Transparent conductive film

Abstract

The present application provides a transparent conductive film having excellent light transmittance in the near infrared region. The transparent conductive film of the embodiment of the present application sequentially comprises a conductive layer, a substrate, and a transmittance adjustment layer, the transmittance adjustment layer comprising an ultraviolet curable resin and hollow particles, the hollow particles having a content ratio of 60 parts by weight to 250 parts by weight with respect to 100 parts by weight of the ultraviolet curable resin.

Description

Technical Field

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

[0002] Traditionally, transparent conductive films used as electrodes in touch sensors have often been made by forming metal oxide layers such as indium tin oxide (ITO) layers on a resin film. In recent years, transparent conductive films have also been studied for use as heat-generating elements, for example, as protective covers for cameras and sensors used in autonomous driving systems for purposes such as snow melting and fog prevention. In these applications, excellent conductivity is required, and the light used should preferably be transmissive. Here, in addition to visible light, transmissibility in the near-infrared region is sometimes also required in these applications.

[0003] Existing technical documents Patent documents Patent Document 1: Japanese Patent Publication No. 2009-505358 Summary of the Invention

[0004] The problem that the invention aims to solve The present invention was made to solve the above-mentioned problems, and its main objective is to provide a transparent conductive film with excellent near-infrared light transmittance.

[0005] Methods for solving problems [1] The transparent conductive film of the present invention comprises a conductive layer, a substrate and a transmittance adjustment layer in sequence. The transmittance adjustment layer includes an ultraviolet-curable resin and hollow particles. The content ratio of the hollow particles is 60 to 250 parts by weight relative to 100 parts by weight of the ultraviolet-curable resin.

[0006] [2] According to the transparent conductive film described in [1] above, the ultraviolet-curable resin may be a cured product of a composition for forming a transmittance adjustment layer containing a multifunctional monomer.

[0007] [3] According to the transparent conductive film described in [2] above, the composition for forming the transmittance adjustment layer may contain a multifunctional monomer having four or more reactive functional groups.

[0008] [4] According to any one of [1] to [3] above, the weight average particle size of the hollow particles can be 30 nm to 100 nm.

[0009] Invention Effects According to embodiments of the present invention, a transparent conductive film with excellent transmittance to near-infrared light can be provided. Attached Figure Description

[0010] Figure 1 This is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention. Detailed Implementation

[0011] The embodiments of the present invention will be described below, but the present invention is not limited to these embodiments.

[0012] A. Overall composition of transparent conductive film Figure 1 This is a schematic cross-sectional view of a transparent conductive film according to one embodiment of the present invention. The transparent conductive film 100 sequentially comprises a conductive layer 10, a substrate 20, and a transmittance adjustment layer 30. Although not shown, the transparent conductive film may further include any suitable other layers. Figure 1 The example illustrates a conductive layer 10 comprising a fibrous conductive material 11, but is not limited thereto. The conductive layer may be, for example, a layer made of a metal film or a layer made of a metal oxide film.

[0013] In one embodiment, the transparent conductive film 100 includes a protective layer 40 disposed on the side of the conductive layer 10 opposite to the substrate 20. The protective layer 40 may be a layer protecting the fibrous conductive material 11. In embodiments of the present invention, by providing the protective layer 40, the durability of the conductive layer 10 can be improved. More specifically, conductive layers composed of fibrous conductive materials (e.g., metal nanowires) have characteristics such as low scratch resistance and low humidification durability. As a result, by providing the protective layer, these problems can be eliminated, thereby improving the durability of the conductive layer (which in turn improves the durability of the transparent conductive film). Furthermore, the conductive layer 10 may also contain components constituting the protective layer 40 (e.g., a resin constituting the protective layer).

[0014] The aforementioned transmittance adjustment layer comprises an ultraviolet-curable resin and hollow particles. By having a transmittance adjustment layer containing hollow particles, the refractive index of the transmittance adjustment layer can be preferably adjusted, suppressing interface reflection of the transparent conductive film. As a result, a transparent conductive film with excellent light transmittance can be obtained. In particular, the transparent conductive film of the embodiments of the present invention can be suitably used as a component that enables the efficient transmission of laser light (near-infrared region) required for sensing in the field of autonomous driving of vehicles using LiDAR (Light Detection and Ranging). In one embodiment, the aforementioned transparent conductive film is used in a transparent heater (e.g., a transparent heater for vehicles). The transparent heater can be of any suitable configuration. Typically, the transparent heater can be configured to generate heat by energizing a transparent conductive film provided with a pair of electrodes. In the transparent heater, the aforementioned transparent conductive film is advantageous in that it can be used as a heat source, has excellent near-infrared transmittance, and exhibits sufficient heating even at low voltages.

[0015] In embodiments of the present invention, the content ratio of the hollow particles in the transmittance adjustment layer is 60 to 250 parts by weight relative to 100 parts by weight of the UV-curable resin. Within this range, a transmittance adjustment layer that maintains preferred light transmittance, exhibits excellent slip properties, and is resistant to scratches can be formed. For example, scratches that are easily generated during roll-to-roll processing can be prevented. Furthermore, when the transmittance adjustment layer is in contact with the conductive layer, such as when the transparent conductive film is formed into a roll, damage to the conductive layer can be prevented.

[0016] In one embodiment, the maximum transmittance (T1max) of the transparent conductive film at wavelengths of 780nm to 1600nm and the maximum transmittance (T2max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate at wavelengths of 780nm to 1600nm satisfy the following formula.

