JP2024067269A - Transparent conductive film laminate, its manufacturing method, and moldable transparent conductive film laminate - Google Patents

Abstract

[Problem] To provide a transparent conductive film laminate suitable for three-dimensional molding having curved surfaces and having good environmental resistance, a manufacturing method thereof, and a moldable transparent conductive film laminate. [Solution] A transparent conductive film laminate obtained by a manufacturing method including a first step of preparing a polycarbonate film having at least one main surface with a static contact angle with water of 60 degrees or more and 75 degrees or less, a second step of applying a conductive ink containing a binder resin and metal nanowires to at least one main surface of the polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less to form a transparent conductive film, and a third step of applying a protective film ink containing a resin component to the transparent conductive film to form a protective film. [Selected Figure] None

Description

The present invention relates to a transparent conductive film laminate, a manufacturing method thereof, and a moldable transparent conductive film laminate. More specifically, the present invention relates to a transparent conductive film laminate that is suitable for three-dimensional processing (three-dimensional molding) and has excellent environmental resistance, a manufacturing method thereof, and a moldable transparent conductive film laminate.

Transparent conductive films are used in various fields such as liquid crystal displays (LCDs), plasma display panels (PDPs), organic electroluminescence displays, transparent electrodes for solar cells (PVs) and touch panels (TPs), antistatic (ESD) films, and electromagnetic shielding (EMI) films. Conventionally, transparent conductive films using ITO (indium tin oxide) have been used, but there are problems such as low indium supply stability, high manufacturing costs, lack of flexibility, and the need for high temperatures during film formation. For this reason, a search for a transparent conductive film to replace ITO is being actively conducted. Among them, a transparent conductive film containing metal nanowires is suitable as an alternative transparent conductive film to ITO because it has excellent conductivity, optical properties, and flexibility, can be formed by a wet process, has low manufacturing costs, and does not require high temperatures during film formation. For example, a transparent conductive film containing silver nanowires and has high conductivity, optical properties, and flexibility is known (see Patent Document 1).

On the other hand, transparent conductive films containing silver nanowires have a problem in that they lack environmental resistance because they have a large surface area per mass of silver and are prone to react with various compounds, and the nanostructures are easily corroded and their conductivity reduced by the effects of various chemicals and cleaning solutions used during the process, and by the effects of oxygen and moisture in the air to which they are exposed during long-term storage. In addition, particularly in applications such as electronic materials, a physical cleaning process using a brush or the like is often used to prevent the adhesion or incorporation of fine particle impurities, dust, and other particles onto the surface of the substrate, but this process can also cause damage to the surface, which is a problem.

To solve this problem, many attempts have been made to laminate a protective film on the surface of a transparent conductive film containing silver nanowires to impart hardness and environmental resistance to the transparent conductive film. In addition, because it is necessary to electrically connect the wiring from the electronic circuit to the transparent conductive film, there is a demand for a protective film that can maintain electrical contact from the protective film surface to the transparent conductive film.

To solve these problems, the following Patent Document 2 discloses a transparent conductive film equipped with a protective film that can provide high environmental resistance to a transparent conductive film containing conductive fibers while maintaining electrical contact with the transparent conductive film, and a method for producing the same.

On the other hand, with the recent widespread use of touch panels and touch pads, the types of devices equipped with them are becoming more diverse, and to further improve the operability of the devices, touch panels and touch pads with three-dimensional shapes, including curved touch surfaces, have been proposed.

For example, Patent Document 1 discloses a capacitive touch panel having a three-dimensional curved touch surface, which is a laminate including at least a transparent base sheet and a main electrode layer having multiple main electrode regions formed on one side of the base sheet using a conductive ink so that the elongation rate of the dried coating is 10% or less and the visible light transmittance is 90% or more, and the laminate is formed into a molded product including a three-dimensional curved surface by drawing when heated and softened.

More specifically, in the method of manufacturing a three-dimensional curved touch panel disclosed in Patent Document 1, first, a main electrode layer having multiple main electrode regions formed using a conductive ink containing an organic conductive material is provided on the surface of a transparent base sheet. Next, an auxiliary electrode layer having auxiliary electrode regions is provided on the main electrode layer by drawing at the locations that will become the peripheral parts of the three-dimensional curved surface. After that, a laminate consisting of these three layers is heated and softened and then drawn to form a three-dimensional curved surface, and then cooled or allowed to cool to obtain a curved molded product. Focusing on the fact that carbon nanotubes or PEDOT, etc. have better extensibility than metal nanofibers, metal nanofibers are used in the main electrode regions that have less extensibility during drawing, and carbon nanotubes or PEDOT, etc. are used in the auxiliary electrode regions that have more extensibility.

Patent Document 2 discloses a thermoformable laminate in which (A) a thermoformable film containing polycarbonate as the main component, (B) an adhesive layer, and (C) a transparent conductive layer are laminated in this order.

Patent document 3 discloses a transparent conductive substrate having a base material, a transparent conductive film formed on at least one of the main surfaces of the base material and containing a binder resin and conductive fibers, and a protective film formed on the transparent conductive film, the binder resin having a thermal decomposition onset temperature of 210°C or higher, and the protective film being a thermosetting film of a thermosetting resin.

Patent Document 4 discloses a transparent conductive film laminate having a transparent substrate made of a transparent thermoplastic resin film, a transparent conductive film formed on at least one main surface of the transparent substrate and containing a binder resin and metal nanowires, and a protective film containing a resin component formed on the transparent conductive film, wherein the binder resin contains at least one of poly-N-vinylacetamide, a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as a monomer unit, and a cellulose-based resin, and 94 mass % or more of the resin component constituting the protective film is derived from a thermoplastic resin.

JP 2013-246741 A JP 2021-70181 A International Publication No. 2018/101334 International Publication No. 2022/138882

However, the conductive ink layer (conductive layer) formed from the conductive ink containing organic conductive materials such as carbon nanotubes or PEDOT used in the manufacturing method of Patent Document 1 has a high resistance value of 50 Ω/□ or more due to the organic material itself, and the conductive layer stretches during deformation, so the resistance value tends to become even higher, which is problematic from an industrial standpoint.

In contrast, a metal layer made of metal has a resistance of 1 Ω/□ or less even in a mesh shape with an opening ratio of 90% or more, which is lower than that of organic conductive materials, and has excellent conductive properties.

On the other hand, when attempting to give a three-dimensional shape using a conductive film having a metal layer formed on a resin substrate by metal plating or metal vapor deposition, the metal layer is often unable to keep up with the expansion of the resin substrate and breaks, making it necessary to take measures such as those disclosed in Patent Document 1.

Patent Document 2 discloses that the (C) transparent conductive layer is composed of a conductive paste or a metal mesh layer, but does not disclose providing a protective film on the (C) transparent conductive layer or the configuration of the protective film suitable for thermoforming.

Patent Document 3 discloses a transparent conductive film equipped with a protective film, but it is not intended to impart a three-dimensional shape, and does not disclose the configuration of a protective film suitable for imparting a three-dimensional shape.

Patent Document 4 discloses a transparent conductive film laminate that can obtain a three-dimensional molded product that has good conductivity and transparency even after three-dimensional molding, and is suitable for molding curved-surface shaped molded products such as curved touch panels, but does not disclose the effect of surface treatment of the transparent substrate on the environmental resistance of the transparent conductive film laminate.

In view of the above, the present invention aims to provide a transparent conductive film laminate that is suitable for three-dimensional molding with curved surfaces and has good environmental resistance, a manufacturing method thereof, and a moldable transparent conductive film laminate.

The inventors conducted extensive research to solve the above problems, and as a result, discovered that a transparent conductive film laminate comprising a transparent substrate made of a transparent thermoplastic resin film, a resin material containing as its main component a thermoplastic resin that exhibits a small increase in resistance value when stretched, a transparent conductive film using as a conductive member silver nanowires that have excellent flexibility, and a protective film containing as its main component a thermoplastic resin, is suitable for three-dimensional molding, and that when forming the transparent conductive film, adjusting the silver nanowire ink-coated surface of the transparent substrate so that it has a static contact angle with water within a specified range is effective in improving the environmental resistance of the transparent conductive film laminate.

The present invention includes the following embodiments:

[1] A transparent conductive film laminate comprising a transparent substrate made of a transparent thermoplastic resin film, a transparent conductive film formed on at least one of the main surfaces of the transparent substrate and comprising a binder resin and metal nanowires, and a protective film containing a resin component formed on the transparent conductive film, wherein the binder resin comprises at least one of poly-N-vinylacetamide, a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as monomer units, and a cellulose-based resin, and the transparent substrate is a polycarbonate film whose main surface on which the transparent conductive film is formed has a static contact angle with water of 60 degrees or more and 75 degrees or less.

[2] The transparent conductive film laminate according to [1], wherein the binder resin is at least one of poly-N-vinylacetamide and a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as monomer units.

[3] The transparent conductive film laminate according to [2], in which the binder resin is poly-N-vinylacetamide.

[4] The transparent conductive film laminate according to any one of [1] to [3], in which the resin component constituting the protective film is derived from a thermoplastic resin containing a carboxyl group-containing polyurethane or ethyl cellulose.

[5] The transparent conductive film laminate according to any one of [1] to [4], wherein the metal nanowires are silver nanowires.

[6] A method for producing a transparent conductive film laminate, comprising: a first step of preparing a polycarbonate film having at least one main surface with a static contact angle with water of 60 degrees or more and 75 degrees or less; a second step of applying a conductive ink containing a binder resin and metal nanowires to at least one main surface of the polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less to form a transparent conductive film; and a third step of applying a protective film ink containing a resin component to the transparent conductive film to form a protective film.

[7] The method for producing a transparent conductive film laminate according to [6], wherein the first step includes a step of subjecting at least one main surface of the polycarbonate film to a corona treatment or plasma treatment.

[8] A moldable transparent conductive film laminate comprising the transparent conductive film laminate according to any one of [1] to [5] and a resin film mainly composed of polycarbonate.

[9] A transparent conductive film laminate according to any one of [1] to [5], in which the ratio ((Ra)) of the sheet resistance value after standing for 1000 hours in an environment of 85°C and 85% RH to the sheet resistance value before standing (Rb) ((Ra/Rb)) is 1.2 or less.

The transparent conductive film laminate of the present invention provides a three-dimensional molded product that has excellent environmental resistance and good conductivity and transparency even after three-dimensional molding, and is suitable for molding curved-surface shaped products such as curved touch panels.

