provided as necessary.

  A pixel electrode 2 patterned as an anode is provided on the translucent substrate. As the material of the pixel electrode 2, transparent electrode materials such as ITO (indium tin composite oxide), IZO (indium zinc composite oxide), tin oxide, zinc oxide, indium oxide, and aluminum oxide composite oxide can be used. ITO is preferred because of its low resistance, solvent resistance, transparency, and the like. ITO is formed on the light-transmitting substrate by sputtering, and is patterned by photolithography to form line-shaped pixel electrodes 2.

  After the line-shaped pixel electrode 2 is formed, the partition wall 3 is formed by a photolithography method using a photosensitive material between adjacent pixel electrodes. More specifically, a step of applying a photosensitive resin composition to a substrate, a step of pattern exposure, development, and baking to form a partition pattern, and a step of applying light irradiation to the partition pattern to make it hydrophilic. Have at least.

  The photosensitive material for forming the partition wall may be either a positive resist or a negative resist, and may be a commercially available one, but it must 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 include polyimide, acrylic resin, novolac resin, and fluorene, but the present invention is not limited thereto. Further, for the purpose of improving the display quality of the organic EL element, a light shielding material may be included 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.

  In the step of irradiating the partition pattern with light to make it hydrophilic, the partition portion and the anode portion are made hydrophilic by irradiating ultraviolet rays or the like from the upper surface of the substrate. The light to be irradiated is preferably an ultraviolet ray generally used for ultraviolet cleaning such as a hydrophilic treatment, and an ultraviolet irradiation treatment with an ultrahigh pressure mercury lamp, a high pressure mercury lamp, a metal halide lamp or the like is preferred. In addition, it is preferable that this process is performed immediately before forming the hole transport layer 4.

  The partition wall 3 in the present invention desirably has a thickness in the range of 0.5 μm to 5.0 μm. By providing the partition wall 3 between adjacent pixel electrodes, it is possible to suppress the spread of the hole transport ink printed on each pixel electrode and to prevent occurrence of a short circuit from the edge of the transparent conductive film. If the partition walls are too low, the effect of preventing a short circuit may not be obtained, so care must be taken.

Further, for example, in the passive matrix type organic EL display panel, when the partition 3 is provided between the pixel electrodes, the cathode layer is formed by directing the partition. When the cathode layer is formed in such a manner as to straddle the partition wall, if the partition wall 3 is too high, the cathode layer is disconnected, resulting in a display defect. When the height of the partition wall 3 exceeds 5.0 μm, the cathode is easily disconnected.

  After the partition wall 3 is formed, the hole transport layer 4 is formed. In the present invention, the hole transport ink for forming the hole transport layer 4 is preferably a water-soluble ink and has a surface tension of 40 mN / m or less. More preferably, it is 35 mN / m or less. This is because when the surface tension is larger than 40 mN / m, the hole transport ink generates pinholes and repellency on the substrate.

  As described above, the method of setting the surface tension to 40 mN / m or less is preferably a method by adding at least one kind of solvent other than water. The use of a surfactant makes it easy to create a non-uniform film during film formation, but the surfactant remains on the hole transport layer film even after drying, and therefore poor adhesion with the laminated layer This is because it may cause deterioration of characteristics and life.

  The solvent added to the hole transport ink can be mixed at a ratio of at least 20% by volume with respect to water, and the vapor pressure of the organic solvent at 20 ° C. is desirably 3 kPa or less. When the vapor pressure is greater than 3 kPa, when the water-soluble hole transport ink is formed on the substrate, only the solvent component evaporates prior to the solvent water, and the coating film causes uneven drying. This is a problem. The boiling point of the organic solvent added to the hole transport ink is preferably 200 ° C. or less. More preferably, it is 180 degrees C or less. This is because when the boiling point is higher than 200 ° C., heating at 200 ° C. or more is necessary to sufficiently volatilize the organic solvent, and the hole transport material causes thermal deterioration, leading to deterioration of device characteristics. Further, when the heating is insufficient, the solvent remains in the film. However, the residual solvent is a problem that leads to deterioration of characteristics and a decrease in life.

  Solvents that satisfy the above conditions include 1-propanol, ethylene glycol, propylene glycol, methyl cellosolve, ethyl cellosolve, butyl cellosolve, diethyl cellosolve, methyl cellosolve, diglyme, propylene glycol monoethyl ether, propylene glycol monomethyl ether, Examples include, but are not limited to, ethylene glycol monomethyl ether acetate, N, N-dimethylformamide, dimethyl sulfoxide, pyridine, 2-aminoethanol, and ethyl lactate.

