JP2007095520A - Organic electroluminescent element and its manufacturing method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide organic EL elements and their manufacturing methods wherein color mixing with neighboring pixels can be prevented when forming an organic light-emitting layer on a substrate by a letterpress printing method using an organic light-emitting ink, and moreover, unevenness in film-thickness can be suppressed when forming a positive hole transport layer or the like by a coating method such as a spin-coating method using ink in the organic EL element equipped with the substrate, a first electrode installed on this substrate, and a barrier rib between first electrodes, equipped with an organic light emitting medium layer including an organic light-emitting layer having different lighting colors on the first electrode, and equipped with a second electrode by pinching the organic light-emitting medium layer. <P>SOLUTION: This is the organic electroluminescent element in which the top part of the barrier rib between the first electrodes has a recessed part. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an organic electroluminescence element (hereinafter referred to as an organic EL element), in particular, a full-color organic EL element and a manufacturing method thereof, and further, an organic EL element in which an organic light emitting medium layer is formed by a wet film forming method and a manufacturing method thereof About.

  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, it is necessary to pattern the organic light emitting layer with high definition so that each pixel becomes red (R), green (G), and blue (B).

  Organic light-emitting materials that form the organic light-emitting layer include low-molecular materials and high-molecular materials. Generally, low-molecular materials are formed into thin films by resistance heating vapor deposition or the like, and then patterned using a fine pattern mask. In this method, there is a problem that the patterning accuracy is less likely as the substrate becomes larger.

Therefore, recently, a method of using a polymer material as an organic light emitting material, dispersing or dissolving the organic light emitting material in a solvent to form a coating solution, and forming a thin film by a wet coating method has been tried. As the wet coating method for forming a thin film, there are a spin coating method, a bar coating method, a protruding coating method, a dip coating method, and the like. However, it is considered difficult to form a thin film by a printing method that is good at coating and patterning.

  Further, among various printing methods, in organic EL elements and displays using glass as a substrate, a method using a hard plate such as a metal printing plate such as a gravure printing method is unsuitable, and an elastic rubber blanket. An offset printing method using, and a relief printing method using an elastic rubber plate or resin plate are also suitable. Actually, as an attempt by these printing methods, a method by offset printing (Patent Document 1), a method by letterpress printing (Patent Document 2), and the like have been proposed.

  On the other hand, the polymer organic light-emitting material has poor solubility in water and alcohol solvents, and in order to form a coating liquid (hereinafter referred to as ink), it is necessary to dissolve and disperse using an organic solvent. Toluene, xylene and other organic solvents are preferred. Therefore, the ink of organic light emitting material (hereinafter referred to as organic light emitting ink) is an ink of organic solvent.

  However, a rubber blanket used for offset printing has a problem that it is easily swollen or deformed by an organic solvent such as toluene or xylene. The types of rubber used in blankets vary from olefin rubber to silicone rubber, but none of these rubbers are resistant to toluene, xylene or other solvents and are prone to swelling and deformation. Not suitable for printing luminescent inks.

  In addition, the relief printing method using an elastic relief plate includes a flexographic printing method using a rubber plate and a resin relief plate method using a resinous plate. Among these, a method using a water development type resin relief plate is used. If present, it is highly resistant to toluene, xylene, and other organic solvents, and can be used for printing organic light-emitting inks.

  For the reasons described above, a water-developing type resin relief printing plate is used as a method for printing organic light-emitting ink composed of toluene, xylene and other aromatic organic solvents on a hard base material such as a glass substrate. The letterpress printing method is optimal. However, as a problem of the relief printing method, when ink is pressed against the substrate from the convex portion of the plate, a phenomenon that the ink is crushed and spreads out easily occurs. As a result, the line width of the printed material actually printed becomes wider than the line width of the plate, but the line width is actually widened even in the printing of the organic light emitting ink.

  In the case of organic light-emitting inks, due to both the problem of solubility of organic light-emitting materials and the necessity of forming a thin film, the ink solid content concentration has to be lowered to around 1%, and the ink viscosity is low. Therefore, the ink tends to spread more easily.

  In anticipation of these, it is conceivable that the line width of the plate is narrowed in advance, but the line width itself for forming the pixels of the organic EL display is originally thin, about 40 to 120 μm, and a plate with a thinner line width than that. Forming is more difficult.

