heat-shielding film

Abstract

[Problem] To provide a thermal barrier film which exhibits high transparency, excellent friction resistance, excellent film strength and excellent bendability, while having high thermal barrier properties. [Solution] A thermal barrier film which comprises a thermal barrier layer that is superposed on at least one surface of a base material film directly or with another layer being interposed therebetween, wherein: the thermal barrier layer is formed from a thermal barrier layer forming composition that contains an antimony-doped tin oxide and a binder resin; the average primary particle diameter of the antimony-doped tin oxide contained in the thermal barrier layer is less than 50 nm; the minimum diameter of the mandrel at which a crack occurs in the thermal barrier layer is less than 4 mm as determined by a cylindrical mandrel method; the spectral transmittance T1400 nm of the thermal barrier film at the wavelength of 1,400 nm is 20% or less; and the haze value of the thermal barrier film is 8% or less.

Description

[Technical Field]

[0001] The present invention relates to a heat-shielding film. [Background technology]

[0002] Agricultural greenhouses have traditionally played an important role in cultivating horticultural crops such as vegetables, fruit trees, and flowers. Against the backdrop of global population growth, climate change, and a decline in the number of people working in agriculture, there is a need for a stable supply of horticultural crops and improved productivity, and the functions required of agricultural greenhouses are becoming more sophisticated.

[0003] To improve the productivity of horticultural crops, temperature management of the cultivation environment is important from the perspective of growth. For example, in the summer, strong sunlight can increase the temperature inside a greenhouse, hindering crop growth and potentially causing leaf burn. The most common countermeasures to high temperatures are greenhouse ventilation, the use of heat-shielding netting, and mist cooling using the heat of evaporation of water. However, these methods pose challenges to improving crop productivity, as ventilation inside the greenhouse can cause insect damage, heat-shielding netting reduces the penetration of sunlight necessary for growth, and mist cooling can have the adverse effect of causing drifting. Furthermore, in winter, sudden drops in temperature in the morning and evening can lead to frost, and low temperatures inside the greenhouse due to insufficient sunlight can have a negative impact on crop growth.

[0004] To solve the above problems, it has been proposed to use a heat-shielding film. For example, Patent Document 1 proposes a method of attaching a heat-shielding film to the outer frame film of an agricultural greenhouse via an adhesive. Patent Document 2 proposes a method of using a heat-shielding film installed in the form of a curtain or roll inside the agricultural greenhouse. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] WO2015-025513 [Patent Document 2] Patent Publication No. 2016-149977 Summary of the Invention [Problem to be solved by the invention]

[0006] However, the heat-shielding films of the above-mentioned prior art documents had insufficient heat-shielding properties and transparency, posing challenges to stable crop supply and productivity improvement. Furthermore, the films had poor abrasion resistance and flexibility, resulting in durability problems. Furthermore, when using a heat-shielding film in the method described in Patent Document 2, the flexibility was insufficient, which could lead to problems such as poor handling and film cracking of the heat-shielding layer.

[0007] Furthermore, improving the heat-shielding properties of a film tends to increase the haze of the film, decrease the amount of light transmitted, or deteriorate visibility. For this reason, there is a demand for a heat-shielding film that not only has high heat-shielding properties but also high light transmittance and high visibility.

[0008] The present invention has been made to solve the above-mentioned problems. Specifically, the present invention provides a heat-shielding film that has excellent heat-shielding properties, transparency, abrasion resistance, and flexibility, and can contribute to the stable supply of horticultural crops and improved productivity. Furthermore, the present invention provides a heat-shielding film that, due to its excellent heat-shielding properties, can also be used as a building material, for example, for window linings in automobiles and houses. [Means for solving the problem]

[0009] That is, the present invention comprises the following: [1] A heat-shielding film having a heat-shielding layer laminated directly or via another layer on at least one surface of a base film, the thermal barrier layer is formed from a thermal barrier layer-forming composition containing antimony-doped tin oxide and a binder resin, the antimony-doped tin oxide contained in the thermal barrier layer has an average primary particle size of less than 50 nm, and the minimum diameter of the mandrel at which cracks occur in the thermal barrier layer when using a cylindrical mandrel method is less than 4 mm, Spectral transmittance T of the heat-shielding film at 1400 nm wavelength 1400nm A heat-shielding film having a thickness of 20% or less and a haze value of 8% or less. [2] In one embodiment, the heat-shielding film of the present invention has a base film that is a polyester film that is substantially free of particles, and has an easy-adhesion layer between the base film and the heat-shielding layer. [3] In one embodiment, the heat-shielding film of the present invention has a pencil hardness of the heat-shielding layer of H or higher. [4] In one embodiment, when the relationship between the thickness n of the heat-shielding layer and the heat-shielding property is expressed by the following (Equation 1), The value expressed by (Equation 1) is 20 or more (100-T 1400nm ) / n (Equation 1). [5] In one embodiment, the heat-shielding film of the present invention has a total light transmittance of 50% or more. [6] In one embodiment, the heat-shielding film of the present invention has a weight ratio of antimony-doped tin oxide to binder resin in the heat-shielding layer-forming composition of antimony-doped tin oxide:binder resin=70:30 to 99:1. [7] In one embodiment, the binder resin of the heat-shielding film of the present invention includes at least one resin selected from the group consisting of acrylate resins, acrylic resins, polyester resins, and polyurethane resins. [8] In another aspect, there is provided an agricultural heat shielding film having the heat shielding film according to the present invention. [9] In another aspect, a heat-shielding film for window lining is provided, which comprises the heat-shielding film according to the present invention. [Effects of the Invention]

[0010] The heat-shielding film of the present invention has high heat-shielding properties. In addition to having high heat-shielding properties, the heat-shielding film of the present invention also has high transparency and light transmittance. Furthermore, the heat-shielding film of the present invention has excellent abrasion resistance and coating strength, and therefore can be used for a long period of time without any deterioration in performance. Furthermore, the heat-shielding film of the present invention has excellent flexibility and therefore excellent handleability, and can suppress film cracking in the heat-shielding layer even when used in a shape such as a curtain or roll. Moreover, even when used in such a shape, the film can have high heat-shielding properties, transparency, and light transmittance. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present inventors have discovered a heat-shielding film having a heat-shielding layer laminated on at least one surface of a base film directly or via another layer, the thermal barrier layer is formed from a thermal barrier layer-forming composition containing antimony-doped tin oxide and a binder resin, the antimony-doped tin oxide contained in the thermal barrier layer has an average primary particle size of less than 50 nm, and the minimum diameter of a mandrel at which cracks occur in the thermal barrier layer by a cylindrical mandrel method is less than 4 mm, The spectral transmittance T of the heat-shielding film at a wavelength of 1400 nm 1400nm It has been found that a heat-shielding film having a viscosity of 20% or less and a haze value of 8% or less can provide a heat-shielding film that is excellent in heat-shielding properties, transparency, abrasion resistance and flexibility.

[0012] The heat-shielding film of the present invention has high heat-shielding properties. In addition to having high heat-shielding properties, the heat-shielding film of the present invention also has high transparency and light transmittance. Therefore, it can be suitably used for agricultural purposes and as a building material for automobile window coverings, residential window coverings, etc. Furthermore, it does not adversely affect the growth of horticultural crops, and when used for window coverings, it can let in outside light without blocking it. Furthermore, the heat-shielding film of the present invention has excellent abrasion resistance and coating strength, and therefore can be used for a long period of time without any deterioration in performance. Furthermore, the heat-shielding film of the present invention has excellent flexibility and therefore excellent handleability, and can suppress film cracking in the heat-shielding layer even when used in a shape such as a curtain or roll. Moreover, even when used in such a shape, the film can have high heat-shielding properties, transparency, and light transmittance. Furthermore, since the heat-shielding film of the present invention has excellent adhesion between the base film and the heat-shielding layer, there is no risk of the heat-shielding layer peeling even when used for a long period of time, and the heat-shielding film can be used without deteriorating in various performance properties. The present invention will be described in detail below.

[0013] (Film substrate) The film substrate used in the present invention is not particularly limited, and various polymer films can be used. It is preferable to use a polyester film substrate formed from a polyester. The polyester constituting the polyester film substrate is not particularly limited. A crystalline linear saturated polyester composed of an aromatic dibasic acid component and a diol component is preferable. For example, polyethylene terephthalate, polyethylene-2,6-naphthalate, polybutylene terephthalate, polytrimethylene terephthalate, or a copolymer primarily composed of these resin components is more preferable. Polyester film substrates formed from polyethylene terephthalate and polyethylene-2,6-naphthalate are particularly preferable, and polyester film substrates formed from polyethylene terephthalate are most preferable. The polyethylene terephthalate preferably contains 90 mol% or more, more preferably 95 mol% or more, of ethylene terephthalate repeating units, and may be copolymerized with small amounts of other dicarboxylic acid components or diol components. For example, from a cost perspective, those produced only from terephthalic acid and ethylene glycol are preferable. In addition, known additives such as antioxidants, light stabilizers, ultraviolet absorbers, crystallizing agents, etc. may be added within a range that does not impair the effects of the film of the present invention. The polyester film substrate is preferably a biaxially oriented polyester film substrate because of its high bidirectional elastic modulus.

[0014] The method for producing the polyester film substrate in the present invention is not particularly limited, and any conventionally commonly used method can be used. For example, the polyester can be melted in an extruder, extruded into a film, and cooled on a rotating cooling drum to obtain an unstretched film, which can then be biaxially stretched. A biaxially stretched film can be obtained by sequentially biaxially stretching a uniaxially stretched film in the longitudinal or transverse direction, or by simultaneously biaxially stretching an unstretched film in the longitudinal and transverse directions.

[0015] In the present invention, the stretching temperature during stretching of the polyester film is preferably equal to or higher than the second-order transition point (Tg) of the polyester, and the stretching is preferably 1 to 8 times, particularly 2 to 6 times, in both the longitudinal and transverse directions.

[0016] The polyester film substrate preferably has a thickness of 12 to 250 μm, more preferably 30 to 188 μm, and even more preferably 50 to 150 μm. A film substrate thickness of 12 μm or more is preferable because it is less likely to be deformed by heat during film production, processing, molding, etc., and the film has a moderate stiffness, making it easy to handle. On the other hand, a film substrate thickness of 250 μm or less is preferable because it prevents excessive amounts of film from being discarded after use, thereby reducing the environmental impact.

[0017] The catalyst for polycondensation used in producing the polyester resin is not particularly limited. For example, antimony trioxide is suitable because it is inexpensive and has excellent catalytic activity. It is also preferable to use a germanium compound or a titanium compound. More preferred polycondensation catalysts include catalysts containing aluminum and / or its compound and a phenolic compound, catalysts containing aluminum and / or its compound and a phosphorus compound, and catalysts containing an aluminum salt of a phosphorus compound.

[0018] Furthermore, the polyester film substrate in the present invention is not particularly limited in terms of its layer structure, and may be a single-layer polyester film substrate, a two-layer structure having different components, or a polyester film substrate consisting of at least three layers, including an outer layer and an inner layer.

