JP2011070792A - Method for manufacturing transparent electrode, and transparent electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for manufacturing a transparent electrode having high coating film homogeneity by use of a release film which never causes spike-like projections on the film surface even if heated, nor causes cracks even if transferred, and also to provide a transparent electrode obtained by the method. <P>SOLUTION: In the method for manufacturing the transparent electrode by forming a transparent conductive layer containing at least conductive metal fine particles on a release surface of a release film and transferring the transparent conductive layer onto a transparent substrate, the release surface of the release film has smoothness Ry of 1 nm or more and 50 nm or less, surface energy of 20 mM/m or more and 50 mM/m or less, and pencil hardness of H or more and 5H or less, measured by a pencil hardness test method based on JISK 5600. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a method for producing a transparent electrode having high conductivity and transparency, and also having a high level of smoothness for use in an organic EL device and the like, and a transparent electrode obtained thereby.

  In recent years, with increasing demand for thin TVs, various types of display technologies such as liquid crystal, plasma, organic EL, and field emission have been actively developed. The transparent electrode is an indispensable constituent technology even in various types of displays. In addition to TVs, transparent electrodes are an indispensable technical element in touch panels, mobile phones, electronic paper, various solar cells, and various electroluminescence light control elements. In particular, in applications such as organic EL and organic thin-film solar cells, current leakage due to unevenness on the surface of the transparent electrode and distortion of layer formation are likely to cause light emission failure and power generation failure, and the transparent electrode surface is highly smooth. Sex is required.

  Transparent electrodes used in organic EL and organic thin-film solar cells are formed by depositing an indium-tin composite oxide (ITO) film on a transparent substrate such as glass or a transparent plastic film by vacuum deposition or sputtering. ITO transparent electrodes have been mainly used. However, a transparent electrode using a vacuum deposition method or a sputtering method has a problem in that the productivity is low and thus the manufacturing cost is high, and since it is inferior in flexibility, it cannot be applied to a device application requiring flexibility.

  In recent years, as a method for solving this problem, a transparent electrode is formed by applying a metal nanowire dispersion such as silver, or a transparent conductive layer containing metal nanowires and a binder is formed on a release film, and then released. A transfer method for forming a transparent electrode by transferring a transparent conductive layer on a mold film onto a transparent substrate has been proposed (see, for example, Patent Document 1).

US2007 / 0074316A1 Specification

  However, in the method of forming a transparent electrode by applying the metal nanowire dispersion described in Patent Document 1, a part of the metal nanowire protrudes on the surface, so that high smoothness is required as the electrode surface. It has a problem that it cannot be applied to technical uses such as organic EL elements.

  On the other hand, in the transfer method in which a transparent electrode is formed by forming a transparent conductive layer on a release film by a wet coating method and transferring the transparent conductive layer onto a transparent substrate, the smoothness of the release film surface is This is reflected in the smoothness of the transparent conductive layer as it is. In particular, in a technical field where high smoothness is required on the electrode surface, a transfer method may be used, and a transfer method using a highly smooth polyethylene film or polyethylene naphthalate film is known. In the method of transferring a transparent conductive layer containing metal nanowires and a binder described in Patent Document 1, when a transparent conductive layer is formed on a release film, ultraviolet curing due to the influence of moisture present in the transparent conductive layer Heat treatment is required to suppress poor curing of adhesives such as mold resins and thermosetting resins. However, when heat treatment is performed after forming a transparent conductive layer on a polyethylene film or polyethylene naphthalate film, spike-like protrusions are formed on the film surface, and the surface smoothness of the transparent conductive layer after transfer is impaired. I have a problem. In addition, when a release layer using a silicone-based polymer compound or a fluorinated polymer compound is formed on the release film in order to improve the release property, the surface energy of the release film surface is lowered and applied to the release film. There is a problem that the metal nanowire dispersion liquid cannot be applied uniformly, and a problem that the release layer has insufficient hardness, causing cracks during transfer and leaving a part of the release layer in the transparent conductive layer. It was. In addition, when a release layer containing starch is formed for the purpose of improving peelability, there is a problem in that a smooth transparent conductive layer cannot be obtained even if metal nanowires are sunk into the release layer during bonding.

  The present invention has been made in view of the above problems, and its purpose is to provide a release film that does not produce spike-like protrusions on the film surface even when heated, and does not cause cracks even when transferred. It is an object of the present invention to provide a method for producing a transparent electrode having high coating film uniformity and a transparent electrode obtained thereby.

  The above object of the present invention is achieved by the following configurations.

  1. A transparent electrode manufacturing method for manufacturing a transparent electrode by forming a transparent conductive layer containing at least conductive metal fine particles on a release surface of a release film and then transferring the transparent conductive layer onto a transparent substrate. The release surface of the release film has a smoothness Ry of 1 nm or more and 50 nm or less, a surface energy of 20 mN / m or more and 50 mN / m or less, and according to a pencil hardness test method according to JISK5600. A method for producing a transparent electrode, wherein the measured pencil hardness is from H to 5H.

  2. 2. The method for producing a transparent electrode according to 1 above, wherein the conductive metal fine particles are metal nanowires.

  3. A transparent electrode produced by the method for producing a transparent electrode according to 1 or 2 above.

  According to the present invention, a method for producing a transparent electrode having a high coating film uniformity using a release film that does not cause spike-like protrusions on the film surface even when heated and does not cause cracks even when transferred. And a transparent electrode obtained thereby.

  Hereinafter, embodiments for carrying out the present invention will be described in detail.

