Transparent conductive film

Abstract

To provide a transparent conductive film with excellent light transmission in the near-infrared region. [Solution] The transparent conductive film according to an embodiment of the present invention is a transparent conductive film comprising a substrate and a conductive layer disposed on at least one side of the substrate, wherein the surface resistance of the transparent conductive film is 200 Ω / □ or less, and the light transmittance of the transparent conductive film in the wavelength region of 780 nm to 2500 nm is 85% or more.

Description

[Technical Field]

[0001] This invention relates to a transparent conductive film. [Background technology]

[0002] Conventionally, transparent conductive films, in which a metal oxide layer such as an indium-tin composite oxide layer (ITO layer) is formed on a resin film, have been widely used as electrodes for touch sensors and the like. However, transparent conductive films with a metal oxide layer have low light transmittance in the near-infrared region, and when light transmittance is taken into consideration, it is difficult to obtain the desired resistance value. [Prior art documents] [Patent Documents]

[0003] [Patent Document 1] Special Publication No. 2009-505358 [Overview of the Initiative] [Problems that the invention aims to solve]

[0004] The present invention was made to solve the above problems, and its main objective is to provide a transparent conductive film with excellent light transmission in the near-infrared region. [Means for solving the problem]

[0005] [1] A transparent conductive film according to an embodiment of the present invention is a transparent conductive film comprising a substrate and a conductive layer disposed on at least one side of the substrate, wherein the surface resistance of the transparent conductive film is 200 Ω / □ or less, and the maximum light transmittance of the transparent conductive film in the wavelength region of 780 nm to 2500 nm is 85% or more. [2] The transparent conductive film in [1] above may have a surface resistance of 100 Ω / □ or less. [3] The transparent conductive film described in [1] or [2] above may have a ratio (T905 / T555) of the light transmittance at a wavelength of 905 nm (T905) to the light transmittance at a wavelength of 555 nm (T555) that is greater than 0.95 and less than or equal to 1.1. [4] The transparent conductive film described in any of [1] to [3] above may have a maximum light transmittance of 85% or more in the wavelength range of 900 nm to 1600 nm. [5] The transparent conductive film described in any of [1] to [4] above may have a light transmittance of 85% or more at a wavelength of 905 nm. [6] In the transparent conductive film described in any of [1] to [5] above, the conductive layer may include a fibrous conductive material and a polymer matrix. [7] The transparent conductive film described in [6] above may also be made of metal nanowires instead of the fibrous conductive material. [8] The transparent conductive film described in any of [1] to [7] above may be for use in a transparent heater. [Effects of the Invention]

[0006] According to embodiments of the present invention, a transparent conductive film with excellent light transmittance in the near-infrared region can be provided. [Brief explanation of the drawing]

[0007] [Figure 1] This is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention. [Modes for carrying out the invention]

[0008] The following describes embodiments of the present invention, but the present invention is not limited to these embodiments.

[0009] A. Overall structure of the transparent conductive film Figure 1 is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention. The transparent conductive film 100 comprises a substrate 10 and a conductive layer 20 disposed on at least one side of the substrate 10. In one embodiment, the conductive layer 20 includes a fibrous conductive material 21. Examples of fibrous conductive materials include metal nanowires and carbon nanotubes. Preferably, metal nanowires are used. Although not shown, the transparent conductive film may further include any other suitable layers.

[0010] In one embodiment, the transparent conductive film 100 includes a protective layer 30 located on the opposite side of the conductive layer 20 from the substrate 10. The protective layer 30 may be a layer that protects the fibrous conductive material 21. In embodiments of the present invention, the durability of the conductive layer 20 can be improved by providing the protective layer 30. More specifically, a conductive layer composed of a fibrous conductive material (e.g., metal nanowires) has characteristics such as low scratch resistance and humidity resistance. By providing a protective layer, these problems can be resolved, and the durability of the conductive layer (and consequently, the durability of the transparent conductive film) can be improved. The conductive layer 20 may also contain components that make up the protective layer 30 (e.g., resins that make up the protective layer).

