Resin laminated film

Abstract

The present invention exhibits high cooling capacity under direct sunlight and high radio wave permeability, and prevents deterioration of radiation cooling performance when the holes are provided in a resin material and deterioration of cooling performance caused by contamination of the holes.　A light reflection layer (B) has a plurality of holes K and is composed of a second resin. The infrared radiation layer (J) is composed of a first resin that emits heat radiation energy greater than absorbed solar energy at a wavelength of 8 to 13 μm. The holes included in the infrared radiation layer (J) are less than holes included in the light reflection layer (B). The laminated resin layer (M) including the light reflection layer (B) and the infrared radiation layer (J) has an arithmetic average reflectance of 80% or more, which is the wavelength average of the light reflectance from 400 to 800 nm, the arithmetic average reflectance of 70% or more, which is the wavelength average of the light reflectance from 800 to 1200 nm, and the wavelength average of the emissivity of 43% or more at a wavelength from 8 to 13 μm.

Description

Resin laminated film

[0001] The present invention relates to a laminated resin film comprising an infrared emitting layer that emits infrared light from an emitting surface, and a light reflecting layer located on the infrared emitting layer opposite to the side where the emitting surface is present.

[0002] A conventional example of a composite cooling material using the radiative cooling phenomenon is one that is configured by laminating an infrared radiative layer that radiates infrared light from a radiative surface and a light reflective layer that is positioned on the side of the infrared radiative layer opposite to the side where the radiative surface is present (see, for example, Patent Document 1). In order to dissipate heat into space through the radiative cooling phenomenon and cool an object under direct sunlight, it is important to achieve both high solar reflectance and high infrared emissivity.

[0003] JP 2018-526599 A JP 2022-528289 A International Publication No. 2018 / 062541

[0004] Previous radiative cooling materials achieved high solar reflectivity by reflecting sunlight with a thin metal film, but using a thin metal film had the problem of increased absorption, which caused the material temperature to rise under direct sunlight. Furthermore, metal thin films had low radio wave transmittance, which made it difficult for communication devices to function when enclosed in a space. Another issue with using a thin metal film as a reflective layer was that if the surface was scratched and the metal layer was exposed, corrosion would begin at the metal layer, causing the metal layer to become discolored due to oxidation, which reduced the reflectivity. Furthermore, when a thin metal film was used as a reflective layer, even a small amount of metal oxide was easily discolored, which meant that the degree of decrease in reflectivity upon degradation was greater than with a reflective layer made of resin.

[0005] There are also radiative cooling materials that increase the reflectivity of sunlight by making the resin porous (see Patent Document 2). In the case of such radiative cooling materials, if the porous portion is exposed on the outermost surface, it is easily soiled by rainwater, etc. If the outermost surface of the radiative cooling material becomes soiled, even if the soiling absorbs sunlight, the radiative cooling material itself does not heat up because there is little thermal contact between the soiling and the radiative cooling material. However, if the inside of the porous portion is contaminated, the heat converted from sunlight by the soiling has no place to escape and heats the material well. As described above, radiative cooling materials with porous portions exposed on the surface are avoided from the viewpoint of contamination.

[0006] There are also radiative cooling materials that utilize the porous material itself as a radiation layer (see Patent Document 3). It is difficult to maximize the radiative cooling capacity of such radiative cooling materials in the atmospheric window region. Porous materials include various types, such as polyethylene terephthalate, polypropylene, polyethylene, and polyethylene naphthalate. However, since the amount of material contributing to radiation decreases when the material is made porous, it is necessary to increase the thickness to achieve a large radiative cooling capacity. Radiative cooling materials are designed to cool the object to which they are attached, and increasing the resin layer, especially the porous resin layer, impedes the radiative cooling material's capacity. From this perspective, designs that use the porous resin layer itself to radiate pose a challenge in cooling the object.

[0007] Furthermore, when improving radiation capacity by using a porous material, the poor thermal conductivity of the porosity prevents the temperature of the object to be cooled from reaching the resin located on the outermost surface, resulting in insufficient cooling of the object. Furthermore, in the case of porous resin layers in which air-containing layers are stacked in a mille-feuille-like pattern, the emissivity tends to decrease when the layers are multi-layered compared to when the layers are not multi-layered. This is because the optical multilayer film structure forms a photonic bandgap structure, improving reflectivity. For this reason, using a porous resin layer not only as a reflective layer but also as an emissive layer is not desirable in terms of improving the cooling structure of radiative cooling materials.

[0008] The object of the present invention is to provide a resin laminate film that can exhibit high cooling capacity and high radio wave transmittance under direct sunlight, and can prevent a decrease in radiative cooling performance when holes are provided in the resin material and a decrease in cooling performance due to contamination of the holes.

[0009] a laminated resin film for achieving the above object, the laminated resin film comprising: an infrared radiation layer that emits infrared light from a radiation surface; and a light-reflecting layer located on the side of the infrared radiation layer opposite to the side where the radiation surface is present, the laminated resin film being characterized in that: the light-reflecting layer has a plurality of voids and is made of a second resin; the infrared radiation layer is made of a first resin that emits thermal radiation energy at a wavelength of 8 μm to 13 μm that is greater than the absorbed solar light energy; the number of voids contained in the infrared radiation layer is fewer than the number of voids contained in the light-reflecting layer; and the laminated resin layer including the light-reflecting layer and the infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of the emissivity at wavelengths of 8 μm to 13 μm of 43% or more.

[0010] According to the above characteristic configuration, firstly, since a metal thin film is not used as the light-reflecting layer, the solar light absorption rate can be reduced and the temperature rise of the resin laminate film can be suppressed compared to a configuration using a metal thin film as the light-reflecting layer. Furthermore, since the radio wave transmittance can be relatively high, even in a situation where a wireless communication device is surrounded by a resin material film having the above characteristic configuration, good communication by the wireless communication device can be maintained. Furthermore, the infrared emitting layer, which is usually installed with its emitting surface facing the atmosphere, contains fewer pores than the pores contained in the light-reflecting layer, and more preferably, the infrared emitting layer contains substantially no pores. This configuration makes it difficult for the infrared emitting layer to be soiled by rainwater, etc., and effectively prevents the soil from absorbing solar light and heating the infrared emitting layer.

[0011] In addition, by configuring the infrared radiation layer to have substantially no pores, the volume fraction of the first resin material that contributes to radiation in the radiative cooling layer can be sufficiently secured, thereby ensuring sufficient radiative cooling capacity. Furthermore, the thermal conductivity can be improved, making it easier for heat from the object to be cooled to be transferred to the radiating surface, and improving the cooling effect can be expected. Furthermore, a configuration in which a photonic band gap structure is not substantially formed inside the first resin layer that constitutes the infrared radiation layer can be realized, thereby improving the emissivity of the infrared radiation layer.

[0012] In addition to the configurations described above, by configuring the light reflective layer from a second resin having a plurality of voids, the inventors have confirmed through tests described below that it is possible to realize a resin laminate film in which the laminate resin layer combining the light reflective layer and the infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of the emissivity at wavelengths of 8 μm to 13 μm, of 43% or more.

[0013] As described above, in a laminated resin layer having an arithmetic mean reflectance of 80% or more, which is the wavelength average of the reflectance of light having a wavelength of 400 nm to 800 nm, and an arithmetic mean reflectance of 70% or more, which is the wavelength average of the reflectance of light having a wavelength of 800 nm to 1200 nm, the light-reflecting layer absorbs only about 2% of the solar energy, due to the influence of the absence of metal. As a result, the solar energy absorbed by the light-reflecting layer at the meridian in summer is reduced to 20 W / m ２ The radiation cooling can be performed even better.

[0014] As a result, a resin laminate film can be realized that can exhibit high cooling capacity under direct sunlight and high radio wave transmittance, and can prevent a decrease in radiative cooling performance when holes are provided in the resin material and a decrease in cooling performance due to contamination of the holes.

[0015] A further characteristic feature of the resin laminate film is that the infrared radiation layer contains a filler in the first resin.