  As a result of intensive studies in view of the above problems, the inventor formed a transparent conductive layer containing at least conductive metal fine particles on the release surface of the release film, and then placed the transparent conductive layer on a transparent substrate. A transparent electrode production method for producing a transparent electrode by transferring to a mold, wherein the release surface of the release film has a smoothness Ry of 1 nm to 50 nm, a surface energy of 20 mN / m to 50 mN. / M or less, and the pencil hardness measured according to the pencil hardness test method according to JISK5600 is H or more and 5H or less. Method for producing transparent electrode having high coating film homogeneity using release film which does not cause protrusion and does not cause crack even if transferred, and transparent electrode obtained thereby Found that can achieve a completed the invention.

  That is, a transparent electrode made of conductive metal fine particles formed according to the method defined in the present invention is characterized by being transparent, low in resistance, and having high smoothness. In the method for producing a transparent electrode of the present invention, as the physical properties of the release film to be applied, the surface energy is controlled to 20 mN / m or more and 50 mN / m or less so that the conductive metal fine particles are uniformly formed on the release film. A transparent conductive layer having high smoothness can be obtained by controlling the smoothness Ry of the release surface of the release film to 1 nm or more and 50 nm or less. Moreover, by controlling the surface hardness of the release film to H or more and 5H or less by evaluation by a pencil hardness test according to JISK5600, the release film is not cracked, and conductive metal fine particles are not bonded at the time of bonding. Since it does not sink into the release film, a smooth transparent conductive layer can be obtained. Therefore, a high-performance transparent electrode can be obtained, and it is very preferable as a transparent electrode for organic EL elements or the like that require particularly high smoothness.

  Hereinafter, the manufacturing method of the transparent electrode of this invention and the detail of a transparent electrode are demonstrated.

<Release film>
The release film according to the present invention is a donor film for forming a transparent conductive layer and transferring it onto a transparent substrate. In the method for producing a transparent electrode of the present invention, the smoothness Ry is 1 nm or more and 50 nm or less, the surface energy is 20 mN / m or more and 50 mN / m or less, and according to the pencil hardness test method according to JIS K 5600. A release film having a measured pencil hardness of H or more and 5H or less is used.

  The release film according to the present invention has a smoothness Ry of 1 nm or more and 50 nm or less, a surface energy of 20 mN / m or more and 50 mN / m or less, and was measured according to a pencil hardness test method according to JIS K 5600. There is no limitation as long as the pencil hardness satisfies H or more and 5H or less. For example, a film in which a layer is formed on a plastic film and the surface energy is adjusted by surface treatment can be used. Usually, the plastic film has a hardness in the range of 4B to HB, and has a low hardness for use as the release film of the present invention. Moreover, when a transparent conductive layer is formed on a plastic film as it is and heated for removing moisture, spike-like protrusions are generated and the smoothness is impaired. Therefore, by forming a hard release layer on the plastic film, it is possible to give the film surface hardness and to suppress protrusions generated on the plastic film.

[Smoothness]
In the present invention, one characteristic is that the smoothness Ry of the release surface of the release film to be applied is 1 nm or more and 50 nm or less.

  In general, Ry: maximum height (height difference between the top and bottom of the surface) and Ra: arithmetic average roughness are used as indices representing the smoothness of the film surface, both of which are JIS B601 (1994). It is a value according to the surface roughness specified in).

  In the release film according to the present invention, the smoothness Ry of the release film surface is 1 nm or more and 50 nm or less. If smoothness Ry of the surface of a release film is 50 nm or less, generation | occurrence | production of the unevenness | corrugation in the transparent conductive layer transcribe | transferred can be suppressed, As a result, the light emission nonuniformity and light emission defect of an organic EL element can be prevented. Moreover, if surface smoothness Ry is 1 nm or more, the productivity of a film is favorable and it is preferable from an economical viewpoint. Furthermore, in technical applications such as organic EL devices that require uniformity of the surface of the transparent conductive layer, the surface smoothness of the release film is preferably Ra ≦ 5 nm.

  A commercially available atomic force microscope (AFM) can be used for the measurement of Ry and Ra specified in the present invention, and can be measured by the following method, for example.

  Using an SPI 3800N probe station and SPA400 multifunctional unit manufactured by Seiko Instruments Inc. as the AFM, set the sample cut to a size of about 1 cm square on a horizontal sample stage on the piezo scanner, and place the cantilever on the sample surface. When approaching and reaching the region where the atomic force works, scanning is performed in the XY direction, and the unevenness of the sample at that time is captured by the displacement of the piezo in the Z direction. A piezo scanner that can scan XY 20 μm and Z 2 μm is used. The cantilever is a silicon cantilever SI-DF20 manufactured by Seiko Instruments Inc., which has a resonance frequency of 120 to 150 kHz and a spring constant of 12 to 20 N / m, and is measured in a DFM mode (Dynamic Force Mode). A measurement area of 80 × 80 μm is measured at a scanning frequency of 1 Hz.

[Surface energy]
In this invention, it is one characteristic that the surface energy of the release surface of the release film to be applied is 20 mN / m or more and 50 mN / m or less. If the surface energy is 20 mN / m or more, good wettability can be obtained, and the conductive metal fine particles can be applied uniformly. Further, if the surface energy is 50 mN / m or less, the conductive metal fine particles are appropriately adhered to the release film, and the conductive metal fine particles can be quickly peeled off from the release film when the release film is peeled off. High smoothness of the conductive layer can be obtained. Furthermore, from the viewpoint of ease of peeling, the surface energy is preferably 20 mN / m or more and 40 mN / m or less.

  The surface energy of the release film according to the present invention is a value representing the wettability of the release film measured using a contact angle method with water and diiodomethane as standard solutions. Specifically, using the dynamic contact angle measurement mode of the contact angle surface analyzer VCA Optima-XE (manufactured by AST), the contact angle is measured by dropping water droplets using ultrapure water and diiodomethane as standard solutions. Then, the surface energy in a two-component system can be calculated and obtained.

〔hardness〕
The present invention is characterized in that the pencil hardness measured according to the pencil hardness test method according to JIS K 5600 of the release surface of the release film to be applied is H or more and 5H or less.