[0019] In one embodiment, the substrate film is a polyester film that is substantially free of particles. Because the substrate film is substantially free of particles, the adhesion between the substrate and the heat-shielding layer can be increased, and peeling of the heat-shielding layer can be suppressed. In addition, the heat-shielding film can have excellent transparency. In the present invention, "substantially free of particles" means that when the surface of the substrate is observed under a microscope, the number of particles with a diameter of 10 μm or more is 10 / mm 2 This means that the surface roughness is 10 μm or less, or that no surface irregularities having a length of 10 μm or more are observed. This is because even if inorganic particles are not actively added to the film, contaminants from foreign matter, raw material resins, and dirt adhering to the lines and equipment during the film manufacturing process may peel off and become mixed into the film.

[0020] Preferably, the substrate film may be a polyester film that is substantially free of inorganic particles. Because the substrate film is substantially free of inorganic particles, the adhesion between the substrate and the heat shield layer can be improved, and peeling of the heat shield layer can be suppressed. In addition, high transparency (light transmittance) can be exhibited. In the present invention, "substantially free of inorganic particles" means that the content of inorganic elements is 50 ppm or less, preferably 10 ppm or less, and most preferably below the detection limit when quantified by fluorescent X-ray analysis. This is because even if inorganic particles are not actively added to the film, contaminants from foreign matter, raw material resins, and dirt adhering to the lines and equipment in the film manufacturing process may peel off and be mixed into the film.

[0021] <Easy adhesion layer> In the heat-shielding film of the present invention, the heat-shielding layer described below may be laminated directly on the film substrate. In one embodiment, it is preferable to form an easy-adhesion layer on the film substrate and provide a heat-shielding layer on the surface of the easy-adhesion layer opposite to the film substrate. By providing the heat-shielding layer via the easy-adhesion layer, the adhesion of the heat-shielding layer to the substrate is further improved, and peeling and film cracking of the heat-shielding layer are less likely to occur even when used outdoors for a long period of time.

[0022] The adhesive layer may be provided on one or both sides of the film substrate. For example, it is preferred that a heat shield layer is formed on at least one side of the film substrate via the adhesive layer. A resin coating layer may be provided on the surface of the film substrate opposite the heat-shielding layer. In this embodiment, for example, a second adhesive layer may be provided between the film substrate and the resin coating layer. For example, the resin coating layer may be an adhesive layer, a hydrophilic layer, or an antifouling layer.

[0023] The easy-adhesion layer is preferably formed by curing a composition containing a urethane resin having a polycarbonate structure and a branched structure, a crosslinking agent, and a polyester resin. The easy-adhesion layer is thought to be formed by curing a structure in which a urethane resin having a polycarbonate structure and a branched structure, and a polyester resin, are crosslinked by a crosslinking agent. Since it is difficult to express the crosslinked chemical structure itself, it is expressed as being formed by curing a composition containing a urethane resin having a polycarbonate structure and a branched structure, a crosslinking agent, and a polyester resin.

[0024] The urethane resin having a polycarbonate structure in the present invention preferably has a urethane bond portion derived from at least a polycarbonate polyol component and a polyisocyanate component, and a branched structure, and further contains a chain extender as needed. The branched structure referred to here is preferably introduced by forming a branched molecular chain structure after synthesis and polymerization due to the presence of three or more terminal functional groups in any of the raw material components constituting the molecular chain, as described above.

[0025] The urethane resin having a polycarbonate structure in the present invention preferably has 3 to 6 terminal functional groups in the molecular chain due to its branched structure, as this allows the resin to be stably dispersed in an aqueous solution and improves blocking resistance.

[0026] The lower limit of the mass ratio of the polycarbonate polyol component to the polyisocyanate component (mass of polycarbonate polyol component / mass of polyisocyanate component) when synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention is preferably 0.5, more preferably 0.6, even more preferably 0.7, particularly preferably 0.8, and most preferably 1.0. A ratio of 0.5 or more is preferable because adhesion to the heat shield layer can be improved. The upper limit of the mass ratio of the polycarbonate polyol component to the polyisocyanate component when synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention is preferably 3.0, more preferably 2.2, even more preferably 2.0, particularly preferably 1.7, and most preferably 1.5. A ratio of 3.0 or less is preferable because blocking resistance can be improved.

[0027] The polycarbonate polyol component used for synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention preferably contains an aliphatic polycarbonate polyol, which has excellent heat resistance and hydrolysis resistance. Examples of the aliphatic polycarbonate polyol include an aliphatic polycarbonate diol and an aliphatic polycarbonate triol, and the aliphatic polycarbonate diol is preferably used. Examples of the aliphatic polycarbonate diol used for synthesizing and polymerizing the urethane resin having a polycarbonate structure in the present invention include aliphatic polycarbonate diols obtained by reacting one or more diols such as ethylene glycol, propylene glycol, 1,3-propanediol, 1,4-butanediol, 1,5-pentanediol, 3-methyl-1,5-pentanediol, 1,6-hexanediol, 1,9-nonanediol, 1,8-nonanediol, neopentyl glycol, diethylene glycol, and dipropylene glycol with carbonates such as dimethyl carbonate, ethylene carbonate, and phosgene.

[0028] The number average molecular weight of the polycarbonate polyol in the present invention is preferably 1000 to 3000, more preferably 1200 to 2900, and most preferably 1500 to 2800. A molecular weight of 1000 or more is preferable because the adhesion of the heat shield layer can be improved. A molecular weight of 3000 or less is preferable because the blocking resistance can be improved.

[0029] Examples of polyisocyanates used in the synthesis and polymerization of the urethane resin having a polycarbonate structure in the present invention include aromatic aliphatic diisocyanates such as xylylene diisocyanate, alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane, aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate, and polyisocyanates obtained by pre-adding one or more of these compounds with trimethylolpropane or the like. The use of the aromatic aliphatic diisocyanates, alicyclic diisocyanates, or aliphatic diisocyanates described above is preferred because it does not cause yellowing problems. Furthermore, it is also preferred because it does not form an overly rigid coating film, can alleviate stress due to thermal shrinkage of the polyester film substrate, and provides good adhesion.

[0030] Examples of chain extenders include glycols such as ethylene glycol, diethylene glycol, 1,4-butanediol, neopentyl glycol, and 1,6-hexanediol; polyhydric alcohols such as glycerin, trimethylolpropane, and pentaerythritol; diamines such as ethylenediamine, hexamethylenediamine, and piperazine; amino alcohols such as monoethanolamine and diethanolamine; thiodiglycols such as thiodiethylene glycol; and water.

[0031] To form a branched structure in the urethane resin, for example, a method can be preferably employed in which the polycarbonate polyol component, polyisocyanate, and chain extender are reacted at an appropriate temperature for an appropriate time, and then a compound having a tri- or higher functional hydroxyl group or isocyanate group is added, and the reaction is further allowed to proceed.

[0032] Specific examples of compounds having three or more functional hydroxyl groups include caprolactone triol, glycerol, trimethylolpropane, butanetriol, hexanetriol, 1,2,3-hexanetriol, 1,2,3-pentanetriol, 1,3,4-hexanetriol, 1,3,4-pentanetriol, 1,3,5-hexanetriol, 1,3,5-pentanetriol, polyethertriol, etc. Examples of the polyethertriol include compounds obtained by addition polymerization of one or more monomers such as ethylene oxide, propylene oxide, butylene oxide, amylene oxide, glycidyl ether, methyl glycidyl ether, t-butyl glycidyl ether, phenyl glycidyl ether, etc., using one or more compounds having three active hydrogens, such as alcohols such as glycerin and trimethylolpropane, and diethylenetriamine, as initiators.

[0033] A specific example of a compound having a tri- or higher functional isocyanate group is a polyisocyanate compound having at least three isocyanate (NCO) groups in one molecule. In the present invention, the tri- or higher functional isocyanate compound includes biuret compounds, nurate compounds, adduct compounds, and the like obtained by modifying isocyanate monomers having two isocyanate groups, such as aromatic diisocyanates, aliphatic diisocyanates, araliphatic diisocyanates, and alicyclic diisocyanates. Examples of aromatic diisocyanates include 1,3-phenylene diisocyanate, 4,4'-diphenyl diisocyanate, 1,4-phenylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-toluidine diisocyanate, dianisidine diisocyanate, and 4,4'-diphenyl ether diisocyanate. Examples of aliphatic diisocyanates include trimethylene diisocyanate, tetramethylene diisocyanate, hexamethylene diisocyanate, pentamethylene diisocyanate, 1,2-propylene diisocyanate, 2,3-butylene diisocyanate, 1,3-butylene diisocyanate, dodecamethylene diisocyanate, and 2,4,4-trimethylhexamethylene diisocyanate. Examples of the aromatic aliphatic diisocyanate include xylylene diisocyanate, ω,ω'-diisocyanate-1,4-diethylbenzene, 1,4-tetramethylxylylene diisocyanate, and 1,3-tetramethylxylylene diisocyanate. Examples of alicyclic diisocyanates include 3-isocyanatomethyl-3,5,5-trimethylcyclohexyl isocyanate (also known as IPDI, isophorone diisocyanate), 1,3-cyclopentane diisocyanate, 1,3-cyclohexane diisocyanate, 1,4-cyclohexane diisocyanate, methyl-2,4-cyclohexane diisocyanate, methyl-2,6-cyclohexane diisocyanate, 4,4'-methylenebis(cyclohexyl isocyanate), and 1,4-bis(isocyanatomethyl)cyclohexane. The biuret form is a self-condensation product having a biuret bond formed by the self-condensation of an isocyanate monomer, and examples thereof include the biuret form of hexamethylene diisocyanate. The nurate is a trimer of an isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate. The adduct refers to a tri- or higher functional isocyanate compound obtained by reacting the above-mentioned isocyanate monomer with a tri- or higher functional low-molecular-weight active hydrogen-containing compound, and examples thereof include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, and a compound obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0034] Examples of chain extenders having three or more functional groups include alcohols having three or more hydroxyl groups, such as trimethylolpropane and pentaerythritol, which are mentioned in the above description of chain extenders.

[0035] The adhesive layer of the present invention is preferably formed by an in-line coating method described below using an aqueous coating liquid. Therefore, the urethane resin of the present invention is preferably water-soluble or water-dispersible. The term "water-soluble or water-dispersible" means that the resin is dispersible in water or an aqueous solution containing less than 50% by mass of a water-soluble organic solvent.

[0036] To impart water dispersibility to urethane resins, sulfonic acid (salt) groups or carboxylic acid (salt) groups can be introduced (copolymerized) into the urethane molecular structure. To maintain moisture resistance, it is preferable to introduce weakly acidic carboxylic acid (salt) groups. Nonionic groups such as polyoxyalkylene groups can also be introduced.