[0011] The surface resistance of the transparent conductive film described above is 200 Ω / □ or less, preferably 0.01 Ω / □ to 200 Ω / □, more preferably 1 Ω / □ to 180 Ω / □, particularly preferably 5 Ω / □ to 150 Ω / □, and most preferably 10 Ω / □ to 100 Ω / □. The surface resistance of the transparent conductive film may be 100 Ω / □ or less, 60 Ω / □ or less, 50 Ω / □ or less, 45 Ω / □ or less, or 40 Ω / □. Within this range, a transparent conductive film particularly suitable for transparent heater applications (especially transparent heaters for vehicles) can be obtained. In one embodiment, the surface resistance of the transparent conductive film described above is 20 Ω / □ or more. One element that controls the surface resistance of the transparent conductive film is the thickness of the conductive layer (the amount of fibrous conductive material in the conductive layer). By adjusting the thickness of the conductive layer so that the surface resistance is above a predetermined level, a transparent conductive film with excellent light transmittance (for example, light transmission in the near-infrared region) can be obtained.

[0012] The transparent conductive film described above has a light transmittance of 85% or more, preferably 90% or more, in the wavelength range of 780 nm to 2500 nm. Within this range, a transparent conductive film suitable for applications that transmit laser light in the near-infrared region can be provided. For example, in the field of autonomous driving of vehicles using LiDAR (Light Detection And Ranging), a transparent conductive film suitable for a component that can efficiently transmit laser light (near-infrared region) necessary for sensing can be provided. A transparent conductive film with light transmittance in the wavelength range of 780 nm to 2500 nm can be obtained, for example, by forming a conductive layer containing metal nanowires. A higher light transmittance in the wavelength range of 780 nm to 2500 nm is preferable, but its upper limit is, for example, 95% (preferably 98%). In this specification, the light transmittance in a predetermined wavelength range means the maximum value of the light transmittance in that range. In other words, "light transmittance in the wavelength range of 780 nm to 2500 nm" and "the maximum value of light transmittance in the wavelength range of 780 nm to 2500 nm" are synonymous. Light transmittance can be measured using a specified spectrophotometer.

[0013] In one embodiment, the transparent conductive film is used in a transparent heater (for example, a transparent heater for a vehicle). The transparent heater can have any suitable configuration. Typically, the transparent heater may be configured to generate heat by passing an electric current through a transparent conductive film on which a pair of electrodes are arranged. In a transparent heater, the transparent conductive film can be used as a heat source. A transparent conductive film having a conductive layer containing metal nanowires is also advantageous in that it has excellent heat generation characteristics, and combined with its excellent near-infrared transmittance, it can be preferably used, for example, in an anti-fog heater (transparent heater) for vehicle windows.

[0014] The above transparent conductive film preferably has a light transmittance of 80% or more, more preferably 85% or more, and particularly preferably 90% or more in the wavelength range of 900 nm to 1600 nm. If it is within such a range, the above effects will be remarkable. The light transmittance in the wavelength range of 900 nm to 1600 nm is preferably as high as possible, and its upper limit is, for example, 95% (preferably 98%). "The light transmittance in the wavelength range of 900 nm to 1600 nm" and "the maximum value of the light transmittance in the wavelength range of 900 nm to 1600 nm" are synonymous. Also, in one embodiment, the minimum value of the light transmittance of the transparent conductive film in the wavelength range of 900 nm to 1600 nm is 80% or more. That is, the light transmittance can be 80% or more throughout the wavelength range of 900 nm to 1600 nm. It is more preferable that the light transmittance is 85% or more throughout the wavelength range of 900 nm to 1600 nm, and further preferably 90% or more.

[0015] The ratio (T905 / T555) of the light transmittance (T905) at a wavelength of 905 nm to the light transmittance (T555) at a wavelength of 555 nm is preferably greater than 0.95 and less than or equal to 1.2, more preferably 0.95 to 1.2, more preferably 0.98 to 1.15, still more preferably 0.99 to 1.1, still more preferably 1 to 1.1, and particularly preferably 1 to 1.05. In one embodiment, T905 / T555 is greater than 0.95 and less than or equal to 1.1. If it is within such a range, a transparent conductive film that can preferably transmit the laser light required for sensing can be obtained.

[0016] The light transmittance at a wavelength of 905 nm is preferably 85% or more, more preferably 88% or more, and still more preferably 90% or more. If it is within such a range, a transparent conductive film suitable for applications that transmit laser light in the near-infrared region can be provided. The light transmittance at a wavelength of 905 nm is preferably as high as possible, and its upper limit is, for example, 95% (preferably 98%).

