JP6413221B2 - Transparent conductive film - Google Patents

Description

  The present invention relates to a transparent conductive film using conductive silver fibers suitable for a touch panel.

  Currently, touch panels are widely used as devices capable of inputting information by directly touching an image display unit. A touch panel is an input device that transmits light on a display screen such as a liquid crystal display device. As a typical form, a capacitive type that utilizes the change in current capacity that occurs between a transparent electrode and a finger. There is a touch panel.

  As a transparent conductive film for touch panels, a transparent conductive film made of a metal oxide such as indium oxide containing tin oxide (tin-doped indium oxide, ITO) is generally laminated on a transparent base film. It is used. However, since a transparent conductive layer made of a metal oxide requires a high deposition temperature and / or a high annealing temperature in order to achieve high conductivity, the transparent substrate needs to have high heat resistance. was there.

In recent years, a transparent conductive film having a transparent conductive layer containing a silver fibrous conductive substance has been studied for this problem (see Patent Document 1). In Patent Document 1, a silver nanowire dispersion and a polyurethane resin are sequentially applied on a PET substrate and dried under a low temperature drying condition of 50 ° C. to provide a transparent conductive layer.

Special table 2009-505358

  However, a transparent conductive film using such a silver fibrous conductive material often has a yellow color derived from the reflection and absorption of silver fibers. Therefore, it is difficult to accurately express the color of the display device arranged under the touch panel, and there is a problem that the visibility of the touch panel is lowered.

  Accordingly, an object of the present invention is to provide a transparent conductive film using a silver fibrous conductive material that can suppress yellow coloring without reducing the total light transmittance.

  In the transparent conductive film of the present invention, a transparent conductive layer is laminated on one surface of a transparent substrate via an adhesive layer, the thickness of the adhesive layer is 5 to 30 nm, and the transparent conductive layer is It consists of conductive silver fibers and a transparent resin coating film, and has a film thickness of 50 to 200 nm.

  Preferably, a functional layer is laminated on the other surface of the transparent substrate.

  Preferably, the functional layer is a hard coat layer, and an adhesive layer having a film thickness of 5 to 30 nm is interposed between the transparent substrate and the hard coat layer. The difference in refractive index from the transparent substrate is within 0.02, and the film thickness is 0.8 to 3.0 μm.

  Further, a low refractive index layer having a refractive index lower than that of the hard coat layer is further laminated as a functional layer on the hard coat layer, and the low refractive index layer has a refractive index of 1.30-1. 45, and preferably a film thickness of 80 to 110 nm.

  In addition, the film thickness in this invention is a physical film thickness, and is not an optical film thickness. In the present invention, “OO to XX” indicating a numerical range means “XX or more and XX or less” unless otherwise specified.

  According to the present invention, an adhesive layer is provided on a transparent substrate, the adhesive layer has a thickness of 5 to 30 nm, and has a conductive conductive silver fiber, and a transparent conductive layer comprising a transparent resin coating for protecting the silver fiber. By setting the film thickness to 50 to 200 nm, it is possible to provide a transparent conductive film capable of suppressing coloring without decreasing the total light transmittance and suppressing the haze value.

Embodiments embodying the present invention will be described in detail below.
As for the transparent conductive film of this invention, the transparent conductive layer is laminated | stacked through the contact bonding layer on one surface of the transparent base film. Moreover, it is preferable that a functional layer is laminated on the other surface through an adhesive layer, and among them, a preferable functional layer is a hard coat layer and a low refractive index layer.

<Transparent substrate film>
The transparent substrate film is not particularly limited as long as it has transparency, but preferably has a refractive index in the range of 1.55 to 1.70. Examples of the material for forming such a transparent substrate film include polyesters such as polyethylene terephthalate (PET, refractive index: 1.67), polycarbonate (PC, refractive index: 1.59), polyarylate (PAR, refractive index). : 1.60) and polyether sulfone (PES, refractive index: 1.65). Among these, a polyester film, particularly a polyethylene terephthalate film is preferable because of easy molding.

  The thickness of the transparent substrate film is preferably 25 to 400 μm, more preferably 25 to 188 μm. When the thickness of the transparent substrate film is less than 25 μm or thicker than 400 μm, the handleability during the production and use of the transparent conductive film is unfavorable. In addition, various additives may contain in the transparent base film. Examples of such additives include ultraviolet absorbers, antistatic agents, stabilizers, plasticizers, lubricants, flame retardants, and the like.

<Adhesive layer>
An adhesive layer is a layer for improving the adhesiveness of a transparent base film, a transparent conductive layer, and a functional layer. The refractive index of the adhesive layer is preferably 1.40 to 1.80. The thickness of the adhesive layer is 5 to 30 nm, preferably 10 to 20 nm. As long as the adhesion between the transparent base film, the transparent conductive layer, and the functional layer can be improved, a known resin can be used as an adhesive. is there. When the film thickness of the adhesive layer is less than 5 nm, the adhesion between the transparent base film, the transparent conductive layer, and the functional layer cannot be maintained. On the other hand, when the film thickness of the adhesive layer exceeds 30 nm, it has an adverse optical effect on the transparent conductive layer, the yellow coloration becomes strong, and there is an optical adverse effect on the functional layer. The interference fringes will increase.

  As a method for forming the adhesive layer, a method in which a coating liquid containing a water-dispersible or water-soluble polyester resin as an adhesive is applied on the transparent substrate film and then dried is preferable. In particular, when a polyester film is used as the transparent substrate film, it is preferable to use a polyester resin, particularly a copolymerized polyester resin, as an adhesive for forming the adhesive layer. The copolyester resin means a polyester resin obtained by a polycondensation reaction between a plurality of dicarboxylic acids and a plurality of polyols or a transesterification reaction between a plurality of esters and a plurality of polyols. Such a copolyester resin is formed by a polycondensation reaction of a dicarboxylic acid and a polyol.