  “Hardness” as used in the present invention is a value obtained by a pencil hardness test in accordance with JIS K 5600, and represents the hardness of the release surface of the release film. For example, a scratch hardness tester (Cotec Corp.) It can obtain | require by measuring using a product.

  If the release film has a hardness of H or more, it is possible to suppress the occurrence of cracks in the release film during transfer and to prevent the release film from being transferred to the transparent conductive layer. Moreover, when the release film has a hardness of HB or less, the metal nanowires sink into the release layer during bonding, and a smooth transparent conductive layer cannot be obtained even if transferred. On the other hand, if the hardness is too high, it becomes difficult to wind the release film on a roll or wind it so as not to cause cracks, and it becomes difficult to perform transfer with a highly productive roll press. Even if cracks do not occur, a film having a hardness of 6H or more has low versatility and high production costs.

[Base material: Plastic film]
The material of the plastic film applicable to the release film according to the present invention is not particularly limited, and various known film materials can be used. For example, synthetic resin such as polyethylene terephthalate, polypropylene, polycarbonate, polystyrene, polyamide, polyamideimide, polyethylene, polyvinyl chloride, artificial resin film such as cellulose acetate, or a composite film or composite sheet thereof. It is done. Above all. From the viewpoint of producing a film having excellent heat resistance and strength, low cost and high smoothness, it is preferable to use a biaxially stretched polyethylene terephthalate film or a biaxially stretched polyethylene naphthalate film.

  Moreover, there is no restriction | limiting in particular as thickness of a plastic film, The thing of the range of 10-200 micrometers can use easily the manufacture of a film without a wrinkle, a crack, etc. The point which can hold down manufacturing cost low To preferred.

[Release layer]
In the release film which concerns on this invention, it is preferable to install a release layer on the plastic film which is a base material.

  Specific examples of the compound for forming a hard release layer include ionizing radiation curable resins and thermosetting resins that are cured by ultraviolet rays, electron beams, or heat, preferably ionizing radiation curable resins. is there.

  Examples of the ionizing radiation curable resin applicable to the present invention include compounds having one or more unsaturated bonds, such as compounds having an acrylate functional group. Examples of the compound having one unsaturated bond include ethyl (meth) acrylate, ethylhexyl (meth) acrylate, styrene, methylstyrene, N-vinylpyrrolidone and the like. Examples of the compound having two or more unsaturated bonds include polymethylolpropane tri (meth) acrylate, hexanediol di (meth) acrylate, tripropylene glycol di (meth) acrylate, diethylene glycol di (meth) acrylate, and pentaerythritol. Multifunctional compounds such as tri (meth) acrylate, dipentaerythritol hexa (meth) acrylate, 1,6-hexanediol di (meth) acrylate, neopentylglycol di (meth) acrylate, and reaction products such as (meth) arylate (For example, poly (meth) acrylate ester of polyhydric alcohol). In the present invention, “(meth) acrylate” refers to methacrylate and acrylate.

  In addition to the above compounds, relatively low molecular weight polyester resins having unsaturated double bonds, polyether resins, acrylic resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyene resins, etc. It can be used as an ionizing radiation curable resin. In addition, by appropriately selecting, mixing and using these resins, it is possible to adjust to the smoothness, hardness and surface energy defined in the present invention.

  In the release layer according to the present invention, when an ionizing radiation curable resin is used as an ultraviolet curable resin, it is preferable to use a photopolymerization initiator. As the photopolymerization initiator, in the case of a resin system having a radical polymerizable unsaturated group, it is preferable to use acetophenones, benzophenones, thioxanthones, benzoin, benzoin methyl ether or the like alone or in combination. In the case of a resin system having a cationic polymerizable functional group, an aromatic diazonium salt, an aromatic sulfonium salt, an aromatic iodonium salt, a metallocene compound, a benzoin sulfonic acid ester or the like is used alone or as a mixture as a photopolymerization initiator. It is preferable. The addition amount of the photopolymerization initiator is preferably used in the range of 0.1 to 10 parts by mass with respect to 100 parts by mass of the ionizing radiation curable composition.

  In addition, the release layer-forming composition includes a solvent, a dispersant, a surfactant, an antistatic agent, a silane coupling agent, for the purpose of increasing curability and improving wettability to a plastic substrate. Add thickeners, anti-coloring agents, coloring agents (pigments, dyes), antifoaming agents, leveling agents, flame retardants, UV absorbers, adhesion promoters, polymerization inhibitors, antioxidants, surface modifiers, etc. It may be.

  In particular, a leveling agent is preferable from the viewpoint of improving wettability to a plastic substrate and improving smoothness of a release layer on a plastic substrate. Moreover, a silica particle is mentioned as a surface modifier, and it is preferable from a viewpoint of improving the hardness of the release film surface.

  Specifically, in the step of forming the release layer, the release layer composition is applied onto a plastic film to form a coating film, and the resulting coating film is irradiated with ionizing radiation or the top of the application. Done by curing. The coating method is not particularly limited. For example, spin coating method, dip method, spray method, die coating method, bar coating method, roll coater method, meniscus coater method, flexographic printing method, screen printing method, pea coater method, etc. Can be mentioned.

[Surface treatment of release layer film]
In this invention, in order to adjust the surface energy of the mold release surface of a mold release layer film, it is preferable to surface-treat with respect to a mold release surface. As a surface treatment applicable to the present invention, a conventionally known technique is applied to make the release surface hydrophilic or hydrophobic. Examples of these surface treatment methods include surface treatments such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, plasma treatment, atmospheric pressure plasma treatment, and laser treatment.

<< Method for producing transparent electrode, transparent electrode >>
In the method for producing a transparent electrode of the present invention, after forming a transparent conductive layer containing conductive metal fine particles on the release surface of the release film described above, the transparent conductive layer is transferred to a transparent substrate. Thus, a transparent electrode is manufactured.

