JP2013077518A - Coating liquid for forming organic electroluminescent element and method for manufacturing organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating liquid for forming an organic electroluminescent element, which suppresses deterioration in luminous efficiency due to turning of an organic light-emitting medium layer into a coating liquid and improves a service life, in manufacturing an organic electroluminescent element by a wet process.SOLUTION: An element substrate is coated by a wet process using the coating liquid containing a fluorine-based solvent as a coating liquid of an organic light-emitting medium layer, and the solvent is removed to form the organic light-emitting medium layer, thereby manufacturing an organic electroluminescent element.

Description

  The present invention relates to a coating liquid for forming a luminescent medium layer of an organic thin film electroluminescent element (hereinafter referred to as “organic EL element”) using an electroluminescent phenomenon of an organic thin film, and a method for producing the organic EL element.

  The organic EL element is a self-luminous element having a structure in which an anode layer, an organic light emitting medium layer, and a cathode layer are sequentially laminated on a transparent substrate.

  The method of forming the organic light emitting medium layer of the organic EL element differs depending on the organic light emitting medium material, and is roughly classified into two methods, vapor deposition and wet methods. When a low molecular material is used as the organic light emitting medium layer, a vacuum evaporation method such as a resistance heating method is used. As the organic light emitting medium layer, copper phthalocyanine is used for the hole injection layer, and N, N′-di (1-naphthyl) -N, N′-diphenyl-1,1′-biphenyl-4,4 ′ is used for the hole transport layer. A typical example is a laminate of tris (8-quinolinol) aluminum with a thickness of about 10 to 100 nm on the diamine and the light emitting layer. In order to manufacture organic EL elements using these low molecular materials, a vacuum deposition apparatus in which a plurality of deposition pots are connected is required, and there are problems such as low productivity and high manufacturing cost.

  In contrast, when a dendrimer material or a polymer material is used as the organic light emitting medium layer, a wet method is used because the material can be made into a solution. In this case, the organic light emitting medium layer typically has a two-layer structure in which a hole transport layer and a light emitting layer are laminated. Compared with the organic EL element using the low molecular weight material described above, there is an advantage that film formation under atmospheric pressure is possible, productivity is high, and manufacturing cost is low.

  In recent years, low molecular weight materials that can be made into solutions have been developed, and material development that can replace high molecular weight materials has been intensively studied. Some low-molecular light-emitting materials used for the light-emitting layer have light emission efficiency and lifetime higher than that of the high-molecular light-emitting material, and therefore, there is a demand for replacement of the high-molecular light-emitting material with a low-molecular light-emitting material.

  In addition, there is a concern about deterioration of the light emission efficiency and life of the organic light emitting medium material due to coating liquefaction, and a technique for coating and liquefying the organic light emitting medium material with little deterioration of light emission efficiency and life is required.

  In Patent Document 1, a technique is adopted in which a fluorine-based surfactant is added to a polymer light-emitting material to reduce luminance unevenness on the surface of the light-emitting layer and prevent life deterioration. In this case, a resin having a fluorine-substituted alkyl group is used as the surfactant, and there is a concern that impurities remain in the light emitting layer.

  Here, compared with a polymer light-emitting material that mainly handles intramolecular carrier movement, in a low-molecular light-emitting material that mainly handles intermolecular carrier movement, carrier movement is hindered by impurities in the light emitting layer. For example, the light emission efficiency and lifetime are greatly degraded.

  In Patent Document 2, a method of manufacturing an organic EL element using a coating liquid in which a fluorine-based surfactant or the like is added to an aqueous light-emitting medium material is employed. Also in this case, the moisture contained in the coating liquid of the organic EL element causes a great deterioration in luminous efficiency and life.

Japanese Patent No. 3848188 Japanese Patent No. 4341304

  The wet method is considered promising for the problems of improving productivity and reducing manufacturing costs. However, in the organic EL element manufacturing method by the above-described wet method, there is a problem that the light emission efficiency and the lifetime are deteriorated due to the coating liquid of the organic light emitting medium material.

  An object of the present invention is to provide a coating liquid of an organic light emitting medium material that can suppress a decrease in light emission efficiency and improve a lifetime.

  The present invention relates to an organic light emitting device that constitutes a light emitting medium layer among a plurality of layers included in an organic EL device in which at least a patterned electrode layer, a light emitting medium layer, and a counter electrode layer are laminated on a light transmitting substrate. The present invention relates to a coating solution for water-insoluble organic EL for forming a layer. The coating liquid for organic EL contains one or more kinds of low-molecular light-emitting materials having no repetitive structure, a solvent for dissolving the low-molecular light-emitting materials, and at least one fluorine-based solvent.