  Dicarboxylic acids include terephthalic acid, isophthalic acid, phthalic acid, phthalic anhydride, 2,6-naphthalenedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, adipic acid, sebacic acid, trimellitic acid, pyromellitic acid, dimer acid Etc. In addition to the dicarboxylic acid, a sulfonic acid metal base-containing dicarboxylic acid may be added to impart water dispersibility.

  Examples of polyols include ethylene glycol, propylene glycol, tetramethylene glycol, 1,4-cyclohexanedimethanol, neopentyl glycol, diethylene glycol, 1,4-butanediol, dipropylene glycol, 1,6-hexanediol, and xylene glycol. Although it is mentioned, it is not limited to these.

  A filler, wax, or the like may be added to the coating solution containing the copolymerized polyester resin for the purpose of imparting blocking resistance and slipperiness. Examples of the filler include silica, titanium oxide, calcium carbonate, calcium silicate, barium sulfate, calcium phosphate, aluminum oxide, magnesium oxide, zinc oxide, and tin oxide. Among these, it is preferable to select one that does not settle in the coating solution. These fillers usually have an average particle size of 20 to 60 nm. When the average particle size is less than 20 nm, sufficient blocking resistance and slipping properties may not be obtained, and when it exceeds 60 nm, the filler tends to fall off.

  As the wax, water-dispersible or water-soluble waxes such as carnauba wax, candelilla wax, rice wax, wood wax, palm wax, montan wax, ozokerite, ceresin wax, paraffin wax, polyethylene glycol, and polypropylene glycol are preferable.

  In order to further improve the scratch resistance, it is preferable to add a crosslinking agent to the adhesive layer. As the crosslinking agent, oxazolines, epoxy compounds, melamine compounds, isocyanate compounds, coupling agents and the like can be used, and among them, oxazolines are preferable. As the oxazolines, a polymer containing an oxazoline group is preferable. This is obtained by copolymerization with an addition polymerizable oxazoline group-containing monomer alone or with another monomer. Examples of the addition polymerizable oxazoline group-containing monomer include 2-vinyl-2-oxazoline, 2-vinyl-4-methyl-2-oxazoline, and 2-isopropenyl-2-oxazoline. Among these, 2-isopropenyl-2-oxazoline is preferred because it is easily available industrially.

  Other monomers are not limited as long as they are copolymerizable with addition-polymerizable oxazoline group-containing monomers, and are acrylic acid esters, unsaturated carboxylic acids, unsaturated nitriles, unsaturated amides. , Vinyl esters, vinyl ethers, α-olefins, halogen-containing α, β-unsaturated monomers, α, β-unsaturated aromatic monomers, and the like.

  The adhesive layer is formed by applying an adhesive coating solution on one side or both sides of the transparent substrate film. The application can be carried out at an arbitrary stage, but is preferably carried out during the production process of the transparent substrate film. The coating method is not particularly limited, and any known method such as a roll coating method, a spin coating method, a dip coating method, a spray coating method, a bar coating method, a knife coating method, a die coating method, an ink jet method, or a gravure coating method is adopted. it can.

<Transparent conductive layer>
A transparent conductive layer is comprised from the silver resin which has electroconductivity, and the transparent resin coating film which protects silver fiber.

(Silver fiber)
The shape of the silver fiber is not branched, it is easy to loosen, and it is easy to obtain a uniform distribution density of the fibrous material. As a result, a large opening is formed between the fibers and the fiber bundle, realizing good light transmittance The wire-like thing which can do is preferable. As an example of the conductive material having such a shape, a silver nanowire which is a wire-like conductive metal can be given. In the present invention, the silver nanowire is a fine conductive substance having a nanometer size and having a shape of a thin bar having a straight line or a curved line and made of silver. When they are nanowires, they are entangled with each other to form a network, so even with a small amount of conductive material, a good electrical conduction path can be formed, and the resistance value of the transparent conductive layer can be reduced. This can be further reduced. Furthermore, when such a mesh-like shape is formed, since the opening of the gap portion of the mesh is large, even if the fibrous conductive material itself is not transparent, it achieves good transparency as a coating film. Is possible.

  The fiber diameter of the silver fiber is preferably less than 500 nm, more preferably less than 200 nm, and even more preferably less than 100 nm. The aspect ratio is preferably more than 10. As an aspect ratio, it is more preferable to exceed 50, and it is more preferable to have an aspect ratio exceeding 100. The shape and size of the silver fiber can be confirmed with a scanning electron microscope or a transmission electron microscope.

  Silver nanowires can be prepared by methods known in the art. For example, a method of reducing silver nitrate in a solution, a method in which an applied voltage or current is applied to the precursor surface from the tip of the probe, a silver nanowire is drawn at the probe tip, and the silver nanowire is continuously formed (Japanese Patent Laid-Open No. 2004-223893). As a method for reducing silver nitrate in a solution, more specifically, silver fibers can be synthesized by liquid phase reduction of a silver salt such as silver nitrate in the presence of a polyol such as ethylene glycol and polyvinylpyrrolidone. is there. For example, Xia, Y. et al. etal. , Chem. Mater. (2002), 14, 4736-4745 and Xia, Y. et al. etal. , Nano letters (2003) 3 (7), 955-960, but is not particularly limited to the methods described therein.

