Resin laminated film

Abstract

It can exhibit high cooling capacity even under direct sunlight and high radio wave transmittance, and prevents a decrease in radiative cooling performance when holes are provided in the resin material and a decrease in cooling performance due to contamination of the holes. [Solution] The light reflecting layer B has a plurality of pores K and is made of a second resin. The infrared emitting layer J is made of a first resin that emits thermal radiation energy at wavelengths of 8 μm to 13 μm that is greater than the absorbed solar energy. The infrared emitting layer J has fewer pores than the light reflecting layer B. A laminated resin layer M including the light reflecting layer B and the infrared emitting layer J has an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of the emissivity at wavelengths of 8 μm to 13 μm of 43% or more.

Description

[Technical field]

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

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

[0003] [Patent Document 1] Special Publication No. 2018-526599 [Patent Document 2] Special Publication No. 2022-528289 [Patent Document 3] International Publication No. 2018 / 062541 Summary of the Invention [Problem to be solved by the invention]

[0004] Conventional radiative cooling materials have achieved high solar reflectance by reflecting sunlight with a thin metal film, but the use of thin metal films has the problem of increasing the absorption rate, which is a factor in increasing the material temperature under direct sunlight. In addition, the use of thin metal films has low radio wave permeability, which means that communication devices cannot function properly when enclosed in a space. Furthermore, when a thin metal film is used as a reflective layer, if the surface is scratched and the metal layer is exposed, corrosion will begin from the metal layer, and the metal layer will become discolored due to oxidation, which can lead to a decrease in reflectance. Furthermore, when a metal thin film is used for the reflective layer, there is a problem that the degree of decrease in reflectance when deteriorated is greater than that of a reflective layer made of resin, because even a small amount of metal oxide is likely to cause coloration.

[0006] Also, there are radiative cooling materials that utilize the porous material itself as a radiation layer (see Patent Document 3). It is difficult for such radiative cooling materials to maximize the radiative cooling capacity in the atmospheric window region. There are various types of materials that can be made porous, such as polyethylene terephthalate, polypropylene, polyethylene, and polyethylene naphthalate, but since the amount of material that contributes to radiation decreases when made porous, it is necessary to increase the thickness to obtain a large radiative cooling capacity. The radiative cooling material is a material intended to cool the object to which it is attached, and an increase in the resin layer, especially the porous resin layer, inhibits the capacity of the radiative cooling material. From this perspective, a design that radiates from the porous resin layer itself inhibits cooling of the object.

[0007] In addition, when improving radiation capacity by using a porous material, the poor thermal conductivity caused by the porosity causes a problem that the temperature of the object to be cooled does not reach the resin located at the top surface, and the object cannot be cooled sufficiently. In addition, in the case of a porous resin layer in which layers containing air are stacked in multiple layers like a mille-feuille, the emissivity tends to decrease when the layers are multi-layered compared to when the layers are not multi-layered. This is because the optical multilayer film structure forms a photonic band gap structure and improves the reflectivity. For this reason, it cannot be said that using a porous resin layer not only as a reflective layer but also as a radiative layer is preferable in terms of improving the cooling structure of the radiative cooling material.

[0008] The object of the present invention is to provide a cooling device that can exhibit high cooling capacity under direct sunlight, high radio wave transmittance, and can reduce the radiation cooling performance when holes are provided in a resin material. DownThe object of the present invention is to provide a resin laminate film capable of preventing such deformation. [Means for solving the problem]

[0009] The resin laminate film for achieving the above object is A resin laminate film comprising an infrared emitting layer that emits infrared light from a emitting surface, and a light reflecting layer located on a side of the infrared emitting layer opposite to a side on which the emitting surface is present, the light reflecting layer has a plurality of pores and is made of a second resin; the infrared radiation layer is made of a first resin that emits thermal radiation energy at a wavelength of 8 μm to 13 μm that is greater than the absorbed solar energy; the infrared emitting layer includes fewer voids than the light reflecting layer includes; The laminated resin layer including the light reflecting layer and the infrared emitting layer has an arithmetic mean reflectance, which is a wavelength average of light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is a wavelength average of light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of emissivity at wavelengths of 8 μm to 13 μm of 43% or more. the law of nature, The thickness of the first resin is 10 μm or more and 500 μm or less, The thickness of the second resin is 10 μm or more and 500 μm or less, The second resin includes at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate; The first resin includes at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate. It is at the point.

