Silver nanowire-containing laminate and method for manufacturing the same

Abstract

The present invention aims to provide a silver nanowire-containing laminate and a method for producing the same, which have high sheet resistance in the silver nanowire-containing layer, better dispersibility of silver nanowires than conventional methods, and can reduce near-infrared transmittance while maintaining visible light transmittance. [Solution] A silver nanowire-containing laminate comprising silver nanowires and a cured product of a polymerizable component in which 30% by mass or more is a polymerizable monomer and / or macromonomer having hydroxyl groups, wherein the mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.5, and which has a silver nanowire-containing layer, and the ratio of visible light transmittance to near-infrared transmittance is 0.85 or less.

Description

Technical Field

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

Background Art

[0002] In recent years, as part of efforts to reduce greenhouse gas emissions, products that contribute to energy conservation have been strongly demanded. Among them, since it contributes to reducing the air-conditioning load of buildings, automobiles, etc., there is a demand for imparting heat insulation and heat shielding functions to windows.

[0003] As a method for imparting a heat insulation and heat shielding function to a window, forming a film having an infrared ray blocking effect, which is a heat ray, on a window glass or attaching an infrared ray blocking film to a window glass can be mentioned. As one of such things, for example, in Patent Document 1, a heat insulating film called a Low-E film using a noble metal film, which utilizes the low emissivity of infrared rays derived from the high reflectivity of far infrared rays, is known. However, since such a far infrared ray reflecting film is produced by a dry coating method such as sputtering, there are problems in terms of production speed and manufacturing cost.

[0004] On the other hand, silver nanowires are cited as one of the materials that can impart heat insulation properties by a wet coating method. For example, in Patent Document 2, since a heat ray reflecting layer can be formed by coating a silver nanowire dispersion using polyvinyl alcohol as a binder, while showing a high visible light transmittance, heat rays such as heating radiated from indoors are reflected and not released, and heat from the outside air is not taken into the room. It has been reported that a heat ray shielding film excellent in heat insulation can be manufactured, but the binder has problems from the viewpoint of substrate adhesion. Further, in Patent Document 3, a heat ray blocking material using silver nanowires excellent in durability by using a polymerizable monomer as a binder is reported.

[0005] Thus, although silver nanowires have heat insulation properties due to their high far-infrared reflectivity, they have limitations in blocking near-infrared light. Increasing the amount of silver nanowires used to reduce near-infrared light transmittance not only reduces visible light transmittance but also increases the conductivity of the silver nanowire-containing layer, leading to a deterioration in radio wave transmittance.

[0006] In particular, near-infrared radiation in the range of 1500nm to 2100nm is known to have a significant impact on the feeling of heat irritation caused by sunlight. Therefore, there was a need for a heat-shielding film made of silver nanowires that maintains visible light transmittance while providing high shielding performance against near-infrared radiation in the 1500nm to 2100nm range, compared to conventional heat-shielding films made of silver nanowires.

[0007] Furthermore, regarding the heat-shielding material disclosed in Patent Document 3, which uses a polymerizable monomer as a binder for a conductive particle-containing layer, it was observed that when a polymerizable monomer as described in the examples of Patent Document 3 was used, the dispersibility of silver nanowires with respect to the polymerizable monomer was low, and the silver nanowires began to aggregate when the monomer concentration increased. Such phenomena raised concerns about defects and skinning during the film formation and drying of the conductive particle-containing layer, and therefore required improvement. [Prior art documents] [Patent Documents]

[0008] [Patent Document 1] Japanese Patent Application Publication No. 63-134232 [Patent Document 2] Japanese Patent Publication No. 2012-252172 [Patent Document 3] Japanese Patent Publication No. 2017-32775 [Overview of the Initiative] [Problems that the invention aims to solve]

[0009] In view of the problems of the prior art described above, the present invention aims to provide a silver nanowire-containing laminate and a method for manufacturing the same, which have good adhesion of the silver nanowire-containing layer to the substrate, high sheet resistance of the silver nanowire-containing layer, eliminate concerns about the dispersion of silver nanowires compared to conventional methods, and can reduce near-infrared transmittance while maintaining visible light transmittance. [Means for solving the problem]

[0010] The inventors of the present invention conducted intensive research to solve the aforementioned problems and, as a result, discovered that the aforementioned 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 the silver nanowire to a specific ratio, thereby completing the present invention.

