Silver nanowire-containing laminate and method for producing same

Abstract

[Problem] The present invention addresses the problem of providing: a silver nanowire-containing laminate which has a silver nanowire-containing layer having a high sheet resistance, has better dispersibility of silver nanowires than conventional methods, and can lower near-infrared transmittance while maintaining visible light transmittance; and a method for producing the same. [Solution] Disclosed is a silver nanowire-containing laminate which has a silver nanowire-containing layer that contains silver nanowires and a cured product of a polymerizable component that includes 30 mass% or more of a polymerizable monomer and / or a macromonomer having a hydroxyl group, wherein the mass ratio of the silver nanowires with respect to the polymerizable component is 0.20 to 1.5. This silver nanowire-containing laminate has a ratio of the visible light transmittance to the near-infrared transmittance of 0.85 or less.

Description

Silver nanowire-containing laminate and method for producing same

[0001] The present invention relates to a silver nanowire-containing laminate and a method for producing the same.

[0002] In recent years, there has been a strong demand for products that contribute to energy conservation as part of efforts to reduce greenhouse gas emissions. One such product is the need to provide windows with heat-shielding and heat-insulating properties, as this would reduce the air-conditioning load in buildings and automobiles.

[0003] Methods for providing windows with heat-shielding and heat-insulating properties include forming a film on the window glass that blocks infrared rays, which are heat rays, or applying an infrared-blocking film to the window glass. Patent Document 1, for example, describes a heat-insulating film known as a Low-E film, which uses a precious metal film and takes advantage of the low infrared radiation resulting from the high reflectivity of far-infrared rays. However, such far-infrared reflective films are produced by dry coating methods such as sputtering, which poses problems in terms of production speed and manufacturing costs.

[0004] On the other hand, silver nanowires are one example of a material that can be imparted with heat insulation properties by a wet coating method. For example, Patent Document 2 reports that a heat ray reflective layer can be formed by applying a silver nanowire dispersion using polyvinyl alcohol as a binder, thereby producing a heat ray shielding film with excellent heat insulation properties that exhibits high visible light transmittance while reflecting and preventing heat rays emitted from heating and other sources from escaping and preventing outside heat from entering the room. However, this binder has issues in terms of substrate adhesion. Furthermore, Patent Document 3 reports a heat ray shielding material using silver nanowires that has excellent durability due to the use of a polymerizable monomer as a binder.

[0005] As described above, although silver nanowires have heat insulating properties due to their high far-infrared reflectivity, they have issues with their near-infrared light blocking performance. Increasing the amount of silver nanowires used to reduce near-infrared light transmittance not only reduces visible light transmittance, but also has the disadvantage of increasing the conductivity of the silver nanowire-containing layer and reducing radio wave transmittance.

[0006] In particular, near-infrared rays in the range of 1500 nm to 2100 nm are known to have a large impact on the burning sensation caused by sunlight, and there has been a demand for a heat-shielding film made of silver nanowires that has higher near-infrared blocking performance in the range of 1500 nm to 2100 nm while maintaining visible light transmittance compared to conventional heat-shielding films made of silver nanowires.

[0007] Furthermore, with regard to the heat ray-shielding material disclosed in Patent Document 3 that uses a polymerizable monomer as a binder for the conductive particle-containing layer, when a polymerizable monomer such as that described in the examples of Patent Document 3 is used, it has been confirmed that the dispersibility of silver nanowires in the polymerizable monomer is low, and as the monomer concentration increases, the silver nanowires begin to aggregate with each other. This phenomenon raises concerns about the occurrence of defects and skinning during the deposition and drying of the conductive particle-containing layer, and therefore needed to be improved.

[0008] JP 63-134232 A JP 2012-252172 A JP 2017-32775 A

[0009] In view of the problems in the conventional technology described above, the present invention aims to provide a silver nanowire-containing laminate and a method for producing the same, in which the silver nanowire-containing layer has good adhesion to the substrate, the sheet resistance of the silver nanowire-containing layer is high, concerns about the dispersibility of silver nanowires are eliminated compared to conventional methods, and near-infrared transmittance can be reduced while maintaining visible light transmittance.

[0010] As a result of intensive research conducted by the inventors to solve the above-mentioned problems, they discovered that the above-mentioned problems can be solved by using a cured product of a polymerizable component containing a polymerizable monomer and / or macromonomer having a hydroxyl group, and further by setting the mass ratio of the polymerizable component to silver nanowires to a specific ratio, and thus completed the present invention.

[0011] That is, the present invention provides: <1> a substrate; and a silver nanowire-containing layer containing silver nanowires having an average minor axis length of 10 to 50 nm and an average major axis length of 2 to 20 μm and a cured product of a polymerizable component, wherein the sheet resistance of the silver nanowire-containing layer is 1.0×10 ３a silver nanowire-containing laminate having a far-infrared reflectance of 50% or more; a silver nanowire-containing layer having a far-infrared reflectance of 50% or more; a silver nanowire-containing layer having a far-infrared reflectance of 1.0×10 ... ３ A method for producing a silver nanowire-containing laminate having a silver nanowire-containing layer with a transmittance of Ω / □ or more, the method comprising the steps of: applying a silver nanowire-containing composition containing silver nanowires having an average minor axis length of 10 to 50 nm and an average major axis length of 2 to 20 μm, a polymerizable component, and a solvent to form a silver nanowire-containing layer; and curing the polymerizable component in the silver nanowire-containing layer with active energy rays, wherein the polymerizable component contained in the silver nanowire-containing composition contains a total of 30 mass% or more of polymerizable monomers and macromonomers having a hydroxyl group, and the mass ratio of the silver nanowires to the polymerizable component is 0.20 to 1.5; and the resulting silver nanowire-containing laminate has a ratio of visible light transmittance to near-infrared transmittance of 0.85 or less.

