JP2011198544A - Organic electroluminescent element and method of manufacturing the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic EL element excellent in emission efficiency, emission luminance, and life expectancy, by heating a substrate at organic film forming.SOLUTION: In the method of manufacturing the organic electroluminescent element provided with a first electrode formed on a substrate, an organic emission medium layer including an organic light-emitting layer made of at least low-molecule light-emitting materials formed on the first electrode, and a second electrode formed in opposition to the first electrode, the organic light-emitting layer is formed in a wet process, which is carried out as the substrate is heated.

Description

The present invention relates to an organic EL element utilizing an electroluminescence (hereinafter abbreviated as EL) phenomenon of an organic thin film, a method for manufacturing the organic EL element, and a display device.

An organic EL element has a structure in which an organic light emitting layer exhibiting at least an electroluminescence phenomenon is sandwiched between an electrode as an anode and an electrode as a second electrode, and a voltage is applied between the electrodes. This is a self-luminous element in which the organic light emitting layer emits light by injecting holes and electrons into the organic light emitting layer and recombining the holes and electrons in the organic light emitting layer.

Further, for the purpose of increasing luminous efficiency, a hole injection layer, a hole transport layer, an electron blocking layer, or between the organic light emitting layer and the second electrode are provided between the anode and the organic light emitting layer. A hole blocking layer, an electron transport layer, an electron injection layer, and the like are appropriately selected and provided. The organic light emitting layer and these hole injection layer, hole transport layer, electron block layer, hole block layer, electron transport layer, electron injection layer and the like are collectively referred to as a light emitting medium layer. Each layer of the light emitting medium layer is made of an organic material or an inorganic material. The organic light emitting layer is made of an organic material, and the organic light emitting layer also includes a low molecular weight material and a high molecular weight material.

Examples of the polymer material include a material obtained by dissolving a low-molecular light-emitting pigment in a polymer such as polystyrene, polymethyl methacrylate, and polyvinyl carbazole in an organic light-emitting layer, or a polyphenylene vinylene derivative (hereinafter abbreviated as PPV). Polymer phosphors such as polyalkylfluorene derivatives (hereinafter abbreviated as PAF) and polymer phosphors such as rare earth metals are used. These polymer materials are generally dissolved or dispersed in a solvent and formed into a film with a thickness of about 1 to 100 nm using a wet method such as coating or printing.

However, these polymer materials have fewer types than low-molecular materials, so the range of material selection is narrow, and many of the performances are inferior in terms of organic EL characteristics such as light emission luminance and lifetime.

Examples of using low molecular weight materials include, for example, copper phthalocyanine (CuPc) for the hole injection layer and N, N′-diphenyl-N, N′-bis (3-methylphenyl) -1 for the hole transport layer. , 1'-biphenyl-4,4'diamine (TPD), tris (8-quinolinol) aluminum (Alq3) for the organic light emitting layer, 2- (4-biphenylyl) -5- (4-tert-butyl for the electron transport layer -Phenyl) -1,3,4, -oxadizole (PBD) and LiF in the electron injection layer.

Each of the light emitting medium layers made of these low-molecular materials is generally about 0.1 to 200 nm in thickness, and mainly a vacuum deposition method such as a resistance heating method or a dry method (dry process) in a vacuum such as a sputtering method. Is formed. As described above, there are a wide variety of low molecular weight materials, and combinations thereof are expected to improve luminous efficiency, luminous luminance, lifetime, and the like.

Further, the low molecular weight material can be formed into a film by a wet process such as coating or printing by dissolving or dispersing in a solvent. Compared with vacuum deposition and sputtering, the wet process has the advantage that the film can be formed in the atmosphere and the equipment is inexpensive, and can be manufactured quickly and efficiently even when the size is increased. In the dry process, pinholes and foreign matter in the hole transport layer are also reflected in the organic light-emitting layer, and short circuits are likely to occur. In the wet process, pinholes and foreign matter in the hole transport layer are easily removed. The organic light-emitting layer can be coated to prevent defects such as short circuits and dark spots, and organic thin films formed using a wet process are less susceptible to crystallization and aggregation than vacuum evaporation. There is also an advantage.