  Silver fibers can be used in a continuous coating method or the like by appropriately dispersing in a dispersion medium to form a paint. The liquid that is the dispersion medium is not particularly limited, and various known dispersion media can be used. For example, saturated hydrocarbons such as hexane, aromatic hydrocarbons such as toluene and xylene, alcohols such as methanol, ethanol, propanol, and butanol, ketones such as acetone, methyl ethyl ketone (MEK), methyl isobutyl ketone, and diisobutyl ketone , Esters such as ethyl acetate and butyl acetate, ethers such as tetrahydrofuran, dioxane and diethyl ether, amides such as N, N-dimethylformamide, N-methylpyrrolidone (NMP) and N, N-dimethylacetamide, ethylene chloride And halogenated hydrocarbons such as chlorobenzene. Moreover, a dispersing agent can also be used according to the kind of dispersion medium. Among these, polar dispersion media are preferable, and those having an affinity for water such as alcohols such as methanol and ethanol, and amides such as NMP have good dispersibility without using a dispersant. It is preferable. These liquids can be used singly or as a mixture of two or more.

  Water can also be used as a dispersion medium. When water is used, if the surface of the adhesive layer is hydrophobic, water is easily repelled, and a uniform film is difficult to obtain when applied. In such a case, a uniform film can be obtained by mixing and adding alcohol to water, or selecting and adding a surfactant that improves wettability to the surface of the hydrophobic adhesive layer. The amount of liquid as a dispersion medium to be used is not particularly limited, and the silver fiber dispersion may have a viscosity suitable for coating. For example, the liquid can be set in a wide range of about 100 to 100,000 parts by weight with respect to 100 parts by weight of the silver fiber, and appropriately selected according to the type of the silver fiber and the dispersion medium, the stirring used, and the dispersing device Can do.

  The dispersion of the silver fibers in the dispersion medium can be performed by applying a known dispersion method to the mixture of the silver fibers and the liquid that is the dispersion medium as necessary. The silver fiber dispersion preferably does not contain a binder resin in terms of improving the conductive performance. In the transparent conductive layer, the contact of silver fibers is not inhibited unless a binder resin is used. Therefore, the electrical conductivity between silver fibers is ensured, and the electrical resistance value of the obtained transparent conductive layer can be further reduced. In addition, the fixation of the transparent conductive layer on the transparent substrate film by the following transparent resin coating film is performed by impregnating the transparent conductive film coating material into the transparent conductive layer and reaching the support film, The fact that the silver fiber dispersion does not contain a binder resin means that the transparent conductive layer contains more gaps, which is preferable in that the fixation by impregnation with the transparent resin coating film is not hindered.

  However, as long as the amount of the transparent conductive layer on the transparent substrate film does not decrease the conductivity and peelability, and does not impair the step of fixing the transparent conductive layer with the resin in the coating for transparent resin coating film, Resin can also be included, and the type and amount thereof can be appropriately selected within the range in which the above characteristics are obtained. In the above addition amount range, the silver fiber dispersion may contain resin and other additives in order to adjust viscosity, prevent corrosion, improve adhesion to the transparent resin coating, and control silver fiber dispersion. Good. Examples of suitable additives and binders include carboxymethylcellulose (CMC), 2-hydroxyethylcellulose (HEC), hydroxypropylmethylcellulose (HPMC), methylcellulose (MC), polyvinyl alcohol (PVA), tripropylene glycol (TPG), And xanthan gum (XG), and surfactants such as ethoxylates, alkoxylates, ethylene oxide, and propylene oxide, and copolymers thereof, sulfonates, sulfates, disulfonates, sulfosuccinates, phosphate esters , And fluorosurfactants, but are not limited thereto.

Furthermore, 2-alkoxyethanol, β-diketone, alkyl acetate, and the like can also be used as non-polymeric organic compounds as film forming agents.

(Transparent resin coating)
The transparent resin coating film is provided to fix the silver fibers on the film. The transparent resin coating film is preferably formed from a material containing an active energy ray-curable resin and a photopolymerization initiator.

  Examples of the active energy ray-curable resin include monofunctional (meth) acrylate and polyfunctional (meth) acrylate. As the monofunctional (meth) acrylate, (meth) acrylic acid alkyl ester, (meth) acrylic acid (poly) ethylene glycol group-containing (meth) acrylic acid ester and the like are preferable. The polyfunctional (meth) acrylate is preferably an ester compound of polyhydric alcohol and (meth) acrylic acid, a polyfunctional polymerizable compound containing two or more (meth) acryloyl groups such as urethane-modified acrylate. In the present specification, “(meth) acrylate” refers to acrylate and methacrylate. Similarly, “(meth) acrylic monomer” described later refers to an acrylic monomer and a methacrylic monomer, and “(meth) acryloyl group” refers to an acryloyl group and a methacryloyl group.

  The photopolymerization initiator is used as a polymerization initiator for forming a coating film by curing the coating liquid for transparent resin coating film with an active energy ray such as ultraviolet (UV). The photopolymerization initiator is not particularly limited as long as it initiates polymerization upon irradiation with active energy rays, and known compounds can be used. For example, 1-hydroxycyclohexyl phenyl ketone, 2-hydroxy-2-methyl-1-phenylpropan-1-one, 2-methyl-1- [4- (methylthio) phenyl] -2-morpholinopropane-1 -One, acetophenone polymerization initiators such as 1- [4- (2-hydroxyethoxy) phenyl] -2-hydroxy-2-methyl-1-propan-1-one, benzoin, 2,2-dimethoxy 1,2 -Benzoin polymerization initiators such as diphenylethane-1-one, benzophenone, [4- (methylphenylthio) phenyl] phenylmethanone, 4-hydroxybenzophenone, 4-phenylbenzophenone, 3,3 ', 4,4' -Benzophenone polymerization initiators such as tetra (t-butylperoxycarbonyl) benzophenone, 2-chlorothio Xanthone, such thioxanthone type polymerization initiators such as 2,4-diethyl thioxanthone, and the like. One of these photopolymerization initiators may be used alone, or two or more thereof may be mixed.