  Moreover, this invention comprises a luminescent medium layer among the several layers contained in the organic electroluminescent element formed by laminating | stacking at least the patterned electrode layer, the luminescent medium layer, and the counter electrode layer on the translucent board | substrate. The present invention relates to a coating solution for water-insoluble organic EL for forming a hole transport layer. The coating liquid for organic EL contains a hole transport material, a solvent for dissolving or dispersing the hole transport material, and at least one fluorine-based solvent.

  According to the coating liquid for organic EL according to the present invention, the wettability with the lower layer is improved by the addition of the fluorine-based solvent. As a result, interlayer adhesion is improved, and physical and electrical durability can be improved. .

Explanatory drawing of the layer structure of the organic EL element which concerns on embodiment of this invention Sectional drawing which shows the specific structure of the organic EL element which concerns on embodiment of this invention. Explanatory drawing showing a relief printing apparatus used in the wet method Explanatory drawing which shows the inkjet apparatus used with a wet method Explanatory drawing showing a nozzle printing device used in the wet method

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. The drawings referred to in the following description are for explaining the configuration of the present embodiment, and the size, thickness, dimensions, and the like of each part shown in the drawings are different from the actual ones. Further, the present invention is not limited to these embodiments.

  FIG. 1 is an explanatory diagram showing the layer configuration of the organic EL element according to this embodiment. More specifically, FIG. 1A is a cross-sectional view taken along line A-A ′ in FIG. 1B, and FIG. 1B is a plan view.

  The organic EL element 1 shown in FIG. 1 has a so-called passive matrix structure, and a plurality of light-transmitting substrates 2 for supporting the organic EL element 1 and a plurality of the EL elements 1 so as to be parallel to each other on the surface of the light-transmitting substrate 2. The formed pixel electrode 3, an organic light emitting medium layer 6 stacked on the pixel electrode 3, and a plurality of counter electrodes 7 stacked on the organic light emitting medium layer 6 and orthogonal to the pixel electrode 3 are provided. Hereinafter, a case where the pixel electrode 3 is an anode and the counter electrode 7 is a cathode will be described. The organic EL element 1 may have a so-called active matrix structure in which a thin film transistor (TFT) is formed on the surface of the translucent substrate 2. Further, the pixel electrode 3 may be a cathode and the counter electrode 7 may be an anode.

  FIG. 2 is a cross-sectional view showing a specific configuration of the organic EL element according to the embodiment of the present invention.

  The translucent substrate 2 is a substrate that supports the pixel electrode 3, the organic light emitting medium layer 6, and the counter electrode 7, and is made of a film or sheet such as metal, glass, or plastic. As the plastic film, polyethylene terephthalate, polypropylene, cycloolefin polymer, polyamide, polyethersulfone, polymethyl methacrylate, or polycarbonate can be used. In addition, another gas barrier film such as a ceramic vapor-deposited film, polyvinylidene chloride, polyvinyl chloride, ethylene-vinyl acetate copolymer saponified product is laminated on the other surface of the translucent substrate 2 where the pixel electrode 3 is not formed. May be.

  The pixel electrode 3 is formed by forming a layer made of a material for forming the pixel electrode 3 on the translucent substrate 2 and then performing patterning as necessary. The barrier ribs 22 may be patterned on the layer made of the material of the pixel electrode 3 as necessary to form the pixel electrode 3 corresponding to each pixel. Examples of the material of the pixel electrode 3 include metal composite oxides such as ITO (indium tin composite oxide), indium zinc composite oxide, and zinc aluminum composite oxide, metal materials such as gold and platinum, these metal oxides, Either a single layer or a laminate of fine particle dispersion films in which fine particles of a metal material are dispersed in an epoxy resin or an acrylic resin can be used. When the pixel electrode 3 is used as an anode, it is preferable to select a material having a high work function such as ITO.

  In the case of a so-called bottom emission structure in which light is extracted from below, it is necessary to select a light-transmitting material. 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 pixel electrode 3. Although the optimum value of the film thickness of the pixel electrode 3 varies depending on the element configuration of the organic EL display, it is not less than 100 mm and not more than 10,000 mm, more preferably not less than 100 mm and not more than 3000 mm, regardless of single layer or stacked layers.

  As a method for forming the pixel electrode 3, depending on the material, 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, a sputtering method, a gravure printing method, or a screen printing method is used. A wet film forming method such as a method can be used.