[0017] The light transmittance at a wavelength of 555 nm is preferably 80% or more, more preferably 85% to 95%.

[0018] The thickness of the above transparent conductive film is preferably 10 μm to 500 μm, more preferably 15 μm to 300 μm, and still more preferably 20 μm to 200 μm.

[0019] B. Conductive layer In one embodiment, the conductive layer includes a fibrous conductive material and a polymer matrix. By forming a conductive layer containing a fibrous conductive material, a transparent conductive film excellent in flexibility and light transmittance can be obtained. The fibrous conductive material is protected by the polymer matrix. As a result, corrosion of the fibrous conductive material is prevented, and a transparent conductive film with more excellent durability can be obtained.

[0020] The thickness of the above conductive layer is preferably 50 nm to 300 nm, more preferably 80 nm to 200 nm.

[0021] (Fibrous conductive material) As the above fibrous conductive material, metal nanowires can be preferably used.

[0022] Metal nanowires refer to a conductive substance made of metal, having a needle-like or thread-like shape, and a diameter in the nanometer size. The metal nanowires may be linear or curved. By using a conductive layer composed of metal nanowires, the metal nanowires form a mesh-like pattern, so that even a small amount of metal nanowires can form a good electrical conduction path, and a transparent conductive film with low electrical resistance can be obtained. Furthermore, since the metal nanowires form a mesh-like pattern, openings are formed in the gaps of the mesh, and a transparent conductive film with high light transmittance can be obtained.

[0023] The ratio of the thickness d to the length L (aspect ratio: L / d) of the above-mentioned fibrous conductive material (preferably a metal nanowire) is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. By using a fibrous conductive material with such a large aspect ratio, the fibrous conductive material intersects well, and high conductivity can be achieved with a small amount of fibrous conductive material. As a result, a transparent conductive film with high light transmittance can be obtained. In this specification, "thickness of the fibrous conductive material" means the diameter if the cross-section of the fibrous conductive material is circular, the minor axis if it is elliptical, and the longest diagonal if it is polygonal. The thickness and length of the fibrous conductive material can be confirmed by scanning electron microscope or transmission electron microscope.

[0024] The thickness of the above-mentioned fibrous conductive material (preferably metal nanowire) is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably 10 nm to 100 nm, and most preferably 10 nm to 50 nm. Within this range, a conductive layer with high light transmittance can be formed.

[0025] The length of the above-mentioned fibrous conductive material (preferably metal nanowire) is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and particularly preferably 10 μm to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

[0026] Any suitable metal can be used as the metal constituting the above-mentioned metal nanowire, as long as it is a conductive metal. Examples of metals constituting the above-mentioned metal nanowire include silver, gold, copper, and nickel. Materials that have been plated (for example, gold plated) of these metals may also be used. Among these, silver, copper, or gold are preferred from the viewpoint of conductivity, and silver is more preferred.

[0027] Any suitable method can be used to manufacture the above-mentioned metal nanowires. For example, methods include reducing silver nitrate in solution, applying a voltage or current from the tip of a probe to the surface of a precursor, drawing out metal nanowires at the tip of the probe, and continuously forming the metal nanowires. In the method of reducing silver nitrate in solution, silver nanowires can be synthesized by liquid-phase reduction of a silver salt such as silver nitrate in the presence of a polyol such as ethylene glycol and polyvinylpyrrolidone. Silver nanowires of uniform size can be mass-produced according to methods such as those described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745, and Xia, Y. et al., Nano letters (2003) 3(7), 955-960.

[0028] The content of fibrous conductive material (preferably metal nanowires) in the conductive layer is preferably 30% to 90% by weight, and more preferably 45% to 80% by weight, relative to the total weight of the conductive layer. Within this range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0029] If the above metal nanowire is a silver nanowire, the density of the conductive layer is preferably 1.3 g / cm³. 3 ~10.5g / cm 3 More preferably 1.5 g / cm³ 3 ~3.0g / cm 3 Within this range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0030] In one embodiment, the conductive layer is patterned. Any suitable method can be used for patterning, depending on the form of the conductive layer. The shape of the pattern of the conductive layer can be any suitable shape depending on the application. For example, patterns described in Japanese Patent Publication No. 2011-511357, Japanese Patent Application Publication No. 2010-164938, Japanese Patent Application Publication No. 2008-310550, Japanese Patent Publication No. 2003-511799, and Japanese Patent Publication No. 2010-541109 are examples. After the conductive layer is formed on the substrate, it can be patterned using any suitable method, depending on the form of the conductive layer.