  It is preferable that 0.1-10 mass parts of photoinitiators are contained in a transparent resin coating film. When the content of the photopolymerization initiator is less than 0.1 part by mass, the active energy ray-curable resin is not sufficiently cured. On the other hand, when the content of the photopolymerization initiator exceeds 10 parts by mass, the photopolymerization initiator is unnecessarily increased, which is not preferable.

  The solvent of the coating liquid for transparent resin coating is not particularly limited as long as it is a known one that has been conventionally used for coating liquid for forming each layer in this type of transparent conductive film, etc. For example, alcohol-based, ketone-based An ester solvent can be selected as appropriate.

  When forming a transparent conductive layer while impregnating silver fibers with a coating solution for a transparent resin coating film, the film thickness of the transparent conductive layer can be appropriately adjusted depending on the application, but the conductivity tends to decrease as the thickness decreases. On the other hand, if it is too thick, transparency tends to decrease due to an increase in haze value, a decrease in total light transmittance, and the like. For example, when used as a transparent conductive layer for a touch panel, since a low haze value and high transparency are strongly required, a transparent conductive layer having a thinner film thickness is often formed. In this case, the transparent conductive layer has a large number of openings, but when measured with a contact-type film thickness meter, the average film thickness is preferably 10 nm to 500 nm, more preferably 30 nm to 300 nm, and 50 nm to 200 nm. Most preferred.

  In addition, if the film thickness of the transparent resin coating is too thin for silver fibers, the protective layer functions such as scratch resistance, abrasion resistance, and weather resistance will decrease, and if it is too thick, the contact resistance as a conductor will increase. To do. The film thickness of the transparent resin coating film is preferably 30 to 200 nm after coating and drying when the film thickness of the transparent conductive layer is 50 to 200 nm. In consideration of the film thickness, the surface resistivity, haze, and the like can be adjusted to achieve predetermined values. 40 to 200 nm is more preferable, and 50 to 200 nm is most preferable. The film thickness of the transparent resin coating film depends on the film thickness of the transparent conductive layer, but if the film thickness is 30 nm or more, the silver nanowire is not exposed too much on the surface of the protective layer, and the protective function by the transparent resin coating film is more When the film thickness is 200 nm or less, an excessively thick film is not formed on the surface, and better conductive performance tends to be ensured.

<Formation of transparent conductive layer>
The transparent conductive layer is formed by applying a silver fiber dispersion on a transparent base film on which an adhesive layer has been formed and then drying to form a conductive silver fiber layer. It is formed by applying and drying the liquid and then curing by irradiation with active energy rays. The method for applying the silver fiber dispersion and the transparent resin coating solution is not particularly limited. For example, a roll coating method, a spin coating method, a dip coating method, a spray coating method, a bar coating method, a knife coating method, a die coating method, and an inkjet method. Any known method such as a gravure coating method can be employed. The type of active energy ray is not particularly limited, but it is preferable to use ultraviolet rays from the viewpoint of convenience and the like.

<Functional layer>
A functional layer can be provided on the opposite surface of the transparent substrate film via an adhesive layer. As this functional layer, any functional layer that can impart a predetermined function to the transparent conductive film can be applied. Examples of the functional layer include a hard coat layer, a low refractive index layer, an antireflection layer, an ultraviolet absorption layer, an antistatic layer, and an antiblocking layer. The antireflection layer is formed by laminating a low refractive index layer having a refractive index lower than that of the hard coat layer on the hard coat layer.

<Hard coat layer>
The hard coat layer is a layer that improves the hardness and scratch resistance of the transparent conductive film surface by being provided. As long as the difference in refractive index between the refractive index of the hard coat layer and the refractive index of the transparent substrate film is within 0.02, and the surface hardness and scratch resistance can be improved, the hard coat layer is used in this type of film. All known resins used in the above can be used, and it is particularly preferable that the resin is formed from a material containing an active energy ray-curable resin and metal oxide fine particles. Here, the metal oxide fine particles mean metal oxides having an average particle diameter of preferably 150 nm or less, more preferably 10 to 150 nm. When this average particle diameter exceeds 150 nm, the fine particles become too large, resulting in a loss of transparency of the hard coat layer.

  By reducing the reflected light by making the refractive index of the hard coat layer close to the refractive index of the transparent substrate film, interference fringes generated by interference of the reflected light can be reduced. On the other hand, when the difference in refractive index between the transparent base film and the hard coat layer exceeds 0.02, the reflected light at the interface between the transparent base film and the hard coat layer becomes strong, resulting in strong interference fringes. It is inappropriate.

  As the active energy ray-curable resin used for the hard coat layer, the same type as the active energy ray-curable resin used in the transparent resin coating can be used.

  When the metal oxide fine particles added to the active energy ray-curable resin are dispersed in the active energy ray-curable resin and a coating film is formed, the difference in refractive index between the transparent base film and the hard coat layer is zero. Those that can be adjusted to be 0.02 or less are selected. Examples of the metal oxide include ITO (indium-tin composite oxide, refractive index 2.0), ATO (antimony-tin composite oxide, refractive index 2.1), antimony oxide (refractive index 2.1), and oxidation. At least one selected from the group consisting of zinc (refractive index 2.1), zirconium oxide (refractive index 2.1), and titanium oxide (refractive index 2.4) is preferable. Among these, zirconium oxide and antimony oxide are particularly preferable in terms of particle dispersibility, average particle diameter, availability, and production cost. The addition amount of the metal oxide fine particles to the active energy ray-curable resin is about 1 to 500 parts by mass with respect to 100 parts by mass of the active energy ray-curable resin.