  The barrier ribs 22 are formed between the pixel electrodes 3 in order to prevent the organic light emitting medium layers 6 formed on the pixel electrodes 3 from mixing with each other. The pattern of the barrier ribs 22 is desirably linear or lattice. As a conventional method for forming the partition walls 22, an inorganic film is uniformly formed on a substrate and masked with a resist, and then dry etching is performed, 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. Examples of the photosensitive resin that can be used as the material of the partition wall 22 include polyimide, acrylic resin, novolac resin, cardo resin, and fluororesin, as long as the resin can be formed by photolithography. Can be used.

  A preferable height of the partition wall 22 is 0.01 μm or more and 10 μm or less, and more preferably 0.5 μm or more and 5 μm or less. If the height of the partition wall 22 exceeds 10 μm, the formation and sealing of the counter electrode is hindered, and if it is less than 0.01 μm, the organic light emitting medium layer 6 is mixed in color or short-circuited with adjacent pixels. .

  Next, a layer made of the material of the organic light emitting medium layer 6 is formed. The organic light emitting medium layer 6 in the present embodiment can be formed of a single layer film or a multilayer film containing an organic light emitting material, and includes at least a hole transport layer 4 formed on the upper surface of the pixel electrode 3, and a hole. The organic light emitting layer 5 formed on the upper surface of the transport layer 4 is laminated. Examples of the configuration in the case of forming with a multilayer film include a hole transport layer 4, an electron transporting light emitting layer or a hole transporting light emitting layer, a three layer structure comprising an electron transport layer, a hole transport layer 4, and an organic light emitting layer 5. , A three-layer structure composed of an electron transport layer, and further, if necessary, a hole or electron injection function and a hole or electron transport function are separated, or a layer that blocks the transport of holes or electrons is inserted. Therefore, it is more preferable to form a multilayer. In addition, the organic light emitting layer 5 in this embodiment refers to the layer containing an organic light emitting material.

  The hole transport layer 4 advances holes injected from the pixel electrode 3 serving as the anode toward the counter electrode 7 serving as the cathode, and prevents electrons from traveling toward the pixel electrode 3 while passing through the holes. It has a function to do.

Examples of the hole transport material used for the hole transport layer 4 include 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, N′-diphenyl-1,1′-biphenyl-4,4′-diamine and other aromatic amine-based low-molecular hole injection / transport materials, polyaniline, polythiophene, polyvinylcarbazole, poly ( polymer hole transporting materials such as 3,4-ethylenedioxythiophene) and a mixture of polystyrene sulfonic acid, polythiophene oligomer materials, Cu ₂ O, C _{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, It can be selected from inorganic materials such as V ₂ O ₅ , Nb ₂ O ₅ , Ta ₂ O ₅ , MoO ₃ , WO ₃ , MnO ₂ , and other existing hole transport materials.

  Solvents for dissolving or dispersing the hole transport material include toluene, xylene, anisole, dimethoxybenzene, tetralin, cyclohexanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, cyclohexanone, methanol, ethanol, isopropyl alcohol, ethyl acetate, acetic acid. Among butyl, methyl benzoate, ethyl benzoate and the like, any one or a mixture thereof can be mentioned.

  A fluorine-based solvent described later is added to the solution or dispersion of the hole transport material described above. In addition, a surfactant, an antioxidant, a viscosity modifier, an ultraviolet absorber, or the like may be added to the coating solution for the hole transport material as necessary. Examples of the viscosity modifier include polystyrene and polyvinylcarbazole. Etc. can be used.

  As a method for forming the hole transport layer 4, depending on the material used for the hole transport layer 4, spin coating, bar coating, wire coating, slit coating, spray coating, curtain coating, flow coating, letterpress printing, letterpress inversion offset Wet methods such as printing, ink jet method, and nozzle printing method, and vapor deposition methods such as resistance heating vapor deposition method, electron beam vapor deposition method, reactive vapor deposition method, ion plating method, and sputtering method can be used.

  An interlayer layer may be formed on the hole transport layer 4. Examples of materials used for the interlayer layer include polymers containing aromatic amines such as polyvinyl carbazole or derivatives thereof, polyarylene derivatives having aromatic amines in the side chain or main chain, arylamine derivatives, and triphenyldiamine derivatives. . These materials can be dissolved or dispersed in a solvent and formed by a wet method such as a spin coating method or other vapor deposition methods.

  The organic light-emitting layer 5 is a functional material of the organic light-emitting layer 5 that emits red, green, or blue light when a voltage is applied, and includes a low-molecular light-emitting material that does not have a repeating structure and a polymer material that has a repeating structure. It is formed by applying a coating solution of an organic light emitting material dissolved or dispersed in a solvent on the hole transport layer 4. The low molecular light emitting material preferably has a mass average molecular weight of 100 to 10,000. The organic light emitting layer 5 is formed by depositing a coating solution of an organic light emitting material in which a low molecular light emitting material is dissolved or dispersed on the hole transport layer 4 using a wet method and then drying it. Xylene or anisole is preferably used as a solvent for the coating solution, but the above-mentioned solvent used for forming the hole transport layer 4 can also be used. In addition, the film thickness of the organic light emitting layer 5 should just be the range of 0.01 micrometer-0.1 micrometer, and it is more preferable that it is 0.03 micrometer-0.08 micrometer. When the thickness is out of the range, the luminous efficiency tends to decrease.

