WO2015075876A1 - Transparent conductor and method for producing transparent conductor - Google Patents

Abstract

Provided is a transparent conductor provided with a transparent conductive film using a metal nanowire and having isotropic conductivity. A first transparent conductor provided with a substrate and a transparent conductive film provided on the substrate, wherein the substrate comprises an optically isotropic material, and the transparent conductive film contains a metal nanowire and exhibits a surface resistance ratio (TD/MD) of the TD direction to the MD direction of no less than 0.6 and less than 1.5. A second transparent conductor provided with a substrate, an intermediate layer provided on the substrate, and a transparent conductive film provided on the intermediate layer, wherein the intermediate layer comprises an optically isotropic material, and the transparent conductive film contains a metal nanowire and exhibits a surface resistance ratio (TD/MD) of the TD direction to the MD direction of no less than 0.6 and less than 1.5.

Description

Transparent conductor and method for producing transparent conductor Cross-reference to related applications

This application claims the priority of Japanese Patent Application No. 2013-240134 (filed on November 20, 2013), the entire disclosure of which is incorporated herein by reference.

The present invention relates to a transparent conductor and a method for producing the transparent conductor.

Transparent conductors provided on the display surface of the display panel, and transparent conductors of information input devices arranged on the display surface side of the display panel, such as transparent conductors that require light transmissivity, have a transparent conductive surface. Metal oxides such as indium tin oxide (ITO) have been used for the film. However, transparent conductive films using metal oxides are expensive to produce because they are sputtered in a vacuum environment, and cracks and delamination are likely to occur due to deformation such as bending and deflection. .

Therefore, instead of a transparent conductive film using a metal oxide, a transparent conductive film provided with metal nanowires has been studied as a transparent conductive film that can be formed by coating or printing and has high resistance to bending and bending. ing. Such a transparent conductive film has attracted attention as a next-generation transparent conductive film that does not use indium which is a rare metal (see, for example, Patent Documents 1 and 2 and Non-Patent Document 1).

A method suitable for producing a transparent conductive film using metal nanowires as described above is disclosed in Patent Document 3. In the method described in Patent Document 3, a plurality of metal nanowires are put on a base material (the metal nanowires are dispersed in a liquid), and the liquid is dried to thereby form metal nanowires on a substrate. A wire network layer (a layer in which a plurality of metal nanowires are connected in a network) is formed. Moreover, in this patent document 3, a metal nanowire network layer is formed on a base | substrate by throwing several metal nanowires on a base | substrate, disperse | distributing a metal nanowire in a liquid, and drying this liquid. The matrix material is put on the metal nanowire network layer, and the matrix material is cured to form a matrix, thereby forming a conductive layer including the matrix and metal nanowires embedded in the matrix. Yes. Patent Document 3 describes that a roll-to-roll process is performed. In this case, the substrate is transported along the transport path by the rotating reel, and the metal nanowire is input along the movement path in the first input part, and the matrix material is input in the second input part. Done along the path.

However, in the manufacturing method in which metal nanowires are dispersed in a liquid and a transparent conductive film is formed by drying the liquid as described in Patent Document 3, the conductivity of the formed film is different. For example, in the case of a transparent conductor having a shape shown in FIG. 2 (a laminate of a base material and a transparent conductive film), the transport direction (MD direction) during production and the width direction perpendicular thereto are used. There remains a problem that the conductivity in the (TD direction) tends to be different. As a transparent conductor used for a touch panel or the like, it is desired that its surface has conductivity in all directions, that is, has isotropic conductivity. Therefore, it is desired that the transparent conductive film using metal nanowires has isotropic conductivity in addition to manufacturability and bending resistance.

Special table 2010-507199 Special table 2010-525526 US Patent Application Publication No. 2007/0074316

This invention makes it a subject to solve the said various problems in the past and to achieve the following objectives. That is, it aims at providing the transparent conductor provided with the transparent conductive film using metal nanowire which has isotropic conductivity.

As a result of intensive studies to achieve the above object, the present inventor has found that, in the production of a transparent conductor, an optically isotropic transparent substrate, or an optically isotropic intermediate provided on the transparent substrate. It has been found that by forming a transparent conductive film on a layer (base), a transparent conductor provided with an isotropic conductive transparent conductive film can be produced, and the present invention has been completed.

This invention is based on the said knowledge by the present inventors, and the means for solving the said subject are as follows. That is,
<1> A transparent conductor comprising a base material and a transparent conductive film provided on the base material, wherein the base material is made of an optically isotropic material, A transparent conductor comprising a wire and having a surface resistance value ratio (TD / MD) in the TD direction and the MD direction of 0.6 or more and less than 1.5.
The transparent conductor according to <1> is obtained by providing a transparent conductive film on a substrate made of an optically isotropic material, and the transparent conductive film has no direction dependency on the surface resistance value, Has isotropic conductivity.
As shown in FIG. 2, in the present invention, the “MD direction” refers to the transport direction of the base material during the production of the transparent conductor, and the “TD direction” refers to a direction (base) perpendicular to the transport direction of the base material. (Width direction of the material).
<2> A transparent conductor comprising a base material, an intermediate layer provided on the base material, and a transparent conductive film provided on the intermediate layer, wherein the intermediate layer is optically isotropic The transparent conductive film is made of a material, includes metal nanowires, and has a ratio of surface resistance values in the TD direction and the MD direction (TD / MD) of 0.6 or more and less than 1.5, It is a transparent conductor.
The transparent conductor according to <2> is obtained by providing an intermediate layer made of an optically isotropic material on a base material, and providing a transparent conductive film on the intermediate layer. The surface resistance value has no direction dependency and has isotropic conductivity.
<3> The method for producing a transparent conductive film according to <1> or <2>, wherein the retardation value of the optically isotropic material at a wavelength of 550 nm is 30 nm or less.
In the present invention, the “retardation value” refers to a value obtained by using the rotational analyzer method.
<4> The transparent conductor according to any one of <1> to <3>, wherein the metal nanowire has a length of 1 μm to 100 μm.
<5> A method for producing a transparent conductor according to any one of <1> to <4>, wherein the dispersion includes metal nanowires and a transparent resin material. A transparent conductive film comprising: a step of forming a dispersion film by applying the dispersion onto an optically isotropic material; and a step of drying and curing the dispersion film to form a transparent conductive film. It is a manufacturing method of a body.
According to the method for producing a transparent conductor according to <5>, a transparent conductive film containing metal nanowires is formed on an optically isotropic material, thereby providing an isotropic conductive transparent conductive film. A transparent conductor can be manufactured.
<6> The method for producing a transparent conductor according to <5>, wherein the dispersion has a viscosity of 1 cP or more and 50 cP or less.