[0016] As explained above, an infrared radiation layer, which is usually installed with its radiation surface facing the atmosphere, is composed of a first resin layer without pores to improve antifouling properties, radiation cooling capacity, and heat transfer in a direction intersecting the radiation surface, but by including a filler in the first resin as in the characteristic configuration described above, the infrared radiation layer can also exhibit a certain level of light reflection performance due to the difference in refractive index between the first resin layer and the filler. This makes it possible to reflect solar radiation not only in the light reflection layer but also in the infrared radiation layer, and maintain a high reflectance of the entire material.

[0017] A further characteristic feature of the resin laminate film is that the thickness of the second resin is 10 μm or more and 500 μm or less.

[0018] As described above, by setting the thickness of the second resin of the light-reflecting layer to 10 μm or more, the light-reflecting layer made of the second resin having a plurality of pores can satisfactorily ensure the reflectivity required for radiative cooling. In addition, by setting the thickness to 500 μm or less, the insulating effect of the second resin having pores containing air or the like can be kept below a certain level, ensuring a certain level of cooling performance for the object to be cooled. Incidentally, thicknesses of 500 μm or more are undesirable because, from the perspective of rigidity, it becomes difficult to conform the material to the curved portion when applied to the curved portion, and forcing the material to conform can destroy the material. Furthermore, if the thickness is too thick during roll-to-roll processing, the amount of material that can be produced at one time is reduced, which is undesirable. That is, by selecting an appropriate material for the second resin having a plurality of pores and providing a light-reflecting layer with a thickness of 10 μm to 500 μm together with the infrared radiation layer, it is possible to achieve an arithmetic mean reflectance of 80% or more, which is the wavelength average of the reflectance of light in the wavelength range of 400 nm to 800 nm, and an arithmetic mean reflectance of 70% or more, which is the wavelength average of the reflectance of light in the wavelength range of 800 nm to 1200 nm. The thickness of the light-reflecting layer is preferably 50 to 300 μm, and more preferably 75 to 200 μm.

[0019] As a further characteristic feature of the resin laminate film, the thickness of the first resin is preferably 10 μm or more and 500 μm or less. In particular, according to the resin laminate film of the present invention, the first resin of the infrared emitting layer does not contain multiple voids and can exhibit higher radiation performance than infrared emitting layers containing voids. Therefore, the required radiation performance can be well secured even with a relatively thin film layer of 500 μm. Incidentally, a thickness of 500 μm or more is undesirable because it becomes difficult to conform the material to a curved portion when applied to a curved portion from the perspective of rigidity, and forcing the material to conform can destroy the material. Furthermore, a thickness that is too thick during roll-to-roll processing is undesirable because it reduces the amount of material that can be produced at one time. Furthermore, by ensuring a thickness of 10 μm or more, sufficient emissivity can be secured, and even if there are irregularities on the surface of the light-reflecting layer due to the multiple voids contained in the second resin, the irregularities are unlikely to be reflected on the radiation surface of the infrared emitting layer, thereby effectively suppressing the adhesion of dirt to the radiation surface.

[0020] A further characteristic feature of the resin laminate film is that the pores of the second resin have a refractive index smaller than that of the second resin, and the arithmetic mean pore diameter of the pores is 0.1 μm or more and 3.0 μm or less.

[0021] As described above, it is preferable that the pores in the second resin of the light-reflecting layer have a refractive index smaller than that of the second resin, and that the arithmetic mean pore diameter of the pores be 0.1 μm or more and 3.0 μm or less. The inventors have confirmed that when the arithmetic mean pore diameter of the pores is set to a plurality of arithmetic mean pore diameters in the range of 0.1 μm or more and 3.0 μm or less, good light reflectance can be achieved at wavelengths of 400 nm to 800 nm and 800 nm to 1200 nm. In the present invention, the arithmetic mean pore diameter of the pores is defined as the arithmetic mean of the shortest inner diameters of the pores. Furthermore, the shape of the pores may be not only spherical, but also flat or polyhedral, having short and long sides.

[0022] A further characteristic feature of the resin laminate film is that the volume ratio of the voids in the light reflecting layer is 0.1% by volume or more and 60% by volume or less.

[0023] The inventors have confirmed that, as described above, by setting the volume fraction of voids in the light-reflecting layer, the reflectance of the light-reflecting layer can be adjusted to the above-mentioned arithmetic mean reflectance. More preferably, the volume fraction of voids in the light-reflecting layer is 1% by volume or more and 50% by volume or less, and the volume fraction of voids in the light-reflecting layer is 10% by volume or more and 40% by volume or less. Having voids of 60% by volume or more reduces thermal conductivity, which can lead to heat accumulation in systems with internal heat sources, making it undesirable from the perspective of heat dissipation. Furthermore, having voids of 60% by volume or more also poses the problem of reduced strength. Furthermore, if the volume fraction of voids is 0.1% by volume or less, it is difficult to sufficiently improve reflectance even by adjusting the average particle size and arrangement of the voids.

[0024] Furthermore, the laminated resin layer preferably has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 400 nm to 800 nm, of 84% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 800 nm to 1200 nm, of 75% or more, and more preferably has an arithmetic mean reflectance of 88% or more at wavelengths of 400 nm to 800 nm and 80% or more at wavelengths of 800 nm to 1200 nm.

[0025] A further characteristic feature of the resin laminate film is that the laminate resin layer has an arithmetic mean transmittance, which is the wavelength average of the light transmittance in the wavelength range of 400 nm to 800 nm, of 1% or more and 12% or less.

[0026] According to the present invention, the arithmetic mean transmittance, which is the wavelength average of the light transmittance from 400 nm to 800 nm, is set to 1% or more and 12% or less. This allows light with wavelengths of 400 nm to 800 nm to be transmitted well through both the first resin of the infrared radiation layer and the second resin of the light-reflecting layer, and the light is reflected at the boundary between the second resin of the light-reflecting layer and the pores, thereby improving the reflectance of the laminated resin layer. In other words, the absorption rate of the laminated resin layer can be reduced. Furthermore, having a light transmittance of 1% or more is advantageous in that it ensures good lighting when used outdoors.

[0027] Furthermore, the laminated resin layer preferably has an average wavelength emissivity of 70% or more in the wavelength range of 8 μm to 13 μm, and more preferably has an average wavelength emissivity of 85% or more in the wavelength range of 8 μm to 13 μm.

[0028] A further characteristic feature of the resin laminate film is that the second resin contains a filler.

[0029] As in the above characteristic configuration, the second resin forming the light-reflecting layer is configured to contain a filler in addition to the multiple voids described above, so that light can be reflected not only at the boundary between the second resin and the voids but also at the boundary between the second resin and the filler.Therefore, for example, in order to ensure a certain level of thermal conductivity, even if the volume ratio of voids to the second resin is made relatively low or the thickness is kept thin, a high arithmetic mean reflectance can be maintained.

[0030] A further characteristic feature of the resin laminate film is that the filler is one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate, and they may be porous.

[0031] By incorporating the above-mentioned filler into the first resin forming the infrared radiation layer or the second resin forming the light-reflecting layer, good light reflectivity can be achieved for the laminated resin layer as a whole. Note that the inventors have confirmed that, in particular, when one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate are used as the filler, the laminated resin layer can exhibit high enough reflectivity to adequately exhibit radiative cooling function, in terms of arithmetic mean reflectivity, which is the wavelength average of light reflectivity at wavelengths from 400 nm to 800 nm, and arithmetic mean reflectivity, which is the wavelength average of light reflectivity at wavelengths from 800 nm to 1,200 nm.

[0032] Furthermore, it is preferable that the second resin of the light-reflecting layer contains at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate, and more preferably, the first resin forming the infrared radiation layer contains at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate.

[0033] As shown in FIG. 2, the resin having a carbon-fluorine bond (C—F) is CHF and CF ２ The absorption coefficient due to this is widely spread over a wide band from 8 μm to 13 μm, which is the atmospheric window, with a particularly large absorption coefficient at 8.6 μm. In addition, with regard to the wavelength band of sunlight, there is no noticeable absorption coefficient in the wavelength range from 0.3 μm to 2.5 μm, where the energy intensity is high.