  As the low molecular light emitting material having no repeating structure used for the organic light emitting layer 5, the organic light emitting material used for the organic light emitting layer includes 9,10-diarylanthracene derivatives, 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-trifluoro) Methyl-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-) -Cyano-8-quinolinolato) [4- (4-cyanophenyl) phenolate] aluminum complex, tris (8-quinolinolato) scandium complex, bis [8- (para-tosyl) aminoquinoline] zinc complex and cadmium complex, 2,3,4-tetraphenylcyclopentadiene, pentaphenylcyclopentadiene, poly-2,5-diheptyloxy-para-phenylene vinylene, coumarin phosphor, perylene phosphor, pyran phosphor, anthrone phosphor Phosphorescent materials such as Ir complexes, porphyrin phosphors, quinacridone phosphors, N, N′-dialkyl-substituted quinacridone phosphors, naphthalimide phosphors, N, N′-diaryl-substituted pyrrolopyrrole phosphors, etc. The body can be used.

  Here, as a low molecular light emitting material used for the organic light emitting layer 5 that emits red light, DCM (4-dicyanomethylene-6- (), a tris (8-quinolinol) aluminum (Alq3), and a pyran compound doping material. p-dimethylaminostyryl) -2-methyl-4H-pyran) and DCJTB (4-dicyanomethylene-6- (p-dimethylaminostyryl) -2- (t-butyl) -4H-pyran), respectively. What added so that a density | concentration might be 2% is mentioned. And this low molecular light-emitting material is melt | dissolved in a solvent, and the coating liquid is formed.

  In addition, the density | concentration of the low molecular light emitting material in a coating liquid should just be the range of 0.1 weight%-10 weight%, and it is more preferable that it is 1.0 weight%-5.0 weight%. Thus, by setting the concentration to 1.0 wt% to 5.0 wt% or less, the film thickness at the time of application does not become too large, and the pattern accuracy at the time of application can be maintained. Note that the weight of the low-molecular light-emitting material having the above ratio represents the combined weight of the host material and the dope material.

  In addition, as a low molecular light emitting material used for the organic light emitting layer 5 emitting green light, Alq3, 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl) as a host material is used. -1H-benzimidazole) (TPBi) and tris (2- (p-tolyl) pyridine) iridium III (Ir (mppy) 3) as a doping material are added so that the doping concentration is 4%. Can be mentioned. And this low molecular light-emitting material is melt | dissolved in a solvent, and the coating liquid is formed. In addition, the density | concentration of the low molecular light emitting material in a coating liquid should just be the range of 0.1 weight%-10 weight%, and it is more preferable that it is 1.0 weight%-5.0 weight%. Note that the weight of the low-molecular light-emitting material having the above ratio represents the combined weight of the host material and the dope material.

Moreover, as a low molecular light emitting material used for the organic light emitting layer 5 that emits blue light, Alq3, DPVBi (4,4′-bis (2,2′-diphenylvinyl) -biphenyl) as a doping material, and Zn ( BOX) ₂ (2- (O-hydroxyphenyl) benzothiazole zinc complex) is added so that the doping concentration is 2%. And this low molecular light-emitting material is melt | dissolved in a solvent, and the coating liquid is formed. In addition, the density | concentration of the low molecular light emitting material in a coating liquid should just be the range of 0.1 weight%-10 weight%, and it is more preferable that it is 1.0 weight%-5.0 weight%.

  Xylene or anisole can be used as a solvent used in a coating solution containing an organic light emitting material. Xylene or anisole has good solubility in many aromatic compounds and organic metal complexes that are used as low-molecular light emitting materials, such as spin coating, bar coating, wire coating, slit coating, spray coating, Good applicability in wet methods such as curtain coating, flow coating, letterpress printing, letterpress reversal offset printing, ink jet method and nozzle printing method. Furthermore, by using xylene as the coating liquid of the low molecular weight light emitting material for the organic light emitting layer, the drying process can be simplified, so that the influence of the residual solvent can be suppressed and the decrease in light emission efficiency can be suppressed.

