JP2008140579A - Organic el element and its manufacturing method, and letterpress - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an organic EL element and an organic EL display in which a thick membrane of a hole transport layer is made possible, in which there is less light emission uneavenness, and which are superior in display quality in the organic EL display which is composed of at least a pixel electrode, a counter electrode, and an organic light-emitting medium layer including the hole transport layer and the organic light-emitting layer, and which makes the organic light emitting layer emit light by making a current flow into the organic light-emitting layer from both the electrodes. <P>SOLUTION: An insulating layer 3 is formed between the pixel electrodes 2 to which patterning is applied on a substrate, and in the case a hole transport ink in which a hole transport material is stably dissolved or dispersed in a medium is printed by letterpress on the pixel electrodes 2 between the insulating layers 3 from convex parts 32 of a letterpress printing 30, the convex parts 32 of the letterpress printing 30 are made to have a concave shape on their middle part. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an organic EL element used in an organic EL display panel or the like in which an organic light emitting layer is made of a polymer material, and a manufacturing method thereof, and more particularly to an organic EL element in which an organic light emitting layer is formed by a printing method and a manufacturing method thereof.

  An organic EL element is one in which an organic light emitting layer made of an organic light emitting material is formed between two opposing electrodes, and light is emitted by passing a current through the organic light emitting layer. The film thickness is important, 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.

  The organic light emitting material for forming the organic light emitting layer includes a low molecular material and a high molecular material. Generally, a low molecular material is formed into a thin film by a vacuum deposition method or the like, and is patterned using a fine pattern mask at this time. This method has a problem that the larger the substrate is, the less patterning accuracy is obtained. 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. An offset printing method has been proposed as a coloring method. (For example, refer to Patent Document 1).
As another method for forming a fine pattern, a relief printing method has been proposed. For example, Patent Document 2 discloses a technique for forming a semiconductor circuit pattern on a substrate.
JP 2001-93668 A JP 2002-217248 A

 In the organic EL display having the organic EL element having the above-described configuration, a method of generally applying a hole transport layer to the entire portion related to image formation, that is, a so-called solid coating method is generally used, and a coating method such as a spin coating method or a die coating method is used. 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.

The inventors of the present invention pattern a pixel electrode as an anode on a glass substrate, pattern an insulating layer between the pixel electrodes, apply a hole transport layer over the entire surface of the organic EL element, and perform organic light emission. In the passive matrix type organic EL device in which the layer was patterned and the cathode layer was patterned, it was confirmed that the current flowing between the patterned electrodes leaked and the luminous efficiency was lowered.
Therefore, in order to prevent this leakage current and improve luminous efficiency, it is necessary to pattern the hole transport layer only on the pixel electrode and not to provide the hole transport layer on the insulating layer. is there.

However, since the hole transport material forming the hole transport layer is made of a polymer material such as (3,4-polyethylenedioxythiophene) (PEDOT), the hole transport material is dissolved or stably dispersed in a solvent. In order to obtain a hole transport ink, it is necessary to reduce the concentration to about 2% because of both the problem of solubility and dispersibility of the polymer material and the necessity of forming a thin film.
When pattern printing is performed with a low-viscosity hole transport ink having a concentration of about 2%, a partition wall is necessary 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. Moreover, as a method of transferring the hole transport ink into the pixel electrode partitioned by the insulating layer, there are printing methods such as an ink jet method and a relief printing method.

However, the inkjet method is a method in which organic light-emitting ink is dropped from the inkjet nozzle to the printing site multiple 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. It is. Therefore, it is difficult for this ink jet method to transfer the ink to all the printing parts surrounded by the insulating layer, and there is a problem that printing omission is likely to occur especially at the edge of the pixel electrode.
In addition, a method for preventing printing omission in the ink jet method has 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, There is a problem that it is necessary to perform water treatment, and the number of processes increases accordingly. Further, the ink dropped on the water-repellent partition walls is piled up, but this has a problem in the uniformity and stability of the display panel because the film thickness uniformity in the pixels tends to deteriorate.