[0031] In one embodiment, the metal nanowires in the conductive layer have a fused network structure. In the metal nanowires having a fused network structure, the metal nanowires are fused to each other at contact points. By forming a conductive layer containing metal nanowires having a fused network structure, a transparent conductive film with higher conductivity can be obtained without impeding transparency.

[0032] A conductive layer containing metal nanowires having the above-described fused network structure can be formed, for example, by adding an additive to promote fusion to a metal nanowire dispersion used during conductive layer formation. Examples of such additives include metal halides (e.g., LiCl, CsCl, NaF, NaCl, NaBr, NaI, KCl, MgCl2, CaCl2, AlCl3, AgF, etc.), inorganic acids (e.g., nitric acid, nitrite, sulfuric acid, etc.), organic acids (e.g., oxalic acid, citric acid, formic acid, acetic acid, lactic acid, propionic acid, butyric acid, acrylic acid, pyruvic acid, trichloroacetic acid, trifluoroacetic acid, hexanoic acid, octanoic acid, decanoic acid, dodecanoic acid (lauric acid), tetradecanoic acid (myristic acid), hexadecanoic acid (palmitic acid), octadecanoic acid (stearic acid), 2-ethylbutyric acid, 2- Examples include methylhexanoic acid, 2-ethylhexanoic acid, 2-propylpentanoic acid, pivalic acid, neoheptanoic acid, neononanoic acid, neodecanoic acid, etc., silver salts (e.g., silver nitrate, silver nitrite, silver lactate, silver chloride, silver sulfate, silver oxide, silver acetate, silver chlorate, silver sulfide, etc., silver formate, silver hexanoate, silver octanoate, silver decanoate, silver dodecanoate, silver tetradecanoate, silver hexadecanate, silver octadecanoate, silver pentanoate, silver pivalate, silver neoheptanoate, silver neononanoate, silver neodecanoate, etc.), and compounds containing elements that can form silver salts (chlorine, sulfur, etc.) (hydrogen chloride, sodium chloride, etc.). Preferably, these are metal halides, and more preferably, NaCl, AgF, LiF, Nabr, or NaF. In one embodiment, a conductive layer containing metal nanowires having the fused network structure described above can be formed by coating a metal nanowire dispersion containing the additives and then subjecting it to heat treatment and / or pressure treatment. The heat treatment temperature is, for example, 50°C to 200°C.

[0033] A conductive layer containing metal nanowires having the above-described fused network structure may be formed by exposing a coating layer of metal nanowire dispersion to acid halide vapor. Examples of acid halide vapors include HCl, HBr, HI, or mixtures thereof.

[0034] Metal nanowires having a fused network structure and methods for producing the same are described, for example, in Japanese Patent Publication No. 2015-530693. The description in said publication is incorporated herein by reference.

[0035] (Polymer matrix) Any suitable polymer can be used as the polymer constituting the polymer matrix described above. Examples of such polymers include acrylic polymers; polyester polymers such as polyethylene terephthalate; aromatic polymers such as polystyrene, polyvinyltoluene, polyvinylxylene, polyimide, polyamide, and polyamideimide; polyurethane polymers; epoxy polymers; polyolefin polymers; acrylonitrile-butadiene-styrene copolymer (ABS); cellulose; silicone polymers; polyvinyl chloride; polyacetate; polynorbornene; synthetic rubber; and fluorine polymers. Preferably, a curable resin (preferably an ultraviolet-curable resin) composed of polyfunctional acrylates such as pentaerythritol triacrylate (PETA), neopentyl glycol diacrylate (NPGDA), dipentaerythritol hexaacrylate (DPHA), dipentaerythritol pentaacrylate (DPPA), and trimethylolpropane triacrylate (TMPTA) is used. The polymer matrix may be a resin constituting the protective layer (details will be described later).

