Thermochromic resin composite material and laminate using the same

Abstract

To provide a thermochromic resin composite material in which the absorption rate of visible light is high at temperatures below 30°C and low at temperatures of at least 60°C. [Solution] A resin composition containing 20-95% by mass of an acrylic polymer with a refractive index of 1.46-1.56 at 23°C, 4-75% by mass of polyvinylidene fluoride with a refractive index of 1.36-1.46 at 23°C, and 1-40% by mass of polyalkyl acrylate with a refractive index of 1.41-1.51 at 23°C, and For every 100 parts by mass of the resin composition, add 0.0005 to 0.03 parts by mass of at least one black colorant selected from the group consisting of black pigments and black dyes. A thermochromic resin composite material characterized by containing the following:

Description

Technical Field

[0001] The present invention relates to a thermochromic resin composite material and a laminate using the same.

Background Art

[0002] In recent years, thermochromic materials that change color or transparency according to temperature changes have attracted attention. For example, Japanese Patent Application Laid-Open No. 2024-8219 (Patent Document 1) discloses a resin composition of 100 parts by mass containing 15 to 84% by mass of an acrylic polymer, 15 to 84% by mass of polyvinylidene fluoride, and 1 to 40% by mass of polycaprolactone, and at least 0.0005 to 0.03 parts by mass of at least one black coloring agent selected from the group consisting of a black pigment and a black dye. This thermochromic resin composite material has a low visible light absorption rate at a high temperature of 70°C or higher and a high visible light absorption rate at a low temperature of 40°C or lower. Further, a laminate having a metal film provided on one side of a member made of such a thermochromic resin composite material has a high visible light reflectance at a high temperature of 70°C or higher and a low visible light reflectance at a low temperature of 40°C or lower.

[0003] However, the thermochromic resin composite material described in Patent Document 1 has a high light absorption rate at a temperature of 60°C, and since the temperature at which the light absorption rate and the light reflectance of the laminate provided with a metal film on one side change are relatively high, it is not always sufficient as a thermal control material in which the light absorption rate and the light reflectance of the laminate change at a temperature near the human body temperature (36°C). For this reason, there is a demand for a thermochromic resin composite material in which the light absorption rate changes at a lower temperature and a laminate in which the light reflectance changes.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] The present invention has been made in view of the problems of the above-mentioned prior art, and aims to provide a thermochromic resin composite material in which the absorption rate of visible light is high at temperatures of 30°C or below and the absorption rate of visible light is low at temperatures of at least 60°C, and a laminate in which a highly reflective layer such as a metal film is provided on one side of a member made of a thermochromic resin composite material, wherein the reflectivity of visible light is low at temperatures of 30°C or below and the reflectivity of visible light is high at temperatures of at least 60°C. [Means for solving the problem]

[0006] As a result of diligent research to achieve the above objective, the present inventors have discovered that in a resin composite material obtained by blending a black colorant with a resin composition containing acrylic polymer, polyvinylidene fluoride, and polyalkyl acrylate in specific proportions, the absorption rate of visible light increases at temperatures below 30°C and decreases at temperatures below at least 60°C. Furthermore, they have discovered that in a laminate in which a highly reflective layer such as a metal film is provided on one side of a component made of this resin composite material, the reflectivity of visible light decreases at temperatures below 30°C and increases at temperatures below at least 60°C, thus completing the present invention.

[0007] In other words, the present invention provides the following embodiments. [1] A resin composition containing 20 to 95% by mass of an acrylic polymer having a refractive index of 1.46 to 1.56 at 23°C, 4 to 75% by mass of polyvinylidene fluoride having a refractive index of 1.36 to 1.46 at 23°C, and 1 to 40% by mass of polyalkyl acrylate having a refractive index of 1.41 to 1.51 at 23°C, and For every 100 parts by mass of the resin composition, add 0.0005 to 0.03 parts by mass of at least one black colorant selected from the group consisting of black pigments and black dyes. A thermochromic resin composite material containing [the specified substance]. [2] The thermochromic resin composite material according to [1], further containing 1 to 100 parts by mass of a glass-based filler with a silicon dioxide purity of 90% or more per 100 parts by mass of the resin composition. A laminate comprising a member made of the thermochromic resin composite material described in [3] [1] or [2], and a highly reflective layer with a visible light reflectivity of 70% or more disposed on at least a portion of one side of the member.

[0008] The reasons why the thermochromic resin composite material of the present invention exhibits a high absorption rate of visible light at temperatures below 30°C and a low absorption rate of visible light at temperatures below at least 60°C, and why the laminate of the present invention exhibits a low reflectivity of visible light at temperatures below 30°C and a high reflectivity of visible light at temperatures below at least 60°C, are not entirely clear, but the inventors speculate as follows.

[0009] In other words, polyalkyl acrylate forms a crystalline phase when exposed to temperatures below its melting point. Therefore, when the thermochromic resin composite material of the present invention is exposed to temperatures below the melting point of polyalkyl acrylate, a sea-island structure is formed having a sea phase consisting of a polymer blend of acrylic polymer and polyvinylidene fluoride and island phases consisting of at least partially crystallized polyalkyl acrylate. When visible light is irradiated onto such a thermochromic resin composite material having a sea-island structure at temperatures below the melting point of polyalkyl acrylate, the incident visible light is scattered by the island phase, and the optical path length when propagating through the thermochromic resin composite material becomes longer, making it easier to absorb by the black colorant contained in trace amounts in the thermochromic resin composite material. As a result, it is presumed that the absorption rate of visible light is high at temperatures below the melting point of polyalkyl acrylate. Furthermore, when visible light is irradiated onto the laminate of the present invention at a low temperature below the melting point of polyalkyl acrylate, it is presumed that the visible light is absorbed by the component made of the thermochromic resin composite material of the present invention, and the reflection of visible light by the highly reflective layer is reduced, resulting in a lower reflectivity of visible light.