[0017] ((T1max-T2max) / T2max)×100≥3% Furthermore, the term "laminar formed of a conductive layer constituting a transparent conductive film and a substrate" refers to a laminate formed of a substrate and a conductive layer disposed on one side of the substrate, and for example, it can be the structure after removing the transmittance adjustment layer from the transparent conductive film. Additionally, in this specification, the value represented by ((T1max-T2max) / T2max)×100 is referred to as the transmittance increase rate caused by the transmittance adjustment layer.

[0018] The percentage of “((T1max-T2max) / T2max)×100” is preferably 3.5% or more, more preferably 4% or more. If it is within such a range, the above effect becomes significant. The upper limit of “((T1max-T2max) / T2max)×100” is, for example, 10%.

[0019] The maximum transmittance (T1max) of the transparent conductive film in the wavelength range of 780 nm to 1600 nm is preferably 85% or more, more preferably 90% or more, and even more preferably 94% or more. A higher maximum transmittance (T1max) of the transparent conductive film in the wavelength range of 780 nm to 1600 nm is preferred, but its upper limit is, for example, 96% (preferably 98%).

[0020] The maximum transmittance (T2max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate is, for example, 80% to 95% at wavelengths of 780 nm to 1600 nm.

[0021] In one embodiment, the maximum transmittance (T3max) of the transparent conductive film at wavelengths of 380nm to 780nm and the maximum transmittance (T4max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate at wavelengths of 380nm to 780nm satisfy the following formula.

[0022] ((T3max-T4max) / T4max)×100≥2% The content of “((T3max-T4max) / T4max)×100” is preferably 2.5% or more, more preferably 3.5% or more. The upper limit of “((T3max-T4max) / T4max)×100” is, for example, 8%.

[0023] The maximum transmittance (T3max) of the transparent conductive film in the wavelength range of 380 nm to 780 nm is preferably 85% or more, more preferably 90% or more, and even more preferably 94% or more. A higher maximum transmittance (T3max) of the transparent conductive film in the wavelength range of 380 nm to 780 nm is preferred, but its upper limit is, for example, 96% (preferably 98%).

[0024] The maximum transmittance (T4max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate is, for example, 80% to 95% at wavelengths of 380 nm to 780 nm.

[0025] The transmittance of the aforementioned transparent conductive film at a wavelength of 905 nm is preferably 85% or more, more preferably 88% or more, and even more preferably 90% or more. Within such a range, a transparent conductive film suitable for transmitting near-infrared laser light can be provided. Higher transmittance at a wavelength of 905 nm is more preferred, but its upper limit is, for example, 95% (preferably 98%).

[0026] The transmittance of the above-mentioned transparent conductive film at a wavelength of 555nm is preferably 80% or more, and more preferably 85% to 95%.

[0027] The haze of the above-mentioned transparent conductive film is preferably 0.1% to 2.5%, more preferably 0.2% to 1.5%.

[0028] The surface resistivity of the aforementioned transparent conductive film 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 / □. In one embodiment, the surface resistivity of the transparent conductive film is 50 Ω / □ or less. Within such a range, a transparent conductive film particularly suitable for use as a transparent heater (especially a transparent heater for vehicles) can be obtained. For example, a heater capable of heating with low voltage can be realized.

[0029] The thickness of the above-mentioned transparent conductive film is preferably 10μm to 500μm, more preferably 15μm to 300μm, and even more preferably 20μm to 200μm.

[0030] In one embodiment, the ratio of the thickness of the substrate to the thickness of the transmittance adjustment layer (substrate thickness / transmittance adjustment layer thickness) is preferably 90 to 800, more preferably 95 to 750. Within this range, reflection of near-infrared light (e.g., light with wavelengths of 780 nm to 1600 nm) can be suppressed, resulting in a transparent conductive film with excellent near-infrared transmittance. In another embodiment, the ratio of the thickness of the substrate to the thickness of the transmittance adjustment layer (substrate thickness / transmittance adjustment layer thickness) is set to 100 or more (preferably 130 or more, more preferably 150 or more). Within this range, a transparent conductive film with minimal interference unevenness can be obtained.

[0031] B. Conductive layer The aforementioned conductive layer can be of any suitable configuration, as long as the effects of the present invention are achieved. In one embodiment, such as... Figure 1 As shown, the conductive layer 10 includes a fibrous conductive material 11. Forming such a conductive layer yields a transparent conductive film with excellent light transmittance, conductivity, and flexibility. The transparent conductive film having a conductive layer including a fibrous conductive material also has excellent heating characteristics; for example, it is preferably used in anti-fog heaters (transparent heaters) for vehicle windows. Examples of fibrous conductive materials include metal nanowires and carbon nanotubes. Metal nanowires are preferred. In one embodiment, the conductive layer includes a fibrous conductive material and a polymer matrix. The fibrous conductive material can be protected by the polymer matrix. As a result, corrosion of the fibrous conductive material can be prevented, resulting in a transparent conductive film with even better durability.

[0032] The thickness of the conductive layer is preferably 50 nm to 300 nm, and more preferably 80 nm to 200 nm.

[0033] (Fiber-based conductive materials) Metal nanowires are preferably used as the aforementioned fiber-based conductive material.

[0034] Metal nanowires are conductive materials made of metal, shaped like needles or filaments, and with a diameter in the nanometer range. Metal nanowires can be straight or curved. When a conductive layer composed of metal nanowires is used, the mesh-like structure allows even a small number of nanowires to form good conductive paths, resulting in a transparent conductive film with low resistance. Furthermore, the mesh-like structure allows openings to be formed between the nanowires, resulting in a transparent conductive film with high light transmittance.

