JP2013101751A - Organic electroluminescent element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an organic electroluminescent element capable of extracting light more efficiently.SOLUTION: An organic electroluminescent element includes a transparent substrate 1, a transparent electrode 2 provided on the transparent substrate 1, and an organic light-emitting layer 3 provided on the transparent electrode 2. The transparent electrode 2 is formed by adding metal nanowires 5 and refractive index control particles 6 into a matrix resin 4. The refractive index n1 of the transparent substrate 1, the refractive index n2 of the transparent electrode 2, and the refractive index n3 of the organic light-emitting layer 3 are set to satisfy a relation of n1≤n2≤n3, n3-n1≤0.3. Total reflection of light can be minimized, respectively, on the boundary surface of the organic light-emitting layer 3 and the transparent electrode 2, and on the boundary surface of the transparent electrode 2 and the transparent substrate 1.

Description

  The present invention relates to an organic electroluminescence element used as a surface light emitter or the like.

  A typical example of the surface light emitter is an organic electroluminescence element (organic EL element). As shown in FIG. 3, this organic EL element is provided with a light transmissive transparent electrode 2 on a light transmissive transparent substrate 1, an organic light emitting layer 3 on the transparent electrode 2, and organic light emission. It is formed by providing an electrode 10 on the layer 3. The light emitted from the organic light emitting layer 3 by applying a voltage between the transparent electrode 2 and the electrode 10 is extracted through the transparent electrode 2 and the transparent substrate 1.

  Here, the transparent electrode 2 is formed by using a metal oxide such as ITO, IZO, AZO, GZO, FTO, or ATO as a transparent conductive material, and using a vapor deposition method such as a sputtering method or a vacuum evaporation method. (See, for example, Patent Document 1).

  However, these film forming methods require an expensive apparatus and a large amount of energy, and therefore a technique for reducing the manufacturing cost and the environmental load is required. Moreover, the refractive index of the transparent electrode 2 formed by forming these metal oxides is significantly higher than that of the transparent substrate 1 generally formed of glass. For this reason, due to the difference in refractive index between the transparent substrate 1 and the transparent electrode 2, the light emitted from the organic light emitting layer 3 is easily totally reflected at the interface between the transparent electrode 2 and the transparent substrate 1, and this total reflection loss is a light extraction efficiency. It became a factor to reduce the.

  On the other hand, an organic EL in which a transparent electrode is formed of a transparent film containing a wire-like conductor has been proposed (see Patent Document 2). In this case, since the refractive index of the transparent electrode can be controlled by selecting the material for forming the transparent film, by adjusting the difference in refractive index between the transparent substrate and the transparent electrode within a predetermined range, The light extraction efficiency is improved by suppressing reflection.

JP 2007-329176 A JP 2009-181856 A

  In the thing of said patent document 2, although the refractive index of a transparent electrode is controlled and the difference of the refractive index with a transparent substrate is adjusted, it is trying to suppress the total reflection of light, but it generate | occur | produced from the organic light emitting layer. In order to improve the light extraction efficiency, it is not sufficient to adjust the relationship between the refractive indexes of the transparent electrode and the transparent substrate, and the light extraction performance is not sufficient.

  This invention is made | formed in view of said point, and it aims at providing the organic electroluminescent element which can take out light more efficiently.

  An organic electroluminescent device according to the present invention includes a transparent substrate 1, a transparent electrode 2 provided on the transparent substrate 1, and an organic light emitting layer 3 provided on the transparent electrode 2. The transparent electrode 2 is formed by containing the metal nanowire 5 and the refractive index controlling particles 6 in the matrix resin 4, and the refractive index n1 of the transparent substrate 1, the refractive index n2 of the transparent electrode 2, and the organic The refractive index n3 of the light emitting layer 3 is set to have a relationship of n1 ≦ n2 ≦ n3 and n3−n1 ≦ 0.3.

  Thus, by setting the relationship between the refractive indexes of the three layers of the transparent substrate 1, the transparent electrode 2, and the organic light emitting layer 3 as described above, it is transparent at the interface between the organic light emitting layer 3 and the transparent electrode 2. The total reflection of light can be suppressed at the interface between the electrode 2 and the transparent substrate 1, and the refractive index control particles 6 are contained in the matrix resin 4 of the transparent electrode 2. In this case, light scattering can be generated, and total reflection of light can also be suppressed by this light scattering effect, and light can be extracted with higher efficiency.

  In the present invention, the difference between the refractive index n4 of the matrix resin 4 of the transparent electrode 2 and the refractive index n5 of the refractive index control particles 6 is 0.2 or more.

  Thus, by setting a large difference between the refractive index of the matrix resin 4 and the refractive index of the refractive index control particles 6, the light scattering effect by the refractive index control particles 6 in the transparent electrode 2 can be enhanced. A higher effect of suppressing the total reflection of light can be obtained.

  In the present invention, the matrix resin 4 of the transparent electrode 2 is a conductive polymer.

  According to this invention, in addition to the conductivity of the metal nanowire 5, the electrical properties of the transparent electrode 2 can be improved by the conductivity of the matrix resin 4 itself.

  In the present invention, the refractive index controlling particles 6 of the transparent electrode 2 are conductive metal oxide particles.

  In order to control the refractive index of the transparent electrode 2 and obtain a light scattering effect in the transparent electrode 2, the refractive index control particles 6 contained in the matrix resin 4 can be made conductive. The electrical characteristics can be improved.

  Further, the present invention is characterized in that an antireflection layer 7 is provided on the surface of the transparent substrate 1 opposite to the side on which the transparent electrode 2 is provided.

  By providing the antireflection layer 7 in this way, total reflection at the interface between the transparent substrate 1 and air can be reduced, and the light extraction efficiency can be further increased.

