JP7820123B2 - Transparent Conductive Film - Google Patents

Description

The present invention relates to a transparent conductive film.

Conventionally, transparent conductive films used in touch sensor electrodes and the like often consist of a transparent resin film on which a metal oxide layer, such as an indium-tin composite oxide layer (ITO layer), is formed. However, transparent conductive films with a metal oxide layer formed on them have insufficient flexibility, making them difficult to use in applications requiring flexibility, such as flexible displays.

Transparent conductive films with a conductive layer containing metal nanowires have been proposed as highly flexible transparent conductive films. However, such transparent conductive films suffer from the problem of the metal nanowires degrading under high humidity conditions, resulting in increased resistance. One possible solution to this problem is to protect the conductive layer composed of metal nanowires with a polymer matrix. However, even with this technology, it is difficult to fully prevent degradation of the metal nanowires.

Special Publication No. 2009-505358

The present invention has been made to solve the above problems, and its purpose is to provide a transparent conductive film that has a conductive layer containing metal nanowires and has excellent humidification reliability.

The transparent conductive film of the present invention comprises a transparent substrate and a transparent conductive layer disposed on at least one side of the transparent substrate, the transparent conductive layer containing metal nanowires and a polymer matrix, and the polymer matrix containing a thiol-based compound.
In one embodiment, the thiol compound is a thiol compound having a dithiolane skeleton.
In one embodiment, the thiol compound is α-lipoic acid.
In one embodiment, the content of the thiol compound having a dithiolane skeleton is 0.1 to 5 parts by weight relative to 100 parts by weight of the polymer constituting the polymer matrix.
In one embodiment, the metal nanowires have a fused network structure.
In one embodiment, the transparent conductive layer further contains a silane coupling agent.
In one embodiment, the transparent conductive layer has a visible light transmittance of 80% or more.
In one embodiment, the transparent conductive layer has a sheet resistivity of 200 Ω/□ or less.

The present invention provides a transparent conductive film that has a conductive layer containing metal nanowires and has excellent humidification reliability.

1 is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention.

A. Overview of Transparent Conductive Film Figure 1 is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention. The transparent conductive film 100 comprises a transparent substrate 10 and a transparent conductive layer 20 disposed on at least one side of the transparent substrate 10. The transparent conductive layer 20 includes metal nanowires 21 and a polymer matrix 22. Typically, the transparent conductive layer 20 is configured so that the metal nanowires 21 are present in the polymer matrix 22.

The polymer matrix contains a thiol-based compound. In the present invention, it is believed that the thiol-based compound added to the polymer matrix constituting the transparent conductive layer bonds to the metal nanowires in such a way as to form a protective film on the surface, thereby preventing deterioration of the metal nanowires. The transparent conductive film of the present invention, which exhibits such effects, is able to maintain favorable conductivity without causing deterioration of the metal nanowires even under high humidity conditions. This effect is further enhanced by appropriately selecting the thiol-based compound, as described below. In the present invention, even though metal nanowires are used as the material constituting the transparent conductive layer, deterioration of the material is prevented, thereby enabling the production of a transparent conductive film with excellent flexibility and high environmental durability.

The thickness of the transparent conductive film is preferably 10 μm to 500 μm, more preferably 15 μm to 300 μm, and even more preferably 20 μm to 200 μm.

The visible light transmittance of the transparent conductive film is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. Within this range, a transparent conductive film suitable for use as a transparent electrode can be obtained.

The sheet resistance of the transparent conductive film is preferably 200 Ω/□ or less, more preferably 150 Ω/□ or less, and even more preferably 100 Ω/□ or less. The lower the sheet resistance of the transparent conductive film, the better, but the lower limit is, for example, 1 Ω/□ (preferably 0.5 Ω/□, more preferably 0.1 Ω/□).

B. Transparent Conductive Layer As described above, the transparent conductive layer contains metal nanowires and a polymer matrix. By forming a transparent conductive layer containing metal nanowires, a transparent conductive film with excellent flexibility and light transmittance can be obtained. The metal nanowires are protected by the polymer matrix. As a result, corrosion of the metal nanowires is prevented, and a transparent conductive film with excellent durability can be obtained. The polymer matrix contains a thiol-based compound.