[0035] The ratio of the thickness d to the length L of the aforementioned fibrous conductive material (preferably metal nanowires) (aspect ratio: L / d) is preferably 10 to 100,000, more preferably 50 to 100,000, and particularly preferably 100 to 10,000. Using fibrous conductive materials with a large aspect ratio in this way allows for good cross-linking of the fibrous conductive materials, enabling high conductivity with a small amount of material. As a result, a transparent conductive film with high light transmittance can be obtained. Furthermore, in this specification, the term "thickness of the fibrous conductive material" refers to its diameter when the cross-section of the fibrous conductive material is circular, its minor axis when it is elliptical, and its longest diagonal when it is polygonal. The thickness and length of the fibrous conductive material can be confirmed by scanning electron microscopy or transmission electron microscopy.

[0036] The thickness of the aforementioned fibrous conductive material (preferably metal nanowires) is preferably less than 500 nm, more preferably less than 200 nm, particularly preferably 10 nm to 100 nm, and most preferably 10 nm to 50 nm. Within such a range, a conductive layer with high light transmittance can be formed.

[0037] The length of the aforementioned fiber-based conductive material (preferably metal nanowires) is preferably 1 μm to 1000 μm, more preferably 10 μm to 500 μm, and particularly preferably 10 μm to 100 μm. Within this range, a transparent conductive film with high conductivity can be obtained.

[0038] Any suitable metal can be used as the constituent metal nanowire, as long as it is a conductive metal. Examples of metals constituting the metal nanowire include silver, gold, copper, and nickel. Alternatively, materials formed by plating these metals (e.g., gold plating) can also be used. From the viewpoint of conductivity, silver, copper, or gold are preferred, and silver is more preferred.

[0039] Any suitable method can be used as a method for manufacturing the aforementioned metal nanowires. Examples include: reducing silver nitrate in solution; applying an external voltage or current from the tip of a probe to the surface of a precursor, drawing out metal nanowires from 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 silver salts such as silver nitrate in the presence of polyols such as ethylene glycol and polyvinylpyrrolidone. Uniformly sized silver nanowires can be mass-produced, for example, according to the methods described in Xia, Y. et al., Chem. Mater. (2002), 14, 4736-4745, and Xia, Y. et al., Nano letters (2003), 3(7), 955-960.

[0040] The percentage of the fibrous conductive material (preferably metal nanowires) in the conductive layer relative to the total weight of the conductive layer is preferably 30% to 90% by weight, more preferably 45% to 80% by weight. Within this range, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0041] When the aforementioned metal nanowires are silver nanowires, 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 If the range is as described above, a transparent conductive film with excellent conductivity and light transmittance can be obtained.

[0042] In one embodiment, the conductive layer is patterned. As a patterning method, any suitable method can be used depending on the shape of the conductive layer. The shape of the pattern of the conductive layer can be any suitable shape depending on the application. For example, the patterns described in Japanese Patent Application Publication No. 2011-511357, Japanese Patent Application Publication No. 2010-164938, Japanese Patent Application Publication No. 2008-310550, Japanese Patent Application Publication No. 2003-511799, and Japanese Patent Application Publication No. 2010-541109 can be used. The conductive layer can be patterned using any suitable method according to the shape of the conductive layer after it has been formed on the substrate.

[0043] In one embodiment, the metal nanowires in the conductive layer have a fused mesh structure. The metal nanowires with the fused mesh structure are in a state where they are fused together at their junctions. By forming a conductive layer comprising metal nanowires with a fused mesh structure, a transparent conductive film with higher conductivity can be obtained without compromising transparency.

[0044] The aforementioned conductive layer comprising metal nanowires with a welded mesh structure can be formed, for example, by adding an additive to the metal nanowire dispersion used in forming the conductive layer to promote welding. 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, nitrous acid, sulfuric acid, etc.), and 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, lauryl acid, myristic acid, palmitic acid, stearic acid). The additives include: 2-ethylbutyric acid, 2-methylhexanoic acid, 2-ethylhexanoic acid, 2-propylpentanoic acid, neopentanoic 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 hexadecanoate, silver octadecanoate, silver valerate, silver neopentanoate, 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, metal halides are used, more preferably NaCl, AgF, LiF, NaBr, or NaF. In one embodiment, the conductive layer containing the above-mentioned additives can be formed by coating a metal nanowire dispersion containing the above-mentioned additives and then subjecting it to heat treatment and / or pressure treatment. The temperature for heat treatment is, for example, 50℃ to 200℃.

[0045] The aforementioned conductive layer comprising metal nanowires with a welded mesh structure can also be formed by exposing a coating layer of a metal nanowire dispersion to an acyl halide vapor. Examples of acyl halide vapors include vapors of HCl, HBr, HI, or mixtures thereof.

[0046] Metal nanowires with a fused mesh structure and methods for manufacturing the same are described, for example, in Japanese Patent Application Publication No. 2015-530693. The description in that publication is incorporated herein by reference.

[0047] (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, polyvinyl toluene, polyvinyl xylene, polyimide, polyamide, and polyamide-imide; polyurethane polymers; epoxy polymers; polyolefin polymers; acrylonitrile-butadiene-styrene copolymer (ABS); cellulose; silicone polymers; polyvinyl chloride; polyacetate; polynorbornene; synthetic rubber; and fluorinated polymers. Preferably, a curable resin (preferably a UV-curable resin) made from 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 can be a resin constituting the protective layer (details will be described below).