[0036] The above polymer matrix can be formed by first forming a layer made of fibrous conductive material on a substrate, then applying a polymer solution onto the layer, and subsequently drying or curing the applied layer. This operation forms a conductive layer in which fibrous conductive material is present in the polymer matrix. The above polymer solution contains the polymer constituting the polymer matrix, or a precursor of the polymer (monomer constituting the polymer). The above polymer solution may contain a solvent. Examples of solvents included in the above polymer solution include alcohol-based solvents, ketone-based solvents, tetrahydrofuran, hydrocarbon-based solvents, or aromatic solvents. Preferably, the solvent is volatile. The boiling point of the solvent is preferably 200°C or lower, more preferably 150°C or lower, and even more preferably 100°C or lower.

[0037] C. Protective layer The thickness of the protective layer is preferably 10 nm to 1000 nm, and more preferably 60 nm to 800 nm. Within this range, a transparent conductive film with excellent durability can be obtained.

[0038] The total thickness of the conductive layer and the protective layer is preferably 60 nm to 1000 nm, and more preferably 70 nm to 800 nm. Within this range, a transparent conductive film with excellent durability can be obtained.

[0039] Typically, the protective layer described above is composed of a resin. Any suitable resin can be used as the resin constituting the protective layer, as long as the effects of the present invention are obtained. Examples of such resins include acrylic resins; polyester resins such as polyethylene terephthalate; aromatic resins such as polystyrene, polyvinyltoluene, polyvinylxylene, polyimide, polyamide, and polyamideimide; polyurethane resins; epoxy resins; polyolefin resins; acrylonitrile-butadiene-styrene copolymer (ABS); cellulose; silicone resins; polyvinyl chloride; polyacetate; polynorbornene; synthetic rubber; and fluororesins.

[0040] In one embodiment, a curable resin (e.g., an active energy ray curable resin, a thermosetting resin) is used as the resin for forming the protective layer. The protective layer, which is made of a curable resin, can be formed by curing a composition for forming a curable protective layer.

[0041] In one embodiment, the cured product of a curable protective layer-forming composition containing a (meth)acrylate monomer and / or a (meth)acrylate oligomer is used as the curable resin. Using such a resin, a protective layer with a favorably adjusted shear strength can be obtained. Specific examples of (meth)acrylate monomers and acrylate oligomers include, for example, trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tetra(meth)acrylate, tris(acryloxyethyl) isocyanurate, caprolactone-modified tris(acryloxyethyl) isocyanurate, and pentaerythritol. Examples include chol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, alkyl-modified dipentaerythritol tri(meth)acrylate, alkyl-modified dipentaerythritol tetra(meth)acrylate, alkyl-modified dipentaerythritol penta(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. Among these, pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, or dipentaerythritol penta(meth)acrylate are preferred. The above monomers and polygomers may be used individually or in combination of two or more.

[0042] In one embodiment, the cured resin used is a cured product of a curable protective layer-forming composition containing a urethane (meth)acrylate oligomer. Using such a resin, a protective layer with favorably adjusted shear strength can be obtained. Examples of urethane (meth)acrylate oligomers include oligomers obtained by reacting a polyol with a polyisocyanate and then reacting it with a (meth)acrylate having a hydroxyl group; oligomers obtained by reacting a polyisocyanate with a (meth)acrylate having a hydroxyl group and then reacting it with a polyol; and oligomers obtained by reacting a polyisocyanate, a polyol, and a (meth)acrylate having a hydroxyl group.

[0043] Examples of polyols include polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and copolymers thereof, ethylene glycol, propylene glycol, 1,4-butanediol, and 2,2'-thiodiethanol.

[0044] Examples of polyisocyanates include isophorone diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, m-phenylene diisocyanate, p-phenylene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,3-xylylene diisocyanate, and 1,4-xylylene diisocyanate.