  In the present invention, it is preferable to transfer the transparent conductive layer formed on the release film onto the transparent substrate using an adhesive, and the adhesive applicable to the present invention should be transparent in the visible region. In other words, there is no particular limitation as long as it has sufficient transmittance. As long as it is transparent, a curable resin or a thermoplastic resin may be used. Examples of the curable resins include thermosetting resins, ultraviolet curable resins, and electron beam curable resins. Among these curable resins, the equipment for resin curing is simple and excellent in workability. Therefore, an ultraviolet curable resin is preferable. The adhesive is preferably an acrylic polymer or an epoxy polymer from the viewpoint of transparency. In the present invention, the adhesive layer may be provided on a conductive layer formed on a release film, or may be provided on a transparent substrate.

  The bonding method is not particularly limited and can be performed by a sheet press, a roll press or the like, but is preferably performed using a roll press machine. The roll press is a method in which a film to be bonded is sandwiched between the rolls, and the rolls are rotated. The roll press is uniformly pressurized and is preferable to the productivity than the sheet press.

  In addition, a transparent electrode having a smooth surface is required for an electrode for an organic EL element. In particular, in the case of an electrode for an organic EL element, an ultra thin film of an organic compound is formed on the transparent electrode. Is required to have excellent surface smoothness. Since the smoothness of the release film is transferred to the conductive layer on the transparent substrate by the above method, it is preferable for an electrode for an organic EL device, but its use is not limited.

[Conductive metal fine particles]
The transparent electrode of the present invention is formed by transferring a transparent conductive layer containing conductive metal fine particles to a transparent substrate. The conductive metal fine particle applicable to the present invention refers to a metal in the form of fine particles whose minor axis is from atomic scale to nm size.

  In the conductive metal fine particles according to the present invention, as long as the minor axis of the particle diameter is nm size, the shape may be a particle shape, a rod shape or a wire shape. A wire shape is preferable from the viewpoint.

(Metal nanowires)
In the present invention, the conductive metal fine particles are preferably metal nanowires. In general, the metal nanowire refers to a linear structure having a metal element as a main component. In particular, the metal nanowire according to the present invention exhibits conductivity when a large number of linear structures having a diameter of nm size from the atomic scale are formed in a mesh shape.

  As a metal nanowire applicable to the present invention, in order to form a long conductive path with one metal nanowire, the average length is preferably 3 μm or more, more preferably 3 to 500 μm, particularly 3 It is preferable that it is -300 micrometers. In addition, the relative standard deviation of the length is preferably 40% or less. Moreover, it is preferable that an average diameter is small from a transparency viewpoint, On the other hand, the larger one is preferable from an electroconductive viewpoint. In this invention, 10-300 nm is preferable as an average diameter of metal nanowire, and it is more preferable that it is 30-200 nm. In addition, the relative standard deviation of the diameter is preferably 20% or less.

  There is no restriction | limiting in particular as a metal composition of the metal nanowire which concerns on this invention, Although it can comprise from the 1 type or several metal of a noble metal element and a base metal element, it is a noble metal (For example, gold, platinum, silver, palladium, Rhodium, iridium, ruthenium, osmium, etc.) and at least one metal belonging to the group consisting of iron, cobalt, copper, and tin is preferable, and at least silver is more preferable from the viewpoint of conductivity. In order to achieve both conductivity and stability (sulfurization and oxidation resistance of metal nanowires and migration resistance), it is also preferable to include silver and at least one metal belonging to a noble metal other than silver.

  When the metal nanowire according to the present invention includes two or more kinds of metal elements, for example, the metal composition may be different between the inside and the surface of the metal nanowire, or the entire metal nanowire has the same metal composition. You may have.

  In the present invention, the means for producing the metal nanowire is not particularly limited, and for example, known means such as a liquid phase method and a gas phase method can be used. Moreover, there is no restriction | limiting in particular in a specific manufacturing method, A well-known manufacturing method can be used. For example, as a method for producing silver nanowires, Adv. Mater. , 2002, 14, 833-837; Chem. Mater. , 2002, 14, 4736-4745, etc., as a method for producing gold nanowires, Japanese Patent Application Laid-Open No. 2006-233252, etc., as a method for producing copper nanowires, Japanese Patent Application Laid-Open No. 2002-266007, etc. For example, Japanese Patent Application Laid-Open No. 2004-149871 can be referred to. In particular, Adv. Mater. And Chem. Mater. The method for producing silver nanowires reported in (1) can be easily produced in an aqueous system, and can be preferably applied as a method for producing metal nanowires according to the present invention because of its high electrical conductivity.

[Transparent conductive layer]
In this invention, after forming a transparent conductive layer on a release film using the coating liquid containing the conductive metal fine particles according to the present invention, the transparent conductive layer is transferred to a transparent substrate to transfer the transparent electrode. Make it.

  The method for forming the transparent conductive layer on the release film according to the present invention is not particularly limited as long as it is a liquid phase method in which a coating liquid containing conductive metal fine particles is applied and dried to form a film, and a roll coating method, It is preferable to use a coating method such as a bar coating method, a dip coating method, a spin coating method, a casting method, a die coating method, a blade coating method, a bar coating method, a gravure coating method, a curtain coating method, a spray coating method, or a doctor coating method. . Further, the transparent conductive layer containing at least conductive metal fine particles uses a dispersant for ensuring the dispersibility of the conductive metal fine particles, or a binder for holding the conductive metal fine particles in the film after coating and drying. Also good. As the binder, for example, a polyester resin, an acrylic resin, a polyurethane resin, an acrylic urethane resin, a polycarbonate resin, a cellulose resin, a polyvinyl acetal resin, or the like can be used alone or in combination. The solvent used in the coating solution containing conductive metal fine particles is not particularly limited. For example, water, organic solvents (for example, alcohols such as methanol, ketones such as acetone, amides such as formamide, etc.) , Sulfoxides such as dimethyl sulfoxide, esters such as ethyl acetate, ethers, and the like), and mixed solvents thereof.