  According to the present invention, the refractive index n1 of the transparent substrate 1, the refractive index n2 of the transparent electrode 2, and the refractive index n3 of the organic light emitting layer 3 are set to a relationship of n1 ≦ n2 ≦ n3 and n3−n1 ≦ 0.3. As a result, total reflection of light can be suppressed at the interface between the organic light emitting layer 3 and the transparent electrode 2 and at the interface between the transparent electrode 2 and the transparent substrate 1, and the matrix resin 4 of the transparent electrode 2 can be suppressed. Since the refractive index control particles 6 are contained therein, light scattering can be generated in the transparent electrode 2, and total reflection of light can be suppressed by this light scattering effect. The light emitted from the layer 3 can be extracted with higher efficiency.

It is a schematic sectional drawing which shows an example of embodiment of this invention. It is a schematic sectional drawing which shows another example of embodiment of this invention. It is a schematic sectional drawing which shows a prior art example.

  Embodiments of the present invention will be described below.

  FIG. 1 shows an example of an embodiment of an organic EL element according to the present invention, and a light transmissive transparent electrode 2 is provided on one surface of a light transmissive transparent substrate 1. Moreover, the organic light emitting layer 3 is provided on the surface of the transparent electrode 2, and the organic EL can be formed by providing the electrode 10 on the organic light emitting layer 3. The organic light-emitting layer 3 is formed by containing an organic EL material. The organic light-emitting layer 3 is formed alone, and a hole transport layer or a hole injection layer is formed on the anode side of the organic light-emitting layer 3. An electron transport layer or an electron injection layer may be laminated on the cathode side of the light emitting layer 3 to form a plurality of organic layers.

  When the transparent electrode 2 is used as an anode, the electrode 10 serves as a cathode. When a voltage is applied between the transparent electrode 2 and the electrode 10, holes injected from the transparent electrode 2 serving as an anode, Electrons injected from the electrode 10 are recombined in the organic light emitting layer 3, and light is generated at this time. The light emitted from the organic light emitting layer 3 is extracted through the transparent electrode 2 and the transparent substrate 1.

  The transparent substrate 1 can be used without particular limitation as long as it allows light to pass therethrough, and is either an inorganic material or an organic material. Also good. Examples of the inorganic material forming the transparent substrate 1 include glass such as soda glass and non-alkali glass, quartz, and silicon. Examples of organic materials include acetate resins such as triacetyl cellulose (TAC); polyester resins such as polyethylene terephthalate (PET); polyethersulfone resins, polysulfone resins, polycarbonate resins, polyamide resins, and polyimides. Resin, polyolefin resin, acrylic resin, polynorbornene resin, cellulose resin, polyarylate resin, polystyrene resin, polyvinyl alcohol resin, polyvinyl chloride resin, polyvinylidene chloride resin, polyacrylic resin Etc. These may be used individually by 1 type and may use 2 or more types together.

  Further, the shape, structure, size and the like of the transparent substrate 1 are not particularly limited and can be appropriately selected. Examples of the shape of the transparent substrate 1 include a flat plate shape, a sheet shape, and a film shape. The structure may be, for example, a single layer structure or a laminated structure, and may be selected as appropriate. Can do.

  The transparent substrate 1 may be a single substrate, or may be one in which one or more hard coat layers are formed on the surface of the substrate. Thus, when the transparent substrate 1 is provided with a hard coat layer, the transparent electrode 2 is formed on the hard coat layer. In the present invention, the refractive index is a problem between the transparent electrode 2 and the transparent substrate 1 in the contact interface portion of the transparent substrate 1 with the transparent electrode 2. Accordingly, in the present invention, the refractive index of the transparent substrate 1 means the refractive index of the transparent substrate 1 itself if the transparent substrate 1 is a single substrate, and the transparent substrate 1 has a hard coat layer on the surface. If so, it means the refractive index of the hard coat layer.

  The hard coat layer can be formed using, for example, a reactive curable resin, that is, a hard coat coating material containing at least one of a thermosetting resin and an ionizing radiation curable resin.

  As the thermosetting resin, phenol resin, urea resin, diallyl phthalate resin, melamine resin, unsaturated polyester resin, polyurethane resin, epoxy resin, aminoalkyd resin, silicon resin, polysiloxane resin, etc. can be used. A crosslinking agent, a polymerization initiator, a curing agent, a curing accelerator, and a solvent can be added to these thermosetting resins as necessary.

  The ionizing radiation curable resin preferably has an acrylate functional group, for example, a relatively low molecular weight polyester resin, polyether resin, acrylic resin, epoxy resin, urethane resin, alkyd resin, spiro resin. Acetal resin, polybutadiene resin, polythiol polyene resin, oligomers such as (meth) acrylates of polyfunctional compounds such as polyhydric alcohol, prepolymers, and reactive diluents such as ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, Monofunctional monomers such as methylstyrene and N-vinylpyrrolidone, as well as polyfunctional monomers such as trimethylolpropane tri (meth) acrylate, hexanediol (meth) acrylate, tripropylene glycol di (meth) acrylate , Diethylene glycol di (meth) acrylate, pentaerythritol tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentyl glycol di (meth) acrylate, etc. Can be used. Furthermore, in order to make the ionizing radiation curable resin into an ultraviolet curable resin, it is preferable to incorporate a photopolymerization initiator therein. Examples of the photopolymerization initiator include acetophenones, benzophenones, α-amyloxime esters, thioxanthones, and the like. In addition to the photopolymerization initiator, a photosensitizer may be used. Examples of the photosensitizer include n-butylamine, triethylamine, tri-n-butylphosphine, and thioxanthone.

