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

DESCRIPTION RESIN LAMINATED FILM Technical Field

[0001] The present invention relates to a resin laminated film including: an infrared radiative layer that radiates infrared light from a radiative surface; and a light reflective layer that is located on the infrared radiative layer on a side opposite to the radiative surface. Background Art

[0002] As a conventional example of a composite cooling material using a radiative-cooling phenomenon, there is a material in which an infrared radiative layer that radiates infrared light from a radiative surface and a light reflective layer that is located on the infrared radiative layer on a side opposite to the radiative surface are laminated (see Patent Document 1, for example). In order to reject heat to outer space by the radiative-cooling phenomenon and cool an object under direct sunlight, it is important to achieve both a high solar reflectance and a high infrared emissivity. Prior Art DocumentPatent Document

[0003] Patent Document 1: JP 2018-526599T Patent Document 2: JP 2022-528289T Patent Document 3: WO 2018 / 062541 Disclosure of the InventionProblem to be Solved by the Invention

[0004] Conventional radiative-cooling materials have achieved a high solar reflectance by reflecting sunlight with a thin metal film. However, the use of a thin metal film involves a problem that absorptance increases, which has been a factor causing the material temperature to increase under direct sunlight. In addition, the use of a thin metal film also involves a problem that radio-wave transmissivity decreases, and thus communication equipment tends not to operate properly in a space enclosed by the thin metal film. Further, if a thin metal film is used as a reflective layer, when the surface is scratched and the metal layer is exposed, corrosion starts from the metal layer, oxidation of the metal layer causes coloration of the metal layer, and reflectance tends to decrease easily. Moreover, if a thin metal film is used as the reflective layer, since even a very small amount of a metal oxide tends to cause coloration, the degree of decrease in reflectance upon deterioration is large compared with a reflective layer made of resin.

[0005] There also exists a radiative-cooling material that increases solar reflectance by making a resin porous (see Patent Document 2). In such a radiative-cooling material, if the porous structure is exposed at the outermost surface, it is easily soiled by rainwater and the like. If the outermost surface of the radiative-cooling material is soiled, even when the soil absorbs sunlight, the radiative-cooling material itself does not warm because thermal contact between the soil and the radiative-cooling material is small. However, if the inside of the porous structure is soiled, the heat converted from sunlight has no place to escape due to the soil and thus heats the material significantly. Accordingly, radiative-cooling materials with a porous structure exposed at the surface are avoided from the viewpoint of soiling.

[0006] There also exists a radiative-cooling material that utilizes the porous structure itself as a radiation layer (see Patent Document 3). Such a radiative-cooling material makes it difficult to maximize the radiative-cooling capability in the atmospheric-window region. Various materials can be made porous, such as polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, and the like. However, if the resin is made porous, the amount of substance contributing to radiation decreases, and thus it is necessary to increase thickness to obtain high radiative-cooling capability. Radiative-cooling materials are designed to be attached to a target for cooling the target, and an increase in resin layers, particularly porous resin layers, impairs the capability of the radiative-cooling material. From this viewpoint, a design in which the porous resin layer itself is caused to radiate hinders cooling of the target.

[0007] In addition, if radiative capability is improved by porosity, a problem arises that the temperature of a cooling target is not transferred to the resin located at the outermost surface due to poor thermal conductivity attributable to porosity, and the cooling target cannot be cooled sufficiently. Further, in a porous resin layer in which layers containing air are stacked in multiple layers in a mille-feuille-like manner, emissivity tends to decrease in the case in which the layer is made multilayer as compared with the case in which it is not made multilayer. This is because a photonic band-gap structure is formed due to an optical multilayer film structure, and reflectance is improved. For this reason, utilization of a porous resin layer not only as a reflective layer but also as a radiation layer is not preferable for improving the cooling structure of a radiative-cooling material.

[0008] It is an object of the present invention to provide a resin laminated film that can exhibit high cooling capability under direct sunlight and also exhibit high radio-wave transmissivity, and that can, if voids are provided in a resin material, prevent a decrease in radiative-cooling performance and a decrease in cooling performance that is caused by soiling of the voids. Means for Solving Problem

[0009] In order to achieve the above-described object, a characteristic configuration of a resin laminated film according to the present invention is directed to a resin laminated film including: an infrared radiative layer that radiates infrared light from a radiative surface; and a light reflective layer that is located on the infrared radiative layer on a side opposite to the radiative surface, the light reflective layer having a plurality of voids and being made of a second resin, the infrared radiative layer being made of a first resin that radiates, in a wavelength range from 8 μm to 13 μm, heat radiation energy greater than absorbed solar energy, the infrared radiative layer having fewer voids than the light reflective layer, and a laminated resin layer, constituted by the light reflective layer and the infrared radiative layer, having an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and having a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 43% or more.

[0010] According to the above characteristic configuration, first, since a thin metal film is not used as the light reflective layer, compared with a configuration using a thin metal film as the light reflective layer, the absorptance of sunlight can be suppressed and an increase in the temperature of the resin laminated film can be suppressed. Further, since radio-wave transmissivity can be made relatively high, even in a situation where the resin material film having the above characteristic configuration surrounds wireless communication equipment, communication by the wireless communication equipment can be kept favorable. Further, since a configuration is adopted in which the infrared radiative layer typically installed with the radiative surface facing the atmosphere has fewer voids than the light reflective layer, more preferably the infrared radiative layer has substantially no voids, the infrared radiative layer is less likely to be soiled by rainwater and the like, and it is possible to favorably prevent the soil from absorbing sunlight and heating the infrared radiative layer.

[0011] In addition, since a configuration is adopted in which the infrared radiative layer has substantially no voids, a sufficient volume fraction of the first resin material contributing to radiation can be ensured in the radiative-cooling layer, and sufficient radiative-cooling capability can be ensured. Further, thermal conductivity can be improved, so that heat of the cooling target is easily transferred to the radiative surface, and an improvement in cooling effect can be expected. Moreover, since a configuration can be realized in which a photonic band-gap structure is not substantially formed inside the first resin layer constituting the infrared radiative layer, emissivity of the infrared radiative layer can be improved.

[0012] In addition to the configurations described above, the inventors of the present invention have confirmed through tests described later that, if the light reflective layer is made of a second resin having a plurality of voids, a resin laminated film can be realized in which a laminated resin layer, constituted by the light reflective layer and the infrared radiative layer, has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 43% or more.

[0013] As described above, in a laminated resin layer that has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, the light reflective layer has a solar energy absorptance of only about 2% partly because no metal is contained. As a result, at solar noon in summer, solar energy absorbed by the light reflective layer can be made approximately 20 W / m2 or less, and radiative cooling can be executed even more favorably.

[0014] Thus, it is possible to realize a resin laminated film that can exhibit high cooling capability under direct sunlight and also exhibit high radio-wave transmissivity, and that can, if voids are provided in a resin material, prevent a decrease in radiative-cooling performance and a decrease in cooling performance that is caused by soiling of the voids.

[0015] In another characteristic configuration of the resin laminated film, the first resin of the infrared radiative layer contains a filler.

[0016] As described above, the infrared radiative layer typically installed with the radiative surface facing the atmosphere is constituted by a first resin layer having no voids, thereby improving soiling resistance, radiative-cooling capability, heat transferability in a direction intersecting the radiative surface, and the like. However, as in the above characteristic configuration, since the first resin contains a filler, light reflective performance at or above a certain level can be exhibited in the infrared radiative layer as well, due to a difference in refractive index between the first resin layer and the filler. Thereby, in addition to solar reflection by the light reflective layer, solar reflection can also be provided by the infrared radiative layer, and the reflectance of the entire material can be maintained high.

[0017] In another characteristic configuration of the resin laminated film, the second resin has a thickness of 10 μm or more and 500 μm or less.

[0018] As in the above characteristic configuration, if the thickness of the second resin of the light reflective layer is set to 10 μm or more, reflectance required for radiative cooling can be favorably ensured by the light reflective layer made of the second resin having a plurality of voids. In addition, if the thickness is set to 500 μm or less, the heat-insulating effect by the second resin having voids including air and the like can be limited to a certain level or less, and cooling performance of the cooling target can be ensured at or above a certain level. Incidentally, a thickness of 500 μm or more is undesirable because, from the viewpoint of rigidity, it becomes difficult to make the material follow a curved portion in the case of applying the material to the curved portion, or the material may be broken if forced to follow. Also, in roll-to-roll processing, if the thickness is too large, the quantity of material that can be produced in one run decreases, which is undesirable. That is, if an appropriate material is selected as the second resin having a plurality of voids and a light reflective layer in which the thickness of the second resin is set to 10 μm or more and 500 μm or less is provided together with the infrared radiative layer, a function can be exhibited that makes an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm to 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm to 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance. The thickness of the light reflective layer is preferably 50 to 300 um, and more preferably 75 to 200 um.