[0010] On the other hand, since polyalkyl acrylate has a melting point of 10 to 60°C, the crystals completely melt at a temperature of at least 60°C. Therefore, when the thermochromic resin composite material of the present invention is exposed to a temperature of at least 60°C, a sea-island structure is formed having a sea phase consisting of a polymer blend containing acrylic polymer and polyvinylidene fluoride in predetermined proportions and an island phase consisting of molten polyalkyl acrylate. When visible light is irradiated onto such a thermochromic resin composite material having a sea-island structure at a temperature of at least 60°C, the refractive index of the molten polyalkyl acrylate matches that of the polymer blend containing acrylic polymer and polyvinylidene fluoride in predetermined proportions. As a result, scattering of incident visible light is suppressed, and the optical path length when propagating within the thermochromic resin composite material is shortened, making it less likely for visible light to be absorbed by the black colorant contained in the thermochromic resin composite material. Consequently, it is presumed that the absorption rate of visible light is low at a temperature of at least 60°C. Furthermore, when visible light is irradiated onto the laminate of the present invention at a temperature of at least 60°C, it is presumed that the visible light reflectivity will be high because the visible light is less absorbed in the component made of the thermochromic resin composite material of the present invention, and more visible light is reflected by the highly reflective layer. [Effects of the Invention]

[0011] According to the present invention, it is possible to obtain a thermochromic resin composite material in which the absorption rate of visible light is high at temperatures of 30°C or below, and the absorption rate of visible light is low at temperatures of at least 60°C. Furthermore, by providing a highly reflective layer, such as a metal film, on one side of a component made of such a thermochromic resin composite material, it is possible to obtain a laminate in which the reflectivity of visible light is low at temperatures of 30°C or below, and the reflectivity of visible light is high at temperatures of at least 60°C. [Modes for carrying out the invention]

[0012] The present invention will be described in detail below with reference to its preferred embodiments.

[0013] [Thermochromic resin composite material] First, the thermochromic resin composite material of the present invention will be described. The thermochromic resin composite material of the present invention comprises a resin composition containing 20 to 95% by mass of an acrylic polymer with a refractive index of 1.46 to 1.56 at 23°C, 4 to 75% by mass of polyvinylidene fluoride with a refractive index of 1.36 to 1.46 at 23°C, and 1 to 40% by mass of polyalkyl acrylate with a refractive index of 1.41 to 1.51 at 23°C, and 0.0005 to 0.03 parts by mass of at least one black colorant selected from the group consisting of black pigments and black dyes per 100 parts by mass of the resin composition. Furthermore, in the thermochromic resin composite material of the present invention, it is preferable that 1 to 100 parts by mass of a glass-based filler is further included per 100 parts by mass of the resin composition.

[0014] (Acrylic polymer) The acrylic polymer used in the present invention is an acrylic polymer having a refractive index of 1.46 to 1.56 at 23°C, and includes homopolymers and copolymers of acrylic monomers. The proportion of acrylic monomer units in the copolymer of acrylic monomers is preferably 50 mol% or more, more preferably 70 mol% or more, even more preferably 80 mol% or more, and particularly preferably 90 mol% or more. Among such acrylic polymers, homopolymers of acrylic monomers are preferred from the viewpoint of having excellent heat resistance and transparency, and furthermore, at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material is low and the visible light reflectance of the resulting laminate is high.

[0015] Examples of the acrylic monomers include alkyl methacrylates (e.g., methyl methacrylate, ethyl methacrylate, etc.), alkyl acrylates (e.g., methyl acrylate, ethyl acrylate, etc.), methacrylic acid, and acrylic acid. The number of carbon atoms in the alkyl group of the alkyl methacrylate and alkyl acrylate is preferably 11 or less, more preferably 8 or less, and even more preferably 5 or less, from the viewpoint of ensuring that the refractive index of the acrylic polymer at 23°C is within a predetermined range. Among these acrylic monomers, alkyl methacrylates are preferred, and methyl methacrylate is more preferred, from the viewpoint of excellent heat resistance and moldability.

[0016] Other copolymer monomers used in acrylic monomer copolymers include, for example, olefins (e.g., ethylene, propylene, etc.) and aromatic vinyl monomers (e.g., styrene, α-methylstyrene, etc.). These other copolymer monomers may be used individually or in combination of two or more.

[0017] Specific examples of acrylic polymers used in the present invention include polyalkyl methacrylate (e.g., polymethyl methacrylate, polyethyl methacrylate, etc.), polyalkyl acrylate (e.g., polymethyl acrylate, polyethyl acrylate, etc.), acrylic acid-alkyl methacrylate copolymer (e.g., acrylic acid-methyl methacrylate copolymer, etc.), alkyl methacrylate-alkyl acrylate copolymer (e.g., methyl methacrylate-ethyl acrylate copolymer, etc.), ethylene-alkyl methacrylate (e.g., ethylene-methyl methacrylate copolymer, etc.), ethylene-alkyl acrylate (e.g., ethylene-ethyl acrylate copolymer, etc.), styrene-alkyl methacrylate (e.g., styrene-methyl methacrylate copolymer, etc.), and styrene-alkyl acrylate (e.g., styrene-ethyl acrylate copolymer, etc.). From the viewpoint of ensuring that the refractive index of the acrylic polymer at 23°C is within a predetermined range, the number of carbon atoms in the alkyl group of these acrylic polymers is preferably 11 or less, more preferably 8 or less, and even more preferably 5 or less. Among these acrylic polymers, polyalkyl methacrylate is preferred, and polymethyl methacrylate is more preferred, from the viewpoint of excellent heat resistance and compatibility with polyvinylidene fluoride.

[0018] Furthermore, in the acrylic polymer used in the present invention, the refractive index at 23°C is 1.46 to 1.56, more preferably 1.46 to 1.54, and even more preferably 1.47 to 1.51. If the refractive index of the acrylic polymer is below the lower limit or above the upper limit, the refractive index difference with the polyalkyl acrylate becomes large, and at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material tends to increase, and the visible light reflectance of the resulting laminate tends to decrease.