[0011] In other words, the present invention is <1> base material and It has a silver nanowire-containing layer that includes silver nanowires with an average short axis length of 10-50 nm and an average long axis length of 2-20 μm, and a cured polymerizable component. The sheet resistance of the silver nanowire-containing layer is 1.0 × 10 3 A silver nanowire-containing laminate with a ratio of Ω / □ or higher, The total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component is 30% by mass or more. The proportion of silver nanowires in the silver nanowire-containing layer is 15 to 60% by mass. The mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.5. A silver nanowire-containing laminate having a ratio of visible light transmittance to near-infrared transmittance of 0.85 or less. <2> The above-mentioned far-infrared reflectance is 50% or more. <1> The silver nanowire-containing laminate described above, <3> The mass ratio of silver nanowires to the polymerizable component is 0.25 to 1.0. <1> The silver nanowire-containing laminate described above, <4> The substrate and sheet resistance are 1.0 × 10 3A method for producing a silver nanowire-containing laminate having a silver nanowire-containing layer with a ratio of Ω / □ or higher, A process of forming a silver nanowire-containing layer by coating a silver nanowire-containing composition containing silver nanowires having an average short axis length of 10-50 nm and an average long axis length of 2-20 μm, a polymerizable component, and a solvent, A method for producing a silver nanowire-containing laminate, comprising the step of curing the polymerizable component in the silver nanowire-containing layer with active energy rays, The total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable components contained in the silver nanowire-containing composition is 30% by mass or more. A method for producing a silver nanowire-containing laminate, wherein the mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.5, and the ratio of the visible light transmittance to the near-infrared transmittance of the obtained silver nanowire-containing laminate is 0.85 or less. That is the case. [Effects of the Invention]

[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 of conventional methods. This makes it possible to obtain a silver nanowire-containing heat shielding material that reduces near-infrared transmittance while maintaining a certain level of sheet resistance to ensure visible light transmittance and radio wave transmittance. [Modes for carrying out the invention]

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

[0014] [Base material] The base material in the present invention is not particularly limited as long as it can be obtained by a known method or is a commercially available base material and can be used. Specific examples of the material of the base material 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 base material. Also, a plurality of base materials may be laminated. As the base material, an optically transparent one is preferable, and one having a visible light transmittance of 70% or more is preferable, and one having a visible light transmittance of 80% or more is more preferable.

[0015] [Silver nanowire] The "silver nanowire" in the present invention refers to a silver structure having a minor axis length of less than 1 μm and an aspect ratio (major axis length / minor axis length) of 10 or more. Note that there is no particular limitation on the method for producing the silver nanowire used in the present invention, and those obtained by a known production method can be used. Among them, it is preferable to use a production method in which a silver nanowire is obtained by reducing a silver salt in the presence of a growth controller and a halide salt in a polyol.

[0016] When the silver nanowire is used as a transparent heat ray blocking film, in order to enhance transparency, it is advantageous and preferable that the average minor axis length of the wire is small. The "minor axis length of the silver nanowire" in the present invention refers to the minor axis length measured using a scanning electron microscope (SEM; manufactured by JEOL Ltd., JSM-5610LV). Also, the "average minor axis length of the silver nanowire" refers to the average value of the minor axis lengths measured by observing 100 or more silver nanowires. In the present invention, it is required that the average minor axis length of the silver nanowire is 5 nanometers or less, preferably 4 nanometers or less, more preferably 3 nanometers or less, and even more preferably 2.5 nanometers or less. On the other hand, since the durability under high temperature and high humidity conditions is higher when the average minor axis length of the silver nanowire is larger, the average minor axis length of the silver nanowire is preferably 10 nanometers or more, and more preferably 15 nanometers or more.