[0037] To introduce carboxylic acid (salt) groups into a urethane resin, for example, a polyol compound having a carboxylic acid group, such as dimethylolpropanoic acid or dimethylolbutanoic acid, is introduced as a copolymerization component and neutralized with a salt-forming agent. Specific examples of salt-forming agents include ammonia, trialkylamines such as trimethylamine, triethylamine, triisopropylamine, tri-n-propylamine, and tri-n-butylamine, N-alkylmorpholines such as N-methylmorpholine and N-ethylmorpholine, and N-dialkylalkanolamines such as N-dimethylethanolamine and N-diethylethanolamine. These can be used alone or in combination of two or more.

[0038] When a polyol compound having a carboxylic acid (salt) group is used as a copolymerization component to impart water dispersibility, the molar ratio of the polyol compound having a carboxylic acid (salt) group in the urethane resin is preferably 3 to 60 mol%, and more preferably 5 to 40 mol%, when the total polyisocyanate components of the urethane resin are taken as 100 mol%. A molar ratio of 3 mol% or more is preferred because water dispersibility is obtained. Furthermore, a molar ratio of 60 mol% or less is preferred because water resistance is maintained and moist heat resistance is obtained.

[0039] The urethane resin of the present invention may have a blocked isocyanate structure at the end to improve hardness.

[0040] In the present invention, the crosslinking agent contained in the composition for forming an easy-adhesion layer is preferably a blocked isocyanate, more preferably a tri- or higher functional blocked isocyanate, and particularly preferably a tetra- or higher functional blocked isocyanate, which improves blocking resistance and adhesion to the heat shield layer.

[0041] The lower limit of the NCO equivalent of the blocked isocyanate is preferably 100, more preferably 120, even more preferably 130, particularly preferably 140, and most preferably 150. An NCO equivalent of 100 or more is preferred because there is no risk of coating cracking. The upper limit of the NCO equivalent is preferably 500, more preferably 400, even more preferably 380, particularly preferably 350, and most preferably 300. An NCO equivalent of 500 or less is preferred because blocking resistance is maintained.

[0042] The lower limit of the boiling point of the blocking agent for the blocked isocyanate is preferably 150°C, more preferably 160°C, even more preferably 180°C, particularly preferably 200°C, and most preferably 210°C. The higher the boiling point of the blocking agent, the more suppressed is the volatilization of the blocking agent by heat addition during the drying process after application of the coating liquid or during the film formation process in the case of an in-line coating method, thereby suppressing the occurrence of minute unevenness on the coated surface and improving the transparency of the film. The upper limit of the boiling point of the blocking agent is not particularly limited, but from the viewpoint of productivity, it is thought that the upper limit is about 300°C. Since the boiling point is related to the molecular weight, in order to increase the boiling point of the blocking agent, it is preferable to use a blocking agent with a large molecular weight, and the molecular weight of the blocking agent is preferably 50 or more, more preferably 60 or more, and even more preferably 80 or more.

[0043] The upper limit of the dissociation temperature of the blocking agent is preferably 200°C, more preferably 180°C, even more preferably 160°C, particularly preferably 150°C, and most preferably 120°C. The blocking agent dissociates from the functional group by thermal addition during the drying process after application of the coating solution or during the film formation process in the case of an in-line coating method, generating a regenerated isocyanate group. This allows the crosslinking reaction with urethane resins and the like to proceed, improving adhesion. When the dissociation temperature of the blocked isocyanate is below the above temperature, the dissociation of the blocking agent proceeds sufficiently, resulting in good adhesion, particularly good moist heat resistance.

[0044] Examples of blocking agents used in the blocked isocyanate of the present invention, which have a dissociation temperature of 120°C or lower and a boiling point of 150°C or higher, include bisulfite compounds such as sodium bisulfite, pyrazole compounds such as 3,5-dimethylpyrazole, 3-methylpyrazole, 4-bromo-3,5-dimethylpyrazole, and 4-nitro-3,5-dimethylpyrazole, active methylene compounds such as malonic acid diesters (dimethyl malonate, diethyl malonate, di-n-butyl malonate, and di-2-ethylhexyl malonate), methyl ethyl ketone, and triazole compounds such as 1,2,4-triazole. Among these, pyrazole compounds are preferred from the viewpoints of wet heat resistance and yellowing resistance.

[0045] The tri- or higher functional polyisocyanate, which is the precursor of the blocked isocyanate of the present invention, can be suitably obtained by introducing an isocyanate monomer, such as a biuret, nurate, or adduct obtained by modifying an isocyanate monomer, such as an aromatic diisocyanate, aliphatic diisocyanate, araliphatic diisocyanate, or alicyclic diisocyanate, each having two isocyanate groups. The biuret form is a self-condensation product having a biuret bond formed by the self-condensation of an isocyanate monomer, and examples thereof include the biuret form of hexamethylene diisocyanate. The nurate is a trimer of an isocyanate monomer, and examples thereof include a trimer of hexamethylene diisocyanate, a trimer of isophorone diisocyanate, and a trimer of tolylene diisocyanate. The adduct refers to a tri- or higher functional isocyanate compound obtained by reacting an isocyanate monomer with a tri- or higher functional low-molecular-weight active hydrogen-containing compound, and examples thereof include a compound obtained by reacting trimethylolpropane with hexamethylene diisocyanate, a compound obtained by reacting trimethylolpropane with tolylene diisocyanate, a compound obtained by reacting trimethylolpropane with xylylene diisocyanate, and a compound obtained by reacting trimethylolpropane with isophorone diisocyanate.

[0046] Examples of the isocyanate monomer include 2,4-tolylene diisocyanate, 2,6-tolylene diisocyanate, 4,4'-diphenylmethane diisocyanate, 2,4'-diphenylmethane diisocyanate, 2,2'-diphenylmethane diisocyanate, 1,5-naphthylene diisocyanate, 1,4-naphthylene diisocyanate, phenylene diisocyanate, tetramethylxylylene diisocyanate, 4,4'-diphenylether diisocyanate, 2-nitrodiphenyl-4,4'-diisocyanate, 2,2'-diphenylpropane-4,4'-diisocyanate, 3,3' Examples of suitable diisocyanates include aromatic diisocyanates such as 4,4'-dimethyldiphenylmethane-4,4'-diisocyanate, 4,4'-diphenylpropane diisocyanate, and 3,3'-dimethoxydiphenyl-4,4'-diisocyanate; aromatic aliphatic diisocyanates such as xylylene diisocyanate; alicyclic diisocyanates such as isophorone diisocyanate, 4,4-dicyclohexylmethane diisocyanate, and 1,3-bis(isocyanatomethyl)cyclohexane; and aliphatic diisocyanates such as hexamethylene diisocyanate and 2,2,4-trimethylhexamethylene diisocyanate. From the viewpoints of transparency, adhesion, and moist heat resistance, aliphatic and alicyclic isocyanates and their modified products are preferred, and are preferred for optical applications that require high transparency and no yellowing.

[0047] The blocked isocyanate of the present invention can introduce hydrophilic groups into the precursor polyisocyanate to impart water solubility or water dispersibility. Examples of hydrophilic groups include (1) quaternary ammonium salts of dialkylamino alcohols and quaternary ammonium salts of dialkylaminoalkylamines, (2) sulfonates, carboxylates, and phosphates, and (3) polyethylene glycols and polypropylene glycols capped at one end with an alkyl group. When a hydrophilic moiety is introduced, the resulting polymer will be (1) cationic, (2) anionic, or (3) nonionic. Since many other water-soluble resins are anionic, anionic or nonionic polymers are preferred because they are easily compatible with other resins. Furthermore, anionic polymers have excellent compatibility with other resins, and nonionic polymers lack ionic hydrophilic groups, which improves resistance to moist heat.

[0048] The anionic hydrophilic group preferably has a hydroxyl group for introduction into polyisocyanate and a carboxylic acid group for imparting hydrophilicity. Examples include glycolic acid, lactic acid, tartaric acid, citric acid, hydroxybutyric acid, hydroxyvaleric acid, hydroxypivalic acid, dimethylolacetic acid, dimethylolpropanoic acid, dimethylolbutanoic acid, and polycaprolactone having a carboxylic acid group. To neutralize the carboxylic acid group, an organic amine compound is preferred. Examples include linear or branched primary, secondary, or tertiary amines having 1 to 20 carbon atoms, such as ammonia, methylamine, ethylamine, propylamine, isopropylamine, butylamine, 2-ethylhexylamine, cyclohexylamine, dimethylamine, diethylamine, dipropylamine, diisopropylamine, dibutylamine, trimethylamine, triethylamine, triisopropylamine, tributylamine, and ethylenediamine; cyclic amines, such as morpholine, N-alkylmorpholine, and pyridine; and hydroxyl group-containing amines, such as monoisopropanolamine, methylethanolamine, methylisopropanolamine, dimethylethanolamine, diisopropanolamine, diethanolamine, triethanolamine, diethylethanolamine, and triethanolamine.

[0049] The nonionic hydrophilic group preferably has 3 to 50 repeating units of ethylene oxide and / or propylene oxide in polyethylene glycol or polypropylene glycol capped at one end with an alkyl group, more preferably 5 to 30. Small repeating units result in poor compatibility with resins and increased haze, while large repeating units may result in reduced adhesion under high temperature and humidity conditions. To improve water dispersibility, the blocked isocyanate of the present invention can be supplemented with nonionic, anionic, cationic, or amphoteric surfactants. Examples of such surfactants include nonionic surfactants such as polyethylene glycol and polyhydric alcohol fatty acid esters, anionic surfactants such as fatty acid salts, alkyl sulfates, alkylbenzene sulfonates, sulfosuccinates, and alkyl phosphates, cationic surfactants such as alkylamine salts and alkylbetaines, and surfactants such as amine carboxylates, amine sulfonates, and sulfate ester salts.

[0050] In addition to water, a water-soluble organic solvent may also be contained. For example, the organic solvent used in the reaction may be removed, and another organic solvent may be added.

[0051] In one embodiment of the present invention, the base film is a polyester film, and an easy-adhesion layer is provided between the base film and the heat-shielding layer, and the easy-adhesion layer contains a polyester resin. This embodiment provides even better adhesion between the substrate and the heat shield layer, making it less likely that the heat shield layer will peel off or crack even when used outdoors for a long period of time. In yet another embodiment, the substrate film is a polyester film that is substantially free of particles, and an easy-adhesion layer is provided between the substrate film and the heat-shielding layer, and the easy-adhesion layer contains a polyester resin. For example, the substrate film is substantially free of inorganic particles. This embodiment further improves the adhesion between the substrate and the heat-shielding layer, making it less likely for the heat-shielding layer to peel or crack even when used outdoors for a long period of time. Furthermore, because the substrate exhibits high smoothness, the adhesion between the substrate and the easy-adhesion layer can be further improved, and the flexibility of the present invention can be more effectively exhibited. For example, even when the heat-shielding film is attached to a curved surface, delamination of the heat-shielding film can be suppressed. Furthermore, since the base film is substantially particle-free, it exhibits excellent transparency, and is therefore preferable for agricultural use as it does not pose a risk of interfering with food growth, and for window coverings as it provides excellent visibility without blocking outside light. Furthermore, since the base film does not substantially contain particles, it is easy to recycle after use and is therefore environmentally friendly, which is preferable. Furthermore, since the base film does not substantially contain particles, it is possible to prevent particles contained in the film from falling off during long-term use.