[0045] Preferably, the above-mentioned composition for forming a curable protective layer contains any suitable photopolymerization initiator. Examples of photopolymerization initiators include benzoin ethers such as benzoin n-butyl ether and benzoin isobutyl ether, benzyl ketals such as benzyl dimethyl ketal and benzyl diethyl ketal, acetophenones such as 2,2-dimethoxyacetophenone and 2,2-diethoxyacetophenone, 1-hydroxycyclohexyl phenyl ketone, [2-hydroxy-2-methyl-1-(4-ethylenephenyl)propan-1-one], 2-hydroxy-2-methyl-1-phenylpropan-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-propan-1-one, and 2-hydroxy-2-methyl-1-(4-isopropylphenyl)propan-1-one. Examples include α-hydroxyalkylphenones such as pan-1-one, α-aminoalkylphenones such as 2-methyl-1-[4-(methylthio)phenyl]-1-morpholinopropane and 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-1-butanone, monoacylphosphine oxides such as 2,4,6-trimethylbenzoyldiphenylphosphine oxide and 2,4,6-trimethylbenzoylphenylethoxyphosphine oxide, and monoacylphosphine oxides such as bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0046] D. Base material The above-mentioned substrate is typically composed of any suitable resin. Examples of resins that make up the above-mentioned substrate include cycloolefin resins, polyimide resins, polyvinylidene chloride resins, polyvinyl chloride resins, polyethylene terephthalate resins, polyethylene naphthalate resins, and the like. Preferably, a cycloolefin resin is used.

[0047] The glass transition temperature of the resin constituting the above substrate is preferably 50°C to 200°C, more preferably 60°C to 180°C, and even more preferably 70°C to 160°C.

[0048] The thickness of the above-mentioned substrate is preferably 8 μm to 500 μm, more preferably 10 μm to 250 μm, even more preferably 10 μm to 150 μm, and particularly preferably 15 μm to 100 μm.

[0049] The total light transmittance of the above substrate is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. Within this range, a transparent conductive film suitable for use as a transparent conductive film in a transparent heater or the like can be obtained.

[0050] The tensile breaking strength of the above-mentioned substrate at 23°C is preferably 30 MPa to 100 MPa, more preferably 50 MPa to 95 MPa, and even more preferably 70 MPa to 90 MPa. According to the present invention, even if a film with poor flexibility is used, it can exhibit sufficient flexibility as a transparent conductive film. The tensile breaking strength is measured at room temperature (23°C) in accordance with JIS K 7161.

[0051] The above-mentioned base material may further contain any suitable additives as needed. Specific examples of additives include plasticizers, heat stabilizers, light stabilizers, lubricants, antioxidants, UV absorbers, flame retardants, colorants, antistatic agents, compatibilizers, crosslinking agents, and thickeners. The type and amount of additives used may be appropriately determined depending on the purpose.

[0052] If necessary, various surface treatments may be performed on the above substrate. Any appropriate method can be used for the surface treatment depending on the purpose. Examples include low-pressure plasma treatment, ultraviolet irradiation treatment, corona treatment, flame treatment, and acid or alkali treatment. In one embodiment, the transparent substrate is surface-treated to make the surface of the transparent substrate hydrophilic. By making the substrate hydrophilic, the processability when coating with a conductive layer-forming composition prepared with an aqueous solvent is improved. Furthermore, a transparent conductive film with excellent adhesion between the substrate and the conductive layer can be obtained. The substrate may also have a multi-layer structure, for example, consisting of a resin film and other layers formed on the resin film.

[0053] E. Method for manufacturing transparent conductive film The above-mentioned transparent conductive film can be manufactured by any suitable method. In one embodiment, a conductive layer-forming composition containing metal nanowires is coated onto a substrate, and then a protective layer-forming composition (polymer liquid) is coated onto it to form the film. Alternatively, the protective layer-forming composition may contain metal nanowires, and the protective layer-forming composition containing metal nanowires may be coated onto the substrate to obtain the transparent conductive film.

[0054] The above-mentioned conductive layer-forming composition may contain any suitable solvent in addition to metal nanowires. The conductive layer-forming composition can be prepared as a dispersion of metal nanowires. Examples of the solvent include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. From the viewpoint of reducing environmental impact, it is preferable to use water. The above-mentioned conductive layer-forming composition may further contain any suitable additives depending on the purpose. Examples of the additives include corrosion inhibitors that prevent corrosion of metal nanowires and surfactants that prevent aggregation of metal nanowires. The type, number, and amount of additives used can be appropriately set depending on the purpose.

[0055] The dispersion concentration of metal nanowires in the above-mentioned conductive layer-forming composition is preferably 0.1% to 1% by weight. Within this range, a conductive layer with excellent conductivity and light transmittance can be formed.