[0019] In another characteristic configuration of the resin laminated film, the first resin has a thickness of 10 μm or more and 500 μm or less. In particular, according to the resin laminated film of the present invention, since the first resin of the infrared radiative layer does not have a plurality of voids and can therefore exhibit higher radiation performance than an infrared radiative layer having voids, required radiation performance can be favorably ensured even with a relatively thin film layer having a film thickness of 500 μm. Incidentally, a thickness of 500 μm or more is undesirable because, from the viewpoint of rigidity, it becomes difficult to make the material follow a curved portion in the case of applying the material to the curved portion, or the material may be broken if forced to follow. Also, in roll-to-roll processing, if the thickness is too large, the quantity of material that can be produced in one run decreases, which is undesirable. Also, if the thickness is 10 μm or more, emissivity can be sufficiently ensured, and even in the case in which unevenness attributable to a plurality of voids in the second resin exists on the surface of the light reflective layer, the uneven shape is less likely to be reflected on the radiative surface of the infrared radiative layer, whereby adhesion of soil to the radiative surface can be favorably suppressed.

[0020] In another characteristic configuration of the resin laminated film, the voids in the second resin have a refractive index smaller than that of the second resin, and the voids have an arithmetic mean pore diameter of 0.1 μm or more and 3.0 μm or less.

[0021] As in the above characteristic configuration, it is preferable that the voids in the second resin of the light reflective layer have a refractive index smaller than that of the second resin, and have an arithmetic mean pore diameter of 0.1 μm or more and 3.0 μm or less. The inventors of the present invention have confirmed that good light reflectance can be realized in a wavelength range from 400 nm to 800 nm and in a wavelength range from 800 nm to 1200 nm when the arithmetic mean pore diameter of voids is set to a plurality of arithmetic mean pore diameters within the range of 0.1 μm or more and 3.0 μm or less. In the present invention, the arithmetic mean pore diameter of the voids means an arithmetic mean of the shortest inner diameters of the voids. The shape is not limited to a spherical shape and may be a flat structure having a short axis and a long axis, a polyhedral structure, or the like.

[0022] In another characteristic configuration of the resin laminated film, the voids in the light reflective layer have a volume fraction of 0.1 vol% or more and 60 vol% or less.

[0023] The inventors of the present invention have confirmed that, as described above, reflectance by the light reflective layer can be set to the above arithmetic mean reflectance by setting the volume fraction of the voids in the light reflective layer. More preferably, the voids in the light reflective layer have a volume fraction of 1 vol% or more and 50 vol% or less, and the voids in the light reflective layer have a volume fraction of 10 vol% or more and 40 vol% or less. If voids of 60 vol% or more are provided, thermal conductivity decreases, and thus in a system having a heat source inside, heat is stored and this is undesirable from the viewpoint of heat dissipation. Also, if voids of 60 vol% or more are provided, there arises a problem that strength decreases. On the other hand, if the volume fraction of the voids is less than 0.1 vol%, it is difficult to sufficiently improve reflectance even if the average particle diameter of the voids or their arrangement is devised.

[0024] Further, it is preferable that the laminated resin layer has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 84% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 75% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and it is more preferable that the laminated resin layer has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 88% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 80% or more.

[0025] In another characteristic configuration of the resin laminated film, the laminated resin layer has an arithmetic mean transmittance in a wavelength range from 400 nm to 800 nm of 1% or more and 12% or less, the arithmetic mean transmittance being a wavelength-averaged light transmittance.

[0026] According to the present invention, since the arithmetic mean transmittance in a wavelength range from 400 nm to 800 nm is set to 1% or more and 12% or less, the arithmetic mean transmittance being a wavelength-averaged light transmittance, light in the wavelength range of 400 nm to 800 nm is allowed to favorably transmit through both the first resin of the infrared radiative layer and the second resin of the light reflective layer, and light is reflected at the boundary between the second resin of the light reflective layer and the voids, thereby favorably improving reflectance in the laminated resin layer. In other words, the absorptance in the laminated resin layer can be reduced. In addition, a light transmittance of 1% or more is also good in that daylighting performance can be ensured during outdoor use.

[0027] Further, it is preferable that the laminated resin layer has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 70% or more, and it is more preferable that the laminated resin layer has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 85% or more.

[0028] In another characteristic configuration of the resin laminated film, the second resin contains a filler.

[0029] As in the above characteristic configuration, if the second resin forming the light reflective layer contains a filler in addition to the plurality of voids described above, 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, even in the case in which the volume fraction of the voids relative to the second resin is made relatively low or thickness of the layer is made thin in order to ensure thermal conductivity at or above a certain level, the arithmetic mean reflectance can be maintained high.

[0030] In another characteristic configuration of the resin laminated film, the filler is any 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. These materials may be porous.

[0031] Since the first resin forming the infrared radiative layer or the second resin forming the light reflective layer contains the above filler, good light reflectance can be realized in the entire laminated resin layer. In particular, the inventors of the present invention have confirmed that, if any 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 sufficiently high arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm and in a wavelength range from 800 nm to 1200 nm, the arithmetic mean reflectance being a wavelength-averaged light reflectance, to appropriately exert a radiative-cooling function.

[0032] Further, it is preferable that the second resin of the light reflective layer contains at least any one or more of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate, and it is more preferable that the first resin forming the infrared radiative layer contains at least any one or more of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate.

[0033] As will be described in detail later, as shown in FIG. 3, a resin having a carbon-fluorine bond (C-F) has absorption coefficients attributable to CHF and CF2 over a broad wavelength range from 8 μm to 13 μm, which is the atmospheric window, and particularly has a large absorption coefficient at 8.6 μm. In addition, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient in a wavelength range from 0.3 μm to 2.5 μm where energy intensity is large.

[0034] As for the resin having a carbon-chlorine bond (C-Cl), an absorption coefficient for stretching vibration of C-Cl appears around a wavelength of 12 μm over a wide range with a half width of 1 μm or more. In the case of a vinyl chloride resin, due to electron-withdrawing of chlorine, an absorption coefficient for bending vibration of C-H of an alkene contained in the main chain appears around wavelength 10 μm. The inventors of the present invention select the above material of the first resin also in consideration of these absorption-related characteristics.

[0035] It is preferable that the first resin contains at least any one or more of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

[0036] In particular, regarding the wavelength at which an absorption coefficient occurs in the ultraviolet to visible region of a resin material having a carbon-fluorine bond (C-F), bond energies of C-C, C-H, and C-F bonds of a basic structural unit, with polyvinylidene fluoride (PVDF) as a representative, are 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 light of these wavelengths is absorbed. Therefore, from the viewpoint of absorbing ultraviolet rays in the first resin of the infrared radiative layer and reducing the amount of ultraviolet rays transmitting through the light reflective layer, it is preferable to adopt polyvinyl fluoride or polyvinylidene fluoride as the first resin.

[0037] In another characteristic configuration of the resin laminated film, the first resin contains an ultraviolet absorber, and the infrared radiative layer has an arithmetic mean reflectance in a wavelength range from 340 nm to 400 nm of 50% or less, the arithmetic mean reflectance being a wavelength-averaged ultraviolet reflectance.

[0038] According to the above characteristic configuration, since the first resin forming the infrared radiative layer contains an ultraviolet absorber, and the infrared radiative layer has an arithmetic mean reflectance in a wavelength range from 340 nm to 400 nm of 50% or less, the arithmetic mean reflectance being a wavelength-averaged ultraviolet reflectance, ultraviolet rays can be suitably absorbed by the ultraviolet absorber, ultraviolet rays can be made difficult to reflect, the amount of ultraviolet rays transmitting through the first resin layer and the second resin layer can be reduced, and deterioration of the first resin layer and the second resin layer due to ultraviolet rays can be favorably suppressed.

[0039] In another characteristic configuration of the resin laminated film, the light reflective layer and the infrared radiative layer are bonded to each other via a bonding layer made of at least any one or more of an adhesive, a pressure-sensitive adhesive, and a glue, and the bonding layer is included in the laminated resin layer, and the bonding layer contains at least one of a filler and hollow particles.