  In addition, toluene, mesitylene, cumene, anisole, methylanisole, paracymene, tetralin, cyclohexylbenzene, methylnaphthalene, cyclohexanone, cyclohexylbenzene, dimethoxybenzene, methyl benzoate, ethyl benzoate, ethanol, acetone, methyl ethyl ketone, methyl isobutyl ketone, A solvent such as methanol, isopropyl alcohol, cyclohexanol, ethyl acetate, butyl acetate, methyl benzoate, or ethyl benzoate can be used as a mixed solvent. In order to improve coatability, it is more preferable to mix an appropriate amount of additives such as surfactants, antioxidants, viscosity modifiers and ultraviolet absorbers as necessary.

  Examples of the fluorine-based solvent to be added include methyl nonafluoroisobutyl ether, methyl nonafluorobutyl ether, ethyl nonafluoroisobutyl ether, ethyl nonafluorobutyl ether, 1,1,1,2,2,3,4,5,5, 5-decafluoro-3methoxy-4- (trifluoromethyl) -pentane, 1,1,1,2,3,3-hexafluoro-4- (1,1,2,3,3,3-hexafluoro Perfluoroethers containing a methoxy group or an ethoxy group such as propoxy) -pentane can be used, and preferably 1,1,1,2,2,3,4,5,5,5-decafluoro-3methoxy -4- (trifluoromethyl) -pentane (boiling point: 98 ° C., surface tension: 15 mN / m), 1,1,1,2,3,3-hexafluoro-4 (1,1,2,3,3,3-hexafluoro-propoxy) - pentane (boiling point: 131 ° C., surface tension: 18 mN / m) is good. Other than the perfluoroether type fluorine solvent, any fluorine type solvent in which the surface tension of the coating liquid to which the fluorine type solvent is added becomes 10 to 30 mN / m may be used, and aromatic fluorine such as fluorotoluene, fluoroxylene, benzotrifluoride, etc. It may be a solvent.

  The boiling point of the fluorine-based solvent is preferably lower than the glass transition temperature Tg of the light-emitting medium material used in the organic EL element 1, and the glass transition temperature of the light-emitting medium material is approximately 100 ° C. or higher. Is preferably 100 ° C. or lower.

  The addition amount of the fluorine-based solvent may be 0.1% or more and less than 20% with respect to the solvent weight of the coating solution, and more preferably 1% or more and 10% or less. If the fluorinated solvent is less than 0.1%, the surface tension is greater than 30 mN / m and the wettability with the lower layer cannot be improved, and if it is 20% or more, the luminescent medium material may be precipitated.

  As an electron transport material used for the electron transport layer, 2- (4-bifinylyl) -5- (4-tert-butylphenyl) -1,3,4-oxadiazole, 2,5-bis (1-naphthyl) ) -1,3,4-oxadiazole, oxadiazole derivatives, bis (10-hydroxybenzo [h] quinolinolato) beryllium complexes, triazole compounds, and the like can be used. Alternatively, these electron transport materials may be used as an electron injection layer by doping a small amount of alkali metal or alkaline earth metal having a low work function such as sodium, barium, or lithium.

  As the method for forming the electron transport layer, depending on the material used, spin coating, bar coating, wire coating, slit coating, spray coating, curtain coating, flow coating, letterpress printing, letterpress reverse printing, ink jet method, nozzle printing method Wet methods such as resistance heating evaporation method, electron beam evaporation method, reactive evaporation method, ion plating method, sputtering method and the like can be used.

  The counter electrode 7 is formed on the organic light emitting layer 5. When the second electrode is used as a cathode, a substance having a high work efficiency of electron injection into the organic light emitting medium layer 6 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. Or 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 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 counter electrode 7, 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.

  For example, a passivation layer may be formed on the counter electrode 7 between the counter electrode 7 and the sealing material 23. 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, from the viewpoint of barrier properties and transparency, it is preferable to use silicon oxide (SiOx), silicon nitride (SiNx), or silicon oxynitride (SiOxNy). Alternatively, a gradient membrane 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 , or N ₂ O is added to an organic silicone 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 thickness of the passivation layer varies depending on the electrode level difference of the organic EL element 1, the height of the partition walls of the substrate, the required barrier characteristics, and the like, but generally about 0.01 μm to 10 μm is generally used.

The sealing material 23 is provided to shield the organic light emitting medium layer 6 from the outside. The reason why the sealing material 23 is provided is that the organic light emitting layer 5 is easily deteriorated by moisture and oxygen in the atmosphere. The sealing material 23 can be produced by, for example, laminating a resin layer on the counter electrode 7. The sealing material 23 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 1 × 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 the resin layer on the counter electrode 7 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. The thickness of the resin layer formed on the counter electrode 7 is arbitrarily determined depending on the size and shape of the organic EL element 1 to be sealed, but is preferably about 5 to 500 μm. In addition, although it formed as a resin layer on the counter electrode 7 here, it can also form directly in the organic EL element 1 side.