[0019] (Polyvinylidene fluoride) The polyvinylidene fluoride used in the present invention is a polyvinylidene fluoride having a refractive index at 23°C of 1.36 to 1.46, and examples thereof include homopolymers and copolymers of vinylidene fluoride. As the proportion of vinylidene fluoride units in the copolymer of vinylidene fluoride, 50 mol% or more is preferable, 70 mol% or more is more preferable, 80 mol% or more is still more preferable, and 90 mol% or more is particularly preferable. Among such polyvinylidene fluorides, a homopolymer of vinylidene fluoride is preferable from the viewpoint of excellent compatibility with the acrylic polymer (particularly, polymethyl methacrylate).

[0020] Examples of other copolymer monomers in the copolymer of vinylidene fluoride include fluoroolefins (for example, trifluoroethylene, hexafluoropropylene, etc.), aromatic vinyls (for example, styrene, α-methylstyrene, p-fluorostyrene, α-fluorostyrene, etc.). These other copolymer monomers may be used alone or in combination of two or more.

[0021] In addition, for the polyvinylidene fluoride used in the present invention, the refractive index at 23°C is 1.36 to 1.46, more preferably 1.37 to 1.46, and still more preferably 1.40 to 1.44. When the refractive index of the polyvinylidene fluoride is less than the lower limit or exceeds the upper limit, the refractive index difference from the polyalkyl acrylate becomes large, and at a temperature of at least 60°C, the visible light absorption rate of the obtained resin composite material tends to increase, and the visible light reflectance of the obtained laminate tends to decrease.

[0022] (Polyalkyl acrylate) The polyalkyl acrylate used in the present invention is a polyalkyl acrylate having a refractive index of 1.41 to 1.51 at 23°C, and examples thereof include homopolymers and copolymers of alkyl acrylate monomers. As the proportion of the alkyl acrylate monomer unit in the copolymer of the alkyl acrylate monomer, 50 mol% or more is preferable, 70 mol% or more is more preferable, 80 mol% or more is still more preferable, and 90 mol% or more is particularly preferable. Among such polyalkyl acrylates, from the viewpoint of increasing the degree of temperature change of the visible light absorption rate of the obtained resin composite material and the degree of temperature change of the visible light reflectance of the obtained laminate, the homopolymer of the alkyl acrylate monomer is preferable.

[0023] In such a polyalkyl acrylate, by changing the number of carbon atoms of the alkyl group within the above range, the melting point can be adjusted, and a resin composite material in which the visible light absorption rate changes and a laminate in which the visible light reflectance changes can be obtained at a desired temperature. The number of carbon atoms of the alkyl group can be appropriately set according to the desired temperature for changing the visible light absorption rate of the obtained resin composite material and the visible light reflectance of the obtained laminate, but 12 to 22 is preferable, 12 to 20 is more preferable, 13 to 18 is still more preferable, and 14 to 16 is particularly preferable. By setting the number of carbon atoms of the alkyl group within the above range, the melting point of the polyalkyl acrylate can be adjusted to preferably within the range of 10 to 60°C (more preferably 10 to 55°C, still more preferably 15 to 50°C, particularly preferably 20 to 40°C), and at a temperature within the above range, it is possible to obtain a resin composite material in which the visible light absorption rate changes and a laminate in which the visible light reflectance changes.

[0024] Specific examples of the alkyl acrylate monomers include acrylates having an alkyl group with 12 to 22 carbon atoms, such as dodecyl acrylate, tridecyl acrylate, tetradecyl acrylate, pentadecyl acrylate, hexadecyl acrylate, heptadecyl acrylate, octadecyl acrylate, nonadecyl acrylate, eicosyl acrylate, hene-eicosyl acrylate, and docosyl acrylate; and methacrylates having an alkyl group with 12 to 22 carbon atoms, such as dodecyl methacrylate, tridecyl methacrylate, tetradecyl methacrylate, pentadecyl methacrylate, hexadecyl methacrylate, heptadecyl methacrylate, octadecyl methacrylate, nonadecyl methacrylate, eicosyl methacrylate, hene-eicosyl methacrylate, and docosyl methacrylate. These alkyl acrylate monomers may be used individually or in combination of two or more.

[0025] Other copolymer monomers used in copolymers of alkyl acrylate monomers include, for example, olefins (e.g., ethylene, propylene, etc.) and aromatic vinyl monomers (e.g., styrene, α-methylstyrene, etc.). These other copolymer monomers may be used individually or in combination of two or more.