According to the present invention, there is provided a transparent conductor having a transparent conductive film using metal nanowires, which can solve the above-mentioned problems and achieve the above-mentioned object and has isotropic conductivity. Can do.

FIG. 1 is a diagram showing an example of the first embodiment (A) and the second embodiment (B) of the transparent conductor of the present invention. FIG. 2 is a schematic diagram showing the transport direction (MD direction) of the base material and the direction (width direction of the base material) (TD direction) orthogonal to the transport direction in the transparent conductor of the present invention.

(Transparent conductor)
The transparent conductor of the present invention is a transparent conductor comprising a base material made of an optically isotropic material and a transparent conductive film provided on the base material, or a base material, and provided on the base material. A transparent conductor comprising an intermediate layer made of the optically isotropic material and a transparent conductive film provided on the intermediate layer.
The said transparent conductive film contains metal nanowire, and also contains a transparent resin material (binder), a solvent, a dispersing agent, and another component as needed.

The transparent conductor of the present invention is formed by forming a transparent conductive film containing metal nanowires on an optically isotropic material, so that the surface has isotropic conductivity, the TD direction (width direction) of the surface, The ratio (TD / MD) of the surface resistance value in the MD direction (conveyance direction) is 0.6 or more and less than 1.5. The following can be considered as a principle capable of forming such an isotropic conductive transparent conductive film.
Optical isotropic materials are known to be random with no molecular orientation on their surfaces. By arranging a dispersion of metal nanowires on this optically isotropic material, the metal nanowires are randomly dispersed on the optically isotropic material without causing a biased interaction. Presumed to build no random metal nanowire network. Here, the “metal nanowire network” means a network structure formed by connecting a plurality of metal nanowires in a network.

In the transparent conductor of the present invention, a form using a substrate made of an optically isotropic material is a first embodiment, and a form in which an intermediate layer made of an optically isotropic material is arranged on any substrate is a second. Let it be an embodiment.

<First Embodiment>
The first embodiment of the present invention uses a base material made of an optically isotropic material, and forms a transparent conductive film directly on the base material without providing an intermediate layer or the like. FIG. 1A shows a transparent conductor according to the first embodiment of the present invention. 1st Embodiment of this invention is the transparent conductor 10 which provides the transparent conductive film 12 on the base material 11 which consists of an optically isotropic material.

<< Base material >>
The base material is not particularly limited as long as it is a base material made of an optically isotropic material, and can be appropriately selected according to the purpose. However, a film required for a transparent electrode provided with a transparent conductive film For example, a film-like (sheet-like) base material thinned to such an extent that flexible flexibility can be realized, or a substrate-like film having a thickness enough to realize appropriate flexibility and rigidity. A substrate is preferred.
The optically isotropic material is not particularly limited and may be appropriately selected depending on the intended purpose. For example, cyclic olefin copolymer (COC), cycloolefin polymer (COP), norbornene resin, triacetyl cellulose (TAC) , Polycarbonate (PC), polyethersulfone (PES), glass, and the like. These may be used individually by 1 type and may use 2 or more types together.
Among these, norbornene resin and triacetyl cellulose are preferable from the viewpoint of excellent bending resistance and heat resistance, and triacetyl cellulose is more preferable from the viewpoint of low substrate cost.
It is also possible to use a commercially available product as the substrate. There is no restriction | limiting in particular as said product marketed, According to the objective, it can select suitably, For example, ZEONOR (trademark) by Nippon Zeon Co., Ltd., ZEONEX (trademark); Arton by JSR Corporation (Registered trademark);
The film thickness of the substrate is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 5 μm to 500 μm from the viewpoint of productivity.
“Optical isotropic” in the present invention indicates that the birefringence is small, for example, that the retardation value at a wavelength of 550 nm is 30 nm or less.
There is no restriction | limiting in particular as a retardation value in wavelength 550nm of the said base material, Although it can select suitably according to the objective, 30 nm or less is preferable, 10 nm or less is more preferable, and 5 nm or less is especially preferable.
If the retardation value of the substrate at a wavelength of 550 nm is more than 30 nm, the optical isotropy of the substrate may be lost. On the other hand, if the retardation value of the substrate at a wavelength of 550 nm is within the more preferable range or the particularly preferable range, it is advantageous in view angle characteristics in a display device incorporating the substrate. Specifically, it is advantageous in that the change in the color tone of the display color depending on the viewing angle and the decrease in contrast are small.
In addition, as the retardation, for example, it is possible to measure by various ellipsometry such as a rotation analyzer method and a Senarmon method, but the “retardation value” in the present invention is a rotation analyzer method. The value obtained by using shall be indicated.

<< Transparent conductive film >>
-Dispersion-
In 1st Embodiment of this invention, the said transparent conductive film is formed by providing the said dispersion liquid containing metal nanowire on the said base material consisting of an optically isotropic material, drying and hardening. Various components of the dispersion and the production method will be described below.