  An organic solvent which can be mixed at a ratio of 20% by volume or more with respect to these waters, has a vapor pressure at 20 ° C. of 3 kPa or less, and a boiling point of 200 ° C. or less has an addition amount of 1 to the ink. It is preferable that it is -50 volume%. This is because if the amount is less than 1% by volume, the effect of lowering the surface tension due to the addition of the solvent cannot be sufficiently expected. If the amount added is more than 50%, the risk that the hole transport material aggregates in the ink increases.

  Solvents that are added to the hole transport ink and dissolve or disperse the hole transport material include, for example, ketones such as acetone, methyl ethyl ketone, methyl isobutyl ketone, methanol, ethanol, isopropanol, polyethylene glycol, in addition to the solvents mentioned above. And solvents such as alcohols such as glycerin, ethyl acetate, butyl acetate, isopropyl acetate, cellosolve, carbitol, and the like.

As the above hole transport ink, poly (3,4-ethylenedioxythiophene) (PEDOT) is particularly preferable from the viewpoint of conductivity and hole transportability. This material is dissolved or dispersed in a solvent to form a hole transport material ink, which is formed using the relief printing method of the present invention. The volume resistivity of the formed hole transport layer is preferably 1 × 10 ⁶ Ω · cm or less from the viewpoint of luminous efficiency.

If necessary, surfactants, antioxidants, viscosity modifiers, UV absorbers, etc. may be added to the hole transport ink. is necessary.

  FIG. 2 shows a schematic diagram of a relief printing apparatus when pattern printing is performed by a relief printing method on a substrate to be printed on which a pixel electrode and a partition wall are formed using a hole transport ink made of a hole transport material. This manufacturing apparatus has a plate cylinder 18 on which a plate 16 provided with an ink tank 10, an ink chamber 12, an anilox roll 14, and a relief plate is mounted. An organic luminescent ink diluted with a solvent is accommodated in the ink tank 10, and hole transport ink is fed into the ink chamber 12 from the ink tank 10. The anilox roll 14 is provided so as to be rotatable with respect to the ink supply section of the ink chamber 12.

  As the anilox roll 14 rotates, the ink layer 14a of the hole transport ink supplied to the anilox roll surface is formed with a uniform film thickness. This ink layer is transferred to the convex portion of the plate 16 mounted on the plate cylinder 18 that is driven to rotate in the vicinity of the anilox roll. On the flat table 20, the substrate to be printed 24 on which the transparent electrodes and the partition walls are formed is transported to a printing position by the convex portion of the plate 16 by a transport means (not shown). And the ink in the convex part of the plate 16 is printed on the substrate 24 to be printed, and if necessary, a hole transport layer is formed on the substrate to be printed through a drying process.

  The photosensitive resin relief plate used for this relief plate was a water development type. The photosensitive resin plate includes a solvent development type in which the developer used when developing the exposed resin plate is an organic solvent and a water development type in which the developer is water. The solvent development type tends to be resistant to water-based inks, and the water development type tends to be resistant to organic solvent-based inks. Any resin relief can be used.

  The contact angle between the resin relief printing plate produced here and the hole transport ink is preferably 10 ° or more and 50 ° or less. The contact angle between the resin relief printing plate and the hole transport ink is not determined only by the surface tension of the hole delivery ink, but varies depending on the combination with the resin relief printing plate. Generally, when the ink surface tension is lowered, the contact angle tends to decrease. Here, if the contact angle between the resin relief printing plate and the hole transporting ink is lower than 10 °, it is not preferable because the hole transportation ink causes a printing defect such as a portion where the hole transportation ink wets and spreads to the recesses on the resin relief printing plate. Also, if the contact angle is higher than 50 °, when ink is transferred from the anilox roll to the resin relief plate, the hole transport ink on the resin relief plate will not spread and spread, so that a moire pattern can be seen after the substrate transfer, It is not preferable because it occurs.

  The hole transport ink is printed on the substrate 1 on which the partition walls 3 are formed by the above-described relief printing method to form the hole transport layer 4, and after the hole transport layer 4 is baked, the process proceeds to the next step.

  Here, it is preferable to dry under reduced pressure immediately after forming the hole transport layer by letterpress printing. This is because the solvent component quickly evaporates by drying under reduced pressure, and drying unevenness does not occur. This is because if there is no vacuum drying step, drying unevenness may occur due to a slight change in the drying state in the plane due to the influence of room temperature, humidity, or airflow.