[0026] Specifically, the polyalkyl acrylates used in the present invention include polyalkyl acrylates (e.g., polydodecyl acrylate, polytetradecyl acrylate, polyhexadecyl acrylate, polyoctadecyl acrylate, etc.) and copolymers thereof, polyalkyl methacrylates (e.g., polydodecyl methacrylate, polytetradecyl methacrylate, polyhexadecyl methacrylate, polyoctadecyl methacrylate, etc.) and copolymers thereof, and methacrylate-alkyl acrylate copolymers (e.g., methacrylate). Acrylic acid / dodecyl acrylate copolymer, methacrylic acid / tetradecyl acrylate copolymer, methacrylic acid / hexadecyl acrylate copolymer, methacrylic acid / octadecyl acrylate copolymer, etc., alkyl methacrylate / alkyl acrylate copolymer (for example, dodecyl methacrylate / tetradecyl acrylate copolymer, hexadecyl methacrylate / octadecyl acrylate copolymer, tetradecyl methacrylate / dodecyl acrylate copolymer, octadecyl methacrylate / hexadecyl acrylate Examples include ethylene alkyl acrylate copolymers (e.g., ethylene dodecyl acrylate copolymer, ethylene tetradecyl acrylate copolymer, ethylene hexadecyl acrylate copolymer, ethylene octadecyl acrylate copolymer, etc.), ethylene alkyl methacrylate copolymers (e.g., ethylene dodecyl methacrylate copolymer, ethylene tetradecyl methacrylate copolymer, ethylene hexadecyl methacrylate copolymer, ethylene octadecyl methacrylate copolymer, etc.), styrene alkyl acrylate copolymers (e.g., styrene dodecyl acrylate copolymer, styrene tetradecyl acrylate copolymer, styrene hexadecyl acrylate copolymer, styrene octadecyl acrylate copolymer, etc.), and styrene alkyl methacrylate copolymers (e.g., styrene dodecyl methacrylate copolymer, styrene tetradecyl methacrylate copolymer, styrene hexadecyl methacrylate copolymer, styrene octadecyl methacrylate copolymer, etc.).In these polyalkyl acrylates, the number of carbon atoms in the alkyl group is preferably 12 to 22, more preferably 12 to 20, even more preferably 13 to 18, and particularly preferably 14 to 16, from the viewpoint of ensuring that the refractive index and melting point of the polyalkyl acrylate at 23°C are within a predetermined range. These polyalkyl acrylates may be used individually or in combination of two or more. Furthermore, among these polyalkyl acrylates, from the viewpoint of increasing the degree of temperature change in the visible light absorptivity of the resulting resin composite material and the degree of temperature change in the visible light reflectivity of the resulting laminate, polyalkyl acrylates having an alkyl group with 12 to 22 carbon atoms are preferred, polytetradecyl methacrylate and polyhexadecyl methacrylate are more preferred, and polyhexadecyl methacrylate is particularly preferred.

[0027] Furthermore, the polyalkyl acrylate used in the present invention has a refractive index of 1.41 to 1.51 at 23°C, preferably 1.43 to 1.49. If the refractive index of the polyalkyl acrylate is below the lower limit or above the upper limit, the refractive index difference with the polymer blend containing acrylic polymer and polyvinylidene fluoride in predetermined proportions becomes large, and at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material tends to increase, and the visible light reflectance of the resulting laminate tends to decrease.

[0028] (Resin composition) The resin composition used in the present invention contains 20 to 95% by mass of the acrylic polymer, 4 to 75% by mass of the polyvinylidene fluoride, and 1 to 40% by mass of the polyalkyl acrylate. Such a resin composition exhibits improved transparency at a temperature of at least 60°C, that is, it exhibits a thermochromic effect, and at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material decreases, and the visible light reflectance of the resulting laminate increases.

[0029] In the resin composition, the content of the acrylic polymer must be 20 to 95% by mass. If the content of the acrylic polymer is less than the lower limit or more than the upper limit, the thermochromic effect will not be exhibited, transparency will not improve at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material will be high, and the visible light reflectance of the resulting laminate will be low. Furthermore, from the viewpoint of sufficiently exhibiting the thermochromic effect, sufficiently improving transparency at a temperature of at least 60°C, lowering the visible light absorption rate of the resulting resin composite material, and increasing the visible light reflectance of the resulting laminate, the content of the acrylic polymer is preferably 25 to 90% by mass, and more preferably 30 to 85% by mass.

[0030] Furthermore, the content of polyvinylidene fluoride in the resin composition must be 4 to 75% by mass. If the content of polyvinylidene fluoride is less than the lower limit or more than the upper limit, the thermochromic effect will not be exhibited, transparency will not improve at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material will be high, and the visible light reflectance of the resulting laminate will be low. Also, from the viewpoint of exhibiting a sufficient thermochromic effect, sufficiently improving transparency at a temperature of at least 60°C, having a low visible light absorption rate of the resulting resin composite material, and having a high visible light reflectance of the resulting laminate, the content of polyvinylidene fluoride is preferably 10 to 70% by mass, and more preferably 15 to 65% by mass.

[0031] Furthermore, in the resin composition, the content of the polyalkyl acrylate must be 1 to 40% by mass. If the content of the polyalkyl acrylate is below the lower limit, thermochromic properties will not be exhibited, transparency will not decrease significantly at temperatures below 30°C, the visible light absorption rate of the resulting resin composite material will be low, and the visible light reflectance of the resulting laminate will be high. On the other hand, if the content of the polyalkyl acrylate exceeds the upper limit, the mechanical properties of the resin composition will deteriorate at temperatures above 60°C. Also, from the viewpoint of sufficiently exhibiting a thermochromic effect, decreasing transparency at temperatures below 30°C, increasing the visible light absorption rate of the resulting resin composite material, and decreasing the visible light reflectance of the resulting laminate, the content of the polyalkyl acrylate is preferably 3 to 40% by mass, and more preferably 5 to 40% by mass.

[0032] Furthermore, it is preferable that the resin composition has a sea-island structure comprising a sea phase consisting of a polymer blend containing the acrylic polymer and polyvinylidene fluoride in predetermined proportions, and an island phase consisting of at least a portion of the polyalkyl acrylate. With such a sea-island structure formed, at temperatures of 30°C or below, the polyalkyl acrylate in the island phase crystallizes, making the resin composition opaque, increasing the visible light absorption rate of the resulting resin composite material and decreasing the visible light reflectance of the resulting laminate. Also, at temperatures of at least 60°C, the polyalkyl acrylate melts, and the refractive index of the island phase becomes approximately the same as that of the polymer blend in the sea phase, improving transparency and exhibiting a thermochromic effect, resulting in a lower visible light absorption rate of the resulting resin composite material and a higher visible light reflectance of the resulting laminate.

[0033] In the aforementioned sea-island structure, the size of the island phase is preferably such that the maximum length of the island phase (or diameter if the island phase is circular) is 50 nm to 100 μm, more preferably 100 nm to 80 μm, and particularly preferably 150 nm to 50 μm. If the size of the island phase is less than the lower limit, the thermochromic effect will not be sufficiently expressed, the transparency will not decrease easily at temperatures below 30°C, the visible light absorption rate of the resulting resin composite material will be low, and the visible light reflectance of the resulting laminate will tend to be high. On the other hand, if the size of the island phase exceeds the upper limit, the moldability tends to decrease.