  On the other hand, in letterpress printing, in order to press the convex part of the letterpress against the printing site, the letterpress fills the space formed by the plate and the partition, so that the ink is laterally moved in the pixels surrounded by the partition. Strongly spread. Therefore, in general, printing omission at the edge of the pixel electrode hardly occurs. Moreover, letterpress printing is simple and has the advantage that the throughput is better than that of the ink jet method or the like. Therefore, the relief printing method is suitable for forming the hole transport layer from the hole transport ink.

As described above, in order to dissolve or stably disperse the hole transport material in a solvent to obtain a hole transport ink, it is necessary to reduce the concentration to about 2% due to the solubility problem of the polymer material. In order to form a desired film thickness using a low-concentration ink, it is necessary to reduce the number of anilox lines, and a fine pattern cannot be formed.
In addition, the luminous efficiency in the pixel plane needs to be uniform in the plane, and the thickness of the hole transport layer in the pixel plane needs to be uniform. However, it has been difficult to reliably form a hole transport layer having a uniform thickness in a fine region surrounded by the partition walls.

  Furthermore, in the case of conventional relief printing, ink may flow down to the relief if there is a scratch on the end of the relief after inking the anilox into the relief of the relief.

  Therefore, the present invention provides a method of forming a hole transport layer only on a pixel electrode patterned in an organic EL element, and can display images with good uniformity without a decrease in light emission efficiency due to leakage current. An object of the present invention is to provide an organic EL device and a method for manufacturing the same.

In order to achieve the above-described object, the present invention includes a pixel electrode, an insulating layer defining a light emitting region on the pixel electrode, and at least two layers stacked on the light emitting region and including a hole transport layer and an organic light emitting layer. A method of manufacturing an organic EL element comprising an organic light emitting medium layer including a counter electrode facing the pixel electrode through the organic light emitting layer, wherein the organic light emitting medium layer is formed using a relief plate in the light emitting region. An organic light-emitting medium layer forming step including a step of forming at least one layer constituting the convex portion, and the top portion of the convex portion of the relief plate is located on the extension of the side surface of the convex portion and constitutes the side surface of the top portion And a tip end surface for the top portion that is connected to the side surface for the top portion and forms a tip end surface of the convex portion, and is formed of a curved surface that is recessed in a direction opposite to the projecting direction of the convex portion. The concave portion is formed by the top end surface. Made is, in the organic light emitting medium layer forming step, the ink for forming the layer to be formed, characterized in that it is printed on the light emitting region from said recess of said top.
The organic EL device manufacturing method according to the present invention includes at least a pixel electrode, a counter electrode, an organic light emitting medium layer including a hole transport layer and an organic light emitting layer, and a current is passed from both electrodes to the organic light emitting layer. A method of manufacturing an organic EL element that emits light from an organic light emitting layer by forming an insulating layer between patterned pixel electrodes on a substrate, and dissolving or dispersing a hole transport material in a solvent by letterpress printing And a step of forming a hole transport layer by printing the positive hole transport ink from the convex portion of the relief printing onto the pixel electrode between the insulating layers, and having a concave portion at the top of the convex portion of the relief printing plate. The depth of the recess is 0.5 to 5.0 μm.

The organic EL device of the present invention comprises an organic light emitting medium layer including at least a pixel electrode, a counter electrode, a hole transport layer, and an organic light emitting layer. The organic light emitting layer emits light by passing a current from both electrodes to the organic light emitting layer. An organic EL element to be used is formed by using an insulating layer formed between patterned pixel electrodes on a substrate and a hole transport ink in which a hole transport material is dissolved or dispersed in a solvent by a relief printing method. And a hole transport layer formed by printing on the pixel electrode between the insulating layer and the shape of the convex portion of the relief plate has a concave portion at the top, and the depth of the concave portion is 0 .5 to 5.0 μm.
Moreover, in the above structure, the depth of the surface and trough part of the convex part of the said relief plate is 50 micrometers or more, It is characterized by the above-mentioned. The constituent material of the relief printing plate is made of a resin material, and its hardness is 18 to 75 (Shore D), 45 to 90 (Shore A). Furthermore, the viscosity of the hole transport layer ink is 5 to 80 mPa · s.