  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 the firing is insufficient.

  After the hole transport layer 4 is formed, an organic light emitting layer is formed. The organic light emitting layer is a layer that emits light by passing an electric current, and the organic light emitting material forming the organic light emitting layer 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, Examples thereof include 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. In addition, a surfactant, an antioxidant, a viscosity modifier, an ultraviolet absorber and the like may be added to the organic light emitting ink as necessary.

  As a method for forming the organic light emitting layer, in addition to the relief printing method of the present invention, a pattern can be formed by an ink jet method, an intaglio offset printing method, a relief inversion offset printing method, or the like. In addition, when using the relief printing method of this invention, the resin relief plate suitable for organic luminescent ink can be used, and the water-development type photosensitive resin relief plate is especially suitable.

  After the organic light emitting layer 5 is formed, the cathode layer 6 is formed in a line pattern orthogonal to the pixel electrode line pattern. As the material of the cathode layer 6, a material according to the light emitting characteristics of the organic light emitting layer can be used. For example, a simple metal such as lithium, magnesium, calcium, ytterbium or aluminum or a stable metal such as gold or silver can be used. An alloy etc. are mentioned. Alternatively, a conductive oxide such as indium, zinc, or tin can be used. Examples of the method for forming the cathode layer include a method using a vacuum vapor deposition method using a mask.

  The organic EL device of the present invention has a structure in which a hole transport layer and an organic light emitting layer are laminated from the anode layer side between a pixel electrode which is an anode and a cathode layer. In addition to the transport layer and the organic light emitting layer, a layered structure in which layers such as a hole blocking layer, an electron transport layer, and an electron injection layer are selected as necessary can be employed. Moreover, when forming these layers, the formation method similar to a light emitting layer can be used.

  Finally, in order to protect these organic EL constituents from external oxygen and moisture, the organic EL display panel can be obtained by hermetically sealing with a glass cap 7 and an adhesive 8. Moreover, when a translucent board | substrate has flexibility, you may seal using a sealing agent and a flexible film.

  Examples of the present invention will be described. A pixel electrode is formed by forming an ITO (indium-tin oxide) thin film on a 1.8 inch diagonal glass substrate by sputtering, and patterning the ITO film by photolithography and etching with an acid solution. did. The line pattern of the pixel electrode was a pattern in which a line width of 136 μm, a space of 30 μm, and 192 lines were formed in about 32 mm square.

Next, the partition was formed as follows. A positive type photosensitive polyimide Photo Nice DL-1000 manufactured by Toray Industries, Inc. was spin-coated on the glass substrate on which the pixel electrode was formed. The spin coating conditions were 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 1.5 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. Ultraviolet irradiation was performed for 3 minutes with a UV / O3 cleaning device manufactured by Oak Seisakusho.

  Next, as a hole transport ink, Vitron CH-8000 60% by volume, ultrapure water 20% by volume, 1-propanol 20% by volume were mixed and prepared to obtain an ink. 1-propanol alone has a vapor pressure at 20 ° C. of 1.87 kPa, a boiling point of 97.2 ° C., a surface tension of 23.7 mN / m, and hydration properties are freely mixed. When the viscosity was measured using this aqueous solution of PEDOT, it was 17.5 mPa · s, and the surface tension was 32.2 mN / m. At this time, the contact angle between the hole transport ink and the resin relief printing plate was 23 °. A hole transport layer was formed between the partition walls using a relief printing method using the above ink. In addition, as a pretreatment, the substrate before printing was irradiated with ultraviolet rays for 3 minutes using a UV / O3 cleaning device manufactured by Oak Manufacturing. After printing, vacuum drying was performed at 30 ° C. for 5 minutes, and then the hole transport layer was baked in the atmosphere at 200 ° C. for 30 minutes to form a hole transport layer. The film thickness of the hole transport layer at this time was 50 nm. The patterning state was confirmed with respect to the formed positive hole transport layer.

  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. Was printed by letterpress printing. The thickness of the organic light emitting layer after printing and drying was 80 nm.

  A cathode layer made of Ca and Al was formed thereon by mask vapor deposition using a resistance heating vapor deposition method in a line pattern orthogonal to the pixel electrode line pattern. Finally, in order to protect these organic EL constituents from external oxygen and moisture, they were hermetically sealed using a glass cap and an adhesive to produce an organic EL display panel.