[0048] The polymer matrix described above can be formed by forming a layer made of a fibrous conductive material on a substrate, coating the layer with a polymer solution, and then drying or curing the coating layer. This operation forms a conductive layer containing the fibrous conductive material within the polymer matrix. The polymer solution contains a polymer constituting the polymer matrix, or a precursor of the polymer (a monomer constituting the polymer). The polymer solution may contain a solvent. Examples of solvents included in the polymer solution include: alcohol solvents, ketone solvents, tetrahydrofuran, hydrocarbon solvents, or aromatic solvents. Preferably, the solvent is volatile. The boiling point of the solvent is preferably below 200°C, more preferably below 150°C, and even more preferably below 100°C.

[0049] (Metallic film conductive layer) The aforementioned conductive layer can be a layer made of a metal film or a layer made of a metal oxide film. Suitable materials for constituting such a conductive layer include metals such as Cu, Al, Fe, Cr, Ti, Si, Nb, In, Zn, Sn, Au, Ag, Co, Cr, Ni, Pb, Pd, Pt, W, Zr, Ta, Hf, Mo, Mn, Mg, and V. Alternatively, alloys or oxides containing two or more of these metals, or with these metals as the main component, can also be used. For example, indium-tin oxide (ITO) can be used.

[0050] C. Transmittance Adjustment Layer The refractive index of the aforementioned transmittance adjustment layer is preferably 1.45 or less, more preferably 1.40 or less, even more preferably 1.30 or less, further preferably 1.25 or less, and particularly preferably 1.20 or less. By setting the transmittance adjustment layer with a refractive index within such a range, interface reflection of the transparent conductive film can be suppressed. As a result, a transparent conductive film with excellent light transmittance can be obtained. The lower the refractive index of the low refractive index layer, the more preferred, but its lower limit is, for example, 1.07 or more (preferably 1.05 or more). The refractive index of the transmittance adjustment layer can be adjusted by containing hollow particles. In this specification, the refractive index refers to the refractive index measured at a wavelength of 550 nm.

[0051] The thickness of the transmittance adjustment layer is preferably 120 nm or more, more preferably 150 nm to 1000 nm, and even more preferably 170 nm to 600 nm. Within this range, reflection of near-infrared light (e.g., light with wavelengths of 780 nm to 1600 nm) can be suppressed, resulting in a transparent conductive film with excellent near-infrared transmittance. Furthermore, a transmittance adjustment layer with excellent sliding properties and resistance to scratches can be formed. In one embodiment, the thickness of the transmittance adjustment layer is set to less than 510 nm (preferably 500 nm or less, more preferably 400 nm or less). Within this range, a transparent conductive film with minimal interference unevenness can be obtained.

[0052] The arithmetic mean surface roughness Ra of the aforementioned transmittance adjustment layer is preferably 1 nm to 50 nm, more preferably 1.2 nm to 40 nm, and even more preferably 1.5 nm to 30 nm. In one embodiment, the arithmetic mean surface roughness Ra of the transmittance adjustment layer is set to 1.5 nm or more. The arithmetic mean surface roughness Ra can be measured according to JIS B 0601.

[0053] The maximum profile height Rz of the aforementioned transmittance adjustment layer is preferably 12 nm or more, more preferably 20 nm or more, and even more preferably 30 nm or more. Within such a range, a transmittance adjustment layer with particularly excellent sliding properties and resistance to scratches can be formed. The upper limit of the maximum profile height Rz of the transmittance adjustment layer can be, for example, 80 nm, 70 nm, or 60 nm. The maximum profile height Rz of the transmittance adjustment layer can be measured according to JIS B 0601-2001.

[0054] (UV-curable resin) As described above, a UV-curable resin is used as the resin constituting the transmittance adjustment layer. Using a UV-curable resin yields a transparent conductive film with excellent scratch resistance. Furthermore, since the transmittance adjustment layer can be formed without heating, damage to the hollow particles can be prevented.

[0055] As the aforementioned UV-curable resins, examples include acrylate-based and / or methacrylate-based resins with curable properties. Examples include: silicone resins, polyester resins, polyether resins, epoxy resins, urethane resins, alkyd resins, spiroacetal resins, polybutadiene resins, polythiol polyolefin resins, and oligomers or prepolymers of polyfunctional compounds such as acrylates or methacrylates from polyols. One type may be used alone, or two or more may be used in combination.

[0056] In one embodiment, the cured product of a transmittance adjustment layer forming composition comprising (meth)acrylate monomers and / or (meth)acrylate oligomers is used as the above-mentioned UV-curable resin. Specific examples of (meth)acrylate monomers and (meth)acrylate oligomers include: trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tetra(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, caprolactone-modified tri(acryloyloxyethyl)isocyanurate, pentaerythritol 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. Preferred monomers include pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, or dipentaerythritol penta(meth)acrylate. Additionally, urethane acrylates may also be used. Examples of urethane acrylates include: phenyl glycidyl ether acrylate hexamethylene diisocyanate urethane prepolymer, pentaerythritol triacrylate hexamethylene diisocyanate urethane prepolymer, and dipentaerythritol pentaacrylate hexamethylene diisocyanate urethane prepolymer. One of the above monomers and oligomers may be used alone, or two or more may be used in combination.