[0017] The infrared blocking performance of silver nanowires is known to function due to the anisotropy of the silver nanowires in the longitudinal direction, that is, because the longitudinal length exceeds the nanometer size. Therefore, from the viewpoint of infrared blocking, the average longitudinal length of the nanowires needs to be above a certain length. On the other hand, nanowires that are too long are prone to entanglement, reducing dispersion stability, and the increased contact opportunities between silver nanowires tend to lower the sheet resistance, so shorter nanowires are preferable. In this invention, "long-axis length of silver nanowire" refers to the value calculated using image processing software (product name: Image-Pro Premier, Media Cybernetics, Inc.) after photographing silver nanowires using a dark-field microscope (product name: BX51, manufactured by Olympus Corporation). Furthermore, "average longitudinal length of silver nanowire" refers to the average value of the longitudinal lengths measured by observing 1000 or more silver nanowires. In this invention, the average longitudinal length of 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 components] The polymerizable component in this invention is a compound that can be cured by undergoing a polymerization reaction directly or in response to an initiator when irradiated with active energy rays such as ultraviolet light, visible light, or electron beams. This invention is characterized by containing polymerizable monomers and / or macromonomers having hydroxyl groups as the polymerizable component. By curing the polymerizable component, the sheet resistance of the silver nanowire-containing layer can be increased by adhering the silver nanowires to the substrate and inhibiting contact between the silver nanowires.

[0019] The dispersibility of silver nanowires can be improved by including polymerizable monomers and / or macromonomers having hydroxyl groups in the polymerizable component. The polymerizable monomers and macromonomers having hydroxyl groups are monomers and macromonomers that undergo polymerization reactions directly or in response to the action of an initiator by irradiation with visible light or active energy rays such as ultraviolet light or electron beams. They can be used without particular limitations as long as they have at least one hydroxyl group in the molecule. However, since a higher number of hydroxyl groups per molecular weight results in better dispersibility of silver nanowires, it is preferable that the number of hydroxyl groups per molecular weight be 1 / 3000 or more, more preferably 1 / 2000 or more, and even more preferably 1 / 1000 or more. Specific examples of polymerizable monomers having hydroxyl groups 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 hydroxyl groups include polymerizable epoxy resins and polymerizable acrylic resins having an average of one or more polymerizable unsaturated groups and an average of one or more hydroxyl groups per molecule. Among these, polymerizable monomers and / or macromonomers having hydroxyl groups with (meth)acryloyl groups are preferred from the viewpoint of radical polymerization.

[0020] As polymerizable components, in addition to the polymerizable monomers and / or macromonomers having hydroxyl groups, polymerizable monomers and / or macromonomers without hydroxyl groups can be used in combination. The polymerizable monomers and / or macromonomers without hydroxyl groups are not particularly limited and can be used as any monomer or macromonomer that undergoes a polymerization reaction directly or in response to an initiator by irradiation with visible light or active energy rays such as ultraviolet light or electron beams. Specific examples of polymerizable monomers include (meth)acrylic acid esters such as (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, and methoxy-triethylene glycol (meth)acrylate; aromatic vinyls such as styrene and methylstyrene; vinyl carboxylate esters such as vinyl acetate; (meth)acrylamide, N-isopropyl (meth)acrylate Examples include (meth)acrylamides such as luamide 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 macromonomers include polymerizable urethane acrylate resins, polymerizable acrylic resins, and polymerizable polyester resins, each having an average of one or more polymerizable unsaturated groups per molecule. These can be used individually 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 polymerizable component. The silver nanowire-containing layer is obtained by coating and drying a silver nanowire-containing composition, described later, onto a substrate 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 1.0 × 10⁻⁶, from the viewpoint of radio wave transmission. 3 A resistance of Ω / □ or higher is required. Radio wave transparency is better the higher the sheet resistance of the silver nanowire-containing layer, therefore 1.0 × 10 4 It is more preferable that the resistance is Ω / □ or greater. The upper limit of the sheet resistance of the silver nanowire-containing layer is not particularly limited, but is generally 1.0 × 10⁻⁶. 20 It is less than or equal to Ω / □.

[0023] [Percentage of silver nanowires in the silver nanowire-containing layer] In this invention, the proportion of silver nanowires in the silver nanowire-containing layer must be 15 to 60% by mass. By setting the proportion of silver nanowires in the silver nanowire-containing layer to 15% by mass or more, the far-infrared reflectivity due to the silver nanowires can be increased. Furthermore, by setting the proportion of silver nanowires in the silver nanowire-containing layer to 60% by mass or less, the sheet resistance of the silver nanowire-containing layer can be kept high, thereby increasing the 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] A higher visible light transmittance of the silver nanowire-containing laminate is preferable because it improves transparency. In this invention, the visible light transmittance is the total light transmittance measured by the method in accordance with JIS K 7361-1. The visible light transmittance of the silver nanowire-containing laminate is preferably 60% or higher, more preferably 70% or higher, and even more preferably 75% or higher.