FIG. 2 is a diagram showing a photograph of a substrate surface of a silver nanowire ink coating according to Example 1 observed with a microscope. FIG. 2 is a photograph of a substrate surface of a silver nanowire ink coating according to Comparative Example 1 observed under a microscope.

The following describes the form for implementing the present invention (hereinafter referred to as the embodiment).

The transparent conductive film laminate according to the embodiment has a transparent substrate made of a transparent thermoplastic resin film, a transparent conductive film formed on at least one of the main surfaces of the transparent substrate and containing a binder resin and metal nanowires, and a protective film containing a resin component formed on the transparent conductive film, characterized in that the binder resin contains at least one of poly-N-vinylacetamide, a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as a monomer unit, and a cellulose-based resin, and the transparent substrate is a polycarbonate film whose main surface on which the transparent conductive film is formed has a static contact angle with water of 60 degrees or more and 75 degrees or less. In this specification, "transparent" means that the total light transmittance is 75% or more.

<Transparent substrate>
The transparent substrate may be colored, but the total light transmittance (transparency to visible light) is preferably high, and the total light transmittance is preferably 80% or more. The transparent substrate that can be used is a thermoplastic resin film, and examples of the thermoplastic resin film include polycarbonate films. Polycarbonate films are preferable because they are amorphous thermoplastic resin films that have good moldability in three-dimensional molding. The polycarbonate is not particularly limited as long as it contains a -[O-R-OCO]- unit (wherein R contains an aliphatic group, an aromatic group, or both an aliphatic group and an aromatic group, and further has a linear structure or a branched structure) containing a carbonate bond in the molecular main chain. The thickness of the polycarbonate film is preferably 10 to 500 μm, more preferably 25 to 250 μm, and even more preferably 40 to 150 μm.

Here, the static contact angle with water of the main surface of the polycarbonate film (transparent substrate) on which the transparent conductive film is formed is set to 60 degrees or more and 75 degrees or less. The inventors have found that this improves the environmental resistance of the transparent conductive film laminate according to the embodiment. This is believed to be because by setting the static contact angle with water of the polycarbonate film surface to 60 degrees or more and 75 degrees or less, the compatibility (wettability) of the polycarbonate film with the silver nanowire ink described below is improved, improving the adhesion between the substrate and the silver nanowires and the in-plane uniformity of the silver nanowires. A method for setting the static contact angle with water of the polycarbonate film surface to 60 degrees or more and 75 degrees or less will be described later.

<Transparent conductive film>
Metal nanowires are used as the conductive material that constitutes the transparent conductive film. Metal nanowires are less extensible than carbon nanotubes, but are flexible materials, and are preferable to carbon nanotubes in terms of transparency. It has been confirmed in advance that by using a conductive ink combined with a specific binder resin (poly-N-vinylacetamide (PNVA (registered trademark)) described below), it is possible to form wiring that does not break or cause other problems even when a 15% strain is applied. However, poly-N-vinylacetamide (PNVA (registered trademark)) is hygroscopic, which makes the sheet resistance value of the transparent conductive film unstable, and therefore it is necessary to provide a protective film covering the surface. Metal nanowires are metals whose diameters are on the order of nanometers, and are conductive materials having a wire-like shape. In one embodiment, metal nanotubes, which are conductive materials having a porous or non-porous tubular shape, may be used together with (mixed with) the metal nanowires or in place of the metal nanowires. In this specification, "wire-like" and "tube-like" both mean linear, but the former means one that is not hollow at the center and the latter means one that is hollow at the center, and their properties may be flexible or rigid. In this specification, the former is referred to as "metal nanowires in the narrow sense" and the latter as "metal nanotubes in the narrow sense", and "metal nanowires" includes both metal nanowires in the narrow sense and metal nanotubes in the narrow sense. Metal nanowires in the narrow sense and metal nanotubes in the narrow sense may be used alone or in combination.

The transparent conductive film is formed on a polycarbonate film so that the metal nanowires have intersections, and light can pass through openings where the metal nanowires are not formed. It is preferable that the metal nanowires form a nanostructure network having intersections, and it is more preferable that the metal nanowires form a nanostructure network in which at least some of the intersections are fused. The fact that the intersections of the metal nanowires are fused can be confirmed by analyzing the electron diffraction pattern of a transmission electron microscope (TEM). Specifically, it can be confirmed by analyzing the electron diffraction pattern of a point where the metal nanowires intersect and a metal nanowire sufficiently away from the intersection, and by the fact that the crystal structures of the two are different (the occurrence of recrystallization).

Known manufacturing methods can be used to manufacture metal nanowires. For example, silver nanowires can be synthesized by reducing silver nitrate in the presence of polyvinylpyrrolidone using the polyol method (see Chem. Mater., 2002, 14, 4736). Gold nanowires can also be synthesized by reducing chloroauric acid hydrate in the presence of polyvinylpyrrolidone (see J. Am. Chem. Soc., 2007, 129, 1733). Technologies for large-scale synthesis and purification of silver nanowires and gold nanowires are described in detail in WO 2008/073143 and WO 2008/046058. Gold nanotubes having a porous structure can be synthesized by using silver nanowires as a template and reducing a chloroauric acid solution. The silver nanowires used as the template dissolve into the solution through an oxidation-reduction reaction with chloroauric acid, resulting in the formation of gold nanotubes with a porous structure (see J. Am. Chem. Soc., 2004, 126, 3892-3901).

The average diameter of the metal nanowire is preferably 1 to 500 nm, more preferably 5 to 200 nm, even more preferably 5 to 100 nm, and particularly preferably 10 to 50 nm. The average length of the long axis of the metal nanowire is preferably 1 to 100 μm, more preferably 1 to 80 μm, even more preferably 2 to 70 μm, and particularly preferably 5 to 50 μm. The average diameter and average long axis length of the metal nanowires satisfy the above ranges, and the average aspect ratio is preferably greater than 5, more preferably 10 or more, even more preferably 100 or more, and particularly preferably 200 or more. Here, the aspect ratio is a value calculated by a/b when the average diameter of the metal nanowires is approximated by b and the average long axis length is approximated by a. a and b are measured using a scanning electron microscope (SEM) and an optical microscope. Specifically, b (average diameter) is determined by measuring the dimensions of 100 arbitrarily selected silver nanowires using a field emission scanning electron microscope JSM-7000F (manufactured by JEOL Ltd.) and taking the arithmetic mean value of the measured values. In addition, a (average length) is calculated by measuring the dimensions of 100 arbitrarily selected silver nanowires using a shape measuring laser microscope VK-X200 (manufactured by Keyence Corporation) and taking the arithmetic mean value of the measured values.

Examples of materials for metal nanowires include at least one selected from the group consisting of gold, silver, platinum, copper, nickel, iron, cobalt, zinc, ruthenium, rhodium, palladium, cadmium, osmium, and iridium, as well as alloys combining these metals. In order to obtain a coating film having low sheet resistance and high total light transmittance, it is preferable to include at least one of gold, silver, and copper. Since these metals are highly conductive, when obtaining a certain sheet resistance, the density of the metal on the surface can be reduced, thereby achieving a high total light transmittance. Of these metals, it is more preferable to include at least one of gold and silver, and silver nanowires are most preferable.

The transparent conductive film includes metal nanowires and a binder resin. Generally, a binder resin having transparency and excellent processability can be used. When using metal nanowires manufactured using a polyol method, it is preferable to use a binder resin that is soluble in alcohol, water, or a mixed solvent of alcohol and water from the viewpoint of compatibility with the manufacturing solvent (polyol). In one embodiment, the binder resin includes at least one of poly-N-vinylacetamide (PNVA (registered trademark)), N-vinylacetamide copolymer, and cellulose-based resin. As the binder resin, only one of poly-N-vinylacetamide (PNVA (registered trademark)), N-vinylacetamide copolymer, or cellulose-based resin may be used, or a combination of two or more of these may be used. Only one type of cellulose-based resin described later may be used, but a combination of two or more types may be used. Considering that it is preferable to use a binder resin with high heat resistance from the viewpoint of post-processing, poly-N-vinylacetamide (PNVA (registered trademark)) is more preferable.

Poly-N-vinylacetamide is a homopolymer of N-vinylacetamide (NVA). As the N-vinylacetamide copolymer, a copolymer containing 70 mol% or more of N-vinylacetamide (NVA) as a monomer unit can be used. Examples of monomers copolymerizable with NVA include N-vinylformamide, N-vinylpyrrolidone, acrylic acid, methacrylic acid, sodium acrylate, sodium methacrylate, acrylamide, and acrylonitrile. If the content of the copolymerization component increases, the sheet resistance of the obtained transparent conductive film tends to increase, and the miscibility with the metal nanowires or the adhesion to the substrate tends to decrease, and the heat resistance (thermal decomposition onset temperature) also tends to decrease. Therefore, it is preferable that the monomer unit derived from N-vinylacetamide is contained in the polymer at 70 mol% or more, more preferably 80 mol% or more, and even more preferably 90 mol% or more. The weight average molecular weight of such polymers based on absolute molecular weight is preferably 30,000 to 4,000,000, more preferably 100,000 to 3,000,000, and even more preferably 300,000 to 1,500,000. The absolute molecular weight of poly-N-vinylacetamide and N-vinylacetamide copolymers is measured by the following method.

<Absolute molecular weight measurement>
The binder resin was dissolved in the following eluent and allowed to stand for 20 hours. The concentration of the binder resin in this solution was 0.05% by mass.

This is filtered through a 0.45 μm membrane filter, and the molecular weight of the filtrate is measured by GPC-MALS to calculate the weight average molecular weight based on the absolute molecular weight.
GPC: Shodex (registered trademark) SYSTEM 21 manufactured by Showa Denko K.K.
Column: TSKgel (registered trademark) G6000PW manufactured by Tosoh Corporation
Column temperature: 40°C
Eluent: 0.1 mol/L NaH2PO4 aqueous solution + 0.1 mol/L Na2HPO4 aqueous solution Flow rate: 0.64 mL/min
Sample injection volume: 100 μL
MALS detector: Wyatt Technology Corporation, DAWN (registered trademark) DSP
Laser wavelength: 633 nm
Multi-angle fit method: Berry method

Cellulose resins are linear polymers consisting of six-membered ether rings covalently bonded by so-called glycosidic bonds, which contain ether groups. Although cellulose itself does not dissolve in water, alcohol, or a mixed solvent of alcohol and water, some modified cellulose derivatives dissolve in water, alcohol, or a mixed solvent of alcohol and water. The cellulose resin is not particularly limited as long as it dissolves in water, alcohol, or a mixed solvent of alcohol and water, but cellulose ethers can be used. Examples of cellulose ethers include alkyl celluloses (e.g., C1-4 alkyl celluloses such as methyl cellulose and ethyl cellulose), hydroxyalkyl celluloses (e.g., hydroxy C1-4 alkyl celluloses such as hydroxymethyl cellulose, hydroxyethyl cellulose, and hydroxypropyl cellulose), hydroxyalkyl alkyl celluloses (e.g., hydroxy C2-4 alkyl C1-4 alkyl celluloses such as hydroxypropyl methyl cellulose), carboxyalkyl celluloses (e.g., carboxymethyl cellulose), and alkyl-carboxyalkyl celluloses (e.g., methyl carboxymethyl cellulose). These can be used alone or in combination of two or more. Among these, it is preferable to use methyl cellulose or ethyl cellulose from the viewpoints of solubility in the solvent and environmental resistance (moisture resistance). The weight average molecular weight of the cellulose-based resin is preferably 100,000 to 200,000. In this disclosure, the weight average molecular weight of the cellulose-based resin is a polyethylene oxide equivalent value measured by gel permeation chromatography (hereinafter referred to as GPC).