  Finally, the organic EL element 1 and the sealing material 23 are bonded together in a sealing chamber. When the sealing material 23 has a two-layer structure of a sealing layer and a resin layer, and a thermoplastic resin is used for the resin layer, it is preferable to perform only the 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.

  The outline of the manufacturing method of the organic EL element 1 having the above configuration will be described. First, the pixel electrode 3 is formed on the translucent substrate 2. This is because an ITO film is formed on the entire surface of the translucent substrate 2 using a sputtering method, and further, exposure and development are performed by a photolithography technique, and a main part remaining as the pixel electrode 3 is covered with a photoresist. Then, unnecessary portions are etched with an acid solution to remove the ITO film. In this way, a plurality of pixel electrodes 3 arranged at predetermined intervals are formed.

  Next, the partition wall 22 is formed on each pixel electrode 3. In this method, a photoresist is applied on the translucent substrate 2 or the pixel electrode 3, and exposure and development are performed by a photolithography technique to leave the photoresist on each pixel electrode 3. Thereafter, the photoresist is cured by baking.

  Then, using a relief printing apparatus 31 as shown in FIG. 3, a hole transport material coating solution is applied onto the pixel electrode 3 to form the hole transport layer 4. The relief printing apparatus 31 includes a coating liquid tank 32 that stores a coating liquid of a hole transport material, a supply nozzle 33 that supplies the coating liquid to the anilox roll 34, and a coating liquid that is supplied from the anilox roll to the pixel electrode 3. A roll 35 and a relief plate 36 are attached to the surface. The coating liquid adhering to the pixel electrode 3 is averaged within the region partitioned by the partition wall 22 because of its low viscosity. Thereafter, the coating liquid is dried and fixed on the pixel electrode 3.

  After the hole transport layer 4 is formed, the organic light emitting layer 5 is formed on the hole transport layer 4 by a relief printing method as described above. As described above, a material for forming the organic light emitting layer 5 is used by mixing a fluorine-based solvent with a coating solution of a low molecular light emitting material.

  Subsequently, the counter electrode 7 is formed by vapor deposition on the organic light emitting layer 5 by vapor deposition such as resistance heating vapor deposition. Finally, the pixel electrode 3, the organic light emitting medium layer 6, and the counter electrode 7 are filled with a resin layer in order to protect them from oxygen and moisture in the air, and covered and sealed with a sealing substrate 24, and then the organic EL element 1 Manufacturing.

  According to the organic EL element 1 and the manufacturing method of the organic EL element 1 configured as described above, it is possible to use a low molecular light emitting material by a relief printing method, and without reducing the light emission efficiency, the organic light emitting layer 5 can be stabilized.

  The hole transport layer 4 may be formed by applying a coating liquid of a hole transport material onto the pixel electrode 3 using an ink jet apparatus 41 as shown in FIG. The ink jet apparatus 41 includes a coating liquid tank 42 that stores a coating liquid of a hole transport material and a discharge head 43 that adheres the coating liquid to the surface of the pixel electrode 3. The coating liquid adhering to the pixel electrode 3 is averaged within the region partitioned by the partition wall 22 because of its low viscosity. Thereafter, the coating liquid is dried and fixed on the pixel electrode 3.

  After forming the hole transport layer 4, the organic light emitting layer 5 is formed on the hole transport layer 4 by an ink jet apparatus in the same manner as described above. As described above, as a material for forming the organic light emitting layer, a fluorine-based solvent is mixed with a coating solution of a low molecular light emitting material.

  A hole transport layer 4 may be formed by applying a coating liquid of a hole transport material onto the pixel electrode 3 using a nozzle printing apparatus 51 as shown in FIG. The nozzle printing apparatus 51 includes a coating liquid tank 52 that stores a coating liquid of a hole transport material, and a discharge head 53 that adheres the coating liquid to the surface of the pixel electrode 3. The coating liquid adhering to the pixel electrode 3 is averaged within the region partitioned by the partition wall 22 because of its low viscosity. Thereafter, the coating liquid is dried and fixed on the pixel electrode 3.

  After forming the hole transport layer 4, the organic light emitting layer 5 is formed on the hole transport layer 4 by a nozzle printing apparatus in the same manner as described above. As described above, a material for forming the organic light emitting layer 5 is used by mixing a fluorine-based solvent with a coating solution of a low molecular light emitting material.