  The thickness of the transparent conductive layer according to the present invention varies depending on the shape and content of the conductive metal fine particles and the transparent conductive material to be used, but as a rough guide, the average diameter of the conductive metal fine particles is preferably 500 nm or less. . Further, it is preferable to reduce the thickness of the transparent conductive layer according to the present invention by pressurization or the like because the network formation of conductive metal fine particles in the thickness direction can be made dense.

(Transparent substrate)
The transparent substrate used for the production of the transparent electrode of the present invention is not particularly limited as long as it has high light transmittance. For example, it has excellent hardness as a substrate, and transparent conductivity to the surface thereof. A glass substrate, a resin substrate, a resin film, and the like are preferable in terms of ease of formation of the layer, and a transparent resin film is preferably used from the viewpoint of lightness and flexibility.

  In the present invention, the transparent resin film that can be preferably used as the transparent substrate is not particularly limited, and the material, shape, structure, thickness and the like can be appropriately selected from known ones. For example, polyester resin films such as polyethylene terephthalate (PET), polyethylene naphthalate, modified polyester, polyethylene (PE) resin films, polypropylene (PP) resin films, polystyrene resin films, polyolefin resin films such as cyclic olefin resins, Vinyl resin films such as polyvinyl chloride and polyvinylidene chloride, polyether ether ketone (PEEK) resin film, polysulfone (PSF) resin film, polyether sulfone (PES) resin film, polycarbonate (PC) resin film, polyamide resin A film, a polyimide resin film, an acrylic resin film, a triacetyl cellulose (TAC) resin film, and the like can be given. If the resin film transmittance of 80% or more in nm), can be preferably applied as a transparent resin substrate according to the present invention. Among them, from the viewpoint of transparency, heat resistance, ease of handling, strength and cost, it is preferably a biaxially stretched polyethylene terephthalate film, a biaxially stretched polyethylene naphthalate film, a polyethersulfone film, or a polycarbonate film. More preferred are a stretched polyethylene terephthalate film and a biaxially stretched polyethylene naphthalate film.

  The transparent substrate used in the present invention can be subjected to a surface treatment or an easy-adhesion layer in order to adjust the wettability and adhesiveness of the adhesive. A conventionally well-known technique can be used about a surface treatment or an easily bonding layer. For example, the surface treatment includes surface activation treatment such as corona discharge treatment, flame treatment, ultraviolet treatment, high frequency treatment, glow discharge treatment, active plasma treatment, and laser treatment. Examples of the easy adhesion layer include polyester, polyamide, polyurethane, vinyl copolymer, butadiene copolymer, acrylic copolymer, vinylidene copolymer, and epoxy copolymer.

  When the transparent substrate is a biaxially stretched polyethylene terephthalate film, the interface reflection between the film substrate and the easy-adhesion layer is achieved by setting the refractive index of the easy-adhesion layer adjacent to the film to 1.57 to 1.63. Since it can reduce and can improve the transmittance | permeability, it is more preferable. The method for adjusting the refractive index can be carried out by appropriately adjusting the ratio of the oxide sol having a relatively high refractive index such as tin oxide sol or cerium oxide sol and the binder resin. The easy adhesion layer may be a single layer, but may be composed of two or more layers in order to improve adhesion.

<Transparent electrode>
In the transparent electrode of the present invention, the total light transmittance of the transparent conductive layer containing conductive metal fine particles is 60% or more, preferably 70% or more, particularly preferably 80% or more. The total light transmittance can be measured according to a known method using a spectrophotometer or the like.

In the transparent electrode of the present invention, the electrical resistance value of the transparent conductive layer containing the conductive metal fine particles is preferably 10 ³ Ω / □ or less as the surface specific resistance, and preferably 10 ² Ω / □ or less. More preferably, it is 10Ω / □ or less. The surface specific resistance can be measured according to, for example, JIS K6911, ASTM D257, etc., and can be easily measured using a commercially available surface resistivity meter. The surface specific resistance only needs to satisfy the above-mentioned surface specific resistance in the state of conductive metal fine particles alone, and the conductive metal fine particles function as a bus electrode. Conductivity of the conductive metal fine particle-containing conductive layer can be made uniform. The surface resistivity of the conductive polymer is 10 ⁴ Ω / □ or more and 10 ⁹ Ω, which can make the conductivity of the conductive metal fine particle-containing conductive layer uniform without affecting current leakage between the conductive metal fine particle-containing conductive layers. / □ or less, more preferably 10 ⁶ Ω / □ or more and 10 ⁹ Ω / □ or less.

  An anchor coat, a hard coat layer, etc. can also be provided to the transparent electrode of the present invention. If necessary, a conductive layer containing a conductive polymer or a metal oxide may be further provided.

  The transparent electrode of the present invention can be used for transparent electrodes such as LCDs, organic EL elements, plasma displays, electrochromic displays, solar cells, touch panels, electronic papers and electromagnetic shielding materials, etc., but has excellent conductivity and transparency. In addition, since it has high smoothness, it is preferably used for an organic EL device.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples, but the present invention is not limited thereto. In addition, although the display of "part" or "%" is used in an Example, unless otherwise indicated, "part by mass" or "mass%" is represented.