JP 2001-93668 A JP 2001-155858 A

  In the formation of an organic light emitting layer using an ink typified by a relief printing method, there is a problem that the line width of the printed body tends to be wider than the line width of the plate. When the patterned first electrode is formed on the substrate and the organic light emitting layer is printed on the first electrode, if the organic light emitting ink spreads to the adjacent first electrode, a different emission color is generated. This causes color mixing with the organic light emitting layer, and causes uneven color in the display.

  In addition, in order to prevent color mixing due to the spread of ink, when an extremely high partition wall is provided, a film in the vicinity of the partition wall is formed when a hole transport layer or the like is formed on the entire surface of the organic EL element by a spin coat method or the like. There is also a problem that the thickness becomes large and the film thickness tends to be nonuniform.

  Accordingly, an object of the present invention is to provide an organic EL element capable of preventing color mixture to adjacent pixels when an organic light emitting layer is formed on a substrate by a relief printing method using an organic light emitting ink, and a method for manufacturing the same. . Another object of the present invention is to provide an organic EL device capable of suppressing unevenness in film thickness in the vicinity of a partition wall when a hole transport layer or the like is formed by a coating method such as spin coating using ink, and a method for producing the same. And

  In order to solve the above-mentioned problems, the present inventors have examined the shape of the partition walls and found that the following means are effective.

  The invention according to claim 1 of the present invention includes a substrate, a first electrode provided on the substrate, a partition between the first electrodes, and an organic light emitting layer having a different emission color on the first electrode. An organic electroluminescence device comprising an organic light-emitting medium layer, and a second electrode sandwiching the organic light-emitting medium layer, wherein the top of the partition wall has a recess, and did.

  The invention according to claim 2 provides the organic electroluminescent element according to claim 1, wherein the height of the partition wall is in the range of 0.3 μm to 1.0 μm.

  In the invention according to claim 3, an organic light emitting medium layer forming material is dissolved or dispersed in a solvent to form an ink, and at least one of the organic light emitting medium layers is formed by a wet film forming method using the ink. A method for producing an organic electroluminescent element according to claim 1 or claim 2 is provided.

  The invention according to claim 4 is characterized in that an organic light emitting material is dissolved or dispersed in a solvent to form an ink, and the organic light emitting layer is formed by a relief printing method using the ink. It was set as the manufacturing method of the organic electroluminescent element of claim | item 2.

  According to the present invention, when the top of the partition wall has a recess, the recess prevents the ink from entering the adjacent patterned first electrode when forming an organic light emitting layer having a different emission color. Thus, it was possible to obtain an organic EL element having no color mixture. In addition, the partition walls can be lowered, and when a hole transport layer or the like is formed by a coating method such as spin coating, it is possible to prevent the ink film thickness from increasing in the vicinity of the partition walls. An organic light-emitting device free from the above could be obtained.

  It shows about the organic EL element of this invention. FIG. 1 shows an explanatory cross-sectional view of the organic EL device of the present invention. (B) is an enlarged view of the partition wall portion of (a).

  Hereinafter, the present invention will be described with reference to the drawings. The present invention is applicable to both passive matrix type organic EL elements and active matrix type organic EL elements. 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.

  As shown in FIG. 1, the organic EL element of the present invention has a first electrode 2 on a substrate 1. In the case of the passive matrix system, the first electrode 2 has a stripe pattern. In the case of the active matrix method, the first electrode 2 has a pattern for each pixel. A partition wall 7 having a recess is provided between the first electrodes 2. When the first electrode is patterned by photolithography, the edge of the first electrode may have burrs. The burr at the edge of the first electrode causes a short circuit with the second electrode. Therefore, the partition wall 7 is preferably formed so as to cover the end portion of the first electrode.

  The organic EL element of the present invention has an organic light emitting medium layer on the first electrode 2 and in a region (pixel portion) partitioned by the partition walls 7. The organic light emitting medium layer may be composed of an organic light emitting layer alone, or may be composed of a laminated structure of an organic light emitting layer and a light emission auxiliary layer. FIG. 1 shows an organic light emitting medium layer composed of a laminated structure of a hole transport layer 3 which is a light emission auxiliary layer and organic light emitting layers (41, 42, 43). A hole transport layer 3 is provided on the first electrode, and a red organic light-emitting layer 41, a green organic light-emitting layer 42, and a blue organic light-emitting layer 43 are provided on the hole transport layer 3.