JP 2004-127531 A JP 7-192874 A

However, it is difficult to form a uniform thin film by a wet process, and depending on the solvent and light emitting material used, uniform film formation may not be possible due to crystallization or aggregation of the light emitting material.

Therefore, Patent Document 1 proposes to provide a crystal prevention layer around the light emitting portion of the element, but this method cannot prevent crystals and aggregation occurring in the light emitting portion. Also, Patent Document 2 proposes to disperse a low molecular weight material in a polymer binder to prevent crystallization, but this method has limited materials that can be used, making it difficult to select materials.

The present invention has been made in view of the above problems, and an object of the present invention is to provide an organic EL element having excellent light emission efficiency, light emission luminance, and lifetime by heating a substrate when forming an organic film.

The invention according to claim 1 is a first electrode formed on a substrate, an organic light emitting medium layer including an organic light emitting layer made of at least a low molecular light emitting material formed on the first electrode, and the first And a second electrode formed to face the electrode, wherein the organic light emitting layer is formed by a wet process, and the wet process is performed while heating the substrate. This is a method for producing an organic electroluminescence element.

Invention of Claim 2 is a manufacturing method of the organic electroluminescent element of Claim 1 whose temperature which heats the said board | substrate is 80 to 120 degreeC.

The invention according to claim 3 is the method of manufacturing an organic electroluminescence element according to claim 2, wherein the wet process is any one of a coating method, an ink jet method, and a printing method.

The invention according to claim 4 is an organic electroluminescence element manufactured by the method for manufacturing an organic electroluminescence element according to any one of claims 1 to 3.

By heating the substrate during the formation of the organic light-emitting layer, the organic film can be formed, thereby preventing pinholes, dark spots, and current leaks. An organic EL element having excellent spread, luminous efficiency, luminous luminance, and lifetime can be obtained.

It is explanatory drawing which shows an example of the organic EL element of this invention.

Hereinafter, an example of the organic EL element according to the present invention will be described with reference to FIG. In particular, a bottom emission type organic EL element that extracts light from the organic light emitting layer from the substrate side on which the organic EL element is formed will be described. However, a top emission type organic light that extracts light from the organic light emitting layer from the sealing side is described. May be.

<Board>
The substrate 101 serves as a support for the printed body of the present invention. As the material of the substrate 101, any substrate can be used as long as it has an insulating property and excellent dimensional stability. For example, plastic films and sheets such as glass, quartz, polypropylene, polyethersulfone, polycarbonate, cycloolefin polymer, polyarylate, polyamide, polymethyl methacrylate, polyethylene terephthalate, polyethylene naphthalate, etc., or oxidation to these plastic films and sheets Metal oxides such as silicon and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride and aluminum nitride, metal oxynitrides such as silicon oxynitride, acrylic resins and epoxy resins Translucent base material with a single layer or laminated polymer resin film such as silicone resin or polyester resin, metal foil such as aluminum or stainless steel, sheet, plate, aluminum on the plastic film or sheet It can be used um, copper, nickel, stainless steel and metal film non-translucent substrate as a laminate of such. In particular, when a bottom emission type organic EL element is used as in the present invention, a translucent base material may be selected. A substrate made of these materials is preferably subjected to moisture-proofing treatment or hydrophobic treatment by forming an inorganic film or a fluororesin layer in order to prevent moisture from entering the organic EL element. In particular, in order to avoid intrusion of moisture into the organic light emitting medium, it is preferable to reduce the moisture content and gas permeability coefficient in the substrate.

The substrate 101 may be an active drive substrate on which a thin film transistor (TFT) is formed. When the printed body of the present invention is an active drive organic EL element, a planarization layer is formed on the TFT, and the lower electrode (first electrode 12) of the organic EL element is formed on the planarization layer. It is preferable that the TFT and the lower electrode are electrically connected via a contact hole provided in the planarization layer. By comprising in this way, the outstanding electrical insulation can be obtained between TFT and an organic EL element. The TFT and the organic EL element formed above the TFT are supported by a support. The support is preferably excellent in mechanical strength and dimensional stability. Specifically, the materials described above as the substrate can be used. As the thin film transistor provided on the support, a known thin film transistor can be used. Specifically, a thin film transistor mainly including an active layer in which a source / drain region and a channel region are formed, a gate insulating film, and a gate electrode can be given. The structure of the thin film transistor is not particularly limited, and examples thereof include known structures such as a staggered type, an inverted staggered type, a top gate type, a bottom gate type, and a coplanar type.