[0052] The polyester resin used to form the easy-adhesion layer in the present invention may be a linear one, but is more preferably a polyester resin containing a dicarboxylic acid and a diol having a branched structure as constituent components. The dicarboxylic acid referred to here includes aliphatic dicarboxylic acids such as adipic acid and sebacic acid, and aromatic dicarboxylic acids such as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid, as well as terephthalic acid, isophthalic acid, phthalic acid, and 2,6-naphthalenedicarboxylic acid. Furthermore, the branched glycol refers to a diol having a branched alkyl group, and examples thereof include 2,2-dimethyl-1,3-propanediol, 2-methyl-2-ethyl-1,3-propanediol, 2-methyl-2-butyl-1,3-propanediol, 2-methyl-2-propyl-1,3-propanediol, 2-methyl-2-isopropyl-1,3-propanediol, 2-methyl-2-n-hexyl-1,3-propanediol, 2,2-diethyl-1,3-propanediol, 2-ethyl-2-n-butyl-1,3-propanediol, 2-ethyl-2-n-hexyl-1,3-propanediol, 2,2-di-n-butyl-1,3-propanediol, 2-n-butyl-2-propyl-1,3-propanediol, and 2,2-di-n-hexyl-1,3-propanediol.

[0053] The polyester resin preferably contains the branched glycol component, which is a more preferred embodiment of the present invention, at a ratio of 10 mol % or more, and more preferably 20 mol % or more, of the total glycol components. If the ratio is 10 mol % or less, the crystallinity may be high, and the adhesiveness of the easy-adhesion layer may be reduced. The upper limit of the glycol component content of the total glycol components is preferably 80 mol % or less, and more preferably 70 mass %. If the ratio is 80 mol % or more, the concentration of oligomers, which are by-products, may increase, which may affect the transparency of the easy-adhesion layer. Ethylene glycol is the most preferred glycol component other than the above compounds. Small amounts of diethylene glycol, propylene glycol, butanediol, hexanediol, 1,4-cyclohexanedimethanol, etc. may also be used.

[0054] The dicarboxylic acid as a constituent component of the polyester resin is most preferably terephthalic acid or isophthalic acid. In addition to the dicarboxylic acids, 5-sulfoisophthalic acid or the like is preferably copolymerized in a range of 1 to 10 mol % to impart water dispersibility to the copolymerized polyester resin. Examples include sulfoterephthalic acid, 5-sulfoisophthalic acid, and 5-sodium sulfoisophthalic acid. A polyester resin containing a dicarboxylic acid having a naphthalene skeleton may be used, but in order to prevent a decrease in the adhesion of the heat shield layer, the quantitative proportion of the dicarboxylic acid is preferably 5 mol % or less of the total carboxylic acid components, and it may not be used at all. The polyester resin contained in the easy-adhesion layer and the polyester film used for the base film may be the same polyester resin, or polyester resins having different physical properties may be appropriately selected.

[0055] When the total solid content of the polyester resin, urethane resin having a polycarbonate structure, and crosslinking agent in the coating solution is taken as 100% by mass, the lower limit of the content of the crosslinking agent is preferably 5% by mass, more preferably 7% by mass, even more preferably 10% by mass, and most preferably 12% by mass. A content of 5% by mass or more is preferable because it can improve blocking resistance. The upper limit of the content of the crosslinking agent is preferably 50% by mass, more preferably 40% by mass, even more preferably 35% by mass, and most preferably 30% by mass. A content of 50% by mass or less is preferable because it increases transparency.

[0056] When the total solid content of the polyester resin, urethane resin having a polycarbonate structure, and crosslinking agent in the coating solution is taken as 100% by mass, the lower limit of the content of the urethane resin having a polycarbonate structure is preferably 5% by mass. A content of 5% by mass or more is preferred because adhesion to the heat shield layer can be improved. The upper limit of the content of the urethane resin having a polycarbonate structure is preferably 50% by mass, more preferably 40% by mass, even more preferably 30% by mass, and most preferably 20% by mass. A urethane resin content of 50% by mass or less is preferred because blocking resistance can be improved.

[0057] When the total solid content of the polyester resin, urethane resin, and crosslinking agent in the coating solution is 100% by mass, the content of the polyester resin is preferably 10% by mass or more, more preferably 20% by mass or more, even more preferably 30% by mass or more, particularly preferably 35% by mass or more, and most preferably 40% by mass or more. When the content of the polyester resin is 10% by mass or more, the adhesion between the easy-adhesion layer and the polyester film substrate becomes good, which is preferable. The content of the polyester resin is preferably 80% by mass or less, more preferably 75% by mass or less, and even more preferably 70% by mass or less. A polyester resin content of 80% by mass or less is preferred because the heat shield layer has good resistance to moist heat, and a polyester resin content of 10% by mass or more is preferred because the heat shield layer has good adhesion to the substrate.

[0058] In the easy-adhesion layer of the present invention, known additives such as surfactants, antioxidants, heat stabilizers, weather stabilizers, ultraviolet absorbers, organic lubricants, pigments, dyes, organic or inorganic particles, antistatic agents, nucleating agents, etc. may be added within a range that does not impair the effects of the present invention.

[0059] In the present invention, in order to further improve the blocking resistance of the easy-adhesion layer, it is also a preferred embodiment to add particles to the easy-adhesion layer.The particles to be contained in the easy-adhesion layer in the present invention include, for example, titanium oxide, barium sulfate, calcium carbonate, calcium sulfate, silica, alumina, talc, kaolin, clay, etc., or mixtures thereof, and further include other general inorganic particles such as inorganic particles used in combination with calcium phosphate, mica, hectorite, zirconia, tungsten oxide, lithium fluoride, calcium fluoride, etc., and organic polymer particles such as styrene-based, acrylic-based, melamine-based, benzoguanamine-based, silicone-based, etc.

[0060] The average particle size of the particles in the easy-adhesion layer (average particle size based on the number of particles as measured by a scanning electron microscope (SEM); the same applies hereinafter) is preferably 0.04 to 2.0 μm, more preferably 0.1 to 1.0 μm. When the average particle size of the inactive particles is 0.04 μm or more, it is easy to form irregularities on the film surface, which improves the handling properties of the film, such as slipperiness and winding ability, and improves the processability during lamination, which is preferable. On the other hand, when the average particle size of the inactive particles is 2.0 μm or less, it is preferable that the particles are less likely to fall off. The particle concentration in the easy-adhesion layer is preferably 1 to 20 mass % of the solid components.

[0061] The average particle size of the particles was measured by observing the particles on the cross section of the laminated polyester film with a scanning electron microscope, observing 30 particles, and determining the average particle size as the average value.

[0062] The shape of the particles is not particularly limited as long as it satisfies the objectives of the present invention, and spherical particles and irregular, non-spherical particles can be used. The particle size of irregular particles can be calculated as the equivalent circle diameter. The equivalent circle diameter is the value obtained by dividing the observed particle area by π, calculating the square root, and then multiplying it by two.

[0063] The adhesive layer can be formed after or during the production process of the film substrate. From the viewpoint of productivity, it is particularly preferred to form the adhesive layer at any stage of the film production process, i.e., by applying a coating liquid to at least one surface of an unstretched or uniaxially stretched PET film.

[0064] Any known method can be used to apply this coating solution to the PET film. Examples include reverse roll coating, gravure coating, kiss coating, die coating, roll brushing, spray coating, air knife coating, wire bar coating, pipe doctor coating, impregnation coating, and curtain coating. These methods can be used alone or in combination.

[0065] In the present invention, the thickness of the easy-adhesion layer can be appropriately set in the range of 0.001 to 2.00 μm, but in order to achieve both processability and adhesiveness, it is preferably in the range of 0.01 to 1.00 μm, more preferably 0.02 to 0.80 μm, and even more preferably 0.05 to 0.50 μm. When the thickness of the easy-adhesion layer is 0.001 μm or more, good adhesiveness is obtained, which is preferable. When the thickness of the easy-adhesion layer is 2.00 μm or less, blocking is less likely to occur, which is preferable.

[0066] <Heat barrier layer> The heat-shielding film of the present invention has a heat-shielding layer laminated directly or via another layer on at least one surface of a substrate film. The heat-shielding layer is a layer formed from a cured product of a heat-shielding layer-forming composition containing antimony-doped tin oxide and a binder resin.

[0067] The antimony-doped tin oxide has an average primary particle size of less than 50 nm, preferably 1 nm or more and less than 50 nm, more preferably 1 nm or more and 40 nm or less, for example, 1 nm or more and 30 nm or less, even more preferably 1 nm or more and less than 20 nm, and may be 1 nm or more and 10 nm or less, for example, 1 nm or more and less than 10 nm is particularly preferred. A primary average particle size of 1 nm or more is preferred because it prevents aggregation of the antimony-doped tin oxide and impairs the transparency of the heat-shielding layer. A primary particle size of less than 50 nm is preferred because it allows the antimony-doped tin oxide to be uniformly distributed in the heat-shielding layer, resulting in excellent heat-shielding properties. The average primary particle size was measured by cutting a resin-embedded heat-shielding film with a microtome and observing the cross section of the heat-shielding layer with a TEM.

[0068] It is preferable that the antimony-doped tin oxide be uniformly distributed in the heat-shielding layer from the viewpoints of heat-shielding properties and transparency. Furthermore, if the antimony-doped tin oxide is uniformly distributed in the heat-shielding layer, the cross-linking reaction of the binder component contained in the heat-shielding layer also proceeds efficiently, resulting in a heat-shielding layer with high coating strength, which is also preferable. The distribution of the antimony-doped tin oxide in the heat-shielding layer can be confirmed from the degree of brightness when the cross section of the heat-shielding film is observed with a TEM, as described above.

[0069] In the present invention, "antimony-doped tin oxide is uniformly distributed in the thermal barrier layer" can take various forms. In one embodiment, the antimony-doped tin oxide may be uniformly distributed over the entire surface of the thermal barrier layer. For example, when the thermal barrier layer has a single-layer structure, the antimony-doped tin oxide may be uniformly distributed over at least one surface region. Alternatively, the antimony-doped tin oxide may be uniformly distributed over both surface regions of the thermal barrier layer. For example, when the thermal barrier layer has a multi-layer structure, the antimony-doped tin oxide may be uniformly distributed in the outermost layer or in an intermediate region in the thickness direction of the thermal barrier layer. In one embodiment, the antimony-doped tin oxide may be uniformly distributed throughout the thickness of the thermal barrier layer, that is, throughout the entire thermal barrier layer. In one embodiment, the antimony-doped tin oxide may be uniformly distributed at a higher density in the surface region of the thermal barrier layer. For example, the density of the antimony-doped tin oxide on the substrate film side of the thermal barrier layer may be set to a different value from the density of the antimony-doped tin oxide on the surface of the thermal barrier layer opposite the substrate (the surface in contact with the atmosphere).