[0012] According to the present invention, the dispersibility of silver nanowires and the adhesion of the silver nanowire-containing layer to the substrate are better than those achieved by conventional methods, and it is possible to obtain a silver nanowire-containing heat-shielding material that has reduced near-infrared transmittance while maintaining a certain level of sheet resistance or higher to ensure visible light transmittance and radio wave transmittance.

[0013] The present invention will be described in detail below.

[0014] [Substrate] The substrate in the present invention can be any substrate obtained by a known method or commercially available, without particular limitations. Specific examples of substrate materials include glass, polyimide, polycarbonate, polyethersulfone, polyacrylate, polyester, polyethylene terephthalate, polyethylene naphthalate, polyolefin, and polyvinyl chloride. An organic functional material and an inorganic functional material may be further formed on the substrate. Multiple substrates may also be laminated. The substrate is preferably optically transparent, preferably having a visible light transmittance of 70% or more, more preferably 80% or more.

[0015] [Silver Nanowires] In the present invention, "silver nanowires" refers to silver structures having a minor axis length of less than 1 μm and an aspect ratio (major axis length / minor axis length) of 10 or more. There are no particular limitations on the method for producing the silver nanowires used in the present invention, and those obtained by known production methods can be used. Among these, it is preferable to use a production method in which silver nanowires are obtained by reducing a silver salt in a polyol in the presence of a growth inhibitor and a halide salt.

[0016] When silver nanowires are used as a transparent heat-shielding film, a small average short axis length of the wires is advantageous and preferable in order to enhance transparency. In the present invention, the "short axis length of silver nanowires" refers to the short axis length measured using a scanning electron microscope (SEM; JEOL Ltd., JSM-5610LV). Furthermore, the "average short axis length of silver nanowires" refers to the average value of the short axis lengths measured by observing 100 or more silver nanowires. In the present invention, the average short axis length of silver nanowires is required to be 50 nm or less, preferably 40 nm or less, more preferably 30 nm or less, and even more preferably 25 nm or less. On the other hand, since a larger average short axis length of silver nanowires increases durability under high-temperature and high-humidity conditions, the average short axis length of silver nanowires is preferably 10 nm or more, and even more preferably 15 nm or more.

[0017] It is known that the infrared blocking performance of silver nanowires is due to the anisotropy of the silver nanowires in the long axis direction, i.e., the long axis length exceeds the nanometer size. Therefore, from the perspective of infrared blocking, the average long axis length of the nanowires must be at least a certain length. On the other hand, nanowires that are too long tend to become tangled, reducing dispersion stability. In addition, the increased contact between silver nanowires tends to reduce sheet resistance, so short nanowires are preferred. In this specification, the "long axis length of silver nanowires" refers to the value calculated by photographing silver nanowires using a dark-field microscope (product name: BX51, manufactured by Olympus Corporation) and using image processing software (product name: Image-Pro Premier, manufactured by Media Cybernetics, Inc.). Furthermore, the "average long axis length of silver nanowires" refers to the average long axis length measured by observing 1,000 or more silver nanowires. In the present invention, the average major axis length of the silver nanowires is required to be 2 to 20 μm, preferably 2 to 14 μm, more preferably 2 to 8 μm, and even more preferably 2 to 4 μm.

[0018] [Cured Product of Polymerizable Component] The polymerizable component of the present invention is a compound that undergoes a polymerization reaction upon irradiation with active energy rays such as ultraviolet light, visible light, or electron beams, either directly or through the action of an initiator, to give a cured product. The present invention is characterized in that the polymerizable component contains a polymerizable monomer and / or macromonomer having a hydroxyl group. When cured, the polymerizable component adheres the silver nanowires to the base and prevents contact between the silver nanowires, thereby increasing the sheet resistance of the silver nanowire-containing layer.