[0040] In particular, if the bonding layer contains a filler or hollow particles, for example, having an arithmetic mean particle diameter of about 0.1 μm or more and 5 um or less as described above, the reflectance of light in the ultraviolet to visible region can be improved, and the thickness of the laminated resin layer (particularly, the light reflective layer) required to obtain a desired reflectance can be reduced.

[0041] In another characteristic configuration of the resin laminated film, the voids in the second resin have a flat shape.

[0042] According to the above characteristic configuration, since layers having different refractive indices can be provided in multiple layers, light reflection is more likely to occur as compared with a case where the thickness is the same and the voids have a non-flat structure, and reflectance can be more easily increased even with the same thickness, which is advantageous.

[0043] The resin laminated film described above may include a bonding resin layer that is located on the light reflective layer on the side opposite to the infrared radiative layer. Thereby, since the resin laminated film can be suitably adhered to another material that is a bonding target, a cooling effect for various materials can be favorably exerted. Brief Description of the Drawings

[0044] FIG. 1 is a diagram illustrating an embodiment of a resin laminated film. FIG. 2 is a diagram illustrating another embodiment of the resin laminated film. FIG. 3 is a diagram showing a relationship between absorption coefficients and wavelength bands of resin materials. FIG. 4 is a diagram showing a relationship between light absorptance and wavelength of resin materials. FIG. 5 is a diagram showing an emissivity spectrum of a vinyl chloride resin. FIG. 6 is a diagram showing an emissivity spectrum of a vinylidene chloride resin. FIG. 7 is a diagram showing an emissivity spectrum of an ethylene terephthalate resin. FIG. 8 is a diagram showing a relationship between the temperature of a radiative surface and the temperature of a light reflective layer. FIG. 9 is a diagram showing a light-absorptance spectrum of an ethylene terephthalate resin. Best Mode for Carrying Out the Invention

[0045] Hereinafter, embodiments of the present invention will be described with reference to the drawings.[Basic Configuration of Resin Laminated Film] As shown in FIG. 1, a resin laminated film CP includes an infrared radiative layer J that radiates infrared light IR from a radiative surface H, and a light reflective layer B that is located on the infrared radiative layer J on the side opposite to the radiative surface H. The resin laminated film CP is in the form of a film obtained by stacking the infrared radiative layer J and the light reflective layer B on one another. That is, the resin laminated film CP is configured as a radiative-cooling film.

[0046] The light reflective layer B has a plurality of voids K and is made of a second resin. The infrared radiative layer J is made of a first resin that radiates, in a wavelength range from 8 μm to 13 μm, heat radiation energy greater than absorbed solar energy. The infrared radiative layer J has fewer voids K than the light reflective layer B, and the infrared radiative layer J is a layer that substantially does not have voids K.

[0047] Further, a laminated resin layer M, constituted by the light reflective layer B and the infrared radiative layer J, has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 43% or more. In this specification, the laminated resin layer M is a concept that also includes a bonding layer S that bonds the light reflective layer B to the infrared radiative layer J.

[0048] More preferably, the laminated resin layer M has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 84% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 75% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and more preferably, the laminated resin layer M has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 88% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 80% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance. Also, the laminated resin layer M has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of more preferably 70% or more, and even more preferably 85% or more. Incidentally, if the infrared radiative layer J, the bonding layer S, and the light reflective layer B are selected such that a refractive-index difference between them increases, reflectance can be improved. As one example, polyvinylidene chloride containing TiO2 can be used for the infrared radiative layer, an acrylic adhesive can be used for the bonding layer S, and PET containing a plurality of voids can be used for the light reflective layer B.

[0049] With this characteristic configuration, solar energy absorbed by the laminated resin layer M can be suppressed to 2% or less, and the solar energy absorbed at solar noon in summer in Japan can be suppressed to about 20 W / m2.

[0050] In this embodiment, light L encompasses ultraviolet light, visible light, and infrared light. When these are described in terms of the wavelength of light, which is electromagnetic waves, the light L encompasses electromagnetic waves having wavelengths of 10 nm to 20000 nm (electromagnetic waves having wavelengths of 0.01 μm to 20 μm). The sunlight spectrum includes wavelengths ranging from 300 nm to 4000 nm, and its intensity increases as wavelength increases from 400 nm, and is particularly large in a wavelength range from 500 nm to 1800 nm.

[0051] In this embodiment, the laminated resin layer M is configured to have an arithmetic mean transmittance in a wavelength range from 400 nm to 800 nm of 1% or more and 12% or less, the arithmetic mean transmittance being a wavelength-averaged light transmittance.

[0052] Accordingly, the resin laminated film CP is configured such that the radiative surface H of the infrared radiative layer J reflects a portion of light L incident on the resin laminated film CP and the light reflective layer B reflects a portion of light L (e.g., sunlight) incident on the resin laminated film CP and transmitted through the infrared radiative layer J so that the reflected light goes out from the radiative surface H.

[0053] The resin laminated film CP is also configured such that heat input from a cooling target (not shown) that is located on the light reflective layer B on the side opposite to the infrared radiative layer J to the resin laminated film CP (e.g., heat input from the cooling target through heat conduction) is converted to infrared light IR and radiated by the infrared radiative layer J, thereby cooling the cooling target.

[0054] That is, the resin laminated film CP is configured to reflect light L emitted toward the resin laminated film CP and radiate heat conducted to the resin laminated film CP (e.g., heat conducted from the atmosphere or from the cooling target) as infrared light IR to the outside. Also, the resin laminated film CP (radiative cooling film) is configured to be flexible due to the infrared radiative layer J and the light reflective layer B being flexible.

[0055] The light reflective layer B and the infrared radiative layer J are bonded to each other via a bonding layer S made of at least any one or more of an adhesive, a pressure-sensitive adhesive, and a glue. The bonding layer S, although not shown, contains at least one of a filler and hollow particles, and thus the reflectance of light in the ultraviolet to visible region can be improved, and the thickness of the laminated resin layer M (particularly, the light reflective layer) required to obtain a desired reflectance can be reduced. Here, as the filler or hollow particles, those having an arithmetic mean particle diameter of about 0.1 μm or more and 5 um or less can be suitably used, and as the filler, particulate materials including any 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 can be suitably used. Thereby, the reflectance of light in the ultraviolet to visible region can be improved, and the thickness of the laminated resin layer M (particularly, the light reflective layer B) required to obtain a desired reflectance can be reduced.

[0056] In addition, the resin laminated film CP is used to implement a radiative-cooling method of emitting infrared light IR from the radiative surface H of the infrared radiative layer J on the side opposite to the surface in contact with the light reflective layer B. Specifically, the radiative surface H is directed toward the sky, and a radiative-cooling method is performed in which infrared light IR is emitted from the radiative surface H directed toward the sky.

[0057] [Infrared Radiative Layer] It is preferable that the first resin forming the infrared radiative layer J contains an ultraviolet absorber, and the infrared radiative layer J has an arithmetic mean reflectance in a wavelength range from 340 nm to 400 nm of 50% or less, the arithmetic mean reflectance being a wavelength-averaged ultraviolet reflectance. Preferred 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, oxanilide-based ultraviolet absorbers, and the like, and in particular, benzotriazole-based ultraviolet absorbers, triazine-based ultraviolet absorbers, and hindered amine-based stabilizers are particularly preferable because they can absorb up to the long-wavelength side of ultraviolet rays. The first resin preferably contains at least any one or more of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate, and more preferably contains at least any one or more of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

[0058] As the first resin forming the infrared radiative layer J, a colorless resin material including 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. FIG. 3 shows the wavelength region having an absorption coefficient in the wavelength band of the atmospheric window, for each resin material (excluding carbon-oxygen bonds).

[0059] According to Kirchhoff’s law, the emissivity (ε) is equal to the light absorptance (A). The light absorptance can be obtained from the absorption coefficient (α) by the relational expression A = 1 − exp(−αt) (hereinafter referred to as an absorptance equation). Here, t is the film thickness. That is, large heat radiation can be obtained in wavelength bands having a large absorption coefficient by adjusting the film thickness of the infrared radiative layer J. In a case where radiative cooling is performed outdoors, it is preferable to use a material having a large absorption coefficient in a wavelength range from 8 μm to 13 μm, which is the wavelength band of the atmospheric window. Also, in order to suppress absorption of sunlight, it is preferable to use a material that has no absorption coefficient or has a small absorption coefficient in a wavelength range from 0.3 μm to 4 μm, in particular from 0.4 μm to 2.5 μm. As can be understood from the relationship expression between absorption coefficient and absorptance, light absorptance (emissivity) varies depending on film thickness of the resin material.