In general, the letterpress printing method refers to all printing methods using a plate whose image line portion has a convex shape, that is, a letterpress, in a broad sense. The letterpress printing method described in the present invention is a rubber plate or a resin plate. A printing method using a relief printing plate made of Also, among those skilled 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, letterpress printing method I will call it. 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.
Further, when the insulating layer has a lattice shape, the light emitting region has a window shape. In addition, when the insulating layer has a line shape, the light emitting region is a portion between the lines. In addition, the insulating layer may partially overlap the pixel electrode or may not overlap.

  According to the organic EL element and the method for producing the same of the present invention, a pixel electrode in which a hole transport ink in which a hole transport material is dissolved or stably dispersed in a solvent by a letterpress printing method is located between the convex part of the letterpress and the insulating layer And an ink film having a desired thickness can be transferred. Further, since the ink can be prevented from flowing into the relief, there is an effect that it is possible to obtain an organic EL element excellent in uniformity without defects.

Hereinafter, an example in which the embodiment of the present invention is applied to a passive matrix type organic EL display panel will be described. There are a passive matrix type and an active matrix type as a driving method of the organic EL element, but 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 electrodes are opposed to each other so as to be orthogonal to each other, and light is emitted at the intersection, whereas the active matrix method uses a so-called thin film transistor (TFT) substrate in which a transistor is formed for each pixel. Thus, the light is emitted independently for each pixel.
FIG. 1 is a sectional view showing the structure of an organic EL display panel according to an embodiment of the present invention.
The organic EL element in this organic EL display panel is formed on the substrate 1. When this organic EL display panel is a Potom emission type organic EL element that extracts light from the substrate side, it is necessary to use a transparent one as the substrate 1, but the top that extracts light from the opposite side of the substrate 1 is used. In the case of the emission method, the substrate 1 does not need to have translucency.
As the 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. In addition, as the plastic in that case, for example, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, polycarbonate, or 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. Provided as needed.

A pixel electrode 2 patterned as an anode is provided on the substrate 1. 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 substrate by a sputtering method and patterned by a photolithography method to form a line-shaped pixel electrode 2.
Then, after the line-shaped pixel electrode 2 is formed, the insulating layer 3 is formed by photolithography using a photosensitive material between the adjacent pixel electrodes 2.

  The insulating layer 3 in the present embodiment desirably has a thickness in the range of 0.5 μm to 5.0 μm. Further, by providing the insulating layer 3 between the adjacent pixel electrodes 2, the spread of the hole transport ink printed on each pixel electrode 2 is suppressed, and the hole transport layer 4 is formed on the insulating layer 3 when a display is formed. It is possible to prevent the occurrence of leakage current due to being in the area. If the insulating layer 3 is too low, ink spreading cannot be prevented and the hole transport layer 4 is formed on the insulating layer 3.

  For example, in a passive matrix type organic EL display panel, when the insulating layer 3 is provided between the pixel electrodes, the cathode layer 6 is formed with the insulating layer 3 orthogonally crossed. When the cathode layer 6 is formed so as to straddle the insulating layer 3 in this way, if the insulating layer 3 is too high, the cathode layer 6 is disconnected, resulting in a display defect. When the height of the insulating layer 3 exceeds 5.0 μm, disconnection of the cathode tends to occur.

  Further, the photosensitive material for forming the insulating layer 3 may be either a positive resist or a negative resist, and may be a commercially available one, but it must have insulating properties. In addition, when the partition does not have sufficient insulation, a current flows to the adjacent pixel electrode 2 through the partition and a display defect occurs. Specific examples thereof include polyimide, acrylic resin, novolac resin, and fluorene, but are 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 insulating layer 3 is applied using a coating method such as a spin coater, a bar coater, a roll coater, a die coater, or a gravure coater, and is patterned by a photolithography method. Alternatively, the insulating layer 3 may be formed using a gravure offset printing method, a reverse printing method, a flexographic printing method, or the like without using a photosensitive resin.