[0019] The dispersibility of silver nanowires can be improved by including a polymerizable monomer and / or macromonomer having a hydroxyl group in the polymerizable component. The polymerizable monomer and macromonomer having a hydroxyl group are monomers and macromonomers that undergo a polymerization reaction when irradiated with visible light or active energy rays such as ultraviolet light or electron beams, either directly or through the action of an initiator, and are not particularly limited as long as they have at least one hydroxyl group in the molecule. However, since the greater the number of hydroxyl groups per molecular weight, the better the dispersibility of silver nanowires, so the number of hydroxyl groups per molecular weight is preferably 1 / 3000 or more, more preferably 1 / 2000 or more, and even more preferably 1 / 1000 or more. Specific examples of polymerizable monomers having a hydroxyl group include 2-hydroxyethyl (meth)acrylate, 2-hydroxypropyl (meth)acrylate, 4-hydroxybutyl (meth)acrylate, polyethylene glycol mono(meth)acrylate, polypropylene glycol mono(meth)acrylate, 2-hydroxy-3-phenoxypropyl (meth)acrylate, N-(2-hydroxyethyl) (meth)acrylamide, pentaerythritol tri(meth)acrylate, dipentaerythritol penta(meth)acrylate, ethylene oxide-modified isocyanuric acid di(meth)acrylate, and bisphenol A diglycidyl ether (meth)acrylic acid adduct. Specific examples of macromonomers having a hydroxyl group include polymerizable epoxy resins and polymerizable acrylic resins having an average of one or more polymerizable unsaturated groups per molecule and an average of one or more hydroxyl groups per molecule. Among these, from the viewpoint of radical polymerizability, polymerizable monomers and / or macromonomers having a hydroxyl group and a (meth)acryloyl group are preferred.

[0020] As the polymerizable component, in addition to the polymerizable monomer and / or macromonomer having a hydroxyl group, a polymerizable monomer and / or macromonomer not having a hydroxyl group can be used in combination. The polymerizable monomer and / or macromonomer not having a hydroxyl group is not particularly limited as long as it is a monomer and / or macromonomer that undergoes a polymerization reaction upon irradiation with visible light or active energy rays such as ultraviolet light or electron beams, either directly or through the action of an initiator. Specific examples of the polymerizable monomer include (meth)acrylic acid, methyl (meth)acrylate, ethyl (meth)acrylate, butyl (meth)acrylate, 2-ethylhexyl (meth)acrylate, cyclohexyl (meth)acrylate, phenoxyethyl (meth)acrylate, methoxy-diethylene glycol (meth)acrylate, methoxy-triethylene glycol (meth)acrylate, and other (meth)acrylic acid esters; aromatic vinyls such as styrene and methylstyrene; carboxylic acid vinyl esters such as vinyl acetate; (meth)acrylamide, N-isopropyl (meth)acrylate, Examples of suitable macromonomers include (meth)acrylamides such as methylolpropane tri(meth)acrylate and N,N-dimethyl(meth)acrylamide, polyethylene glycol di(meth)acrylate, trimethylolpropane tri(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethylene oxide-modified bisphenol A di(meth)acrylate, ethylene oxide-modified trimethylolpropane tri(meth)acrylate, and ethylene oxide-modified isocyanuric acid tri(meth)acrylate. Specific examples of suitable macromonomers include polymerizable urethane acrylate resins, polymerizable acrylic resins, and polymerizable polyester resins having an average of one or more polymerizable unsaturated groups per molecule. These may be used alone or in combination of two or more.

[0021] [Silver Nanowire-Containing Layer] The silver nanowire-containing layer of the present invention contains at least silver nanowires and a cured product of a polymerizable component. The silver nanowire-containing layer is formed by applying a silver nanowire-containing composition described below onto a substrate, drying it, and curing it.

[0022] [Sheet Resistance of Silver Nanowire-Containing Layer] The sheet resistance of the silver nanowire-containing layer of the present invention is set to 1.0×10 ３ The higher the sheet resistance of the silver nanowire-containing layer, the better the radio wave transmittance. ４ The upper limit of the sheet resistance of the silver nanowire-containing layer is not particularly limited, but is generally 1.0×10 2０ Ω / □ or less.

[0023] [Proportion of Silver Nanowires in the Silver Nanowire-Containing Layer] In the present invention, the proportion of silver nanowires in the silver nanowire-containing layer must be 15 to 60% by mass. By making the proportion of silver nanowires in the silver nanowire-containing layer 15% by mass or more, the far-infrared reflectance of the silver nanowires can be increased. Furthermore, by making the proportion of silver nanowires in the silver nanowire-containing layer 60% by mass or less, the sheet resistance of the silver nanowire-containing layer can be maintained high, thereby increasing radio wave transmittance. The proportion of silver nanowires in the silver nanowire-containing layer is preferably 20% by mass or more, more preferably 24% by mass or more, and even more preferably 28% by mass or more. Furthermore, the proportion of silver nanowires in the silver nanowire-containing layer is preferably 50% by mass or less, more preferably 45% by mass or less, and even more preferably 40% by mass or less.

[0024] [Visible Light Transmittance of Silver Nanowire-Containing Laminate] The higher the visible light transmittance of the silver nanowire-containing laminate, the more improved the transparency, and therefore, the more preferable. The visible light transmittance in the present invention is defined as the total light transmittance measured by a method in accordance with JIS K 7361-1. The visible light transmittance of the silver nanowire-containing laminate is preferably 60% or more, more preferably 70% or more, and even more preferably 75% or more.

[0025] [Near-infrared transmittance of silver nanowire-containing laminate] The near-infrared transmittance in the present invention refers to the average transmittance of infrared rays in the range of 1500 to 2100 nm. The near-infrared transmittance of the silver nanowire-containing laminate is preferably low from the viewpoint of suppressing the burning sensation caused by sunlight. The near-infrared transmittance of the silver nanowire-containing laminate is preferably 75% or less, more preferably 70% or less, and even more preferably 65% ​​or less.