[0025] [Near-infrared transmittance of silver nanowire-containing laminate] In this invention, near-infrared transmittance refers to the average transmittance of infrared rays in the 1500-2100 nm range. From the viewpoint of suppressing the scorching sensation caused by sunlight, it is preferable that the near-infrared transmittance of the silver nanowire-containing laminate be low. 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 the visible light transmittance to the near-infrared transmittance of a silver nanowire-containing laminate can be used as an indicator of the compatibility between the transparency and near-infrared shielding properties of the silver nanowire-containing laminate. A lower value indicates that near-infrared rays are blocked while maintaining transparency. In this invention, the ratio of the visible light transmittance to the 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 the visible light transmittance to the near-infrared transmittance of the silver nanowire-containing laminate can be determined by (near-infrared transmittance of the silver nanowire-containing laminate) / (visible light transmittance of the silver nanowire-containing laminate).

[0027] [Far-infrared reflectivity of silver nanowire-containing laminate] A higher far-infrared reflectance of the silver nanowire-containing laminate is preferable because it improves heat insulation. In this invention, the far-infrared reflectance refers to the average value of the relative reflectance of infrared rays with respect to the Al mirror in the 2.5 to 25 μm range. The far-infrared reflectance of the silver nanowire-containing laminate is preferably 50% or higher, more preferably 60% or higher, and even more preferably 70% or higher.

[0028] [Process for forming a silver nanowire-containing layer] The present invention relates to a method for producing a silver nanowire-containing laminate, which includes the step of applying a silver nanowire-containing composition onto a substrate to form a silver nanowire-containing layer. Specific examples of application methods include spin coating, slit coating, dip coating, blade coating, bar coating, spray coating, letterpress printing, intaglio printing, screen printing, planar printing, dispensing, and inkjet printing. Furthermore, these application methods may be used to apply multiple layers of the laminate.

[0029] [Silver nanowire-containing composition] The silver nanowire-containing composition of the present invention comprises at least silver nanowires, a polymerizable component, and a solvent. Various additives may be used in combination with the silver nanowire-containing composition as needed, to the extent that they do not impair the effects of the invention. Specific examples of additives include non-photosensitive resins, dispersants, leveling agents, refractive index modifiers, and silver nanowire degradation inhibitors.

[0030] [Concentration of silver nanowires] The concentration of silver nanowires in the silver nanowire-containing composition used in the present invention can be set arbitrarily, 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, it becomes necessary to increase the coating thickness or apply multiple coats to obtain the desired infrared shielding performance during coating, thus increasing the effort required during use. Therefore, from the viewpoint of productivity, it 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 used to disperse the silver nanowires in the silver nanowire-containing composition and to form a uniform coating film by evaporation when forming the silver nanowire-containing layer. While it can be selected as appropriate, it is preferable to include a monovalent saturated alcohol having 1 to 6 carbon atoms or an alkylene glycol monoalkyl ether having 3 to 6 carbon atoms, from the viewpoint of dispersibility of silver nanowires and compatibility with polymerizable components. Specific examples of monovalent 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. Other solvents can be used in combination as needed, as long as they do not hinder the effects of the invention. However, it is preferable that the proportion of a monohydric saturated alcohol having 1 to 6 carbon atoms or an 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 proportion of 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. Furthermore, the mass ratio of the solvent to the silver nanowires in the silver nanowire-containing composition is preferably 15 to 2000, and more preferably 40 to 1000.

[0032] [Total percentage of polymerizable monomers and macromonomers containing hydroxyl groups] In the present invention, the total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component of the silver nanowire-containing composition, that is, the total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component constituting the cured product contained in the silver nanowire-containing layer, is required to be 30% by mass or more. Since the dispersibility of silver nanowires improves as the amount of hydroxyl groups in the polymerizable component increases, the total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component is preferably 35% by mass or more, and 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 mg KOH / g or more, more preferably 20 mg KOH / g or more, and even more preferably 30 mg KOH / g or more.