The transparent conductive film can be formed by applying, by printing or the like, a conductive ink containing the metal nanowires, a binder resin, and a solvent onto at least one of the main surfaces of a polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less, and then drying and removing the solvent.

The solvent is not particularly limited as long as it disperses the metal nanowires well and dissolves the binder resin but does not dissolve the polycarbonate film. When using metal nanowires synthesized by the polyol method, it is preferable to use alcohol, water, or a mixed solvent of alcohol and water from the viewpoint of compatibility with the manufacturing solvent (polyol). It is more preferable to use a mixed solvent of alcohol and water because the drying speed of the binder resin can be easily controlled. The alcohol preferably contains at least one saturated monohydric alcohol (methanol, ethanol, normal propanol, and isopropanol) having 1 to 3 carbon atoms represented by CnH2n+1OH (n is an integer of 1 to 3) [hereinafter simply referred to as "saturated monohydric alcohol having 1 to 3 carbon atoms". ], and it is more preferable that the saturated monohydric alcohol having 1 to 3 carbon atoms accounts for 40 mass% or more of the total alcohol. Using a saturated monohydric alcohol having 1 to 3 carbon atoms is advantageous in terms of the process because it makes it easier to dry the solvent. As the alcohol, an alcohol other than a saturated monohydric alcohol having 1 to 3 carbon atoms can be used in combination. Examples of alcohols other than saturated monohydric alcohols having 1 to 3 carbon atoms that can be used in combination include ethylene glycol, propylene glycol, ethylene glycol monomethyl ether, ethylene glycol monoethyl ether, propylene glycol monomethyl ether, and propylene glycol monoethyl ether. By using these alcohols in combination with saturated monohydric alcohols having 1 to 3 carbon atoms, the drying speed of the solvent can be adjusted. The total alcohol content in the mixed solvent is preferably 5 to 90% by mass. If the alcohol content in the mixed solvent is less than 5% by mass or more than 90% by mass, stripes (coating spots) may occur during coating.

The conductive ink can be produced by mixing and stirring the binder resin, metal nanowires and solvent using a planetary stirrer or the like. The content of the binder resin contained in the conductive ink is preferably in the range of 0.01 to 1.0 mass%. The content of the metal nanowires contained in the conductive ink is preferably in the range of 0.01 to 1.0 mass%. The content of the solvent contained in the conductive ink is preferably in the range of 98.0 to 99.98 mass%.

The conductive ink can be printed by a bar coating method, a spin coating method, a spray coating method, a gravure method, a slit coating method, or the like. The shape of the printed film or pattern formed by printing is not particularly limited, but examples include the shape of a wiring or electrode pattern formed on a polycarbonate film, or the shape of a film (solid pattern) covering the entire surface or a part of the surface of a polycarbonate film. The formed pattern becomes conductive by heating to dry the solvent. The dry thickness of the transparent conductive film varies depending on the diameter of the metal nanowires used, the desired sheet resistance value, and the like, but is preferably 10 to 300 nm, and more preferably 30 to 200 nm. If the dry thickness of the transparent conductive film is 10 nm or more, the number of intersections of the metal nanowires increases, and good conductivity can be obtained. If the dry thickness of the transparent conductive film is 300 nm or less, light is easily transmitted and reflection by the metal nanowires is suppressed, and good optical properties can be obtained. If necessary, the conductive pattern may be irradiated with appropriate light.

<Protective film>
In general, the protective film for protecting the transparent conductive film is preferably formed from a cured film of a curable resin composition from the viewpoint of mechanically protecting the transparent conductive film. However, the cured film is not preferable as a protective film used in three-dimensional molding because it does not have excellent moldability. Although it depends on the final application form, for example, when applied to a touch panel, the transparent conductive film laminate is usually used by being stuck to other members, that is, it is mechanically protected by other members. In that case, high mechanical strength is not required for the transparent conductive film laminate itself. Therefore, the protective film containing the resin component constituting the transparent conductive film laminate of one embodiment is mainly composed of a thermoplastic resin having excellent moldability. In other words, 94% by mass or more of the resin component constituting the protective film is derived from a thermoplastic resin. As described later, the protective film is formed by applying a resin composition obtained by dissolving a resin in a solvent onto the transparent conductive film. Therefore, when 94% by mass or more of the resin component constituting the protective film is derived from a thermoplastic resin, it means that 94% by mass or more of the resin component contained in the resin composition used to form the protective film is a thermoplastic resin. It is necessary to use a resin composition that can dissolve a resin component in a solvent that does not damage the binder resin and polycarbonate film of the transparent conductive film and can be applied well to the transparent conductive film, and can form a film on the transparent conductive film. Examples of applicable resin compositions include resin compositions containing ethyl cellulose and polyurethane having a carboxy group. Examples of resin compositions containing ethyl cellulose include ETHOCEL (registered trademark) STD-100 (manufactured by Dow Chemical (USA), ethyl cellulose, weight average molecular weight: 180,000, molecular weight distribution (Mw/Mn) = 3.0 [catalog value]). The polyurethane containing a carboxy group preferably has a weight average molecular weight of 1,000 to 100,000, more preferably 3,000 to 85,000, even more preferably 5,000 to 70,000, and particularly preferably 10,000 to 65,000. In this specification, the weight average molecular weight of the polyurethane containing a carboxy group is a value measured by GPC in terms of polystyrene. If the weight average molecular weight of the carboxyl group-containing polyurethane is less than 1,000, the elongation, flexibility and strength of the coating film may be impaired. If it exceeds 100,000, the solubility of the polyurethane in a solvent may be reduced and, even if it is dissolved, the viscosity may become too high, resulting in significant limitations in terms of use.

In this specification, unless otherwise specified, the GPC measurement conditions for the weight average molecular weight of a carboxy group-containing polyurethane are as follows.
Device name: JASCO Corporation HPLC unit HSS-2000
Column: Shodex column LF-804
Mobile phase: tetrahydrofuran Flow rate: 1.0 mL/min
Detector: JASCO Corporation RI-2031Plus
Temperature: 40.0°C
Sample volume: Sample loop 100 μL
Sample concentration: about 0.1% by mass

The acid value of the polyurethane containing carboxy groups is preferably 10 to 140 mg-KOH/g, and more preferably 15 to 130 mg-KOH/g. If the acid value of the polyurethane containing carboxy groups is 10 mg-KOH/g or more, the solvent resistance of the protective film is good, and the curing properties of the resin composition when a small amount of a curing component is used in combination are also good. If the acid value of the polyurethane containing carboxy groups is 140 mg-KOH/g or less, the solubility of the polyurethane resin in a solvent is good, and the viscosity of the resin composition can be easily adjusted to the desired viscosity.

In this specification, the acid value of a polyurethane containing a carboxy group is a value measured by the following method.

Weigh out approximately 0.2 g of sample using a precision balance into a 100 ml Erlenmeyer flask, then add 10 ml of a mixed solvent of ethanol/toluene = 1/2 (mass ratio) to dissolve it. Then, add 1 to 3 drops of phenolphthalein ethanol solution as an indicator to the container, and stir thoroughly until the sample becomes homogenous. Titrate this with 0.1 N potassium hydroxide-ethanol solution, and the neutralization endpoint is when the indicator remains slightly red for 30 seconds.

The value obtained using the following formula is the acid value of the polyurethane containing a carboxy group.
Acid value (mg-KOH/g) = [B x f x 5.611] / S
B: Amount of 0.1N potassium hydroxide-ethanol solution used (mL)
f: Factor of 0.1N potassium hydroxide-ethanol solution S: Amount of sample taken (g)

More specifically, polyurethane containing a carboxy group is a polyurethane synthesized using (a1) a polyisocyanate compound, (a2) a polyol compound, and (a3) a dihydroxy compound having a carboxy group as monomers. From the viewpoint of light resistance and weather resistance, it is desirable that (a1), (a2), and (a3) do not contain functional groups having conjugation such as aromatic compounds. Each monomer will be described in more detail below.

(a1) Polyisocyanate Compound As the (a1) polyisocyanate compound, a diisocyanate having two isocyanato groups per molecule is usually used. As the polyisocyanate compound, for example, an aliphatic polyisocyanate or an alicyclic polyisocyanate can be used alone or in combination of two or more. A small amount of polyisocyanate having three or more isocyanato groups can also be used as long as the polyurethane containing a carboxy group does not gel.

Examples of aliphatic polyisocyanates include 1,3-trimethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,9-nonamethylene diisocyanate, 1,10-decamethylene diisocyanate, 2,2,4-trimethylhexamethylene diisocyanate, 2,4,4-trimethylhexamethylene diisocyanate, lysine diisocyanate, 2,2'-diethyl ether diisocyanate, and dimer acid diisocyanate.

Examples of alicyclic polyisocyanates include 1,4-cyclohexane diisocyanate, 1,3-bis(isocyanatomethyl)cyclohexane, 1,4-bis(isocyanatomethyl)cyclohexane, 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (IPDI, isophorone diisocyanate), bis-(4-isocyanatocyclohexyl)methane (hydrogenated MDI), hydrogenated (1,3- or 1,4-)xylylene diisocyanate, and norbornane diisocyanate.

(a1) By using an alicyclic compound in which the number of carbon atoms other than the carbon atoms in the isocyanato group (-NCO group) is 6 to 30 as the polyisocyanate compound, it is possible to obtain a protective film that is highly reliable at high temperatures and high humidity and is suitable for electronic device components. Among the alicyclic polyisocyanates listed above, 1,4-cyclohexane diisocyanate, isophorone diisocyanate, bis-(4-isocyanatocyclohexyl)methane, 1,3-bis(isocyanatomethyl)cyclohexane, and 1,4-bis(isocyanatomethyl)cyclohexane are preferred.