[0057] In one embodiment, the composition for forming the transmittance adjustment layer comprises a multifunctional monomer, preferably a multifunctional acrylate. A multifunctional monomer refers to a monomer having two or more reactive functional groups. A reactive functional group is a functional group that can be cross-linked by ultraviolet radiation, i.e., a functional group having multiple bonds, such as alkenyl, alkynyl, vinyl, acryloyl, methacrylate, allyl, etc. In the composition for forming the transmittance adjustment layer, the content ratio of the multifunctional monomer relative to 100 parts by weight of the monomer component is preferably 50 parts by weight or more, more preferably 70 parts by weight or more, and even more preferably 90 parts by weight or more. In one embodiment, the content ratio of the multifunctional monomer relative to 100 parts by weight of the monomer component is 100 parts by weight.

[0058] In one embodiment, the multifunctional monomer preferably has three or more reactive functional groups, and more preferably four or more reactive functional groups. For example, the upper limit for the number of reactive functional groups in a multifunctional monomer is six.

[0059] The composition for forming the transmittance adjustment layer may contain 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-hydroxycyclohexylphenyl ketone, [2-hydroxy-2-methyl-1-(4-ethylhexyl)prop-1-one], 2-hydroxy-2-methyl-1-phenylprop-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-prop-1-one, 2-hydroxy-2-methyl-1-(4-isoprop-1-one] Alpha-hydroxyalkyl phenyl ketones such as 2-methyl-1-[4-(methylthio)phenyl]-1-morpholinylpropane and 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-1-butanone; monoacylphosphine oxides such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2,4,6-trimethylbenzoyl phenyl ethoxyphosphine oxide; and monoacylphosphine oxides such as bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0060] The composition for forming the transmittance adjustment layer may contain any suitable solvent. Examples of such solvents include MIBK (methyl isobutyl ketone), PGM (propylene glycol monomethyl ether), PMA (propylene glycol monomethyl ether acetate), and TBA (tert-butanol). Mixtures of these solvents may also be used.

[0061] (Hollow particles) As described above, the transmittance adjustment layer contains hollow particles. Examples of such hollow particles include silica particles, acrylic resin particles, and acrylic-styrene copolymer particles. Examples of such silica particles include products manufactured by Nippon Kaisha Chemical Industry Co., Ltd. under the trade names "Thrulya 5320" and "Thrulya 4320".

[0062] The weight-average particle size of the hollow particles can be, for example, 30 nm or more, 40 nm or more, 50 nm or more, 60 nm or more, or 70 nm or more, and can be 150 nm or less, 120 nm or less, 110 nm or less, 100 nm or less, or 80 nm or less. In one embodiment, the weight-average molecular weight of the hollow particles is set to 30 nm to 100 nm. If it is within such a range, a transparent conductive film that preferably maintains light transmittance and has excellent sliding properties can be obtained. The weight-average particle size can be measured by a dynamic light scattering device (DLS). The shape of the hollow particles is not particularly limited; for example, they can be approximately spherical in the form of beads, or they can be amorphous such as powder. Approximately spherical particles are preferred, more preferably approximately spherical particles with an aspect ratio of 1.5 or less, and most preferably spherical particles.

[0063] As described above, the content ratio of the hollow particles is 60 to 250 parts by weight relative to 100 parts by weight of the UV-curable resin. The content ratio of the hollow particles is preferably 100 to 160 parts by weight relative to 100 parts by weight of the UV-curable resin, more preferably 110 to 150 parts by weight, and even more preferably 120 to 150 parts by weight. When the content falls within such a range, the aforementioned effects become apparent.

[0064] The hollowness of the aforementioned hollow particles is preferably 30% to 70%, more preferably 40% to 60%, and even more preferably 40% to 50%. Within this range, a transmittance adjustment layer with a preferably adjusted refractive index can be formed, which maintains preferred light transmittance, exhibits excellent sliding properties, and is not prone to scratches. The hollowness is expressed by the formula: Hollowness = {(Volume of voids) / (Volume of hollow particles)} × 100.

[0065] The transmittance adjustment layer may further comprise solid particles. Examples of such solid particles include silica particles, zirconium oxide particles, and titanium-containing particles (e.g., titanium oxide particles). Examples of such silica particles include those manufactured by Nissan Chemical Industries, Ltd. under the trade names "MEK-2140Z-AC," "MIBK-ST," and "IPA-ST." The weight-average particle size of these solid particles may be 5 nm or more, 10 nm or more, 15 nm or more, 20 nm or more, or 25 nm or more, and may be 330 nm or less, 250 nm or less, 200 nm or less, 150 nm or less, or 100 nm or less. The shape of the solid particles is not particularly limited; for example, they may be approximately spherical in the form of beads, or they may be irregularly shaped such as powder. Approximately spherical particles are preferred, more preferably approximately spherical particles with an aspect ratio of 1.5 or less, and most preferably spherical particles. The amount of the solid particles added is, for example, 100 parts by weight or less, 40 parts by weight or less, or 5 parts by weight or less, relative to 100 parts by weight of the UV-curable resin. In one embodiment, the transmittance adjustment layer does not contain solid particles.

[0066] D. Substrate The aforementioned substrate is typically composed of any suitable resin. Examples of resins constituting the substrate include cyclic olefin resins, polyimide resins, polyvinylidene chloride resins, polyvinyl chloride resins, polyethylene terephthalate resins, and polyethylene naphthalate resins. Cyclic olefin resins are preferred.

[0067] The glass transition temperature of the resin constituting the above-mentioned substrate is preferably 50°C to 200°C, more preferably 60°C to 180°C, and even more preferably 70°C to 160°C.

[0068] The thickness of the above-mentioned substrate is preferably 8μm to 500μm, more preferably 10μm to 250μm, even more preferably 10μm to 150μm, and particularly preferably 15μm to 100μm.