Example 1
<Preparation of release layer coating solution>
(Preparation of release layer coating solution 1)
To 120 parts by mass of ethyl acetate solvent-dispersed colloidal silica (SiO ₂ component 30% by mass, average particle size 20 nm, manufactured by Nissan Chemical Co., Ltd.), 2-methacryloyloxyethyl isocyanate (MOI, molecular weight 155, manufactured by Showa Denko Co., Ltd.) Was mixed for 19 hours, and 0.01 parts by weight of di-n-butyltin dilaurate (DBTDL) was added as a catalyst, followed by stirring at 70 ° C. for 2 hours. At this time, a very small amount of hydroquinone was added so that the polymerizable double bond would not react. Thereafter, all isocyanate groups were reacted, and it was confirmed by infrared absorption analysis that there were no remaining isocyanate groups, and a resin composition M having a solid content of 40% by mass was obtained.

  Next, 50 parts by mass of pentaerythritol tetraacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd., trade name A-TMMT) and 70 parts by mass of ethyl acetate as a solvent are added to 100 parts by mass of the resin composition M prepared above. Furthermore, as a leveling agent, 1 part by mass of solvent type leveling agent Byketol-Special (manufactured by Big Chemie Japan Co., Ltd.) and 5 parts by mass of IRGACURE 184 (manufactured by Ciba Japan Co., Ltd.) as an initiator are added, and a release layer is added. Coating solution 1 was prepared.

(Preparation of release layer coating liquids 2 to 4: Adjustment of release film smoothness Ry)
In the preparation of the release layer coating solution 1, the addition amount (1 part by mass) of the solvent type leveling agent Byketol-Special (manufactured by Big Chemie Japan Co., Ltd.) was changed to pentaerythritol tetraacrylate (manufactured by Shin Nakamura Chemical Co., Ltd.). , Trade names A-TMMT) were prepared in the same manner except that they were changed to 0 parts by weight, 2 parts by weight, and 4 parts by weight, respectively, with respect to 50 parts by weight.

(Preparation of release layer coating solutions 5 to 7: adjustment of pencil hardness of release film)
In the preparation of the release layer coating solution 3, the added amount (50 parts by mass) of pentaerythritol tetraacrylate (trade name A-TMMT, manufactured by Shin-Nakamura Chemical Co., Ltd.) is added to 100 parts by mass of the resin composition M. On the other hand, release layer coating solutions 5 to 7 were prepared in the same manner except that they were changed to 0, 15, and 30 parts by mass, respectively.

(Preparation of release layer coating liquids 8 to 10: adjustment of surface energy of release film)
In the preparation of the release layer coating solution 3, the amount of ethyl acetate solvent-dispersed colloidal silica (SiO ₂ component 30% by mass, average particle size 20 nm, manufactured by Nissan Chemical Industries, Ltd.) contained in the resin composition M (120 (Parts by mass) were changed to 0 parts by mass, 250 parts by mass, and 400 parts by mass, respectively, to prepare release layer coating solutions 8 to 10 in the same manner.

<Production of release film>
[Preparation of release film 1]
The above prepared release layer coating solution 1 is applied to the surface of the 100 μm-thick polyethylene terephthalate film (Cosmo Shine A4100, manufactured by Toyobo Co., Ltd.) that has not been subbing by the bar coating method, and is heated at 60 ° C. for 5 minutes. After heat drying, the release film 1 was produced by irradiating with ultraviolet rays at an irradiation intensity of 1500 mW / cm ² . In addition, it was 2.0 micrometers as a result of measuring the thickness of the formed release layer using the reflective spectral film thickness meter FE-3000 (made by Otsuka Electronics Co., Ltd.).

[Preparation of release films 2 to 10]
In the production of the release film 1, release films 2 to 10 were produced in the same manner except that the release layer coating liquids 2 to 10 were used instead of the release layer coating liquid 1, respectively.

[Production of Release Film 11]
Using the Ar / CF ₄ mixed gas (Ar = 99% by volume: CF ₄ = 1% by volume), the high-frequency power source frequency of 13.56 MHz (manufactured by Pearl Industrial Co., Ltd.), the discharge output for the release film 4 produced above. Under the condition of 4 W / cm ² , atmospheric pressure plasma discharge treatment was performed for 0.2 seconds to produce a release film 11.

[Preparation of Release Film 12]
In the production of the release film 11, a release film 12 was produced in the same manner except that the processing time of the atmospheric pressure plasma discharge treatment was changed to 1.0 second.

[Preparation of release films 13 and 14]
In the production of the release films 11 and 12, an Ar / N ₂ / CO ₂ mixed gas (Ar = 94% by volume) was used instead of the Ar / CF ₄ mixed gas (Ar = 99% by volume: CF ₄ = 1% by volume). : N ₂ = 3% by volume: CO ₂ = 3% by volume) was used to prepare release films 13 and 14 in the same manner.

[Production of release films 15 to 18]
In the production of the release films 11 to 14, release films 15 to 18 were produced in the same manner except that the release film 1 was used instead of the release film 4 as a sample to be subjected to plasma treatment.

[Preparation of release film 19]
The release film 4 produced above was subjected to a corona treatment of 20 W · min / m ² to produce a release film 19.

[Production of Release Film 20]
A release film 20 was produced by subjecting the produced release film 1 to a corona treatment of 20 W · min / m ² .

[Preparation of release films 21-27]
The following commercially available films were prepared and used as release films 21 to 27, respectively.