In addition, by adding high refractive index particles, that is, ultrafine particles of high refractive index metal or metal oxide, to the hard coat coating material, the refractive index is adjusted by adding high refractive index particles to the hard coat layer. Also good. The high refractive index particles preferably have a refractive index of 1.6 or more and a particle size of 0.5 to 200 nm. The compounding quantity of high refractive index particle | grains is adjusted so that it may become the range of 5-70 volume% with respect to a hard-coat layer. Examples of the ultrafine particles of the high refractive index metal or metal oxide include one or more oxide particles selected from titanium, aluminum, cerium, yttrium, zirconium, niobium, and antimony. Are, for example, ZnO (refractive index 1.90), TiO ₂ (refractive index 2.3 to 2.7), CeO ₂ (refractive index 1.95), Sb ₂ O ₅ (refractive index 1.71), SnO. ₂ , ITO (refractive index 1.95), Y ₂ O ₃ (refractive index 1.87), La ₂ O ₃ (refractive index 1.95), ZrO ₂ (refractive index 2.05), Al ₂ O ₃ ( Examples thereof include fine powders having a refractive index of 1.63).

  After applying such a hard coat coating material on the substrate and drying it as necessary, in the case of a hard coat coating material containing a thermosetting resin, it is heated and a hard coat coating material containing an ionizing radiation curable resin. In this case, the hard coat layer is formed by irradiating with ionizing rays such as ultraviolet rays to form a cured film. The coating method is not particularly limited, and various methods such as spin coating method, dip method, spray method, slide coating method, bar coating method, roll coater method, meniscus coater method, flexographic printing method, screen printing method, and bead coater method are available. Adopted.

  In the present invention, the transparent electrode 2 provided on the surface of the transparent substrate 1 is formed by containing the metal nanowire 5 and the refractive index controlling particles 6 in the matrix resin 4. The transparent electrode 2 is formed, for example, by dispersing the metal nanowires 5 and the refractive index controlling particles 6 in a resin solution and applying the resin solution to the surface of the transparent substrate 1 to form a matrix resin 4 film. Can be done.

  The matrix resin 4 for forming the film of the transparent electrode 2 is not particularly limited, but acrylic resin, polyethylene, polypropylene, polyethylene terephthalate, polymethyl methacrylate, polystyrene, polyethersulfone, polyarylate, polycarbonate resin. , Polyurethane, polyacrylonitrile, polyvinyl acetal, polyamide, polyimide, diacryl phthalate resin, cellulosic resin, polyvinyl chloride, polyvinylidene chloride, polyvinyl acetate, other thermoplastic resins, and the single amount constituting these resins Two or more types of copolymers may be mentioned.

  Moreover, as the matrix resin 4, what polymerizes by the polymerization reaction of a monomer or an oligomer can also be used. When using a resin that undergoes a photopolymerization reaction or a thermal polymerization reaction as such a resin, a monomer that generates a polymerization reaction directly or under the action of an initiator by irradiation with ionizing radiation such as ultraviolet light or an electron beam. Or an oligomer can be used and the monomer or oligomer which has an acryl group or a methacryl group is suitable. Among them, a polyfunctional binder component is preferable in order to increase the scratch resistance and hardness by crosslinking.

  As one having one functional group in one molecule, specifically, for example, isoamyl (meth) acrylate, lauryl (meth) acrylate, stearyl (meth) acrylate, butoxyethyl (meth) acrylate, ethoxy-diethylene glycol (meta ) Acrylate, methoxy-triethylene glycol (meth) acrylate, methoxy-polyethylene glycol (meth) acrylate, methoxydipropylene glycol (meth) acrylate, methoxydiethylene glycol (meth) acrylate phenoxyethyl (meth) acrylate, phenoxy-polyethylene glycol (meth) ) Acrylate, tetrahydrofurfuryl (meth) acrylate, isobornyl (meth) acrylate, 2-hydroxyethyl (meth) acrylate, -Hydroxypropyl (meth) acrylate, 2-hydroxy-3-phenoxypropyl (meth) acrylate, (meth) acrylic acid, 2- (meth) acryloyloxyethyl-succinic acid, 2- (meth) acryloyloxyethyl phthalate Acid, isooctyl (meth) acrylate, isomyristyl (meth) acrylate, 2-hydroxybutyl (meth) acrylate, methyl (meth) acrylate, ethyl (meth) acrylate, n-butyl (meth) acrylate, isobutyl (meth) acrylate, Examples include cyclohexyl methacrylate, benzyl (meth) acrylate, (meth) acryloylmorpholine, and the like.

  As those having two or more functional groups, specifically, for example, polyethylene glycol diacrylate, glycerin triacrylate, trimethylolpropane triacrylate, pentaerythritol triacrylate, pentaerythritol tetraacrylate, dipentaerythritol pentaacrylate, diester Examples thereof include pentaerythritol hexaacrylate, alkyl-modified dipentaerythritol hexaacrylate, and the compounds having a benzene ring include ethylene oxide-modified bisphenol A diacrylate, modified bisphenol A diacrylate, ethylene glycol diacrylate, and ethylene oxide propylene oxide-modified bisphenol. A diacrylate, propylene oxide tetramethylene oxide Modified bisphenol A diacrylate, bisphenol A- diepoxy - acrylic acid adduct, ethylene oxide-modified bisphenol F diacrylate, and polyfunctional acrylates or methacrylates such as polyester acrylates.

  1,2-bis (meth) acryloylthioethane, 1,3-bis (meth) acryloylthiopropane, 1,4-bis (meth) acryloylthiobutane, 1,2-bis (meth) acryloylmethylthiobenzene, The use of sulfur-containing (meth) acrylates such as 1,3-bis (meth) acryloylmethylthiobenzene is also effective for increasing the refractive index.

  Further, a light or thermal polymerization initiator may be blended in order to promote curing by ultraviolet rays or heat.