[0056] Any suitable method can be used to apply the above-mentioned conductive layer-forming composition. Examples of application methods include spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, intaglio printing, and gravure printing. Any suitable drying method (e.g., natural drying, forced-air drying, and heat drying) can be used to dry the coated layer. For example, in the case of heat drying, the drying temperature is typically 50°C to 200°C, preferably 80°C to 150°C. The drying time is typically 1 to 10 minutes.

[0057] The above protective layer-forming composition comprises a resin that forms a protective layer, or its precursor (monomer, oligomer). The protective layer-forming composition may further contain any suitable additives as needed. For example, it may contain photopolymerization initiators, coupling agents, etc. The protective layer-forming composition may also further contain any suitable solvent for dilution. Examples of such solvents include toluene, butyl acetate, isobutanol, ethyl acetate, cyclohexane, cyclohexanone, methylcyclohexanone, hexane, acetone, methyl ethyl ketone, methyl isobutyl ketone, propylene glycol monomethyl ether, diethyl ether, ethylene glycol, etc.

[0058] Any suitable method can be used to apply the above-mentioned protective layer-forming composition. Examples of application methods include spray coating, bar coating, roll coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, intaglio printing, gravure printing, and the like.

[0059] When using a curable protective layer-forming composition, a curing treatment is performed after applying the composition. The curing treatment method is chosen according to the composition of the curable protective layer-forming composition. For example, the curing treatment method involves heating and drying the solvent, followed by irradiation at 500 mW / cm² using an ultraviolet irradiator. 2 ~3000mW / cm2 At an irradiation intensity of, the work amount is 50 mJ / cm 2 ~400 mJ / cm 2 The method of irradiating ultraviolet rays can be mentioned.

Example

[0060] Hereinafter, the present invention will be specifically described by way of examples, but the present invention is not limited to these examples. The measurement methods for each characteristic are as follows. Unless otherwise specified, "parts" and "%" in the examples and comparative examples are based on weight. (1) Surface resistance The surface resistance value of the transparent conductive film was measured using "EC-80" manufactured by NAPSON. The measurement temperature was 23°C. (2) Transmittance In the wavelength range of 780 nm to 2500 nm, the transmittance was measured at room temperature using the transmittance measurement mode of "Hitachi Spectrophotometer U-4100" manufactured by Hitachi High-Technologies Corporation. In Table 1, the transmittance at wavelengths 555 nm and 905 nm, the ratio thereof (T905nm / T555nm), and the maximum and minimum transmittances in the range of 900 nm to 1600 nm are shown.

[0061] [Production Example 1] (Synthesis of silver nanowires and preparation of silver nanowire dispersion liquid) In a reaction vessel equipped with a stirrer, at 160°C, 5 ml of anhydrous ethylene glycol, an anhydrous ethylene glycol solution of PtCl2 (concentration: 1.5×10 -40.5 ml of (mol / L) was added. After 4 minutes, 2.5 ml of anhydrous ethylene glycol solution of AgNO3 (concentration: 0.12 mol / L) and 5 ml of anhydrous ethylene glycol solution of polyvinylpyrrolidone (MW: 55000) (concentration: 0.36 mol / L) were simultaneously added dropwise over 6 minutes to the resulting solution. After this addition, the mixture was heated to 160°C and the reaction was carried out for more than 1 hour until the AgNO3 was completely reduced to produce silver nanowires. Next, acetone was added to the reaction mixture containing the silver nanowires obtained as described above until the volume of the reaction mixture was increased fivefold. The reaction mixture was then centrifuged (2000 rpm, 20 minutes) to obtain silver nanowires. The obtained silver nanowires had a short diameter of 30 nm to 40 nm, a long diameter of 30 nm to 50 nm, and a length of 5 μm to 50 μm. Silver nanowire dispersion I was prepared by dispersing the silver nanowire (concentration: 0.2 wt%) and pentaethylene glycol dodecyl ether (concentration: 0.1 wt%) in pure water.