  Furthermore, the hard coat layer coating solution also contains a photopolymerization initiator. The photopolymerization initiator may be the same as the photopolymerization initiator used in the transparent resin coating film. 0.1-10 mass parts is contained in a hard-coat layer with respect to a total of 100 mass parts of active energy ray hardening-type resin and metal oxide fine particles. When the content of the photopolymerization initiator is less than 0.1 part by mass, the active energy ray-curable resin is not sufficiently cured. On the other hand, when the content of the photopolymerization initiator exceeds 10 parts by mass, the photopolymerization initiator is unnecessarily increased, which is not preferable.

  In addition, other components can be further added to the active energy ray-curable resin as long as the effects of the present invention are not impaired. Examples of such other components include additives such as a polymer, a polymerization inhibitor, an antioxidant, a dispersant, a surfactant, a light stabilizer, and a leveling agent. Further, any amount of solvent can be added as long as it is dried after film formation in the wet coating method.

  Moreover, the film thickness after dry-hardening of a hard-coat layer shall be 0.8-3.5 micrometers. When the film thickness is less than 0.8 μm, the pencil hardness is less than H, which is not preferable. When the film thickness is thicker than 3.5 μm, curling due to curing shrinkage becomes strong and becomes unnecessarily thick, which is not preferable because productivity and workability are lowered.

  The hard coat layer is formed by forming an adhesive layer on the surface opposite to the transparent conductive layer on the transparent substrate film, applying a hard coat layer coating solution, drying, and curing by irradiation with active energy rays. . The coating method of the hard coat layer coating solution is not particularly limited, and examples thereof include a roll coating method, a spin coating method, a dip coating method, a spray coating method, a bar coating method, a knife coating method, a die coating method, an ink jet method, and a gravure coating method. Any known method can be employed. The type of active energy ray is not particularly limited, but it is preferable to use ultraviolet rays from the viewpoint of convenience and the like.

<Low refractive index layer>
A low refractive index layer is a layer which improves a total light transmittance by reducing reflection by relative relationship with base layers, such as a hard-coat layer or a transparent base film. The low refractive index layer has a refractive index in the range of 1.30 to 1.45, which is lower than that of the base layer such as a hard coat layer or a transparent base film, and maintains adhesion and scratch resistance with the base layer. As long as it is possible, all known resins can be used, and it is particularly preferable that the resin is formed from a material containing inorganic fine particles and an active energy ray-curable resin.

  When the refractive index of the low refractive index layer is less than 1.30, the proportion of inorganic fine particles in the coating film increases, and the coating film strength decreases. On the other hand, when the refractive index of the low refractive index layer is larger than 1.45, the reflection reduction function is lowered, and the degree of increase in the total light transmittance becomes low.

  The active energy ray curable resin may be the same type as the active energy ray curable resin used in the transparent resin coating film. Here, from the viewpoint of adjusting the refractive index to be low, an active energy ray-curable resin containing a fluorine group can also be used. The active energy ray-curable resin containing a fluorine group is not particularly limited, and a monofunctional (meth) acrylate, a polyfunctional (meth) acrylate moiety and a fully fluorinated alkyl, alkenyl, aryl ester, complete or partial fluorine And fluorinated vinyl ethers, fully or partially fluorinated vinyl esters, and fully or partially fluorinated vinyl ketones.

  In addition, the inorganic fine particles are blended in order to actively lower the refractive index, and the average particle diameter is preferably 80 nm or less, more preferably 10 to 80 nm. When the average particle diameter is larger than 80 nm, it is not preferable because the optical performance of the low refractive index layer is deteriorated such as light scattering. Furthermore, the surface of the fine particles can be modified with various coupling agents as required. An example of such a coupling agent is an organically substituted silicon compound. In particular, a film having high hardness can be formed by modifying the surface with a reactive group such as a (meth) acryloyl group.

  The inorganic fine particles added to the active energy ray-curable resin are preferably at least one selected from the group consisting of hollow silicon oxide, colloidal silicon oxide, lanthanum fluoride, and magnesium fluoride. Among these, hollow silicon oxide and colloidal silicon oxide are particularly preferable in terms of average particle diameter, availability, and production cost.

  The addition amount of the inorganic fine particles to the active energy ray curable resin is about 1 to 1000 parts by mass with respect to 100 parts by mass of the active energy ray curable resin.

Further, the coating liquid for the low refractive index layer also contains a photopolymerization initiator. The photopolymerization initiator may be the same as the photopolymerization initiator used in the transparent resin coating film. The photopolymerization initiator is contained in an amount of 0.1 to 10 parts by mass in the low refractive index layer with respect to 100 parts by mass in total of the active energy ray-curable resin and the metal oxide fine particles. When the content of the photopolymerization initiator is less than 0.1 part by mass, the active energy ray-curable resin is not sufficiently cured. On the other hand, when the content of the photopolymerization initiator exceeds 10 parts by mass, the photopolymerization initiator is unnecessarily increased, which is not preferable.

In addition, other components can be further added to the active energy ray-curable resin as long as the effects of the present invention are not impaired. Examples of such other components include additives such as a polymer, a polymerization inhibitor, an antioxidant, a dispersant, a surfactant, a light stabilizer, and a leveling agent. Further, any amount of solvent can be added as long as it is dried after film formation in the wet coating method.

The thickness of the low refractive index layer after drying and curing is 80 to 110 nm. When the film thickness is less than 80 nm, the reflection reduction function is lowered, and the degree of increase in the total light transmittance is lowered, which is not preferable. When the film thickness is greater than 110 nm, the coloring becomes strong due to interference with the hard coat layer, which is not preferable.