As described above, from the viewpoint of weather resistance and light resistance, it is preferable to use a compound that does not have an aromatic ring as the (a1) polyisocyanate compound. Therefore, when an aromatic polyisocyanate or an aromatic aliphatic polyisocyanate is used as necessary, the content of these is preferably 50 mol% or less, more preferably 30 mol% or less, and even more preferably 10 mol% or less, based on the total amount (100 mol%) of the (a1) polyisocyanate compound.

(a2) Polyol Compound The (a2) polyol compound (however, the (a2) polyol compound does not include the (a3) dihydroxy compound having a carboxy group described below) has a number average molecular weight of usually 250 to 50,000, preferably 400 to 10,000, and more preferably 500 to 5,000. The number average molecular weight of the polyol compound is a polystyrene-equivalent value measured by GPC under the above-mentioned conditions.

Examples of the (a2) polyol compound include polycarbonate polyol, polyether polyol, polyester polyol, polylactone polyol, polysilicone with hydroxyl groups at both ends, and polyol compounds having 18 to 72 carbon atoms obtained by hydrogenating polyvalent carboxylic acids derived from C18 (18 carbon atoms) unsaturated fatty acids and their polymers made from vegetable fats and oils to convert the carboxylic acids to hydroxyl groups. From the viewpoint of the balance between the water resistance, insulation reliability, and adhesion to the substrate of the protective film, it is preferable that the (a2) polyol compound is a polycarbonate polyol.

Polycarbonate polyol can be obtained by reacting a diol having 3 to 18 carbon atoms with a carbonate ester or phosgene, and is represented, for example, by the following structural formula (1).

In formula (1), R ³ is a residue obtained by removing a hydroxyl group from the corresponding diol (HO-R ³ -OH), which is an alkylene group having 3 to 18 carbon atoms; n ₃ is a positive integer, preferably 2-50.

Specifically, the polycarbonate polyol represented by formula (1) can be produced by using 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decamethylene glycol, or 1,2-tetradecanediol as a raw material.

The polycarbonate polyol may be a polycarbonate polyol (copolymer polycarbonate polyol) having multiple types of alkanediyl groups in its skeleton. The use of a copolymer polycarbonate polyol is often advantageous from the viewpoint of preventing crystallization of polyurethane containing carboxy groups. In consideration of solubility in a solvent, it is preferable to use a polycarbonate polyol having a branched skeleton and a hydroxyl group at the end of the branched chain.

As long as the effects of the present invention are not impaired, (a2) the polyol compound may be a diol having a molecular weight of 300 or less, which is typically used as a diol component in synthesizing polyesters or polycarbonates. Examples of such low molecular weight diols include ethylene glycol, 1,2-propanediol, 1,3-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol, 1,5-pentanediol, 1,6-hexanediol, 3-methyl-1,5-pentanediol, 1,8-octanediol, 1,3-cyclohexanedimethanol, 1,4-cyclohexanedimethanol, 1,9-nonanediol, 2-methyl-1,8-octanediol, 1,10-decamethylene glycol, 1,2-tetradecanediol, 2,4-diethyl-1,5-pentanediol, butylethylpropanediol, 1,3-cyclohexanedimethanol, diethylene glycol, triethylene glycol, and dipropylene glycol.

(a3) Dihydroxy Compound Containing a Carboxy Group As the (a3) dihydroxy compound containing a carboxy group, a carboxylic acid or aminocarboxylic acid having two of either a hydroxy group or a hydroxyalkyl group having 1 or 2 carbon atoms and a molecular weight of 200 or less is preferable in terms of being able to control the crosslinking points. (a3) Dihydroxy Compounds Containing a Carboxy Group include, for example, 2,2-dimethylolpropionic acid, 2,2-dimethylolbutanoic acid, N,N-bishydroxyethylglycine, and N,N-bishydroxyethylalanine, and among these, 2,2-dimethylolpropionic acid and 2,2-dimethylolbutanoic acid are preferred because of their high solubility in solvents. (a3) Dihydroxy Compounds Containing a Carboxy Group may be used alone or in combination of two or more.

Carboxy group-containing polyurethane can be synthesized from only the above three components ((a1), (a2) and (a3)). It can also be synthesized by reacting (a4) a monohydroxy compound and/or (a5) a monoisocyanate compound. From the viewpoint of light resistance, it is preferable that (a4) a monohydroxy compound and (a5) a monoisocyanate compound are compounds that do not contain an aromatic ring or a carbon-carbon double bond in the molecule.

Carboxylic acid-containing polyurethane can be synthesized by reacting the above-mentioned (a1) polyisocyanate compound, (a2) polyol compound, and (a3) dihydroxy compound having a carboxyl group in an appropriate organic solvent in the presence or absence of a known urethane catalyst such as dibutyltin dilaurate. It is advantageous to react the carboxylic acid-containing polyurethane without a catalyst because there is no need to consider the final contamination with tin, etc.

The organic solvent is not particularly limited as long as it has low reactivity with the isocyanate compound. The organic solvent is preferably a solvent that does not contain a basic functional group such as an amine and has a boiling point of 50°C or higher, preferably 80°C or higher, and more preferably 100°C or higher. Examples of such solvents include toluene, xylene, ethylbenzene, nitrobenzene, cyclohexane, isophorone, diethylene glycol dimethyl ether, ethylene glycol diethyl ether, ethylene glycol monomethyl ether acetate, propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, methyl methoxypropionate, ethyl methoxypropionate, methyl ethoxypropionate, ethyl ethoxypropionate, ethyl acetate, n-butyl acetate, isoamyl acetate, ethyl lactate, acetone, methyl ethyl ketone, cyclohexanone, N,N-dimethylformamide, N,N-dimethylacetamide, N-methylpyrrolidone, γ-butyrolactone, and dimethyl sulfoxide.

Considering that organic solvents with low solubility for the resulting polyurethane are not preferred, and that polyurethane is used as a raw material for protective film inks in electronic material applications, the organic solvent is preferably propylene glycol monomethyl ether acetate, propylene glycol monoethyl ether acetate, dipropylene glycol monomethyl ether acetate, diethylene glycol monoethyl ether acetate, γ-butyrolactone, or a combination thereof.

There are no particular restrictions on the order in which the raw materials are added, but typically (a2) the polyol compound and (a3) the dihydroxy compound having a carboxy group are added to the reaction vessel first, and after dissolving or dispersing them in a solvent, (a1) the polyisocyanate compound is added dropwise at 20 to 150°C, more preferably 60 to 120°C, and then these are reacted at 30 to 160°C, more preferably 50 to 130°C.

The molar ratio of the raw materials is adjusted according to the molecular weight and acid value of the desired polyurethane.

Specifically, the molar ratio of the isocyanato groups of (a1) the polyisocyanate compound: (hydroxyl groups of (a2) the polyol compound + hydroxyl groups of (a3) the dihydroxy compound having a carboxy group) is preferably 0.5 to 1.5:1, preferably 0.8 to 1.2:1, and more preferably 0.95 to 1.05:1.

The molar ratio of the hydroxyl groups of (a2) the polyol compound to the hydroxyl groups of (a3) the dihydroxy compound having a carboxy group is preferably 1:0.1-30, more preferably 1:0.3-10.

As described above, 94% by mass or more of the resin components constituting the protective film are derived from thermoplastic resins. 6% by mass or less of the resin components constituting the protective film may be derived from curable resins (compounds). If the amount of curable resins (compounds) in the resin components in the resin composition is in the range of 6% by mass or less, the function as a protective film can be improved without causing a significant decrease in three-dimensional molding processability. Suitable curable resins (compounds) that can be used in combination with thermoplastic resins include epoxy resins (compounds) having two or more epoxy groups in one molecule.

When forming the protective film, the thermoplastic resin and the thermosetting resin may react with each other. For example, when a polyurethane containing a carboxy group is used as the thermoplastic resin and an epoxy resin is used as the thermosetting resin, the carboxy group of the polyurethane may react with the epoxy group of the epoxy resin to form a polyurethane-epoxy resin complex. In this specification, "94% by mass or more of the resin components constituting the protective film are derived from a thermoplastic resin" means that the thermoplastic resin used to form the protective film, for example, a polyurethane containing a carboxy group, corresponds to 94% by mass or more of the resin components of the protective film, and the thermosetting resin used to form the protective film, for example, an epoxy resin having two or more epoxy groups in one molecule, corresponds to 6% by mass or less of the resin components of the protective film. When the resin components forming the protective film are derived from a polyurethane containing a carboxy group and an epoxy resin having two or more epoxy groups in one molecule, the content of the epoxy resin having two or more epoxy groups in one molecule is more than 0% by mass and 6% by mass or less of the resin components.

Epoxy resins (compounds) having two or more epoxy groups in one molecule include, for example, bisphenol A type epoxy compounds, hydrogenated bisphenol A type epoxy resins, bisphenol F type epoxy resins, novolac type epoxy resins, phenol novolac type epoxy resins, cresol novolac type epoxy resins, N-glycidyl type epoxy resins, bisphenol A novolac type epoxy resins, chelate type epoxy resins, glyoxal type epoxy resins, amino group-containing epoxy resins, rubber-modified epoxy resins, dicyclopentadiene phenolic type epoxy resins, silicone-modified epoxy resins, ε-caprolactone-modified epoxy resins, aliphatic type epoxy resins containing glycidyl groups, and alicyclic epoxy resins containing glycidyl groups.

Epoxy compounds having three or more epoxy groups in one molecule can be used more preferably. Examples of such epoxy compounds include EHPE (registered trademark) 3150 (manufactured by Daicel Corporation), jER (registered trademark) 604 (manufactured by Mitsubishi Chemical Corporation), EPICLON (registered trademark) EXA-4700 (manufactured by DIC Corporation), EPICLON (registered trademark) HP-7200 (manufactured by DIC Corporation), pentaerythritol tetraglycidyl ether, pentaerythritol triglycidyl ether, and TEPIC (registered trademark)-S (manufactured by Nissan Chemical Industries, Ltd.).

The blending ratio of the epoxy resin (compound) and the polyurethane containing a carboxy group is preferably such that the molar ratio (Ep/COOH) of the epoxy group (Ep) of the epoxy resin to the carboxy group (COOH) of the polyurethane containing a carboxy group is greater than 0 and is 0.02 or less.