[0026] [Ratio of visible light transmittance to near-infrared transmittance of silver nanowire-containing laminate] The ratio of visible light transmittance to near-infrared transmittance of the silver nanowire-containing laminate can be used as an index of compatibility between the transparency and near-infrared shielding properties of the silver nanowire-containing laminate, with a lower value indicating that the silver nanowire-containing laminate is able to block near-infrared while maintaining transparency. In the present invention, the ratio of visible light transmittance to near-infrared transmittance of the silver nanowire-containing laminate is required to be 0.85 or less, preferably 0.80 or less, and more preferably 0.77 or less. The ratio of visible light transmittance to near-infrared transmittance of the silver nanowire-containing laminate can be calculated by (near-infrared transmittance of silver nanowire-containing laminate) / (visible light transmittance of silver nanowire-containing laminate).

[0027] [Far-infrared reflectance of silver nanowire-containing laminate] The higher the far-infrared reflectance of the silver nanowire-containing laminate, the better the thermal insulation, and therefore the more preferable. In the present invention, the far-infrared reflectance refers to the average value of the relative reflectance of infrared rays at 2.5 to 25 μm relative to an Al mirror. The far-infrared reflectance of the silver nanowire-containing laminate is preferably 50% or more, more preferably 60% or more, and even more preferably 70% or more.

[0028] [Step of Forming a Silver Nanowire-Containing Layer] The method for producing a silver nanowire-containing laminate of the present invention includes a step of applying a silver nanowire-containing composition to a substrate to form a silver nanowire-containing layer. Specific examples of the application method include spin coating, slit coating, dip coating, blade coating, bar coating, spraying, letterpress printing, intaglio printing, screen printing, lithographic printing, dispensing, and inkjet printing. These application methods may also be used to apply the silver nanowire-containing composition multiple times.

[0029] [Silver Nanowire-Containing Composition] The silver nanowire-containing composition of the present invention contains at least silver nanowires, a polymerizable component, and a solvent. Various additives can be used in combination with the silver nanowire-containing composition as needed, provided that the effects of the present invention are not impaired. Specific examples of additives include non-photosensitive resins, dispersants, leveling agents, refractive index modifiers, and agents for preventing deterioration of silver nanowires.

[0030] [Silver Nanowire Concentration] The silver nanowire concentration in the silver nanowire-containing composition used in the present invention can be set as desired, but from the viewpoint of dispersion stability, it is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and even more preferably 2.0% by mass or less. Furthermore, if the silver nanowire concentration is extremely low, in order to obtain the desired infrared blocking performance during coating, the coating thickness must be increased or multiple coatings must be applied, which increases the effort required during use. Therefore, from the viewpoint of productivity, the silver nanowire concentration is preferably 0.01% by mass or more, more preferably 0.05% by mass or more, even more preferably 0.10% by mass or more, and particularly preferably 0.20% by mass or more.

[0031] [Solvent for Silver Nanowire-Containing Composition] The solvent used in the present invention is a component that disperses the silver nanowires in the silver nanowire-containing composition and evaporates during film formation of the silver nanowire-containing layer to form a uniform coating film, and can be selected as appropriate. However, from the viewpoint of dispersibility of silver nanowires and compatibility with the polymerizable component, the solvent preferably contains a monohydric saturated alcohol having 1 to 6 carbon atoms or an alkylene glycol monoalkyl ether having 3 to 6 carbon atoms. Specific examples of monohydric saturated alcohols having 1 to 6 carbon atoms include methanol, ethanol, 1-propanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-1-propanol, and 1-hexanol. Specific examples of alkylene glycol monoalkyl ethers having 3 to 6 carbon atoms include ethylene glycol monomethyl ether, propylene glycol monomethyl ether, ethylene glycol monobutyl ether, and diethylene glycol monoethyl ether. Various other solvents can be used in combination as needed to the extent that they do not impair the effects of the invention. Preferably, the ratio of the monohydric saturated alcohol having 1 to 6 carbon atoms or the alkylene glycol monoalkyl ether having 3 to 6 carbon atoms in the solvent is 50% or more, more preferably 70% or more, and even more preferably 80% or more. Specific examples of other solvents that can be used in combination include water, diacetone alcohol, ethylene glycol, propylene glycol, ethylene glycol dimethyl ether, ethylene glycol monomethyl ether acetate, ethyl acetate, methyl isobutyl ketone, and toluene. The ratio of the solvent in the silver nanowire-containing composition is preferably 70% to 99.9% by mass, more preferably 80% to 99.9% by mass, even more preferably 85% to 99.8% by mass, and particularly preferably 90% to 99.7% by mass. The mass ratio of the solvent to the silver nanowires in the silver nanowire-containing composition is preferably 15 to 2,000, more preferably 40 to 1,000.

[0032] [Total Proportion of Polymerizable Monomer and Macromonomer Having a Hydroxyl Group] In the present invention, the total proportion of polymerizable monomer and macromonomer having a hydroxyl group in the polymerizable components in the silver nanowire-containing composition, i.e., the total proportion of polymerizable monomer and macromonomer having a hydroxyl group in the polymerizable components constituting the cured product contained in the silver nanowire-containing layer, is required to be 30% by mass or more. Since the more hydroxyl groups contained in the polymerizable component, the more improved the dispersibility of silver nanowires, the total proportion of polymerizable monomer and macromonomer having a hydroxyl group in the polymerizable component is preferably 35% by mass or more, more preferably 40% by mass or more. Similarly, from the viewpoint of dispersibility of silver nanowires, the hydroxyl value of the polymerizable component is preferably 10 mgKOH / g or more, more preferably 20 mgKOH / g or more, and even more preferably 30 mgKOH / g or more.