[0069] The total light transmittance of the aforementioned substrate is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more. Within such a range, a transparent conductive film suitable for use as a transparent conductive film in transparent heaters and the like can be obtained.

[0070] 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 when using a film with poor flexibility, it can exhibit sufficient flexibility as a transparent conductive film. The tensile breaking strength is measured at room temperature (23°C) according to JIS K 7161.

[0071] The aforementioned substrate may further include 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 types and amounts of additives used can be appropriately determined according to the purpose.

[0072] Various surface treatments can be applied to the aforementioned substrate as needed. The surface treatment employs any suitable method 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 its surface hydrophilic. If the substrate is made hydrophilic, the processability is excellent when coating a conductive layer forming composition prepared from an aqueous solvent. Furthermore, a transparent conductive film with excellent adhesion between the substrate and the conductive layer can be obtained. Additionally, the substrate can be multilayered, for example, it can be composed of a resin film and other layers formed on the resin film.

[0073] E. Protective layer The thickness of the aforementioned protective layer is preferably 10 nm to 1000 nm, more preferably 60 nm to 800 nm. Within this range, a transparent conductive film with excellent durability can be obtained.

[0074] The combined thickness of the conductive layer and the protective layer is preferably 60 nm to 1000 nm, more preferably 70 nm to 800 nm. Within this range, a transparent conductive film with excellent durability can be obtained.

[0075] Typically, the protective layer described above is composed of resin. Any suitable resin can be used as the resin constituting the protective layer, as long as the effects of the present invention are achieved. Examples of such resins include: acrylic resins; polyester resins such as polyethylene terephthalate; aromatic resins such as polystyrene, polyvinyl toluene, polyvinyl xylene, polyimide, polyamide, and polyamide-imide; polyurethane resins; epoxy resins; polyolefin resins; acrylonitrile-butadiene-styrene copolymer (ABS); cellulose; silicone resins; polyvinyl chloride; polyacetate; polynorbornene; synthetic rubber; and fluorinated resins.

[0076] In one embodiment, a curable resin (e.g., an active energy line curable resin, a thermosetting resin) is used as the resin for forming the above-mentioned protective layer. The protective layer composed of the curable resin can be formed by curing the curable protective layer forming composition.

[0077] In one embodiment, a cured composition comprising (meth)acrylate monomers and / or (meth)acrylate oligomers is used as the curable resin described above. Using such a resin yields a protective layer with preferably adjusted shear strength. Specific examples of (meth)acrylate monomers and (meth)acrylate oligomers include: trimethylolpropane tri(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, propylene oxide-modified trimethylolpropane tri(meth)acrylate, trimethylolpropane tetra(meth)acrylate, tri(acryloyloxyethyl)isocyanurate, caprolactone-modified tri(acryloyloxyethyl)isocyanurate, pentaerythritol 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. The preferred monomers are pentaerythritol tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, or dipentaerythritol penta(meth)acrylate. One of the monomers and oligomers may be used alone, or two or more may be used in combination.

[0078] In one embodiment, the cured product of a composition for forming a curable protective layer containing urethane (meth)acrylate oligomers is used as the aforementioned curable resin. Using such a resin yields a protective layer with preferably adjusted shear strength. Examples of urethane (meth)acrylate oligomers include: oligomers obtained by reacting a polyol with a polyisocyanate followed by reacting a hydroxyl-containing (meth)acrylate; oligomers obtained by reacting a polyisocyanate with a hydroxyl-containing (meth)acrylate followed by reacting a polyol; and oligomers obtained by reacting a polyisocyanate, a polyol, and a hydroxyl-containing (meth)acrylate.

[0079] Examples of polyols include: polyethylene glycol, polypropylene glycol, polytetramethylene ether glycol and their copolymers, ethylene glycol, propylene glycol, 1,4-butanediol, 2,2'-thiodiethanol, etc.

[0080] Examples of polyisocyanates include: isophorone diisocyanate, 2,4-toluene diisocyanate, 2,6-toluene diisocyanate, m-phenylene diisocyanate, terephthalene diisocyanate, hexamethylene diisocyanate, trimethylhexamethylene diisocyanate, 4,4'-diphenylmethane diisocyanate, hydrogenated diphenylmethane diisocyanate, 1,3-phenylenedimethyl diisocyanate, 1,4-phenylenedimethyl diisocyanate, etc.

[0081] 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-hydroxycyclohexylphenyl ketone, [2-hydroxy-2-methyl-1-(4-ethylhexyl)prop-1-one], 2-hydroxy-2-methyl-1-phenylprop-1-one, 1-[4-(2-hydroxyethoxy)phenyl]-2-hydroxy-2-methyl-1-prop-1-one, 2-hydroxy-2-methyl-1-(4-isoprop-1-one) Alpha-hydroxyalkyl phenyl ketones such as 2-methyl-1-[4-(methylthio)phenyl]-1-morpholinylpropane and 2-benzyl-2-dimethylamino-1-(4-morpholinylphenyl)-1-butanone; monoacylphosphine oxides such as 2,4,6-trimethylbenzoyl diphenylphosphine oxide and 2,4,6-trimethylbenzoyl phenyl ethoxyphosphine oxide; and monoacylphosphine oxides such as bis(2,6-dimethoxybenzoyl)-2,4,4-trimethylpentylphosphine oxide and bis(2,4,6-trimethylbenzoyl)phenylphosphine oxide.