[0060] In order to lower temperature below ambient atmosphere by radiative cooling under solar radiation, if a material having a large absorption coefficient in the wavelength band of the atmospheric window and having almost no absorption coefficient in the wavelength band of sunlight is selected, it is possible to create a state in which sunlight is hardly absorbed by adjusting the film thickness, but a large amount of heat radiation in the atmospheric window is emitted, that is, the output by radiative cooling becomes greater than the input by sunlight.

[0061] A carbon-fluorine bond (C-F) has absorption coefficients attributable to CHF and CF2 over a broad wavelength range from 8 μm to 13 μm, which is the atmospheric window, and particularly has a large absorption coefficient at 8.6 μm. In addition, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient in a wavelength range from 0.3 μm to 2.5 μm where energy intensity is large.

[0062] Examples of a resin material having a carbon-fluorine bond (C-F) include polyvinylidene fluoride (PVDF), which is a partially fluorinated resin. Hereinafter, polyvinylidene fluoride may be described as a vinylidene fluoride resin, but both refer to the same material. The same applies to other resins.

[0063] As for a carbon-chlorine bond (C-Cl), an absorption coefficient for stretching vibration of C-Cl appears around a wavelength of 12 μm over a wide range with a half width of 1 μm or more. Examples of such resin materials include polyvinyl chloride (PVC) and a vinylidene chloride resin (PVDC). In the case of a vinyl chloride resin, due to electron-withdrawing of chlorine, an absorption coefficient for bending vibration of C-H of an alkene contained in the main chain appears around a wavelength of 10 μm.

[0064] An ester bond (R-COO-R) and an ether bond (C-O-C bond) have absorption coefficients in a wavelength range from 7.8 μm to 9.9 μm. As for a carbon-oxygen bond included in the ester bond and the ether bond, a large absorption coefficient appears in a wavelength range from 8 μm to 10 μm. If a benzene ring is introduced into a side chain of a hydrocarbon resin, absorption appears broadly in a wavelength range from 8.1 μm to 18 μm due to vibration of the benzene ring itself and vibration of surrounding elements due to the benzene ring.

[0065] Examples of resins that have these bonds include an ethylene terephthalate resin, an ethylene naphthalate resin, and a polymethyl methacrylate resin.

[0066] [Consideration on Light Absorption] The following is consideration on absorption of light in the ultraviolet-visible range, that is, absorption of sunlight by resin materials having the above-described bonds and functional groups. The origin of absorption of ultraviolet light and visible light is transition of electrons that contribute to bonds. Absorption of light in this wavelength range can be found by calculating bond energy. First, the following considers wavelengths at which resin materials having a carbon-fluorine bond (C-F) have an absorption coefficient in the ultraviolet-visible range. Bond energies of C-C, C-H, and C-F bonds of a basic structural unit, with polyvinylidene fluoride (PVDF) as a representative, are 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 light of these wavelengths is absorbed.

[0067] Since the sunlight spectrum includes only wavelengths longer than 0.300 μm, if a fluorocarbon resin is used, the resin absorbs almost no ultraviolet rays, visible rays, and near-infrared rays of sunlight. Note that ultraviolet rays are defined as light having a wavelength shorter than 0.400 μm, visible rays are defined as light in a wavelength range from 0.400 μm to 0.800 μm, near-infrared rays are defined as light in a wavelength range from 0.800 μm to 3 μm, mid-infrared rays are defined as light in a wavelength range from 3 μm to 8 μm, and far-infrared rays are defined as light having a wavelength longer than 8 μm.

[0068] As for a carbon-chlorine bond (C-Cl), bond energy between carbon and chlorine in an alkene is 3.28 eV, which corresponds to a wavelength of 0.378 μm, and therefore, ultraviolet rays in sunlight are absorbed well, but almost no light in the visible range is absorbed. FIG. 4 shows an absorptance spectrum in the ultraviolet-visible range of a vinyl chloride resin with a thickness of 100 μm. Light absorption is large at wavelengths shorter than 0.38 μm. FIG. 4 also shows an absorptance spectrum in the ultraviolet-visible range of a vinylidene chloride resin with a thickness of 100 μm. A slight increase can be observed in the absorptance spectrum at wavelengths shorter than 0.4 μm.

[0069] Examples of resins that have any of an ester bond (R-COO-R), an ether bond (C-O-C bond), and a benzene ring include a methyl methacrylate resin, an ethylene terephthalate resin, and an ethylene naphthalate resin. For example, bond energy of a C-C bond in an acrylic resin is 3.93 eV and the resin absorbs sunlight having a wavelength shorter than 0.315 μm, but absorbs almost no light in the visible range.

[0070] FIG. 4 shows an absorptance spectrum in the ultraviolet-visible range of a methyl methacrylate resin with a thickness of 5 mm, as an example of resin materials having the above-described bonds and functional groups. Note that the methyl methacrylate resin described as an example is a commercially available resin in which a benzotriazole ultraviolet absorbing agent is mixed. Since the thickness is as large as 5 mm, the absorptance is large even at wavelengths at which the absorption coefficient is small, and light absorption is large at wavelengths shorter than 0.38 μm but longer than 0.315 μm.

[0071] FIG. 4 also shows an absorptance spectrum in the ultraviolet-visible range of an ethylene terephthalate resin with a thickness of 40 μm, as an example of resin materials having the above-described bonds and functional groups. As shown in the diagram, the absorptance increases as the wavelength gets closer to 0.315 μm, and the absorptance sharply increases at the wavelength of 0.315 μm. In the case of the ethylene terephthalate resin as well, when the thickness is increased, the absorptance becomes large at a wavelength slightly longer than 0.315 μm due to an absorption edge of a C-C bond, and the absorptance for ultraviolet rays becomes large as is the case with methyl methacrylate resin.

[0072] The infrared radiative layer J may be any of a single-layer film made of a single resin material, a multilayer film made of a plurality of resin materials, a single-layer film made of a blend of a plurality of resin materials, and a multilayer film made of blends of a plurality of resin materials, as long as resin materials having the above-described characteristics of the emissivity (light emissivity) and the light absorptance are used. Note that a blend encompasses copolymers such as an alternating copolymer, a random copolymer, a block copolymer, and a graft copolymer, and a modified product obtained by substituting a side chain.

[0073] [Emissivities of Vinyl Chloride Resin and Vinylidene Chloride Resin] FIG. 5 shows the emissivity of a vinyl chloride resin (PVC), which is a representative example of resins having a carbon-chlorine bond, in the atmospheric window. Also, FIG. 6 shows the emissivity of a vinylidene chloride resin (PVDC) in the atmospheric window. As for the carbon-chlorine bond, an absorption coefficient for stretching vibration of C-Cl appears around a wavelength of 12 μm over a wide range with a half width of 1 μm or more. Also, in the case of the vinyl chloride resin, an absorption coefficient for bending vibration of C-H in an alkene contained in the main chain appears at a wavelength of about 10 μm due to electron-withdrawing of chlorine. This also applies to the vinylidene chloride resin. Due to these, a wavelength-averaged emissivity when the thickness is 10 μm is 43% in a wavelength range from 8 μm to 13 μm and falls within the prescribed range of the wavelength-averaged emissivity of 43% or more. As shown in the diagrams, the emissivity in the atmospheric window range increases as the film thickness is increased.

[0074] [Emissivity of Ethylene Terephthalate Resin] FIG. 7 shows the emissivity of an ethylene terephthalate resin, which is a representative example of resins having an ester bond or a benzene ring, in the atmospheric window. An ester bond has an absorption coefficient in a wavelength range from 7.8 μm to 9.9 μm. As for a carbon-oxygen bond included in the ester bond, a large absorption coefficient appears in a wavelength range from 8 μm to 10 μm. When a benzene ring is introduced into a side chain of a hydrocarbon resin, absorption appears broadly in a wavelength range from 8.1 μm to 18 μm due to vibration of the benzene ring itself and vibration of surrounding elements due to the benzene ring. Due to these, a wavelength-averaged emissivity when the thickness is 10 μm is 71% in a wavelength range from 8 μm to 13 μm and falls within the prescribed range of the wavelength-averaged emissivity of 40% or more. As shown in the diagram, the emissivity in the atmospheric window range increases as the film thickness is increased.