Release film 21: Cosmo Shine A4100 (manufactured by Toyobo Co., Ltd.)
Release film 22: Silicone ultralight release film E7006 having a release layer (thickness 100 μm, manufactured by Toyobo Co., Ltd.)
Release film 23: Non-silicone intermediate release film TN100 having a release layer (thickness 100 μm, manufactured by Toyobo Co., Ltd.)
Release film 24: Non-silicone heavy release film TN200 having a release layer (thickness 100 μm, manufactured by Toyobo Co., Ltd.)
Release film 25: Silicone light release film therapy WD having a release layer (thickness 100 μm, manufactured by Toray Industries, Inc.)
Release film 26: Non-silicone intermediate release film therapy BX9 having a delamination (thickness 100 μm, manufactured by Toray Industries, Inc.)
Release film 27: Non-silicone intermediate release film therapy BX10 having a release layer (thickness 100 μm, manufactured by Toray Industries, Inc.)
<< Preparation of release film with transparent conductive layer >>
Using the produced release films 1 to 27, the following silver nanowire dispersion liquid is used on the release surface, and the silver nanowire is applied under the condition that the basis weight of the silver nanowire is 60 mg / m ² to form a silver nanowire layer. Then, it was heated and dried at 120 ° C. for 30 minutes. Next, an aqueous solution containing polyvinyl alcohol (PVA) as a soluble binder is overcoated on the silver nanowire layer formed as described above so as to have a dry film thickness of 5 nm and dried, and release films 1-27 with a transparent conductive layer are formed. Produced.

[Preparation of silver nanowire dispersion]
Adv. Mater. , 2002, 14, 833 to 837, a silver nanowire having an average minor axis of 75 nm and an average length of 35 μm is prepared using polyvinylpyrrolidone K30 (molecular weight: 50,000; manufactured by ISP). Silver nanowires were separated by filtration using an outer filtration membrane, washed with water, redispersed in ethanol, and 25% by mass of hydroxypropylmethylcellulose as a water-soluble binder was added to silver to prepare a silver nanowire dispersion. .

[Measurement of characteristic value of release film]
About each produced release film, the surface energy (mN / m), pencil hardness, and smoothness Ry (nm) were measured according to the following method.

(Measurement of surface energy)
Using the contact angle surface analyzer VCA Optima-XE (AST Products) dynamic contact angle measurement mode, the surface energy (mN / m) of the release surface of each release film is measured using ultrapure water and diiodomethane as standard solutions. The contact angle was measured by dropping water droplets, and the surface energy in a two-component system was calculated.

(Measurement of pencil hardness)
The release surface of each release film was measured using a scratch hardness tester (manufactured by Cortec Co., Ltd.) according to a pencil hardness test method according to JIS K 5600.

(Measurement of smoothness Ry)
Ry of the release surface of each release film was measured using an atomic force microscope (AFM). Specifically, as an AFM, using a Seiko Instruments SPI3800N probe station and SPA400 multifunctional unit, a sample cut to a size of about 1 cm square is set on a horizontal sample stage on a piezo scanner, When the cantilever was approached to the sample surface and reached the region where the atomic force worked, scanning was performed in the XY direction, and the unevenness of the sample at that time was captured by the displacement of the piezo in the Z direction. A piezo scanner that can scan XY 20 μm and Z 2 μm was used. The cantilever is a silicon cantilever SI-DF20 manufactured by Seiko Instruments Inc., which has a resonance frequency of 120 to 150 kHz and a spring constant of 12 to 20 N / m. Measurement was performed at 1 Hz.

  The results obtained are shown in Table 1.

[Evaluation of release film with transparent conductive layer]
(Evaluation of coating uniformity)
Table 1 shows the results obtained by visually observing the uniformity of the coating film of the transparent conductive layer formed on the release surface of each release film, and evaluating the coating uniformity according to the following criteria.

○: The silver nanowire dispersion liquid is uniformly applied. ×: The silver nanowire dispersion liquid is applied in a non-uniform state by repelling the release film. << Preparation and Evaluation of Transparent Electrode >>
(Production of transparent electrode)
About the produced release films 1-27 with a transparent conductive layer, an ultraviolet curable transparent resin NN803 (manufactured by JSR Corporation) is applied on the transparent conductive layer under the condition that the film thickness after drying is 1.5 μm. After the solvent component was vaporized to form an adhesive layer, it was bonded to a glass substrate that was a transparent substrate. Then, the transparent conductive layer containing silver nanowire was transcribe | transferred to the transparent base material by irradiating an ultraviolet-ray, fully hardening | curing the contact bonding layer, and peeling a release film, and produced each transparent electrode.

[Evaluation of transparent electrode]
(Evaluation of peelability during transfer)
In the above transfer step, the peelability of the release film during transfer was visually observed, the peelability was evaluated according to the following criteria, and the obtained results are shown in Table 1.

A: The release film was peeled off satisfactorily and an extremely smooth transparent conductive layer was obtained. B: Cracks occurred in part of the release film. C: Part of the transparent conductive layer remained in the release film. D : Crack occurs in the release film, and a part of the release film adheres to the transparent conductive layer. E: The transparent conductive layer is non-uniform, and even if transferred, a portion without silver nanowires is generated and smooth. A transfer surface was not obtained. Aside from A, it was determined that there was a problem in quality.

(Evaluation of smoothness of transfer surface (transparent conductive layer))
The smoothness of the surface of the transparent conductive layer transferred onto the transparent substrate was visually observed, and the smoothness rY was measured using an atomic force microscope (AFM) in the same manner as in the above method. The smoothness of the transfer surface was evaluated according to the standard.

A: Smoothness of transfer surface has no problem in visual observation and smoothness Ry is less than 60 nm B: Smoothness of transfer surface has no problem in visual observation, but smoothness Ry is 60 nm or more C: Transfer surface The smoothness Ry is less than 60 nm, but there are some areas where the smoothness is inferior when visually observed. D: The smoothness of the transfer surface is clearly inferior by visual observation, and the smoothness Ry is also 60 nm or more. The obtained measurement results and evaluation results are shown in Table 1.

  As is clear from the results shown in Table 1, the transparent conductive layer formed using a release film having a release surface having the smoothness, surface energy, and pencil hardness specified in the present invention is compared with the comparative example. It can be seen that a highly uniform coating film can be obtained without repelling the silver nanowire dispersion used for the formation. Moreover, it turns out that the transparent electrode of this invention which has the transparent conductive layer based on this invention has the favorable peelability at the time of transcription | transfer, and the smoothness of the formed transparent conductive layer.