The thickness of the transparent conductive layer is preferably 10 nm to 1000 nm, and more preferably 20 nm to 500 nm.

The visible light transmittance of the transparent conductive layer is preferably 80% or more, more preferably 85% or more, even more preferably 90% or more, and particularly preferably 95% or more.

The sheet resistance of the transparent conductive layer is preferably 200 Ω/□ or less, more preferably 150 Ω/□ or less, and even more preferably 100 Ω/□ or less. The lower the sheet resistance of the transparent conductive film, the better, but the lower limit is, for example, 1 Ω/□ (preferably 0.5 Ω/□, more preferably 0.1 Ω/□).

(metal nanowires)
Metal nanowires are conductive materials made of metal, shaped like needles or threads, and nanometer-sized diameters. Metal nanowires may be linear or curved. By using a transparent conductive layer made of metal nanowires, the metal nanowires form a mesh, allowing even a small amount of metal nanowires to form an excellent electrical conduction path, resulting in a transparent conductive film with low electrical resistance. Furthermore, the mesh-like shape of the metal nanowires allows openings to be formed in the gaps between the meshes, resulting in a transparent conductive film with high light transmittance.

The ratio of the thickness d to the length L of the metal nanowire (aspect ratio: L/d) is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. By using metal nanowires with such a high aspect ratio, the metal nanowires can be well intersected, enabling high conductivity to be achieved with a small number of metal nanowires. As a result, a transparent conductive film with high light transmittance can be obtained. Note that, in this specification, "thickness of a metal nanowire" refers to the diameter if the cross section of the metal nanowire is circular; the minor axis if the cross section is elliptical; and the longest diagonal if the cross section is polygonal. The thickness and length of a metal nanowire can be confirmed using a scanning electron microscope or a transmission electron microscope.

The thickness of the metal nanowires is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably 10 nm to 100 nm, and most preferably 10 nm to 50 nm. Within this range, a transparent conductive layer with high light transmittance can be formed.

The length of the metal nanowires is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and particularly preferably 10 μm to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

Any suitable metal can be used as the metal constituting the metal nanowires, as long as it is conductive. Examples of metals constituting the metal nanowires include silver, gold, copper, and nickel. Materials obtained by plating these metals (e.g., gold plating) may also be used. Among these, silver, copper, or gold are preferred from the viewpoint of conductivity, and silver is even more preferred.

Any suitable method can be used to manufacture the metal nanowires. Examples include reducing silver nitrate in solution, applying a voltage or current from the tip of a probe to the surface of a precursor, drawing out the metal nanowires at the tip of the probe, and continuously forming the metal nanowires. In the method of reducing silver nitrate in solution, silver nanowires 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. Uniformly sized silver nanowires can be mass-produced, for example, according to the methods described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745 and Xia, Y. et al., Nano Letters (2003), 3(7), 955-960.

The transparent conductive layer containing the metal nanowires can be formed by applying a dispersion of the metal nanowires in a solvent onto the transparent substrate and then drying the applied layer.

Examples of the solvent include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. From the perspective of reducing environmental impact, it is preferable to use water.

The dispersion concentration of the metal nanowires in the metal nanowire dispersion liquid is preferably 0.1% to 1% by weight. Within this range, a transparent conductive layer with excellent conductivity and light transparency can be formed.

The metal nanowire dispersion liquid may further contain any appropriate additives depending on the purpose. Examples of such additives include corrosion inhibitors that prevent corrosion of the metal nanowires, surfactants that prevent aggregation of the metal nanowires, etc. The type, number, and amount of additives used may be appropriately determined depending on the purpose.

Any appropriate method can be used to apply the metal nanowire dispersion. Examples of application methods include spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, intaglio printing, and gravure printing. Any appropriate drying method (e.g., natural drying, air drying, and heat drying) can be used to dry the coated layer. For example, in the case of heat drying, the drying temperature is typically 50°C to 200°C, and the drying time is typically 1 to 10 minutes.