[0010] According to the above characteristic configuration, firstly, since a metal thin film is not used as the light reflecting layer, the solar light absorptance can be suppressed and the temperature rise of the resin laminate film can be suppressed compared to a configuration using a metal thin film as the light reflecting layer. Furthermore, since the radio wave transmittance can be made relatively high, even in a situation where the resin material film having the above characteristic configuration surrounds a wireless communication device, communication by the wireless communication device can be maintained well. 。

[0011] In addition, by making the number of pores in the infrared radiation layer substantially zero, the volume ratio of the first resin material that contributes to radiation in the radiative cooling layer can be sufficiently secured, and the radiative cooling capacity can be sufficiently secured. Furthermore, the thermal conductivity can be improved, making it easier for the heat of the object to be cooled to be transferred to the radiative surface, and an improvement in the 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 emitting layer, the emissivity of the infrared emitting layer can be improved.

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

[0013] As described above, in a laminated resin layer having an arithmetic mean reflectance of 80% or more, which is the wavelength average of the light reflectance of wavelengths from 400 nm to 800 nm, and an arithmetic mean reflectance of 70% or more, which is the wavelength average of the light reflectance of wavelengths from 800 nm to 1200 nm, the light reflecting layer absorbs only about 2% of the solar energy, due to the absence of metal. As a result, the solar energy absorbed by the light reflecting layer at the meridian in summer is reduced to 20 W / m 2 The radiation cooling can be performed even better. Furthermore, as in the above characteristic configuration, by setting the thickness of the second resin of the light reflecting layer to 10 μm or more, the light reflecting layer made of the second resin having a plurality of pores can satisfactorily ensure the reflectance required for radiation cooling. In addition, by setting the thickness to 500 μm or less, the heat insulating effect of the second resin having pores containing air or the like can be kept below a certain level, and the cooling performance of the object to be cooled can be ensured above a certain level. Incidentally, if the thickness is 500 μm or more, it becomes difficult to make the material conform to the curved portion when applied to the curved portion from the viewpoint of rigidity, and if the material is forced to conform to the curved portion, it is not desirable. In addition, if the thickness is too thick during roll-to-roll processing, the amount of material that can be produced at one time is reduced, which is not desirable. That is, by selecting an appropriate material as the second resin having a plurality of pores, and by providing a light reflecting layer having a thickness of 10 μm or more and 500 μm or less together with the infrared radiation layer, it is possible to achieve an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 400 nm to 800 nm, of 80% or more, and an arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 800 nm to 1200 nm, of 70% or more. The thickness of the light reflecting layer is preferably 50 to 300 μm, and more preferably 75 to 200 μm. Furthermore, the thickness of the first resin is not less than 10 μm and not more than 500 μm. In particular, according to the resin laminate film of the present invention, the first resin of the infrared radiation layer does not contain multiple pores and can exhibit higher radiation performance than an infrared radiation layer containing pores, so that even if the film thickness is relatively thin at 500 μm, the required radiation performance can be well secured. Incidentally, if the thickness is more than 500 μm, it becomes difficult to make the material conform to the curved part when applied to the curved part from the viewpoint of rigidity, and if the material is forced to conform to the curved part, it will be destroyed, which is undesirable. In addition, if the thickness is too thick during roll-to-roll processing, the amount of material that can be produced at one time will be small, which is undesirable. Furthermore, by ensuring a thickness of 10 μm or more, sufficient emissivity can be ensured. Furthermore, the second resin of the light reflecting layer includes at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate, and the first resin forming the infrared emitting layer includes at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate. As shown in FIG. 2, the resin having a carbon-fluorine bond (CF) is CHF and CF 2 The absorption coefficient due to the above phenomenon is widely spread over a wide band from 8 μm to 13 μm, which is the atmospheric window, and the absorption coefficient is particularly large at 8.6 μm. In addition, there is no noticeable absorption coefficient in the solar wavelength band from 0.3 μm to 2.5 μm, where the energy intensity is high. In addition, resins with carbon-chlorine bonds (C-Cl) have an absorption coefficient due to the C-Cl stretching vibration that appears in a broad band of 1 μm or more at half-width centered around a wavelength of 12 μm. In the case of polyvinyl chloride resin, an absorption coefficient due to the CH bending vibration of the alkene contained in the main chain appears at a wavelength of around 10 μm due to the influence of chlorine electron withdrawal. The inventors took these absorption-related characteristics into consideration when selecting the material for the first resin. Furthermore, it is more preferable that the first resin contains at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride. In particular, regarding the wavelengths at which resin materials with carbon-fluorine bonds (CF) have absorption coefficients in the ultraviolet to visible range, the bond energies of the CC bonds, CH bonds, and CF bonds in the basic structure of polyvinylidene fluoride (PVDF) 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 absorb light of these wavelengths. For this reason, from the viewpoint of absorbing ultraviolet rays in the first resin of the infrared emitting layer and reducing the amount of ultraviolet rays that transmit through the light reflecting layer, it is preferable to employ polyvinyl fluoride or polyvinylidene fluoride as the first resin.