[0070] The binder resin contained in the heat shield layer preferably contains at least one selected from the group consisting of acrylate resins, acrylic resins, polyester resins, and polyurethane resins, more preferably selected from the group consisting of acrylate resins and acrylic resins, and even more preferably selected from acrylate resins. Although not intended to be limited to a particular theory, by using an acrylate resin as the binder resin, the binder resins crosslink with each other while incorporating antimony-doped tin oxide particles, improving the coating strength and resulting in a heat shield layer with excellent abrasion resistance, substrate adhesion, and flexibility.

[0071] Examples of the acrylate resin in the present invention include an acrylate compound, a methacrylate compound, and a urethane acrylate compound. When an acrylate resin is used as a binder resin, each of these can be suitably used. It is most preferable to use a urethane acrylate compound. By using a urethane acrylate compound, cure shrinkage can be suppressed and a heat shield layer with excellent flexibility and substrate adhesion can be obtained.

[0072] The binder resin may be a monomer, oligomer, or polymer. From the viewpoint of solubility in organic solvents and ease of handling, it is preferable to use a monomer or oligomer. These may be used alone or in combination of two or more.

[0073] When a monomer is used as the (meth)acrylate compound, for example, trimethylolpropane tri(meth)acrylate, pentaerythritol tri(meth)acrylate, pentaerythritol tetra(meth)acrylate, dipentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, dipentaerythritol hexa(meth)acrylate, ethoxylated isocyanuric acid tri(meth)acrylate, caprolactone-modified dipentaerythritol hexa(meth)acrylate, etc. The term "(meth)acrylate compound" is meant to encompass both methacrylate and acrylate.

[0074] When an oligomer is used as the (meth)acrylate compound, examples thereof include polyfunctional (meth)acrylate oligomers, polyester acrylate oligomers, epoxy acrylate oligomers, polyether acrylate oligomers, polybutadiene acrylate oligomers, and silicone acrylate oligomers.

[0075] The urethane acrylate compound used in the present invention refers to a compound having a urethane bond and one or more radically curable functional groups selected from an acryloyl group and a methacryloyl group in the molecular chain. The synthesis method is not particularly limited, but it can be obtained, for example, by reacting a polyhydric alcohol and an organic polyisocyanate with a hydroxyacrylate.

[0076] Examples of the polyhydric alcohols include neopentyl glycol, 3-methyl-1,5-pentanediol, ethylene glycol, propylene glycol, 1,4-butanediol, 1,6-hexanediol, trimethylolpropane, pentaerythritol, tricyclodecanedimethylol, and bis-[hydroxymethyl]cyclohexane; polyester polyols obtained by reacting the polyhydric alcohols with polybasic acids (e.g., succinic acid, phthalic acid, hexahydrophthalic anhydride, terephthalic acid, adipic acid, azelaic acid, and tetrahydrophthalic anhydride); polycaprolactone polyols obtained by reacting the polyhydric alcohols with ε-caprolactone; polycarbonate polyols (e.g., polycarbonate diol obtained by reacting 1,6-hexanediol with diphenyl carbonate); and polyether polyols. Examples of the polyether polyols include polyethylene glycol, polypropylene glycol, polytetramethylene glycol, and ethylene oxide-modified bisphenol A.

[0077] Examples of the organic polyisocyanate include isocyanate compounds such as isophorone diisocyanate, hexamethylene diisocyanate, tolylene diisocyanate, xylene diisocyanate, diphenylmethane-4,4'-diisocyanate, and dicyclopentanyl isocyanate, as well as adducts of these isocyanate compounds and polymers of these isocyanates.

[0078] Examples of the hydroxy(meth)acrylate compound include pentaerythritol di(meth)acrylate, pentaerythritol tri(meth)acrylate, dipentaerythritol tetra(meth)acrylate, dipentaerythritol penta(meth)acrylate, hydroxyethyl(meth)acrylate, hydroxypropyl(meth)acrylate, hydroxybutyl(meth)acrylate, dimethylolcyclohexyl mono(meth)acrylate, hydroxycaprolactone(meth)acrylate, etc. Among these, pentaerythritol tri(meth)acrylate and dipentaerythritol penta(meth)acrylate are preferred in terms of hardness.

[0079] The acrylate compound used in the present invention, such as a urethane acrylate compound, can also be commercially available. Examples of commercially available products include Mitsubishi Chemical's UV1700B (10 functional groups), UV7620EA (9 functional groups), UV7610B (9 functional groups), UV7600B (6 functional groups), and UV7650B (5 functional groups), Nippon Kayaku's DPHA40H (10 functional groups), and UX5003 (6 functional groups), Arakawa Chemical's Beamset 577 (6 functional groups), Taisei Fine Chemical's 8UX-015A (15 functional groups), and Shin-Nakamura Chemical's A-701A (2 functional groups), A-TMM-3 (3 functional groups), A-TMMT (4 functional groups), A-DPH (6 functional groups), and U15HA (15 functional groups).

[0080] The number of functional groups of the binder resin is preferably 2 or more, more preferably 3 or more, and even more preferably 4 or more. Bifunctional or more is preferable because the binder resins crosslink with each other, resulting in a heat shield layer with excellent curing properties and excellent coating strength. The greater the number of functional groups, the better the curing properties. It is most preferable to use a polyfunctional urethane acrylate compound, for example, one with 20 or less and 16 or less functional groups, since this can prevent excessive curling and adverse effects on substrate adhesion and flexibility.

[0081] The thickness of the heat-shielding layer is preferably 5 μm or less, more preferably 4 μm or less, and even more preferably 3 μm or less. A release layer thickness of 5 μm or less is preferred because it provides excellent flexibility and substrate adhesion. The smaller the thickness, the more preferred it is from the viewpoint of flexibility and substrate adhesion. For example, in order to achieve excellent heat-shielding properties and coating strength, a thickness of 0.5 μm or more is preferred.

[0082] The content of antimony-doped tin oxide contained in the thermal barrier layer is important for obtaining a thermal barrier layer with excellent thermal barrier properties. Increasing the content can improve the thermal barrier properties. On the other hand, when the thermal barrier properties are improved, the thickness of the thermal barrier layer tends to increase as the content of antimony-doped tin oxide increases, which may impair the mechanical properties of the thermal barrier layer. In contrast, in the present invention, the content of antimony-doped tin oxide contained in the heat-shielding layer is increased, resulting in high heat-shielding properties, as well as high flexibility, substrate adhesion, and transparency. For example, the heat-shielding layer of the present invention has a thickness of 5 μm or less, which satisfies all of high heat-shielding properties, high flexibility, substrate adhesion, and transparency, and can also be made even thinner. This reduces adverse effects on food growth and improves durability when used repeatedly outdoors. Furthermore, the weight of the heat-shielding film itself can be reduced, which can contribute to fuel savings and reduce environmental impact, for example, in applications such as automotive window coverings. As described above, in the present invention, the use of fine antimony-doped tin oxide having a primary particle size of less than 50 nm makes it possible to provide a heat shielding layer having excellent heat shielding properties while keeping the film thickness thin. Furthermore, the use of antimony-doped tin oxide having a primary particle size of less than 50 nm facilitates the crosslinking reaction of the binder resin, resulting in a heat shielding layer having excellent coating strength.

[0083] The relationship between the film thickness and the thermal barrier properties can be expressed by the following formula 1. In the formula, the film thickness of the thermal barrier layer is n (μm), and T 1400nmmeans the spectral transmittance (%) at a wavelength of 1400 nm. The larger the value represented by Formula 1, the higher the heat-shielding performance of the thin heat-shielding layer. The value of Formula 1 is preferably 20 or more, more preferably 25 or more, and even more preferably 30 or more, with the larger the value, the more preferable. A value of Formula 1 of 20 or more is preferred because the heat-shielding properties, flexibility, and adhesion to the substrate are excellent, and the durability is also excellent when used outdoors for a long period of time. (100-T 1400nm ) / n...(Formula 1)

[0084] In one embodiment, the relationship between the thickness n of the heat shield layer and the heat shielding property, expressed by the following (Equation 1), may be 90 or less, for example, 80 or less.

[0085] The surface roughness (Sa) of the surface of the heat-shielding layer opposite the film substrate is preferably 10 nm or less, more preferably 8 nm or less, and even more preferably 5 nm or less. A surface roughness of 10 nm or less is preferable because when the heat-shielding film is used in curtain or roll form, the heat-shielding layer of the heat-shielding film and the surface of the substrate film opposite the heat-shielding layer may rub against each other, causing scratches and impairing transparency. The smaller the surface roughness, the better. For example, a surface roughness of 0.1 nm or more is preferable in consideration of the slipperiness with the transport rolls in the heat-shielding film manufacturing process.

[0086] The content of antimony-doped tin oxide and binder resin in the heat-shield layer-forming composition is preferably antimony-doped tin oxide:binder resin = weight ratio = 70:30 to 99:1, more preferably 80:20 to 99:1, and particularly preferably 85:15 to 98:2. By setting the content within the above range, a heat-shield layer excellent in heat-shielding properties, flexibility, and coating strength is obtained, which is preferable.

[0087] The heat shield layer-forming composition may contain more than 50 mass% of antimony-doped tin oxide, for example, 60 mass% or more, or 70 mass% or more, relative to 100 parts by mass of the total of the antimony-doped tin oxide and the solid content of the binder resin, and may also contain 80 mass% or more of antimony-doped tin oxide. By ensuring that the thickness is within this range, the heat-shielding film can have high heat-shielding properties, and can also exhibit high flexibility, substrate adhesion, and transparency. In one embodiment, the thermal barrier layer-forming composition may contain 99% by mass or less, for example, less than 97% by mass, for example, 95% by mass or less, of antimony-doped tin oxide relative to 100 parts by mass of the total of the antimony-doped tin oxide and the solid content of the binder resin. By keeping the thickness within this range, the heat-shielding film can have high heat-shielding properties, and can also exhibit high flexibility, substrate adhesion, and transparency. Furthermore, with the present invention, the thickness of the heat-shielding layer according to the present invention can be made 5 μm or less, which satisfies all of high heat-shielding properties, high flexibility, substrate adhesion, and transparency, and further thinning is also possible.

[0088] When an acrylate resin is used as the binder resin, it is preferable to include a polymerization initiator. The polymerization initiator is preferably a polymerization initiator that generates radicals upon irradiation with heat or active energy rays. One or more initiators may be used, and a photoradical initiator and a thermal radical initiator may be used simultaneously.

[0089] The photoinitiator is not particularly limited and can be a commonly used one. Specific examples include benzophenone, acetophenone, benzoin, benzoin methyl ether, benzoin ethyl ether, benzoin isopropyl ether, benzoin isobutyl ether, benzoin benzoic acid, benzoin methyl benzoate, benzoin dimethyl ketal, 2,4-diethylthioxanthone, 1-hydroxycyclohexyl phenyl ketone, benzyl diphenyl sulfide, tetramethylthiuram monosulfide, azobisisobutyronitrile, benzyl, dibenzyl, diacetyl, β-chloroanthraquinone, (2,4,6-trimethylbenzyldiphenyl)phosphine oxide, and 2-benzothiazole-N,N-diethyldithiocarbamate.