The content of metal nanowires in the transparent conductive layer is preferably 30% to 90% by weight, and more preferably 45% to 80% by weight, based on the total weight of the transparent conductive layer. Within this range, a transparent conductive film with excellent conductivity and light transparency can be obtained.

When the metal nanowires are silver nanowires, the density of the transparent conductive layer is preferably 1.3 g/cm ³ to 10.5 g/cm ³ , and more preferably 1.5 g/cm ³ to 3.0 g/cm ^3. Within such a range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

In one embodiment, the transparent conductive layer is patterned. Any appropriate method can be used as the patterning method depending on the form of the transparent conductive layer. The pattern shape of the transparent conductive layer can be any appropriate shape depending on the application. Examples include the patterns described in JP-T-2011-511357, JP-A-2010-164938, JP-A-2008-310550, JP-T-2003-511799, and JP-T-2010-541109. After the transparent conductive layer is formed on the transparent substrate, it can be patterned using any appropriate method depending on the form of the transparent conductive layer.

In one embodiment, the metal nanowires in the transparent conductive layer have a fused network structure. Metal nanowires with a fused network structure are in a state in which the metal nanowires are fused to each other at their contact points. By forming a transparent conductive layer containing metal nanowires with a fused network structure, a transparent conductive film with higher conductivity can be obtained without impairing transparency.

The transparent conductive layer containing the metal nanowires having the fused network structure can be formed, for example, by adding an additive to the metal nanowire dispersion to promote fusion. Examples of such additives include metal halides (e.g., LiCl, CsCl, NaF, NaCl, NaBr, NaI, KCl, MgCl ₂ , CaCl ₂ , AlCl ₃ , AgF, etc.), inorganic acids (e.g., nitric acid, nitrous acid, sulfuric acid, etc.), organic acids (e.g., oxalic acid, citric acid, formic acid, acetic acid, lactic acid, propionic acid, butyric acid, acrylic acid, pyruvic acid, trichloroacetic acid, trifluoroacetic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic (lauric) acid, tetradecanoic (myristic) acid, hexadecanoic (palmitic) acid, octadecanoic (stearic) acid, 2-ethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 2-propylpentanoic acid, pivalic acid, Examples of suitable silver salts include silver salts (e.g., silver nitrate, silver nitrite, silver lactate, silver chloride, silver sulfate, silver oxide, silver acetate, silver chlorate, silver sulfide, silver formate, silver hexanoate, silver octanoate, silver decanoate, silver dodecanoate, silver tetradecanoate, silver hexadecanoate, silver octadecanoate, silver pentanoate, silver pivalate, silver neoheptanoate, silver neononanoate, silver neodecanoate), and compounds containing elements capable of forming silver salts (e.g., chlorine, sulfur) (e.g., hydrogen chloride, sodium chloride). Among these, metal halides are preferred, and NaCl, AgF, LiF, NaBr, or NaF is more preferred. In one embodiment, the transparent conductive layer containing the metal nanowires having a fused network structure can be formed by applying a metal nanowire dispersion containing the additive, followed by a heat treatment and/or a pressure treatment. The temperature of the heat treatment is, for example, 50°C to 200°C.

A transparent conductive layer containing metal nanowires having the above-mentioned fused network structure may be formed by exposing a coating layer of a metal nanowire dispersion to acid halide vapor. Examples of acid halide vapor include vapors of HCl, HBr, HI, or mixtures thereof.

Metal nanowires with a fused network structure and a method for producing them are described, for example, in JP-A-2015-530693. The disclosure of this publication is incorporated herein by reference.