[0014] From the above, it is possible to demonstrate high cooling capacity under direct sunlight, high radio wave transmittance, and low radiation cooling performance when holes are provided in the resin material. Down It is possible to realize a resin laminate film that can prevent this.

[0015] Further characteristic configurations of the resin laminate film are as follows: The infrared radiation layer is characterized in that the first resin contains a filler.

[0016] As explained above, an infrared radiation layer, which is usually installed with its radiation surface facing the atmosphere, is composed of a first resin layer having no voids, and is intended to improve anti-fouling properties, radiative cooling capacity, and heat transfer in a direction intersecting the radiation surface. However, by including a filler in the first resin as in the above characteristic configuration, the infrared radiation layer can also exhibit a certain level of light reflection performance due to the difference in refractive index between the first resin layer and the filler. This allows solar radiation to be reflected not only by the light-reflecting layer, but also by the infrared-emitting layer, thereby maintaining a high reflectance for the entire material.

[0020] Further characteristic configurations of the resin laminate film are as follows: The pores in the second resin have a refractive index smaller than that of the second resin, The arithmetic mean pore size of the pores is 0.1 μm or more and 3.0 μm or less.

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

[0022] Further characteristic configurations of the resin laminate film are as follows: The volume ratio of the voids in the light reflecting layer is 0.1 volume % or more and 60 volume % or less.

[0023] The inventors have confirmed that the reflectance of the light reflective layer can be set to the above-mentioned arithmetic average reflectance by setting the volume ratio of the voids in the light reflective layer as described above. More preferably, the volume percentage of the voids in the light reflecting layer is 1 volume % or more and 50 volume % or less, and the volume percentage of the voids in the light reflecting layer is 10 volume % or more and 40 volume % or less. If the material has 60% or more voids by volume, the thermal conductivity will decrease, and in the case of a system with an internal heat source, heat will accumulate, which is undesirable from the viewpoint of heat dissipation. In addition, if the material has 60% or more voids by volume, there will be a problem of reduced strength. Furthermore, if the volume fraction of the voids is 0.1% by volume or less, it is difficult to sufficiently improve the reflectance even if the average particle size and arrangement of the voids are devised.

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

[0025] Further characteristic configurations of the resin laminate film are as follows: The laminated resin layer has an arithmetic mean transmittance, which is the wavelength average of the transmittance of light having a wavelength of 400 nm to 800 nm, of 1% to 12%.