  After forming the insulating layer 3 as described above, the hole transport layer 4 is then formed. Examples of the hole transport material forming the hole transport layer 4 include polyaniline derivatives, polythiophene derivatives, polyvinylcarbazole (PVK) derivatives, poly (3,4-ethylenedioxythiophene) (PEDOT), and the like. These materials are dissolved or dispersed in a solvent to form a hole transport material ink, which is formed using the relief printing method according to the present embodiment. The volume low efficiency of the formed hole transport layer 4 is preferably 1 × 10 6 Ω · cm or less from the viewpoint of light emission efficiency.

  Examples of the solvent for dissolving or dispersing the hole transport material include toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropanol, ethylene glycol, polyethylene glycol, glycerin, ethyl acetate, and butyl acetate. , Isopropyl acetate, water and the like alone or a mixed solvent thereof. Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added as needed.

FIG. 2 shows an outline of a relief printing apparatus when pattern printing is performed on a substrate to be printed on which a pixel electrode 2 and an insulating layer 3 are formed using a hole transport ink made of a hole transport material.
As shown in the figure, the present 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 30 is mounted. The ink tank 10 contains hole transport ink diluted with a solvent, and the hole transport ink is fed into the ink chamber 12 from the ink tank 10. The anilox roll 14 is rotatably supported with respect to the ink supply part 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. The ink layer 14a is transferred to the convex portion 32 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 electrode and the insulating layer 3 are formed is conveyed to a printing position by the convex portion 32 of the plate 16 by a conveying means (not shown). And the ink in the convex part 32 of the plate 16 is printed on the printing substrate 24, and the hole transport layer 4 is formed on the printing substrate through a drying process as necessary.

  In this example, the photosensitive resin relief plate used for the relief plate 30 was of the 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. In general, solvent-developed types are resistant to water-based inks, and water-developed types tend to be resistant to organic solvent-based inks. Any resin relief plate 30 can be used.

Here, as shown in FIG. 3, the shape of the convex portion 32 of the resin relief plate 30 is a middle-concave shape so that the hole transport layer 4 can be formed on the pixel electrode 2 with the resin relief plate 30 to a desired film thickness. In other words, the shape is such that the concave portion 36 is formed on the top portion 32 </ b> A of the convex portion 32.
More specifically, the top portion 32A of the convex portion 32 of the relief plate 30 is positioned on the extension of the side surface of the convex portion 30 and the side surface 34 for the top portion constituting the side surface of the top portion 32A, and the direction opposite to the protruding direction of the convex portion 30 And a top end surface 35 that is connected to the top side surface 34 and forms the front end surface of the convex portion 30. A concave portion 36 that is recessed in the direction opposite to the protruding direction of the convex portion 32 is formed in the top portion 32A of the convex portion 32 by the top side surface 34 on both sides and the top front end surface 35 connected to the front ends thereof.
In the recess 36, the ratio (A / B) of the width B of the opening of the recess 36 to the height difference A of the recess 36 is preferably 1/200 to 1/2.
In the present specification, the width B of the opening of the recess 36 refers to the dimension of the recess 36 positioned between the tips of the top side surfaces 34 on both sides.
In the present specification, the height difference A of the recess 36 means a difference in height between the tip of the top side surface 34 and the bottom of the recess 36. In other words, the height difference A is substantially equal to the depth A of the recess 36.
The width B of the opening of the recess 36 is set according to the region surrounded or sandwiched by the insulating layer 3, but is 10 to 100 μm. By setting the width of the opening with respect to the height difference of the recess 36 to 1/200 to 1/2, the hole transport layer 4 having a uniform thickness is formed in a region surrounded or sandwiched by the insulating layer 3. be able to.
Here, it is desirable that the height difference A of the recess 36 is 0.5 to 5.0 μm. When the height difference A is 0.5 μm or less, the effect of increasing the film thickness is reduced, or the ink tends to flow into the relief. On the other hand, when the height difference A is 5.0 μm or more, the amount of transition from the anilox roll 14 is not stable, which causes unevenness. Further, by setting the height difference A to 0.5 to 5.0 μm, the hole transport layer 4 having a uniform thickness can be reliably formed in a region surrounded or sandwiched by the insulating layer 3. it can.
The top end surface 35 is formed as a curved surface that is recessed in the direction opposite to the protruding direction of the convex portion 32. Here, the curved surface refers to a continuously curved surface that is not a flat surface. Therefore, the concave portion 36 (the top end surface 35) may have a meniscus shape. Here, the meniscus shape refers to a shape having no corners in the recess 36. By adopting a meniscus shape, the ink film can be reliably transferred without ink remaining in the recess 36.