(polymer matrix)
Any appropriate polymer can be used as the polymer constituting the polymer matrix. Examples of such polymers include acrylic polymers; polyester polymers such as polyethylene terephthalate; aromatic polymers such as polystyrene, polyvinyl toluene, polyvinyl xylene, polyimide, polyamide, and polyamideimide; polyurethane polymers; epoxy polymers; polyolefin polymers; acrylonitrile-butadiene-styrene copolymers (ABS); cellulose; silicone polymers; polyvinyl chloride; polyacetate; polynorbornene; synthetic rubber; and fluorine-based polymers. Preferably, a curable resin (preferably an ultraviolet-curable resin) composed of a polyfunctional acrylate such as pentaerythritol triacrylate (PETA), neopentyl glycol diacrylate (NPGDA), dipentaerythritol hexaacrylate (DPHA), dipentaerythritol pentaacrylate (DPPA), or trimethylolpropane triacrylate (TMPTA) is used.

The polymer matrix can be formed by forming a layer of metal nanowires on a transparent substrate, applying a polymer solution to the layer, and then drying or curing the applied layer, as described above. This process forms a transparent conductive layer in which metal nanowires are present in a polymer matrix.

The polymer solution contains the polymer that constitutes the polymer matrix or a precursor of the polymer (the monomer that constitutes the polymer).

The polymer solution may contain a solvent. Examples of solvents contained in the polymer solution include alcohol-based solvents, ketone-based solvents, tetrahydrofuran, hydrocarbon-based solvents, and aromatic solvents. Preferably, the solvent is volatile. The boiling point of the solvent is preferably 200°C or less, more preferably 150°C or less, and even more preferably 100°C or less.

(Thiol compounds)
The thiol compound may be, for example, a compound represented by general formula (1).
HS-R...(1)
In formula (1), R is an aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 30 carbon atoms, preferably an aliphatic hydrocarbon group or aromatic hydrocarbon group having 1 to 20 carbon atoms. R may be linear or branched. R may also contain a double bond and/or a triple bond at any appropriate position. R may also have any appropriate substituent. Examples of the substituent include an SH group, a hydroxyl group, an _NH2 group, an alkyl ester group, a carboxyl group, an allyl group, and a halogen group. R may also have a substituent containing an element such as N, S, O, Si, or P. Specific examples of thiol compounds include α-thioglycerol, aminoethanethiol, thioglycolic acid, methyl thioglycolate, ethyl thioglycolate, propyl thioglycolate, butyl thioglycolate, t-butyl thioglycolate, 2-ethylhexyl thioglycolate, octyl thioglycolate, isooctyl thioglycolate, decyl thioglycolate, dodecyl thioglycolate, thioglycolic acid esters of ethylene glycol, thioglycolic acid esters of neopentyl glycol, and thioglycolic acid esters of pentaerythritol.

In one embodiment, a thiol-based compound having a dithiolane skeleton (preferably a 1,2-dithiolane skeleton) is used. Thiol-based compounds having a dithiolane skeleton are characterized by their resistance to reaction with compounds constituting the polymer matrix. Therefore, they do not impair the protective function of the polymer matrix and can form a conductive layer that exhibits excellent adhesion to the transparent substrate. Furthermore, because thiol-based compounds having a dithiolane skeleton have two bonding points, they can densely coat the metal nanowires. Even a small amount of such a thiol-based compound can contribute to improved moisture resistance. Adding a small amount of thiol-based compound does not impair the protective function of the polymer matrix and can form a conductive layer that exhibits excellent adhesion to the transparent substrate.

Examples of thiol compounds having a dithiolane skeleton include α-lipoic acid, 5-(1,2-dithiolan-3-yl)pentanamide, and 4-methyl-1,2-dithiolane-4-carboxamide. Among these, α-lipoic acid is particularly preferred. The use of α-lipoic acid not only significantly enhances the above-mentioned effects, but also allows for the production of transparent conductive films with superior durability due to the radical trapping and antioxidant properties of α-lipoic acid.

In one embodiment, an alkylthiol is used as the thiol compound. Specific examples of alkylthiols include methanethiol, ethanethiol, propanethiol, n-octanethiol, n-dodecanethiol, hexadecanethiol, and n-octadecanethiol.