  Although what is generally marketed may be used as a photoinitiator, when it illustrates especially, benzophenone, 2, 2- dimethoxy- 1, 2- diphenyl ethane- 1-one (Ciba Specialty Chemicals Co., Ltd. product " Irgacure 651 "), 1-hydroxy-cyclohexyl-phenyl-ketone (" Irgacure 184 "manufactured by Ciba Specialty Chemicals), 2-hydroxy-2-methyl-1-phenyl-propan-1-one (Ciba Specialty Chemicals' “Darocur 1173”, Lamberti's “Esacure KL200”), Oligo (2-hydroxy-2-methyl-1-phenyl-propan-1-one) (Lamberti's “Esacure KIP150” "), 2-hydroxyethyl-phenyl-2-hydride Xyl-2-methyl-1-propan-1-one (“Irgacure 2959” manufactured by Ciba Specialty Chemicals Co., Ltd.), 2-methyl-1 (4- (methylthio) phenyl) -2-morpholinopropane-1 -ON ("Irgacure 907" manufactured by Ciba Specialty Chemicals Co., Ltd.), 2-benzyl-2-dimethylamino-1- (4-morpholinophenyl) -butanone-1 (Ciba Specialty Chemicals Co., Ltd. " Irgacure 369 "), bis (2,4,6-trimethylbenzoyl) phenylphosphine oxide (" Irgacure 819 "manufactured by Ciba Specialty Chemicals Co., Ltd.), bis (2,6-dimethoxybenzoyl) -2,4 , 4-Trimethyl-pentylphosphine oxide (Ciba Specialty Chemical) "CGI403" manufactured by KK Thioxanthone or a derivative thereof, and the like can be used, and one or a mixture of two or more of these can be used.

  Further, a tertiary amine such as triethanolamine, ethyl-4-dimethylaminobenzoate, isopentylmethylaminobenzoate or the like may be added for the purpose of photosensitization.

  As a polymerization initiator by heat, a peroxide such as benzoyl peroxide (= BPO) or an azo compound such as azobisisobutylnitrile (= AIBN) is mainly used.

  The blending amount of the photopolymerization initiator and the thermal polymerization initiator is usually preferably about 0.1 to 10 parts by mass with respect to 100 parts by mass of the composition (resin + metal nanowire).

  Moreover, you may use the monomer or oligomer which has cationic polymerizable functional groups, such as an epoxy group, a thioepoxy group, and an oxetanyl group. Further, if necessary, a photocation initiator or the like can be used in combination. These are likewise preferably polyfunctional.

  Moreover, about resin to thermally polymerize, a sol-gel type material is mentioned generally, Sol-gel type materials, such as alkoxy silane and alkoxy titanium, are preferable. Of these, alkoxysilane is preferred. The sol-gel material forms a polysiloxane structure. Specific examples of the alkoxysilane include tetraalkoxysilanes such as tetramethoxysilane, tetraethoxysilane, tetrapropoxysilane, tetraisopropoxysilane, and tetrabutoxysilane, methyltrimethoxysilane, methyltriethoxysilane, methyltripropoxysilane, and methyl. Tributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, 3- Glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropylto Trialkoxysilanes such as ethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3,4-epoxycyclohexylethyltrimethoxysilane, 3,4-epoxycyclohexylethyltriethoxysilane, dimethyldimethoxysilane, dimethyldiethoxysilane, Examples include diethyldimethoxysilane and diethyldiethoxysilane. These alkoxysilanes can be used as a partial condensate thereof. Among these, tetraalkoxysilanes or partial condensates thereof are preferable. In particular, tetramethoxysilane, tetraethoxysilane or a partial condensate thereof is preferable.

  Further, a conductive polymer can be used as the matrix resin 4. Examples of the conductive polymer include, but are not limited to, polythiophene, polyaniline, polypyrrole, polyphenylene, polyphenylene vinylene, polyacetylene, polycarbazole, and polyacetylene. These may be used alone or in combination. Moreover, in order to improve electroconductivity, you may perform doping using the following dopants. Examples of the dopant include, but are not limited to, sulfonic acid, Lewis acid, protonic acid, alkali metal, alkaline earth metal, and the like.

  By using the conductive polymer as the matrix resin 4 for forming the film of the transparent electrode 2 in this way, in addition to the conductivity by the metal nanowire 5, the film itself formed by the matrix resin 4 is also provided with conductivity. The electrical characteristics of the transparent electrode 2 can be improved.

  As the matrix resin 4, two or more kinds selected from the above-mentioned photopolymerizable resin, thermopolymerizable resin, and conductive polymer may be used in combination.

  In the present invention, the metal nanowire 5 contained in the transparent electrode 2 may be any material such as an Ag nanowire, an Au nanowire, a Cu nanowire, or a Co nanowire. Moreover, there is no restriction | limiting in particular in the manufacturing method of the metal nanowire 5, For example, well-known means, such as a liquid phase method and a gaseous-phase method, can be used. There is no restriction | limiting in particular also in a specific manufacturing method, A well-known manufacturing method can be used. For example, as a method for producing Ag nanowires, Adv. Mater. 2002, 14, P833-837, Chem. Mater. 2002, 14, P4736-4745, the above-mentioned Patent Document 2 and the like, as a method for producing Au nanowires, JP 2006-233252A and the like, as a method for producing Cu nanowires, JP 2002-266007 A and the like, As a method for producing Co nanowires, JP-A No. 2004-148771 can be cited. In particular, the above Adv. Mater. And Chem. Mater. The method for producing Ag nanowires reported in (1) can produce Ag nanowires easily and in large quantities in an aqueous system, and the conductivity of silver is the largest among metals. It can apply preferably as a manufacturing method.

  In the present invention, the average diameter of the metal nanowire 5 is preferably 200 nm or less from the viewpoint of transparency, and preferably 10 nm or more from the viewpoint of conductivity. It is preferable that the average diameter is 200 nm or less because a decrease in light transmittance can be suppressed. On the other hand, if the average diameter is 10 nm or more, the function as a conductor can be expressed significantly, and a larger average diameter is preferable because conductivity is improved. Therefore, the average diameter is more preferably 20 to 150 nm, and further preferably 40 to 150 nm. The average length of the metal nanowires 5 is preferably 1 μm or more from the viewpoint of conductivity, and preferably 100 μm or less from the viewpoint of the effect on the transparency due to aggregation. More preferably, it is 1-50 micrometers, and it is still more preferable that it is 3-50 micrometers. The average diameter and the average length of the metal nanowire 5 can be obtained from an arithmetic average of measured values of individual nanowire images by taking an electron micrograph of a sufficient number of nanowires using SEM or TEM. The length of the metal nanowire 5 should originally be obtained in a state of being straightly extended, but in reality, it is often bent, and thus the projected diameter of the metal nanowire 5 using an image analyzer from an electron micrograph. And the projected area is calculated, assuming a cylindrical body (length = projected area / projected diameter). The number of metal nanowires to be measured is preferably at least 100 or more, and more preferably 300 or more metal nanowires 5 are measured.