[0033] [Percentage of silver nanowires in the components of the silver nanowire-containing composition, excluding the solvent] In this invention, it is preferable that the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition be 15 to 60% by mass. By setting the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition to 15% by mass or more, the far-infrared reflectivity of the resulting silver nanowire-containing laminate can be increased. Furthermore, by setting the proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition to 60% by mass or less, the sheet resistance of the silver nanowire-containing layer can be maintained at a high level, thereby increasing the 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% by mass or more, even more preferably 24% by mass or more, and particularly preferably 28% by mass or more. Furthermore, the proportion of silver nanowires in the silver nanowire-containing layer is more preferably 50% by mass or less, even more preferably 45% by mass or less, and particularly preferably 40% by mass or less. The proportion of silver nanowires in the components excluding the solvent contained in the silver nanowire-containing composition can be determined by (mass of silver nanowires in the silver nanowire-containing composition) / (mass of components excluding the solvent contained in the silver nanowire-containing composition).

[0034] [Mass ratio of silver nanowires to polymerizable components] In this invention, the mass ratio of silver nanowires to polymerizable components in the silver nanowire-containing composition, that is, the mass ratio of silver nanowires to polymerizable components constituting the cured product in the silver nanowire-containing layer, needs to be between 0.20 and 1.5. A higher mass ratio of silver nanowires to polymerizable components allows for a reduction in near-infrared transmittance while maintaining the visible light transmittance of the resulting silver nanowire-containing laminate; therefore, a ratio of 0.25 or higher is preferable, 0.30 or higher is more preferable, and 0.40 or higher is even more preferable. Furthermore, a lower mass ratio of silver nanowires to polymerizable components allows for a higher sheet resistance of the silver nanowire-containing layer and improves the physical durability of the silver nanowire-containing layer; therefore, a ratio of 1.0 or lower is preferable, and 0.7 or lower is more preferable. The mass ratio of silver nanowires to polymerizable components can be determined by (mass of silver nanowires in the silver nanowire composition) / (mass of polymerizable components).

[0035] [Silver nanowire degradation inhibitor] Silver nanowire degradation inhibitors are compounds that function to suppress the degradation of silver nanowires under environmental conditions. From the viewpoint of long-term stability, it is preferable that silver nanowire-containing compositions include silver nanowire degradation inhibitors. Silver nanowire degradation inhibitors are not particularly limited and can be appropriately selected, for example, thiols and azoles.

[0036] [Process for curing polymerizable components] The present invention includes a step of curing a polymerizable component with active energy rays after applying a 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 known methods can be used. Among these, photocuring using ultraviolet light is preferred from the viewpoint of simplicity of the curing process. 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 with ultraviolet light can be arbitrarily selected depending on the type of photopolymerization initiator, and examples include high-pressure mercury lamps, xenon lamps, metal halide lamps, LEDs, etc.

[0037] [Photopolymerization initiator] The photopolymerization initiator is not particularly limited, and any photopolymerization initiator obtained by known methods or a commercially available one can be used. Specific examples of photopolymerization initiators include 1-hydroxycyclohexylphenyl 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, xanthones, anthraquinones, 2-methylanthraquinone, etc. These can be used individually or in combination of two or more.

[0038] [Content of photopolymerization initiator] There are no particular restrictions on the content of the photopolymerization initiator, but it is preferably 0.1 to 10 parts by mass, and more preferably 2 to 8 parts by mass, when the total amount of polymerizable components is 100 parts by mass.

[0039] [Silver nanowire-containing laminate] A 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 as long as they do not impede the effects of the present invention. Examples of other layers include a protective layer, an anti-reflective layer, an adhesive layer, a hard coat layer, and the like.

[0040] [Protective layer] The silver nanowire-containing laminate may have an additional protective layer on the side of the silver nanowire-containing layer opposite the substrate. The protective layer is mainly provided for the purpose of physically and chemically protecting the silver nanowire-containing layer. The protective layer may be installed adjacent to the silver nanowire-containing layer, or there may be multiple layers between the protective layer and the silver nanowire-containing layer. The protective layer may also contain the aforementioned silver nanowire degradation inhibitor. From the viewpoint of protecting the silver nanowire-containing layer, it is preferable that the protective layer be placed 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 according to the purpose. Specific examples include epoxy resin, acrylic resin, urethane resin, silicone resin, etc.

[0041] The silver nanowire-containing laminate of the present invention can be used, for example, in windows of buildings or automobiles to create heat-shielding windows that reduce the air conditioning load. [Examples]

[0042] The present invention will be described in detail below based on embodiments, but the present invention is not limited to these embodiments.