[0034] (Black coloring agent) The black colorant used in the present invention is at least one selected from the group consisting of black pigments and black dyes. Examples of the black pigments include carbon black, carbon nanotubes, carbon fibers, titanium black, perylene black, and oxides, composite oxides, sulfides, sulfates, carbonates, etc., of metals such as copper, iron, manganese, cobalt, chromium, nickel, zinc, calcium, and silver. Examples of the black dyes include organic dyes such as anthraquinone-based, perinone-based, perylene-based, azo-based, methine-based, and quinoline-based dyes. Among these black colorants, carbon particles having a graphite structure are preferred from the viewpoint of affinity with the resin composition.

[0035] In the thermochromic resin composite material of the present invention, it is preferable that 30% by mass or more (preferably 50% by mass or more, more preferably 70% by mass or more) of the black colorant is present in the island phase of the sea-island structure (the phase consisting of the polyalkyl acrylate). This increases the absorption rate of visible light at temperatures of 30°C or below. That is, at temperatures of 30°C or below, the polyalkyl acrylate forms a crystalline phase, and the visible light incident on the thermochromic resin composite material is scattered by the crystalline phase. At this time, the presence of the black colorant in the island phase allows the visible light to be absorbed efficiently.

[0036] The size and shape of the black pigment are preferably spherical with a diameter of 5 nm to 30 μm (preferably 7 nm to 20 μm, more preferably 10 nm to 10 μm). If the size of the black pigment is less than the lower limit, handling of the black pigment tends to become complicated when manufacturing the thermochromic resin composite material. On the other hand, if the size of the black pigment exceeds the upper limit, the phase structure of the resin composition becomes disordered, and the change in visible light absorption rate with temperature tends to become smaller.

[0037] (Glass-based filler) There are no particular restrictions on the glass-based filler used in the present invention, but it is preferable that it has a silicon dioxide purity of 90% or more. A glass-based filler with a silicon dioxide purity of 90% or more has a refractive index at least 60°C that is similar to that of a polymer blend containing acrylic polymer and polyvinylidene fluoride in a predetermined ratio or the polyalkyl acrylate. Therefore, in a resin composition containing the acrylic polymer, the polyvinylidene fluoride, the polyalkyl acrylate and the glass-based filler, transparency is improved at least 60°C, the thermochromic effect is maintained, the visible light absorption rate of the resulting resin composite material is kept low at at least 60°C, and the scratch resistance of the resin composite material and the laminate can be improved while maintaining a high visible light reflectance of the resulting laminate. Furthermore, in a resin composition containing the acrylic polymer, polyvinylidene fluoride, polyalkyl acrylate, and glass-based filler, the thermochromic effect is sufficiently maintained, transparency is sufficiently improved at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material is sufficiently low, and the visible light reflectance of the resulting laminate is sufficiently high. From this viewpoint, the silicon dioxide purity of the glass-based filler is preferably 95% or higher, and more preferably 98% or higher. On the other hand, glass-based fillers with a silicon dioxide purity below the lower limit have a refractive index that is significantly different from that of the polymer blend and the polyalkyl acrylate at a temperature of at least 60°C. Therefore, in a resin composition containing the acrylic polymer, polyvinylidene fluoride, polyalkyl acrylate, and glass-based filler, the thermochromic effect is not maintained, transparency decreases at a temperature of at least 60°C, the visible light absorption rate of the resulting resin composite material tends to increase, and the visible light reflectance of the resulting laminate tends to decrease.

[0038] In the glass-based filler, the refractive index at 23°C is preferably 1.40 to 1.50, and more preferably 1.44 to 1.48. If the refractive index of the glass-based filler is below the lower limit or above the upper limit, the thermochromic effect is not maintained in the resin composition containing the acrylic polymer, the polyvinylidene fluoride, the polyalkyl acrylate, and the glass-based filler. At a temperature of at least 60°C, the transparency decreases, the visible light absorption rate of the resulting resin composite material increases, and the visible light reflectance of the resulting laminate tends to decrease.

[0039] Furthermore, the size and shape of the glass-based filler are preferably spherical with a diameter of 100 nm to 2 mm (preferably 200 nm to 1.5 mm, more preferably 500 nm to 1 mm) or fibrous with a fiber diameter of 100 nm to 2 mm (preferably 200 nm to 1.5 mm, more preferably 500 nm to 1 mm) and a fiber length of 100 μm to 50 mm (preferably 200 μm to 30 mm, more preferably 300 μm to 10 mm). If the size of the glass-based filler is below the lower limit, it tends to become difficult to handle, while if it exceeds the upper limit, the moldability of the resin composition tends to decrease.

[0040] (Thermochromic resin composite material) The thermochromic resin composite material of the present invention contains 0.0005 to 0.03 parts by mass of the black colorant per 100 parts by mass of a resin composition containing the acrylic polymer, polyvinylidene fluoride, and polyalkyl acrylate in predetermined proportions. This thermochromic resin composite material exhibits a change in visible light absorption rate with temperature, with the visible light absorption rate increasing at temperatures below 30°C and decreasing at temperatures below 60°C. For example, in the case of a plate-shaped thermochromic resin composite material with a thickness of 0.5 mm, the difference in visible light absorption rate between temperatures below 30°C and temperatures below 60°C is 10% or more. On the other hand, if the amount of black colorant is below the lower limit, the visible light absorption rate does not improve (especially at temperatures below 30°C), while if the amount of black colorant exceeds the upper limit, the visible light absorption rate becomes too high, making it difficult for the visible light absorption rate to change with temperature. Furthermore, from the viewpoint of increasing the difference in visible light absorption rate between temperatures below 30°C and temperatures at least 60°C, the amount of black colorant is preferably 0.001 to 0.025 parts by mass, more preferably 0.0015 to 0.020 parts by mass, and particularly preferably 0.002 to 0.015 parts by mass, per 100 parts by mass of the resin composition.