[0034] Furthermore, in resins having carbon-chlorine bonds (C-Cl), the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more, centered around a wavelength of 12 μm. Furthermore, in the case of vinyl chloride resin, an absorption coefficient due to the C-H bending vibration of the alkene contained in the main chain appears at a wavelength of around 10 μm, due to the influence of chlorine electron withdrawal. The inventors selected the material for the first resin described above, taking these absorption characteristics into consideration.

[0035] The first resin preferably includes at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

[0036] In particular, for wavelengths at which resin materials having carbon-fluorine bonds (C-F) exhibit absorption coefficients in the ultraviolet to visible range, the bond energies of the C-C bond, C-H bond, and C-F bond in the basic structural portion of polyvinylidene fluoride (PVDF) are calculated to be 4.50 eV, 4.46 eV, and 5.05 eV. These correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and absorb light of these wavelengths. For this reason, from the perspective of absorbing ultraviolet light in the first resin of the infrared radiation layer and reducing the amount of ultraviolet light transmitted through the light-reflecting layer, it is preferable to use polyvinyl fluoride or polyvinylidene fluoride as the first resin.

[0037] A further characteristic feature of the resin laminate film is that the first resin contains an ultraviolet absorber, and the infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the ultraviolet reflectance in the wavelength range of 340 nm to 400 nm, of 50% or less.

[0038] According to the above-described characteristic configuration, the first resin forming the infrared radiation layer contains an ultraviolet absorber, and the arithmetic mean reflectance, which is the wavelength average of the ultraviolet reflectance of the infrared radiation layer in the wavelength range of 340 nm to 400 nm, is 50% or less. Therefore, ultraviolet rays can be suitably absorbed by the ultraviolet absorber, and ultraviolet rays can be made less likely to be reflected. This reduces the amount of ultraviolet rays that transmits through the first resin forming the infrared radiation layer and the second resin forming the light reflection layer, and effectively suppresses deterioration of the first resin layer and the second resin layer due to ultraviolet rays.

[0039] A further characteristic feature of the resin laminate film is that the light-reflecting layer and the infrared radiation layer are connected by a connecting layer made of at least one of an adhesive, a pressure-sensitive adhesive, and a glue, the connecting layer being included in the laminate resin layer, and the connecting layer containing at least one of a filler and hollow particles.

[0040] In particular, as described above, by incorporating fillers or hollow particles having an arithmetic mean particle size of, for example, about 0.1 μm or more and 5 μm or less into the connection layer, the reflectance of light in the ultraviolet to visible region can be improved, and the thickness of the laminated resin layer (particularly the light-reflecting layer) can be reduced to obtain the desired reflectance.

[0041] A further characteristic feature of the resin laminate film is that the pores of the second resin have a flat shape.

[0042] According to the above characteristic configuration, it is possible to provide multiple layers with different refractive indices, which makes it easier for light to be reflected compared to when the holes have a non-flat structure at the same thickness, and has the advantage of making it easier to increase the reflectivity even at the same thickness.

[0043] The resin laminate film described above may have a connecting resin layer on the side of the light-reflecting layer opposite the infrared radiation layer, which allows the resin laminate film to be suitably bonded to other materials, thereby providing a good cooling effect for various materials.

[0044] FIG. 1 is a diagram illustrating an embodiment of a resin laminate film. FIG. 2 is a diagram illustrating another embodiment of a resin laminate film. FIG. 3 is a diagram illustrating the relationship between the absorption coefficient and wavelength band of a resin material. FIG. 4 is a diagram illustrating the relationship between the light absorptance and wavelength of a resin material. FIG. 5 is a diagram illustrating the emissivity spectrum of a vinyl chloride resin. FIG. 6 is a diagram illustrating the emissivity spectrum of a vinylidene chloride resin. FIG. 7 is a diagram illustrating the emissivity spectrum of an ethylene terephthalate resin. FIG. 8 is a diagram illustrating the relationship between the temperature of the emitting surface and the temperature of the light reflecting layer. FIG. 9 is a diagram illustrating the light absorptance spectrum of an ethylene terephthalate resin.

[0045] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic structure of resin laminate film] As shown in Fig. 1, the resin laminate film CP has a laminated structure including an infrared emitting layer J that radiates infrared light IR from an emitting surface H, and a light reflecting layer B that is located on the side of the infrared emitting layer J opposite to the side where the emitting surface H is present, and is formed into a film shape. In other words, the resin laminate film CP is configured as a radiative cooling film.

[0046] The light-reflecting layer B has a plurality of pores K and is made of a second resin, and the infrared-emitting layer J is made of a first resin that emits thermal radiation energy at a wavelength of 8 μm to 13 μm that is greater than the absorbed solar light energy. The infrared-emitting layer J contains fewer pores K than the light-reflecting layer B, and the infrared-emitting layer J is a layer that does not substantially contain pores K.

[0047] Furthermore, the laminated resin layer M, which is a combination of the light-reflecting layer B and the infrared-emitting layer J, is configured so that the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, is 80% or more, the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, is 70% or more, and the wavelength average of the emissivity at wavelengths of 8 μm to 13 μm is 43% or more. In this specification, the laminated resin layer M is a concept that also includes the connecting layer S that connects the light-reflecting layer B and the infrared-emitting layer J.

[0048] More preferably, the laminate resin layer M has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 400 nm to 800 nm, of 84% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 800 nm to 1200 nm, of 75% or more. The laminate resin layer M has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 400 nm to 800 nm, of 88% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 800 nm to 1200 nm, of 80% or more. Furthermore, the laminate resin layer M more preferably has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light at wavelengths of 8 μm to 13 μm, of 70% or more, and even more preferably an arithmetic mean reflectance, which is the wavelength average of the emissivity, of 85% or more. Incidentally, the reflectance can be improved by selecting materials for the infrared emitting layer J, the connecting layer S, and the light reflecting layer B such that the difference in refractive index between them is large. For example, TiO ２ For the light reflecting layer B, an acrylic adhesive can be used, and for the light reflecting layer B, PET containing a plurality of pores can be used.

[0049] By having this characteristic, the laminated resin layer M can suppress the solar energy absorption to 2% or less, and the solar energy absorbed at the meridian in the summer in Japan can be reduced to 20 W / m ２ It can be about.

[0050] In this embodiment, light L includes ultraviolet light, visible light, and infrared light, and when expressed in terms of the wavelength of light as electromagnetic waves, includes electromagnetic waves with wavelengths of 10 nm to 20,000 nm (electromagnetic waves of 0.01 μm to 20 μm). The solar light spectrum exists in a wavelength range of 300 nm to 4,000 nm, and the intensity increases as the wavelength increases from 400 nm, with the intensity being particularly high in a wavelength range of 500 nm to 1,800 nm.

[0051] In this embodiment, the laminated resin layer M is configured so that the arithmetic mean transmittance, which is the wavelength average of the light transmittance in the wavelength range of 400 nm to 800 nm, is 1% or more and 12% or less.

[0052] Therefore, the resin laminate film CP is configured to reflect a portion of the light L incident on the resin laminate film CP at the radiation surface H of the infrared radiation layer J, and to reflect the light (sunlight, etc.) that has passed through the infrared radiation layer J out of the light L incident on the resin laminate film CP at the light reflecting layer B and to allow it to escape to the outside from the radiation surface H.

[0053] The resin laminate film CP is configured to cool an object to be cooled (not shown) located on the opposite side of the light reflecting layer B from the side where the infrared radiation layer J is present, by converting heat input to the resin laminate film CP (for example, heat input by thermal conduction from the object to be cooled) into infrared light IR by the infrared radiation layer J and radiating the infrared light IR, thereby cooling the object to be cooled.

[0054] That is, the resin laminate film CP is configured to reflect light L irradiated onto the resin laminate film CP, and to radiate heat transferred to the resin laminate film CP (for example, heat transferred from the atmosphere or from the object to be cooled) to the outside as infrared light IR. Furthermore, the infrared emitting layer J and the light reflecting layer B are flexible, so that the resin laminate film CP (radiative cooling film) is configured to be flexible.