[0043] <Fabrication of silver nanowires> (Synthesis Example 1) In a four-necked flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 666.97 parts by mass of a propylene glycol solution of 1.0% by mass polyvinylpyrrolidone (BASF, Sokalan® K90P), 5.35 parts by mass of a propylene glycol solution of 1.5% by mass sodium chloride, 1.87 parts by mass of a propylene glycol solution of 2.2% by mass sodium bromide, and 162.95 parts by mass propylene glycol were added while nitrogen was supplied. The mixture was stirred at room temperature for 30 minutes. Then, after raising the internal temperature to 145°C, 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 deionized water, and 30 parts by mass of propylene glycol was added, and the mixture was stirred for 10 minutes. Subsequently, while maintaining the internal temperature at 145°C, 127 parts by mass of a 5.5% by mass silver nitrate propylene glycol solution were added over 90 minutes, and the mixture was stirred for a further 30 minutes. The resulting solution was then cooled to obtain reaction solution (a-1) containing silver nanowires.

[0044] [Preparation of a silver nanowire aqueous dispersion] 1000 parts by mass of reaction solution (a-1) containing silver nanowires were diluted with 3000 parts by mass of water and filtered by suction using a membrane filter. Further water was added to the residue and suction filtration was repeated five times, and water was added again to obtain a 0.15% by mass crude purified silver nanowire dispersion. The obtained crude purified silver nanowire dispersion was treated with a centrifuge at a rotation speed of 2000 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 a 0.7% by mass silver nanowire aqueous dispersion (b-1). The obtained silver nanowires had an average long axis length of 12 μm and an average short axis length of 25 nm.

[0045] (Synthesis Example 2) In a four-necked flask equipped with a stirrer, thermometer, and nitrogen inlet tube, 342.75 parts by mass of a propylene glycol solution of 4.0% by mass polyvinylpyrrolidone (BASF, Sokalan® K90P), 5.34 parts by mass of a propylene glycol solution of 1.5% by mass sodium chloride, 2.14 parts by mass of a propylene glycol solution of 2.2% by mass sodium bromide, and 486.80 parts by mass propylene glycol were added while nitrogen was supplied. The mixture was stirred at room temperature for 30 minutes. Next, the internal temperature was raised to 145°C, and a solution prepared by mixing and dissolving 1.17 parts by mass of 2,5-dimethyl-4-methoxy-3(2H)-furanone, 4.80 parts by mass of deionized water, and 30 parts by mass propylene glycol was added, and the mixture was stirred for 10 minutes. Subsequently, while maintaining the internal temperature at 145°C, 127 parts by mass of a 5.5% by mass silver nitrate propylene glycol solution were added over 15 minutes, and the mixture was stirred for a further 30 minutes. The resulting solution was then cooled to obtain reaction solution (a-2) containing silver nanowires. The obtained 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) containing 0.7% by mass. The obtained 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 a silver nanowire aqueous dispersion (b-1) was diluted with 500 parts by mass of 1-propanol and filtered by suction using a membrane filter. Further 1-propanol was added to the residue and suction filtration was repeated twice, and 1-propanol was added again to obtain a 0.7% by mass silver nanowire 1-propanol dispersion (c-1).

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

[0048] [Evaluation of the dispersibility of silver nanowires with polymerizable monomers] 7 parts by mass of polymerizable monomer were mixed with 0.1 parts by mass of a 1-propanol dispersion of silver nanowires (c-1), and the mixture was stirred to confirm the dispersion state of the silver nanowires. The results are shown in Table 1.

[0049] [Table 1]

[0050] As shown in Table 1, in Evaluation Examples 3, 5, 7, and 8, which do not contain polymerizable monomers or macromonomers containing hydroxyl groups, the dispersibility of silver nanowires in the polymerizable monomers or macromonomers is low, and it can be seen that the silver nanowires aggregate in the polymerizable monomers or macromonomers. Furthermore, even when hydroxyl-containing monomers or macromonomers are included, as in Evaluation Example 11, the silver nanowires aggregate when the proportion of polymerizable monomers or macromonomers containing hydroxyl groups is low, but in examples where the polymerizable monomers or macromonomers containing hydroxyl groups are 30% or more, it can be seen that the silver nanowires can maintain their dispersed state.