[0090] As the photoinitiator, α-hydroxyalkylphenone and α-aminoalkylphenone, which are considered to have particularly excellent surface curing properties, can be preferably used because they can suppress oxygen inhibition and increase coating film strength. Examples of α-hydroxyalkylphenone include 1-hydroxycyclohexylphenyl ketone, 2-hydroxy-1-{4-[4-(2-hydroxy-2-methylpropionyl)-benzyl]-phenyl}-2-methylpropan-1-one, 2-hydroxy-2-methyl-1-phenyl-propan-1-one, and 1-[4-(2-hydroxyethoxy)-phenyl]-2-hydroxy-2-methyl-1-propan-1-one. Examples of α-aminoalkylphenones include 2-benzyl-2-dimethylamino-1-(4-morpholinophenyl)-butanone-1, 2-methyl-1-(4-methylthiophenyl)-2-morpholinopropan-1-one, 2-(dimethylamino)-2-[(4-methylphenyl)methyl]-1-[4-(4-morpholyl)phenyl]-1-butanone, and the like.

[0091] When using a photoinitiator, the addition of a sensitizer can promote the absorption of active energy rays and further improve curing properties. There are no particular restrictions on the sensitizer, and common sensitizers can be used, with anthracene derivatives and naphthalene derivatives being preferred. One or more types of sensitizers may be used.

[0092] The amount of polymerization initiator added is preferably 0.1% by mass or more and 10% by mass or less, more preferably 0.5% by mass or more and 10% by mass or less, and most preferably 1% by mass or more and 7% by mass or less, relative to 100% by mass of the binder component in the heat shield layer. Amounts of 0.1% by mass or more are preferred because they do not generate an insufficient amount of radicals, which can lead to insufficient curing. Amounts of 10% by mass or less are preferred because they reduce the amount of polymerization initiator residue contained in the heat shield layer, which reduces contamination of the surface of the heat shield layer and does not adversely affect crop growth.

[0093] The amount of sensitizer added is preferably 0.1 to 5 times the mass of the photoinitiator, more preferably 0.1 to 2 times. Amounts greater than 0.1 times are preferred because a sufficient sensitizing effect can be obtained. Amounts less than 5 times are preferred because they inhibit the absorption of active energy rays by the photoinitiator, preventing a risk of insufficient radical generation.

[0094] The composition for forming a heat shield layer preferably contains a leveling agent to improve its coatability. There are no particular limitations on the leveling agent, and any common one can be used, but it is preferable to use a polyorganosiloxane, more preferably a polydimethylsiloxane, and most preferably a polydimethylsiloxane having a functional group. The use of a polydimethylsiloxane having a functional group is preferable because it improves the leveling property of the composition for forming a heat shield layer when it is applied and dried, resulting in a uniform film.

[0095] Additives such as adhesion improvers and antistatic agents may be added to the heat shield layer of the present invention as long as they do not impair the effects of the present invention.

[0096] The method for forming the heat shield layer is not particularly limited, and may be such that a heat shield layer-forming composition prepared by dissolving or dispersing antimony-doped tin oxide and a binder resin in an organic solvent is spread on one side of a film substrate by coating or the like, the solvent is removed by drying, the resulting mixture is dried by heating, and then the resulting mixture is cured by irradiation with active energy rays or heat.

[0097] When curing using a photoinitiator, the drying temperature for solvent drying is preferably 50°C or higher and 110°C or lower, and more preferably 60°C or higher and 100°C or lower. The heating time is preferably 30 seconds or shorter, more preferably 20 seconds or shorter. At 110°C or lower, the thermal load on the film is reduced, and appearance defects due to thermal shrinkage of the film are unlikely to occur. This is preferable because there is little risk of flatness defects due to sagging when used for agricultural greenhouses or window coverings. At temperatures higher than 50°C, the dilution solvent used during application is insufficiently dried, eliminating the risk of process contamination.

[0098] As the active energy rays for curing the coating film using a photoinitiator, ultraviolet rays, electron beams, X-rays, etc. can be used, but ultraviolet rays are easy to use and are preferred. The amount of ultraviolet rays to be irradiated is 30 to 500 mJ / cm in terms of cumulative light dose. 2 is preferable, and more preferably, 30 to 300 mJ / cm 2 30mJ / cm 2 A dose of 500 mJ / cm or more is preferable because the resin is cured sufficiently. 2 By setting the amount to the following, the processing speed can be improved, and the heat-shielding film can be produced economically, which is preferable.

[0099] In the present invention, the organic solvent added to the heat shield layer-forming composition is preferably a solvent with a boiling point of 90°C or higher. Adding a solvent with a boiling point of 90°C or higher prevents bumping during drying, levels the coating film, and improves the smoothness of the coating film surface after drying. The amount of solvent added is preferably about 10 to 80% by mass of the entire coating liquid.

[0100] As a method for applying the coating liquid, any known coating method can be applied, and conventionally known methods such as roll coating methods such as gravure coating and reverse coating, bar coating methods such as wire bar coating, die coating, spray coating, and air knife coating can be used.

[0101] <Physical properties of heat-shielding film> The heat-shielding property can be evaluated by the transmittance in the infrared region measured using spectral transmittance.

[0102] Spectral transmittance at 1200 nm wavelength (T 1200nm ) is preferably 20%, more preferably 15% or less, and even more preferably 10% or less, and the smaller the better. 1200nm A value of 20% or less means that infrared rays are less likely to pass through when the heat-shielding film is used, which is preferable as it provides excellent heat-shielding properties. For example, T1200nm is 0.1% or more.

[0103] Spectral transmittance of 1400nm wavelength (T 1400nm ) is preferably 20% or less, more preferably 15% or less, and even more preferably 10% or less, and the smaller the better. 1400nm It is preferable that the value is 20% or less because it has excellent heat insulation properties as described above. For example, T 1400nm is 0.1% or more.

[0104] Spectral transmittance of 1800nm ​​wavelength (T 1800nm ) is preferably 5% or less, more preferably 3% or less, and even more preferably 1% or less, and the smaller the better. 1800nm It is preferable that the value is 5% or less because it has excellent heat insulation properties as described above. For example, T 1400nm may be 0 and 0.01% or more.

[0105] Here, in the present invention, T 1200nm、 T 1400nm、 T 1800nm By satisfying this relationship, heat rays from sunlight can be more effectively blocked, and the effect of excellent heat shielding properties can be achieved.

[0106] In the present invention, T 1400nm The spectral transmittance can be measured using an ultraviolet-visible-near infrared spectrophotometer, and can be evaluated using a commercially available product such as UV-3150 manufactured by Shimadzu Corporation.

[0107] Transparency can be evaluated using the haze value. The haze value is preferably 8% or less, more preferably 5% or less, even more preferably 3% or less, and most preferably 1% or less. A haze value of 8% or less is preferable because it transmits light necessary for food growth, contributing to a stable supply of crops and improved productivity. Furthermore, when used for window coverings, it is preferable because it provides excellent visibility both indoors and outdoors. For example, the haze value is 0.01% or more, and may be 0.05% or more.

[0108] Transparency can also be evaluated by total light transmittance. The total light transmittance is preferably 50% or more, more preferably 60% or more, and even more preferably 65% ​​or more. A total light transmittance of 50% or more is preferable because it allows light of wavelengths necessary for food growth to be efficiently introduced from the outside into the indoor environment. For example, the total light transmittance may be 95% or less.

[0109] Flexibility can be evaluated by a cylindrical mandrel method. The minimum diameter of the mandrel at which cracks occur in the heat shield layer is preferably less than 4 mm, more preferably less than 3 mm, and the smaller the better. If it is less than 4 mm, there is no risk of cracks occurring in the heat shield layer when the heat shield film is used in curtain or roll form, and handling is also excellent, which is preferable. Evaluation by the mandrel method can be performed in accordance with JIS K 5600-5-1.

[0110] Curability can be evaluated using pencil hardness. The pencil hardness of the heat shielding layer is preferably H or higher, and more preferably 2H or higher. A pencil hardness of H or higher is preferable because it means that the coating film is sufficiently hardened, and the heat shielding layer can be prevented from being scraped even when used outdoors for a long period of time, resulting in excellent durability.

[0111] Scratch resistance can be evaluated by steel wool evaluation. For example, #0000 steel wool can be moved back and forth over the heat shield layer under a constant load, and the evaluation can be performed by counting the number of scratches that occur on the heat shield layer. The number of scratches is preferably 5 or less, more preferably 3 or less, and most preferably no scratches at all. The fewer scratches there are, the less likely the heat shield layer is to be scratched when used outdoors, and there is no risk of a decrease in heat shielding properties or transparency, making it more durable, which is preferable. A detailed evaluation method will be described later.

[0112] The adhesion of the heat shield layer to the substrate can be evaluated by cross-cut evaluation. For example, a grid-like pattern of cuts is made on the heat shield layer, and adhesive tape is applied to the cut surface and peeled off, and the evaluation can be based on the number of squares that come off. When quantified as substrate adhesion (%) = 100 - (number of peeled squares), the substrate adhesion rate is preferably 95% or more, more preferably 98% or more, and most preferably 100%. A substrate adhesion rate of 95% or more is preferred because there is no risk of the heat shield layer peeling off when used outdoors for long periods of time, and it has excellent durability. A detailed evaluation method will be described later. [Example]

[0113] The present invention will be described in more detail below using examples, but the present invention is not limited to these examples. The property values ​​used in the present invention were evaluated using the following methods.

[0114] (Primary particle size of antimony-doped tin oxide) The heat-shielding film was embedded in epoxy resin, and ultrathin sections were prepared using an ultramicrotome, followed by carbon deposition to prepare samples for TEM observation. The cross sections of these samples were observed using a transmission electron microscope (JEOL, JEM2100). Measurements were performed at an accelerating voltage of 200 kV and a direct magnification of 50,000. The diameters of 10 particles randomly selected from the obtained image were measured, and the average value was taken as the primary particle size.

[0115] (Base film thickness) Using a Millitron (electronic microindicator), four 5cm square samples were cut from four arbitrary points on the film to be measured, and measurements were taken at five points on each sample (total of 20 points), and the average value was taken as the thickness.

[0116] (thickness of heat shield layer) The cut-out heat-shielding film was embedded in resin and cut into ultrathin sections using an ultramicrotome. Then, using a JEOL JEM2100 transmission electron microscope at a direct magnification of 20,000 times, the film thickness of the release layer was measured from the observed TEM image.

[0117] (spectral transmittance) The transmittance at each wavelength was measured using an ultraviolet-visible-near infrared spectrophotometer (Shimadzu Corporation, UV-3150).

[0118] (Haze value) Measurement was carried out in accordance with JIS K 7136:2000 using a haze meter (manufactured by Nippon Denshoku Industries, NDH7000II).

[0119] (Total light transmittance) The haze was measured using a haze meter (NDH7000II, manufactured by Nippon Denshoku Industries Co., Ltd.) in accordance with JIS K 7361-1.

[0120] (Pencil hardness) Measurement was carried out in accordance with JIS K 5600-5-4.