After forming the adhesive layer on the surface opposite to the transparent conductive layer on the transparent substrate film or forming the hard coat layer on the adhesive layer, the low refractive index layer is coated with the coating solution for the low refractive index layer. After coating and drying, it is formed by curing by irradiation with active energy rays. The coating method of the coating solution for the low refractive index layer is not particularly limited. For example, roll coating method, spin coating method, dip coating method, spray coating method, bar coating method, knife coating method, die coating method, ink jet method, gravure coating method. Any known method can be used. The type of active energy ray is not particularly limited, but it is preferable to use ultraviolet rays from the viewpoint of convenience and the like.

  The color of transmitted light of such a transparent conductive film can be evaluated by b * of the L * a * b * color system defined in JISZ 8729, and −1.0 ≦ b * ≦ 1.0. When b *> 1.0, there is a problem that the transparent conductive film appears colored yellow. On the other hand, when b * <− 1.0, there is a problem that the transparent conductive film appears to be colored blue.

  At the same time, the total light transmittance of the transparent conductive film is 90.0% or more. A total light transmittance of less than 90.0% is not preferable because the luminance deteriorates when used for a member such as a touch panel. The haze value of the transparent conductive film is less than 2.0%. When the haze value is 2.0% or more, the transparency is lowered, and the visibility of the display image is deteriorated when used for a member such as a touch panel.

EXAMPLES Hereinafter, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the scope of these examples.
First, an adhesive coating solution, a transparent resin coating solution, a hard coating layer coating solution, and a low refractive index layer coating solution are prepared and formed using a hard coating layer coating solution and a low refractive index layer coating solution. The refractive index of the layer to be measured was measured by the following method.

<Refractive index>
(1) The coating liquid for each layer is dried and cured on a PET film having a refractive index of 1.67 (trade name “A4100”, manufactured by Toyobo Co., Ltd.) using a dip coater (produced by Motori Sugiyama). The thickness of the layer was adjusted so as to be about 100 to 1000 nm.
(2) After drying, it was cured by irradiating with 400 mJ ultraviolet rays using a 120 W high-pressure mercury lamp in a nitrogen atmosphere by an ultraviolet irradiation device (manufactured by Iwasaki Electric Co., Ltd.). The back surface of the cured PET film was roughened with sandpaper, and the reflection spectrum was measured with a reflection spectral film thickness meter (“FE-3000”, manufactured by Otsuka Electronics Co., Ltd.).
(3) From the reflectance read from the reflection spectrum, the constant of the wavelength dispersion formula (Formula 1) of n-Cauchy shown below was obtained, and the refractive index at the wavelength of 589 nm was obtained.
N (λ) = a / λ4 + b / λ2 + c (Formula 1)
(N: refractive index, λ: wavelength, a, b, c: chromatic dispersion constant)

(Preparation of adhesive coating solution)
(1) Synthesis of copolyester resin (a)
100 parts by mass of dimethyl terephthalate, 100 parts by mass of dimethyl isophthalate, 30.3 parts by mass of ethylene glycol, 150 parts by mass of neopentyl glycol, 0.1 part by mass of zinc acetate and 0.1 part by mass of antimony trioxide are used in a transesterification reaction vessel. Then, the mixture was heated to 180 ° C. and reacted for 4 hours to conduct a transesterification reaction. Thereafter, 5 parts by mass of 5-sodium sulfoisophthalic acid was added, and an esterification reaction was performed at 240 ° C. for 1 hour. Next, the temperature was raised to 250 ° C., the inside of the system was reduced in pressure to 1 mmHg (133 Pa), and a polycondensation reaction was performed for 2 hours to obtain a copolyester resin (a).

(2) Synthesis of cross-linking agent (b) Charge 300 parts by mass of ion-exchanged water into a flask and heat to 60 ° C. under a nitrogen stream, and add 0.3 part by mass of ammonium persulfate and 0.3 part by mass of sodium hydrogen nitrite. Added. Thereafter, a mixture of 20.2 parts by mass of methyl methacrylate, 21.2 parts by mass of 2-isopropenyl-2-oxazoline, 45.5 parts by mass of polyethylene oxide methacrylic acid and 10.2 parts by mass of acrylamide was added dropwise over 4 hours. Stirring was continued for 1 hour after completion of the dropwise addition to obtain a 25% by mass aqueous dispersion of the crosslinking agent (B).

(3) Preparation of Adhesive Coating Solution A-1 65 parts by mass of a 30% by mass aqueous dispersion of the copolyester resin (a), 40 parts by mass of a 25% by mass aqueous dispersion of the crosslinking agent (b) and 450 parts by mass of ion-exchanged water was mixed to obtain an adhesive coating solution A-1.

(Preparation of transparent resin coating solution)
Transparent by mixing 100 parts by mass of active energy ray-curable resin (DPHA manufactured by Nippon Kayaku Co., Ltd.), 5 parts by mass of photopolymerization initiator (IRGACURE 184 manufactured by Ciba Specialty Chemicals Co., Ltd.) and 2625 parts by mass of isobutyl alcohol. Resin coating liquid (B-1) was prepared.

[Preparation of coating liquid for hard coat layer]
The following raw materials were used as the coating liquid for the hard coat layer, and each raw material had the composition described in Table 1 below, and the fine particle component (silica fine particles or metal oxide fine particles) and the active energy ray-curable resin were started. The agent and the solvent were mixed at a mass ratio of 100: 5: 100 to prepare hard coat layer coating liquids HC-1 to HC-2. As each raw material, a zirconium oxide fine particle dispersion (ZRMEK 25% -F47 manufactured by CI Kasei Co., Ltd.) was used as metal oxide fine particles. A hexafunctional urethane acrylate (purple light UV-7600B manufactured by Nippon Synthetic Chemical Industry Co., Ltd.) was used as the active energy ray-curable resin. IRGACURE184 (I-184) manufactured by Ciba Specialty Chemicals Co., Ltd. was used as a photopolymerization initiator. Further, methyl isobutyl ketone was used as a solvent.