[0055] The light-reflecting layer B and the infrared-emitting layer J are connected by a connecting layer S made of at least one of an adhesive, a pressure-sensitive adhesive, and a glue. Although not shown, the connecting layer S contains at least one of a filler and hollow particles, which can improve the reflectance of light in the ultraviolet to visible light range and reduce the thickness of the laminated resin layer M (particularly the light-reflecting layer) to obtain the desired reflectance. The filler and hollow particles preferably have an arithmetic mean particle diameter of approximately 0.1 μm to 5 μm. Examples of suitable fillers include titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate, both in a granular form. This improves the reflectance of light in the ultraviolet to visible region, and reduces the thickness of the laminated resin layer M (particularly the light reflecting layer B) to obtain a desired reflectance.

[0056] In addition, the resin laminate film CP is used to implement a radiative cooling method in which infrared light IR is radiated from a radiation surface H on the opposite side of the surface of the infrared radiation layer J that is in contact with the light reflecting layer B. Specifically, the radiation surface H is directed toward the sky, and the radiation cooling method is implemented in which infrared light IR is radiated from the radiation surface H that faces the sky.

[0057] [Infrared-Emitting Layer] The first resin forming the infrared-emitting layer J preferably contains an ultraviolet absorber, and the infrared-emitting layer J preferably has an arithmetic mean reflectance, which is the wavelength average of the reflectance of ultraviolet light in the wavelength range of 340 nm to 400 nm, of 50% or less. Suitable examples of the ultraviolet absorber include benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, hindered amine-based stabilizers, benzophenone-based ultraviolet absorbers, cyanoacrylate-based ultraviolet absorbers, salicylate-based ultraviolet absorbers, and oxanilide-based ultraviolet absorbers. Benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and hindered amine-based stabilizers are particularly preferred because they can absorb ultraviolet light up to the longer wavelength side. The first resin preferably contains at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate, and more preferably contains at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

[0058] A colorless resin material containing a carbon-fluorine bond (C-F), a carbon-chlorine bond (C-Cl), a carbon-oxygen bond (C-O), an ester bond (R-COO-R), an ether bond (C-O-C bond), or a benzene ring can be used for the first resin forming the infrared radiation layer J. For each resin material (excluding the carbon-oxygen bond), the wavelength range in which it has an absorption coefficient in the atmospheric window wavelength band is shown in Figure 3.

[0059] According to Kirchhoff's law, emissivity (ε) and optical absorptivity (A) are equal. Optical absorptivity can be calculated from the absorption coefficient (α) using the equation A = 1-exp(-αt) (hereafter referred to as the optical absorptivity equation), where t is the film thickness. In other words, adjusting the film thickness of the infrared radiation layer J allows for greater thermal radiation in wavelength bands with larger absorption coefficients. For outdoor radiative cooling, it is recommended to use a material with a large absorption coefficient in the wavelength range of 8 μm to 13 μm, which is the atmospheric window wavelength band. Furthermore, to suppress the absorption of sunlight, it is recommended to use a material with no or a small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, especially 0.4 μm to 2.5 μm. As can be seen from the equation for the absorption coefficient and absorptivity, optical absorptivity (emissivity) varies depending on the film thickness of the resin material.

[0060] In order to lower the temperature below the surrounding atmosphere through radiative cooling in a solar radiation environment, if a material is selected that has a large absorption coefficient in the wavelength band of the atmospheric window and almost no absorption coefficient in the wavelength band of sunlight, then by adjusting the film thickness, it will absorb almost no sunlight but emit a lot of thermal radiation from the atmospheric window, meaning that it is possible to create a state in which the output from radiative cooling is greater than the input of sunlight.

[0061] For carbon-fluorine bonds (C—F), CHF and CF ２ The absorption coefficient due to this is widely spread over a wide band from 8 μm to 13 μm, which is the atmospheric window, with a particularly large absorption coefficient at 8.6 μm. In addition, with regard to the wavelength band of sunlight, there is no noticeable absorption coefficient in the wavelength range from 0.3 μm to 2.5 μm, where the energy intensity is high.

[0062] An example of a resin material having a carbon-fluorine bond (C-F) is polyvinylidene fluoride (PVDF), which is a partially fluorinated resin. Note that hereafter, polyvinylidene fluoride may be referred to as vinylidene fluoride resin, but both terms are used to refer to the same material. The same applies to other resins.

[0063] For carbon-chlorine bonds (C-Cl), the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more, centered around a wavelength of 12 μm. Furthermore, examples of resin materials include polyvinyl chloride (PVC) and vinylidene chloride resin (PVDC). In the case of vinyl chloride resin, the electron-withdrawing effect of chlorine causes an absorption coefficient due to the C-H bending vibration of the alkene contained in the main chain to appear at a wavelength of around 10 μm.

[0064] Ester bonds (R-COO-R) and ether bonds (C-O-C bonds) have absorption coefficients in the wavelength range of 7.8 μm to 9.9 μm. Furthermore, the carbon-oxygen bonds contained in ester bonds and ether bonds exhibit strong absorption coefficients in the wavelength range of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, a wide range of absorption appears in the wavelength range of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements caused by the influence of the benzene ring.

[0065] Resins having these bonds include ethylene terephthalate resin, ethylene naphthalate resin, and polymethyl methacrylate resin.

[0066] [Consideration of Light Absorption] We will now consider the light absorption in the ultraviolet-visible region of resin materials with the bonds and functional groups described above, i.e., sunlight absorption. The origin of absorption from ultraviolet to visible light is the transition of electrons that contribute to the bond. Absorption in this wavelength region can be understood by calculating the bond energy. First, we will consider the wavelengths at which absorption coefficients occur in the ultraviolet to visible region of resin materials with carbon-fluorine bonds (C-F). The bond energies of the C-C bond, C-H bond, and C-F bond in the basic structural parts of polyvinylidene fluoride (PVDF) are calculated to be 4.50 eV, 4.46 eV, and 5.05 eV. These correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and they absorb light of these wavelengths.

[0067] Since the sunlight spectrum only contains wavelengths longer than 0.300 μm, when fluororesin is used, it hardly absorbs the ultraviolet, visible, and near-infrared rays of sunlight. Note that ultraviolet rays are defined as wavelengths shorter than 0.400 μm, visible light as wavelengths from 0.400 μm to 0.800 μm, near-infrared rays as wavelengths from 0.800 μm to 3 μm, mid-infrared rays as wavelengths from 3 μm to 8 μm, and far-infrared rays as wavelengths longer than 8 μm.

[0068] Regarding carbon-chlorine bonds (C-Cl), the bond energy between carbon and chlorine in alkenes is 3.28 eV, and the wavelength is 0.378 μm, so they absorb a lot of ultraviolet light in sunlight, but have almost no absorption in the visible range. Figure 4 shows the absorptance spectrum from ultraviolet to visible range for a 100 μm thick vinyl chloride resin, which exhibits increased light absorption at wavelengths shorter than 0.38 μm. Figure 4 shows the absorptance spectrum from ultraviolet to visible range for a 100 μm thick vinylidene chloride resin, which exhibits a slight increase in the absorptance spectrum at wavelengths shorter than 0.4 μm.

[0069] Resins that have an ester bond (R-COO-R), an ether bond (C-O-C bond), or a benzene ring include methyl methacrylate resin, ethylene terephthalate resin, and ethylene naphthalate resin. For example, the bond energy of the C-C bond in acrylic is 3.93 eV, and it absorbs sunlight with wavelengths shorter than 0.315 μm, but has almost no absorption in the visible range.

[0070] As an example of a resin material having these bonds and functional groups, the absorbance spectrum from ultraviolet to visible light of a 5 mm-thick methyl methacrylate resin is shown in Figure 4. Note that the methyl methacrylate resin shown here is a commonly available commercially available resin containing a benzotriazole-based UV absorber. Because the plate is 5 mm thick, the wavelengths with small absorption coefficients are also large, resulting in high light absorption at wavelengths longer than 0.315 μm and shorter than 0.38 μm.