[0051] [Preparation of silver nanowire-containing composition] A silver nanowire-containing composition (d-1) with a silver nanowire concentration of 0.5% by mass was prepared by placing 71.43 parts by mass of a 0.7% by mass silver nanowire dispersion (c-1), 1.0 part by mass of a mixture of pentaerythritol triacrylate and pentaerythritol tetraacrylate (manufactured by Toagosei Co., Ltd., Aronics M-305), 0.05 parts by mass of 2-hydroxy-2-methyl-1-phenylpropanone, and 27.52 parts by mass of 1-propanol into a poly container, closing the lid, and mixing with a shaker for 5 minutes. Silver nanowire-containing compositions (d-2) to (d-18) were prepared in the same manner as silver nanowire-containing composition (d-1), except that the composition was changed as shown in Table 2.

[0052] [Table 2]

[0053] The 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 content 55-63%) Aronix M-5700: 2-Hydroxy-3-Phenoxypropyl Acrylate (manufactured by Toagosei Co., Ltd.) NK Oligo U-15HA: Urethane acrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) NK Ester A-HD-N: 1,6-Hexanediol Diacrylate (manufactured by Shin-Nakamura Chemical Industry Co., Ltd.) Initiator 1: 2-hydroxy-2-methyl-1-phenylpropanone Initiator 2: 1-Hydroxycyclohexylphenyl ketone NPA: 1-propanol PGM: Propylene glycol monomethyl ether HPMC: Hydroxypropyl methylcellulose (manufactured by Shin-Etsu Chemical Co., Ltd., Metroze® 60SH50) PVA: Polyvinyl alcohol (manufactured by Kuraray Co., Ltd., Kuraray Poval 28-98) Bailar Nb-G6600: Niobium oxide nanoparticle aqueous dispersion (manufactured by Taki Chemical Co., Ltd., niobium oxide concentration 6% by mass, non-volatile content 9% by mass)

[0054] (Example 1) [Preparation of silver nanowire-containing laminates] A silver nanowire-containing composition (d-1) was uniformly applied to a 100 μm thick polyethylene terephthalate film (PET film, manufactured by Toray Industries, Inc., product name "Lumirror U403") using a No. 12 wire bar. After drying in a 70°C hot air convection dryer for 2 minutes, 1000 mJ / cm² of ultraviolet light was applied to the PET substrate from above using a UV1501C-SZ ultraviolet irradiation device (manufactured by Sen Engineering Co., Ltd.). 2 Under these conditions, a silver nanowire-containing laminate (e-1) was fabricated by irradiating it with UV light in a nitrogen atmosphere.

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

[0056] [Dispersibility of silver nanowire-containing compositions during drying] Regarding silver nanowire-containing compositions (d-1) and (d-19), a drop of the silver nanowire-containing composition was placed on a glass slide (soda-lime glass slide manufactured by AS ONE Corporation), and observed using a dark-field microscope (product 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 was observed as the solvent evaporated, but in silver nanowire-containing composition (d-19), aggregation of silver nanowires was observed as the solvent evaporated and the concentration of polymerizable components increased. Thus, it can be seen that silver nanowire-containing composition (d-19), which does not contain polymerizable monomers or macromonomers with hydroxyl groups, has poor dispersibility of silver nanowires when dry.

[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 coating side of the fabricated silver nanowire-containing laminate, and the sheet resistance of the silver nanowire-containing layer was determined from the arithmetic mean. 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 laminates] Using a haze meter NDH5000 (manufactured by Nippon Denshoku Industries Co., Ltd.), the total light transmittance of three different locations in the fabricated silver nanowire-containing laminate was measured, and the visible light transmittance of the silver nanowire-containing laminate was determined from the arithmetic mean. The results are shown in Tables 3 and 4.

[0059] [Near-infrared transmittance of silver nanowire-containing laminate] Using a V-670 UV-Vis-Near-Infrared Spectrophotometer (manufactured by JASCO Corporation, using the ISN-723 integrating sphere unit), the fabricated silver nanowire-containing laminate was positioned with the silver nanowire-containing layer coating side facing the light source. 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 determined from the arithmetic mean of the transmittances at each wavelength. The results are shown in Tables 3 and 4.