In addition, since a uniform organic light emitting layer can be formed in this invention, the organic EL element which concerns on this invention formed the 1st electrode and the 2nd electrode in strip shape, and the passive matrix drive type organic EL element formed so that it might mutually orthogonally cross Even as a light emitting element without using as a display.

<First electrode>
Specifically, as the first electrode 102, a composite oxide of indium and tin (hereinafter referred to as ITO), a composite oxide of indium and zinc (hereinafter referred to as IZO), tin oxide, zinc oxide, indium oxide, zinc as oxides. Although there are aluminum complex oxides, etc., ITO can be preferably used because of its low resistance, solvent resistance, transparency, etc., and it is formed on the substrate 101 by vapor deposition or sputtering. You can also. Alternatively, a precursor such as indium octylate or indium acetone can be formed on the base material by a coating pyrolysis method in which an oxide is formed by thermal decomposition. Alternatively, a metal such as aluminum, gold or silver deposited as a semi-transparent metal or an organic semiconductor such as polyaniline can be used, and the above materials may be a single layer or a laminate. In the case of a so-called bottom emission structure in which light is extracted from below, it is necessary to select a translucent material among the above materials. If necessary, a metal material such as copper or aluminum may be provided as an auxiliary electrode in order to reduce the wiring resistance of the first electrode 102.
The first electrode 102 may be patterned by etching as necessary, and the surface may be activated by UV treatment, plasma treatment, or the like.

<Partition wall>
The partition wall 105 is formed so as to partition a light emitting region corresponding to a pixel when the organic EL element according to the present invention is used as a pixel display element such as a display. In general, an active matrix drive type display device has a first electrode 102 formed for each pixel, and each pixel tries to occupy as wide an area as possible, so that the end of the first electrode 102 is covered. The most preferable shape of the partition wall is basically a lattice shape that divides the first electrode 102 by the shortest distance. In the present invention, the partition wall need not be formed.

As a method for forming the partition wall 105, as in the conventional method, an inorganic film is uniformly formed on a substrate, masked with a resist, and then dry-etched, or a photosensitive resin is laminated on the substrate. And a method of forming a predetermined pattern by photolithography. If necessary, a water repellent can be added, or plasma or UV can be irradiated to impart liquid repellency to the ink after formation.
A preferable height of the partition wall is 0.1 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 2 μm or less. If the height of the partition wall 105 exceeds 10 μm, the formation and sealing of the second electrode is hindered, and if it is less than 0.1 μm, the end portion of the first electrode 102 cannot be covered, or it is adjacent when the light emitting medium layer is formed. This is because they are short-circuited or mixed with pixels.

<Organic luminescent medium layer>
The organic light emitting medium layer 103 of the organic EL element in the present invention is composed of a plurality of functional layers, such as a hole injection layer, a hole transport layer, an organic light emitting layer, a hole blocking layer, Examples include an electron transport layer, an electron injection layer, a partition wall, and the like, and in order to obtain a light emitting effect, a laminated structure including at least an organic light emitting layer and one or more other layers is desirable.

FIG. 1 shows an embodiment of the organic EL device of the present invention. The organic light emitting medium layer is composed of five layers of a hole injection layer, a hole transport layer, an organic light emitting layer, an electron transport layer, and an electron injection layer. The layer configuration is arbitrary, and the effect of the present invention can be obtained as long as it has a laminated structure including at least an organic light emitting layer and one or more other layers. The thickness of each layer is arbitrary, but preferably 10 to 100 nm, and the total thickness of the organic light emitting medium layer is preferably 80 to 500 nm. Hereinafter, materials and methods for forming an organic light emitting medium layer will be described.