[0075] [Temperatures of Light Reflective Layer and Surface of Infrared Radiative Layer] Heat radiation in the atmospheric window from the infrared radiative layer J occurs in the vicinity of the surface of the resin material. As shown in FIG. 5, in the case of the vinyl chloride resin, the amount of heat radiation in the atmospheric window range hardly increases even when the thickness is increased to more than 100 μm. That is, in the case of the vinyl chloride resin, heat radiation in the atmospheric window occurs in a portion of the resin material that is within a depth of about 100 μm from the surface, and radiation from a deeper portion does not go to the outside. FIG. 6 shows that the matter described for the vinyl chloride resin also applies to the vinylidene chloride resin.

[0076] As shown in FIG. 7, in the case of the ethylene terephthalate resin, the amount of heat radiation in the atmospheric window range hardly increases even when the thickness is increased to more than 125 μm. That is, in the case of the ethylene terephthalate resin, heat radiation in the atmospheric window occurs in a portion of the resin material that is within a depth of about 100 μm from the surface, and radiation from a deeper portion does not go to the outside.

[0077] As described above, heat radiation from a surface of a resin material in the atmospheric window range occurs in a portion of the resin material that is within a depth of about 100 μm from the surface, and when the thickness of the resin material is increased to more than 100 μm, the cooling effect obtained through radiative cooling performed by the resin laminated film is insulated by a portion of the resin material that does not contribute to heat radiation. An ideal case will be considered where an infrared radiative layer J is made of a first resin that does not absorb sunlight at all and the infrared radiative layer J is formed on the light reflective layer B. In this case, sunlight is only absorbed by the light reflective layer B of the resin laminated film CP. Resin materials generally have a thermal conductivity of about 0.2 W / m·K, and when a calculation is performed taking the thermal conductivity into account, the temperature of a cooling surface (a surface of the light reflective layer B on the side opposite to the infrared radiative layer J) increases when the thickness of the infrared radiative layer J is larger than 20 mm.

[0078] Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of the first resin of the infrared radiative layer J is generally about 0.2 W / m·K, and accordingly, when the thickness of the resin material layer is larger than 20 mm as shown in FIG. 8, the light reflective layer B is heated by solar radiation and the cooling target on the light reflective layer B side is heated. That is, the thickness of the first resin of the infrared radiative layer J needs to be 20 mm or less.

[0079] Note that FIG. 8 shows a plot of a surface temperature of the radiative surface H and the temperature of the light reflective layer B in a resin laminated film (radiative cooling film), which were calculated assuming the time of solar noon on a sunny day in summer in western Japan. The calculation was performed assuming AM1.5 sunlight with an energy density of 350 W / m2 as an average value of solar irradiance in daytime in summer. The ambient temperature is 30°C, and radiation energy is 100 W at 30°C, although this varies according to the temperature. The calculation was performed assuming that the infrared radiative layer J did not absorb sunlight. The calculation was performed assuming that the radiative cooling device was used in a windless state and the convective heat transfer coefficient was 5 W / m2 / K.

[0080] [Light Absorption by Hydrocarbon Resin] In a case where the resin material (the first resin, the second resin) is a resin that contains, as a main chain, a hydrocarbon having one or two or more of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, absorption through vibration, such as bending or stretching of bonds, is observed in the near-infrared range, in addition to ultraviolet ray absorption by electrons contributing to covalent bonds described above.

[0081] Specifically, absorption based on fundamental tones of transitions of CH3, CH2, and CH to the first excited state appears in a wavelength range from 1.6 μm to 1.7 μm, a wavelength range from 1.65 μm to 1.75 μm, and at a wavelength of 1.7 μm, respectively. Furthermore, absorption based on fundamental tones of combination tones of CH3, CH2, and CH appears at a wavelength of 1.35 μm, a wavelength of 1.38 μm, and a wavelength of 1.43 μm, respectively. Furthermore, overtones of transitions of CH2 and CH to the second excited state appear around a wavelength of 1.24 μm. Fundamental tones of bending and stretching of a C-H bond are widely distributed in a wavelength range from 2 μm to 2.5 μm.

[0082] Also, in a case where the resin material has an ester bond (R-COO-R) or an ether bond (C-O-C), large light absorption appears around a wavelength of 1.9 μm. According to the absorptance equation described above, light absorptances for these are small and inconspicuous when the film thickness of the resin material is small, but become large when the film thickness is large.

[0083] FIG. 9 shows a relationship between the light absorptance of an ethylene terephthalate resin having an ester bond and a benzene ring and the sunlight spectrum in a case where the film thickness is changed. As shown in the diagram, at wavelengths longer than 1.5 μm, light absorption through each vibration increases as the film thickness is increased from 25 μm to 125 μm and 500 μm. Light absorption increases not only on the long wavelength side but also in the ultraviolet range and the visible range. This is because a light absorption edge for a chemical bond has some width.

[0084] When the film thickness is small, the light absorptance becomes large at a wavelength at which the resin has the maximum absorption coefficient, but when the film thickness is increased, a small absorption coefficient for an absorption edge having a width appears as an absorptance according to the absorptance equation described above. Therefore, when the film thickness is increased, light absorption in the ultraviolet range and the visible range increases. As for the reflectance, if the arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm is 80% or more and the arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm is 43% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and if the wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm is 43% or more, the absorption can be suppressed to about 85 W / m2 with respect to solar energy of 350 W / m2. In addition, if the emissivity is 43% or more, energy of 85 W / m2 can be radiated with respect to radiation of about 200 W / m2 when the atmosphere is in good conditions and thus a radiative-cooling function can be exhibited. In other words, it is preferable that a laminated resin layer, constituted by the light reflective layer and the infrared radiative layer, has an arithmetic mean reflectance in a wavelength range from 400 nm to 800 nm of 80% or more and an arithmetic mean reflectance in a wavelength range from 800 nm to 1200 nm of 70% or more, the arithmetic mean reflectance being a wavelength-averaged light reflectance, and has a wavelength-averaged emissivity in a wavelength range from 8 μm to 13 μm of 43% or more.

[0085] Since the light reflective layer B has reflection properties in which the reflectance in a wavelength range from 400 nm to 800 nm is 80% or more and the reflectance in a wavelength range from 800 nm to 1200 nm is 70% or more, solar energy absorbed by the light reflective layer B of the radiative cooling device (radiative cooling film) can be suppressed to 25% or less, that is, the solar energy absorbed at solar noon in summer can be suppressed to about 85 W. Also, when humidity and the like are high, the atmospheric window becomes narrow, but even in the case in which the radiation decreases to, for example, about 125 W / m2, energy greater than solar energy can be released if the emissivity is 70% or more, which is preferable.

[0086] As described above, the maximum value of infrared radiation in the wavelength band of the atmospheric window in summer at a lowland in Japan is about 160 W at 30°C when the atmosphere is in good conditions, and is usually about 125 W. If both the first resin forming the infrared radiative layer J and the second resin forming the light reflective layer B are ethylene terephthalate resin, which is a hydrocarbon resin, and if each film thickness is 500 μm, the sum of solar absorption of the laminated resin layer M (both the infrared radiative layer J and the light reflective layer B) becomes 176 W / m2. Thus, if both the first resin forming the infrared radiative layer J and the second resin forming the light reflective layer B are ethylene terephthalate resin, which is a hydrocarbon resin, and if the film thicknesses of the infrared radiative layer J and the light reflective layer B are each 500 μm or more, that is, if the film thickness of the laminated resin layer M is 1000 μm or more, radiative-cooling performance is not exerted. In other words, it is preferable that the thicknesses of the first resin of the infrared radiative layer J and the second resin of the light reflective layer B are each 500 μm or less. It is also preferable that the thicknesses of the first resin of the infrared radiative layer J and the second resin of the light reflective layer B are each 10 μm or more, and the lower limit of the film thickness is determined from the viewpoint of ensuring infrared emissivity and light reflectance.

[0087] [Light Absorption by Blend Resin] In a case where the resin material (the first resin, the second resin) is obtained by blending a resin that contains a carbon-fluorine bond as a main chain and a resin that contains a hydrocarbon as a main chain, light absorption by CH, CH2, CH3, or the like appears in the near-infrared range according to the proportion of the blended resin containing a hydrocarbon as a main chain. When the carbon-fluorine bond is the main component, light absorption by the hydrocarbon in the near-infrared range is small, and therefore, the thickness can be increased up to 20 mm, which is an upper limit set from the viewpoint of thermal conductivity. However, when the blended hydrocarbon resin is the main component, the thicknesses of the first resin and the second resin each need to be set to 500 μm or less.