  Furthermore, a second electrode is disposed on the organic light emitting layer. In the case of the passive matrix method, the second electrode is provided in a stripe shape so as to be orthogonal to the first electrode having a stripe shape. In the case of the active matrix method, the second electrode is formed on the entire surface of the organic EL element.

  In the present invention, when the concave portion is provided in the central portion of the partition formed between each adjacent pixel electrode, the organic EL ink printed on the pixel electrode is over the partition and tries to protrude into the adjacent pixel. In addition, since a certain amount of ink can be stored in the concave portion, there is an effect of suppressing the protrusion of the ink. Excess ink 8 is trapped in the concave portion of the partition wall, and the ink does not enter the adjacent pixel. In the case of an active matrix organic EL element, the partition walls having the recesses may be formed only in the portions where the adjacent organic light emitting layers have different emission colors.

  In principle, the larger the volume of the partition wall recess, the greater the ink damming effect. However, the partition wall portion is a non-light emitting portion, and therefore the partition wall cannot be made so large. Usually, it is desired to keep the line width of the partition wall portion at most about 50%, desirably about 25% with respect to the line width of the light emitting layer portion. On the other hand, the width of the partition wall formed in the partition wall portion cannot be increased beyond a certain level because the width of the remaining partition wall portion becomes too narrow if it is increased, and it is limited to about 50% of the width of the partition wall portion. It is.

  Accordingly, when the volume of the partition surrounded by the first electrode and the volume of the partition formed on the partition is compared with that of the partition that is the portion where the organic light emitting ink is held immediately after printing, that is, before drying, the partition wall is formed. Even when the depth is maximized, the volume of the partition wall is at most about 25% of the volume on the pixel electrode surrounded by the partition wall and the pixel electrode holding the ink. Furthermore, as a result of the examination, it was found that there is a certain degree of ink damming effect if the volume of the recess is at least 5% or more of the volume of the pixel electrode surrounded by the partition wall and the pixel electrode, which is the part that holds the ink. .

  The height of the partition wall is preferably in the range of 0.3 μm to 1.0 μm. When the height of the partition wall is less than 0.3 μm, color mixing due to spreading of ink may not be prevented even if a recess is provided. In addition, if the height of the partition wall exceeds 1.0 μm, the film thickness in the vicinity of the partition wall becomes thick when the hole transport layer forming material is made into ink and formed by a spin coat method or the like, and the film thickness in the pixel is increased. You may stand unevenly.

  Next, the manufacturing method of the organic EL element according to the present invention will be described.

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

  For example, a glass substrate or a quartz substrate can be used. Further, it may be a plastic film or sheet such as polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate. Metal oxide thin film, metal fluoride thin film, metal nitride thin film, metal oxynitride thin film, or polymer resin film for the purpose of preventing moisture from entering the organic light emitting medium layer in these plastic films and sheets You may utilize what laminated | stacked these as a board | substrate.

  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) can be formed on these to form an active matrix 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 planarization layer may be formed on the TFT layer, and the TFT and the first electrode may be electrically connected via a contact hole.

  A first electrode is provided on the substrate. When the first electrode is used as an anode, the material is a metal composite such as ITO (indium tin composite oxide), IZO (indium zinc composite oxide), tin oxide, zinc oxide, indium oxide, zinc aluminum composite oxide. A single layer or a stacked layer of metal materials such as oxide, gold, platinum, and chromium can be used. As a method for forming the first electrode, a dry film forming method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method can be used.

  In addition, ITO is preferably used because of its low resistance, solvent resistance, and high transparency when the bottom mission method is adopted. ITO is formed on a glass substrate by a sputtering method, and is patterned by a photolithography method to form a first electrode.