As the hole injecting material and the hole transporting material used for the hole injecting layer and the hole transporting layer, any material generally used as a hole transporting material may be used. Specifically, copper phthalocyanine, tetra Metal phthalocyanines such as (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, N'-diphenyl-1,1'-biphenyl-4 , 4'-diamine and other aromatic amine-based low-molecular hole injection and transport materials, polyaniline, polythiophene, polyvinylcarbazole, poly (3,4-ethylenedioxythiophene) and poly Polymer hole transport materials such as a mixture of Chirensuruhon acid, polythiophene oligomer _{materials, Cu 2 O, Cr 2 O} 3, Mn 2 O 3, FeOx (x~0.1), NiO, CoO, Pr 2 O 3 , Ag ₂ O, MoO ₂ , Bi ₂ O ₃ , ZnO, TiO ₂ , SnO ₂ , ThO ₂ , V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO _2, etc. The material can be selected from other existing hole transport materials, and can be formed by vacuum deposition or the like.

In addition, these materials are toluene, xylene, acetone, anisole, methyl anisole, dimethyl anisole, ethyl benzoate, methyl benzoate, mesitylene, tetralin, amylbenzene, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, A film can be formed by a wet process such as a printing method or spin coating by using it as a hole transport coating solution by dissolving or dispersing in ethyl acetate, butyl acetate, water or the like alone or in a mixed solvent.

The light emitting body used for the organic light emitting layer may be a low molecular light emitting material generally used as an organic light emitting material, such as a 9,10-diarylanthracene derivative, pyrene, coronene, perylene, rubrene, 1,1,4, 4-tetraphenylbutadiene, tris (8-quinolinolato) aluminum complex, tris (4-methyl-8-quinolinolato) aluminum complex, bis (8-quinolinolato) zinc complex, tris (4-methyl-5-trifluoromethyl-8) -Quinolinolato) aluminum complex, tris (4-methyl-5-cyano-8-quinolinolato) 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, tris (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 1,2,3,4 -Tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, poly-2,5-diheptyloxy-para-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor, porphyrin phosphor , Phosphorescent materials such as quinacridone phosphors, N, N′-dialkyl-substituted quinacridone phosphors, naphthalimide phosphors, N, N′-diaryl-substituted pyrrolopyrrole phosphors, or Ir complexes Known low-molecular light-emitting materials such as illuminants are listed, and these materials are It can be used as the organic light-emitting ink is dissolved or dispersed in a medium. In general, a low molecular weight light emitting material has a molecular weight of 1300 or less, but may have a molecular weight of 1300 or more as long as the light emitting molecule does not have a repeating structure.

Solvents that dissolve or disperse the above low-molecular light emitting materials include toluene, xylene, acetone, anisole, methylanisole, dimethylanisole, ethyl benzoate, methyl benzoate, mesitylene, tetralin, amylbenzene, methyl ethyl ketone, methyl isobutyl ketone, Cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, butyl acetate, water or the like can be used alone or in a mixed solvent, but not limited to the above as long as it can dissolve a low molecular weight light emitting material. Absent.

As the hole blocking material and the electron transporting material used for the hole blocking layer and the electron transporting layer, any material generally used as an electron transporting material may be used, such as triazole, oxazole, oxadiazole, silole, Examples include boron-based low molecular weight materials, and film formation by vacuum deposition is possible.

<Second electrode>
Next, the second electrode 104 is formed. When the second electrode is used as a cathode, a substance having a high electron injection efficiency into the organic light emitting medium layer 103 and a low work function is used. Specifically, a single metal such as Mg, Al, or Yb is used, or a compound such as Li, oxidized Li, or LiF is sandwiched by about 1 nm at the interface contacting the light emitting medium, and Al or Cu having high stability and conductivity is laminated. May be used. Alternatively, in order to achieve both electron injection efficiency and stability, one or more metals such as Li, Mg, Ca, Sr, La, Ce, Er, Eu, Sc, Y, and Yb having a low work function and stable Ag, Al An alloy system with a metal element such as Cu or Cu may be used. Specifically, alloys such as MgAg, AlLi, and CuLi can be used. In the case of a so-called top emission structure in which light is extracted from the second electrode side, it is preferable to select a light-transmitting material. In this case, after thinly providing Li and Ca having a low work function, a metal composite oxide such as ITO (indium tin composite oxide), indium zinc composite oxide, or zinc aluminum composite oxide may be laminated. The organic light emitting medium layer 103 may be laminated with a metal oxide such as ITO by doping a small amount of a metal such as Li or Ca having a low work function.