[0088] Note that a blend of a fluorocarbon resin and a hydrocarbon encompasses a hydrocarbon-substituted fluorocarbon resin, as well as an alternating copolymer, a random copolymer, a block copolymer, and a graft copolymer of a fluorine monomer and a hydrocarbon monomer.

[0089] Light absorption by CH, CH2, CH3, or the like in the near-infrared range appears according to the molecular weight and proportion of the hydrocarbon side chain, which serves as a substituent. When the monomer introduced as a side chain or a copolymerization monomer has a low molecular weight or the density of the introduced monomer is low, light absorption by the hydrocarbon in the near-infrared range is small, and therefore, the thickness can be increased to the upper limit of 20 mm set from the viewpoint of thermal conductivity. When a high-molecular weight hydrocarbon is introduced as a side chain or a copolymerization monomer into a fluorocarbon resin, the thicknesses of the first resin and the second resin each need to be set to 500 μm or less.

[0090] [Thickness of Infrared Radiative Layer] From the viewpoint of practical use of the resin laminated film CP, the thinner the infrared radiative layer J, the better. The thermal conductivity of a resin material is generally lower than those of metal, glass, and the like. In order to effectively cool the cooling target, it is preferable that the infrared radiative layer J has the minimum required film thickness. Heat radiation in the atmospheric window increases as the film thickness of the infrared radiative layer J is increased, and heat radiation energy in the atmospheric window is saturated when the film thickness exceeds a certain thickness.

[0091] Although the film thickness at which heat radiation is saturated varies according to the resin material, in the case of a fluorocarbon resin, heat radiation is generally sufficiently saturated when the film thickness is 300 μm. Therefore, from the viewpoint of thermal conductivity, it is desirable to set the film thickness to be no greater than 300 μm, rather than 500 μm. Furthermore, even when the thickness is about 100 μm, sufficient heat radiation can be obtained in the atmospheric window range although heat radiation is not saturated. The smaller the thickness is, the higher the thermal transmittance becomes and the more effectively the temperature of the cooling target can be reduced, and therefore, in the case of a fluorocarbon resin, the thickness is preferably set to about 100 μm or less.

[0092] Absorption coefficients of a carbon-silicon bond, a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, and an ether bond are larger than an absorption coefficient of a C-F bond. Naturally, it is desirable to set the film thickness to be no greater than 300 μm, rather than 500 μm, from the viewpoint of thermal conductivity, but if the film thickness is further reduced to increase the thermal conductivity, an even greater radiative cooling effect can be expected. In the case of a resin that contains any of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, heat radiation is saturated even when the thickness is 100 μm, and sufficient heat radiation can be obtained in the atmospheric window range even when the thickness is 50 μm. The smaller the thickness of the resin material is, the higher the thermal transmittance becomes and the more effectively the temperature of the cooling target can be reduced, and therefore, in the case of a resin containing any of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, it is possible to suppress thermal insulation properties and effectively cool the cooling target by setting the thickness to 50 μm or less. In the case of a resin containing a carbon-chlorine bond, it is possible to effectively cool the cooling target when the thickness is 100 μm or less.

[0093] When the thickness is reduced, it is possible to obtain an effect other than the effect of suppressing thermal insulation properties and facilitating conduction of the cooling effect. That is, it is possible to suppress light absorption by CH, CH2, and CH3 in the near-infrared range, which occurs in the case of a resin that contains any of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, and an ether bond. When the thickness is reduced, absorption of sunlight by these can be suppressed and consequently, cooling capability of the resin laminated film CP is increased. From the viewpoint described above, in the case of a resin containing any of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, the radiative cooling effect can be more effectively exhibited under solar radiation when the thickness is 50 μm or less.

[0094] In the case of a carbon-silicon bond, heat radiation in the atmospheric window is sufficiently saturated even when the thickness is 50 μm, and sufficient heat radiation can be obtained in the atmospheric window even when the thickness is 10 μm. The smaller the thickness of the infrared radiative layer J is, the higher the thermal transmittance becomes and the more effectively the temperature of the cooling target can be reduced, and therefore, in the case of a resin containing a carbon-silicon bond, it is possible to suppress thermal insulation properties and effectively cool the cooling target by setting the thickness to 10 μm or less. When the thickness is reduced, absorption of sunlight can be suppressed and consequently, cooling capability of the resin laminated film CP is increased. From the viewpoint described above, in the case of a resin containing a carbon-silicon bond, the radiative cooling effect can be more effectively exhibited under solar radiation when the thickness is 10 μm or less.

[0095] As will be described later, a resin is also used as the light reflective layer B in the resin laminated film CP according to this embodiment. Although the light reflective layer B has voids K at a certain volume fraction as described below, a certain level of heat radiation can be expected. Considering this, it is preferable that the thickness of the infrared radiative layer J described above is made even thinner.

[0096] [Details of Light Reflective Layer] The light reflective layer B provides the above reflection properties (reflection properties as the laminated resin layer M) by making a refractive index of the second resin forming the light reflective layer different from a refractive index of an internal material inside the plurality of voids K included in the second resin. Specifically, it is preferable that the second resin of the light reflective layer B contains at least any one or more 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 reflective layer B because the resin itself is easily colored and reflectance tends to become low.

[0097] Further, various gases and fluids can be included inside the voids K in the second resin of the light reflective layer B, but preferably air is enclosed. The refractive index of the voids K (more specifically, gases or fluids included in the voids K) is smaller than that of the second resin. Also, it is preferable that the voids K have an arithmetic mean pore diameter of 0.1 μm or more and 3.0 μm or less. In this embodiment, the arithmetic mean pore diameter means an arithmetic mean of the minimum inner diameters of the voids K. The voids K can have various shapes such as spherical or elliptical shapes, but from the viewpoint of improving the light reflectance, a flat shape is preferable, and more preferably, a long axis of the voids K is oriented along a direction along the film surface (radiative surface H) of the resin laminated film CP. Further, the volume fraction of the voids K in the light reflective 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 even more preferably 10 vol% or more and 40 vol% or less.

[0098] As a result of diligent study by the inventors of the present invention, it is preferable that the second resin of the light reflective layer B has a thickness of 10 μm or more and 500 μm or less. If the thickness of the second resin of the light reflective layer B is set to 10 μm or more, reflectance required for radiative cooling can be favorably ensured by the light reflective layer B made of the second resin having a plurality of voids K. In addition, if the thickness is set to 500 μm or less, the heat-insulating effect by the second resin having voids K including air and the like can be limited to a certain level or less, and cooling performance of the cooling target can be ensured at or above a certain level. The second resin of the light reflective layer B has a thickness of preferably 50 to 300 um, and more preferably 75 to 200 um. If the thickness is 500 μm or more, thermal conductivity in the thickness direction decreases and insulation becomes strong, and thus in the case of application to a casing or the like having a heat source inside, heat storage inside the casing increases, which is undesirable from the viewpoint of heat radiation.

[0099] The resin laminated film CP may include a filler F (F1, F2) in the first resin forming the infrared radiative layer J and in the second resin forming the light reflective layer B, as shown in FIG. 2. The filler F (F1, F2) may be included in at least one of the first resin forming the infrared radiative layer J and the second resin forming the light reflective layer B. The filler F (F1, F2) may be any 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 the filler F1 included in the first resin may be different from the filler F2 included in the second resin.

[0100] [Experimental Results] With respect to the examples and comparative examples of the laminated resin film described above, Tables 1 to 4 below show results of various tests regarding soiling resistance, ultraviolet reflectance, reflectance in a wavelength range from 400 nm to 800 nm, reflectance in a wavelength range from 800 nm to 1200 nm, transmittance in a wavelength range from 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic-wave transmissivity. In the test results shown in the tables, underlined portions indicate that conditions of the respective tests are not satisfied. Incidentally, Tables 1 to 4 also show various conditions of films constituting the examples and comparative examples.

[0101] Soiling resistance was evaluated by performing an outdoor exposure test for one month in Osaka City, using color difference ΔE before and after exposure, and defining that those having ΔE < 2.0 have high (good) soiling resistance. The color difference ΔE means “CIEDE2000 color difference” based on JIS Z8781.

[0102] Ultraviolet reflectance was evaluated using an arithmetic mean of reflectance in a wavelength range from 340 nm to 400 nm measured using a UV-Vis Spectrophotometer UV-2600 (manufactured by Shimadzu Corporation). Those having a reflectance of 50% or less were defined as satisfying the condition (low ultraviolet reflectance).