[0026] According to the present invention, the arithmetic mean transmittance, which is the wavelength average of the light transmittance from 400 nm to 800 nm, is set to be 1% or more and 12% or less. This allows light with wavelengths of 400 nm to 800 nm to transmit well through both the first resin of the infrared radiation layer and the second resin of the light reflecting layer, and reflects light at the boundary between the second resin of the light reflecting layer and the pores, thereby making it possible to satisfactorily improve the reflectance of the laminated resin layer. In other words, the absorptance in the laminated resin layer can be reduced. In addition, by having a light transmittance of 1% or more, it is advantageous in that lighting properties can be ensured when used outdoors.

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

[0028] Further characteristic configurations of the resin laminate film are as follows: The second resin contains a filler.

[0029] As in the above characteristic configuration, by configuring the second resin forming the light reflecting layer to contain a filler in addition to the multiple 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, in order to ensure a certain level of thermal conductivity, even if the volume ratio of the voids to the second resin is made relatively low or the thickness is kept thin, a high arithmetic mean reflectance can be maintained.

[0030] Further characteristic configurations of the resin laminate film are as follows: The filler may be titanium oxide, glass microbeads, Diacid Silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminium silicate RumiThe oxide may be any one or more of cerium oxide, heavy calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate. They may also be porous.

[0031] By incorporating the above-mentioned filler in the first resin forming the infrared emitting layer or the second resin forming the light reflecting layer, it is possible to achieve good light reflectance for the entire laminated resin layer. In addition, the inventors have particularly used titanium oxide, glass microbeads, and Oxidation Silicon, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminium silicate Rumi It has been confirmed that when one or more of the following materials are used as the laminated resin layer, the arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths of 400 nm to 800 nm, and the arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths of 800 nm to 1200 nm, can be high enough to adequately exhibit the radiative cooling function.

[0037] Further characteristic configurations of the resin laminate film are as follows: The first resin contains an ultraviolet absorbing agent, The infrared radiation layer has an arithmetic mean reflectance, which is the wavelength average of the reflectance of ultraviolet rays having wavelengths of 340 nm to 400 nm, of 50% or less.

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

[0039] Further characteristic configurations of the resin laminate film are as follows: 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, the connecting layer being included in the laminated resin layer; The connecting layer includes at least one of a filler and a hollow particle.

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

[0041] Further characteristic configurations of the resin laminate film are as follows: The pores in the second resin have a flat shape.

[0042] According to the above characteristic configuration, it is possible to provide multiple layers with different refractive indices, which has the advantage that light reflection is more likely to occur than when the holes have a non-flat structure at the same thickness, and the reflectance can be easily increased even for the same thickness. [Brief description of the drawings]

[0043] [Figure 1] FIG. 2 is a diagram illustrating an embodiment of a resin laminate film. [Diagram 2] FIG. 4 is a diagram illustrating another embodiment of the resin laminate film. [Diagram 3] FIG. 4 is a diagram showing the relationship between the absorption coefficient of a resin material and a wavelength band. [Figure 4] FIG. 4 is a diagram showing the relationship between the light absorptance of a resin material and the wavelength. [Diagram 5] FIG. 1 is a diagram showing the emissivity spectrum of polyvinyl chloride resin. [Figure 6] FIG. 2 is a diagram showing the emissivity spectrum of vinylidene chloride resin. [Figure 7] FIG. 2 is a diagram showing the emissivity spectrum of ethylene terephthalate resin. [Figure 8]FIG. 4 is a diagram showing the relationship between the temperature of the radiation surface and the temperature of the light reflecting layer. [Figure 9] FIG. 2 is a diagram showing the light absorptance spectrum of ethylene terephthalate resin. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0044] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic structure of resin laminate film] As shown in FIG. 1, the resin laminate film CP has an infrared emitting layer J that radiates infrared light IR from an emitting surface H, and a light reflecting layer B that is located on the side of the infrared emitting layer J opposite to the side on which the emitting surface H exists, laminated together, and is formed into a film shape. In other words, the resin laminate film CP is configured as a radiative cooling film.

[0045] The light reflecting layer B has a plurality of voids K and is made of a second resin. The infrared radiation layer J is made of a first resin that emits thermal radiation energy at a wavelength of 8 μm to 13 μm that is greater than the absorbed solar light energy. The infrared radiation layer J contains fewer voids K than the light reflecting layer B, and the infrared radiation layer J is a layer that does not substantially contain voids K.