[0071] As an example of a resin material having these bonds and functional groups, the absorptance spectrum from ultraviolet to visible light of a 40 μm-thick ethylene terephthalate resin is shown in Figure 4. As shown in the figure, the absorptance increases as the wavelength approaches 0.315 μm, at which point the absorptance increases sharply. Note that as the thickness of ethylene terephthalate resin increases, the absorptance due to the absorption edge derived from C-C bonds also increases slightly longer than 0.315 μm, and similar to methyl methacrylate resin, the absorptance in ultraviolet light increases.

[0072] The infrared radiation layer J may be a single layer film of one type of resin material, a multilayer film of multiple types of resin materials, a single layer film of a resin material blended with multiple types of resin materials, or a multilayer film of a resin material blended with multiple types of resin materials, as long as the resin material has the above-mentioned emissivity (light emissivity) and light absorptivity characteristics. Blends also include copolymers such as alternating copolymers, random copolymers, block copolymers, and graft copolymers, as well as modified copolymers with substituted side chains.

[0073] [Emissivity of Polyvinyl Chloride Resin and Vinylidene Chloride Resin] Figure 5 shows the emissivity of polyvinyl chloride resin (PVC) at the atmospheric window, as a representative example of a resin with a carbon-chlorine bond. Figure 6 shows the emissivity of polyvinylidene chloride resin (PVDC) at the atmospheric window. With regard to carbon-chlorine bonds, the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. Furthermore, in the case of polyvinyl chloride resin, due to the electron-withdrawing effect of chlorine, an absorption coefficient resulting from the C-H bending vibration of the alkene contained in the main chain appears at a wavelength of around 10 μm. The same is true for polyvinylidene chloride resin. Due to these effects, the wavelength-averaged emissivity at a thickness of 10 μm is 43% from 8 μm to 13 μm, which falls within the wavelength-averaged emissivity requirement of 43% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0074] [Emissivity of Ethylene Terephthalate Resin] Figure 7 shows the emissivity of ethylene terephthalate resin in the atmospheric window, a representative example of a resin containing ester bonds or benzene rings. Ester bonds have an absorption coefficient in the wavelength range of 7.8 μm to 9.9 μm. Furthermore, the carbon-oxygen bond contained in the ester bond exhibits a strong absorption coefficient in the wavelength range of 8 μm to 10 μm. When benzene rings are introduced into the side chains of hydrocarbon resins, a wide range of absorption occurs in the wavelength range of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements caused by the benzene ring. Due to these effects, the wavelength-averaged emissivity of a 10 μm thick film is 71% from 8 μm to 13 μm, which falls within the wavelength-averaged range of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases with increasing film thickness.

[0075] [Surface Temperature of the Light Reflecting Layer and the Infrared Emitting Layer] Thermal radiation from the atmospheric window of the infrared emitting layer J occurs near the surface of the resin material. As can be seen from Figure 5, in the case of vinyl chloride resin, even if the thickness exceeds 100 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of vinyl chloride resin, thermal radiation from the atmospheric window occurs within a depth of approximately 100 μm from the surface, and radiation from deeper parts does not escape. As can be seen from Figure 6, vinylidene chloride resin is similar to vinyl chloride resin.

[0076] 7, in the case of ethylene terephthalate resin, even if the thickness exceeds 125 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of ethylene terephthalate resin, thermal radiation in the atmospheric window occurs in a portion about 100 μm deep from the surface, and radiation from deeper portions does not escape to the outside.

[0077] As described above, thermal radiation from the atmospheric window region generated from the surface of the resin material occurs within a depth of approximately 100 μm from the surface. As the resin thickness increases beyond this, the cold generated by radiation cooling of the resin laminate film is insulated by the resin material that does not contribute to thermal radiation. Ideally, the infrared radiation layer J is formed from a first resin that does not absorb sunlight at all, and the infrared radiation layer J is fabricated on the light-reflecting layer B. In this case, sunlight is absorbed only by the light-reflecting layer B of the resin laminate film CP. The thermal conductivity of resin materials is generally about 0.2 W / m / K. Taking this thermal conductivity into account, calculations show that if the thickness of the infrared radiation layer J exceeds 20 mm, the temperature of the cooling surface (the surface of the light-reflecting layer B opposite the side where the infrared radiation layer J is present) will rise.

[0078] Even if an ideal resin material that does not absorb sunlight at all exists, the thermal conductivity of the first resin of the infrared radiation layer J is generally about 0.2 W / m K, so if the thickness exceeds 20 mm as shown in Figure 8, the light reflecting layer B will be heated by sunlight and the object to be cooled placed on the side of the light reflecting layer B will be heated. In other words, the thickness of the first resin of the infrared radiation layer J needs to be 20 mm or less.

[0079] Figure 8 is a plot of the surface temperature of the radiation surface H of the resin laminated film (radiative cooling film) and the temperature of the light-reflecting layer B, calculated assuming a sunny day in summer in western Japan at noon. The sunlight is AM 1.5, and the average value of the solar radiation intensity during the day in summer is 350 W / m ２ The outside temperature is 30°C, and the radiant energy varies depending on the temperature, but is 100W at 30°C. This calculation assumes that there is no absorption of sunlight in the infrared radiation layer J. Assuming no wind, the convective heat transfer coefficient is 5W / m ２ / K.

[0080] [Regarding Light Absorption of Hydrocarbon-Based Resins] When the resin materials (first resin, second resin) are resins whose main chain is a hydrocarbon having one or more carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, or benzene rings, absorption due to vibrations such as bond bending and stretching is observed in the near-infrared region in addition to the ultraviolet absorption due to the covalently bonded electrons described above.

[0081] Specifically, CH ３ , C.H. ２ The absorptions due to the fundamental tones of the transition to the first excited state of CH appear at wavelengths of 1.6 μm to 1.7 μm, 1.65 μm to 1.75 μm, and 1.7 μm, respectively. ３ , C.H. ２ The absorptions due to the reference tones of the CH combination tones appear at wavelengths of 1.35 μm, 1.38 μm, and 1.43 μm, respectively. ２ The overtones of the transition to the second excited state of CH appear at a wavelength of around 1.24 μm. The fundamental tones of the bending and stretching of the C-H bond are distributed over a wide band from 2 μm to 2.5 μm.

[0082] Furthermore, when the resin material has an ester bond (R-COO-R) or an ether bond (C-O-C), there is significant light absorption at a wavelength of around 1.9 μm. According to the light absorption relational expression described above, the light absorption rate due to these bonds becomes smaller and less noticeable when the resin material film thickness is thin, but becomes larger when the film thickness is thick.

[0083] Figure 9 shows the relationship between light absorptance and sunlight spectrum when the film thickness of ethylene terephthalate resin containing ester bonds and benzene rings is changed. As the film thickness increases from 25 μm to 125 μm to 500 μm, the absorption of light in the wavelength range longer than 1.5 μm, due to the respective vibrations, increases. Furthermore, light absorption increases not only on the long wavelength side but also from the ultraviolet region to the visible region. This is due to the broadening of the light absorption edge caused by chemical bonds.

[0084] When the film thickness is thin, the light absorptance is large at the wavelength with the largest absorption coefficient, but as the film thickness increases, a weak absorption coefficient at the broadened absorption edge appears as the absorptance according to the light absorptance relational expression described above. As a result, as the film thickness increases, light absorption increases from the ultraviolet region to the visible region. Regarding reflectance, if the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 400 nm to 800 nm, is 80% or more, and the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 800 nm to 1200 nm, is 43% or more, then if the absorbed energy of sunlight is 350 W / m and the wavelength average of the emissivity at wavelengths from 8 μm to 13 μm is 43% or more, then the solar energy is 350 W / m. ２ Absorption is 85W / m ２ Furthermore, if the emissivity is 43% or more, it can be suppressed to 200 W / m on a day with good atmospheric conditions. ２ For radiation of about 85W / m ２ In other words, it is preferable that the laminated resin layer including the light-reflecting layer and the infrared-emitting layer has an arithmetic mean reflectance, which is the wavelength average of light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is the wavelength average of light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of emissivity at wavelengths of 8 μm to 13 μm of 43% or more.