[0033] [Proportion of Silver Nanowires in the Components Excluding Solvent Contained in the Silver Nanowire-Containing Composition] In the present invention, the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition is preferably 15 to 60 mass%. By ensuring that the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition is 15 mass% or more, the far-infrared reflectance of the resulting silver nanowire-containing laminate can be increased. Furthermore, by ensuring that the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition is 60 mass% or less, the sheet resistance of the silver nanowire-containing layer can be maintained high, thereby improving radio wave transmittance. The proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition is more preferably 20 mass% or more, even more preferably 24 mass% or more, and particularly preferably 28 mass% or more. Furthermore, the proportion of silver nanowires in the silver nanowire-containing layer is more preferably 50 mass% or less, even more preferably 45 mass% or less, and particularly preferably 40 mass% or less. The proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition can be calculated by (mass of silver nanowires in the silver nanowire composition) / (mass of the components excluding the solvent contained in the silver nanowire-containing composition).

[0034] [Mass Ratio of Silver Nanowires to Polymerizable Component] In the present invention, the mass ratio of silver nanowires to the polymerizable component contained in the silver nanowire-containing composition, i.e., the mass ratio of silver nanowires to the polymerizable component constituting the cured product contained in the silver nanowire-containing layer, must be 0.20 to 1.5. A higher mass ratio of silver nanowires to polymerizable component can reduce the near-infrared transmittance while maintaining the visible light transmittance of the resulting silver nanowire-containing laminate; therefore, a mass ratio of 0.25 or more is preferred, 0.30 or more is more preferred, and 0.40 or more is even more preferred. A lower mass ratio of silver nanowires to polymerizable component can increase the sheet resistance of the silver nanowire-containing layer and improve the physical durability of the silver nanowire-containing layer; therefore, a mass ratio of 1.0 or less is preferred, 0.7 or less is more preferred. The mass ratio of silver nanowires to polymerizable component can be calculated by (mass of silver nanowires in the silver nanowire composition) / (mass of polymerizable component).

[0035] [Silver nanowire anti-degradation agent] A silver nanowire anti-degradation agent is a compound that functions to suppress the deterioration of silver nanowires in the environment. From the viewpoint of stability over time, it is preferable that the silver nanowire-containing composition contains a silver nanowire anti-degradation agent. The silver nanowire anti-degradation agent is not particularly limited and can be selected appropriately, and examples thereof include thiols and azoles.

[0036] [Step of curing the polymerizable component] The present invention includes a step of curing the polymerizable component with active energy rays after applying the silver nanowire-containing composition. The step of curing the polymerizable component is carried out by irradiating the polymerizable component with active energy rays such as ultraviolet light, visible light, or electron beams, and any known method can be used. Among these, photocuring using ultraviolet light is preferred from the viewpoint of ease of curing treatment. When photocuring using ultraviolet light, it is preferable to include a photopolymerization initiator in the silver nanowire-containing composition, and the light source for irradiating ultraviolet light can be selected as desired depending on the type of photopolymerization initiator, and examples thereof include a high-pressure mercury lamp, a xenon lamp, a metal halide lamp, and an LED.

[0037] [Photopolymerization initiator] The photopolymerization initiator is not particularly limited, and can be obtained by a known method, or a commercially available photopolymerization initiator can be used. Specific examples of photopolymerization initiators include 1-hydroxycyclohexyl phenyl ketone, diethoxyacetophenone, 2-hydroxy-2-methyl-1-phenylpropanone, 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoylbenzoic acid, methyl benzoylbenzoate, 2-methyl-1-[4-(methylthio)phenyl]-2-(4-morpholinyl)-1-propanone, xanthone, anthraquinone, and 2-methylanthraquinone. These can be used alone or in combination of two or more.

[0038] [Photopolymerization initiator content] The content of the photopolymerization initiator is not particularly limited, but is preferably 0.1 parts by mass to 10 parts by mass, and more preferably 2 parts by mass to 8 parts by mass, relative to 100 parts by mass of the total amount of the polymerizable components.

[0039] [Silver nanowire-containing laminate] The silver nanowire-containing laminate is a laminate having at least a substrate and a silver nanowire-containing layer. The silver nanowire-containing laminate may have other functional layers within a range that does not impair the effects of the present invention. Examples of other layers include a protective layer, an anti-reflection layer, an adhesive layer, and a hard coat layer.

[0040] [Protective Layer] The silver nanowire-containing laminate may further have a protective layer on the side of the silver nanowire-containing layer opposite the substrate. The protective layer is provided mainly for the purpose of physically and chemically protecting the silver nanowire-containing layer. The protective layer may be disposed adjacent to the silver nanowire-containing layer, or multiple layers may be provided between the protective layer and the silver nanowire-containing layer. The protective layer may also contain the silver nanowire deterioration inhibitor described above. From the viewpoint of protecting the silver nanowire-containing layer, it is preferable that the protective layer be disposed adjacent to the silver nanowire-containing layer. There are no particular restrictions on the materials that can be used as the protective layer and they can be appropriately selected depending on the purpose. Specific examples include epoxy resins, acrylic resins, urethane resins, silicone resins, etc.