[0041] Furthermore, in the thermochromic resin composite material of the present invention, it is preferable that 1 to 100 parts by mass of the glass-based filler is further included per 100 parts by mass of the resin composition. By including the glass-based filler, the scratch resistance of the resulting resin composite material is improved, and the radiative cooling ability of the thermochromic resin composite material can be improved. On the other hand, if the content of the glass-based filler exceeds the upper limit, the moldability tends to decrease. Also, from the viewpoint of scratch resistance, radiative cooling ability, and moldability of the resulting resin composite material, the content of the glass-based filler is more preferably 5 to 40 parts by mass, and particularly preferably 10 to 30 parts by mass, per 100 parts by mass of the thermochromic resin composition.

[0042] There are no particular restrictions on the method for producing such a thermochromic resin composite material, and known kneading methods such as melt kneading can be employed. However, from the viewpoint of having the black colorant present in the island phase made of the polyalkyl acrylate and uniformly dispersing this island phase, first, the black colorant and the polyalkyl acrylate are dry blended, and then the resulting mixture is kneaded (preferably by melt kneading) to prepare a masterbatch (MB). Next, the acrylic polymer, the polyvinylidene fluoride, the polyalkyl acrylate, the masterbatch, and optionally the glass-based filler are dry blended, and then the resulting mixture is kneaded (preferably by melt kneading) to produce the thermochromic resin composite material of the present invention. Furthermore, this thermochromic resin composite material may be molded into a desired shape.

[0043] [Laminate] Next, the laminate of the present invention will be described. The laminate of the present invention comprises a member made of the thermochromic resin composite material of the present invention and a highly reflective layer having a visible light reflectivity of 70% or more, which is disposed on at least a portion of one side of the member.

[0044] (Component made of thermochromic resin composite material) The component made of the thermochromic resin composite material used in the present invention is obtained by molding the thermochromic resin composite material of the present invention into a desired shape. There are no particular restrictions on the shape of such a component made of the thermochromic resin composite material; for example, it may be in the shape of a plate such as a square plate or a disc, or a flexible film.

[0045] When the member made of the thermochromic resin composite material is a plate-shaped member, its thickness is preferably 0.01 to 3.0 mm, more preferably 0.05 to 2.5 mm, and particularly preferably 0.1 to 2.0 mm. When the thickness of the plate-shaped member is below the lower limit, the change in visible light absorption rate with temperature tends to be small, while when the thickness of the plate-shaped member exceeds the upper limit, the temperature response of the visible light absorption rate tends to decrease.

[0046] (High reflective layer) The highly reflective layer used in the present invention is a highly reflective layer with a reflectance of 70% or more for visible light (particularly at a wavelength of 589 nm). When the visible light reflectance of the highly reflective layer falls below the aforementioned lower limit, the change in visible light reflectance due to temperature becomes smaller. Furthermore, the visible light reflectance of the highly reflective layer is preferably 80% or more, more preferably 85% or more, and particularly preferably 90% or more.

[0047] Examples of materials that constitute such a highly reflective layer include metal films, barium sulfate, and polytetrafluoroethylene. Examples of metal films include silver foil (visible light (wavelength 589nm) reflectance: 94%) and aluminum foil (visible light (wavelength 589nm) reflectance: 81%).

[0048] In the high-reflectivity layer, the content (purity) of the main component high-reflectivity material (for example, silver in the case of silver foil, aluminum in the case of aluminum foil, and barium sulfate in the case of a barium sulfate layer) is preferably 70% by mass or more, more preferably 75% by mass or more, and particularly preferably 80% by mass or more. When the content (purity) of the main component high-reflectivity material falls below the lower limit, the change in visible light reflectance due to temperature tends to become smaller.

[0049] Furthermore, the thickness of the high-reflectivity layer is preferably 50 nm to 100 μm, more preferably 75 nm to 50 μm, and particularly preferably 100 nm to 25 μm. When the thickness of the high-reflectivity layer is less than the lower limit, the change in visible light reflectance due to temperature tends to decrease, while when the thickness of the plate-like member exceeds the upper limit, the flexibility of the member tends to decrease.

[0050] (Laminated structure) The laminate of the present invention comprises a member made of the thermochromic resin composite material and the high-reflectivity layer disposed on at least a portion of one side of the member. The reflectivity of visible light of this laminate changes with temperature, with the reflectivity of visible light decreasing at temperatures of 30°C or below and increasing at temperatures of at least 60°C. For example, in the case of a laminate comprising a plate-shaped member made of the thermochromic resin composite material with a thickness of 0.5 mm, the difference in reflectivity of visible light (wavelength 589 nm) between temperatures of 30°C or below and at least 60°C is 10% or more.

[0051] There are no particular limitations on the method for manufacturing such a laminate. For example, the member made of the thermochromic resin composite material and the high-reflectivity layer may be superimposed and then heat-pressed together by press molding or the like, or the metal film may be deposited onto the surface of the member made of the thermochromic resin composite material. [Examples]

[0052] The present invention will be described more specifically below based on examples and comparative examples, but the present invention is not limited to the following examples. The polyhexadecyl acrylate and polytetradecyl acrylate used in the examples and comparative examples were synthesized by the following method.