When an epoxy resin (compound) is used in combination with a polyurethane containing a carboxyl group, a curing accelerator can be further blended in the resin composition. Specific examples of the curing accelerator include phosphine-based compounds such as triphenylphosphine and tributylphosphine (manufactured by Hokko Chemical Industry Co., Ltd.), Curazol (registered trademark) (imidazole-based epoxy resin curing agent: manufactured by Shikoku Kasei Co., Ltd.), 2-phenyl-4-methyl-5-hydroxymethylimidazole, U-CAT (registered trademark) SA series (DBU salt: manufactured by San-Apro Co., Ltd.), and Irgacure (registered trademark) 184. The amount of the curing accelerator used is preferably 20 to 80 parts by mass, more preferably 30 to 70 parts by mass, and even more preferably 40 to 60 parts by mass, per 100 parts by mass of the epoxy resin (compound). The curing accelerator is included in the resin component that is not a thermoplastic resin.

A curing aid may be used in combination. Examples of the curing aid include polyfunctional thiol compounds and oxetane compounds. Examples of the polyfunctional thiol compounds include pentaerythritol tetrakis (3-mercaptopropionate), tris-[(3-mercaptopropionyloxy)-ethyl]-isocyanurate, trimethylolpropane tris(3-mercaptopropionate), and Karenz (registered trademark) MT series (manufactured by Showa Denko K.K.). Examples of the oxetane compounds include Aron Oxetane (registered trademark) series (manufactured by Toa Gosei Co., Ltd.), ETERNACOLL (registered trademark) OXBP, and OXMA (manufactured by Ube Industries, Ltd.). The amount of the curing aid used is preferably 0.1 to 10 parts by mass, more preferably 0.5 to 6 parts by mass, per 100 parts by mass of the epoxy resin (compound), so that the effect of adding the aid can be obtained, an excessive increase in the curing rate can be avoided, and handling properties can be maintained. The curing aid is also included in the resin component that is not a thermoplastic resin.

The resin composition preferably contains 95.0% by mass or more and 99.9% by mass or less of the solvent, more preferably 96% by mass or more and 99.7% by mass or less, and even more preferably 97% by mass or more and 99.5% by mass or less. As the solvent, one that does not damage the transparent conductive film or the polycarbonate film can be used. The solvent used in the synthesis of the polyurethane containing a carboxy group can be used as it is, or another solvent can be used to adjust the solubility or printability of the binder resin. When using another solvent, the solvent used in the synthesis of the polyurethane containing a carboxy group may be distilled off before or after adding a new solvent to replace the solvent. Considering the complexity of the operation and the energy cost, it is preferable to use at least a part of the solvent used in the synthesis of the polyurethane containing a carboxy group as it is. Considering the stability of the resin composition, the boiling point of the solvent is preferably 80°C to 300°C, more preferably 80°C to 250°C. If the boiling point of the solvent is less than 80°C, it will dry out easily during printing, and uneven application will occur. If the boiling point of the solvent is higher than 300°C, it will require a long heating process at high temperature during drying and curing, making it unsuitable for industrial production.

Solvents include solvents used in polyurethane synthesis such as propylene glycol monomethyl ether acetate (boiling point 146°C), γ-butyrolactone (boiling point 204°C), diethylene glycol monoethyl ether acetate (boiling point 218°C), and tripropylene glycol dimethyl ether (boiling point 243°C); ether-based solvents such as propylene glycol dimethyl ether (boiling point 97°C) and diethylene glycol dimethyl ether (boiling point 162°C); isopropyl alcohol (boiling point 82°C), t-butyl alcohol (boiling point 82°C), and 1-Hexanol (boiling point 157°C), propylene glycol monomethyl ether (boiling point 120°C), diethylene glycol monomethyl ether (boiling point 194°C), diethylene glycol monoethyl ether (boiling point 196°C), diethylene glycol monobutyl ether (boiling point 230°C), triethylene glycol (boiling point 276°C), ethyl lactate (boiling point 154°C), and other hydroxyl group-containing solvents; ketone-based solvents such as methyl ethyl ketone (boiling point 80°C); or ester-based solvents such as ethyl acetate (boiling point 77°C). These solvents can be used alone or in combination of two or more. When two or more types are mixed, in addition to the solvent used in the synthesis of the polyurethane containing a carboxy group, it is preferable to use in combination a solvent having a hydroxyl group and a boiling point of more than 100°C, which does not cause aggregation or precipitation, or a solvent having a boiling point of 100°C or less, in terms of the drying property of the ink, taking into consideration the solubility of the polyurethane, epoxy resin, and the like used. Solvents that corrode transparent conductive films or polycarbonate films when used alone can also be used if they are mixed with other solvents to create a composition that does not corrode transparent conductive films or polycarbonate films.

The resin composition can be produced by mixing a mixture of polyurethane containing a carboxy group, an epoxy compound, and a curing accelerator and/or curing aid as necessary, adding a solvent so that the solvent content in the resin composition is 95.0% by mass or more and 99.9% by mass or less, and stirring these components until they are uniform.

The solids concentration in the resin composition varies depending on the desired film thickness and printing method, but is preferably 0.1 to 10% by mass, and more preferably 0.5 to 5% by mass. If the solids concentration is in the range of 0.1 to 10% by mass, the film thickness does not become excessively thick when the resin composition is applied onto a transparent conductive film, and a state in which electrical contact with the transparent conductive film can be maintained can be maintained, and weather resistance and light resistance can be imparted to the protective film.

The above-mentioned resin composition is applied onto a transparent conductive film by printing such as bar coat printing, gravure printing, inkjet printing, and slit coating, and the solvent is then dried and removed to form a protective film. The thickness of the protective film is usually more than 100 nm and less than 1 μm. The thickness of the protective film is preferably more than 100 nm and less than 500 nm, more preferably more than 100 nm and less than 200 nm, even more preferably more than 100 nm and less than 150 nm, and particularly preferably more than 100 nm and less than 120 nm. If the thickness of the protective film exceeds 1 μm, it becomes difficult to obtain electrical continuity between the wiring and the transparent conductive film in a later process.

As described above, the transparent conductive film laminate obtained by sequentially forming a transparent conductive film (e.g., a silver nanowire layer) and a protective film on a polycarbonate film has excellent three-dimensional processability. As a three-dimensional processing method for a transparent conductive film laminate, various known methods such as vacuum forming, blow molding, free blow molding, pressure forming, vacuum pressure forming, and heat press molding can be mentioned. Regardless of the method used, stress is applied to the three-dimensionally processed transparent conductive film laminate, causing distortion. The transparent conductive film laminate is stretched due to this distortion. In a transparent conductive film laminate with low three-dimensional processability, breakage of the transparent conductive film constituting the transparent conductive film laminate or a significant increase in the sheet resistance value is usually observed at low stress (low stretch ratio). On the other hand, in a transparent conductive film laminate with good three-dimensional processability, breakage of the transparent conductive film does not occur or the increase in the sheet resistance value is small up to high stress (high stretch ratio). Therefore, the three-dimensional processability of the transparent conductive film laminate can be evaluated by performing a tensile test on the transparent conductive film laminate and measuring the change in the sheet resistance value. As shown in the examples below, in one embodiment of the transparent conductive film laminate, the ratio (R/R0) of the sheet resistance value (R) after applying 15% strain to the sheet resistance value (R0) before applying strain is 25 or less, which is favorable. This is thought to be because the use of a protective film in which 94 mass % or more of the resin component is a thermoplastic resin makes it difficult for cracks to occur in the protective film even when strain is applied, and prevents cracks in the protective film from propagating to the transparent conductive film and impairing its conductivity. From the viewpoint of three-dimensional processability, it is preferable that the protective film does not contain a curing component (epoxy compound, curing accelerator, etc.).

The manufacturing method of the transparent conductive film laminate according to the embodiment is characterized by including a first step of preparing a polycarbonate film having at least one main surface with a static contact angle with water of 60 degrees or more and 75 degrees or less, a second step of applying a conductive ink containing a binder resin and metal nanowires to at least one main surface of the polycarbonate film with a static contact angle with water of 60 degrees or more and 75 degrees or less to form a transparent conductive film, and a third step of applying a protective film ink containing a resin component to the transparent conductive film to form a protective film.

Here, the method for making the static contact angle with water 60 degrees or more and 75 degrees or less in the first step is not particularly limited, and a known surface treatment method for hydrophilizing the surface of a substrate (resin film) can be applied. For example, corona treatment and plasma treatment can be mentioned. It is known that the surface of a polycarbonate film, which is a transparent substrate, can be hydrophilized by these methods, but it was not known that making the static contact angle with water of the surface (main surface) of the polycarbonate film 60 degrees or more and 75 degrees or less is effective in improving the environmental resistance of a transparent conductive film laminate in which a transparent conductive film composed of a binder resin and metal nanowires and a protective film containing a resin component are sequentially laminated on the main surface of the polycarbonate film. The present inventor has found that in order to improve the environmental resistance of the transparent conductive film laminate of the above configuration, it is effective for the static contact angle with water of the main surface of the polycarbonate film, to which a conductive ink containing a binder resin and metal nanowires is applied, to be stably in the range of 60 degrees or more and 75 degrees or less. Here, the static contact angle being stable in the range of 60 degrees or more and 75 degrees or less means that the change in the static contact angle over time is small and the range of 60 degrees or more and 75 degrees or less is stably maintained. If the static contact angle is less than 60 degrees, it is presumed that the hydrophilicity of the main surface of the polycarbonate film is too high and it is prone to absorb water, which may result in a decrease in the conductivity of the transparent conductive film. If the static contact angle is more than 75 degrees, it is presumed that the wettability of the conductive ink containing metal nanowires to the main surface of the polycarbonate film is insufficient, resulting in insufficient adhesion at the interface between the polycarbonate film and the conductive ink, which may allow moisture to easily penetrate into the gaps and may result in a decrease in the conductivity of the transparent conductive film.