[0103] Reflectance in a wavelength range from 400 nm to 800 nm was evaluated using an arithmetic mean of reflectance in a wavelength range from 400 nm to 800 nm measured using a UV-Vis Spectrophotometer UV-2600 (manufactured by Shimadzu Corporation). Those having a reflectance of 80% or more were defined as satisfying the condition (high reflectance in a wavelength range from 400 nm to 800 nm).

[0104] Reflectance in a wavelength range from 800 nm to 1200 nm was evaluated using an arithmetic mean of reflectance in a wavelength range from 800 nm to 1200 nm measured using a UV-Vis Spectrophotometer UV-2600 (manufactured by Shimadzu Corporation). Those having a reflectance of 70% or more were defined as satisfying the condition (high reflectance in a wavelength range from 800 nm to 1200 nm).

[0105] Transmittance in a wavelength range from 400 nm to 800 nm was evaluated using an arithmetic mean of transmittance in a wavelength range from 400 nm to 800 nm measured using a UV-Vis Spectrophotometer UV-2600 (manufactured by Shimadzu Corporation). Those having a transmittance of 1% or more were defined as satisfying the condition (high transmittance in a wavelength range from 400 nm to 800 nm).

[0106] Infrared emissivity was evaluated using an arithmetic mean of emissivity in a wavelength range from 8 μm to 13 μm measured using an FT-IR IRTracer-100 (manufactured by Shimadzu Corporation). Those having an emissivity of 70% or more were defined as satisfying the condition (high infrared emissivity in a wavelength range from 400 nm to 800 nm).

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

[0108] Xenon weather resistance was evaluated by exposing samples for 3000 hours to ultraviolet rays having an intensity of 180 W / m2 in an environment where black panel temperature (BPT) is 63°C, in a xenon weather resistance test defined in JIS K5600, measuring color difference ΔE before and after the test. Those having ΔE < 2.0 were defined as having high (good) weather resistance.

[0109] Radio-wave transmissivity was measured at 800 MHz using a KEC method at KEC Kansai Electronics Industry Development Center (a general incorporated association). Those having an attenuation degree of 10 dB or less were defined as having high (good) radio-wave transmissivity.

[0110] In the tables, PET means polyethylene terephthalate, PEN means polyethylene naphthalate, PVC means polyvinyl chloride, PVDC means polyvinylidene chloride, PVDF means polyvinylidene fluoride (poly(vinylidene fluoride)), and PP means polypropylene.

[0111] For preparation of the sample of Example 1, a vinyl chloride resin containing TiO2 was formed into a thin film by a calender process, and was bonded to a PET film containing TiO2 by a dry lamination method. 

[0112] Table 1 Ex. 1Ex. 2Ex. 3Ex. 4Ex. 5Infrared radiative layerFirst resinPVCPVCPVCPVCPVCFiller typeTiO2TiO2TiO2TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm240 nm240 nm240 nmFiller concentration5.0%7.5%5.0%5.0%5.0%Presence of voidsAbsentAbsentAbsentAbsentAbsentVoid volume %−−−−−Void arithmetic mean pore diameter−−−−−Thickness50 um50 um50 um50 um50 umLight reflective layerSecond resinPETPETPETPPPENFiller typeTiO2TiO2BaSO4TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm500 nm240 nm240 nmFiller concentration10.0%10.0%10.0%10.0%10.0%Presence of voidsPresentPresentPresentPresentPresentVoid volume %25 vol%25 vol%25 vol%25 vol%25 vol%Void arithmetic mean pore diameter400 nm400 nm400 nm400 nm400 nmThickness100 um100 um100 um100 um100 umSoiling resistance (1-month outdoor exposure in Osaka)ΔE<2.0GoodGoodGoodGoodGoodUltraviolet reflectance (340-400 nm)≤501313201313Reflectance (400-800 nm)≥889192959191Reflectance (800-1200 nm)≥808283928282Transmittance (400-800 nm)≥133233Infrared emissivity≥859595959595Thermal conductivity GoodGoodGoodGoodGoodXenon weather resistance3000 h yellowingGoodGoodGoodGoodGoodElectromagnetic-wave transmissivity≤10dBGoodGoodGoodGoodGood

[0113] Table 2 Ex. 6Ex. 7Ex. 8Com.Ex. 9Ex. 10Infrared radiative layerFirst resinPVCPVCPVCPVDCPVDFFiller typeTiO2TiO2TiO2TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm240 nm240 nm240 nmFiller concentration5.0%0.0%5.0%5.0%5.0%Presence of voidsAbsentAbsentAbsentAbsentAbsentVoid volume %−−−−−Void arithmetic mean pore diameter−−−−−Thickness75 um75 um50 um50 um50 umLight reflective layer Second resinPETPETPETPETPETFiller typeTiO2TiO2TiBaO3TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm240 nm240 nm240 nmFiller concentration10.0%10.0%10.0%10.0%10.0%Presence of voidsPresentPresentPresentPresentPresentVoid volume %25 vol%25 vol%25 vol%25 vol%25 vol%Void arithmetic mean pore diameter400 nm400 nm400 nm400 nm400 nmThickness75 um150 um50 um100 um100 umSoiling resistance (1-month outdoor exposure in Osaka)ΔE<2.0GoodGoodGoodGoodGoodUltraviolet reflectance (340-400 nm)≤501310151313Reflectance (400-800 nm)≥889288919191Reflectance (800-1200 nm)≥808380828282Transmittance (400-800 nm)≥135333Infrared emissivity≥859595959595Thermal conductivity GoodGoodGoodGoodGoodXenon weather resistance3000 h yellowingGoodGoodGoodGoodGoodElectromagnetic-wave transmissivity≤10dBGoodGoodGoodGoodGood

[0114] Table 3 Ex. 11Ex. 12Ex. 13Ex. 14Ex. 15Infrared radiative layerFirst resinPVCPVCPVCPVCPVCFiller typeTiO2TiO2TiO2TiO2TiO2Filler arithmetic mean particle diameter270 nm240 nm240 nm240 nm240 nmFiller concentration5.0%5.0%5.0%5.0%5.0%Presence of voidsAbsentAbsentAbsentAbsentAbsentVoid volume %−−−−−Void arithmetic mean pore diameter−−−−−Thickness50 um50 um50 um50 um50 umLight reflective layer Second resinPETPETPETPETPETFiller typeTiO2TiO2TiO2TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm240 nm240 nm240 nmFiller concentration10.0%10.0%10.0%10.0%10.0%Presence of voidsPresentPresentPresentPresentPresentVoid volume %25 vol%25 vol%25 vol%25 vol%25 vol%Void arithmetic mean pore diameter400 nm400 nm400 nm300 nm600 nmThickness100 um100 um100 um100 um100 umSoiling resistance (1-month outdoor exposure in Osaka)ΔE<2.0GoodGoodGoodGoodGoodUltraviolet reflectance (340-400 nm)≤501315101513Reflectance (400-800 nm)≥889193909193Reflectance (800-1200 nm)≥808285818284Transmittance (400-800 nm)≥133333Infrared emissivity≥859595959595Thermal conductivity GoodGoodGoodGoodGoodXenon weather resistance3000 h yellowingGoodGoodGoodGoodGoodElectromagnetic-wave transmissivity≤10dBGoodGoodGoodGoodGood

[0115] Table 4  Com.Ex. 1Com.Ex. 2Com.Ex. 3Com.Ex. 4Com.Ex. 5Com.Ex. 6Infrared radiative layer First resinPETPETPETPETPETPVCFiller typeTiO2TiO2TiO2TiO2TiO2TiO2Filler arithmetic mean particle diameter240 nm240 nm240 nm240 nm240 nm240 nmFiller concentration10.0%10.0%10.0%10.0%5.0%5.0%Presence of voidsPresentPresentPresentPresentAbsentAbsentVoid volume %25 vol%25 vol%25 vol%80 vol%--Void arithmetic mean pore diameter400 nm400 nm400 nm100 nm--Thickness100 um100 um600 um100 um100 um100 umLight reflective layer Second resinNonePETPETPETNoneSilver-deposited PETFiller type-TiO2TiO2TiO2--Filler arithmetic mean particle diameter-240 nm240 nm240 nm--Filler concentration-5.0%5.0%5.0%--Presence of voids-AbsentAbsentAbsent--Void volume %-AbsentAbsentAbsent--Void arithmetic mean pore diameter------Thickness-50 um50 um50 um--Soiling resistance (1-month outdoor exposure in Osaka)ΔE<2.0PoorPoorPoorPoorGoodGoodUltraviolet reflectance (340-400 nm)≤508131515820Reflectance (400-800 nm)≥88809095938095Reflectance (800-1200 nm)≥80758085827596Transmittance (400-800 nm)≥11032380Infrared emissivity≥85808085808095Thermal conductivity GoodGoodPoorPoorGoodGoodXenon weather resistance3000 h yellowingPoorPoorPoorPoorPoorGoodElectromagnetic-wave transmissivity≤10dBGoodGoodGoodGoodGoodPoor 

[0116] As shown in the experimental results above, in the resin laminated films CP according to Examples 1 to 16 of the present invention, results satisfying the specified conditions were obtained for soiling resistance, ultraviolet reflectance, reflectance in a wavelength range from 400 nm to 800 nm, reflectance in a wavelength range from 800 nm to 1200 nm, transmittance in a wavelength range from 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic-wave transmissivity.