[0082] F. Manufacturing method of transparent conductive film The aforementioned transparent conductive film can be manufactured using any suitable method. In one embodiment, a transparent conductive film is obtained by coating a transmittance adjustment layer forming composition on one side of a substrate and a conductive layer forming composition on the other side of the substrate. When the transparent conductive film has a protective layer, a transparent conductive film is obtained by coating a protective layer forming composition (polymer liquid) after forming the conductive layer by coating the conductive layer forming composition. Alternatively, the protective layer forming composition may contain metal nanowires, and the protective layer forming composition containing metal nanowires may be coated onto a substrate to obtain a transparent conductive film.

[0083] In one embodiment, the conductive layer forming composition comprises the aforementioned fibrous conductive material. In addition to the fibrous conductive material, the conductive layer forming composition may contain any suitable solvent. The conductive layer forming composition can be prepared in the form of a dispersion of the fibrous conductive material. Examples of such solvents include water, alcohol-based solvents, ketone-based solvents, ether-based solvents, hydrocarbon-based solvents, and aromatic solvents. From the viewpoint of reducing environmental impact, water is preferred. The conductive layer forming composition may further contain any suitable additives depending on the purpose. Examples of such additives include, for instance, corrosion-resistant materials that prevent corrosion of the fibrous conductive material, and surfactants that prevent aggregation of the fibrous conductive material. The type, quantity, and amount of additives used can be appropriately determined according to the purpose.

[0084] The dispersion concentration of the fibrous conductive material in the above-mentioned conductive layer forming composition is preferably 0.1% to 1% by weight. If it is within such a range, a conductive layer with excellent conductivity and light transmittance can be formed.

[0085] As a coating method for the above-mentioned conductive layer forming composition, any suitable method can be used. Examples of coating methods include: spraying, bar coating, roller coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, gravure printing, photogravure printing, etc. As a drying method for the coating layer, any suitable drying method can be used (e.g., natural drying, air drying, heat drying). 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.

[0086] The conductive layer (e.g., a layer made of a metal film or a layer made of a metal oxide film) can be formed by any suitable film-forming method (e.g., vacuum evaporation, sputtering, CVD, ion plating, spraying, etc.). This film-forming method is known to those skilled in the art, and therefore detailed descriptions are omitted.

[0087] The composition for forming the transmittance adjustment layer described above uses the composition described in section C. The concentration of the solid components in the composition for forming the transmittance adjustment layer is, for example, 0.1% to 20% by weight, preferably 1% to 10% by weight.

[0088] As a coating method for the above-mentioned transmittance adjustment layer composition, any suitable method can be used. Examples of coating methods include: spraying, rod coating, roller coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, gravure printing, photogravure printing, etc. As a drying method for the coating layer, any suitable drying method can be used (e.g., natural drying, air drying, heat drying). 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.

[0089] When using a transmittance adjustment layer forming composition containing a curable resin, a curing process is performed after coating the transmittance adjustment layer forming composition. As a method for curing, any suitable method can be used depending on the composition of the transmittance adjustment layer forming composition. For example, a method for curing can be described as follows: after heating and drying the coated layer, use an ultraviolet irradiator at 500 mW / cm². 2 ~3000mW / cm 2 The irradiation intensity and cumulative irradiation energy are 50–400 mJ / cm². 2 Ultraviolet rays.

[0090] The protective layer forming composition described above comprises a resin or its precursor (monomer, oligomer) for forming a protective layer. The protective layer forming composition may further comprise any suitable additives as needed. For example, it may contain a photopolymerization initiator, coupling agent, etc. Additionally, the protective layer forming composition may further comprise 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.

[0091] As a coating method for the composition for forming the above-mentioned protective layer, any suitable method can be used. Examples of coating methods include: spraying, bar coating, roller coating, die coating, inkjet coating, screen coating, dip coating, letterpress printing, gravure printing, photogravure printing, etc.

[0092] When using a curable protective layer forming composition, a curing process is performed after coating the composition. As a method for curing, any suitable method can be used depending on the composition of the curable protective layer forming composition. For example, a curing process can be performed by heating and drying the solvent, followed by irradiation with an ultraviolet light machine at 500 mW / cm². 2 ~3000mW / cm 2 The irradiation intensity and cumulative irradiation energy are 50–400 mJ / cm². 2 Ultraviolet rays.

[0093] Example The present invention will now be specifically described through examples, but the invention is not limited to these examples. The methods for measuring each characteristic are shown below. Furthermore, unless otherwise stated, "parts" and "%" in the examples and comparative examples are based on weight.

[0094] (1) Surface resistance The surface resistivity of the transparent conductive film (conductive layer) was measured using a NAPSON product, trade name "EC-80". The measurement temperature was set to 23°C.

[0095] (2) Transmittance The transmittance of a specified wavelength range was measured at room temperature using the transmittance measurement mode of the Hitachi High-Tech Science U-4100 spectrophotometer.

[0096] The evaluation samples were set as transparent conductive films and laminates obtained by removing the transmittance adjustment layer from the transparent conductive films (laminates formed by conductive layers and substrates). The increase in transmittance caused by the transmittance adjustment layer was calculated based on the transmittance of each sample.

[0097] Specifically, the maximum transmittance (T1max) of the transparent conductive film in the wavelength range of 780nm to 1600nm and the maximum transmittance (T2max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate in the wavelength range of 780nm to 1600nm are measured. The increase rate of transmittance caused by the transmittance adjustment layer in the wavelength range of 780nm to 1600nm is calculated by the formula ((T1max-T2max) / T2max)×100.