The refractive index of the hard coat layer formed using the obtained coating liquids HC-1 to HC-2 for hard coat layer was measured. The results are shown in Table 1.

(Preparation of coating solution for low refractive index layer)
The following raw materials are used as the coating solution for the low refractive index layer, and each raw material has the composition described in Table 2 below, and the fine particle component (hollow silica fine particles or metal oxide fine particles) component and the active energy ray-curable resin The photopolymerization initiator and the solvent were mixed at a mass ratio of 100: 5: 2000 to prepare coating solutions L-1 to L-3 for the low refractive index layer. As each raw material, acrylic modified hollow silica fine particle through rear NAU manufactured by JGC Catalysts & Chemicals Co., Ltd. was used as hollow silica fine particles. Moreover, active energy ray-curable resin: Nippon Kayaku Co., Ltd. DPHA was used. IRGACURE907 (I-907) manufactured by Ciba Specialty Chemicals Co., Ltd. was used as a photopolymerization initiator. And isopropyl alcohol was used as a solvent.

The refractive index of the low refractive index layer formed using the obtained coating liquids L-1 to L-3 for the low refractive index layer was measured. The results are shown in Table 2.

( Reference Example 1-1)
An adhesive coating solution (A-1) was applied to one surface of a 125 μm thick PET film with a bar coater, followed by drying by heating to form an adhesive layer.

  On the adhesive layer, 0.1% w / v silver silver electrode fiber aqueous dispersion medium (Clear Ohmink manufactured by Cambridge Technology Corporation) is applied with a bar coater and dried by heating to form a conductive silver fiber layer. did. Further thereon, a transparent resin coating liquid (B-1) was applied with a bar coater, dried, and then cured by irradiating with a 120 W high-pressure mercury lamp by irradiating 400 mJ ultraviolet rays (each layer). (See Table 3 below). About the obtained transparent conductive film, the total light transmittance, the haze value, the transmitted color b *, and the adhesiveness were measured by the following methods (see Table 3 below for measurement results).

<Total light transmittance / haze value>
The total light transmittance (%) and haze value of the transparent conductive film were measured with a haze meter (“NDH2000”, manufactured by Nippon Denshoku Industries Co., Ltd.).

<Transparent color>
Using a color difference meter (“SQ-2000”, manufactured by Nippon Denshoku Industries Co., Ltd.), the transmitted color and b * of the transparent conductive film were measured. This b * is a value in the L * a * b * color system defined in JISZ 8729.

<Adhesion>
The transparent conductive layer was subjected to a cross-cut peeling tape test according to JIS D0202-1998. Using cellophane tape (manufactured by Nichiban Co., Ltd., CT24), the film was adhered to the film and then peeled off. Judgment was expressed as “C” when 100 cells were not peeled out of 100 squares, and “×” when one cell was peeled off.

( Reference Example 1-2 to Reference Example 1-3)
A transparent conductive film was produced in the same manner as in Reference Example 1-1 except that the adhesive layer and the transparent conductive layer were formed as shown in Table 3 below. About the transparent conductive film of the obtained Reference Example 1-2 to Reference Example 1-3, the total light transmittance, the haze value, the transmission color b *, and the adhesion were measured in the same manner as in Reference Example 1-1 (measurement results). (See Table 3 below).

(Comparative Example 1-1 to Comparative Example 1-3)
A transparent conductive film was produced in the same manner as in Reference Example 1-1 except that the thickness of the adhesive layer and the transparent conductive layer were set as shown in Table 4 below.

(Comparative Example 1-4)
A transparent conductive film was produced in the same manner as Reference Example 1-1 except that no adhesive layer was formed.

About the transparent conductive film of the obtained Comparative Reference Example 1-1 to Comparative Reference Example 1-4, the total light transmittance, the haze value, the transmission color b *, and the adhesion were measured in the same manner as in Reference Example 1-1. See Table 4 below for measurement results).

( Reference Example 2-1)
An adhesive coating liquid (A-1) was applied to both surfaces of a 125 μm-thick PET film with a bar coater and heat-dried to form an adhesive layer.

  The hard coat layer coating solution (HC-1) was applied to one surface of the adhesive layer with a bar coater, and hardened by irradiating with 400 mJ ultraviolet rays with a 120 W high pressure mercury lamp. . Subsequently, a 0.1% w / v silver / silver electrode fiber aqueous dispersion medium (Clear Ohm ink manufactured by Cambridge Technology Corporation) was applied on the adhesive layer on the other surface of the PET film with a bar coater, dried by heating, and conductive. A silver fiber layer having was formed. Further thereon, a transparent resin coating liquid (B-1) was applied with a bar coater, dried, and then cured by irradiating with a 120 W high-pressure mercury lamp by irradiating 400 mJ ultraviolet rays (each layer). For the film thickness, see Table 5 below).

( Reference Example 2-2)
A transparent conductive film was produced in the same manner as in Reference Example 2-1, except that the thickness of the adhesive layer and the transparent conductive layer were set as shown in Table 5 below. For the obtained transparent conductive film of Reference Example 2-2, the total light transmittance, haze value, transmission color b *, and adhesion were measured in the same manner as in Reference Example 2-1. ).

(Example 3-1)
An adhesive coating liquid (A-1) was applied to both surfaces of a 125 μm-thick PET film with a bar coater and heat-dried to form an adhesive layer.