  In the present invention, the refractive index controlling particles 6 are contained for adjusting the refractive index of the transparent electrode 2 and preferably have a lower refractive index than the matrix resin of the transparent electrode 2. The numerical value of the refractive index of the refractive index controlling particle 6 is not particularly limited, but is preferably in the range of 1.10 to 1.45.

  Such refractive index controlling particles 6 are not particularly limited, but for example, silica, magnesium fluoride, calcium fluoride, cerium fluoride, aluminum fluoride, acrylic particles, styrene particles, urethane particles, or These composites and nanoporous particles can be mentioned.

  Further, as the refractive index control particles 6, conductive metal oxide particles can also be used. Examples of the conductive metal oxide include indium-tin oxide (ITO), indium-zinc oxide (IZO), tin oxide, a mixture of antimony-doped tin oxide (ATO) and gallium-doped zinc oxide (GZO), etc. Can be mentioned.

  By using such conductive metal oxide particles as the refractive index control particles 6 to be contained in the transparent electrode 2, in addition to the conductivity by the metal nanowires 5, the refractive index control particles 6 can also have conductivity. The electrical characteristics of the transparent electrode 2 can be improved.

  The refractive index controlling particles 6 may be solid particles, or may be hollow particles having a structure in which one outer shell covers a single cavity, or porous particles. These hollow particles and porous particles are preferable because the effect of adjusting the refractive index to be low can be obtained by the hollow portion inside the hollow particles and porous particles. Further, the shape of the refractive index control particles 6 may be spherical or irregular. Furthermore, the surface of the refractive index control particles 6 may be treated with an organometallic compound such as a silane, titanium, aluminum, or zirconium coupling agent. The refractive index controlling particles 6 can be used alone or in combination with one or more of the above-described ones. Among these, hollow silica particles are particularly preferable.

  The particle diameter of the refractive index controlling particles 6 is not particularly limited, but the average primary particle diameter is preferably less than 100 nm, and more preferably 80 nm or less. If the average primary particle diameter of the refractive index control particles 6 exceeds 100 nm, the transparency of the transparent electrode 2 may be reduced. The lower limit of the particle size of the refractive index controlling particles 6 is practically about 5 nm in terms of average primary particle size. In the present invention, the average particle diameter is a value measured by a laser diffraction / scattering method.

  The compounding quantity of the metal nanowire 5 to the resin solution which forms the transparent electrode 2 is 0.01-90 mass% of metal nanowires 5 in the transparent electrode 2 when the transparent electrode 2 is formed as described later. It is preferable to adjust and set as described above. As for content of the metal nanowire 5, 0.1-30 mass% is more preferable, More preferably, it is 0.5-10 mass%.

  The blending amount of the refractive index control particles 6 in the resin solution forming the transparent electrode 2 is set to be in the range of 10 to 80% by mass with respect to the total amount of the resin solid content and the refractive index control particles 6. Preferably, it is 20 to 70% by mass. If the blending amount of the refractive index control particles 6 is less than this range, the effect of adjusting the refractive index of the transparent electrode 2 by blending the refractive index control particles 6 may be insufficient. When the blending amount of the control particles 6 exceeds this range, the film hardness of the transparent electrode 2 is lowered, and there is a possibility that a problem occurs in the film strength.

  Here, it is essential that the resin solution contains a solvent for dissolving and dispersing solid components such as the solid content of the matrix resin 4, the metal nanowires 5, and the refractive index control particles 6. Is not particularly limited. For example, alcohols such as methanol, ethanol and isopropyl alcohol; ketones such as methyl ethyl ketone, methyl isobutyl ketone and cyclohexanone; esters such as ethyl acetate and butyl acetate; halogenated hydrocarbons; aromatic hydrocarbons such as toluene and xylene Or mixtures thereof can be used. Among these, it is preferable to use a ketone-based organic solvent. When a resin solution is prepared using a ketone-based solvent, it can be easily and uniformly applied to the surface of the transparent substrate, and the solvent after coating. Since the evaporation rate is moderate and hardly causes uneven drying, a transparent conductive film having a uniform thickness and a large area can be easily obtained. In addition to the above organic solvent, water may be used as the solvent, or an organic solvent and water may be used in combination. The amount of the solvent can uniformly dissolve and disperse each of the above solid components so that the concentration does not cause aggregation during storage after preparing the resin solution and is not too dilute during coating. Adjust as appropriate. Prepare a high-concentration resin solution by reducing the amount of solvent used within the range that satisfies this condition, store it in a state that does not take up the volume, take out the necessary amount at the time of use, and adjust the solvent to a concentration suitable for coating work. It is preferable to dilute with. When the total amount of the solid content and the solvent is 100 parts by mass, the amount of the solvent is preferably set to 50 to 99.9 parts by mass with respect to 0.1 to 50 parts by mass of the total solids, and more preferably By using 70 to 99.5 parts by mass of the solvent with respect to 0.5 to 30 parts by weight of the total solid content, a resin solution that is particularly excellent in dispersion stability and suitable for long-term storage can be obtained. . The combination of the resin and the solvent to be used is not particularly defined, but it is preferable to use a solvent in which the compounded resin is easily dissolved. Moreover, since it may melt | dissolve in the solvent to be used depending on the transparent substrate 1 to apply, it is desirable to design an appropriate solvent composition after confirming the solubility in the transparent substrate 1 in advance.