  In addition, this invention is not limited to the said embodiment, A various change can be added in the range which does not deviate from the meaning of this invention. For example, a hole blocking layer, a hole injection layer, an electron injection layer, or an electron block layer may be formed. Here, as with the hole transport layer 4, the hole injection layer and the electron block layer pass holes from the pixel electrode 3 that is the pixel electrode toward the counter electrode 7 that is the counter electrode. Also, it has a function of preventing electrons from traveling in the direction of the pixel electrode 3. The hole blocking layer, the electron transporting layer, and the electron injecting layer allow electrons to pass from the counter electrode 7 that is the counter electrode toward the pixel electrode 3 that is the pixel electrode, while passing the electrons. It has the function to prevent progressing in the direction.

  Further, a thin film such as lithium fluoride may be provided between the counter electrode 7 and the organic light emitting medium layer 6. In order to pattern the counter electrode 7, a metal film, a ceramic film deposition mask, or the like can be used. Furthermore, although the barrier ribs 22 are formed on each pixel electrode 3, the barrier ribs 22 may not be provided.

  Hereinafter, the present invention will be described in detail with reference to Examples and Comparative Examples. However, the present invention is not limited by the following description.

[Element creation]
As shown in FIG. 1, a strip-like pixel electrode 3 having a width of 80 μm and a thickness of 0.15 μm is formed on a light-transmitting substrate 2 (white plate glass: length 100 mm × width 100 mm × thickness 0.7 mm) by a sputtering method to 80 μm. Formed at intervals. Here, the surface roughness Ra of the pixel electrode 3 was 20 nm in an arbitrary plane of 200 μm 2. Here, the hole transport layer 4 was prepared by using a polyarylene derivative as a hole transport material and dissolving it in xylene to a concentration of 3.0% by weight. Fluorine solvent 1,1,1,2,2,3,4,5,5,5-decafluoro-3methoxy-4- (trifluoromethyl) -pentane (hereinafter referred to as F1) was added to this solution. It added and it was set as the coating liquid. The coating solution was formed on the substrate by spin coating and dried at 200 ° C. for 10 minutes.

The organic light-emitting layer 5 is a low-molecular light-emitting material used for a pixel emitting green light, and the host material is 2,2 ′, 2 ″-(1,3,5-benzenetriyl) tris (1-phenyl- 1H-benzimidazole (TPBi) and tris (2- (p-tolyl) pyridine) iridium III (Ir (mppy) ₃ ) were used as the doping material. And F1 was used as a fluorine-type solvent added to the coating liquid of this low molecular light-emitting material. A low molecular light emitting material was dissolved in xylene to obtain a 1 wt% solution, and a fluorinated solvent F1 was added to prepare a coating solution. This coating solution was applied to the substrate on the hole transport layer 4 by a spin coating method and dried in an inert gas atmosphere at 100 ° C. for 30 minutes to obtain an organic light emitting layer 5 having a thickness of 70 nm. The coating liquid compositions of the hole transport layer 4 and the organic light emitting layer 5 are described in the following examples. Thereafter, LiF / Al = 0.5 nm / 150 nm was formed as the counter electrode 7 by vapor deposition. Then, the sealing substrate 24 was adhere | attached and the organic EL element 1 was obtained.

[Evaluation method]
The formation process of the organic EL element 1 produced according to this example and the evaluation of the formed organic EL element 1 were performed as follows.

(Luminescence efficiency)
Luminous efficiency (cd / A) when a voltage of 7 V was applied to the produced organic EL element 1 was measured.

(lifespan)
Using the produced organic EL element 1, the half-life of luminance was measured with a constant current at a luminance of 1000 cd / m ² .

(Chromaticity)
Using the produced organic EL element 1, chromaticity (x, y) at a luminance of 1000 cd / m ² was measured.

[Example 1]
Evaluation was performed using a solution obtained by adding 10% of a fluorinated solvent to a solution of a low-molecular light-emitting material (host / dopant) forming the organic light-emitting layer 5 as a coating solution.

[Example 2]
Evaluation was performed using a solution obtained by adding 10% of a fluorine-based solvent to a solution of a hole transport material forming the hole transport layer 4 as a coating solution.

[Example 3]
Evaluation was performed using a solution obtained by adding 10% of a fluorine-based solvent to a solution of a hole transport material and a low-molecular light-emitting material (host / dopant) that form the hole transport layer 4 and the organic light-emitting layer 5, respectively. .

[Comparative Example 1]
Evaluation was performed using a coating solution to which no fluorinated solvent was added.

[Comparative Example 2]
Evaluation was carried out in the same manner as in Example 1 except that 4-fluorophenetol (hereinafter referred to as F2) (boiling point: 180 ° C.) was used as the fluorinated solvent used in the organic light emitting layer 5.