[0121] (Steel wool hardness) Steel wool (Nippon Steel Wool Co., Ltd., Bonstar (registered trademark) No. 0000) weighing 200 g and measuring 700 mm 2 A steel wool evaluation jig was created by attaching the steel wool to a metal base. Using this jig, the release surface side of the heat shielding film was rubbed back and forth 10 times with a load of 200 g applied, with the steel wool in contact with the heat shielding layer side of the heat shielding film. A 2 x 2 cm area in the center of the rubbed surface was observed under reflected fluorescent light, and the number of scratches visible to the naked eye was evaluated. The number of scratches was judged according to the following criteria and evaluated as follows: ◎: Number of scratches = 0 ○: 1 scratch or less < 3 scratches △: 3 scratches or less 5 scratches or less ×: 5 < number of scratches

[0122] (Mandrel evaluation) Measurement was carried out in accordance with JIS K 5600-5-1.

[0123] (cross cut) Using a cutter guide with a gap spacing of 2 mm, 100 grid-shaped cuts are made on the surface of the heat-shielding layer, penetrating the heat-shielding layer and reaching the film substrate. Next, cellophane adhesive tape (Nichiban, No. 405; 24 mm wide) is attached to the grid-shaped cuts and rubbed with an eraser to ensure complete adhesion. The cellophane adhesive tape is then peeled vertically from the heat-shielding layer surface of the heat-shielding film, and the number of squares that have peeled off from the heat-shielding layer surface of the heat-shielding film is counted visually, and the adhesion between the heat-shielding layer and the film substrate is calculated using the following formula. Note that even squares that are partially peeled off are counted as peeled squares. Adhesion to substrate (%) = 100 - (number of peeled squares) The substrate adhesion (%) was evaluated according to the following criteria. ◎: 100% 〇: 98% or more, less than 100% △: 95% or more, less than 98% ×: Less than 95%

[0124] (Method for measuring number average molecular weight of polycarbonate polyol) When urethane resins with polycarbonate structures are measured by proton nuclear magnetic resonance spectroscopy (H-NMR), a peak derived from the methylene group adjacent to the OCOO bond is observed at around 4.1 ppm. Additionally, a peak derived from the methylene group adjacent to the urethane bond formed by the reaction of polyisocyanate with polycarbonate polyol is observed approximately 0.2 ppm higher than this peak. The number-average molecular weight of the polycarbonate polyol was calculated from the integral values ​​of these two peaks and the molecular weight of the monomers that make up the polycarbonate polyol.

[0125] (Polymerization of urethane resin A-1 having a polycarbonate structure) 27.5 parts by mass of hydrogenated m-xylylene diisocyanate, 6.5 parts by mass of dimethylolpropanoic acid, 60 parts by mass of polyhexamethylene carbonate diol with a number average molecular weight of 1800, 6 parts by mass of neopentyl glycol, and 84.00 parts by mass of acetone as a solvent were added to a four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer. The mixture was stirred under a nitrogen atmosphere at 75°C for 3 hours, and it was confirmed that the reaction solution had reached the specified amine equivalent. Next, 5 parts by mass of trimethylolpropane was added, and the mixture was stirred under a nitrogen atmosphere at 75°C for 1 hour, and it was confirmed that the reaction solution had reached the specified amine equivalent. After cooling the reaction solution to 40°C, 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisper capable of high-speed stirring, and the temperature was adjusted to 25°C. The mixture was stirred for 2000 min. -1 The polyurethane prepolymer solution was added and dispersed in water while stirring and mixing at 50°C. Then, the acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (A-1) with a solids content of 34% by mass.

[0126] (Polymerization of urethane resin A-2 having a polycarbonate structure) A four-neck flask equipped with a stirrer, Dimroth condenser, nitrogen inlet tube, silica gel drying tube, and thermometer was charged with 25 parts by weight of 4,4-dicyclohexylmethane diisocyanate, 5 parts by weight of dimethylolpropanoic acid, 52 parts by weight of polyhexamethylene carbonate diol with a number average molecular weight of 2600, 6 parts by weight of neopentyl glycol, and 84.00 parts by weight of acetone as a solvent. The mixture was stirred under a nitrogen atmosphere at 75°C for 3 hours, and the reaction mixture was confirmed to have reached the required amine equivalent. Next, 18 parts by weight of a polyisocyanate compound having an isocyanurate structure (Asahi Kasei Chemicals, Duranate TPA, trifunctional) made from hexamethylene diisocyanate was added, and the mixture was stirred under a nitrogen atmosphere at 75°C for 1 hour, and the reaction mixture was confirmed to have reached the required amine equivalent. The reaction mixture temperature was then lowered to 50°C, and 8 parts by weight of methyl ethyl ketoxime was added dropwise. After cooling this reaction solution to 40°C, 5.17 parts by mass of triethylamine was added to obtain a polyurethane prepolymer solution. Next, 450 g of water was added to a reaction vessel equipped with a homodisperser capable of high-speed stirring, and the temperature was adjusted to 25°C. While stirring and mixing at 2000 min-1, the polyurethane prepolymer solution was added and dispersed in water. Then, acetone and a portion of the water were removed under reduced pressure to prepare a water-dispersible urethane resin solution (A-2) with a solids content of 35% by mass.

[0127] (Polymerization of blocked isocyanate crosslinking agent B-1) A flask equipped with a stirrer, thermometer, and reflux condenser was charged with 66.04 parts by weight of a polyisocyanate compound (Duranate TPA, manufactured by Asahi Kasei Chemicals) having an isocyanurate structure derived from hexamethylene diisocyanate, 17.50 parts by weight of N-methylpyrrolidone, and 95 parts by weight of 3,5-dimethylpyrazole (dissociation temperature: 120°C, boiling point: 218°C). The mixture was then maintained at 70°C for 1 hour under a nitrogen atmosphere. Subsequently, 30 parts by weight of dimethylolpropanoic acid was added dropwise. After measuring the infrared spectrum of the reaction solution and confirming that the absorption of the isocyanate groups had disappeared, 5.59 parts by weight of N,N-dimethylethanolamine and 132.5 parts by weight of water were added to obtain a blocked polyisocyanate aqueous dispersion (B-1) with a solids content of 40% by weight. The blocked isocyanate crosslinker had a functionality of 4 and an NCO equivalent of 280.

[0128] (Polymerization of blocked isocyanate crosslinking agent B-2) A flask equipped with a stirrer, thermometer, and reflux condenser was charged with 100 parts by weight of a polyisocyanate compound (Duranate TPA, manufactured by Asahi Kasei Chemicals) having an isocyanurate structure derived from hexamethylene diisocyanate, 55 parts by weight of propylene glycol monomethyl ether acetate, and 30 parts by weight of polyethylene glycol monomethyl ether (average molecular weight 750). The mixture was then maintained at 70°C for 4 hours under a nitrogen atmosphere. The reaction mixture was then cooled to 50°C, and 47 parts by weight of methyl ethyl ketoxime was added dropwise. The infrared spectrum of the reaction mixture was measured to confirm that the absorption of the isocyanate group had disappeared. Then, 210 parts by weight of water was added to obtain an oxime-blocked isocyanate crosslinking agent (B-2) with a solids content of 40% by weight. The blocked isocyanate crosslinking agent had 3 functional groups and an NCO equivalent of 170.

[0129] (Polyester Resin Polymerization C-1) A stainless steel autoclave equipped with a stirrer, thermometer, and partial reflux condenser was charged with 194.2 parts by mass of dimethyl terephthalate, 184.5 parts by mass of dimethyl isophthalate, 14.8 parts by mass of dimethyl-5-sodium sulfoisophthalate, 233.5 parts by mass of diethylene glycol, 136.6 parts by mass of ethylene glycol, and 0.2 parts by mass of tetra-n-butyl titanate, and the transesterification reaction was carried out at a temperature of 160 to 220°C for 4 hours. The temperature was then raised to 255°C, and the reaction system was gradually reduced in pressure. The reaction was then continued for 1 hour and 30 minutes under a reduced pressure of 30 Pa to obtain copolymer polyester resin (C-1). The resulting copolymer polyester resin (C-1) was pale yellow and transparent. The reduced viscosity of copolymer polyester resin (C-1) was measured and found to be 0.70 dL / g. The glass transition temperature measured by DSC was 40°C.

[0130] (Preparation of Polyester Water Dispersion Cw-1) A reactor equipped with a stirrer, thermometer, and reflux device was charged with 15 parts by mass of polyester resin (C-1) and 15 parts by mass of ethylene glycol n-butyl ether, and the mixture was heated to 110°C and stirred to dissolve the resin. After the resin was completely dissolved, 70 parts by mass of water was gradually added to the polyester solution while stirring. After the addition, the liquid was cooled to room temperature while stirring to produce a milky white polyester water dispersion (Cw-1) with a solids content of 15% by mass.

[0131] (Production of polyester film X1) As the raw polymer for the film, PET resin pellets with an intrinsic viscosity of 0.62 dl / g (solvent: phenol / tetrachloroethane = 60 / 40) and substantially no particles were dried at 135°C for 6 hours under a reduced pressure of 133 Pa. Then, the pellets were fed into an extruder and melt-extruded into a sheet at approximately 280°C, which was then rapidly cooled and solidified on a rotating cooled metal roll maintained at a surface temperature of 20°C to obtain an unstretched PET sheet.

[0132] This unstretched PET sheet was heated to 100° C. using a group of heated rolls and an infrared heater, and then stretched 3.5 times in the longitudinal direction using a group of rolls with different peripheral speeds to obtain a uniaxially stretched PET film.

[0133] Next, the following adhesive layer-forming coating solution was left to stand at room temperature for 5 hours or more, and then applied to one side of the PET film by roll coating, followed by drying at 80°C for 20 seconds. The final coating amount after drying (after biaxial stretching) was 0.15 g / m 2 The film was then stretched 4.0 times in the width direction at 120°C using a tenter, and while the length of the film in the width direction was fixed, it was heated at 230°C for 5 seconds and further subjected to a 3% width direction relaxation treatment at 100°C for 10 seconds to obtain a 100 μm polyester film X1. (Preparation of coating solution for forming easy-adhesion layer) The following coating agent was mixed with a mixed solvent of water and isopropanol to prepare a coating solution with a solids mass ratio of urethane resin solution (A-2) / crosslinking agent (B-1) / polyester water dispersion (Cw-1) of 22 / 10 / 68. Urethane resin solution (A-2) 2.71 parts by mass Crosslinking agent (B-1) 1.00 parts by mass Polyester water dispersion (Cw-1) 19.05 parts by mass Particles 0.47 parts by mass (Dry process silica with an average particle size of 200 nm, solid content of 3.5% by mass) Particles 1.85 parts by mass (Silica sol with an average particle size of 40 to 50 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content 10% by mass)

[0134] (Production of polyester film X2) A polyester film X2 was obtained in the same manner as in the production of the polyester film X1, except that the urethane resin was changed to (A-1).

[0135] (Production of polyester film X3) A polyester film X3 was obtained in the same manner as in the polyester film X1, except that the crosslinking agent was changed to (B-2).