  In the periphery of the display portion of the obtained organic EL display panel, there are an anode-side extraction electrode and a cathode-side extraction electrode connected to each pixel electrode, and these were obtained by connecting them to a power source. The lighting display of the organic EL display panel was confirmed, the light emission state was checked, and the lifetime at which the initial luminance was halved was measured.

  A hole transport ink was prepared in the same manner as in Example 1 except that 60% by volume of Vitron CH-8000, 20% by volume of ultrapure water, and 20% by volume of butyl cellosolve were mixed and prepared as an ink. In addition, butyl cellosolve has the property that the vapor pressure at 20 ° C. is 0.8 kPa, the boiling point is 170.2 ° C., the surface tension is 27.4 mN / m, and the hydration property is freely mixed. When the viscosity was measured using this PEDOT aqueous solution, it was 19.1 mPa · s and the surface tension was 27.9 mN / m. At this time, the contact angle between the hole transport ink and the resin relief printing plate was 19 °.

This example is Example 1 for comparison.
A hole transport ink was prepared in the same manner as in Example 1 except that 60% by volume of Vitron CH-8000, 20% by volume of ultrapure water, and 20% by volume of ethanol were mixed, prepared, and used as an ink. Ethanol alone has the properties of a vapor pressure of 5.9 kPa at 20 ° C., a boiling point of 78.3 ° C., a surface tension of 22.5 mN / m, and a hydration property that can be freely mixed. When the viscosity was measured using this aqueous solution of PEDOT, it was 17.5 mPa · s, and the surface tension was 33.4 mN / m. At this time, the contact angle between the hole transport ink and the resin relief printing plate was 22 °.

  This example is Example 2 for comparison.

  A hole transport ink was prepared in the same manner as in Example 1, except that 60% by volume of Vitron CH-8000, 20% by volume of ultrapure water, and 20% by volume of glycerin were mixed and prepared as an ink. In addition, glycerin alone has a vapor pressure of 0.0003 kPa at 20 ° C., a boiling point of 290.0 ° C., a surface tension of 63.3 mN / m, and a hydration property that is freely mixed. When this aqueous solution of PEDOT was used, the surface tension was 67.9 mN / m. At this time, the contact angle between the hole transport ink and the resin relief printing plate was 35 °.

This example is Example 3 for comparison.
It was produced in the same manner as in Example 1 except that Vitron® CH-8000 (45% by volume) and 1-propanol (55% by volume) were mixed and prepared as the hole transport ink. When the viscosity was measured using this aqueous solution of PEDOT, it was 21.1 mPa · s and the surface tension was 25.3 mN / m. At this time, the contact angle between the hole transport ink and the resin relief printing plate was 21 °.

  Table 1 shows the evaluation results of the pattern shapes of the hole transport layers in Examples 1 and 2 and Comparative Examples 1, 2, and 3, and the evaluation results of the display state and lifetime of the produced organic EL elements.

  As an evaluation method, the pattern shape of the hole transport layer was confirmed by visual inspection to confirm repelling and the like. Moreover, the obtained organic EL element was made to emit light, and observation of unevenness and measurement of a lifetime at which the initial luminance was reduced by half were performed.

It is a schematic diagram of the structure of the example of the organic EL element in the organic EL panel concerning this invention. It is the schematic of the relief printing apparatus in this invention.

Explanation of symbols

1: translucent substrate 2: pixel electrode 3: partition wall 4: hole transport layer 5: organic light emitting layer 6: cathode layer 7: glass cap 8: adhesive 10: ink tank 12: ink chamber 14: anilox roll 14a: Ink layer 16: Plate 18: Plate cylinder 20: Flat table 24: Printed substrate

Claims (3)

A method for producing an organic EL device comprising at least a step of forming a partition pattern on a transparent substrate and a step of forming a hole transport layer by transferring a hole transport ink to a region surrounded by the partition by a relief printing method The hole transport ink is a water-soluble ink, can be mixed at a ratio of 20% by volume or more with respect to at least one kind of water, and the vapor pressure at 20 ° C. is 3 kPa or less, and It comprises an organic solvent having a boiling point of 200 ° C. or less, the total addition amount of the organic solvent is 1 to 50% by volume, and the surface tension of the hole transport ink is 40 mN / m or less. Manufacturing method of organic EL element.   The method for producing an organic EL device according to claim 1, further comprising a reduced-pressure drying step after the transfer of the hole transport layer.   2. The method for producing an organic EL device according to claim 1, wherein the contact angle of the hole transport ink with respect to the photosensitive resin relief plate used in the relief printing method is from 10 ° to 50 °.

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