--- Metal nanowires--
The metal nanowire is made of metal and is a fine wire having a diameter on the order of nm.
The constituent element of the metal nanowire is not particularly limited as long as it is a metal element, and can be appropriately selected according to the purpose. For example, Ag, Au, Ni, Cu, Pd, Pt, Rh, Ir, Examples include Ru, Os, Fe, Co, Sn, Al, Tl, Zn, Nb, Ti, In, W, Mo, Cr, Fe, V, Ta, and the like. These may be used individually by 1 type and may use 2 or more types together.
Among these, Ag and Cu are preferable in terms of high conductivity.

The average minor axis diameter of the metal nanowire is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably more than 1 nm and not more than 500 nm, and more preferably 10 nm to 100 nm.
When the average minor axis diameter of the metal nanowire is 1 nm or less, the conductivity of the metal nanowire deteriorates, and the transparent conductive film containing the metal nanowire may not function as a conductive film. If it exceeds, the total light transmittance and haze of the transparent conductive film containing the metal nanowires may deteriorate. On the other hand, when the average minor axis diameter of the metal nanowire is within the more preferable range, it is advantageous in that the transparent conductive film including the metal nanowire has high conductivity and high transparency.

The average major axis length of the metal nanowire is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably more than 1 μm and 1,000 μm or less, more preferably 10 μm to 300 μm.
When the average major axis length of the metal nanowire is 1 μm or less, the metal nanowires are hardly connected to each other, and the transparent conductive film containing the metal nanowire may not function as a conductive film, and exceeds 1,000 μm. And the total light transmittance and haze (Haze) of the transparent conductive film containing the said metal nanowire may deteriorate, or the dispersibility of the metal nanowire in the dispersion liquid used when forming a transparent conductive film may deteriorate. . On the other hand, when the average major axis length of the metal nanowire is within the more preferable range, it is advantageous in that the transparent conductive film including the metal nanowire has high conductivity and high transparency.
The average minor axis diameter and the average major axis length of the metal nanowires are the number average minor axis diameter and the number average major axis length that can be measured with a scanning electron microscope. More specifically, at least 100 metal nanowires are measured, and the projected diameter and projected area of each nanowire are calculated from an electron micrograph using an image analyzer. And this projection diameter was made into the short axis diameter. Further, the major axis length was calculated based on the following formula.
Long axis length = projected area / projected diameter The average minor axis diameter was an arithmetic average value of minor axis diameters. The average major axis length was the arithmetic average value of the major axis length.

Furthermore, the metal nanowire may have a wire shape in which metal nanoparticles are connected in a bead shape. In this case, the length of the metal nanowire is not limited.

The weight per unit area of the metal nanowires is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably ^{0.001g / m 2 ~ 1.000g / m} 2, 0.003g / m 2 ~ 0.3 g / m ² is more preferable.
When the basis weight of the metal nanowire is less than 0.001 g / m ² , the metal nanowire is not sufficiently present in the metal nanowire layer, and the conductivity of the transparent conductive film may be deteriorated. If it exceeds .000 g / m ² , the total light transmittance and haze of the transparent conductive film may deteriorate. On the other hand, when the basis weight of the metal nanowire is within the more preferable range, it is advantageous in that the conductivity of the transparent conductive film is high and the transparency is high.

The compounding amount of the metal nanowires in the dispersion is not particularly limited and may be appropriately selected depending on the purpose. However, when the mass of the dispersion is 100 parts by mass, 10.00 parts by mass is preferred.
The amount of the metal nanowires is less than 0.01 part by weight, sufficient basis weight to the metal nanowires in the final transparent conductive film obtained ^{(0.001g / m 2 ~ 1.000g /} m 2 ) May not be obtained, and if it exceeds 10.00 parts by mass, the dispersibility of the metal nanowires may deteriorate.

-Transparent resin material (binder)-
The transparent resin material (binder) is for dispersing the metal nanowires.
There is no restriction | limiting in particular as said transparent resin material (binder), According to the objective, it can select suitably, For example, a known transparent natural polymer resin, synthetic polymer resin, etc. are mentioned, Thermoplastic It may be a resin, or may be a heat (light) curable resin that is cured by heat, light, electron beam, or radiation. These may be used individually by 1 type and may use 2 or more types together.
The thermoplastic resin is not particularly limited and may be appropriately selected depending on the intended purpose. For example, polyvinyl chloride, vinyl chloride-vinyl acetate copolymer, polymethyl methacrylate, nitrocellulose, chlorinated polyethylene, chlorine Polypropylene, vinylidene fluoride, ethylcellulose, hydroxypropylmethylcellulose, polyvinyl alcohol, polyvinylpyrrolidone, and the like.
The thermosetting (photo) curable resin is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include silicon resins such as melamine acrylate, urethane acrylate, isocyanate, epoxy resin, polyimide resin, and acrylic-modified silicate. And a polymer in which a photosensitive group such as an azide group or a diazirine group is introduced into at least one of a main chain and a side chain.

--solvent--
The solvent is not particularly limited as long as it can disperse metal nanowires, and can be appropriately selected according to the purpose. For example, water; methanol, ethanol, n-propanol, i-propanol, n- Alcohols such as butanol, i-butanol, sec-butanol and tert-butanol; ketones such as cyclohexanone, cyclopentanone and anone; amides such as N, N-dimethylformamide (DMF); sulfides such as dimethyl sulfoxide (DMSO); Etc. These may be used individually by 1 type and may use 2 or more types together.