As a method for forming the second electrode 104, 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 depending on the material. Although there is no restriction | limiting in particular in the thickness of a 2nd electrode, About 10 nm-1000 nm are desirable. Moreover, when utilizing a 2nd electrode as a translucent electrode layer, about 0.1-10 nm is desirable for the film thickness in the case of using metal materials, such as Ca and Li.

<Passivation layer>
A passivation layer may be formed on the second electrode. Examples of the material for the passivation layer include metal oxides such as silicon oxide and aluminum oxide, metal fluorides such as aluminum fluoride and magnesium fluoride, metal nitrides such as silicon nitride, aluminum nitride and carbon nitride, and silicon oxynitride. A laminated film of a metal carbide such as metal oxynitride or silicon carbide, and a polymer resin film such as an acrylic resin, an epoxy resin, a silicone resin, or a polyester resin may be used as necessary. In particular, it is preferable to use silicon oxide (SiO _x ), silicon nitride (SiN _x ), and silicon oxynitride (SiO _x N _y ) from the viewpoints of gas barrier properties and transparency. Alternatively, a laminated film or a gradient film may be used.

As a method for forming the passivation layer, a resistance heating vapor deposition method, an electron beam vapor deposition method, a reactive vapor deposition method, an ion plating method, a sputtering method, or a CVD method can be used depending on the material. It is preferable to use a CVD method in terms of translucency. As the CVD method, a thermal CVD method, a plasma CVD method, a catalytic CVD method, a VUV-CVD method, or the like can be used. In addition, as a reaction gas in the CVD method, a gas such as N ₂ , O ₂ , NH ₃ , H ₂ , N ₂ O is added to an organic silicon compound such as monosilane, hexamethyldisilazane (HMDS), or tetraethoxysilane. It may be added as necessary. For example, the density of the film may be changed by changing the flow rate of silane, and hydrogen or carbon may be contained in the film by the reactive gas used. The film thickness of the sealing layer varies depending on the electrode step of the organic EL element, the height of the partition walls of the substrate, the required barrier characteristics, and the like, but generally about 10 nm to 10,000 nm is generally used.

<Sealing body>
As an organic EL device, it is possible to emit light by sandwiching a light emitting material between electrodes and passing an electric current. However, since the organic light emitting material is easily deteriorated by moisture and oxygen in the atmosphere, it is usually cut off from the outside. A sealing body is provided. For example, the sealing body can be formed by providing a resin layer made of a resin adhesive on a sealing material.

The sealing material needs to be a base material having low moisture and oxygen permeability. Examples of the material include ceramics such as alumina, silicon nitride, and boron nitride, glass such as alkali-free glass and alkali glass, metal foil such as quartz, aluminum, and stainless steel, and moisture-resistant film. Examples of moisture-resistant films include films formed by CVD of SiOx on both sides of plastic substrates, films with low permeability and water-absorbing films, or polymer films coated with a water-absorbing agent. The water vapor transmission rate is preferably 10 ⁻⁶ g / m ² / day or less.

Examples of the material for the resin layer include a photo-curing adhesive resin, a thermosetting adhesive resin, a two-component curable adhesive resin, and an ethylene ethyl acrylate (EEA) made of epoxy resin, acrylic resin, silicone resin, etc. Examples thereof include acrylic resins such as polymers, vinyl resins such as ethylene vinyl acetate (EVA), thermoplastic resins such as polyamide and synthetic rubber, and thermoplastic adhesive resins such as acid-modified products of polyethylene and polypropylene. Examples of methods for forming a resin layer on a sealing material include solvent solution method, extrusion lamination method, melting / hot melt method, calendar method, nozzle coating method, screen printing method, vacuum laminating method, hot roll laminating method. And so on. A material having a hygroscopic property or an oxygen absorbing property may be contained as necessary. Although the thickness of the resin layer formed on a sealing material is arbitrarily determined by the magnitude | size and shape of the organic EL element to seal, about 5-500 micrometers is desirable. In addition, although it formed as a resin layer on the sealing material here, it can also form directly in the organic EL element side.