  When coating the resin solution in which the metal nanowires 5 and the refractive index controlling particles 6 are dispersed on the surface of the transparent substrate 1, any method such as spin coating, screen printing, dip coating, die coating, casting, spray coating, gravure coating, etc. Can be adopted.

  In the present invention, as an organic EL material for forming the organic light emitting layer 3 provided on the transparent electrode 2, any material conventionally used in organic EL elements can be used. For example, anthracene, naphthalene, pyrene, tetracene, coronene, perylene, phthaloperylene, naphthaloperylene, diphenylbutadiene, tetraphenylbutadiene, coumarin, oxadiazole, bisbenzoxazoline, bisstyryl, cyclopentadiene, coumarin, oxadiazole, bisbenzoxa Zoline, bisstyryl, cyclopentadiene, quinoline metal complex, tris (8-hydroxyquinolinato) aluminum complex, tris (4-methyl-8-quinolinato) aluminum complex, tris (5-phenyl-8-quinolinato) aluminum complex, amino Quinoline metal complex, benzoquinoline metal complex, tri- (p-terphenyl-4-yl) amine, pyran, quinacridone, rubrene, and derivatives thereof, or 1 Examples include aryl-2,5-di (2-thienyl) pyrrole derivatives, distyrylbenzene derivatives, styrylarylene derivatives, styrylamine derivatives, and compounds or polymers having a group consisting of these luminescent compounds as part of the molecule. be able to. Further, not only compounds derived from fluorescent dyes typified by the above compounds, but also so-called phosphorescent materials, for example, luminescent materials such as Ir complexes, Os complexes, Pt complexes, and europium complexes, or compounds or polymers having these in the molecule It can be used suitably.

  Here, in the present invention, the organic EL material is selected so that the refractive index of the organic light emitting layer 3 is higher than the refractive index of the transparent substrate 1, and the refractive indexes of the organic light emitting layer 3 and the transparent substrate 1 are selected. The organic EL material is selected so that the difference between the two becomes 0.3 or less. The smaller the difference in refractive index between the organic light emitting layer 3 and the transparent substrate 1, the better. Ideally, it is zero.

In the present invention, Al or the like is generally used as the material of the electrode 10 provided on the organic light emitting layer 3, but a laminated structure or the like may be configured by combining Al and another electrode material. it can. Such electrode material combinations include alkali metal and Al laminates, alkali metal and silver laminates, alkali metal halides and Al laminates, and alkali metal oxides and Al laminates. And a laminate of alkaline earth metal or rare earth metal and Al, and alloys of these metal species with other metals. Specifically, a laminate of Al, sodium, sodium-potassium alloy, lithium, magnesium and the like, magnesium-silver mixture, magnesium-indium mixture, aluminum-lithium alloy, LiF / Al mixture / laminate, Al / Al ₂ An O ₃ mixture or the like can be mentioned as an example. Of course, the materials and forms listed above are merely examples, and the present invention is not limited to these.

  In the organic EL element formed as described above, the transparent electrode 2 exhibits high conductivity when the metal nanowires 5 contained in the matrix resin 4 of the film come into contact with each other. The refractive index of the transparent electrode 2 can be adjusted by changing the type and content of the refractive index control particles 6 contained in the matrix resin 4.

  Here, in the present invention, when the refractive index of the transparent substrate 1 is n1, the refractive index of the transparent electrode 2 is n2, and the refractive index n3 of the organic light emitting layer 3, n1 ≦ n2 ≦ n3 is satisfied. The refractive index n2 of the transparent electrode 2 is set so that the refractive index n2 is a value between the refractive index n1 of the transparent substrate 1 and the refractive index n3 of the organic light emitting layer 3. As described above, the difference between the refractive index n1 of the transparent substrate 1 and the refractive index n3 of the organic light emitting layer 3 is 0.3 or less, that is, n3−n1 ≦ 0.3. For this reason, the difference between the refractive index n3 of the organic light emitting layer 3 and the refractive index n2 of the transparent electrode 2, the refractive index n2 of the transparent electrode 2 and the refractive index n3 of the transparent substrate 1 become small, and the light emitted from the organic light emitting layer 3 Can be prevented from being totally reflected at the interface between the organic light emitting layer 3 and the transparent electrode 2 and light transmitted through the transparent electrode 2 is incident on the transparent substrate 1. At this time, total reflection at the interface between the transparent electrode 2 and the transparent substrate 1 can be suppressed.

  Therefore, total reflection of light can be suppressed at each interface between the organic light emitting layer 3 and the transparent electrode 2, and between the transparent electrode 2 and the transparent substrate 1, and the light extraction efficiency can be increased. In addition, since the matrix resin 4 of the transparent electrode 2 contains the refractive index control particles 6, light scattering can be generated in the transparent electrode 2, and the total reflection of light is also caused by this light scattering effect. Therefore, the light extraction efficiency can be further increased.

  Here, the difference between the refractive index n4 of the matrix resin 4 of the transparent electrode 2 and the refractive index n5 of the refractive index control particles 6 is preferably 0.2 or more. Thus, when the difference between the refractive index n4 of the matrix resin 4 and the refractive index n5 of the refractive index control particles 6 is large, the light scattering effect by the refractive index control particles 6 can be enhanced, and the total reflection of light. And the light extraction efficiency can be further increased.

  FIG. 2 shows another embodiment of the present invention, in which an antireflection layer 7 is provided on the surface of the transparent substrate 1 opposite to the side on which the transparent electrode 2 is provided. By providing the antireflection layer 7 on the transparent substrate 1 in this way, it is possible to prevent the light transmitted through the transparent substrate 1 from being totally reflected at the interface between the transparent substrate 1 and air, and to improve the light extraction efficiency. It can be increased.