  Moreover, it is preferable that the difference of the convex part 32 of the relief plate 30 and the location in which the convex part 32 is not provided, ie, the difference of the depth of the part to which ink is not transferred, is 50 micrometers or more. If this difference is small, depending on the printing conditions, not only the convex portion 32 but also the portion where the convex portion 32 is not provided will come into contact with the substrate, and ink will be transferred to the extra portion, causing problems such as leakage. This is because it occurs.

  Next, the hardness of the resin relief plate 30 is preferably 45 to 90 degrees (Shore A) and 18 to 75 degrees (Shore D). This is because if the hardness is less than 45 degrees (Shore A), the margin for the printing pressure is narrow and the image line is twisted or crushed, making it very difficult to form a uniform pattern. If the angle is greater than 75 degrees (Shore D), the printing pressure appropriate for pattern formation becomes too high, and the substrate 1 or the insulating layer 3 is overloaded, and there is a risk of cracking, distortion, or scratches. It is.

  The viscosity of the hole transport layer 4 ink is preferably 5 to 80 mPa · s. In the relief printing method used in the present embodiment, the ink is first transferred from the anilox roll 14 onto the relief 30. However, at a viscosity of 80 mPa · s or more, the ink is transferred from the anilox roll 14 onto the relief 30. This is because the ink does not sufficiently level on the relief plate 30 and moire due to the anilox roll 14 may occur in the printing pattern.

  Next, after the formation of the hole transport layer 4 as described above, the organic light emitting layer 5 is formed. 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, 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.

  As a method for forming the organic light-emitting layer 5, in addition to the relief printing method according to the present embodiment, a pattern can be formed by an inkjet method, an intaglio offset printing method, a relief reverse printing method, or the like. In addition, when using the relief printing method by this Embodiment, the resin relief plate 30 suitable for organic luminescent ink can be used, and the water-development type photosensitive resin relief plate 30 is especially suitable.

  Next, after forming the organic light emitting layer 5 as described above, the cathode layer 6 is formed in a line pattern orthogonal to the line pattern of the pixel electrode 2. As the material of the cathode layer 6, those according to the light emission characteristics of the organic light emitting layer 5 can be used. For example, simple metals such as lithium, magnesium, calcium, ytterbium and aluminum and stable metals such as gold and silver can be used. And alloys thereof. Alternatively, a conductive oxide such as indium, zinc, or tin can be used. Examples of the method for forming the cathode layer 6 include a formation method by a vacuum vapor deposition method using a mask.

  The organic EL element of the present embodiment has a configuration in which the hole transport layer 4 and the organic light emitting layer 5 are laminated from the anode layer side between the pixel electrode 2 that is an anode and the cathode layer 6. In addition to the hole transport layer 4 and the organic light emitting layer 5, a layered structure in which a layer such as a hole block layer, an electron transport layer, and an electron injection layer is selected as necessary can be adopted between the cathode layers 6. The formation method of the present invention can also be used when forming these layers. Furthermore, the pixel electrode 2 can be a cathode and the counter electrode can be an anode.

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. In the case where the substrate has flexibility, sealing may be performed using a sealing agent and a flexible film.
(Example 1)

Next, examples of the present invention will be described.
Here, trial manufacture and measurement were performed for the following Examples 1 to 3 and Comparative Examples 1 to 4.
First, an ITO (indium-tin oxide) thin film is formed on a 300 mm square glass substrate by sputtering, and the ITO film is patterned by photolithography and etching with an acid solution. The pixel electrode 2 was formed so that two displays could be taken. The line pattern of the pixel electrode 2 per surface of the display was a pattern in which 1950 lines were formed with a line width of 40 μm and a space of 20 μm.