[0060] [Far-infrared reflectivity 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 fabricated silver nanowire-containing laminate was positioned with the silver nanowire-containing layer coated side facing the light source, and an Al mirror was used as the background, with wavelengths of 2.5 to 25 μm (wavenumbers 4000 to 400 cm). -1 The reflectance in the range of 2cm -1 Measurements were taken at intervals, and the far-infrared reflectance of the silver nanowire-containing laminate was determined from the arithmetic mean of the reflectances at each wavelength. The results are shown in Tables 3 and 4.

[0061] [Table 3]

[0062] [Table 4]

[0063] Adhesive tape (manufactured by 3M Japan Ltd., product name "Scotch Mending Tape 810") was applied to the side of the silver nanowire-containing laminate prepared in the examples and comparative examples 1 and 2 described in Table 3, opposite to the PET film. After rubbing it three times with a finger, the adhesive tape was peeled off, and the surface of the silver nanowire-containing laminate was visually observed to check for the presence or absence of delamination of the silver nanowires. No clear delamination was observed in the silver nanowire-containing laminate prepared in the examples described in Table 3, but the silver nanowires had peeled off from the PET film in the silver nanowire-containing laminate prepared in comparative examples 1 and 2. This indicates that the silver nanowire-containing laminates of the examples described in Table 3 have excellent adhesion to the substrate.

[0064] The silver nanowire-containing laminates obtained in the examples shown in Table 3 have sheet resistances within the range defined in this invention, and therefore exhibit superior radio wave transmission compared to the silver nanowire-containing laminates obtained in Comparative Examples 1 to 4.

[0065] The silver nanowire-containing laminates obtained in the examples described in Table 3 have a mass ratio of silver nanowires to polymerizable components within the range defined in this invention. Therefore, compared to the silver nanowire-containing laminate obtained in Comparative Example 5, where the mass ratio of silver nanowires to polymerizable components is smaller than the range defined in this invention, the ratio of visible light transmittance to near-infrared transmittance is smaller, indicating that near-infrared radiation can be effectively blocked while maintaining transparency.

[0066] The silver nanowire-containing laminates obtained in the examples described in Table 4 have a proportion of silver nanowires in the silver nanowire-containing layer that is within the range defined in this invention. Therefore, compared to the silver nanowire-containing laminate obtained in Comparative Example 6, where the proportion of silver nanowires in the silver nanowire-containing layer is smaller than the range defined in this invention, the silver nanowire-containing laminates obtained in this example have a higher far-infrared reflectivity and superior heat insulation.

[0067] Compared to Example 12, Examples 1, 3, 5, 6, 8, and 10 have a more favorable mass ratio of silver nanowires to polymerizable components, which allows for a lower ratio of visible light transmittance to near-infrared transmittance of the resulting silver nanowire-containing laminates.

Claims

1. base material and The material has a silver nanowire-containing layer that includes silver nanowires with an average short axis length of 10 to 50 nm and an average long axis length of 2 to 20 μm, and a cured polymerizable component. The sheet resistance of the silver nanowire-containing layer is 1.0 × 10 ３ A silver nanowire-containing laminate having an Ω / □ or greater ratio, The total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable component is 30% by mass or more. The proportion of silver nanowires in the silver nanowire-containing layer is 15 to 60% by mass. The mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.

5. A silver nanowire-containing laminate having a ratio of visible light transmittance to near-infrared transmittance of 0.85 or less.

2. A silver nanowire-containing laminate according to claim 1, wherein the far-infrared reflectance is 50% or more.

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

0.

4. The substrate and sheet resistance are 1.0 × 10 ３ A method for producing a silver nanowire-containing laminate having a silver nanowire-containing layer with a ratio of Ω / □ or higher, A process of forming a silver nanowire-containing layer by coating a silver nanowire-containing composition containing silver nanowires having an average short axis length of 10 to 50 nm and an average long axis length of 2 to 20 μm, a polymerizable component, and a solvent, A method for producing a silver nanowire-containing laminate, comprising the step of curing the polymerizable component in the silver nanowire-containing layer with active energy rays, The total proportion of polymerizable monomers and macromonomers having hydroxyl groups in the polymerizable components contained in the silver nanowire-containing composition is 30% by mass or more. A method for producing a silver nanowire-containing laminate, wherein the mass ratio of silver nanowires to the polymerizable component is 0.20 to 1.5, and the ratio of the visible light transmittance to the near-infrared transmittance of the obtained silver nanowire-containing laminate is 0.85 or less.

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