[0053] (Synthesis Example 1) 12 g of hexadecyl acrylate (HDA, manufactured by Tokyo Chemical Industry Co., Ltd., product code: H1168) and 64 mg of 2,2'-azobisisobutyronitrile (AIBN, manufactured by Kishida Chemical Co., Ltd., product code: 010-05992) were dissolved in 20 ml of toluene. The mixture was then stirred at 70°C for 8 hours under a nitrogen atmosphere to polymerize the HDA. The resulting toluene solution of polyhexadecyl acrylate (PHDA) was reprecipitated by adding a sufficient amount of methanol dropwise, and the resulting precipitate (PHDA) was separated and recovered by filtration. Subsequently, the obtained PHDA was dried in an oven at room temperature under reduced pressure to remove methanol, yielding PHDA with a number-average molecular weight of approximately 30,000, a refractive index of 1.46 (at 23°C), and a melting point of 37°C. The number-average molecular weight was measured using gel permeation chromatography (GPC-101, manufactured by Shoko Science Co., Ltd.), the refractive index was measured using an Abbe refractometer (DR-M2, manufactured by Atago Co., Ltd.), and the melting point was measured using a differential scanning calorimeter (X3, manufactured by TA Instruments).

[0054] (Synthesis Example 2) A polyhexadecylacrylate / tetradecylacrylate copolymer (PHDA / PTDA) with a number average molecular weight of approximately 30,000, a refractive index of 1.46 (at 23°C), and a melting point of 25°C was obtained in the same manner as in Synthesis Example 1, except that 6.0 g of the aforementioned hexadecylacrylate and 5.4 g of tetradecylacrylate (TDA, manufactured by Tokyo Chemical Industry Co., Ltd., product code: T2265) were used instead of 12 g of the aforementioned hexadecylacrylate. The number average molecular weight, refractive index, and melting point were measured in the same manner as in Synthesis Example 1.

[0055] (Preparation Example 1) 5.0 g of polymethyl methacrylate (PMMA, Kuraray Co., Ltd. "Parapet G grade", refractive index: 1.492 (23℃)), 2.69 g of polyvinylidene fluoride (PVDF, Aldrich, catalog number: 427144, refractive index: 1.420 (23℃)), and 34.2 mg of black pigment (carbon black (CB), Aldrich, catalog number: 05-1530-5-500G-J, particle size: 24 nm) were dry-blended. The resulting mixture was then placed in a tabletop miniature mixer (Haake "Minilab") and kneaded at 220℃ for 5 minutes to prepare a masterbatch (MB).

[0056] (Example 1) The resulting resin composite material was prepared by dry blending PMMA, PVDF, PHDA, and the masterbatch (MB) such that the PMMA content was 48 parts by mass, the PVDF content was 32 parts by mass, the PHDA content was 20 parts by mass, and the black pigment content was 0.005 parts by mass. The resulting mixture was then placed in a small tabletop mixer (Haake "Minilab") and kneaded at 220°C for 5 minutes to prepare the resin composite material. The resulting resin composite material was then press-molded using a tabletop press at a temperature of 220°C and a pressure of 6 MPa for 30 seconds to produce a 50 mm × 50 mm × 0.5 mm flat plate.

[0057] (Example 2) A resin composite material was prepared in the same manner as in Example 1, except that the PMMA content in the resulting resin composite material was changed to 72 parts by mass and the PVDF content to 8 parts by mass. A 50 mm × 50 mm × 0.5 mm flat plate was then fabricated.

[0058] (Example 3) A resin composite material was prepared in the same manner as in Example 1, except that the PMMA content in the resulting resin composite material was changed to 32 parts by mass and the PVDF content to 48 parts by mass. A 50 mm × 50 mm × 0.5 mm flat plate was then fabricated.

[0059] <Light absorption rate> A temperature controller is installed in the sample chamber of a haze meter (HGM-3DP, manufactured by Suga Test Instruments Co., Ltd.), and the total light transmittance [%] of a flat plate at 25°C and 60°C is measured using this haze meter. From the obtained total light transmittance, the following formula is used: Light absorption rate [%] = 100 - Total light transmittance [%] The light absorption rate [%] was determined using the following method. The results are shown in Table 1.

[0060] [Table 1]

[0061] As shown in Table 1, the resin composite materials (Examples 1-3) containing acrylic polymer, polyvinylidene fluoride, polyalkyl acrylate, and black colorant in predetermined proportions showed a difference of 10% or more in visible light absorptivity between room temperature (25°C) and high temperature (60°C), confirming that they are thermochromic resin composite materials whose visible light absorptivity changes with temperature.

[0062] (Example 4) The resulting resin composite material was prepared by dry blending PMMA, PVDF, PHDA, the masterbatch (MB), and SiO2 (silicon dioxide, SO-C6 manufactured by Admatex Co., Ltd., silicon dioxide purity: 99% or higher, particle size: 1.8~2.3 μm) so that the PMMA content was 58.5 parts by mass, the PVDF content was 31.5 parts by mass, the PHDA content was 10 parts by mass, the black pigment content was 0.005 parts by mass, and the SiO2 content was 25 parts by mass. The resulting mixture was then placed in a small tabletop mixer (Minilab manufactured by Haake) and kneaded at 220°C for 5 minutes to prepare the resin composite material. The resulting resin composite material was then press-molded using a tabletop press at a temperature of 220°C and a pressure of 6 MPa for 30 seconds to produce a 50 mm × 50 mm × 0.5 mm flat plate.

[0063] This flat plate was placed on top of silver foil (manufactured by Kenis Co., Ltd., catalog number: 68381066, size: 115 mm x 115 mm, thickness: approximately 0.4 μm), and pressed using a tabletop press at a temperature of 220°C and a pressure of 6 MPa for 30 seconds to produce a laminated plate in which the silver foil was heat-pressed onto the entire back surface of the flat plate.

[0064] (Example 5) A resin composite material was prepared in the same manner as in Example 4, except that SiO2 was not included, and then a 50mm x 50mm x 0.5mm flat plate and laminate were produced.

[0065] (Example 6) A resin composite material was prepared in the same manner as in Example 5, except that the content of PMMA in the obtained resin composite material was changed to 48 parts by mass, the content of PVDF to 32 parts by mass, and the content of PHDA to 20 parts by mass. Furthermore, a 50 mm × 50 mm × 0.5 mm flat plate and laminate were produced.