One example of surface treatment conditions that will keep the static contact angle of the main surface of a polycarbonate film with water in a stable range of 60 degrees or more and 75 degrees or less is to treat the surface of the polycarbonate film using a commercially available corona discharge surface treatment device (CTW-0212 (manufactured by Wedge Corporation)) at an irradiation output of 0.3 to 0.5 kW and a speed of 1 to 10 m/min, followed by curing in an atmosphere of 25 to 50% RH for 24 hours or more. According to the study by the present inventor, the static contact angle of the surface of the polycarbonate film immediately after the corona discharge surface treatment is reduced to about 50 degrees or less, but then rises and is in an unstable state, and the degree of increase in the static contact angle is large immediately after the static contact angle is reduced to about 50 degrees or less after the surface treatment, and the degree of increase in the static contact angle gradually becomes gentler with the passage of time, and it becomes about 60° after 1 day (24 hours) and about 70° after 7 days (168 hours), and thereafter the change over time is small, and the static contact angle tends to stabilize (the change in the static contact angle is saturated). In addition, there is almost no difference in optical properties and tensile properties between the transparent conductive film laminate (the former) in which the conductive ink is applied in a state in which the static contact angle is unstable immediately after the surface treatment of the polycarbonate film and the transparent conductive film laminate (the latter) in which the conductive ink is applied in a state in which the static contact angle is stable, but the former has a larger sheet resistance value and in-plane sheet resistance variation, and the environmental resistance tends to clearly decrease. Applying conductive ink to the polycarbonate film surface after surface treatment while the static contact angle is stable at 60 degrees or more and 75 degrees or less is effective in obtaining a transparent conductive film laminate with good environmental resistance.

In the second step, the transparent conductive film is formed by heating a conductive ink applied to at least one main surface of a polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less to dry the solvent.
In the third step, the protective film is formed by applying the resin composition (ink for protective film) onto the transparent conductive film, and drying and removing the solvent.

The transparent conductive film laminate according to another embodiment includes an embodiment as a moldable laminate (moldable transparent conductive film laminate) laminated with a substrate (front plate) containing a thermoplastic resin. A substrate (front plate) containing a thermoplastic resin is laminated on the transparent conductive film laminate described above for protection, decoration, and retention of the shaped shape of the transparent conductive film laminate. The type of thermoplastic resin constituting the substrate is not particularly limited as long as it is transparent, but various resins such as polycarbonate (PC) resin, acrylic resin, polyethylene terephthalate (PET), triacetyl cellulose (TAC), polyethylene naphthalate (PEN), thermoplastic polyimide (PI), cycloolefin polymer (COP), cycloolefin copolymer (COC), polyethersulfone, and cellophane are used. Of these options, it is preferable that the thermoplastic resin of the substrate contains at least a polycarbonate resin. The thickness of the substrate (front plate) is preferably in the range of 0.5 to 3.0 mm, more preferably in the range of 0.6 to 2.5 mm, and even more preferably in the range of 0.8 to 2.0 mm. If it is within the range of 0.5 to 3.0 mm, it can be shaped without any problems and the shape after shaping can be maintained.

The type of polycarbonate resin contained in the substrate is not particularly limited as long as it contains a -[O-R-OCO]- unit (where R contains an aliphatic group, an aromatic group, or both an aliphatic group and an aromatic group, and further has a linear or branched structure) containing a carbonate bond in the molecular main chain, but polycarbonates having a bisphenol skeleton are preferred, and polycarbonates having a bisphenol A skeleton or a bisphenol C skeleton are particularly preferred. As the polycarbonate resin, a mixture or copolymer of bisphenol A and bisphenol C may be used. The hardness of the substrate can be improved by using a bisphenol C-based polycarbonate resin, for example, a polycarbonate resin containing only bisphenol C, or a mixture or copolymer of bisphenol C and bisphenol A. In addition, the viscosity average molecular weight of the polycarbonate resin is preferably 15,000 to 40,000, more preferably 20,000 to 35,000, and even more preferably 22,500 to 25,000. It is preferable to use the same polycarbonate as the transparent substrate that constitutes the transparent conductive film laminate described above.

The acrylic resin contained in the substrate is not particularly limited, but examples thereof include homopolymers (PMMA, etc.) of various (meth)acrylic acid esters such as methyl methacrylate (MMA), or copolymers of MMA and one or more other monomers, and further includes mixtures of multiple types of these resins. Among these, (meth)acrylates containing a cyclic alkyl structure, which have low birefringence, low moisture absorption, and excellent heat resistance, are preferred. Examples of such acrylic resins include, but are not limited to, ACRYPET (registered trademark, manufactured by Mitsubishi Chemical Corporation), DELPET (registered trademark, manufactured by Asahi Kasei Corporation), and PARAPET (registered trademark, manufactured by Kuraray Co., Ltd.).

The substrate may be a two-layered product containing polycarbonate resin and the above-mentioned acrylic resin. By using a two-layered product containing polycarbonate resin and the above-mentioned acrylic resin, it is possible to improve the surface hardness while maintaining the thermoformability of the substrate.

The substrate may also contain additives as components other than the thermoplastic resin. Examples include heat stabilizers, antioxidants, flame retardants, flame retardant assistants, UV absorbers, release agents, and colorants. These may be used alone or in combination of two or more. Antistatic agents, fluorescent brighteners, antifogging agents, flow improvers, plasticizers, dispersants, antibacterial agents, etc. may also be added to the substrate.

The substrate preferably contains 80% by mass or more of a thermoplastic resin, more preferably 90% by mass or more, and even more preferably 95% by mass or more. The substrate preferably contains 80% by mass or more of a polycarbonate resin, more preferably 90% by mass or more, and even more preferably 95% by mass or more, of the thermoplastic resin.

A substrate further coated with a hard coat of thermoplastic resin can also be used. A substrate coated with a hard coat can be obtained by applying a hard coat composition containing a photopolymerizable compound to the substrate, drying, and then curing with ultraviolet light, or by applying a thermosetting composition containing a thermosetting compound to the substrate, drying, and then curing by heating. A method in which a hard coat composition containing a photopolymerizable compound is applied to the substrate, drying, and then curing with ultraviolet light is preferred. The hard coat is preferably provided on the substrate surface opposite the adhesive layer described below.

Any photopolymerizable compound can be used as long as it has a photopolymerizable functional group, but those containing a urethane (meth)acrylate component are preferred. The urethane (meth)acrylate contains a polymer of a resin material containing a urethane (meth)acrylate derived from a polyol, an isocyanate, and a (meth)acrylate, and a (meth)acrylate. In other words, it is preferred that the compound is a mixture of a urethane (meth)acrylate obtained by a dehydration condensation reaction of the three components of a polyol, an isocyanate, and a (meth)acrylate, and a (meth)acrylate.

Additives can be added to the hard coat composition to improve its physical properties. Examples of additives include fluorine-based or silicone-based additives that can impart antifouling and slip properties, and inorganic particle components to improve scratch resistance.

It is also possible to use a substrate made of a thermoplastic resin having a treatment layer other than the hard coat layer, such as an anti-glare layer or an anti-stain/fingerprint treatment layer.

The transparent conductive film laminate and the substrate are laminated via an adhesive layer. Any adhesive layer can be used as long as it is capable of adhering the transparent conductive film laminate and the substrate. The adhesive layer can be easily obtained by applying an adhesive to the substrate surface and drying it. It is also possible to use a commercially available optically clear adhesive sheet (OCA) or optically clear adhesive resin (OCR) for lamination.

OCA bonds adherends together under atmospheric pressure or vacuum, and uses acrylic, silicone, and other materials. Examples include LUCIACS (registered trademark, manufactured by Nitto Denko Corporation), Clearfit (registered trademark, manufactured by Mitsubishi Chemical Corporation), and HSV (manufactured by Sekisui Chemical Co., Ltd.).

OCR is an adhesive resin used to bond adherends together, and acrylic, silicone, and other materials are commercially available.

The following describes specific examples of the present invention. Note that the following examples are provided to facilitate understanding of the present invention, and the present invention is not limited to these examples.

<Surface treatment of substrate>
Substrate 1
A polycarbonate (PC) film (Mitsubishi Gas Chemical Co., Ltd., Iupilon (registered trademark) FS-2000H, glass transition temperature: 130 ° C (catalog value), A4 size, 100 μm thickness) was placed on the processing table area of a corona discharge surface treatment device CTW-0212 (manufactured by Wedge Co., Ltd.), the distance between the substrate and the treatment electrode (ceramic electrode) was 10 mm, and the PC film was treated twice on one side at an output of 0.3 kW (processing table moving speed: 3 m / min, 1 round trip). The PC film after the corona discharge surface treatment was cured for 1 day (24 hours) in a digital control desiccator DCD-SSP3 (manufactured by AS ONE Co., Ltd.) set to 25% RH (temperature 25 ± 10 ° C, humidity 40 ± 20% RH, held in the air atmosphere) to obtain a substrate 1. A 2 μl water droplet was dropped onto the corona discharge surface-treated surface of the substrate 1 under an atmospheric condition of 25° C., 50% RH, and the static contact angle after 5 seconds was measured by the sessile drop method (θ/2 method). Ion-exchanged water was used as the water, and the static contact angle was measured using a contact angle meter DMo-501 (manufactured by Kyowa Interface Science Co., Ltd.) and the attached analysis software FAMAS (manufactured by Kyowa Interface Science Co., Ltd.). As a result, the static contact angle with water was 60°.

Substrate 2
Substrate 2 was obtained by carrying out the same treatment as for Substrate 1, except that the curing period in the digital control desiccator was changed to 7 days (168 hours). The corona discharge surface-treated surface of Substrate 2 had a static contact angle with water of 70°.

Substrate 3
Substrate 3 was obtained by carrying out the same treatment as for Substrate 2, except that the corona discharge surface treatment conditions were changed to an output of 0.5 kW. The corona discharge surface-treated surface of Substrate 3 had a static contact angle with water of 70°.

Substrate 4
Substrate 4 was obtained by carrying out the same treatment as for Substrate 1, except that the curing period in the digital control desiccator was changed to 30 days (720 hours). Substrate 4 had a static contact angle with water of 75°.

Substrate 5
A PC film that was not subjected to a corona discharge surface treatment and subsequent curing was used as the substrate 5. The corona discharge surface-treated surface of the substrate 5 had a static contact angle with water of 90°.

Substrate 6
Substrate 6 was obtained by carrying out the same treatment as for Substrate 1, except that the number of days of curing in the digital control desiccator was changed to 0 days (0 hours). The corona discharge surface-treated surface of Substrate 6 had a static contact angle with water of 50°.

Substrate 7
Substrate 7 was obtained by carrying out the same treatment as for Substrate 1, except that the conditions of the corona discharge surface treatment were changed to an output of 0.2 kW. However, since it was difficult for corona discharge to occur uniformly under these conditions (discharge spots were visually observed), and it was highly likely that the surface treatment was not uniform, this substrate was excluded from the coating and evaluation of the silver nanowire ink described below.

Substrate 8
Substrate 8 was obtained by carrying out the same treatment as for Substrate 1, except that the conditions of the corona discharge surface treatment were changed to an output of 0.6 kW. However, under these conditions, the heat generated by the corona discharge caused a defect in that the substrate was partially deformed and melted, and therefore Substrate 8 produced under these conditions was excluded from the coating and evaluation of the silver nanowire ink described below.