[0041] The silver nanowire-containing laminate of the present invention can be used in windows of buildings, automobiles, etc., and can be applied to heat-blocking windows that reduce the load on air conditioning.

[0042] The present invention will be specifically explained below based on examples, but the present invention is not limited to these examples.

[0043] Synthesis Example 1: While introducing nitrogen into a four-neck flask equipped with a stirrer, a thermometer, and a nitrogen inlet tube, 666.97 parts by mass of a 1.0% by mass polyvinylpyrrolidone (BASF, Sokalan® K90P) propylene glycol solution, 5.35 parts by mass of a 1.5% by mass sodium chloride propylene glycol solution, 1.87 parts by mass of a 2.2% by mass sodium bromide propylene glycol solution, and 162.95 parts by mass of propylene glycol were added and stirred at room temperature for 30 minutes. The internal temperature was then raised to 145°C, and a solution prepared by mixing and dissolving 1.06 parts by mass of 2,5-dimethyl-4-hydroxy-3(2H)-furanone, 4.80 parts by mass of ion-exchanged water, and 30 parts by mass of propylene glycol was added and stirred for 10 minutes. Thereafter, 127 parts by mass of a propylene glycol solution of silver nitrate with a concentration of 5.5% by mass was added over 90 minutes while maintaining the internal temperature at 145°C, and the mixture was stirred for an additional 30 minutes. The resulting solution was then cooled to obtain a reaction solution (a-1) containing silver nanowires.

[0044] [Preparation of Aqueous Silver Nanowire Dispersion] 1,000 parts by mass of the reaction solution (a-1) containing silver nanowires was diluted with 3,000 parts by mass of water and then subjected to suction filtration using a membrane filter. Water was then added to the residue, and suction filtration was repeated five times. Water was then added again to obtain a 0.15% by mass crudely purified silver nanowire dispersion. The obtained crudely purified silver nanowire dispersion was centrifuged at 2,000 rpm for 10 minutes, and the remaining supernatant was collected to remove silver nanowires with relatively large diameters. The obtained supernatant was concentrated using a membrane filter to prepare an aqueous silver nanowire dispersion (b-1) with a silver nanowire content of 0.7% by mass. The obtained silver nanowires had an average major axis length of 12 μm and an average minor axis length of 25 nm.

[0045] (Synthesis Example 2) While nitrogen was being introduced into a four-necked flask equipped with a stirrer, a thermometer, and a nitrogen inlet tube, 342.75 parts by mass of a propylene glycol solution of 4.0% polyvinylpyrrolidone (manufactured by BASF, Sokalan (registered trademark) K90P), 5.34 parts by mass of a propylene glycol solution of 1.5% by mass of sodium chloride, 2.14 parts by mass of a propylene glycol solution of 2.2% by mass of sodium bromide, and 486.80 parts by mass of propylene glycol were added and stirred at room temperature for 30 minutes. Next, the internal temperature was raised to 145 ° C., and then a solution obtained by mixing and dissolving 1.17 parts by mass of 2,5-dimethyl-4-methoxy-3(2H)-furanone, 4.80 parts by mass of ion-exchanged water, and 30 parts by mass of propylene glycol was added and stirred for 10 minutes. Thereafter, while maintaining the internal temperature at 145°C, 127 parts by mass of a 5.5% by mass propylene glycol solution of silver nitrate was added over 15 minutes, and the mixture was stirred for an additional 30 minutes. The resulting solution was then cooled to obtain a reaction solution (a-2) containing silver nanowires. The resulting reaction solution (a-2) was treated in the same manner as reaction solution (a-1) in Synthesis Example 1 to prepare an aqueous dispersion of silver nanowires (b-2) with a silver nanowire content of 0.7% by mass. The resulting silver nanowires had an average major axis length of 4 μm and an average minor axis length of 30 nm.

[0046] [Preparation of Silver Nanowire Solvent Dispersion] 100 parts by mass of the silver nanowire aqueous dispersion (b-1) was diluted with 500 parts by mass of 1-propanol and the diluted solution was subjected to suction filtration using a membrane filter. 1-propanol was further added to the residue, and the suction filtration was repeated twice. 1-propanol was then added again to obtain a 1-propanol dispersion (c-1) of 0.7% by mass of silver nanowires.

[0047] 100 parts by mass of the aqueous dispersion of silver nanowires (b-2) was diluted with 500 parts by mass of ethanol and then subjected to suction filtration using a membrane filter. Ethanol was further added to the residue, and the suction filtration was repeated twice, and ethanol was added again to obtain an ethanol dispersion of 1.5% by mass of silver nanowires (c-2).

[0048] [Evaluation of Dispersibility of Silver Nanowires in Polymerizable Monomer] 0.1 parts by mass of the 1-propanol dispersion of silver nanowires (c-1) was added to 7 parts by mass of the polymerizable monomer and stirred, and the dispersion state of the silver nanowires was confirmed. The results are shown in Table 1.