The content of the thiol compound is preferably 0.04 to 10 parts by weight, more preferably 0.1 to 8 parts by weight, and even more preferably 0.12 to 5 parts by weight, relative to 100 parts by weight of the polymer constituting the polymer matrix. Within this range, a transparent conductive film with excellent moisture resistance can be obtained. In one embodiment, when a thiol compound having a dithiolane skeleton is used as the thiol compound, the content of the thiol compound having a dithiolane skeleton is preferably 0.1 to 5 parts by weight, more preferably 0.15 to 3 parts by weight, relative to 100 parts by weight of the polymer constituting the polymer matrix. Within this range, a transparent conductive film with not only excellent moisture resistance but also remarkably excellent conductivity can be obtained. If the content of the thiol compound having a dithiolane skeleton is too high, the thiol compound may react with the metal nanowires, resulting in a decrease in conductivity.

(Coupling Agent)
In one embodiment, the transparent conductive layer (essentially the polymer matrix) further contains a coupling agent. A silane coupling agent is preferably used as the coupling agent. By adding a coupling agent, a transparent conductive film having excellent adhesion between the transparent substrate and the transparent conductive layer can be obtained. Generally, coupling agents act to reduce moisture resistance (humidification reliability). However, according to the present invention, by using a thiol-based compound in combination with a coupling agent, a transparent conductive film having excellent adhesion between the transparent substrate and the transparent conductive layer can be obtained while preventing deterioration of the metal nanowires and maintaining humidification reliability. In other words, the present invention is advantageous in that the effectiveness of the coupling agent is enhanced by including a thiol-based compound.

As the silane coupling agent, an amino-based silane coupling agent is preferably used. It is also possible to use a combination of an amino-based silane coupling agent and an acrylic silane coupling agent.

Examples of amino-based silane coupling agents include γ-aminopropyltriethoxysilane, γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltrimethoxysilane, N-(β-aminoethyl)-γ-aminopropyltriethoxysilane, N-(β-aminoethyl)-γ-aminopropylmethyldimethoxysilane, γ-phenylaminopropyltrimethoxysilane, and 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine. Furthermore, many amino-based silane coupling agents are commercially available. Specific examples of commercially available products include KBE-9103, KBM-575, and KBM-6123 manufactured by Shin-Etsu Chemical Co., Ltd., and A-1102, A-1122, and A-1170 manufactured by Momentive Performance Materials Japan, Inc. 3-triethoxysilyl-N-(1,3-dimethylbutylidene)propylamine is preferred.

Acrylic silane coupling agents are typically silane coupling agents having a (meth)acrylic group in the backbone. Examples of acrylic silane coupling agents include 3-methacryloxypropyltrimethoxysilane, 3-methacryloxypropyltriethoxysilane, 3-acryloxypropyltrimethoxysilane, 3-acryloxypropyltriethoxysilane, methacryloxymethyltrimethoxysilane, methacryloxymethyltriethoxysilane, acryloxymethyltrimethoxysilane, acryloxymethyltriethoxysilane, and 3-methacryloxypropylmethyldimethoxysilane. Furthermore, many acrylic silane coupling agents are commercially available. Specific examples of commercially available products include KBM-502 and KBM-5103 manufactured by Shin-Etsu Chemical Co., Ltd. Preferred are 3-acryloxypropyltrimethoxysilane and 3-methacryloxypropylmethyldimethoxysilane.

The content of the coupling agent (preferably a silane coupling agent) is preferably 0.001 to 20 parts by weight, and more preferably 0.02 to 10 parts by weight, per 100 parts by weight of the polymer that constitutes the polymer matrix. Within this range, a transparent conductive film with excellent adhesion between the transparent substrate and the transparent conductive layer can be obtained.

C. Transparent Substrate The thickness of the transparent substrate is preferably 8 μm to 500 μm, more preferably 10 μm to 250 μm, still more preferably 10 μm to 150 μm, and particularly preferably 15 μm to 100 μm.

The total light transmittance of the transparent substrate is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. Within this range, a transparent conductive film suitable for use in touch panels and the like can be obtained.

Any suitable resin can be used as the resin constituting the transparent substrate, as long as the effects of the present invention can be obtained. Examples of resins constituting the transparent substrate include cycloolefin-based resins, polyimide-based resins, polyvinylidene chloride-based resins, polyvinyl chloride-based resins, polyethylene terephthalate-based resins, and polyethylene naphthalate-based resins. Cycloolefin-based resins are preferred. Using cycloolefin-based resins makes it possible to inexpensively obtain transparent substrates with high moisture barrier properties.