[0046] Furthermore, the laminated resin layer M consisting of the light-reflecting layer B and the infrared-emitting layer J is configured so that the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, is 80% or more, the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, is 70% or more, and the wavelength average of the emissivity at wavelengths of 8 μm to 13 μm is 43% or more. In this specification, the laminated resin layer M is a concept that also includes a connection layer S that connects the light reflecting layer B and the infrared emitting layer J.

[0047] More preferably, the laminate resin layer M has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths from 400 nm to 800 nm, of 84% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths from 800 nm to 1200 nm, of 75% or more, and the laminate resin layer M has an arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths from 400 nm to 800 nm, of 88% or more, and an arithmetic mean reflectance, which is the wavelength average of the reflectance of light with wavelengths from 800 nm to 1200 nm, of 80% or more. Moreover, the laminated resin layer M more preferably has an average wavelength emissivity of 70% or more in the wavelength range of 8 μm to 13 μm, and further preferably has an average wavelength emissivity of 85% or more. Incidentally, the reflectance can be improved by selecting materials for the infrared radiation layer J, the connection layer S, and the light reflecting layer B that have a large difference in refractive index between them. As an example, polyvinylidene chloride containing TiO2 can be used for the infrared radiation layer, an acrylic adhesive can be used for the connection layer S, and PET containing a number of voids can be used for the light reflecting layer B.

[0048] By having this characteristic, the laminated resin layer M can suppress the solar energy absorption to 2% or less, and the solar energy absorbed at the meridian in the Japanese summer can be suppressed to 20 W / m 2 It can be about that.

[0049] In this embodiment, light L includes ultraviolet light, visible light, and infrared light, and when described in terms of the wavelength of light as electromagnetic waves, it includes electromagnetic waves with wavelengths of 10 nm to 20,000 nm (electromagnetic waves of 0.01 μm to 20 μm). The solar spectrum exists in the wavelength range from 300 nm to 4000 nm, and the intensity increases as the wavelength increases from 400 nm, and is particularly strong in the wavelength range from 500 nm to 1800 nm.

[0050] In this embodiment, the laminated resin layer M is configured so that the arithmetic mean transmittance, which is the wavelength average of the light transmittance from 400 nm to 800 nm, is 1% or more and 12% or less.

[0051] Therefore, the resin laminate film CP is configured to reflect a portion of the light L incident on the resin laminate film CP at the radiation surface H of the infrared radiation layer J, and to reflect the light (sunlight, etc.) that is transmitted through the infrared radiation layer J out of the light L incident on the resin laminate film CP at the light reflecting layer B and escape to the outside from the radiation surface H.

[0052] The resin laminate film CP is configured to cool an object to be cooled (not shown) located on the opposite side of the light reflecting layer B from the side where the infrared radiation layer J is present (for example, heat input by thermal conduction from the object to be cooled), by converting the heat input into infrared light IR by the infrared radiation layer J and radiating it, thereby cooling the object to be cooled.

[0053] In other words, the resin laminate film CP is configured to reflect light L irradiated onto the resin laminate film CP, and also to radiate heat transferred to the resin laminate film CP (e.g., heat transferred from the atmosphere or from an object to be cooled) to the outside as infrared light IR. Furthermore, the infrared emitting layer J and the light reflecting layer B are flexible, so that the laminated resin film CP (radiative cooling film) is configured to be flexible.

[0054] The light reflecting layer B and the infrared emitting layer J are connected by a connecting layer S made of at least one of an adhesive, a pressure sensitive adhesive, and a glue. Although not shown, the connecting layer S contains at least one of a filler and a hollow particle, which can improve the reflectance of light in the ultraviolet to visible region, and can reduce the thickness of the laminated resin layer M (particularly the light reflecting layer) to obtain a desired reflectance. Here, the filler and hollow particles that can be used preferably have an arithmetic mean particle size of about 0.1 μm to 5 μm. Examples of the filler include titanium oxide, glass microbeads, Diacid Silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminium silicate RumiGranulated one or more of the following can be suitably used: calcium carbonate, heavy calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate. This improves the reflectance of light in the ultraviolet to visible region, and reduces the thickness of the laminated resin layer M (particularly the light reflecting layer B) to obtain a desired reflectance.