[0098] In addition, the maximum transmittance (T3max) of the transparent conductive film in the wavelength range of 380nm to 780nm and the maximum transmittance (T4max) of the laminate formed by the conductive layer constituting the transparent conductive film and the substrate in the wavelength range of 380nm to 780nm were measured. The increase rate of transmittance caused by the transmittance adjustment layer in the wavelength range of 380nm to 780nm was calculated by the formula ((T3max-T4max) / T4max)×100.

[0099] (3) Arithmetic mean surface roughness Ra The arithmetic mean surface roughness Ra of a 5 μm × 5 μm region on the surface of the transmittance adjustment layer was measured using a scanning probe microscope “NanoscopeIV” AFM tapping mode manufactured by Veeco Instruments.

[0100] (4) Coefficient of kinetic friction Using the trade name "TSf-503" manufactured by Kyowa Interface Chemical Co., Ltd., and in accordance with JIS K7125:1999, the sample (transmittance adjustment layer) size on the contact side was 1 cm□, the measurement load was 100 g, the measurement speed was 1 mm / s, the measurement distance was 30 mm, and the measurement temperature was 23 °C. The sliding plate (bottom surface: felt) was slid against the transmittance adjustment layer, and the coefficient of friction (static friction coefficient) at the start of sliding was measured.

[0101] (5) Anti-adhesion A cyclic olefin polymer film (COP film, manufactured by Zeon Corporation, Japan) was deposited on the surface of the transmittance adjustment layer of the transparent conductive film. A load was applied by finger pressure, and the film's adhesion was evaluated. Cases where the COP film was completely not adhered to the transparent conductive film, or where the COP film was slightly adhered but immediately peeled off, were evaluated as "OK". Cases where the COP film adhered but did not peel off were evaluated as "NG".

[0102] [Example 1] <1. Preparation of a composition for forming a transmittance adjustment layer> A transmittance adjustment layer forming composition (coating liquid) with a solid content concentration of 3.5% by weight was prepared by mixing 100 parts by weight of pentaerythritol triacrylate (manufactured by Osaka Organic Chemical Industry Co., Ltd., trade name "Viscoat #300"), 120 parts by weight of hollow particles (manufactured by Nichibukai Catalyst Chemicals Co., Ltd., trade name: OMNIRAD2959), 10 parts by weight of photopolymerization initiator (manufactured by BASF Co., Ltd., trade name: OMNIRAD2959) and a mixed solvent of MIBK and PGM (MIBK:PGM (weight ratio) = 1:3).

[0103] <2. Manufacturing of the substrate and transmittance adjustment layer laminate> The above-mentioned transmittance adjustment layer forming composition was coated onto a substrate (polyethylene terephthalate film, manufactured by Toray Industries, Inc., product name "Lumirror#50", thickness 50 μm). A die-coating machine was used for coating. Using the die-coating machine, the above-mentioned transmittance adjustment layer forming composition (coating liquid) was coated onto one side of the PET film to form a coating film. Subsequently, after heating at 80°C for 1 minute, the film was irradiated with a high-pressure mercury lamp with a cumulative exposure of 200 mJ / cm². 2 The laminate, consisting of a substrate and a transmittance adjustment layer, is manufactured using ultraviolet light. Furthermore, the transmittance adjustment layer has a thickness of 170 nm.

[0104] <3. Fabrication of Transparent Conductive Films> In a parallel-plate type roll-up magnetron sputtering apparatus, a sintered target containing indium oxide and tin oxide at a weight ratio of 90:10 or 96.7:3.3 is mounted. Subsequently, a 5.3 × 10⁻⁶ m³ / h column of argon gas and oxygen gas is sputtered. -1 In an atmosphere of Pa, a conductive layer is formed by reactive sputtering on the opposite side of the transmittance adjustment layer of the above-mentioned substrate / transmittance adjustment layer laminate. The resistivity of the film after film formation is 15Ω / □.

[0105] The transparent conductive film obtained in the manner described above was used for the above evaluation. The results are shown in Table 1.

[0106] [Example 2] The amount of hollow particles was set to 150 parts by weight, and otherwise, a transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was used for the above evaluation. The results are shown in Table 1.

[0107] [Example 3] The amount of hollow particles was set to 80 parts by weight, and otherwise, a transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was used for the above evaluation. The results are shown in Table 1.

[0108] [Comparative Example 1] The amount of hollow particles was set to 50 parts by weight, and otherwise, a transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was used for the above evaluation. The results are shown in Table 1.

[0109] [Comparative Example 2] Without the addition of hollow particles, a transparent conductive film was obtained in the same manner as in Example 1. The obtained transparent conductive film was then subjected to the above evaluation. The results are shown in Table 1.

[0110] Table 1

[0111] Symbol Explanation 10: Substrate 20: Conductive layer 30: Transmittance Adjustment Layer 40: Protective layer 100: Transparent conductive film

Claims

1. A transparent conductive film, comprising sequentially a conductive layer, a substrate, and a transmittance adjustment layer, The transmittance adjustment layer comprises UV-curable resin and hollow particles. The hollow particles are present in a ratio of 60 to 250 parts by weight relative to 100 parts by weight of the UV-curable resin.

2. The transparent conductive film according to claim 1, wherein, The UV-curable resin is a cured product of a composition for forming a transmittance adjustment layer containing multifunctional monomers.

3. The transparent conductive film according to claim 2, wherein, The composition for forming the transmittance adjustment layer comprises a multifunctional monomer having four or more reactive functional groups.

4. The transparent conductive film according to any one of claims 1 to 3, wherein, The weight-average particle size of the hollow particles is 30 nm to 100 nm.

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