As the cycloolefin-based resin, for example, polynorbornene can be preferably used. Polynorbornene refers to a (co)polymer obtained using norbornene-based monomers having a norbornene ring as some or all of the starting materials (monomers).

A variety of polynorbornene products are commercially available. Specific examples include "Zeonex" and "Zeonor" manufactured by Zeon Corporation, "Arton" manufactured by JSR Corporation, "Topas" manufactured by TICONA, and "APEL" manufactured by Mitsui Chemicals, Inc.

The glass transition temperature of the resin constituting the transparent substrate is preferably 50°C to 200°C, more preferably 60°C to 180°C, and even more preferably 70°C to 160°C.
If the transparent substrate has a glass transition temperature in this range, deterioration during the formation of the transparent conductive layer can be prevented.

The transparent substrate may further contain any appropriate additives as needed. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinkers, and thickeners. The types and amounts of additives used can be appropriately determined depending on the purpose.

The transparent substrate can be obtained by any suitable molding method, such as compression molding, transfer molding, injection molding, extrusion molding, blow molding, powder molding, FRP molding, and solvent casting. Among these methods, extrusion molding or solvent casting is preferred, as this increases the smoothness of the resulting transparent substrate and provides good optical uniformity. Molding conditions can be set appropriately depending on the composition and type of resin used.

If necessary, the transparent substrate may be subjected to various surface treatments. Any appropriate method may be used for the surface treatment depending on the purpose. Examples include low-pressure plasma treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. In one embodiment, the transparent substrate is surface-treated to make the surface of the transparent substrate hydrophilic.

The present invention will be explained in detail below using examples, but the present invention is not limited to these examples in any way. The evaluation methods used in the examples and comparative examples are as follows.

(1) Surface Resistivity: Measured using a product manufactured by NAPSON under the trade name "EC-80". The measurement temperature was 23°C.
(2) Haze: Measurement was performed using an instrument manufactured by Murakami Color Research Institute Co., Ltd. under the trade name "HR-100." The measurement temperature was 23° C. The average value obtained by repeating the measurement three times was used as the measured value.
(3) Humidification Test The transparent conductive film was placed in a humidifying oven at a temperature of 65° C. and a humidity of 90%, and left for 500 hours, after which the above measurements (1) and (2) were carried out.
(4) Adhesion (cross-cut peel test)
The transparent conductive film was placed in a humidified oven at a temperature of 65°C and a humidity of 90%, and after leaving it for 500 hours, 100 grids were formed on the transparent conductive layer side of the transparent conductive film, and a cross-cut peel test was carried out in accordance with JIS K 5400. The test was carried out on three transparent conductive films, and the number of peeled grids was counted.

[Production Example 1] (Synthesis of silver nanowires and preparation of silver nanowire dispersion)
In a reaction vessel equipped with a stirrer, 5 ml of anhydrous ethylene glycol and 0.5 ml of anhydrous ethylene glycol solution of PtCl2 (concentration: 1.5 x ^10-4 mol/L) were added at 160°C. After 4 minutes, 2.5 ml of anhydrous ethylene glycol solution of _AgNO3 (concentration: 0.12 mol/L) and 5 ml of anhydrous ethylene glycol solution of polyvinylpyrrolidone (MW: 55,000) (concentration: 0.36 mol/L) were simultaneously added dropwise to the resulting solution over 6 minutes. After this addition, the mixture was heated to 160°C and reacted for over 1 hour until the _AgNO3 was completely reduced, producing silver nanowires. Next, acetone was added to the reaction mixture containing the silver nanowires obtained as described above until the volume of the reaction mixture was 5 times that of the reaction mixture, and the reaction mixture was centrifuged (2000 rpm, 20 minutes) to obtain silver nanowires.
The obtained silver nanowires had a minor axis of 30 nm to 40 nm, a major axis of 30 nm to 50 nm, and a length of 5 μm to 50 μm.
The silver nanowires (concentration: 0.2 wt %) and pentaethylene glycol dodecyl ether (concentration: 0.1 wt %) were dispersed in pure water to prepare a silver nanowire dispersion liquid I.