[0055] In addition, the resin laminate film CP is used to implement a radiative cooling method in which infrared light IR is radiated from a radiation surface H on the opposite side to the surface of the infrared radiating layer J that is in contact with the light reflecting layer B. Specifically, the radiation surface H is directed toward the sky, and infrared light IR is radiated from the radiation surface H directed toward the sky.

[0056] [Infrared radiation layer] The first resin forming the infrared radiation layer J preferably contains an ultraviolet absorbing agent, and the infrared emitting layer J preferably has an arithmetic mean reflectance, which is the wavelength average of the ultraviolet reflectance from 340 nm to 400 nm, of 50% or less. As the ultraviolet absorbing agent, a benzotriazole-based ultraviolet absorbing agent, a triazine-based ultraviolet absorbing agent, a hindered amine-based stabilizer, a benzophenone-based ultraviolet absorbing agent, a cyanoacrylate-based ultraviolet absorbing agent, a salicylate-based ultraviolet absorbing agent, an oxanilide-based ultraviolet absorbing agent, or the like can be suitably used, and in particular, a benzotriazole-based ultraviolet absorbing agent, a triazine-based ultraviolet absorbing agent, or a hindered amine-based stabilizer is particularly preferred because it can absorb ultraviolet rays up to the long wavelength side. In addition, it is preferable that the first resin contains at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate, and more preferably contains at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

[0057] The first resin forming the infrared radiation layer J can be a colorless resin material containing a carbon-fluorine bond (CF), a carbon-chlorine bond (C-Cl), a carbon-oxygen bond (CO), an ester bond (R-COO-R), an ether bond (COC bond), or a benzene ring. For each resin material (excluding carbon-oxygen bonds), the wavelength ranges in which they have an absorption coefficient in the atmospheric window wavelength band are shown in Figure 3.

[0058] According to Kirchhoff's law, emissivity (ε) and light absorptance (A) are equal. Light absorptance can be calculated from the absorption coefficient (α) using the relation A=1-exp(-αt) (hereafter referred to as the light absorptance relation). Here, t is the film thickness. In other words, by adjusting the film thickness of the infrared radiative layer J, a large thermal radiation can be obtained in a wavelength band with a large absorption coefficient. When performing radiative cooling outdoors, it is recommended to use a material with a large absorption coefficient in the wavelength band of the atmospheric window, that is, from 8 μm to 13 μm. In addition, to suppress the absorption of sunlight, it is advisable to use a material that has no or has a small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, especially in the range of 0.4 μm to 2.5 μm. As can be seen from the relational equation between the absorption coefficient and the absorptance, the light absorptance (emissivity) changes depending on the film thickness of the resin material.

[0059] In order to lower the temperature below the surrounding atmosphere by radiative cooling in a solar radiation environment, if a material is selected that has a large absorption coefficient in the wavelength band of the atmospheric window and almost no absorption coefficient in the wavelength band of sunlight, then by adjusting the film thickness, it will absorb almost no sunlight but emit a lot of thermal radiation from the atmospheric window, meaning it is possible to create a state in which the output from radiative cooling is greater than the input of sunlight.

[0060] Regarding carbon-fluorine bonds (CF), the absorption coefficients due to CHF and CF2 are widely distributed over a wide band from 8 μm to 13 μm, which is the atmospheric window, with the absorption coefficient being particularly large at 8.6 μm. In addition, regarding the solar wavelength band, there is no noticeable absorption coefficient in the wavelength range from 0.3 μm to 2.5 μm, where the energy intensity is high.

[0061] Resin materials having carbon-fluorine bonds (CF) include: One example is polyvinylidene fluoride (PVDF), a partially fluorinated resin. In the following description, polyvinylidene fluoride may be referred to as vinylidene fluoride resin, but the two terms refer to the same material. The same applies to other resins.