<Preparation of Silver Nanowires>
Silver nanowire 1
Polyvinylpyrrolidone K-90 (manufactured by Nippon Shokubai Co., Ltd.) (0.98 g), AgNO ₃ (1.04 g), and FeCl ₃ (0.8 mg) were dissolved in ethylene glycol (250 ml) and reacted by heating at 150° C. for 1 hour. The obtained silver nanowire crude dispersion was dispersed in 2000 ml of a water/ethanol=20/80 [mass ratio] mixed solvent, and poured into a small benchtop tester (manufactured by NGK Insulators, Ltd., using a ceramic membrane filter Cefilt, membrane area 0.24 m ² , pore size 2.0 μm, dimensions Φ30 mm×250 mm, filtration differential pressure 0.01 MPa), and cross-flow filtration was performed at a circulation flow rate of 12 L/min and a dispersion temperature of 25° C. to remove impurities, and silver nanowires 1 (average diameter: 26 nm, average length: 20 μm) were obtained. The average diameter of the obtained silver nanowires 1 was determined by measuring the dimensions (diameters) of 100 arbitrarily selected silver nanowires using a field emission scanning electron microscope JSM-7000F (manufactured by JEOL Ltd.) and taking the arithmetic mean value. The average length of the obtained silver nanowires 1 was determined by measuring the dimensions (lengths) of 100 arbitrarily selected silver nanowires using a shape measuring laser microscope VK-X200 (manufactured by Keyence Corporation) and taking the arithmetic mean value. The methanol, ethylene glycol, AgNO ₃ , and FeCl ₃ used were reagents manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.

<Preparation of conductive ink (silver nanowire ink)>
Preparation Example 1 (Silver Nanowire Ink 1)
11 g of a dispersion of silver nanowires 1 synthesized by the polyol method in a water/ethanol mixed solvent (silver nanowire concentration 0.62 mass%, water/ethanol = 20/80 [mass ratio]), 1.1 g of water, 6.0 g of methanol (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), 7.2 g of ethanol (manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), 12.8 g of propylene glycol monomethyl ether (PGME, manufactured by Fuji Film Wako Pure Chemical Industries, Ltd.), 1.2 g of propylene glycol (PG, manufactured by Asahi Glass Co., Ltd.), and 0.7 g of an aqueous solution of PNVA (registered trademark) (manufactured by Showa Denko K.K., solid content concentration 10 mass%, absolute molecular weight 900,000) were mixed and stirred (rotation speed 100 rpm) for 1 hour at room temperature under atmospheric conditions using a mix rotor VMR-5R (manufactured by AS ONE Corporation) to produce 40 g of silver nanowire ink 1.

<Printing of silver nanowire ink coating>
The silver nanowire ink 1 prepared in Preparation Example 1 was applied to the corona discharge surface-treated main surfaces of the substrates 1 to 6 with a bar coat printer (AFA-Standard manufactured by Coatec Co., Ltd.) at a wet film thickness of 20 μm, and a transparent conductive film (silver nanowire ink coating film) was printed as an A4 size solid pattern. After the solvent was dried at 80° C. for 1 minute using an incubator ETAC HS350 manufactured by Kusumoto Chemical Co., Ltd., the sheet resistance of the obtained transparent conductive film was measured. The sheet resistance is the arithmetic average value of the sheet resistance of 30 points obtained by dividing the transparent conductive film (solid pattern) into areas of 3 cm square and measuring the center of each area. The sheet resistance of the transparent conductive film using the silver nanowire ink 1 was 50Ω/□ in all cases. The sheet resistance was measured using a non-contact resistance meter (EC-80P manufactured by Napson Co., Ltd.). The thickness of the transparent conductive film was measured using a film thickness measurement system based on optical interference (F20-UV manufactured by Filmetrics Inc.) and found to be 80 nm. Measurements were taken at different locations and the average value of measurements taken at three points was used as the film thickness. A spectrum from 450 nm to 800 nm was used for the analysis. This measurement system allows direct measurement of the film thickness (Tc) of the transparent conductive film (silver nanowire ink coating film) formed on a polycarbonate film.

<Preparation of protective film ink (resin composition)>
Synthesis examples of polyurethanes containing carboxy groups Synthesis Example 1
A 2 L three-neck flask equipped with a stirrer, a thermometer, and a condenser (reflux condenser) was charged with 16.7 g of C-1015N (manufactured by Kuraray Co., Ltd., polycarbonate diol, raw material diol molar ratio: 1,9-nonanediol:2-methyl-1,8-octanediol=15:85, molecular weight 964) as a polyol compound, 10.8 g of 2,2-dimethylolbutanoic acid (manufactured by Huzhou Changsheng Chemical Co., Ltd.) as a dihydroxy compound containing a carboxy group, and 62.6 g of propylene glycol monomethyl ether acetate (manufactured by FUJIFILM Wako Pure Chemical Industries, Ltd.) as a solvent, and the 2,2-dimethylolbutanoic acid was dissolved at 90° C.

The temperature of the reaction liquid was lowered to 70°C, and 23.5 g of polyisocyanate, Desmodur (registered trademark)-W (bis-(4-isocyanatocyclohexyl)methane), manufactured by Sumika Covestro Urethane Co., Ltd.), was added dropwise over 30 minutes using a dropping funnel. After dropping was completed, the temperature was raised to 100°C, and the reaction was carried out at 100°C for 15 hours. After it was confirmed by IR that the isocyanate had almost completely disappeared, 0.5 g of isobutanol was added, and the reaction was carried out at 100°C for a further 6 hours. The weight average molecular weight of the resulting polyurethane containing carboxyl groups, as determined by GPC, was 33,500, and the acid value of the resin solution was 39.4 mgKOH/g.

Protective Film Ink 1
7.1 g of the carboxyl group-containing polyurethane solution (solid content concentration 42.4% by mass) obtained in Synthesis Example 1 was added to 92.9 g of a mixture of 1-hexanol (C6OH) and ethyl acetate (EA) (C6OH:EA = 50:50 (mass ratio)) as a solvent, and the mixture was stirred at 1200 rpm for 20 minutes using a Thinky Corporation-manufactured centrifugal vacuum mixer Awatori Rentaro (registered trademark) ARV-310 to make the mixture homogeneous, thereby obtaining protective film ink 1. The non-volatile content (solid content) concentration of protective film ink 1 (amount of carboxyl group-containing polyurethane) calculated from the mass before and after drying of the solvent was 3% by mass.

<Protective film printing>
Example 1
The transparent conductive film (silver nanowire ink coating film) printed on the corona discharge surface-treated main surface of the substrate 1 using the silver nanowire ink 1 obtained in Preparation Example 1 was coated with the protective film ink 1 at a wet film thickness of about 7 μm on the main surface of the transparent conductive film using the bar coat printer described above, and a transparent conductive film with a protective film (silver nanowire ink coating film with a protective film) was printed as an A4 size solid pattern. The solvent was dried at 80° C. for 1 minute using the thermostat described above to obtain a transparent conductive film laminate according to Example 1. The sheet resistance of the obtained transparent conductive film laminate was measured. The sheet resistance in this case is the arithmetic average value of the sheet resistance of 30 points obtained by dividing the transparent conductive film laminate (solid pattern) into areas of 3 cm square and measuring the center of each area. The sheet resistance of the transparent conductive film laminate using the protective film ink 1 was 50Ω/□ in all cases. The sheet resistance was measured using the non-contact resistance meter described above. The thickness of the protective film was measured using a film thickness measurement system (F20-UV manufactured by Filmetrics Inc.) based on optical interference, similar to the film thickness of the transparent conductive film (silver nanowire ink coating film) described above, and was found to be 90 nm. In this case, the measurement points were changed and the average value of measurements taken at three points was taken as the film thickness. A spectrum from 450 nm to 800 nm was used for the analysis. With this measurement system, the total film thickness (Tc+Tp) of the film thickness (Tc) of the transparent conductive film (silver nanowire ink coating film) formed on the polycarbonate film and the film thickness (Tp) of the protective film formed thereon can be directly measured, so the film thickness (Tp) of the protective film can be obtained by subtracting the film thickness (Tc) of the transparent conductive film (silver nanowire ink coating film) measured earlier from this measurement value.

Examples 2 to 4 and Comparative Examples 1 and 2
In the same manner as in Example 1, a silver nanowire ink coating and a protective film were formed on the corona discharge surface-treated main surface of each substrate as shown in Table 1, to obtain each transparent conductive film laminate.

<Moldable transparent conductive film laminate of transparent conductive film laminate and substrate (front panel)>
Example 5
A front plate was attached to the protective film side of the transparent conductive film laminate obtained in Example 2 via an OCA to produce a moldable transparent conductive film laminate in which the transparent conductive film laminate and the front plate were laminated. As the OCA, CS9864UAS (thickness 100 μm) manufactured by Nitto Denko Corporation was used. As the front plate, FS-2000H (polycarbonate, thickness 0.5 mm) manufactured by Mitsubishi Gas Chemical Company was used. Specifically, after cutting the OCA having separators on both sides to a predetermined size, one separator was peeled off, and one adhesive surface was attached to the surface of the front plate using a hand roller (2 kg roller) under the condition of one round trip. Next, the other separator was peeled off, and the other adhesive surface was attached to the protective film side of the transparent conductive film laminate under the following conditions to produce a moldable transparent conductive film laminate in which the transparent conductive film laminate and the front plate were laminated, and used as a test piece.
(Lamination conditions)
Surface pressure: 0.4 MPa
Degree of vacuum: 30 Pa
Next, the test piece was placed in an autoclave and autoclaved for 15 minutes under conditions of a temperature of 50° C. and a pressure of 0.5 MPa. The test piece was then left to stand for 1 hour in an environment of 23° C. and 50% RH before being used for testing.

Comparative Example 3
A moldable transparent conductive film laminate was produced by laminating the transparent conductive film laminate and a front panel in the same manner as in Example 5, except that the transparent conductive film laminate of Comparative Example 1 was used.

Evaluation of transparent conductive film <sheet resistance value>
The sheet resistance of each of the transparent conductive film laminates obtained in each of the Examples and Comparative Examples was measured using a non-contact resistance meter (EC-80P manufactured by Napson Corporation, probe type High: 10 to 1000 Ω/□, S-High: 1000 to 3000 Ω/□) and judged according to the following criteria. The results are shown in Table 1.
◯: The average sheet resistance value at each location is 50±5 Ω/□, and σ is 10 or less.
Δ: The average sheet resistance value at each location is 50±5 Ω/□, and σ is greater than 10 and less than 30.
×: The average value of the sheet resistance at each location is not 50±5 Ω/□.