[0062] [Example 1] The silver nanowire dispersion I obtained in Production Example 1 was applied to a substrate (polyethylene terephthalate film, manufactured by Mitsubishi Chemical Corporation, product name "T910E125", thickness 125 μm) using a die coater so that the resistance value after film formation was 100 Ω / □, and the film was formed by heating at 120°C for 2 minutes. Furthermore, a monomer composition with a solid content of 1% by weight was obtained by diluting 1 part by weight of pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300") and 0.1 parts by weight of a photopolymerization initiator (manufactured by BASF, trade name "Irgacure 907") with 59 parts by weight of isopropyl alcohol and 25 parts by weight of diacetone alcohol. This monomer composition was then applied to the silver nanowire ink-coated surface using a spin coater to a dry film thickness of 70 nm, heated at 80°C for 1 minute, and then exposed to a high-pressure mercury lamp with an integrated exposure dose of 200 mJ / cm². 2 By irradiating with ultraviolet light, a transparent conductive film consisting of a substrate, a conductive layer, and a protective layer was obtained.

[0063] [Example 2] A transparent conductive film was obtained in the same manner as in Example 1, except that the silver nanowire dispersion I obtained in Production Example 1 was coated onto a substrate (cycloolefin (norbornene) resin film (manufactured by Zeon Corporation, product name "Zeonor ZF16", thickness 40 μm) using a die coater so that the resistance value after film formation was 37 Ω / □.

[0064] [Example 3] A transparent conductive film was obtained in the same manner as in Example 2, except that the silver nanowire dispersion I obtained in Manufacturing Example 1 was coated using a die coater so that the resistance value after film formation was 25 Ω / □.

[0065] [Example 4] A transparent conductive film was obtained in the same manner as in Example 2, except that the silver nanowire dispersion I obtained in Manufacturing Example 1 was coated using a die coater so that the resistance value after film formation was 20 Ω / □.

[0066] [Example 5] A transparent conductive film was obtained in the same manner as in Example 2, except that the silver nanowire dispersion I obtained in Manufacturing Example 1 was coated using a die coater so that the resistance value after film formation was 18 Ω / □.

[0067] [Example 6] A transparent conductive film was obtained in the same manner as in Example 2, except that the silver nanowire dispersion I obtained in Manufacturing Example 1 was coated using a die coater so that the resistance value after film formation was 13 Ω / □.

[0068] [Comparative Example 1] A sintered target containing indium oxide and tin oxide in a weight ratio of 90:10 or 96.7:3.3 was mounted on a parallel plate type winding magnetron sputtering apparatus. Subsequently, a film was deposited on one side of a substrate (polyethylene terephthalate film, manufactured by Mitsubishi Chemical Corporation, product name "T910E125", thickness 125 μm) by reactive sputtering in an atmosphere of 5.3 × 10⁻¹ Pa consisting of 80% argon gas and 20% oxygen gas. A transparent conductive layer was formed so that the resistance value after film deposition was 40 Ω / □. The light transmittance of the transparent conductive film obtained as described above in the wavelength range of 780 nm to 2500 nm was less than 85%.

[0069] [Table 1]

[0070] As is clear from Table 1, the present invention provides a transparent conductive film with excellent light transmittance in the near-infrared region. The transparent conductive film of the example is suitable, for example, as a component that can efficiently transmit laser light (near-infrared region) necessary for sensing in the field of autonomous driving of vehicles using LiDAR (Light Detection And Ranging). [Explanation of Symbols]

[0071] 10 Base material 20 Conductive layer 30 protective layer 100 Transparent conductive film

Claims

1. A transparent conductive film comprising a substrate and a conductive layer disposed on at least one side of the substrate, The surface resistance of the transparent conductive film is 200 Ω / □ or less. The maximum light transmittance of the transparent conductive film in the wavelength range of 780 nm to 2500 nm is 85% or more. Transparent conductive film.

2. The transparent conductive film according to claim 1, wherein the surface resistance is 100 Ω / □ or less.

3. The transparent conductive film according to claim 1, wherein the ratio of the light transmittance at a wavelength of 905 nm (T905) to the light transmittance at a wavelength of 555 nm (T555) (T905 / T555) is greater than 0.95 and less than or equal to 1.

1.

4. The transparent conductive film according to claim 1, wherein the maximum value of light transmittance in the wavelength range of 900 nm to 1600 nm is 85% or more.

5. The transparent conductive film according to claim 1, wherein the light transmittance at a wavelength of 905 nm is 85% or more.

6. The transparent conductive film according to claim 1, wherein the conductive layer comprises a fibrous conductive material and a polymer matrix.

7. The transparent conductive film according to claim 6, wherein the fibrous conductive material is a metal nanowire.

8. A transparent conductive film according to claim 1, for use with a transparent heater.

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