[0049]

[0050] As shown in Table 1, in Evaluation Examples 3, 5, 7, and 8, which do not contain a polymerizable monomer or macromonomer having a hydroxyl group, the dispersibility of the silver nanowires in the polymerizable monomer or macromonomer is low, and the silver nanowires aggregate in the polymerizable monomer or macromonomer. Also, even when a hydroxyl group-containing monomer or macromonomer is contained, as in Evaluation Example 11, the silver nanowires aggregate when the proportion of the polymerizable monomer or macromonomer having a hydroxyl group is low, but it is clear that the silver nanowires can maintain a dispersed state in examples where the proportion of the polymerizable monomer or macromonomer having a hydroxyl group is 30% or more.

[0051] [Preparation of Silver Nanowire-Containing Composition] A plastic container was charged with 71.43 parts by mass of 0.7% by mass silver nanowire dispersion (c-1), 1.0 part by mass of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (Aronix M-305, manufactured by Toagosei Co., Ltd.), 0.05 parts by mass of 2-hydroxy-2-methyl-1-phenylpropanone, and 27.52 parts by mass of 1-propanol, and the container was then closed and mixed for 5 minutes on a shaker to prepare silver nanowire-containing composition (d-1) with a silver nanowire concentration of 0.5% by mass. Silver nanowire-containing compositions (d-2) to (d-18) were also prepared in the same manner as silver nanowire-containing composition (d-1), except that the compositions were changed as shown in Table 2.

[0052]

[0053] Details of the components in Table 2 are as follows: Aronix M-305: a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd., pentaerythritol triacrylate ratio: 55 to 63%) Aronix M-5700: 2-hydroxy-3-phenoxypropyl acrylate (manufactured by Toagosei Co., Ltd.) NK Oligo U-15HA: urethane acrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) NK Ester A-HD-N: 1,6-hexanediol diacrylate (manufactured by Shin-Nakamura Chemical Co., Ltd.) Initiator 1: 2-hydroxy-2-methyl-1-phenylpropanone Initiator 2: 1-hydroxycyclohexyl phenyl ketone NPA: 1-propanol PGM: propylene glycol monomethyl ether HPMC: hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., Metrose (registered trademark) 60SH50) PVA: Polyvinyl alcohol (Kuraray Co., Ltd., Kuraray Poval 28-98) Baylar Nb-G6600: Niobium oxide nanoparticle aqueous dispersion (Taki Chemical Co., Ltd., niobium oxide concentration 6% by mass, non-volatile content 9% by mass)

[0054] Example 1 Preparation of Silver Nanowire-Containing Laminate The silver nanowire-containing composition (d-1) was uniformly applied onto a 100 μm-thick polyethylene terephthalate film (PET film, manufactured by Toray Industries, Inc., product name "Lumirror U403") using a No. 12 wire bar, dried for 2 minutes in a hot air convection dryer at 70°C, and then applied onto the PET substrate from above at 1000 mJ / cm using an ultraviolet irradiation device UV1501C-SZ (manufactured by Sen Engineering Co., Ltd.). ２ A silver nanowire-containing laminate (e-1) was prepared by irradiating the substrate with UV light in a nitrogen atmosphere under the conditions of (a) to (c).

[0055] (Examples 2 to 19, Comparative Examples 1 to 6) In Examples 2 to 19 and Comparative Examples 1 to 6, silver nanowire-containing laminates were prepared in the same manner as in Example 1, except that the silver nanowire-containing compositions, wire bars, and drying conditions used were changed as shown in Tables 3 and 4.

[0056] [Dispersibility of Silver Nanowire-Containing Composition During Drying] With regard to silver nanowire-containing compositions (d-1) and (d-19), a drop of the silver nanowire-containing composition was placed on a glass slide (soda glass slide, manufactured by AS ONE Corporation) and observed using a dark-field microscope (trade name: BX51, manufactured by Olympus Corporation) to confirm the dispersion state of the silver nanowires as the solvent gradually evaporated. In silver nanowire-containing composition (d-1), no aggregation of silver nanowires due to solvent evaporation was observed. However, in silver nanowire-containing composition (d-19), aggregation of silver nanowires was observed as the solvent evaporated and the concentration of the polymerizable component increased. This shows that silver nanowire-containing composition (d-19), which does not contain a polymerizable monomer or macromonomer having a hydroxyl group, exhibits poor dispersibility of silver nanowires during drying.

[0057] [Measurement of Sheet Resistance of Silver Nanowire-Containing Layer] The sheet resistance (Ω / □) was measured at five different locations on the silver nanowire-containing layer coated surface of the prepared silver nanowire-containing laminate, and the sheet resistance of the silver nanowire-containing layer was calculated from the arithmetic mean value. A low resistivity meter Loresta-GP MCP-T610 (manufactured by Mitsubishi Chemical Corporation) was used to measure the sheet resistance. The results are shown in Tables 3 and 4.

[0058] [Measurement of visible light transmittance of silver nanowire-containing laminate] Using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance of three different parts of the prepared silver nanowire-containing laminate was measured, and the visible light transmittance of the silver nanowire-containing laminate was calculated from the arithmetic mean value. The results are shown in Tables 3 and 4.