Finally, the organic EL element and the sealing body are bonded together in a sealing chamber. When the sealing body has a two-layer structure of a sealing material and a resin layer, and a thermoplastic resin is used for the resin layer, it is preferable to perform only pressure bonding with a heated roll. When a thermosetting adhesive resin or a photocurable adhesive resin is used, it is preferable to carry out light or heat curing in a state where it is roll-bonded or flat-bonded. At this time, in order to prevent the organic EL element from being deteriorated by oxygen or moisture in the atmosphere, it is desirable to perform in an inert gas atmosphere, for example, an argon or nitrogen atmosphere.

Next, a method for forming an organic light emitting layer in the wet process according to the present invention will be described. However, the present invention is not limited to these.

In general, low-molecular light emitting materials are likely to be crystallized or aggregated. When an organic light emitting layer made of a low molecular light emitting material is formed by a wet process, the low molecular light emission that was dissolved and dispersed as the solvent of the organic light emitting ink in which the low molecular light emitting material is dissolved or dispersed is removed. This is because the material cannot be completely dissolved in the solvent and precipitates as crystals or agglomerates using impurities in the ink as nuclei. The organic light emitting layer in which crystallization or aggregation has occurred has a non-uniform film thickness, or the light emitting material is localized, causing unevenness in light emission. Furthermore, since the thickness of the organic light emitting layer is not uniform, the first electrode and the second electrode are likely to be short-circuited at a portion where the thickness of the organic light emitting layer is thin, which may cause a pixel defect.

However, in the present invention, when the organic light emitting ink is transferred onto the substrate by coating, ink jet or printing, the solubility of the solvent is increased by heating the substrate, and the low molecular light emitting material that cannot be dissolved due to the decrease in the solvent is crystallized. In the case where an organic light emitting layer made of a low molecular light emitting material is formed by a wet process, it is possible to form an organic light emitting layer with a uniform film thickness and without uneven light emission. Moreover, when forming an organic light emitting layer using a low molecular light emitting material, a light emitting material or a solvent that cannot be used conventionally because of crystallization or aggregation can be used.

Examples of wet processes include coating methods, inkjet methods, and printing methods. Examples of coating methods include spin coaters, bar coaters, roll coaters, die coaters, and gravure coaters. Printing methods include letterpress printing, letterpress offset printing, and intaglio printing. Printing, intaglio offset printing, etc. When the organic EL device according to the present invention is used as a display device of a display, it is necessary to form an organic light emitting layer by patterning. Therefore, an ink jet method or a printing method capable of forming a pattern is used. If this is not necessary, an organic light emitting layer may be formed on one surface of the first electrode by a coating method.

The means for heating the substrate is not particularly limited as long as the organic light-emitting ink transferred onto the substrate can be heated, but it is preferable to provide a heating element such as a heating wire in a surface plate for fixing the substrate. . The organic light-emitting ink is transferred onto a substrate fixed on a surface plate provided with heating means such as a heating wire by various coating methods, ink jet methods, or various printing methods. It may be heated later. Moreover, it is desirable to heat until the solvent in the transferred organic luminescent ink is completely removed.

The heating temperature of the substrate is desirably less than the glass transition point of the low molecular light emitting material to be used. When heated to a temperature higher than the glass transition point of the low molecular light emitting material, the low molecular light emitting material in a fluidized state may be crystallized as it is cooled. Therefore, it is desirable to change the heating temperature depending on the low molecular light emitting material to be used. However, if the temperature is in the range of 80 ° C. or higher and 120 ° C. or lower, the low molecular light emitting material is not crystallized and the organic light emitting layer is formed with good film forming properties. Can do.

The above wet process can be used not only for forming the organic light emitting layer but also for forming other layers of the organic light emitting medium layer such as a hole transport layer by a wet process. However, it is preferable that the heating temperature required for the upper layer is higher than the heating temperature required for the lower layer.