  Next, the insulating layer 3 was formed as follows. First, an acrylic photoresist material was spin coated on the glass substrate on which the pixel electrode 2 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 height of the insulating layer 3 was 1.5 μm. An insulating layer 3 having a line pattern was formed between the pixel electrodes 2 by photolithography using a photoresist material applied to the entire surface.

  Next, 80 parts by weight of Vitron AI-4083 as a PEDOT solution and 20 parts by weight of methyl cellosolve were mixed and prepared as a hole transport ink to prepare an ink having a viscosity of 15 mPa · s. As the plate material, a concave portion 36 is provided on the top 32A of the convex portion 32 of the relief plate 30 to form a middle concave shape, the height difference A is 1.0 μm, and the convex portion 32 and the convex portion 32 of the relief plate 30 are not provided. The plate making was performed so that the difference was 100 μm. The plate material had a hardness of 77 (Shore A). A hole transport layer 4 was formed between the insulating layers 3 by a relief printing method using the above ink and plate. An anilox roll of 180 lines / inch was used for printing, and after printing, the hole transport layer 4 was formed by drying in the atmosphere at 200 ° C. for 30 minutes. The film thickness at this time was 50 nm. Then, the patterning state of the formed hole transport layer 4 was confirmed.

  Next, an organic light-emitting ink in which a polyphenylene vinylene derivative, which is an organic light-emitting material, is dissolved in toluene so as to have a concentration of 1% is used, and the line pattern is aligned directly above the pixel electrode 2 sandwiched between the insulating layers 3. The organic light emitting layer 5 was printed by a relief printing method. At this time, an anilox roll of 150 lines / inch and a photosensitive resin plate of water development type were used. As a result, the film thickness of the organic light emitting layer 5 after printing and drying was 80 nm.

A cathode layer 6 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 line pattern of the pixel electrode 2. 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 part of the organic EL display panel obtained in this way, there are an extraction electrode on the anode side connected to each pixel electrode 2 and an extraction electrode on the cathode side. By connecting these to a power source, The lighting display of the obtained organic EL display panel was confirmed, and the light emission state was checked.
(Example 2)

The same procedure as in Example 1 was performed except that the convex portion 32 of the relief printing plate 30 for printing the hole transport layer 4 had a concave shape and the height difference A was set to 3.0 μm.
(Example 3)

  The same as Example 1 except that the height difference between the convex part 32 of the relief printing plate 30 for printing the hole transport layer 4 and the part where the convex part 32 is not provided was 60 μm.

Moreover, it produced on condition as follows as a comparative example.
[Comparative Example 1]
The same procedure as in Example 1 was performed except that the convex portion 32 of the relief printing plate 30 for printing the hole transport layer 4 had a concave shape and the height difference A was 8.0 μm.
[Comparative Example 2]
The same procedure as in Example 1 was performed except that the relief 30 having a height difference of 30 μm between the relief 30 for printing the hole transport layer 4 and the portion where the relief 32 was not provided was used.
[Comparative Example 3]
It was produced in the same manner as in Example 1 except that the hardness of the relief printing 30 of the relief printing method was changed to 25 (Shore A) in order to form the hole transport layer 4.
[Comparative Example 4]
As a hole transport ink, 10 parts by weight of polyethylene glycol was added to the ink prepared in Example 1 to prepare a hole transport ink. At this time, the viscosity of the ink was 95 mPa · s. A panel was produced using this ink in the same manner as in Example 1.

FIG. 4 shows the evaluation results of the line pattern shape of the hole transport layer 4 in Examples 1 to 3 and Comparative Examples 1 to 4 as described above and the evaluation result of the display state of the produced organic EL display.
As shown, it can be seen that better results are obtained with the example of the present invention than with the comparative example.