[0059] [Near-infrared transmittance of silver nanowire-containing laminate] Using an ultraviolet-visible-near-infrared spectrophotometer V-670 (manufactured by JASCO Corporation, using an integrating sphere unit ISN-723), the prepared silver nanowire-containing laminate was placed with the silver nanowire-containing layer-coated surface facing the light source, and the transmittance in the wavelength range of 1500 to 2100 nm was measured at 0.5 nm intervals, and the near-infrared transmittance of the silver nanowire-containing laminate was calculated from the arithmetic mean value of the transmittance at each wavelength. The results are shown in Tables 3 and 4.

[0060] [Far-infrared reflectance of silver nanowire-containing laminate] Using a Fourier transform infrared spectrometer Spectrum Two (manufactured by PerkinElmer, using a specular reflection accessory with an incident angle of 16 degrees), the silver nanowire-containing layer coated surface of the prepared silver nanowire-containing laminate was placed on the light source side, and an Al mirror was used as the background. －１ ) reflectance in the range of 2 cm －１ The far-infrared reflectance of the silver nanowire-containing laminate was calculated from the arithmetic mean value of the reflectance at each wavelength. The results are shown in Tables 3 and 4.

[0061]

[0062]

[0063] An adhesive tape (product name "Scotch Mending Tape 810" manufactured by 3M Japan Ltd.) was applied to the side opposite the PET film of the silver nanowire-containing laminates prepared in the Examples and Comparative Examples 1 and 2 listed in Table 3, and the tape was rubbed with a finger three times. The adhesive tape was then peeled off, and the surface of the silver nanowire-containing laminate was visually observed to check for peeling of the silver nanowires. No clear peeling was observed in the silver nanowire-containing laminates prepared in the Examples listed in Table 3, but the silver nanowires had peeled off from the PET film in the silver nanowire-containing laminates prepared in Comparative Examples 1 and 2. This shows that the silver nanowire-containing laminates of the Examples listed in Table 3 have excellent adhesion to the substrate.

[0064] The silver nanowire-containing laminates obtained in the examples listed in Table 3 have sheet resistances within the range specified by the present invention, and therefore have superior radio wave transmittance compared to the silver nanowire-containing laminates obtained in Comparative Examples 1 to 4.

[0065] The silver nanowire-containing laminate obtained in the examples listed in Table 3 has a mass ratio of silver nanowires to polymerizable components that is within the range specified by the present invention. Therefore, compared to the silver nanowire-containing laminate obtained in Comparative Example 5, in which the mass ratio of silver nanowires to polymerizable components is smaller than the range specified by the present invention, the ratio of visible light transmittance to near-infrared transmittance is smaller, and it can be seen that near-infrared rays can be effectively blocked while maintaining transparency.

[0066] The silver nanowire-containing laminates obtained in the examples listed in Table 4 have a proportion of silver nanowires contained in the silver nanowire-containing layer that is within the range specified by the present invention, and therefore have higher far-infrared reflectivity and better thermal insulation properties than the silver nanowire-containing laminate obtained in Comparative Example 6, in which the proportion of silver nanowires contained in the silver nanowire-containing layer is smaller than the range specified by the present invention.

[0067] Compared to Example 12, Examples 1, 3, 5, 6, 8, and 10 have a more preferable range of mass ratio of silver nanowires to polymerizable components, and therefore it is possible to reduce the ratio of visible light transmittance to near-infrared light transmittance of the resulting silver nanowire-containing laminate.

Claims

1. A substrate having a silver nanowire-containing layer containing silver nanowires having an average minor axis length of 10 to 50 nm and an average major axis length of 2 to 20 μm and a cured product of a polymerizable component, wherein the sheet resistance of the silver nanowire-containing layer is 1.0×10 ３ A silver nanowire-containing laminate having a transmittance of Ω / □ or more, wherein the total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component is 30 mass% or more, the proportion of silver nanowires contained in the silver nanowire-containing layer is 15 to 60 mass%, the mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.5, and the ratio of visible light transmittance to near-infrared transmittance is 0.85 or less.

2. The silver nanowire-containing laminate according to claim 1, which has a far-infrared reflectance of 50% or more.

3. The silver nanowire-containing laminate according to claim 1, wherein the mass ratio of the silver nanowires to the polymerizable component is 0.25 to 1.

0.

4. Substrate and sheet resistance is 1.0 x 10 ３ A method for producing a silver nanowire-containing laminate having a silver nanowire-containing layer with a transmittance of Ω / □ or more, the method comprising the steps of: applying a silver nanowire-containing composition containing silver nanowires having an average minor axis length of 10 to 50 nm and an average major axis length of 2 to 20 μm, a polymerizable component, and a solvent to form a silver nanowire-containing layer; and curing the polymerizable component in the silver nanowire-containing layer with active energy rays, wherein the polymerizable component contained in the silver nanowire-containing composition contains a polymerizable monomer and a macromonomer having a hydroxyl group at a total ratio of 30 mass% or more, the mass ratio of the silver nanowires to the polymerizable component is 0.20 to 1.5, and the ratio of visible light transmittance to near-infrared transmittance of the obtained silver nanowire-containing laminate is 0.85 or less.

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