  A gas barrier layer may be provided on the surface of the transparent substrate 1 opposite to the side where the transparent electrode 2 is provided. By providing the gas barrier layer in this manner, moisture and oxygen can be prevented from entering the organic EL, deterioration of the organic light emitting layer 3 can be suppressed, and the life of the organic EL element can be maintained long. Is.

  Next, the present invention will be specifically described with reference to examples.

Example 1
7.50 parts by mass of ultraviolet curable acrylic resin (“A-DPH” manufactured by Shin-Nakamura Chemical Co., Ltd., refractive index 1.49) as a forming material of the matrix resin 4 and oxidized Zr particles as refractive index control particles 6 30.0 parts by mass (manufactured by CI Kasei Co., Ltd., solid content 20% by mass, refractive index 2.15) was used, and these were dissolved in a mixed solvent of 28.5 parts by mass of methyl ethyl ketone and 28.5 parts by mass of methyl isobutyl ketone. Next, silver nanowires were blended as metal nanowires 5 into this solution. The silver nanowire was used as a dispersion in which MEK was dispersed as a dispersion medium at a solid content of 30.0% by mass, and 5.0 parts by mass of this dispersion was added to the above mixed solution and mixed well. Further, 0.50 part by mass of a photopolymerization initiator 1-hydroxy-cyclohexyl-phenyl-ketone (“Irgacure 184” manufactured by Ciba Geigy) was added and mixed well, followed by stirring and mixing in a constant temperature atmosphere at 25 ° C. for 1 hour. A resin solution having a solid mass ratio upon drying of matrix resin: refractive index control particles: metal nanowires = 50: 40: 10 was prepared.

Next, a glass substrate (refractive index: 1.50) is used as the transparent substrate 1, and the above resin solution is applied to the surface of the glass substrate by spin coating, dried at room temperature (23 ° C.) for 2 minutes, and then further 120 It was dried by heating at 3 ° C. for 3 minutes. Then, the transparent electrode 2 with a film thickness of 0.5 μm was formed by irradiating and curing ultraviolet rays at an intensity of 500 mJ / cm ² . The transparent electrode 2 formed in this way had a refractive index of 1.67.

  Next, when poly (3,4-ethylenedioxythiophene) and polyanionic poly (styrenesulfonate) are abbreviated as PEDOT and the latter as PSS, the composition ratio of PEDOT: PSS = 1: 2.5 A mixed solution was prepared. And this solution was apply | coated by the spin coat method on the transparent electrode 2 formed as mentioned above, and it formed into a film thickness so that it might become a film thickness of 200 nm, and formed the hole injection layer by heating to 120 degreeC. . The refractive index of this hole injection layer made of this PEDOT: PSS film was 1.52. Next, TFB (Poly [(9,9-dioctylfluorenyl-2,7-diyl) -co- (4,4 '-(N- (4-sec-butylphenyl)) diphenylamine)]) (manufactured by American Dice Source) “Hole Transport Polymer ADS259BE”) in THF solvent was applied with a spin coater to a film thickness of 12 nm, and a TFB film was formed on the hole injection layer. A hole transport layer was formed by firing. The refractive index of this hole transport layer was 1.7. Next, a solution obtained by dissolving a red polymer (“Light Emitting polymer ATS111RE” manufactured by American Dye Source) in a THF solvent is applied onto the hole transport layer with a spin coater so as to have a film thickness of 70 nm. The organic light emitting layer 3 was formed by baking for minutes. It was 1.7 when the refractive index of this organic light emitting layer 3 was measured. Further, Ba (manufactured by high purity chemical) was formed on the organic light emitting layer 3 as an electron injection layer with a film thickness of 5 nm.

  Finally, Al (manufactured by High-Purity Chemical Co., Ltd.) was vacuum-deposited with a thickness of 80 nm on the electron injection layer to form the electrode 4 serving as a cathode. In this way, an organic EL element having a layer structure as shown in FIG. 1 was obtained.

(Example 2)
In Example 1, an organic material having a layer structure as shown in FIG. 1 was used in the same manner as in Example 1 except that a film-like substrate (PET, thickness 125 μm, refractive index 1.65) was used as the transparent substrate 1. An EL element was obtained.

(Example 3)
In Example 1, ITO particles (manufactured by CI Kasei Co., Ltd., solid content: 20% by mass, refractive index: 2.10) are used as the refractive index control particles 6. Formed. The refractive index of the transparent electrode 2 was 1.60. Otherwise, in the same manner as in Example 1, an organic EL element having a layer structure as shown in FIG. 1 was obtained.

Example 4
In Example 1, instead of acrylic resin, poly (3,4-ethylenedioxythiophene) and polyanionic poly (styrene sulfonate) are used as the forming material of the matrix resin 4, and PEDOT: PSS = 1: 2.5. A transparent electrode 2 was formed in the same manner as in Example 1 except that the solution mixed at the composition ratio was used. In this conductive electrode 2, the refractive index of the matrix resin was 1.52, and the refractive index of the transparent electrode 2 was 1.68. Otherwise, in the same manner as in Example 1, an organic EL element having a layer structure as shown in FIG. 1 was obtained.

(Example 5)
In Example 2, the antireflection layer 7 made of a low refractive index film having a film thickness of 100 nm and a refractive index of 1.35 was provided on the surface opposite to the transparent electrode 2 of the transparent substrate 1 made of a PET base material. The antireflection layer 7 was formed by coating the surface of the transparent substrate 1 with the coating material composition prepared as follows.

First, 356 parts by mass of methanol was added to 208 parts by mass of tetraethoxysilane, and 18 parts by mass of water and 18 parts by mass of 0.01N hydrochloric acid aqueous solution (“H ₂ O” / “OR” = 0.5 ”were added. This mixture was stirred for 2 hours in a constant temperature bath at 25 ° C. to obtain a silicone resin having a weight average molecular weight adjusted to 850 as a matrix forming material. In addition, hollow silica IPA (isopropanol) dispersion sol (solid content 20% by mass, average primary particle diameter 35 nm, outer shell thickness about 8 nm, manufactured by Catalyst Kasei Kogyo Co., Ltd.) is used as a hollow silica fine particle. Silica fine particles / silicone resin (condensation compound equivalent) is blended so that the mass ratio is 40/60 on a solid basis, so that the total solid content is 3% by mass. By dilution with methanol to prepare a coating material composition.