[0136] (Production of polyester film X4) Polyester film X4 was obtained in the same manner as polyester film X1, except that the following coating agent was mixed into a mixed solvent of water and isopropanol, and the solid mass ratio of urethane resin solution (A-1) / crosslinking agent (B-1) / polyester water dispersion (Cw-1) was changed to 25 / 26 / 49. Urethane resin solution (A-1) 3.55 parts by mass Crosslinking agent (B-1) 3.16 parts by mass Polyester water dispersion (Cw-1) 16.05 parts by mass Particles 0.47 parts by mass (Dry process silica with an average particle size of 200 nm, solid content of 3.5% by mass) Particles 1.85 parts by mass (Silica sol with an average particle size of 40 to 50 nm, solid content concentration of 30% by mass) Surfactant 0.30 parts by mass (Silicone-based, solid content 10% by mass)

[0137] Example 1 The following composition for forming a heat shield layer was applied to the adhesive layer side of polyester film X1 using reverse gravure so that the thickness of the heat shield layer after drying would be 2.7 μm, and the coating film after drying was dried at 90° C. for 15 seconds. 2 A heat-shielding film was obtained by irradiating the film with ultraviolet light (Heraeus LightHammer MARKII, H bulb). The resulting heat-shielding film was evaluated for flexibility, heat-shielding properties, curing properties, abrasion resistance, transparency, and substrate adhesion, and good evaluation results were obtained. Methyl ethyl ketone 59.70 parts by mass Propylene glycol monomethyl ether 14.93 parts by mass Antimony-doped tin oxide (primary particle size 8 nm) 22.50 parts by mass Binder resin: dipentaerythritol hexaacrylate 2.50 parts by mass (Product name: A-DPH, Shin-Nakamura Chemical, hexafunctional acrylate compound) Polymerization initiator: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one 0.13 parts by mass (Product name: Omnirad907, manufactured by IGM Resins) Leveling agent 0.24 parts by mass (Product name: BYK-3510, manufactured by BYK Japan)

[0138] Example 2 A heat shielding film was obtained in the same manner as in Example 1, except that the composition for forming the heat shielding layer was changed to the following. Methyl ethyl ketone 59.75 parts by mass Propylene glycol monomethyl ether 14.94 parts by mass Antimony-doped tin oxide (primary particle size 8 nm) 23.75 parts by mass Binder resin: dipentaerythritol hexaacrylate 1.25 parts by mass (Product name: A-DPH, Shin-Nakamura Chemical, hexafunctional acrylate compound) Polymerization initiator: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one 0.06 parts by mass (Product name: Omnirad907, manufactured by IGM Resins) Leveling agent 0.25 parts by mass (Product name: BYK-3510, manufactured by BYK Japan)

[0139] Example 3 A heat shielding film was obtained in the same manner as in Example 1, except that the composition for forming the heat shielding layer was changed to the following. Methyl ethyl ketone 59.77 parts by mass Propylene glycol monomethyl ether 14.94 parts by mass Antimony-doped tin oxide (primary particle size 8 nm) 24.25 parts by mass Binder resin: dipentaerythritol hexaacrylate 0.75 parts by mass (Product name: A-DPH, Shin-Nakamura Chemical, hexafunctional acrylate compound) Polymerization initiator: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one 0.04 parts by mass (Product name: Omnirad907, manufactured by IGM Resins) Leveling agent 0.25 parts by mass (Product name: BYK-3510, manufactured by BYK Japan)

[0140] Example 4 A heat shielding film was obtained in the same manner as in Example 1, except that the composition for forming the heat shielding layer was changed to the following. Methyl ethyl ketone 59.60 parts by mass Propylene glycol monomethyl ether 14.90 parts by mass Antimony-doped tin oxide (primary particle size 8 nm) 20.00 parts by mass Binder resin: 10-functional urethane acrylate compound 5.00 parts by mass (Product name: UV-1700B, manufactured by Mitsubishi Chemical Corporation) Polymerization initiator: 2-methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one 0.25 parts by mass (Product name: Omnirad907, manufactured by IGM Resins) Leveling agent 0.25 parts by mass (Product name: BYK-3510, manufactured by BYK Japan)

[0141] Example 5 A heat-shielding film was obtained in the same manner as in Example 1, except that the binder resin was changed to a 10-functional urethane acrylate compound (product name: UV-1700B, manufactured by Mitsubishi Chemical Corporation).

[0142] Example 6 A heat-shielding film was obtained in the same manner as in Example 1, except that the binder resin was changed to a 15-functional urethane acrylate compound (product name: 8UX-015A, manufactured by Taisei Fine Chemical Co., Ltd.).

[0143] Example 7 A heat-shielding film was obtained in the same manner as in Example 1, except that the binder resin was changed to a tetrafunctional acrylate compound (product name: A-TMMT, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0144] Example 8 A heat-shielding film was obtained in the same manner as in Example 1, except that the binder resin was changed to a trifunctional acrylate compound (product name: A-TMM-3, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0145] Example 9 A heat-shielding film was obtained in the same manner as in Example 1, except that the binder resin was changed to a bifunctional acrylate compound (product name: A-701A, manufactured by Shin-Nakamura Chemical Co., Ltd.).

[0146] Example 10 A heat shielding film was obtained in the same manner as in Example 1, except that the coating was carried out so that the heat shielding layer had a thickness of 3.8 μm.

[0147] Example 11 A heat shielding film was obtained in the same manner as in Example 1, except that the coating was carried out so that the heat shielding layer had a thickness of 4.9 μm.

[0148] Example 12 A heat shielding film was obtained in the same manner as in Example 1, except that the coating was carried out so that the heat shielding layer had a thickness of 1.3 μm.

[0149] Example 13 A heat shielding film was obtained in the same manner as in Example 1, except that the primary particle size of the antimony-doped tin oxide was changed to 10 nm.

[0150] Example 14 A heat shielding film was obtained in the same manner as in Example 1, except that the primary particle size of the antimony-doped tin oxide was changed to 20 nm.

[0151] Example 15 A heat shielding film was obtained in the same manner as in Example 1, except that the polyester film was changed to Polyester film X2.

[0152] Example 16 A heat-shielding film was obtained in the same manner as in Example 1, except that the polyester film was changed to Polyester film X3.

[0153] Example 17 A heat shielding film was obtained in the same manner as in Example 1, except that the polyester film was changed to Polyester film X4.

[0154] (Comparative Example 1) A heat shielding film was obtained in the same manner as in Example 1, except that the composition for forming the heat shielding layer was changed to the following. Methyl ethyl ketone 59.80 parts by mass Propylene glycol monomethyl ether 14.95 parts by mass Antimony-doped tin oxide (primary particle size 8 nm) 25.00 parts by mass Leveling agent 0.25 parts by mass (Product name: BYK-3510, manufactured by BYK Japan) Since the heat-shielding film did not contain a binder resin in the composition for forming a heat-shielding layer, a uniform coating film was not formed, resulting in a high haze value. Furthermore, the coating film strength was insufficient, resulting in poor pencil hardness and steel wool hardness. Furthermore, the adhesion to the polyester film X1 was poor, and the durability was insufficient for long-term outdoor use.

[0155] (Comparative Example 2) A heat-shielding film was obtained in the same manner as in Example 1, except that the primary particle size of the antimony-doped tin oxide was changed to 50 nm. Because the primary particle size of the antimony-doped tin oxide in this heat-shielding film was 50 nm or more, the heat-shielding property was insufficient and the haze value was high. Furthermore, because the crosslinking reaction of the binder resin did not proceed easily, the curability and abrasion resistance were insufficient, and the durability was insufficient for long-term outdoor use.

[0156] [Table 1A]

[0157] [Table 1B]

[0158] [Table 2]

[0159] As is clear from the results of the examples, the heat-shielding film of the present invention has high heat-shielding properties. Furthermore, the heat-shielding film of the present invention has high transparency (light transmittance) while also having high heat-shielding properties. Therefore, it can be suitably used for agricultural purposes and as a building material for automobile window coverings, residential window coverings, etc. Furthermore, it does not adversely affect the growth of horticultural crops, and when used for window coverings, it can let in outside light without blocking it. Furthermore, the heat-shielding film of the present invention has excellent abrasion resistance and coating strength, and therefore can be used for a long period of time without any deterioration in performance. Furthermore, the heat-shielding film of the present invention has excellent flexibility and therefore excellent handleability, and can suppress film cracking in the heat-shielding layer even when used in a shape such as a curtain or roll. Moreover, even when used in such a shape, the film can have high heat-shielding properties and transparency (light transmittance). Furthermore, the heat-shielding film of the present invention also has excellent abrasion resistance. [Industrial Applicability]

[0160] The heat-shielding film of the present invention has high heat-shielding properties and high transparency, so it does not adversely affect the growth of horticultural crops and can let in outside light without blocking it when used for window coverings. Furthermore, it has excellent abrasion resistance and coating strength, so it can be used suitably for long periods of time without its performance decreasing. In addition, it has excellent flexibility, so it is easy to handle, and can be used suitably in the form of a curtain or roll without causing problems such as film cracking in the heat-shielding layer.

Claims

1. A heat-shielding film having a base film and a heat-shielding layer, an easy-adhesion layer between the base film and the heat-shielding layer, the thermal barrier layer is formed from a thermal barrier layer-forming composition containing antimony-doped tin oxide and a binder resin, the antimony-doped tin oxide contained in the thermal barrier layer has an average primary particle size of less than 50 nm, and the minimum diameter of a mandrel at which cracks occur in the thermal barrier layer by a cylindrical mandrel method is less than 4 mm, The heat-shielding film has a spectral transmittance T1400nm at a wavelength of 1400 nm of 20% or less and a haze value of 8% or less.

2. the base film is a polyester film that does not substantially contain particles, and the easy-adhesion layer is formed by curing a composition that contains a urethane resin having a polycarbonate structure and a branched structure, a crosslinking agent, and a polyester resin; The heat-shielding film according to claim 1 .

3. 3. The heat-shielding film according to claim 1, wherein the heat-shielding layer has a pencil hardness of H or more.

4. When the relationship between the thickness n of the thermal barrier layer and the thermal barrier property is expressed by the following (Equation 1), The heat-shielding film according to any one of claims 1 to 3, wherein the value represented by (Formula 1) is 20 or more: (100-T1400nm) / n (Formula 1) In formula 1, the film thickness n is 0.5 μm or more and 5 μm or less.

5. The heat-shielding film according to any one of claims 1 to 4, which has a total light transmittance of 50% or more.

6. 6. The heat shielding film according to claim 1, wherein the content of the antimony-doped tin oxide and the binder resin in the heat shielding layer-forming composition is, in terms of weight ratio, antimony-doped tin oxide:binder resin=70:30 to 99:

1.

7. The heat-shielding film according to any one of claims 1 to 6, wherein the binder resin comprises at least one resin selected from the group consisting of acrylate resins, acrylic resins, polyester resins, and polyurethane resins.

8. A heat-shielding film for agricultural use, comprising the heat-shielding film according to any one of claims 1 to 7.

9. A heat-shielding film for window lining, comprising the heat-shielding film according to any one of claims 1 to 7.

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