  After forming the first electrode, a partition wall is formed by a photolithography method using a photosensitive material between adjacent pixel electrodes. The barrier ribs are formed between the first electrodes using a photolithographic method after first coating the entire surface with an insulating photosensitive material by a slit coating method or a spin coating method. The photosensitive material is roughly classified into a positive type and a negative type, and in the case of the negative type photosensitive material, a resin binder, a monomer, and a photopolymerization initiator are included. The positive photosensitive material contains a positive photosensitive resin. In the present invention, both negative and positive photosensitive materials can be used. Specific examples of the photosensitive material include polyimide, acrylic resin, and novolac resin.

  As an example of a method for forming a partition having a recess, FIG. 2 shows a cross-sectional view of a photomask pattern and a partition. FIG. 2A shows a photomask pattern (upper part of FIG. 2A) and a cross-sectional shape of the partition wall (lower part of FIG. 2A) when a positive photosensitive material is used. FIG. 2B shows a photomask pattern (upper part of FIG. 2A) and a sectional shape of the partition wall (lower part of FIG. 2A) when a positive photosensitive material is used. The photomask has a structure in which a light shielding material is patterned on a transparent base material such as glass, and includes a light transmitting portion 91 and a light shielding portion 92. As described above, by using a photomask having two adjacent line patterns, a partition wall having a recess can be formed. It can also be formed by a two-layer structure of partition walls. That is, the first layer is formed with a height obtained by subtracting the depth of the concave portion to be formed from the desired height of the partition without providing the concave portion, and the second layer is the same height as the depth of the concave portion to be formed. By forming a coating film with, and then forming a recess in the second layer by a photolithography method, a recess having a desired depth can be formed in a partition wall having a desired height.

  Next, an organic light emitting medium layer is formed. The organic light emitting medium layer may be composed of an organic light emitting layer alone, or an organic light emitting layer and a layer for assisting light emission such as a hole transport layer, a hole injection layer, an electron transport layer, and an electron injection layer. A laminated structure may be used. The hole transport layer, hole injection layer, electron transport layer, and electron injection layer are appropriately selected.

  The organic light emitting layer is a layer that emits light when an electric current is passed. Organic light-emitting materials formed by the organic light-emitting layer include 9,10-diarylanthracene derivatives, pyrene, coronene, perylene, rubrene, 1,1,4,4-tetraphenylbutadiene, tris (8-quinolato) aluminum complex, tris (4-methyl-8-quinolato) aluminum complex, bis (8-quinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8-quinolato) aluminum complex, tris (4-methyl-5-cyano-) 8-quinolate) aluminum complex, bis (2-methyl-5-trifluoromethyl-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, bis (2-methyl-5-cyano-8-quinolinolato) [4- (4-Cyanophenyl) phenolate] aluminum complex, Lis (8-quinolinolato) scandium complex, bis [8- (paratosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4-tetraphenylcyclopentadiene, poly-2,5-diheptyloxy-paraphenylene vinylene, etc. The low molecular weight light emitting material can be used.

  Further, coumarin phosphors, perylene phosphors, pyran phosphors, anthrone phosphors, polyphyrin phosphors, quinacridone phosphors, N, N′-dialkyl-substituted quinacridone phosphors, naphthalimide phosphors, A material obtained by dispersing a low molecular weight light emitting material such as an N, N′-diaryl-substituted pyrrolopyrrole-based fluorescent pair or a phosphorescent light emitter such as an Ir complex in a polymer can be used. As the polymer, polystyrene, polymethyl methacrylate, polyvinyl carbazole and the like can be used. Further, it may be a polymer light emitting material such as polyarylene, polyarylene vinylene, polyfluorene, polyphenylene vinylene, polyparaphenylene vinylene, polythiophene or polyspiro. In addition, a material obtained by dispersing or copolymerizing the low molecular material in these high molecular materials, or other existing light emitting materials can be used.

  As a material for the hole transport layer, metal phthalocyanines such as copper phthalocyanine and tetra (t-butyl) copper phthalocyanine and metal-free phthalocyanines, quinacridone compounds, 1,1-bis (4-di-p-tolylaminophenyl) Cyclohexane, N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1,1′-biphenyl-4,4′-diamine, N, N′-di (1-naphthyl) -N, Aromatic amine low molecular hole injection and transport materials such as N′-diphenyl-1,1′-biphenyl-4,4′-diamine, polyaniline, polythiophene, polyvinylcarbazole, poly (3,4-ethylenedioxythiophene) ) And polystyrene sulfonic acid and other polymer hole transport materials, polythiophene oligomer materials, and other existing hole transport materials It is possible to choose from.