[0085] By making the light-reflecting layer B exhibit a reflectance of 80% or more from 400 nm to 800 nm and a reflectance of 70% or more from 800 nm to 1200 nm, the solar energy absorbed by the light-reflecting layer B in the radiative cooling device (radiative cooling film) can be reduced to 25% or less, i.e., the solar energy absorbed at noon in summer can be reduced to about 85 W. Furthermore, although the atmospheric window narrows when humidity is high, even if radiation falls to, for example, about 125 W / m2, an emissivity of 70% or more is desirable because it can emit more energy than solar energy.

[0086] As mentioned above, the maximum value of infrared radiation in the wavelength band of the atmospheric window in the summer in the lowlands of Japan is about 160 W at 30°C on a day with good atmospheric conditions, and usually about 125 W. If both the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B are ethylene terephthalate resin, a hydrocarbon-based resin, and each has a film thickness of 500 μm, the sum of the solar light absorption of the laminated resin layer M (both the infrared emitting layer J and the light reflecting layer B) is 176 W / m ２ As described above, when the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B are both ethylene terephthalate resin, a hydrocarbon-based resin, the film thickness of each of the infrared emitting layer J and the light reflecting layer B must be 500 μm or more, i.e., when the film thickness of the laminated resin layer M is 1000 μm or more, the radiative cooling performance is not exhibited. In other words, it is preferable that the thickness of the first resin of the infrared emitting layer J and the thickness of the second resin of the light reflecting layer B are each 500 μm or less. It is preferable that the thickness of the first resin of the infrared emitting layer J and the thickness of the second resin of the light reflecting layer B are 10 μm or more, and the lower limit of the film thickness is determined from the viewpoint of ensuring infrared emissivity and light reflectivity.

[0087] [Regarding the light absorption of blended resins] When the resin material (first resin, second resin) is a resin material obtained by blending a resin having a carbon-fluorine bond as the main chain with a resin having a hydrocarbon as the main chain, the light absorption of CH, CH ２ , C.H. ３ When carbon-fluorine bonds are the main component, the absorption of light in the near-infrared region due to hydrocarbons is small, so the thickness can be increased up to 20 mm, which is the upper limit from the viewpoint of thermal conductivity. However, when a blended hydrocarbon resin is the main component, the thickness of each of the first resin and the second resin must be 500 μm or less.

[0088] The blend of fluororesin and hydrocarbon also includes those in which the fluororesin is substituted with hydrocarbon, and alternating copolymers, random copolymers, block copolymers and graft copolymers of fluoromonomers and hydrocarbon monomers.

[0089] Depending on the molecular weight and proportion of the hydrocarbon side chain to be substituted, CH, CH ２ , C.H. ３ When the monomer introduced as a side chain or copolymer has a low molecular weight, or when the density of the introduced monomer is low, the absorption of light in the near-infrared region due to hydrocarbons is small, so the thickness can be increased up to 20 mm, which is the limit from the viewpoint of thermal conductivity. When a high molecular weight hydrocarbon is introduced as a side chain or copolymerized monomer of the fluororesin, the thickness of each of the first resin and the second resin must be 500 μm or less.

[0090] [Thickness of the infrared radiation layer] From the viewpoint of practical use of the resin laminate film CP, it is preferable that the thickness of the infrared radiation layer J is thin. The thermal conductivity of resin materials is generally lower than that of metals, glass, etc. In order to effectively cool an object to be cooled, it is preferable that the thickness of the infrared radiation layer J is kept to the minimum necessary. The thicker the thickness of the infrared radiation layer J, the greater the thermal radiation from the atmospheric window, and once a certain thickness is exceeded, the thermal radiation energy from the atmospheric window becomes saturated.

[0091] The thickness at which the film saturates depends on the resin material, but in the case of fluororesin, a thickness of roughly 300 μm is sufficient. Therefore, from the perspective of thermal conductivity, it is preferable to keep the film thickness below 300 μm rather than 500 μm. Furthermore, although thermal radiation does not saturate, sufficient thermal radiation can be obtained in the atmospheric window region even with a thickness of around 100 μm. Since a thinner film has a higher thermal conductivity and can more effectively lower the temperature of the object being cooled, a thickness of around 100 μm or less is preferable in the case of fluororesin.

[0092] The absorption coefficients resulting from carbon-silicon bonds, carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds are greater than the absorption coefficient resulting from C-F bonds. Naturally, from the perspective of thermal conductivity, it is desirable to keep the film thickness below 300 μm rather than 500 μm; however, further thinning the film to increase thermal conductivity can be expected to produce even greater radiative cooling effects. In the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, saturation occurs even at a thickness of 100 μm, and sufficient thermal radiation can be obtained in the atmospheric window region even at a thickness of 50 μm. The thinner the resin material, the higher the thermal transmittance and the more effectively the temperature of the object to be cooled can be lowered. Therefore, in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, a thickness of 50 μm or less reduces the thermal insulation and allows the object to be cooled to be cooled effectively. In the case of carbon-chlorine bonds, a thickness of 100 μm or less allows the object to be cooled to be cooled effectively.

[0093] The benefit of making the material thinner is not only that it reduces heat insulation and makes it easier to conduct heat. This is because resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds exhibit CH, CH in the near-infrared region. ２ , C.H. ３ This is due to the suppression of light absorption in the near-infrared region caused by the radiation. By making the film thinner, the solar absorption caused by these factors can be reduced, thereby increasing the cooling ability of the resin laminate film CP. From the above perspective, in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0094] In the case of carbon-silicon bonds, even a thickness of 50 μm fully saturates the thermal radiation in the atmospheric window region, and even a thickness of 10 μm provides sufficient thermal radiation in the atmospheric window region. The thinner the infrared radiation layer J, the higher the thermal transmittance and the more effectively the temperature of the object to be cooled can be lowered. Therefore, in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less reduces the heat insulating properties and allows the object to be cooled to be cooled more effectively. Thinner films can reduce solar absorption, thereby enhancing the cooling capacity of the resin laminate film CP. From the above perspectives, in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less can more effectively achieve the radiative cooling effect under sunlight.

[0095] As will be described later, in the resin laminate film CP according to this embodiment, a resin is also used for the light-reflecting layer B. Although the light-reflecting layer B contains voids K at a certain volumetric ratio, a certain amount of heat radiation can be expected. In consideration of this point, it is preferable to further reduce the thickness of the infrared radiation layer J described above.

[0096] [Details of the Light Reflecting Layer] The light reflecting layer B has the above-mentioned reflective characteristics (reflective characteristics of the laminated resin layer M) by differentiating the refractive index of the second resin forming the light reflecting layer from the refractive index of the material inside the multiple voids K contained in the second resin. Specifically, the second resin of the light reflecting layer B preferably contains at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate. Conversely, polyimide and bakelite are undesirable as the second resin of the light reflecting layer B because the resins themselves tend to be discolored and have low reflectance.

[0097] Furthermore, the pores K of the second resin of the light-reflecting layer B can contain various gases or fluids, but preferably contain air. The refractive index of the pores K (more specifically, the gas or fluid contained in the pores K) is smaller than that of the second resin. Furthermore, the arithmetic mean pore diameter of the pores K is preferably 0.1 μm or more and 3.0 μm or less. In this embodiment, the arithmetic mean pore diameter refers to the arithmetic mean of the smallest inner diameters of the pores K. The shape of the pores K can be various shapes, such as spherical or elliptical, but from the viewpoint of improving light reflectance, a flat shape is preferable, and more preferably, the major axis of the pores K is aligned in the direction along the film surface (radiation surface H) of the resin laminate film CP. Furthermore, the volume fraction of the pores K in the light-reflecting layer B is preferably 0.1 vol% or more and 60 vol% or less, more preferably 1 vol% or more and 50 vol% or less, and more preferably 10 vol% or more and 40 vol% or less.