In order to suppress drying unevenness and cracks in the dispersion film formed using the dispersion, a high boiling point solvent may be further added to the dispersion. Thereby, the evaporation rate of the solvent from the dispersion can be controlled.
The high boiling point solvent is not particularly limited and may be appropriately selected depending on the intended purpose. For example, butyl cellosolve, diacetone alcohol, butyl triglycol, propylene glycol monomethyl ether, propylene glycol monoethyl ether, ethylene glycol monoethyl Ether, ethylene glycol monopropyl ether, ethylene glycol monoisopropyl ether, diethylene glycol monobutyl ether, diethylene glycol monoethyl ether, diethylene glycol monomethyl ether diethylene glycol diethyl ether, dipropylene glycol monomethyl ether, tripropylene glycol monomethyl ether, propylene glycol monobutyl ether, propylene glycol isopropyl A Le, dipropylene glycol isopropyl ether, tripropylene glycol isopropyl ether, methyl glycol, and the like.
These may be used individually by 1 type and may use 2 or more types together.

-Dispersant-
The dispersant is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include polyvinyl pyrrolidone (PVP); amino group-containing compounds such as polyethyleneimine; sulfo groups (including sulfonates) and sulfonyl groups. , Sulfonamide group, carboxylic acid group (including carboxylate), amide group, phosphate group (including phosphate and phosphate ester), phosphino group, silanol group, epoxy group, isocyanate group, cyano group, vinyl group, A compound having a functional group such as a thiol group or a carbinol group, which can be adsorbed to a metal; These may be used alone or in combination of two or more.
The dispersant may be adsorbed on the surface of the metal nanowire. Thereby, the dispersibility of the said metal nanowire can be improved.

When the dispersant is added to the dispersion, it is preferable to add the dispersant so that the conductivity of the finally obtained transparent conductive film does not deteriorate. Thereby, the said dispersing agent can be made to adsorb | suck to metal nanowire by the quantity of the grade which the electroconductivity of a transparent conductive film does not deteriorate.

-Other ingredients-
The other components are not particularly limited and may be appropriately selected depending on the intended purpose. For example, surfactants, viscosity modifiers, curing accelerators, plasticity, stabilizers such as antioxidants and sulfidizing agents, and the like. , Etc. can be added.

-Thickness of transparent conductive film-
The thickness of the transparent conductive film formed by applying the above dispersion onto a substrate is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.1 μm to 500 μm, preferably 1 μm to 100 μm is more preferable, and 10 μm to 50 μm is particularly preferable.
If the thickness of the transparent conductive film is less than 0.1 μm, sufficient conductivity may not be obtained, and if it exceeds 500 μm, in addition to not forming a sufficient network of metal nanowires, the transparency is May get worse. On the other hand, when the thickness of the transparent conductive film is within the more preferable range or the particularly preferable range, it is advantageous in terms of forming a network of metal nanowires.

-Isotropic conductivity of transparent conductive film-
As the ratio (TD / MD) of the surface resistance value in the TD direction (width direction) and the MD direction (transport direction) of the transparent conductive film formed on the substrate, as long as it is 0.6 or more and less than 1.5, Although there is no restriction | limiting in particular, Although it can select suitably according to the objective, 0.8 or more and less than 1.2 are preferable, and 0.9 or more and less than 1.1 are especially preferable.
When the ratio of the surface resistance values is less than 0.6, the conductivity in the TD direction is deteriorated, and when it is 1.5 or more, the conductivity in the MD direction is deteriorated. On the other hand, when the ratio of the surface resistance values is within the preferable range, the more preferable range, or the particularly preferable range, it is advantageous in that the anisotropy of the surface resistance is relaxed and isotropic. That is, it is advantageous in terms of in-plane conductivity.

Second Embodiment
2nd Embodiment of this invention is the transparent conductor which provided the intermediate | middle layer which consists of an optically isotropic material on a base material, and formed the transparent conductive film on this intermediate | middle layer. FIG. 1B shows a transparent conductor according to the second embodiment of the present invention. 2nd Embodiment of this invention is the transparent conductor 10 which has the intermediate | middle layer 13 on the base material 11, and provided the transparent conductive film 12 on this intermediate | middle layer 13. As shown in FIG.

<< Base material >>
There is no restriction | limiting in particular as said base material, Although it can select suitably according to the objective, The transparent base material comprised with the material which has transparency with respect to visible light, such as an inorganic material and a plastic material, is preferable. The transparent substrate has a film thickness required for a transparent electrode having a transparent conductive film, for example, a film-like (sheet-like) substrate thinned to such an extent that flexible flexibility can be realized, Or it shall be a substrate-like base material which has a film thickness which can implement | achieve moderate flexibility and rigidity.
There is no restriction | limiting in particular as said inorganic material, According to the objective, it can select suitably, For example, quartz, sapphire, glass, etc. are mentioned.
There is no restriction | limiting in particular as said plastic material, According to the objective, it can select suitably, For example, a triacetyl cellulose (TAC), polyester (TPEE), a polyethylene terephthalate (PET), a polyethylene naphthalate (PEN), a polyimide (PI), polyamide (PA), aramid, polyethylene (PE), polyacrylate, polyether sulfone, polysulfone, polypropylene (PP), diacetyl cellulose, polyvinyl chloride, acrylic resin (PMMA), polycarbonate (PC), epoxy Known polymer materials such as resin, urea resin, urethane resin, melamine resin, and cycloolefin polymer (COP) can be used. When a transparent substrate is constituted using such a plastic material, the film thickness of the transparent substrate is preferably 5 μm to 500 μm from the viewpoint of productivity, but is not particularly limited to this range.
The base material in the second embodiment does not need to be optically isotropic as compared with the base material in the first embodiment, and therefore is selected widely in consideration of other desired physical properties and costs. Can do.

<< Intermediate layer >>
In the second embodiment of the transparent conductor of the present invention, an intermediate layer made of an optically isotropic material is provided between the substrate and the transparent conductive film. The intermediate layer is formed, for example, by applying an intermediate layer forming solution containing an intermediate layer forming component and a solvent onto a substrate by spin coating or the like, drying the solvent, and curing the intermediate layer forming component. The The intermediate layer made of an optically isotropic material has an advantage that it is relatively inexpensive and easy to manufacture, as compared with a base material made of an optically isotropic material.