[0117] In contrast, in Comparative Examples 1 to 4, since relatively many voids K are formed in the infrared radiative layer J serving as a surface layer, the soiling resistance condition is not satisfied and soil tends to adhere. In Comparative Examples 1 and 5, since the second resin of the light reflective layer B is not provided, the conditions regarding reflectance in a wavelength range from 400 nm to 800 nm and reflectance in a wavelength range from 800 nm to 1200 nm are not satisfied and reflectance is low. In Comparative Example 6, since a PET film with silver, which is a metal, deposited is used as the light reflective layer B, the condition of transmittance in a wavelength range from 400 nm to 800 nm is not satisfied and daylighting performance is poor, and the radio-wave transmissivity condition is also not satisfied. Also, in Comparative Examples 1 and 5, since the second resin of the light reflective layer B is not provided, infrared emissivity is considered not to satisfy the condition, suggesting that the second resin of the light reflective layer B contributes to infrared emissivity to a certain extent. In Comparative Examples 2 and 4, it is inferred that the infrared emissivity condition is not satisfied because a plurality of voids K are provided in a relatively thin infrared radiative layer J of 100 μm. In Comparative Examples 3 and 4, since a resin layer having voids K is thick and thermal conductivity of the entire material decreases, the thermal conductivity condition is not satisfied. In Comparative Examples 1 to 5, weather resistance of PET to ultraviolet rays is insufficient, and yellowing occurs in xenon weather resistance evaluation, and thus the xenon weather resistance condition is not satisfied.

[0118] [Other Embodiments](1) A configuration may be adopted in which the radiative surface H of the infrared radiative layer J is protected by a protective layer (not shown). As the protective layer, materials such as fluorine, fluorinated acrylic, and the like can be suitably used, and the thickness thereof is preferably about 0.1 μm or more and 100 μm or less. As the material, polyethylene or polypropylene having low emissivity in the atmospheric window may also be used. The protective layer has an anti-soiling function, a scratch-prevention function, and a role as a sacrificial layer.

[0119] (2) A bonding resin layer may be provided on the reflective layer B on the side opposite to the infrared radiative layer J. The bonding resin layer can be, for example, a bonding layer made of polyvinyl chloride, whereby it can be suitably bonded to a vinyl chloride film material, tarpaulin, and a steel plate. Hereinafter, specific configuration examples in which the resin laminated film CP is bonded to another material via the bonding resin layer will be described.

[0120] As one application, a combination with a film material is conceivable. If a general film material is bonded to the resin laminated film CP via the bonding resin layer, a film material having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or the like can be suitably used. Such a film material with the resin laminated film CP can be sewn or thermally welded, and can be utilized for buildings, tents, sunshades, truck covers, and the like.

[0121] As one application, a combination with a resin waterproof sheet is conceivable. If a general resin waterproof sheet (e.g., “New Best-proof” manufactured by Lonseal Corporation) is bonded to the resin laminated film CP via the bonding resin layer, a resin waterproof sheet having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, or the like can be suitably used. Such a resin waterproof sheet with the resin laminated film CP can be thermally welded and can be utilized for rooftop waterproofing of buildings.

[0122] As one application, a combination with an asphalt waterproof sheet is conceivable. If a general asphalt waterproof sheet is bonded to the resin laminated film CP via the bonding resin layer, an asphalt waterproof sheet having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the asphalt waterproof sheet and the resin laminated film CP may be directly bonded by melting at least one of them by heat. Such an asphalt waterproof sheet with the resin laminated film CP can be adhered to building materials such as metal roofs, concrete roofs, and slate roofs, and can be utilized for cooling buildings.

[0123] As one application, a combination with a clothing fabric is conceivable. If a general clothing fabric is bonded to the resin laminated film CP via the bonding resin layer, a clothing fabric having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the clothing fabric and the resin laminated film CP may be directly bonded by melting at least one of them by heat. If clothing is produced with such a clothing fabric with the resin laminated film CP and used, improvement of heat sensation outdoors and prevention effects against heat stroke can be expected.

[0124] As one application, a combination with a magnet sheet is conceivable. If a general magnet sheet is bonded to the resin laminated film CP via the bonding resin layer, a magnet sheet having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the magnet sheet and the resin laminated film CP may be directly bonded by melting the resin laminated film CP by heat. If such a magnet sheet with the resin laminated film CP is applied to an outdoor metal adherend surface exposed to sunlight (e.g., a metal housing), it can be utilized for cooling the adherend surface.

[0125] As one application, a combination with a metal plate is conceivable. If a general metal plate (such as SUS or an aluminum alloy plate) is bonded to the resin laminated film CP via the bonding resin layer, a metal plate having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the metal plate and the resin laminated film CP may be directly bonded by melting the resin laminated film CP by heat. If such a metal plate with the resin laminated film CP is processed to produce a metal roof or a metal wall and applied to a building, a building having a high cooling effect can be realized.

[0126] As one application, a combination with a slate plate is conceivable. If a general slate plate is bonded to the resin laminated film CP via the bonding resin layer, a slate plate having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the slate plate and the resin laminated film CP may be directly bonded by melting the resin laminated film CP by heat. If such a slate plate with the resin laminated film CP is processed to produce a slate roof or a slate wall and applied to a building, a building having a high cooling effect can be realized.

[0127] As one application, a combination with roof tiles is conceivable. If general roof tiles are bonded to the resin laminated film CP via the bonding resin layer, roof tiles having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, a resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If such roof tiles with the resin laminated film CP are applied to a building, a building having a high cooling effect can be realized.

[0128] As one application, a combination with a concrete plate is conceivable. If a general concrete plate is bonded to the resin laminated film CP via the bonding resin layer, a concrete plate having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If such a concrete plate with the resin laminated film CP is processed to produce a concrete roof or a concrete wall and applied to a building, a building having a high cooling effect can be realized.

[0129] As one application, a combination with a siding board is conceivable. If a general siding board is bonded to the resin laminated film CP via the bonding resin layer, a siding board having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the siding board and the resin laminated film CP may be directly bonded by melting the resin laminated film CP by heat. If such a siding board with the resin laminated film CP is processed to produce a wall and applied to a building, a building having a high cooling effect can be realized.

[0130] As one application, a combination with a resin plate is conceivable. If a general resin plate is bonded to the resin laminated film CP via the bonding resin layer, a resin plate having cooling performance can be produced. In this case, as the bonding resin layer of the resin laminated film CP, an adhesive layer made of resin such as acrylic, urethane, silicone, vinyl chloride, vinylidene chloride, polyester, or the like can be suitably used. If the resin laminated film CP having no bonding resin layer is used, the resin plate and the resin laminated film CP may be directly bonded by melting at least one of the resin plate and the resin laminated film CP by heat. If such a resin plate with the resin laminated film CP is processed to produce a housing, a housing having a high cooling effect outdoors can be realized.

[0131] Note that the configurations disclosed in the above embodiment (including the variations, which shall similarly apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as no contradiction arises; the embodiments disclosed in the present specification are examples; and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention. Industrial Applicability

[0132] The resin laminated film according to the present invention is effectively applicable as a resin laminated film that can exhibit high cooling capability under direct sunlight and also exhibit high radio-wave transmissivity, and that can, if voids are provided in a resin material, prevent a decrease in radiative-cooling performance and a decrease in cooling performance that is caused by soiling of the voids. Description of Reference Signs

[0133] B: Light reflective layer CP: Resin laminated film F: Filler H: Radiative surface IR: Infrared light J: Infrared radiative layer K: Voids M: Laminated resin layer S: Bonding 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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