  The hard coat layer coating solution (HC-1) was applied to one surface of the adhesive layer with a bar coater, and hardened by irradiating with 400 mJ ultraviolet rays with a 120 W high pressure mercury lamp. . Further, the low refractive index layer coating liquid (L-1) was applied onto the hard coat layer with a bar coater, and cured by irradiating with 400 mJ ultraviolet rays with a 120 W high pressure mercury lamp. . Subsequently, a 0.1% w / v silver / silver electrode fiber aqueous dispersion medium (Clear Ohm ink manufactured by Cambridge Technology Corporation) was applied on the adhesive layer on the other surface of the PET film with a bar coater, dried by heating, and conductive. A silver fiber layer having was formed. Further thereon, a transparent resin coating liquid (B-1) was applied with a bar coater, dried, and then cured by irradiating with a 120 W high-pressure mercury lamp by irradiating 400 mJ ultraviolet rays (each layer). (See Table 6 below).

(Examples 3-2 to 3-3)
A transparent conductive film was produced in the same manner as in Example 3-1, except that the thickness of the adhesive layer and the transparent conductive layer were set as shown in Table 6 below. For the obtained transparent conductive films of Examples 3-2 and 3-3, the total light transmittance, haze value, transmitted color b *, and adhesion were measured in the same manner as in Example 3-1. (See Table 6).

(Example 4-1)
An adhesive coating liquid (A-1) was applied to both surfaces of a 125 μm-thick PET film with a bar coater and heat-dried to form an adhesive layer. The low refractive index layer was formed by applying the low refractive index layer coating liquid (L-1) to one of the adhesive layers with a bar coater and irradiating it with ultraviolet light of 400 mJ with a 120 W high pressure mercury lamp. Subsequently, a 0.1% w / v silver / silver polar fiber aqueous dispersion medium (Clear Ohmink manufactured by Cambrius Technology Corporation) is applied on the other adhesive layer with a bar coater, heat-dried, and conductive silver fibers. A layer was formed. Further thereon, a transparent resin coating liquid (B-1) was applied with a bar coater, dried, and then cured by irradiating with a 120 W high-pressure mercury lamp by irradiating 400 mJ ultraviolet rays (each layer). For the film thickness, see Table 7 below).

(Examples 4-2 to 4-3)
A transparent conductive film was produced in the same manner as in Example 4-1, except that the thickness of the adhesive layer and the transparent conductive layer were set as shown in Table 7 below. For the obtained transparent conductive films of Examples 4-2 and 4-3, the total light transmittance, haze value, transmitted color b *, and adhesion were measured in the same manner as in Example 4-1. (See Table 7).

(Results and Discussion)
As is clear from the results of Reference Example 1-1 to Reference Example 1-3 (Table 3), the transparent conductive layer is made of a silver fiber having conductivity and a transparent resin coating film, with the adhesive layer having a thickness of 5 to 30 nm. When the film thickness was 50 to 200 nm, the value of the transmitted color b * was small, coloring of the transparent conductive film was sufficiently suppressed, and an excellent total light transmittance could be realized.

On the other hand, in Comparative Reference Examples 1-1 to 1-3 (Table 4), either the film thickness of the adhesive layer or the film thickness of the transparent conductive layer is out of the above range, and the value of the transmission color b * is The transparent conductive film was greatly colored, the total light transmittance was lowered, or the haze value was increased.

In Comparative Reference Example 1-4 (Table 4), since the adhesive layer was not provided, the adhesiveness of the transparent conductive layer was deteriorated.

In Reference Examples 2-1 and 2-2 (Table 5), the transparent conductive film of Reference Example 1-1 has a refractive index difference of 0.02 or less with respect to the transparent substrate, and a film thickness of 0.8 to 3 By providing a hard coat layer of .mu.m, there is no interference fringes at the interface between the transparent base film and the hard coat layer, and there is no influence of curling due to curing shrinkage, and the hardness and scratch resistance of the transparent conductive film can be increased. I was able to improve.

In Examples 3-1 to 3-3 (Table 6), the transparent conductive film of Example 2-1 was provided with a low refractive index layer having a refractive index of 1.30 to 1.45 and a film thickness of 80 to 110 nm. Further, coloring of the transparent conductive film was further suppressed, and a more excellent total light transmittance could be realized.

In Examples 4-1 to 4-3 (Table 7), the transparent conductive film of Example 1-1 was provided with a low refractive index layer having a refractive index of 1.30 to 1.45 and a thickness of 80 to 110 nm. Further, coloring of the transparent conductive film was further suppressed, and a more excellent total light transmittance could be realized.

Claims (2)

A transparent conductive layer is laminated on one surface of the transparent substrate via an adhesive layer,
The adhesive layer has a thickness of 5 to 30 nm,
The transparent conductive layer is composed of a silver fiber and the transparent resin film having conductivity, Ri thickness 50~200nm der,
A functional layer is laminated on the other surface of the transparent substrate;
The functional layer is a hard coat layer,
Between the transparent substrate and the hard coat layer, an adhesive layer having a thickness of 5 to 30 nm is interposed,
The hard coat layer has a refractive index difference with the transparent substrate of 0.02 or less and a film thickness of 0.8 to 3.0 μm.
On the hard coat layer, as a functional layer, the refractive index is lower than that of the hard coat layer.
Low refractive index layer is laminated,
The low refractive index layer is a transparent conductive film having a refractive index of 1.30 to 1.45 and a film thickness of 80 to 110 nm . A transparent conductive layer is laminated on one surface of the transparent substrate via an adhesive layer,
The adhesive layer has a thickness of 5 to 30 nm,
The transparent conductive layer comprises a conductive silver fiber and a transparent resin coating film, and the film thickness is 50 to 200 nm.
A functional layer is laminated on the other surface of the transparent substrate;
The functional layer is a low refractive index layer having a lower refractive index than the transparent substrate,
Between the transparent substrate and the low refractive index layer, an adhesive layer having a thickness of 5 to 30 nm is interposed,
The low refractive index layer is a transparent conductive film having a refractive index of 1.30 to 1.45 and a film thickness of 80 to 110 nm.