  As a material for the electron transport layer, 2- (4-bifinylyl) -5- (4-t-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1-naphthyl)- 1,3,4-oxadiazole, an oxadiazole derivative, a bis (10-hydroxybenzo [h] quinolinolato) beryllium complex, a triazole compound, or the like can be used.

  Solvents that dissolve or disperse the organic light emitting material include toluene, xylene, acetone, hexane, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, 2-methyl- (t-butyl) Benzene, 1,2,3,4-tetramethylbenzene, pentylbenzene, 1,3,5-triethylbenzene, cyclohexylbenzene, 1,3,5-tri-isopropylbenzene and the like can be used alone or in combination. . Moreover, surfactant, antioxidant, a viscosity modifier, a ultraviolet absorber, etc. may be added to organic luminescent ink as needed.

  Solvents that dissolve or disperse the hole transport material and electron transport material include, for example, toluene, xylene, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, water, etc. Alternatively, a mixed solvent thereof can be used. In particular, water or alcohols are suitable.

  The organic light emitting medium layer is formed by a wet film forming method. When the organic light emitting medium layer has a laminated structure, it is not necessary to form all of the layers by the wet coat method. As the wet film forming method, there are coating methods such as a spin coating method, a die coating method, a dip coating method, a discharge coating method, a pre-coating method, a roll coating method, and a bar coating method. Moreover, you may utilize the printing method of a relief printing method and the inkjet printing method. In particular, when an organic light emitting layer is formed, it can be selectively applied to the pixel portion by a printing method. For this reason, it becomes possible to manufacture the organic EL element which can perform a color display by printing to each pixel the light emitting layer which light-emits in a mutually different color.

  In particular, the organic light emitting layer is preferably formed by a relief printing method. Unlike the ink jet method, the relief printing method transfers the ink so that the plate and the printing substrate are in contact with each other, so that the partition wall can be lowered. In the present invention, the letterpress used in the letterpress printing method is preferably a water development type resin letterpress. Examples of the water-developable photosensitive resin constituting the resin plate in the present invention include a type having a hydrophilic polymer and a monomer containing an unsaturated bond, a so-called crosslinkable monomer and a photopolymerization initiator as constituent elements. In this type, polyamide, polyvinyl alcohol, cellulose derivatives and the like are used as hydrophilic polymers. Examples of the crosslinkable monomer include methacrylates having a vinyl bond, and examples of the photopolymerization initiator include aromatic carbonyl compounds. Among these, a polyamide-based water-developable photosensitive resin is preferable from the viewpoint of printability.

  The printing apparatus used for forming the organic light emitting layer may be any relief printing apparatus that prints on a flat plate, but a printing machine as shown below is desirable. FIG. 3 shows a schematic diagram of the relief printing apparatus of the present invention. This manufacturing apparatus has a plate cylinder 18 to which an ink tank 10, an ink chamber 12, an anilox roll 14, and a resin relief plate 16 are attached. The ink tank 10 contains organic light-emitting ink diluted with a solvent, and the organic light-emitting ink is fed into the ink chamber 12 from the ink tank 10. The anilox roll 14 rotates in contact with the ink supply section of the ink chamber 12 and the plate cylinder 18.

  As the anilox roll 14 rotates, the organic light emitting ink 14a supplied from the ink chamber is uniformly held on the surface of the anilox roll, and then transferred to the convex portion of the resin relief plate 16 attached to the plate cylinder with a uniform film thickness. To do. Furthermore, the substrate to be printed is fixed on a slidable substrate fixing base, and moved to the printing start position while adjusting the position by the position adjustment mechanism of the plate pattern and the substrate pattern. The convex portion of the resin relief plate 16 further moves while contacting the substrate, and the ink is transferred by patterning to a predetermined position of the substrate 24 to be printed on the stage 20.

  In addition, by using the partition wall having a concave portion of the present invention, when organic light emitting medium layers other than the organic light emitting layer such as a hole transport layer are patterned by a wet film forming method using ink, the organic light emitting layer is used. The present invention can also be applied when forming by an inkjet method.