[0098] Furthermore, as a result of intensive research by the inventors, the thickness of the second resin of the light-reflecting layer B is preferably 10 μm or more and 500 μm or less. By making the thickness of the second resin of the light-reflecting layer B 10 μm or more, the light-reflecting layer B made of the second resin having a plurality of pores K can satisfactorily ensure the reflectivity required for radiative cooling. In addition, by making the thickness 500 μm or less, the insulating effect of the second resin having pores K containing air or the like can be kept below a certain level, thereby ensuring a certain level of cooling performance for the object to be cooled. The thickness of the second resin of the light-reflecting layer B is preferably 50 to 300 μm, and more preferably 75 to 200 μm. If the thickness is 500 μm or more, the thermal conductivity in the thickness direction decreases and the insulating properties become stronger. Therefore, when applied to an enclosure with an internal heat source, the heat accumulation within the enclosure increases, which is undesirable from the perspective of thermal radiation.

[0099] As shown in Fig. 2 , the resin laminate film CP may contain a filler F (F1, F2) in the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B. The filler F (F1, F2) may be contained in at least one of the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B. The filler F (F1, F2) may be one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate. The filler F1 contained in the first resin and the filler F2 contained in the second resin may be different materials.

[0100] [Experimental Results] For the examples and comparative examples of the laminate resin films described above, various tests were conducted on antifouling properties, ultraviolet reflectance, reflectance at wavelengths of 400 nm to 800 nm, reflectance at wavelengths of 800 nm to 1200 nm, transmittance at wavelengths of 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic wave transmittance. The results are shown in Tables 1 to 4 below. In the test results shown in the tables, underlined portions indicate that the various test conditions were not met. Incidentally, Tables 1 to 4 also show various conditions for the films constituting the examples and comparative examples.

[0101] The stain resistance was evaluated by a one-month outdoor exposure test in Osaka City using the color difference ΔE before and after exposure, and a value of ΔE<2.0 was defined as high (good) stain resistance. The color difference ΔE refers to the "CIEDE2000 color difference" based on JIS Z8781.

[0102] The UV reflectance was evaluated using the arithmetic mean of the reflectance in the wavelength range of 340 nm to 400 nm measured using a UV-visible spectrometer UV-2600 (Shimadzu Corporation). A reflectance of 50% or less was defined as satisfying the condition (low UV reflectance).

[0103] The reflectance in the wavelength range of 400 nm to 800 nm was evaluated using the arithmetic mean of the reflectance in the wavelength range of 400 nm to 800 nm measured using an ultraviolet-visible spectrometer UV-2600 (Shimadzu Corporation). A reflectance of 80% or more was defined as satisfying the condition (high reflectance in the wavelength range of 400 nm to 800 nm).

[0104] The reflectance in the wavelength range of 800 nm to 1200 nm was evaluated using the arithmetic mean of the reflectance in the wavelength range of 800 nm to 1200 nm measured using an ultraviolet-visible spectrometer UV-2600 (Shimadzu Corporation). A reflectance of 70% or more was defined as satisfying the condition (high reflectance in the wavelength range of 800 nm to 1200 nm).

[0105] The transmittance in the wavelength range of 400 nm to 800 nm was evaluated using the arithmetic mean of the transmittance in the wavelength range of 400 nm to 800 nm measured using an ultraviolet-visible spectrometer UV-2600 (Shimadzu Corporation). A transmittance of 1% or more was defined as satisfying the condition (high transmittance in the wavelength range of 400 nm to 800 nm).

[0106] The infrared emissivity was evaluated using the arithmetic mean of the emissivity at wavelengths of 8 μm to 13 μm measured using an FT-IR IRTracer-100 (Shimadzu Corporation). A sample with an emissivity of 70% or higher was defined as satisfying the condition (high reflectivity at wavelengths of 400 nm to 800 nm).

[0107] The thermal conductivity was measured using the laser flash method defined in JIS R1611, and a thermal conductivity of 0.3 W / m·K or more was defined as having high (good) thermal conductivity.

[0108] Xenon weather resistance is measured in the xenon weather resistance test defined in JIS K5600, where the black panel temperature (BPT) is 63°C and the ultraviolet intensity is 180 W / m ２ The sample was exposed to ultraviolet light of 1000 W for 3000 hours, and the color difference ΔE of the sample before and after the test was measured. Samples with ΔE<2.0 were defined as having high (good) weather resistance.

[0109] The radio wave transmittance was measured at 800 MHz using the KEC method at the Kansai Electronics Industry Development Center (KEC) General Incorporated Association. An attenuation of 10 dB or less was defined as high (good) radio wave transmittance.

[0110] In the table, PET stands for polyethylene terephthalate, PEN stands for polyethylene naphthalate, PVC stands for polyvinyl chloride, PVDC stands for polyvinylidene chloride, PVDF stands for polyvinylidene fluoride (polyvinylidene fluoride), and PP stands for polypropylene.

[0111] For the preparation of the sample of Example 1, TiO ２ A thin film of vinyl chloride resin containing TiO was formed by a calendaring method. ２ The laminate was prepared by laminating a PET film containing the compound by dry lamination.

[0112]

[0113]

[0114]

[0115]

[0116] As shown by the above experimental results, the resin laminate films CP according to Examples 1 to 16 of the present invention satisfy the specified conditions in terms of antifouling properties, ultraviolet reflectance, reflectance at wavelengths of 400 nm to 800 nm, reflectance at wavelengths of 800 nm to 1200 nm, transmittance at wavelengths of 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic wave transmittance.

[0117] On the other hand, in Comparative Examples 1 to 4, a relatively large number of pores K are formed in the infrared radiation layer J as the surface layer, so the anti-fouling condition is not met and the layer is susceptible to dirt adhesion. In Comparative Examples 1 and 5, a second resin is not provided as the light-reflecting layer B, so the conditions for reflectance at wavelengths of 400 nm to 800 nm and reflectance at wavelengths of 800 nm to 1200 nm are not met, resulting in low reflectance. In Comparative Example 6, PET vapor-deposited with silver, a metal, is used as the light-reflecting layer B, so the transmittance condition at wavelengths of 400 nm to 800 nm is not met, resulting in poor light transmission and also in failure to meet the radio wave transmittance condition. Furthermore, in Comparative Examples 1 and 5, a second resin is not provided as the light-reflecting layer B, so it is believed that the infrared emissivity condition is not met, and it is inferred that the second resin as the light-reflecting layer B contributes to a certain degree to the infrared emissivity. It is presumed that Comparative Examples 2 and 4 do not satisfy the condition for infrared emissivity due to the provision of multiple pores K in the relatively thin 100 μm infrared radiation layer J. In Comparative Examples 3 and 4, the resin layer having pores K is thick, resulting in low thermal conductivity of the material as a whole, and therefore the condition for thermal conductivity is not satisfied. In Comparative Examples 1 to 5, the weather resistance of the PET against ultraviolet rays is insufficient, and yellowing occurs when xenon weather resistance is evaluated, so the condition for xenon weather resistance is not satisfied.

[0118] [Other Embodiments] (1) A configuration may be adopted in which the radiation surface H of the infrared radiation layer J is protected by a protective layer (not shown). Materials such as fluorine and acrylic fluorine can be suitably used for the protective layer, and the thickness thereof is preferably about 0.1 μm or more and 100 μm or less. Polyethylene or polypropylene, which has a low emissivity at the atmospheric window, may be used as the material. The protective layer has antifouling and anti-scratch functions and serves as a sacrificial layer.

[0119] (2) A connecting resin layer may be provided on the side of the reflective layer B opposite to the infrared radiation layer J. As an example, the connecting resin layer may be a connecting layer made of polyvinyl chloride, which allows for suitable connection to a vinyl chloride film material, tarpaulin, or steel plate. Specific configuration examples for connecting the resin laminate film CPCP to other materials using a connecting resin layer are shown below.

[0120] One possible application is combining it with a membrane material. By connecting a general membrane material and a resin laminate film CP with a connecting resin layer, a membrane material with cooling properties can be produced. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, or vinylidene chloride can be suitably used as the connecting resin layer of the resin laminate film CP. A membrane material with this resin laminate film CP can be sewn or heat-sealed, making it suitable for use in buildings, tents, sunshade covers, truck tarpaulins, and more.