[0066] (Example 7) A resin composite material was prepared in the same manner as in Example 5, except that PMMA, PVDF, PHDA / PTDA, and the masterbatch (MB) were used, such that the resulting resin composite material contained 58.5 parts by mass of PMMA, 31.5 parts by mass of PVDF, 10 parts by mass of PHDA / PTDA, and 0.005 parts by mass of black pigment. A 50 mm × 50 mm × 0.5 mm flat plate and laminate were then produced.

[0067] (Example 8) A resin composite material was prepared in the same manner as in Example 5, except that the PMMA content in the resulting resin composite material was changed to 81 parts by mass and the PVDF content to 9 parts by mass. Furthermore, a 50 mm × 50 mm × 0.5 mm flat plate and laminate were fabricated.

[0068] (Example 9) A resin composite material was prepared in the same manner as in Example 5, except that the PMMA content in the resulting resin composite material was changed to 36 parts by mass and the PVDF content to 54 parts by mass. Furthermore, a 50 mm × 50 mm × 0.5 mm flat plate and laminate were fabricated.

[0069] (Example 10) A resin composite material was prepared in the same manner as in Example 5, except that the PMMA content in the obtained resin composite material was changed to 54 parts by mass, the PVDF content to 36 parts by mass, and the black pigment content to 0.001 parts by mass. Furthermore, a 50 mm × 50 mm × 0.5 mm flat plate and laminate were produced.

[0070] (Comparative Example 1) A resin composite material was prepared in the same manner as in Example 5, except that the content of black pigment in the resulting resin composite material was changed to 0.05 parts by mass. Furthermore, a 50 mm × 50 mm × 0.5 mm flat plate and laminate were produced.

[0071] (Comparative Example 2) A resin composite material was prepared in the same manner as in Example 6, except that black pigment was not included. Furthermore, a 50mm x 50mm x 0.5mm flat plate and laminate were produced.

[0072] <Light reflectance> A rubber heater was placed on the back surface (the side with the silver foil) of the obtained laminate, and the optical reflectance [%] of the laminate was measured at 25°C and 60°C by irradiating the surface of the laminate (the side without the silver foil) with light of wavelength 589 nm using a UV-Vis spectrophotometer (Shimadzu Corporation "UV-3600") equipped with an integrating sphere. The results are shown in Table 2.

[0073] [Table 2]

[0074] As shown in Table 2, laminates (Examples 4-10) made of a resin composite material containing acrylic polymer, polyvinylidene fluoride, polyalkyl acrylate, and a black colorant in predetermined proportions, with silver foil heat-pressed onto the entire back surface, were found to have improved light reflectivity at high temperatures (60°C) compared to room temperature (25°C).

[0075] On the other hand, a laminate (Comparative Example 1) made of a resin composite material containing a predetermined amount of black coloring agent, with silver foil heat-pressed onto the entire back surface, exhibited very low light reflectivity and showed almost no change in light reflectivity with temperature. Furthermore, a laminate (Comparative Example 2) made of a resin composite material without black coloring agent, with silver foil heat-pressed onto the entire back surface, exhibited high light reflectivity, but showed almost no change in light reflectivity with temperature. [Industrial applicability]

[0076] As described above, according to the present invention, it is possible to obtain a resin composite material in which the absorption rate of visible light is high at temperatures of 30°C or below, and the absorption rate of visible light is low at temperatures of at least 60°C. Furthermore, by providing a highly reflective layer such as a metal film on one side of a component made of such a resin composite material, it is possible to obtain a laminate in which the reflectivity of visible light is low at temperatures of 30°C or below, and the reflectivity of visible light is high at temperatures of at least 60°C.

[0077] When sunlight is irradiated onto such a laminate of the present invention, at low temperatures, the absorption rate of sunlight increases (the reflectance of visible light decreases), resulting in a greater amount of heat generated by sunlight. On the other hand, at high temperatures, the absorption rate of sunlight decreases (the reflectance of visible light increases), resulting in a smaller amount of heat generated by sunlight. Therefore, the laminate of the present invention can be applied as an autonomous temperature-regulating material in which the amount of heat generated by sunlight changes with changes in ambient temperature. For example, it is useful as a laminate used in buildings such as residences, factories, and warehouses, as well as in transportation vehicles such as automobiles and trains.

[0078] Furthermore, by attaching such a laminate of the present invention to the surface of an object (e.g., a roof or wall) such that the object is positioned on the highly reflective layer side of the laminate, when the temperature is low, the laminate generates heat due to sunlight, thereby heating the object. When the temperature is high, sunlight is reflected by the laminate, thus suppressing heating of the object due to sunlight. In particular, the laminate of the present invention has a high reflectivity of visible light at temperatures of at least 60°C, making it possible to suppress heating of the object due to sunlight even at relatively low temperatures. Therefore, the laminate of the present invention is particularly useful as a thermal control material that can create a more comfortable living space because it can change the reflectivity of visible light and suppress heating of the object due to sunlight at temperatures around human body temperature (36°C).

Claims

1. A resin composition containing 20 to 95% by mass of an acrylic polymer with a refractive index of 1.46 to 1.56 at 23°C, 4 to 75% by mass of polyvinylidene fluoride with a refractive index of 1.36 to 1.46 at 23°C, and 1 to 40% by mass of polyalkyl acrylate with a refractive index of 1.41 to 1.51 at 23°C, and For every 100 parts by mass of the resin composition, add 0.0005 to 0.03 parts by mass of at least one black colorant selected from the group consisting of black pigments and black dyes. A thermochromic resin composite material characterized by containing the following:

2. The thermochromic resin composite material according to claim 1, further comprising 1 to 100 parts by mass of a glass-based filler with a silicon dioxide purity of 90% or more per 100 parts by mass of the resin composition.

3. A laminate characterized by comprising a member made of the thermochromic resin composite material described in claim 1 or 2, and a highly reflective layer having a visible light reflectivity of 70% or more, disposed on at least a portion of one side of the member.

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