  Next, a second electrode is formed. When the second electrode is a cathode, a material having high electron injection efficiency is used as the material. 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 in contact with the light emitting medium, and Al or Cu having high stability and conductivity is laminated. And use. Or, 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, Yb, etc., which have low work function, and stable Ag, Al An alloy system with a metal element such as Cu is used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used.

  As a method for forming the second electrode, a dry film formation method such as a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, or a sputtering method can be used. The thickness is preferably about 10 nm to 1 μm. In the present invention, the first electrode can be a cathode and the second electrode can be an anode.

  And it seals through an adhesive agent with a glass cap etc., and prevents deterioration of the cathode and the light emitting medium layer due to moisture and oxygen.

  Examples of the present invention will be specifically described below. In this example (comparative example), an example of creating a passive matrix type organic EL display panel is shown. In the prepared panel, the ITO pattern formed on the substrate, that is, the line pattern of the first electrode, has a line width of 80 μm and a space of 40 μm, and the partition formed in the space part is 5 μm at each end of the adjacent first electrode. Since they are formed one by one, the partition walls have a width of 50 μm.

Example 1
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 first electrode was formed so that two surfaces could be taken. The line pattern of the pixel electrode per display surface was a pattern in which 1950 lines were formed with a line width of 80 μm and a space of 40 μm.

  In Example 1, the height of the partition formed between the pixel electrodes was 0.5 μm. The barrier ribs were formed by first coating the entire surface with an insulating photoresist material by a slit coating method, and then using the photolithography method so that the barrier ribs were patterned in a line shape in the space portion of the first electrode. At this time, a pattern was formed on the photomask in which a line-shaped recess was formed at the top of the partition wall, and at the same time, a recess at the top of the partition wall was formed. The recess was formed with a width of 20 μm and a depth of 0.5 μm. At this time, the volume of the concave portion was 25% of the volume of the ink holding portion surrounded by the partition wall and the pixel electrode.

  A polymer film made of PEDOT was formed thereon by spin coating as a hole transport layer. Furthermore, organic light-emitting inks of each color in which polyphenylene vinylene derivatives, which are red, green, and blue organic light-emitting materials, are dissolved in toluene so as to have a concentration of 1% are used. The light emitting layer was printed by a relief printing method. At this time, a 150 line / inch anilox roll and a water developing type photosensitive resin plate were used. The thickness of the organic light emitting layer after printing and drying was 80 nm.

  A second electrode made of Ca and Al was formed thereon by mask vapor deposition using a resistance overheating vapor deposition method in a line pattern orthogonal to the line pattern of the first 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 adhesive to produce an element panel for an organic EL display. In the peripheral part of the display part of the obtained panel, there are the extraction electrodes on the anode side and the cathode side connected to each pixel electrode, and the lighting display confirmation of the panel is performed by connecting these to the power source, and the light emission The state was checked.

(Example 2)
In Example 2, the height of the partition was 1 μm, and the recess of the partition was formed with a width of 20 μm and a depth of 0.2 μm. Adjustment of the depth of the recess was realized by forming two layers of photoresist. That is, the first layer is formed with a partition wall having a height of 0.8 μm without providing a recess, and the second layer is formed with a recess having a height of 0.2 μm, so that the total height is 1 μm and the depth of the recess is 0. A partition wall of 2 μm could be formed. The volume of the concave portion at this time was 5% of the volume of the organic EL ink holding portion surrounded by the partition wall and the pixel electrode. Otherwise, a panel was prepared in the same manner as in Example 1.

(Example 3)
In Example 3, the partition wall height was 0.3 μm, and the partition wall recess was formed with a width of 20 μm and a depth of 0.2 μm. The recess was formed in the same manner as in Example 1. The volume of the concave portion at this time is 25% of the volume of the organic EL ink holding portion surrounded by the partition walls and the pixel electrodes. Otherwise, a panel was prepared in the same manner as in Example 1.

Example 4
In Example 4, the partition wall height was 0.2 μm, and the partition wall recesses were formed with a width of 20 μm and a depth of 0.1 μm. The recess was formed in the same manner as in Example 1. Otherwise, a panel was prepared in the same manner as in Example 1.