  Moreover, about each produced said transparent electrode, the surface specific resistance was measured by the four terminal method using the resistivity meter Loresta GP made from Dia Instruments, and the transmittance | permeability was set to Tokyo Denshoku. Total light transmittance was measured using an AUTOMATIC ZEMETER (MODEL TC-HIIIDP) manufactured by KK. As a result, the resistance value of the transparent electrode of the present invention was 10 to 20Ω / □, the transmittance was 80 to 90%, and it was confirmed that the transparent electrode had high conductivity and transparency. .

Example 2
<< Production of organic EL element >>
In accordance with the following method, organic EL elements 1 to 27 were produced using the transparent electrodes 1 to 27 produced in Example 1 as anode electrodes.

  For each transparent electrode produced in Example 1, Baytron PH510 (manufactured by HC Starck Co., Ltd.), which is a dispersion of PEDOT / PSS [poly (3,4-ethylenediothiophene) -poly (styrenesulfonate)] = 1: 2.5. ) Was applied with a spin coater at 1000 rpm for 3 minutes to form a conductive layer having a thickness of 100 nm, whereby the transparent electrode was converted into a surface electrode to form an anode electrode.

  Next, each of the vapor deposition crucibles in a commercially available vacuum vapor deposition apparatus was filled with the constituent material of each layer in an optimum amount for manufacturing each element. The evaporation crucible used was made of a resistance heating material made of molybdenum or tungsten.

First, after reducing the vacuum to 1 × 10 ⁻⁴ Pa, the deposition crucible containing α-NPD was energized and heated, and deposited on the anode electrode at a deposition rate of 0.1 nm / second. A hole transport layer was provided.

  Subsequently, each light emitting layer was provided in the following procedures.

  Ir-1, Ir-2 and compound 1-1 were co-deposited at a deposition rate of 0.1 nm / second so that the concentration of Ir-1 was 13% by mass and Ir-2 was 3.7% by mass. A green-red phosphorescent light emitting layer having a maximum wavelength of 622 nm and a thickness of 10 nm was formed.

  Next, E-1 and Compound 1-1 were co-evaporated at a deposition rate of 0.1 nm / second so that E-1 was 10% by mass, and a blue phosphorescent light emitting layer having a maximum emission wavelength of 471 nm and a thickness of 15 nm was formed. Formed.

  Thereafter, M-1 is vapor-deposited to a thickness of 5 nm to form a hole blocking layer, and CsF is co-deposited with M-1 so that the film thickness ratio is 10%, and an electron transport layer having a thickness of 45 nm is formed. Formed.

  Furthermore, aluminum 110nm was vapor-deposited and the cathode was formed.

Next, using a flexible sealing member made of polyethylene terephthalate as a base material and depositing Al ₂ O ₃ with a thickness of 300 nm, the cathode electrode except for the ends so that external lead terminals of the anode electrode and the cathode electrode can be formed. After applying an adhesive around the substrate and pasting a flexible sealing member, the adhesive was cured by heat treatment to produce organic EL elements 1 to 27.

<< Evaluation of organic EL elements >>
[Evaluation of uneven brightness]
Using the KEITHLEY source measure unit 2400 type, applying each of the organic EL elements produced as described above with direct current voltage, the organic EL elements 1 to 26 that emitted light at 1000 cd were observed for light emission uniformity with a 50 times microscope, The light emission luminance unevenness was evaluated according to the following criteria.

○: The entire organic EL element emits light uniformly. ×: Unevenness is observed in the light emission of the organic EL element. XX: Light emission as the organic EL element is not recognized.

-: The transparent conductive layer (silver nanowire-containing layer) could not be applied uniformly, and the organic EL device could not be formed. The results obtained above are shown in Table 2.

  As is clear from the results shown in Table 2 and the results shown in Table 1 of Example 1, the organic EL elements 22 to 27 using a commercially available release film are the surface energy, hardness, and smoothness of the release film. Since either of them was insufficient, light emission became uneven or did not emit light. In addition, the organic EL element 21 using a polyethylene terephthalate film having no release layer has insufficient hardness, cracks are generated in the release film, and spike-like protrusions are generated on the surface. occured. From the above, it can be seen that it is difficult to obtain a transparent electrode having a smooth surface by applying silver nanowires and transferring the film without cracks in a commercially available release film. Further, by comparing the organic EL elements 11 to 14, if the surface energy is in the range of 20 mN / m or more and 50 mN / m or less, the silver nanowire dispersion liquid can be applied uniformly, and the adhesive strength is too strong, and the silver nano Part of the wire does not remain on the release film. Moreover, by comparing the organic EL elements 5 to 10, when the hardness is H or less, a part of the release layer adheres to a part of the transparent conductive layer as a crack, and when the hardness is 6H or more, the release film It can be seen that cracks occur and a smooth transparent conductive layer cannot be obtained, resulting in uneven light emission. Further, when organic ELs 2 and 18 are compared, it is understood that uniform light emission is obtained when the smoothness Ry of the release film is 50 nm or less, but unevenness is obtained when the release film is 50 nm or more.

Claims (3)

  A transparent electrode manufacturing method for manufacturing a transparent electrode by forming a transparent conductive layer containing at least conductive metal fine particles on a release surface of a release film and then transferring the transparent conductive layer onto a transparent substrate. The release surface of the release film has a smoothness Ry of 1 nm or more and 50 nm or less, a surface energy of 20 mN / m or more and 50 mN / m or less, and according to a pencil hardness test method according to JISK5600. A method for producing a transparent electrode, wherein the measured pencil hardness is from H to 5H.   The method for producing a transparent electrode according to claim 1, wherein the conductive metal fine particles are metal nanowires.   A transparent electrode manufactured by the method for manufacturing a transparent electrode according to claim 1.