  Otherwise, in the same manner as in Example 1, an organic EL element having a layer structure as shown in FIG. 2 was obtained.

(Comparative Example 1)
A transparent electrode 2 was formed on the surface of the transparent substrate 1 by sputtering an ITO film (refractive index 2.1). Otherwise, in the same manner as in Example 1, an organic EL element having a layer structure as shown in FIG. 3 was obtained.

(Comparative Example 2)
13.50 parts by mass of UV curable acrylic resin (“A-DPH” manufactured by Shin-Nakamura Chemical Co., Ltd., refractive index 1.49) is used as a material for forming the matrix resin 4, and 40.5 parts by mass of methyl ethyl ketone It melt | dissolved in the mixed solvent of 40.5 mass parts of methyl isobutyl ketone. Next, silver nanowires were blended as metal nanowires 5 into this solution. The silver nanowire was used as a dispersion in which MEK was dispersed as a dispersion medium at a solid content of 30.0% by mass, and 5.0 parts by mass of this dispersion was added to the above mixed solution and mixed well. Further, 0.50 part by mass of a photopolymerization initiator 1-hydroxy-cyclohexyl-phenyl-ketone (“Irgacure 184” manufactured by Ciba Geigy) was added and mixed well, followed by stirring and mixing in a constant temperature atmosphere at 25 ° C. for 1 hour. A resin solution in which the solid content mass ratio at the time of drying was matrix resin: refractive index control particles: metal nanowires = 90: 0: 10 was prepared.

Next, a glass substrate (refractive index: 1.50) is used as the transparent substrate 1, and the above resin solution is applied to the surface of the glass substrate by spin coating, dried at room temperature (23 ° C.) for 2 minutes, and then further 120 It was dried by heating at 3 ° C. for 3 minutes. Then, the transparent electrode 2 with a film thickness of 0.5 μm was formed by irradiating and curing ultraviolet rays at an intensity of 500 mJ / cm ² . The refractive index of the transparent electrode 2 thus formed was 1.49.

Other than that, an organic EL device was obtained in the same manner as in Example 1.
(Comparative Example 3)
In Comparative Example 2, as a material for forming the matrix resin 4, poly (3,4-ethylenedioxythiophene) and polyanionic poly (styrenesulfonate) are used instead of acrylic resin, and PEDOT: PSS = 1: 2.5. A transparent electrode 2 was formed in the same manner as in Example 1 except that the solution mixed at the composition ratio was used. In this conductive electrode 2, the refractive index of the matrix resin was 1.52, and the refractive index of the transparent electrode 2 was 1.68. And otherwise, it carried out similarly to the comparative example 2, and obtained the organic EL element.

  About the organic EL of Examples 1-5 produced as mentioned above, the electric current value at the time of 2V application and an external quantum efficiency ratio were measured.

  Here, the current value when 2 V was applied to the organic EL element was measured using a DC power source (manufactured by Caseley).

Similarly, a DC power source (manufactured by Caseley) was used, the current flowing inside the organic EL element was fixed at 10 mA / cm ^2, and the characteristics of the organic EL element were evaluated using a luminance meter (manufactured by Topcon). Then, front luminance (cd / m ² ) and current efficiency (cd / A) are measured from −80 ° to + 80 ° in angular orientations every 10 °, and based on this, the total luminous flux [external quantum efficiency (%)] Was calculated. In Table 1, “External quantum efficiency ratio” is shown as a comparative example 1 with “1.0” as the magnification.

  As seen in Table 1, the relationship between the refractive index n1 of the transparent substrate, the refractive index n2 of the transparent electrode, and the refractive index n3 of the organic light emitting layer is n1 ≦ n3 ≦ n2 in Comparative Example 1 where the transparent electrode is ITO. In Comparative Example 2, n2 ≦ n1 ≦ n3, whereas in Examples 1-5, the relationship is n1 ≦ n2 ≦ n3. It is confirmed that the light extraction efficiency is high.

  In Comparative Example 3 corresponding to Patent Document 2, the relationship is n1 ≦ n2 ≦ n3. However, since the refractive index control particles are not contained in the transparent electrode, the light scattering effect cannot be obtained, and the light extraction efficiency is improved. It is confirmed that the effect to do is insufficient.

DESCRIPTION OF SYMBOLS 1 Transparent substrate 2 Transparent electrode 3 Organic light emitting layer 4 Matrix resin 5 Metal nanowire 6 Refractive index control particle 7 Antireflection layer

Claims (5)

  An organic electroluminescent device comprising a transparent substrate, a transparent electrode provided on the transparent substrate, and an organic light emitting layer provided on the transparent electrode, wherein the transparent electrode is a metal nanowire and a refractor in a matrix resin. The refractive index n1 of the transparent substrate, the refractive index n2 of the transparent electrode, and the refractive index n3 of the organic light emitting layer are n1 ≦ n2 ≦ n3 and n3−n1 ≦ 0.3. An organic electroluminescence element characterized by being set to a relationship of   2. The organic electroluminescence device according to claim 1, wherein a difference between a refractive index n <b> 4 of the matrix resin of the transparent electrode and a refractive index n <b> 5 of the refractive index control particles is 0.2 or more.   3. The organic electroluminescence element according to claim 1, wherein the matrix resin of the transparent electrode is a conductive polymer.   The organic electroluminescence device according to any one of claims 1 to 3, wherein the refractive index control particles of the transparent electrode are conductive metal oxide particles.   The organic electroluminescence device according to any one of claims 1 to 4, wherein an antireflection layer is provided on the surface of the transparent substrate opposite to the side on which the transparent electrode is provided.

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