-Intermediate layer forming component-
The intermediate layer forming component is not particularly limited as long as it is a material that is optically isotropic in the final product, can be appropriately selected according to the purpose, and is a transparent layer having transparency to visible light. Those that form are preferred.
Specific examples of the intermediate layer forming component are not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include a photocurable resin, a thermosetting resin, and a radiation curable resin. These may be used individually by 1 type and may use 2 or more types together.
There is no restriction | limiting in particular as said photocurable resin, According to the objective, it can select suitably, For example, an acrylic resin, a vinyl resin, a polyester resin, a polyamide resin etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, an acrylic resin is preferable in terms of high transparency and excellent bending resistance.
Moreover, there is no restriction | limiting in particular as said thermosetting resin, According to the objective, it can select suitably, For example, an epoxy resin, an amino resin, a urethane resin etc. are mentioned. These may be used individually by 1 type and may use 2 or more types together.
Among these, an epoxy resin is preferable in that it has high dimensional stability due to less curing shrinkage.
The content of the intermediate layer forming component in the intermediate layer forming solution is not particularly limited and may be appropriately selected depending on the intended purpose. However, since the film is formed by wet coating, the content is 0.1% by mass to 20%. 0.0 mass% is preferable, and 0.5 mass% to 10.0 mass% is more preferable.
When the content of the intermediate layer forming component is less than 0.1% by mass, it may be difficult to produce a uniform film because thick film coating is required. When the content exceeds 20.0% by mass Therefore, it may be difficult to produce a desired thin film. On the other hand, when the content of the intermediate layer forming component is within the more preferable range, it is advantageous in terms of workability during coating.

-solvent-
The solvent constituting the intermediate layer forming solution is not particularly limited as long as it can dissolve or disperse the intermediate layer forming component, and can be appropriately selected according to the purpose. For example, methanol, ethanol , N-propanol, i-propanol, n-butanol, i-butanol, sec-butanol, tert-butanol and other alcohols; cyclohexanone, cyclopentanone, anone, methyl ethyl ketone, dimethyl ketone and other ketones; N, N-dimethylformamide Amides such as (DMF); sulfides such as dimethyl sulfoxide (DMSO); and the like.

-Physical properties of the intermediate layer-
The thickness of the intermediate layer formed by applying the intermediate layer solution on the substrate is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 0.001 μm to 10 μm, preferably 0.005 μm. Is more preferably 5 μm, and particularly preferably 0.01 μm to 1 μm.
If the thickness of the intermediate layer is less than 0.001 μm, the isotropic conductivity of the transparent conductive film may not be obtained. If the thickness exceeds 10 μm, the total light transmittance of the transparent conductive film may be deteriorated. . On the other hand, when the thickness of the transparent conductive film is within the more preferable range or the particularly preferable range, it is advantageous in that the effect of making the transparent conductive film is isotropic conductivity is easily obtained and the manufacturing is easy. It is.
The intermediate layer needs to be optically isotropic.
There is no restriction | limiting in particular as a retardation value in wavelength 550nm of the said intermediate | middle layer, Although it can select suitably according to the objective, 30 nm or less is preferable, 10 nm or less is more preferable, and 5 nm or less is especially preferable.
If the retardation value of the intermediate layer at a wavelength of 550 nm exceeds 30 nm, the optical isotropy of the intermediate layer may be lost. On the other hand, if the retardation value of the intermediate layer at a wavelength of 550 nm is within the more preferable range or the particularly preferable range, it is advantageous in view angle characteristics.

<< Transparent conductive film >>
The transparent conductive film in the second embodiment of the present invention is the same as the transparent conductive film in the first embodiment of the present invention except that the transparent conductive film is formed not on the base material but on the intermediate layer. is there.

(Method for producing transparent conductor)
The method for producing a transparent conductor of the present invention includes at least a dispersion liquid preparation step, a dispersion film formation step, and a transparent conductive film formation step, and further, an intermediate layer formation step and the like appropriately selected as necessary Including other processes.
In the first embodiment, the production of the transparent conductor of the present invention is started from the step of preparing a metal nanowire dispersion and applying the dispersion onto the prepared substrate, while the second embodiment is performed. In a form, it starts from the process of preparing the solution for intermediate | middle layer formation, and providing the said solution for intermediate | middle layer formation on a base material.

The transparent conductive film is prepared by preparing a dispersion containing metal nanowires (dispersion preparation step), and applying the prepared dispersion onto a substrate or intermediate layer made of an optically isotropic material. It forms (dispersion film formation process), and it forms by performing the drying process and hardening process of the said dispersion film (transparent conductive film formation process).

<Dispersion preparation process>
The dispersion preparation step is a step of preparing a dispersion containing the above-described metal nanowires and various blending components. The dispersion method of the dispersion is not particularly limited and may be appropriately selected depending on the purpose. For example, stirring, ultrasonic dispersion, bead dispersion, kneading, homogenizer treatment, pressure dispersion treatment, and the like are preferable. It is mentioned in.

The viscosity of the dispersion is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 cP or more and 50 cP or less, more preferably 10 cP or more and 40 cP or less, and particularly preferably 20 cP or more and 30 cP or less.
When the viscosity of the dispersion is less than 1 cP, the resistance distribution of the transparent conductive film may be deteriorated, and when it exceeds 50 cP, the coatability may be deteriorated. On the other hand, when the viscosity of the dispersion is in the more preferable range or the particularly preferable range, it is advantageous in that a transparent conductive film having a desired thickness can be more easily produced.

<Dispersion film formation process>
The dispersion film forming step is a step of forming the dispersion film by applying the prepared dispersion on a base material or intermediate layer made of an optically isotropic material.
The application method is not particularly limited and may be appropriately selected depending on the intended purpose. Examples thereof include spin coating, wire bar coating, applicator coating, and slit die coating. By the application, a metal nanowire dispersion film is formed on the base material or the intermediate layer.