(Comparative Example 1)
In Comparative Example 1, the partition wall height was 0.2 μm and the partition wall recess was not provided. Otherwise, a panel was prepared in the same manner as in Example 1.

(Comparative Example 2)
In Comparative Example 2, the partition wall height was 0.3 μm, and the partition wall recess was not provided. Other than that, a panel was prepared in the same manner as in Example 1.

(Comparative Example 3)
In Comparative Example 3, the partition wall height was 0.5 μm, and the partition wall recess was not provided. Otherwise, a panel was prepared in the same manner as in Example 1.

(Comparative Example 4)
In Comparative Example 4, the partition wall height was 0.8 μm, and the partition wall recess was not provided. Otherwise, a panel was prepared in the same manner as in Example 1.

(Comparative Example 5)
In Comparative Example 5, the partition wall height was 1.2 μm, and the partition wall recess was not provided. Otherwise, a panel was prepared in the same manner as in Example 1.

(Comparative Example 6)
In Comparative Example 6, the partition wall height was 2.0 μm and the partition wall recess was not provided. Otherwise, a panel was prepared in the same manner as in Example 1. .

  Table 1 shows the evaluation results of the color mixing rate of the organic EL panels prepared as in Examples 1 to 4 and Comparative Examples 1 to 6, and the evaluation results of the film thickness uniformity of the hole transport layer.

  The color mixture occurrence rate indicates the ratio of color mixture with respect to the total number of pixels. It confirmed with the optical microscope. Further, the film thickness uniformity of the hole transport layer was judged from the cross-sectional shape of the cross-sectional observation with a scanning electron microscope. Circle marks indicate good film thickness uniformity, triangle marks indicate areas where the film thickness is large in the vicinity of the partition wall in some pixel cross sections, and cross marks indicate film thicknesses in most pixel cross sections. It is confirmed that the thickness is increased in the vicinity of the partition wall.

  As can be seen from Comparative Examples 1 to 4, in the panel where the partition wall height is less than 1 μm, color mixing may occur, but even when the partition wall height is less than 1 μm as in Examples 1 to 3, By providing a recess in the partition wall, the occurrence of color mixing can be suppressed. However, color mixing was confirmed in Example 4. However, from the comparison with Comparative Example 1, the effect of the present invention was confirmed because the color mixture occurrence rate was reduced.

  Further, as can be seen from Comparative Examples 5 and 6, if the height of the partition wall exceeds 1.0 μm, no color mixing occurs even if there is no recess, but in this case the film thickness of the hole transport layer Unevenness is observed. Therefore, it is optimal that the height of the partition wall is in the range of 0.3 μm to 1.0 μm and the recess is provided in the partition wall.

Explanatory sectional drawing of the organic EL element of this invention. An explanatory sectional view of a photomask pattern and a partition. 1 is a schematic view of a relief printing apparatus of the present invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Board | substrate 2 1st electrode 3 Hole transport layer 41 Red organic light emitting layer 42 Green organic light emitting layer 43 Blue organic light emitting layer 7 Partition 8 Excess ink 91 Light transmission part 92 Light shielding part 10 Ink tank 12 Ink chamber 14 Anilox roll 14a Ink 16 Resin relief 18 Plate cylinder 20 Stage 24 Printed substrate

Claims (4)

A substrate, a first electrode provided on the substrate, a partition between the first electrodes, an organic light-emitting medium layer including an organic light-emitting layer having different emission colors on the first electrode, and the organic In the organic electroluminescence device comprising the second electrode with the luminescent medium layer interposed therebetween,
An organic electroluminescence element, wherein a top portion of the partition wall has a recess.   The organic electroluminescence device according to claim 1, wherein the height of the partition wall is in the range of 0.3 µm to 1.0 µm.   The organic light emitting medium layer forming material is dissolved or dispersed in a solvent to form an ink, and at least one of the organic light emitting medium layers is formed by a wet film forming method using the ink. Item 3. A method for producing an organic electroluminescence device according to Item 2.   3. The organic electroluminescent device according to claim 1, wherein the organic light emitting material is dissolved or dispersed in a solvent to form an ink, and the organic light emitting layer is formed by a relief printing method using the ink. Method.

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