Next, specific examples of the present invention will be described with reference to Examples and Comparative Examples, but the present invention is not limited thereto.

Example 1
In Example 1, a glass substrate having a thickness of 0.7 mm and a diagonal size of 1.8 inches is used as a substrate, ITO is formed on the substrate by sputtering, and photolithography and etching with an acid solution are performed. The ITO film was patterned and provided as the first electrode.

Next, the partition was formed as follows. An acrylic photoresist material was spin coated on the entire surface of the glass substrate on which the first electrode was formed. The spin coating conditions were rotated at 150 rpm for 5 seconds, then at 500 rpm for 20 seconds, and the partition wall height was 1.5 μm by one coating. A partition wall was formed between the first electrodes by a photolithography method for the photoresist material applied to the entire surface.

Next, a PEDOT aqueous solution having a concentration of 1% was used as the hole injection layer ink, and a polymer film hole injection layer was formed between the partition walls by letterpress printing. At this time, an anilox roll of 180 lines / inch was used, and the thickness of the hole injection layer after drying was 50 nm.

Next, a low molecular film hole transport layer is formed on the first electrode sandwiched between the partition walls by letterpress printing using an ink in which the trifamine amine derivative, which is a hole transport material, is dissolved in cyclohexanol so as to be 1%. Formed. At this time, an anilox roll of 150 lines / inch and a water developing type photosensitive resin plate were used. The film thickness after printing was 30 nm.

Next, 1 wt% of a low molecular light emitting material doped with CBP (a host material manufactured by Sigma Aldrich) or Ir (ppy) ₃ (a doped material manufactured by Sigma Aldrich) is used, and 85% xylene and 15% anisole are used as a solvent. Adjust the organic light-emitting ink using a mixed solvent, place the substrate on a platen with heating wire, heat the substrate to a temperature of 100 ° C, and print the above organic light-emitting ink on the substrate by letterpress printing. Then, an organic light emitting layer having a thickness of 80 nm was patterned. Thereafter, the substrate was heated until the solvent was evaporated to dry the organic light emitting layer.

Next, LiF was formed into a film with a thickness of 0.5 nm by vacuum deposition.

Finally, Al was formed into a film as a second electrode having a thickness of 150 nm by vacuum deposition. And it sealed and sealed using the glass cap and the adhesive agent, and produced the organic electroluminescence display.

The obtained organic EL display device was able to light only selected pixels without short-circuiting between electrodes, and a good display device free from light emission unevenness was obtained. The luminance was 160 cd / m ² at 6V. When continuous lighting was performed at an initial luminance of 400 cd / m ² , the luminance half time was 1600 hours. As a result of observing the pixels with a microscope, no crystals or non-light emitting portions were confirmed.

(Comparative Example 1)
In Comparative Example 1, an organic EL display device was produced in the same manner as in Example 1 except that the organic light emitting layer was formed by a relief printing method without heating the substrate.

The obtained organic EL display device was 70 cd / m ² at 6 V, and the luminance was lower than that in Example 1. Further, white turbidity and unevenness occurred in the emission color, and as a result of observing the pixels with a microscope, many crystallized portions were observed in the organic light emitting layer, and non-light emitting portions were also observed. Furthermore, when continuous lighting was performed at an initial luminance of 400 cd / m ² , a short circuit occurred, and continuous lighting was difficult.

101: substrate 102: first electrode 103: organic light emitting medium layer 104: second electrode 105: partition

Claims (4)

A first electrode formed on the substrate, an organic light emitting medium layer including an organic light emitting layer made of at least a low molecular light emitting material formed on the first electrode, and formed to face the first electrode A method for producing an organic electroluminescence device comprising a second electrode,
The organic light emitting layer is formed by a wet process,
The method of manufacturing an organic electroluminescence element, wherein the wet process is performed while heating the substrate. The method for manufacturing an organic electroluminescent element according to claim 1, wherein the temperature for heating the substrate is 80C to 120C. The method for producing an organic electroluminescence element according to claim 2, wherein the wet process is any one of a coating method, an inkjet method, and a printing method. An organic electroluminescence device manufactured by the method for manufacturing an organic electroluminescence device according to claim 1.

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