<Transparent conductive film formation process>
The transparent conductive film forming step is a step of forming a transparent conductive film by subjecting the dispersion film to a drying process (drying process) and a curing process (curing process).

<< Drying process >>
The drying step is a step of removing the solvent in the dispersion film by drying. There is no restriction | limiting in particular as said drying method, According to the objective, it can select suitably, For example, drying with the hot air of a dryer, hotplate drying, oven drying, IR drying, etc. are mentioned.

<< Curing process >>
The curing step is a step of curing the transparent resin material. The curing means is not particularly limited and can be appropriately selected depending on the type of transparent resin material and desired physical properties. Examples thereof include heat treatment, ultraviolet irradiation, and pressure treatment. It is done. Hereinafter, the heat curing process in the case of using a thermosetting resin will be described.
The heating temperature in the heat curing treatment is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 60 ° C to 140 ° C, more preferably 80 ° C to 120 ° C.
When the heating temperature in the heat curing treatment is less than 60 ° C., the time required for drying may become long and workability may deteriorate, and when it exceeds 140 ° C., the balance with the glass transition temperature (Tg) of the substrate The substrate may be distorted. On the other hand, when the heating temperature in the heat curing treatment is in the more preferable range, it is advantageous in terms of forming a network of metal nanowires.
The heating time in the heat curing treatment is not particularly limited and may be appropriately selected depending on the intended purpose, but is preferably 1 minute to 30 minutes, more preferably 2 minutes to 10 minutes, and particularly preferably about 5 minutes. .
When the heating time in the heat curing treatment is less than 1 minute, drying may be insufficient, and when it exceeds 30 minutes, workability may be deteriorated. On the other hand, when the heating time in the heat curing treatment is within the more preferable range or the particularly preferable time, it is advantageous in terms of network formation and workability of the metal nanowires.

<Intermediate layer forming step>
In the production of the second embodiment of the transparent conductor of the present invention, an intermediate layer forming step of forming an intermediate layer on the substrate is required. The intermediate layer forming step includes a step of preparing the intermediate layer forming solution (intermediate layer forming solution preparing step), a step of applying the intermediate layer forming solution onto a substrate (intermediate layer forming solution applying step). And a step of curing the intermediate layer by photocuring or heat curing (intermediate layer curing step).

<< Intermediate layer forming solution preparation process >>
The intermediate layer forming solution preparation step is a step of preparing the intermediate layer forming solution. In the intermediate layer forming solution preparation step, the intermediate layer forming component and the solvent are mixed to prepare an intermediate layer forming solution.

<< Intermediate layer forming solution application process >>
The intermediate layer forming solution application step is a step of applying the intermediate layer forming solution onto a substrate. The application method is not particularly limited and can be appropriately selected depending on the purpose. For example, spin coating, wire bar coating, applicator coating, slit die coating, and spraying. Examples include coating. These may be used individually by 1 type and may use 2 or more types together.
Among these, coating by spin coating is preferable because it is excellent in coating orientation and workability resulting from coating.
The coating (rotation) speed in the case of applying the intermediate layer forming solution by spin coating is not particularly limited and may be appropriately selected depending on the intended purpose. 000 rpm / 30 seconds is preferred. When the coating speed is within the preferable range, the retardation value of the intermediate layer to be formed can be made lower, that is, more optically isotropic.

<< Intermediate layer curing process >>
The intermediate layer curing step is a step of curing the dried intermediate layer by photocuring or heat curing in accordance with the characteristics of the intermediate layer forming component. If the intermediate layer forming component is a photocurable resin, light having a suitable wavelength is irradiated. If the intermediate layer forming component is a thermosetting resin, heat treatment is performed using an oven or a heating roll.

Next, the present invention will be described more specifically with reference to examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
<Preparation of silver nanowire ink (dispersion)>
A silver nanowire ink was prepared with the following composition.
(1) Metal nanowire: Silver nanowire (manufactured by Seashell Technology, AgNW-25, average diameter 25 nm, average length 23 μm): compounding amount 0.05 part by mass (2) binder: hydroxypropyl methylcellulose (manufactured by Aldrich, Viscosity of 2% aqueous solution at 20 ° C. 80 cP to 120 cP (document value)): blending amount 0.15 parts by mass (3) solvent: (i) water: blending amount 89.80 parts by mass, (ii) ethanol: blending amount 10 0.00 parts by mass

<Preparation of silver nanowire transparent conductor>
A silver nanowire transparent conductor was prepared by the following procedure.
As the substrate, an optically isotropic transparent substrate (norbornene resin film (trade name: ZEONOR (registered trademark) film): manufactured by Nippon Zeon Co., Ltd., model number ZF14, film thickness: 100 μm) was used.
The produced silver nanowire ink (dispersion) was applied onto the substrate with a wire bar (counter 10) to form a silver nanowire dispersion film. Here, the basis weight of the silver nanowires was set to about 0.01 g / m ² .
Next, in the atmosphere, hot air was applied to the coated surface with a dryer to remove the solvent in the silver nanowire-dispersed film by drying.
Thereafter, a heat curing treatment at 120 ° C. for 5 minutes was performed in an oven.
Then, the pressurization process was performed using the calendar processing apparatus provided with a column-shaped press roll and a back roll. Both the press roll and the back roll were processed using a steel roll at a load of 4.0 kN and a conveyance speed of 1 m / min.

<Measurement of resistance value>
Measurement was performed by bringing a measuring probe of a resistivity meter EC-80P (manufactured by Napson Co., Ltd.) into contact with the surface of the silver nanowire transparent conductive film. The measurement was performed at any 12 locations, and the average value was taken as the resistance value. The measurement results are shown in Table 1.