It is sectional drawing which shows the structure of the organic EL element in the organic EL panel by embodiment of this invention. It is sectional drawing which shows the outline | summary of the relief printing apparatus in embodiment of this invention. It is explanatory drawing of the convex part of a letterpress. It is the table | surface which contrasted and showed the measurement result of the pattern shape of the organic electroluminescent display obtained by the Example and comparative example of this invention, a leakage current, and the light emission state with Comparative Examples 1-4.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Substrate, 2 ... Pixel electrode, 3 ... Insulating layer, 4 ... Hole transport layer, 5 ... Organic light emitting layer, 6 ... Cathode layer, 7 ... Glass cap, 8 ... Adhesive, DESCRIPTION OF SYMBOLS 10 ... Ink tank, 12 ... Ink chamber, 14 ... Anilox roll, 14a ... Ink layer, 16 ... Plate, 18 ... Plate cylinder, 20 ... Flat bed, 24 ... Print substrate, 30 ... Letterpress, 32 ... convex, 36 ... concave.

Claims (15)

A pixel electrode; an insulating layer that defines a light emitting region on the pixel electrode; an organic light emitting medium layer that is stacked on the light emitting region and includes at least two layers of a hole transport layer and an organic light emitting layer; and the organic light emitter layer A method of manufacturing an organic EL element comprising a counter electrode facing the pixel electrode via
An organic light emitting medium layer forming step including a step of forming at least one layer constituting the organic light emitting medium layer using a relief plate in the light emitting region;
The top part of the convex part of the relief plate is formed by a side surface for the top part which is located on the extension of the side surface of the convex part and forms a side surface of the top part, and a curved surface which is recessed in a direction opposite to the protruding direction of the convex part. A top end surface that is connected to the side surface and forms a front end surface of the convex portion,
A concave portion is formed on the top portion of the convex portion by the top end surface.
In the organic light emitting medium layer forming step, ink for constituting the layer to be formed is printed from the concave portion of the top portion to the light emitting region.
The manufacturing method of the organic EL element characterized by the above-mentioned.   The step of forming at least one layer constituting the organic light emitting medium layer is a step of transferring the hole transport ink from a convex portion of a relief printing into the light emitting region to form the hole transport layer. Item 2. A method for producing an organic EL device according to Item 1.   3. The method of manufacturing an organic EL element according to claim 1, wherein the ratio (A / B) of the width B of the opening of the recess to the depth A of the recess is 1/200 to 1/2. .   4. The method of manufacturing an organic EL element according to claim 1, wherein the recess has a depth A of 0.5 to 5.0 μm. 5.   The method for manufacturing an organic EL element according to claim 1, wherein the recess has a meniscus shape.   6. The method for manufacturing an organic EL element according to claim 1, wherein a difference in height between the convex portion of the relief plate and a portion where the convex portion is not provided is 50 μm or more.   The organic EL according to any one of claims 1 to 6, wherein the constituent material of the relief printing plate is made of a resin material and has a hardness of 18 to 75 (Shore D) or 45 to 90 (Shore A). Device manufacturing method.    The method for producing an organic EL element according to claim 2, wherein the hole transport layer ink has a viscosity of 5 to 80 mPa · s.   An organic EL element formed by the manufacturing method according to claim 1. A letterpress used in letterpress printing,
The top part of the convex part of the relief plate is formed by a side surface for the top part which is located on the extension of the side surface of the convex part and forms a side surface of the top part, and a curved surface which is recessed in a direction opposite to the protruding direction of the convex part. A top end surface that is connected to the side surface and forms a front end surface of the convex portion,
A concave portion is formed on the top portion of the convex portion by the top end surface.
Letterpress characterized by that.   11. The relief printing plate according to claim 10, wherein the ratio (A / B) of the width B of the opening of the recess to the depth A of the recess is 1/200 to 1/2.   The relief plate according to claim 10 or 11, wherein a depth A of the recess is 0.5 to 5.0 µm.   The relief plate according to any one of claims 10 to 12, wherein the concave portion has a meniscus shape.   The relief plate according to any one of claims 10 to 13, wherein a difference in height between the projection portion of the relief plate and a portion where no projection portion is provided is 50 µm or more.   The relief printing plate according to any one of claims 10 to 14, wherein the relief printing plate is made of a resin material and has a hardness of 18 to 75 (Shore D) or 45 to 90 (Shore A).

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