<Optical properties>
The haze of each of the transparent conductive film laminates obtained in the above-mentioned Examples and Comparative Examples was measured using a Haze Meter NDH 2000 (manufactured by Nippon Denshoku Industries Co., Ltd.) and judged according to the following criteria. The results are shown in Table 1.
◯: Haze is 1.0 or less, total light transmittance is 88% or more, and b* is 1.4 or less.
△: Only two of the three items above apply.
×: Only one or none of the above three items apply.

<Tensile properties>
The tensile test was performed using test pieces obtained by cutting each transparent conductive film laminate obtained in each of the examples and comparative examples into a strip shape with a width of 30 mm and a length of 160 mm. In advance, two marks (a total of five marks) were made at the center of the longitudinal direction of the strip (80 mm from both ends (short sides)) and at both ends from the center at 20 mm intervals at the site corresponding to the gap between the chucks, and four divisions were provided, and the sheet resistance value of each was measured and defined as R _0. The test piece was then set in a precision universal testing machine (Shimadzu Corporation Autograph AG-X). The distance between the chucks when set was 100 mm, and an arbitrary strain was applied at a test speed of 50 mm/min and a test set temperature of 155°C. After the test, the sheet resistance values of 10 points were measured again and defined as R. From this value, R/R ₀ was calculated and determined according to the following criteria. The results are shown in Table 1.
◯: The average value of R/ _R0 at 15% strain is 10 or less.
Δ: The average value of R/ _R0 at 15% strain is more than 10.
×: Not applicable to the above (having some areas that cannot be measured).

<Environmental resistance>
Ten test pieces of each of the transparent conductive film laminates obtained in the above examples and comparative examples were prepared. The sheet resistance change after 1000 hours in a thermohygrostat (ETAC HIFLEX SX403N manufactured by Kusumoto Chemicals Co., Ltd.) maintained at 85° C. and 85% RH was calculated and evaluated according to the following evaluation criteria. The results are shown in Table 1.
◯: Of the ten test pieces, ten had a sheet resistance change within ±20%.
Δ: Of ten test pieces, the number of test pieces in which the sheet resistance value change was within ±20% was 9 to 5.
x: Of ten test pieces, the number of test pieces in which the sheet resistance value change was within ±20% was four or less.
The change in sheet resistance was measured as follows.
Using the same test piece as in the case of tensile properties, the sheet resistance value after standing in the high-temperature, high-humidity chamber for 1000 hours was measured in the same manner as in the case of tensile properties. The measurement result is taken as (Ra). The sheet resistance value of the test piece before standing was also measured in the same manner. The measurement result is taken as (Rb). Next, the ratio of (Ra) to (Rb) ((Ra/Rb)) was calculated and used as the change in sheet resistance value. In the above judgment criteria, ◯ means that ((Ra/Rb)) is 1.2 or less.

<Environmental resistance of test pieces after tension>
In the tensile test, test pieces of each Example and Comparative Example were prepared by applying a 5% strain. The sheet resistance change after 1000 hours in a thermohygrostat (ETAC HIFLEX SX403N manufactured by Kusumoto Chemicals Co., Ltd.) maintained at 85° C. and 85% RH was calculated and evaluated according to the following criteria. The results are shown in Table 1.
The change in sheet resistance was measured in the same manner as in the case of the environmental resistance.
◯: The change in sheet resistance is within ±10%.
Δ: The change in sheet resistance value is more than ±10% and is equal to or less than ±20%.
×: The change in sheet resistance value exceeded ±20%.

Table 1 shows the evaluation results of the transparent conductive film laminates of Examples 1 to 4 and Comparative Examples 1 and 2.
All of Examples 1 to 4, which used substrates 1 to 4 in which the static contact angle with water of the corona discharge surface-treated surface was 60° or more and 75° or less by curing for 1 day (24 hours) or more after corona discharge surface treatment (output 0.3 to 0.5 kW), had good environmental resistance and were rated as ○. This is presumably due to the effect of improving the compatibility (wettability) of the substrate and the silver nanowire ink by setting the static contact angle with water of the substrate surface during silver nanowire ink coating printing to an appropriate value (60° or more and 75° or less).

By subjecting the substrate to a corona discharge surface treatment and using a substrate adjusted to the appropriate static contact angle with water, it can be confirmed by a simple peel test that the adhesion between the substrate and the silver nanowires is improved. The simple peel test is a method in which cellophane tape is applied to the printed surface after printing the silver nanowire ink coating and before printing the protective film, and the state of the printed surface is judged when the tape is peeled off. In Examples 1 to 4, which used substrates 1 to 4 with static contact angles of 60° to 75°, the silver nanowire ink coating did not peel off even when a simple peel test was performed. On the other hand, in Comparative Example 1, which used substrate 5 with a static contact angle with water of 90°, peeling of the silver nanowire ink coating occurred in that area when the simple peel test was performed.

It can be confirmed by microscopic observation that the in-plane uniformity of the silver nanowires is improved by subjecting the substrate to a corona discharge surface treatment and using a substrate adjusted to the appropriate static contact angle with water. The silver nanowire ink coating was observed using a shape measuring laser microscope VK-X200 (manufactured by Keyence Corporation) as the microscope. In Examples 1 to 4, which used substrates 1 to 4 with static contact angles with water of 60° or more and 75° or less, it was confirmed that the silver nanowires were coated uniformly within the surface.

On the other hand, in Comparative Example 1, which used a substrate 5 with a static contact angle with water of 90°, a sea-island pattern was observed, and it was confirmed that the silver nanowires were not uniformly applied within the surface. Photographs of the substrate surfaces observed under a microscope for Example 1 and Comparative Example 1 are shown in Figures 1 and 2.

Comparative Example 1, which used Substrate 5, which was not subjected to corona discharge surface treatment and had a static contact angle with water of 90° on the substrate surface, was rated as x for poor environmental resistance. This is presumably because, compared to Examples 1 to 4, the static contact angle with water was higher, and the wettability of the substrate with the silver nanowire ink was insufficient. Even in the case of Comparative Example 1, which had a high static contact angle with water of 90°, no difference was observed in the sheet resistance, optical properties, and tensile properties compared to Examples 1 to 4.

In addition, Comparative Example 2, which used Substrate 6 with a static contact angle of 50° with water without curing after corona discharge surface treatment, had slightly poor environmental resistance and was rated as △. By subjecting the substrate surface to corona discharge surface treatment, the static contact angle of the substrate surface was reduced to 50°, but the substrate surface was in a very unstable state immediately after corona discharge surface treatment, and the increase in the static contact angle with water gradually slowed down as the curing time passed, reaching 70° after one day (24 hours) of curing, and thereafter the change over time was small and tended to stabilize (saturate). The reason why Comparative Example 2 had slightly poor environmental resistance despite the low static contact angle with water of 50° is not clear, but it is presumed that this was due to the fact that the static contact angle with water was unstable compared to Examples 1 to 4. When the static contact angle with water is low at 50°, the sheet resistance tends to be high and the variation tends to be large. It is suggested that in order to obtain good environmental resistance, it is effective for the substrate surface to have a stable static contact angle with water within an appropriate range.

When the output of the corona discharge surface treatment was 0.2 kW or less, it was difficult for the corona discharge to occur uniformly, so substrate 7 prepared under these conditions was excluded from the coating and evaluation of the silver nanowire ink described above. When the output of the corona discharge surface treatment was 0.6 kW or more, the heat generated by the corona discharge sometimes caused partial deformation and melting of the substrate, so substrate 8 prepared under these conditions was excluded from the coating and evaluation of the silver nanowire ink described above.

In Examples 1 to 4, which used substrates with surfaces that had been subjected to corona discharge surface treatment and had an appropriate static contact angle with water, it was confirmed that the substrates had good environmental resistance even after tensile tests were performed.

Table 2 shows the evaluation results of the moldable transparent conductive film laminates of Example 5 and Comparative Example 3. As with the transparent conductive film laminates of Examples 1 to 4, the moldable transparent conductive film laminate of Example 5, which used a substrate having a surface that had been subjected to corona discharge surface treatment and adjusted to an appropriate contact angle with water, was confirmed to have good environmental resistance even after a tensile test.

On the other hand, in Comparative Example 3, which used a substrate that had not been subjected to corona discharge surface treatment and had a surface with a static contact angle with water of 90°, the environmental resistance was poor both before and after the tensile test, and the substrate was rated as ×.

Claims (9)

A transparent substrate made of a transparent thermoplastic resin film;
a transparent conductive film formed on at least one of the main surfaces of the transparent substrate and including a binder resin and metal nanowires;
a protective film containing a resin component formed on the transparent conductive film;
having
the binder resin comprises at least one of poly-N-vinylacetamide, a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as a monomer unit, and a cellulose-based resin;
A transparent conductive film laminate, wherein the transparent substrate is a polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less on a main surface on which the transparent conductive film is formed. The transparent conductive film laminate according to claim 1, wherein the binder resin is at least one of poly-N-vinylacetamide and a copolymer containing 70 mol % or more of N-vinylacetamide (NVA) as a monomer unit. The transparent conductive film laminate according to claim 2, wherein the binder resin is poly-N-vinylacetamide. The transparent conductive film laminate according to any one of claims 1 to 3, wherein the resin component constituting the protective film is derived from a thermoplastic resin containing polyurethane or ethyl cellulose containing a carboxy group. The transparent conductive film laminate according to any one of claims 1 to 3, wherein the metal nanowires are silver nanowires. A first step of preparing a polycarbonate film having at least one main surface having a static contact angle with water of 60 degrees or more and 75 degrees or less;
a second step of applying a conductive ink containing a binder resin and metal nanowires onto at least one of the main surfaces of the polycarbonate film having a static contact angle with water of 60 degrees or more and 75 degrees or less to form a transparent conductive film;
a third step of applying a protective film ink containing a resin component onto the transparent conductive film to form a protective film;
A method for producing a transparent conductive film laminate comprising the steps of: The method for producing a transparent conductive film laminate according to claim 6, wherein the first step includes a step of subjecting at least one main surface of the polycarbonate film to a corona treatment or plasma treatment. A moldable transparent conductive film laminate comprising the transparent conductive film laminate according to any one of claims 1 to 3 and a resin film mainly composed of polycarbonate. 4. The transparent conductive film laminate according to claim 1, wherein the ratio (Ra/Rb) of the sheet resistance value (Ra) after standing for 1000 hours in an environment of 85° C. and 85% RH to the sheet resistance value (Rb) before standing is 1.2 or less.