[Example 1]
A commercially available long cycloolefin (norbornene) resin film (manufactured by Zeon Corporation, product name "ZEONOR ZF16," thickness 40 μm) was used as the substrate. Silver nanowire dispersion liquid I was applied to this substrate and dried. Next, as a material for forming the overcoat layer, resin composition A was prepared by blending 80 parts by weight of DIC Corporation's product name "UNIDIC ELS-888" and 20 parts by weight of DIC Corporation's product name "UNIDIC RS28-605." This resin composition A was applied to the conductive layer and irradiated with ultraviolet light at an exposure dose of 230 mJ/ ^cm² to form a polymer matrix, resulting in a transparent conductive film. The surface resistance of the transparent conductive film was 50 Ω, and the transparent conductive layer was 60 nm thick.

[Example 2]
A transparent conductive film was obtained in the same manner as in Example 1, except that the amount of α-lipoic acid added was 3 parts by weight per 100 parts by weight of the resin composition A. The obtained transparent conductive film was subjected to the above evaluations. The results are shown in Table 1.

[Example 3]
A transparent conductive film was obtained in the same manner as in Example 1, except that 0.15 parts by weight of decanethiol was used instead of 0.15 parts by weight of α-lipoic acid. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Example 4]
A transparent conductive film was obtained in the same manner as in Example 3, except that the amount of decanethiol added was 3 parts by weight. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Example 5]
A transparent conductive film was obtained in the same manner as in Example 1, except that 0.15 parts by weight of perfluorodecanethiol was used instead of 0.15 parts by weight of α-lipoic acid. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Example 6]
A transparent conductive film was obtained in the same manner as in Example 5, except that the amount of perfluorodecanethiol added was 3 parts by weight. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Comparative Example 1]
A transparent conductive film was obtained in the same manner as in Example 1, except that the thiol compound and the silane coupling agent were not added. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Comparative Example 2]
A transparent conductive film was obtained in the same manner as in Example 1, except that no thiol-based compound was added. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

[Comparative Example 3]
A transparent conductive film was obtained in the same manner as in Example 1, except that no thiol compound was added and the thickness of the transparent conductive layer was set to 90 nm. The obtained transparent conductive film was subjected to the above-mentioned evaluations. The results are shown in Table 1.

As is clear from Table 1, according to the present invention, a transparent conductive film can be obtained that contains metal nanowires and yet has excellent adhesion of the transparent conductive layer to the transparent substrate, even under humidified conditions, and exhibits little change in resistance value and haze, i.e., a transparent conductive film with excellent humidification reliability.

REFERENCE SIGNS LIST 10 Transparent substrate 20 Transparent conductive layer 21 Metal nanowires 22 Polymer matrix 100 Transparent conductive film

Claims (7)

A transparent substrate;
a transparent conductive layer disposed on at least one side of the transparent substrate;
the transparent conductive layer comprises metal nanowires and a polymer matrix;
the polymer matrix comprises a thiol-based compound;
the thiol compound is a thiol compound having a dithiolane skeleton;
Transparent conductive film. 2. The transparent conductive film according to claim 1 , wherein the thiol compound is α-lipoic acid. 3. The transparent conductive film according to claim 1 , wherein the content of the thiol compound having a dithiolane skeleton is 0.1 to 5 parts by weight relative to 100 parts by weight of the polymer constituting the polymer matrix. The transparent conductive film according to claim 1 , wherein the metal nanowires have a fused network structure. The transparent conductive film according to claim 1 , wherein the transparent conductive layer further contains a silane coupling agent. The transparent conductive film according to claim 1 , wherein the transparent conductive layer has a visible light transmittance of 80% or more. 7. The transparent conductive film according to claim 1, wherein the transparent conductive layer has a sheet resistivity of 200 Ω/□ or less.