[Comparative Example 3]
Evaluation was performed in the same manner as in Example 1 except that the baking temperature of the organic light emitting layer 5 was 180 ° C.

[Comparative Example 4]
Evaluation was performed in the same manner as in Example 1 except that 4-fluorophenetol (boiling point: 180 ° C.) was used as the fluorinated solvent used in the organic light emitting layer 5 and the baking temperature of the organic light emitting layer 5 was 180 ° C.

Table 1 shows the evaluation results of luminous efficiency, half-life and chromaticity of Examples 1 to 3 and Comparative Example 1.

Table 2 shows the evaluation results of film formability and light emission efficiency of Example 1 and Comparative Examples 2 to 4.

  As shown in Table 1, compared with the case where the fluorinated solvent of Comparative Example 1 was not used, the fluorinated solvent was added to the hole transport layer 4 or the organic light emitting layer 5 from Examples 1 to 3. As a result, it was possible to suppress the decrease in luminous efficiency and improve the lifetime. In particular, it has been found that the improvement rate of lifetime and the luminous efficiency are increased by using a coating liquid to which a fluorine-based solvent is added for forming both the hole transport layer 4 and the organic light emitting layer 5 of the low molecular light emitting material. It was also confirmed that there was no effect on chromaticity.

  Further, as shown in Table 2, there is no problem in film formability and a decrease in luminous efficiency is observed in the low temperature baking when the fluorine-based solvent (F1) having a boiling point lower than the glass transition temperature of the organic light emitting layer 5 is used. There wasn't. However, although low temperature baking when using a fluorine-based solvent (F2) having a boiling point higher than the glass transition temperature of the organic light-emitting layer 5, there was no problem in film formability, but a decrease in light emission efficiency was observed. This is considered to be due to the residual fluorine-based solvent and impurities. On the other hand, in high temperature baking (boiling point of F2), aggregation of the light emitting material occurred, resulting in a problem in film formability.

  According to this invention, a fluorine-based solvent is added to the organic EL coating liquid, and the organic EL element 1 is manufactured by a process using a wet method, thereby suppressing a decrease in luminous efficiency and improving the lifetime.

DESCRIPTION OF SYMBOLS 1 Organic EL element 2 Translucent board | substrate 3 Pixel electrode 4 Hole transport layer 5 Light emitting layer 6 Organic light emitting medium layer 7 Counter electrode 8 Light emitting pixel 21 EL element with a partition 22 Partition 23 Sealing material 24 Sealing substrate 31 Letterpress printing apparatus 32 Coating liquid tank 33 Supply nozzle 34 Anilox roll 35 Roll 36 Letterpress 41 Ink jet device 42 Coating liquid tank 43 Discharge head 51 Nozzle printing device 52 Coating liquid tank 53 Discharge head

Claims (8)

On the translucent substrate, an organic light emitting layer constituting the light emitting medium layer is formed among a plurality of layers included in the organic EL element formed by laminating at least a patterned electrode layer, a light emitting medium layer, and a counter electrode layer. A non-water-soluble organic EL coating solution,
One or more kinds of low-molecular light emitting materials having no repetitive structure;
A solvent for dissolving the low-molecular light-emitting material;
An organic EL coating solution containing at least one fluorine-based solvent. Of the plurality of layers included in the organic EL element in which at least a patterned electrode layer, a light emitting medium layer, and a counter electrode layer are stacked on a light-transmitting substrate, a hole transport layer constituting the light emitting medium layer is provided. A coating solution for water-insoluble organic EL for forming,
A hole transport material;
A solvent for dissolving or dispersing the hole transport material;
An organic EL coating solution containing at least one fluorine-based solvent.   The coating liquid for organic EL of Claim 2 used in order to form at least 1 layer among the several layers which comprise the said positive hole transport layer.   The coating liquid for organic EL of Claim 2 or 3 used in order to form the layer adjacent to the said electrode layer among the several layers which comprise the said positive hole transport layer.   The coating liquid for organic EL according to any one of claims 1 to 4, wherein the fluorinated solvent is perfluoroether.   The organic EL according to any one of claims 1 to 6, wherein the fluorine-based solvent is contained in a ratio of 0.1 wt% or more and less than 20 wt% with respect to the coating solution for organic EL. Coating liquid.   The coating liquid for organic EL according to any one of claims 1 to 6, wherein a boiling point of the fluorinated solvent is smaller than a glass transition temperature of the luminescent medium layer. A method for manufacturing an organic EL element,
An application step of applying at least one of the organic light-emitting medium layers on the element substrate by a wet method using the organic EL application liquid according to claim 1,
And a solvent removal step of forming the organic light emitting medium layer by removing the solvent contained in the coating solution.

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