[0121] One possible application is a combination with a resin waterproof sheet. A resin waterproof sheet with cooling properties can be produced by connecting a typical resin waterproof sheet (e.g., New Best Proof, manufactured by Lonseal Corporation) and a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, or vinylidene chloride can be suitably used as the connecting resin layer of the resin laminate film CP. A resin waterproof sheet with this resin laminate film CP can be thermally welded, making it suitable for use in waterproofing the rooftops of buildings.

[0122] One possible application is combining it with an asphalt waterproofing sheet. By connecting a typical asphalt waterproofing sheet and a resin laminate film CP with a connecting resin layer, an asphalt waterproofing sheet with cooling properties can be produced. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When using a resin laminate film CP without a connecting resin layer, the asphalt waterproofing sheet and the resin laminate film CP can be directly connected by melting at least one of the asphalt waterproofing sheet and the resin laminate film CP with heat. Such an asphalt waterproofing sheet with a resin laminate film CP can be attached to building materials such as metal roofs, concrete roofs, and slate roofs, and can be used to cool buildings.

[0123] One possible application is a combination with clothing fabric. By connecting a typical clothing fabric and a resin laminate film CP with a connecting resin layer, a clothing fabric with cooling properties can be produced. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the clothing fabric and the resin laminate film CP may be directly connected by melting at least one of the clothing fabric and the resin laminate film CP with heat. Creating and using clothing with the resin laminate film CP can be expected to improve the sensation of heat outdoors and prevent heatstroke.

[0124] One possible application is a combination with a magnet sheet. A magnet sheet with cooling performance can be produced by connecting a general magnet sheet and a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the magnet sheet and the resin laminate film CP may be directly connected by melting the resin laminate film CP with heat. By applying such a magnet sheet with a resin laminate film CP to a metal surface exposed to outdoor sunlight (e.g., a metal housing), it can be used to cool the surface.

[0125] One possible application is a combination with a metal plate. A metal plate with cooling performance can be produced by connecting a general metal plate (such as a stainless steel or aluminum alloy plate) to a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the metal plate and the resin laminate film CP can be directly connected by melting the resin laminate film CP with heat. By processing a metal plate with such a resin laminate film CP to produce a metal roof or metal wall and applying it to a building, a building with a high cooling effect can be realized.

[0126] One possible application is a combination with a slate board. A slate board with cooling properties can be produced by connecting a typical slate board and a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the slate board and the resin laminate film CP may be directly connected by melting the resin laminate film CP with heat. By processing a slate board with such a resin laminate film CP to produce a slate roof or slate wall and applying it to a building, a building with a high cooling effect can be realized.

[0127] One possible application is a combination with roofing tiles. By connecting a general roofing tile and the resin laminate film CP with a connecting resin layer, a roofing tile with cooling properties can be produced. In this case, resins such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, and polyester can be suitably used as the connecting resin layer of the resin laminate film CP. By applying such roofing tiles with the resin laminate film CP to a building, a building with a high cooling effect can be realized.

[0128] One possible application is a combination with a concrete plate. A concrete plate with cooling properties can be produced by connecting a general concrete plate and the resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. By processing such a concrete plate with the resin laminate film CP to produce a concrete roof or concrete wall and applying it to a building, a building with a high cooling effect can be realized.

[0129] One possible application is a combination with a siding board. A siding board with cooling properties can be produced by connecting a typical siding board and a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the siding board and the resin laminate film CP may be directly connected by melting the resin laminate film CP with heat. By processing a siding board with such a resin laminate film CP to create a wall and applying it to a building, a building with a high cooling effect can be realized.

[0130] One possible application is a combination with a resin plate. A resin plate with cooling performance can be produced by connecting a general resin plate and a resin laminate film CP with a connecting resin layer. In this case, an adhesive layer made of a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or polyester can be suitably used as the connecting resin layer of the resin laminate film CP. When a resin laminate film CP without a connecting resin layer is used, the resin plate and the resin laminate film CP may be directly connected by melting at least one of the resin plate or the resin laminate film CP with heat. By processing a resin plate with such a resin laminate film CP to produce a housing, a housing with high cooling performance can be realized outdoors.

[0131] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention.

[0132] The resin laminate film of the present invention can be effectively used as a resin laminate film that can exhibit high cooling capacity under direct sunlight and high radio wave transmittance, and can prevent a decrease in radiative cooling performance when holes are provided in the resin material and a decrease in cooling performance due to contamination of the holes.

[0133] B: Light-reflecting layer CP: Resin laminated film F: Filler H: Radiation surface IR: Infrared light J: Infrared radiation layer K: Hole M: ​​Laminated resin layer S: Connection layer

Claims

1. A resin laminate film comprising an infrared radiation layer that emits infrared light from its radiation surface, and a light-reflecting layer located on the side of the infrared radiation layer opposite to the side where the radiation surface is present, wherein the light-reflecting layer has a plurality of voids and is made of a second resin, the infrared radiation layer is made of a first resin that emits thermal radiation energy at wavelengths of 8 μm to 13 μm that is greater than the solar light energy it absorbs, the number of voids contained in the infrared radiation layer is fewer than the number of voids contained in the light-reflecting layer, and the laminate resin layer including the light-reflecting layer and the infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and the wavelength average of the emissivity at wavelengths of 8 μm to 13 μm is 43% or more.

2. The resin laminate film according to claim 1, wherein the infrared radiation layer contains a filler in the first resin.

3. A resin laminate film according to claim 1 or 2, wherein the thickness of the second resin is 10 μm or more and 500 μm or less.

4. A resin laminate film according to claim 1 or 2, wherein the thickness of the first resin is 10 μm or more and 500 μm or less.

5. A resin laminate film according to claim 1 or 2, wherein the pores in the second resin have a refractive index smaller than that of the second resin, and the arithmetic mean pore diameter of the pores is 0.1 μm or more and 3.0 μm or less.

6. The resin laminate film according to claim 1 or 2, wherein the volume ratio of the voids in the light reflecting layer is 0.1% by volume or more and 60% by volume or less.

7. The resin laminate film according to claim 1 or 2, wherein the volume ratio of the voids in the resin laminate layer is 1% by volume or more and 50% by volume or less.

8. The resin laminate film according to claim 1 or 2, wherein the volume ratio of the voids in the resin laminate layer is 10% by volume or more and 40% by volume or less.

9. A resin laminate film according to claim 1 or 2, wherein the laminate resin layer has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light having a wavelength of 400 nm to 800 nm, of 88% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light having a wavelength of 800 nm to 1200 nm, of 80% or more.

10. A resin laminate film according to claim 1 or 2, wherein the laminate resin layer has an arithmetic mean transmittance, which is the wavelength average of the light transmittance in the wavelength range of 400 nm to 800 nm, of 1% or more and 12% or less.

11. The resin laminate film according to claim 1 or 2, wherein the laminate resin layer has an average wavelength emissivity of 70% or more in the wavelength range of 8 μm to 13 μm.

12. The resin laminate film according to claim 1 or 2, wherein the second resin contains a filler.

13. The resin laminate film according to claim 2, wherein the filler is one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate.

14. The resin laminate film according to claim 12, wherein the filler is one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate.

15. A resin laminate film according to claim 1 or 2, wherein the second resin comprises at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate.

16. A resin laminate film according to claim 1 or 2, wherein the first resin contains at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate.

17. A resin laminate film according to claim 1 or 2, wherein the first resin contains at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

18. A resin laminate film according to claim 1 or 2, wherein the first resin contains an ultraviolet absorber, and the infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the ultraviolet reflectance in the wavelength range of 340 nm to 400 nm, of 50% or less.

19. A resin laminate film according to claim 1 or 2, wherein the light-reflecting layer and the infrared-emitting layer are connected by a connecting layer made of at least one of an adhesive, a pressure-sensitive adhesive, and a glue, and the connecting layer is included in the laminate resin layer.

20. The resin laminate film according to claim 19, wherein the connection layer contains at least one of a filler and hollow particles.

21. A resin laminate film according to claim 1 or 2, wherein the pores in the second resin have a flat shape.

22. The resin laminate film according to claim 1 or 2, further comprising a connecting resin layer on the side of said light reflecting layer opposite to said infrared emitting layer.

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