<Production of wire electrode>
A line electrode having a width of 5 mm and a length of 50 mm in each of the TD direction and the MD direction was produced by etching the transparent conductive film.

<Measurement of resistance value of wire electrode>
Silver paste AF6100 was attached to both ends of the wire electrode, and after firing at 90 ° C. for 30 minutes, the resistance value was measured using an electrode resistance measuring instrument “117 TRUE RMS MULTITIMER” manufactured by Fluke. The measurement results are shown in Table 1.

<Evaluation of isotropic conductivity>
The ratio of the resistance values in the TD direction and the MD direction (TD / MD) was calculated, and isotropic conductivity was evaluated based on the following evaluation criteria. The evaluation results are shown in Table 1.
○: TD / MD is 0.6 or more and less than 1.5 ×: TD / MD is less than 0.6 or 1.5 or more

<Measurement of retardation value>
The retardation of the substrate and the intermediate layer described later was measured using RETS-100, and the value at a measurement wavelength of 550 nm was used as the retardation value. The retardation of the intermediate layer was measured after forming the intermediate layer on glass (isotropic substrate).

(Example 2)
In Example 1, instead of using a norbornene resin film as the optically isotropic transparent substrate, a TAC film (triacetylcellulose, manufactured by Panac Corporation, model number FT-80SZ, film thickness 80 μm) was used. As in Example 1, a silver nanowire transparent conductor was produced, the resistance value was measured, the line electrode was produced, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation value was measured. Was measured. The results are shown in Table 1.

(Comparative Example 1)
In Example 1, instead of using an optically isotropic norbornene resin film, an optically anisotropic PET film (polyethylene terephthalate, manufactured by Toray Industries, Inc., model number U34, film thickness 125 μm) was used as the transparent substrate. Except that, as in Example 1, a silver nanowire transparent conductor was produced, the resistance value was measured, the line electrode was produced, the resistance value of the line electrode was measured, and the isotropic conductivity was evaluated. The retardation value was measured. The results are shown in Table 1.

(Comparative Example 2)
In Comparative Example 1, the silver nanowire ink was transparent as in Comparative Example 1, except that a spin coater (500 rpm, 30 seconds) was used instead of using a wire bar as a coating method of the silver nanowire ink. Conductors were prepared, resistance values were measured, line electrodes were prepared, resistance values of the line electrodes were measured, isotropic conductivity was evaluated, and retardation values were measured. The results are shown in Table 1.

Example 3
In Comparative Example 1, instead of coating the silver nanowire ink on the substrate, as a pre-process for coating the silver nanowire ink, an optically isotropic intermediate layer is formed by the following procedure, and the silver nanowire is formed. Except that the ink was coated on the optically isotropic intermediate layer, similarly to Comparative Example 1, a silver nanowire transparent conductor was prepared, a resistance value was measured, a line electrode was prepared, and the resistance of the line electrode The value was measured, the isotropic conductivity was evaluated, and the retardation value was measured. The results are shown in Table 1.

<Preparation of optical isotropic intermediate layer forming solution>
An optically isotropic intermediate layer forming solution was prepared with the following composition.
(1) Binder: Pentaerythritol triacrylate (Product name: Aronix M305, manufactured by Toa Gosei Co., Ltd.): 1.50 parts by mass of compound (2) Curing agent: 2-methyl-1- (4-methylthiophenyl) -2 -Morpholinopropan-1-one (Product name: Irgacure 907, manufactured by Ciba Chemical Co., Ltd.): Compounding amount 0.05 parts by mass (3) Solvent: Methyl ethyl ketone: Compounding amount 98.45 parts by mass

<Formation of optical isotropic intermediate layer>
The optically isotropic intermediate layer was formed by the following procedure.
As the substrate, optically anisotropic PET (polyethylene terephthalate, manufactured by Toray Industries, Inc., model number U34, film thickness 125 μm) was used.
The prepared solution for forming an optically isotropic intermediate layer was coated on a substrate under a coating condition of 1,000 rpm for 30 seconds using a spin coater to form a film. Thereafter, heat curing treatment was performed in an oven at 80 ° C. for 5 minutes. Furthermore, using a metal hydride lamp, the binder was cured by irradiating ultraviolet rays with an integrated light quantity of 1,000 J / cm ² under a nitrogen atmosphere to form an optically isotropic intermediate layer.

Example 4
In Example 3, a silver nanowire transparent conductive material was used in the same manner as in Example 3 except that a spin coating apparatus (500 rpm, 30 seconds) was used instead of using a wire bar as a coating method of the silver nanowire ink. The body was produced, the resistance value was measured, the line electrode was produced, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation value was measured. The results are shown in Table 1.

(Example 5)
In Example 4, as the film forming conditions for the optically isotropic intermediate layer, the coating conditions of the spin coater were set to 500 rpm for 30 seconds instead of 1,000 rpm for 30 seconds. Example 4 Similarly, a silver nanowire transparent conductor was prepared, a resistance value was measured, a line electrode was prepared, a resistance value of the line electrode was measured, isotropic conductivity was evaluated, and a retardation value was measured. The results are shown in Table 1.

(Example 6)
In Example 4, as the film forming conditions for the optically isotropic intermediate layer, the coating conditions of the spin coater were set to 2500 rpm for 30 seconds instead of 1,000 rpm for 30 seconds. Similarly to Example 4, a silver nanowire transparent conductor was prepared, the resistance value was measured, the line electrode was prepared, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation value was measured. . The results are shown in Table 1.

(Example 7)
In Comparative Example 1, instead of coating the silver nanowire ink on the substrate, as a pre-process for coating the silver nanowire ink, an optically isotropic intermediate layer is formed by the following procedure, and the silver nanowire is formed. Except that the ink was coated on the optically isotropic intermediate layer, similarly to Comparative Example 1, a silver nanowire transparent conductor was prepared, a resistance value was measured, a line electrode was prepared, and the resistance of the line electrode The value was measured, the isotropic conductivity was evaluated, and the retardation value was measured. The results are shown in Table 1.

<Preparation of optical isotropic intermediate layer solution>
An optically isotropic intermediate layer forming solution was prepared with the following composition.
(1) Binder: Pentaerythritol triacrylate (Product name: Aronix M305, manufactured by Toa Gosei Co., Ltd.): Compounding amount 1.50 parts by mass (2) Curing agent: Hexamethylene diisocyanate (Product name: Duranate TPA-100, Asahi Kasei Chemicals) Co., Ltd.): 0.25 part by mass (3) Solvent: methyl ethyl ketone: 98.25 parts by mass

<Preparation of optical isotropic intermediate layer>
An optically isotropic intermediate layer was produced by the following procedure.
As the substrate, optically anisotropic PET (polyethylene terephthalate, manufactured by Toray Industries, Inc., model number U34, film thickness 125 μm) was used.
The produced optically isotropic intermediate layer solution was coated on a substrate under a coating condition of 2,500 rpm for 30 seconds using a spin coater to form a film. Thereafter, a heat curing treatment at 80 ° C. for 60 minutes was performed in an oven.

(Comparative Example 3)
In Example 4, as a pre-process for applying the silver nanowire ink, instead of forming the optically isotropic intermediate layer, it was carried out except that the intermediate layer was formed using the intermediate layer forming solution shown below. Similarly to Example 4, a silver nanowire transparent conductor was prepared, the resistance value was measured, the line electrode was prepared, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation value was measured. . The results are shown in Table 1.
<Preparation of intermediate layer forming solution>
An intermediate layer forming solution was prepared with the following composition.
(1) Binder: Retardation material solution (RMS03-013C, manufactured by Merck & Co., Inc., 30% by mass of liquid crystal): Liquid crystal equivalent 18% by mass
(2) Solvent: Propylene glycol monomethyl ether acetate (PGMEA)
RMS03-013C (liquid crystal 30% by mass) was diluted with PGMEA so that the liquid crystal mass was 18% by mass.

(Comparative Example 4)
In Comparative Example 3, the intermediate layer was formed using a spin coater at 1,000 rpm for 30 seconds, instead of 1,600 rpm for 30 seconds. Other than the above, as in Comparative Example 3, a silver nanowire transparent conductor was prepared, the resistance value was measured, the line electrode was prepared, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation was measured. The value was measured. The results are shown in Table 1.

(Comparative Example 5)
In Comparative Example 3, the formation of the intermediate layer was performed using a spin coater under the coating conditions of 3,200 rpm for 30 seconds instead of being performed under the conditions of 1,000 rpm for 30 seconds. Other than the above, as in Comparative Example 3, a silver nanowire transparent conductor was prepared, the resistance value was measured, the line electrode was prepared, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation was measured. The value was measured. The results are shown in Table 1.

(Example 8)
In Comparative Example 3, the intermediate layer was formed using a spin coater under a coating condition of 3,800 rpm for 30 seconds instead of a coating speed of 1,000 rpm for 30 seconds. Other than the above, as in Comparative Example 3, a silver nanowire transparent conductor was prepared, the resistance value was measured, the line electrode was prepared, the resistance value of the line electrode was measured, the isotropic conductivity was evaluated, and the retardation was measured. The value was measured. The results are shown in Table 1.

From Table 1, it was found that good isotropic conductivity was obtained in a transparent conductor having a retardation value of 30 nm or less of a base material or an intermediate layer directly formed with a transparent conductive film containing silver nanowires.
Further, also in the case of using a liquid crystal solution as the intermediate layer (Example 8), the retardation value of the intermediate layer formed by increasing the number of rotations during spin coating can be lowered. It was found that isotropic conductivity can be obtained. Therefore, the isotropic conductive transparent conductor of the present invention is not achieved by using a specific material for the base material or the intermediate layer, and does not depend on the material, and is an optically isotropic base material or intermediate material. It has been found that this can be achieved by using a layer.

The transparent conductor of the present invention can be suitably used as an alternative to a transparent conductor using a metal oxide such as indium tin oxide (ITO) used in electronic devices such as notebook computers and smartphones. .

DESCRIPTION OF SYMBOLS 10 Transparent conductor 11 Base material 12 Transparent conductive film 13 Intermediate | middle layer

Claims (6)

1. A transparent conductor comprising a substrate and a transparent conductive film provided on the substrate,
   The substrate is made of an optically isotropic material;
   The said transparent conductive film contains metal nanowire, and ratio (TD / MD) of the surface resistance value in TD direction and MD direction is 0.6 or more and less than 1.5, The transparent conductor characterized by the above-mentioned.
2. A transparent conductor comprising a base material, an intermediate layer provided on the base material, and a transparent conductive film provided on the intermediate layer,
   The intermediate layer is made of an optically isotropic material;
   The said transparent conductive film contains metal nanowire, and ratio (TD / MD) of the surface resistance value in TD direction and MD direction is 0.6 or more and less than 1.5, The transparent conductor characterized by the above-mentioned.
3. The transparent conductor according to claim 1 or 2, wherein the retardation value of the optically isotropic material at a wavelength of 550 nm is 30 nm or less.
4. 3. The transparent conductor according to claim 1, wherein the metal nanowire has a length of 1 μm to 100 μm.
5. It is a manufacturing method of the transparent conductor which manufactures the transparent conductor according to claim 1 or 2,
   Preparing a dispersion containing metal nanowires and a transparent resin material;
   Applying the dispersion onto an optically isotropic material to form a dispersion film;
   A step of drying and curing the dispersion film to form a transparent conductive film.
6. The method for producing a transparent conductor according to claim 5, wherein the dispersion has a viscosity of 1 cP or more and 50 cP or less.

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