[0062] For carbon-chlorine bonds (C-Cl), the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. Resin materials include polyvinyl chloride (PVC) and polyvinylidene chloride (PVDC). In the case of polyvinyl chloride, due to the electron-withdrawing effect of chlorine, an absorption coefficient originating from the bending vibration of CH of the alkene contained in the main chain appears at a wavelength of around 10 μm.

[0063] Ester bonds (R-COO-R) and ether bonds (COC bonds) have absorption coefficients in the wavelength range of 7.8 μm to 9.9 μm. In addition, the carbon-oxygen bonds contained in ester bonds and ether bonds have strong absorption coefficients in the wavelength range of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, absorption appears over a wide wavelength range from 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements caused by the influence of the benzene ring.

[0064] Resins having these bonds include ethylene terephthalate resins, ethylene naphthalate resins, and polymethyl methacrylate resins.

[0065] [Optical absorption considerations] Let us consider the light absorption in the ultraviolet-visible region of resin materials with the bonds and functional groups described above, that is, sunlight absorption. The origin of the absorption of ultraviolet to visible light is the transition of electrons that contribute to the bonds. Absorption in this wavelength range can be understood by calculating the bond energy. First, let us consider the wavelengths at which resin materials with carbon-fluorine bonds (CF) have absorption coefficients in the ultraviolet to visible range. The bond energies of the CC, CH, and CF bonds in the basic structure of polyvinylidene fluoride (PVDF) 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 absorb light of these wavelengths.

[0066] Since the solar spectrum only contains wavelengths longer than 0.300μm, when fluororesin is used, it hardly absorbs the ultraviolet, visible, or near-infrared rays of sunlight. Note that ultraviolet rays are defined as wavelengths shorter than 0.400μm, visible light as wavelengths from 0.400μm to 0.800μm, near-infrared rays as wavelengths from 0.800μm to 3μm, mid-infrared rays as wavelengths from 3μm to 8μm, and far-infrared rays as wavelengths longer than 8μm.

[0067] Regarding the carbon-chlorine bond (C-Cl), the bond energy between the carbon and chlorine in an alkene is 3.28 eV, and the wavelength is 0.378 μm, so it absorbs a lot of ultraviolet light in sunlight, but has almost no absorption in the visible range. FIG. 4 shows the absorption spectrum of a 100 μm thick polyvinyl chloride resin in the ultraviolet to visible range, and light absorption increases at wavelengths shorter than 0.38 μm. FIG. 4 shows the absorptance spectrum from ultraviolet to visible light for a 100 μm thick vinylidene chloride resin, and shows a slight increase in the absorptance spectrum on the shorter wavelength side than 0.4 μm.

[0068] Resins with ester bonds (R-COO-R), ether bonds (COC bonds), and benzene rings include methyl methacrylate resin, ethylene terephthalate resin, and ethylene naphthalate resin. For example, the bond energy of the C-C bond in acrylic is 3.93 eV, and it absorbs sunlight with wavelengths shorter than 0.315 μm, but has almost no absorption in the visible range.

[0069] As an example of a resin material having these bonds and functional groups, the absorption spectrum from ultraviolet to visible light of a 5 mm-thick methyl methacrylate resin is shown in Figure 4. The methyl methacrylate resin shown is a commonly available product on the market, and contains a benzotriazole-based ultraviolet absorber. Because the plate is 5 mm thick, the wavelengths with small absorption coefficients are also large, and light absorption is greater on the shorter wavelength side than 0.38 μm, which is longer than the wavelength of 0.315.

[0070] As an example of a resin material having these bonds and functional groups, the absorption spectrum from ultraviolet to visible light of a 40 μm-thick ethylene terephthalate resin is shown in FIG. As shown in the figure, the absorptance increases as the wavelength approaches 0.315 μm, and the absorptance increases sharply at a wavelength of 0.315 μm. Note that with ethylene terephthalate resin, as the thickness is increased, the absorptance due to the absorption edge derived from the C-C bond increases slightly longer than the wavelength of 0.315 μm, and the absorptance of ultraviolet light increases in the same way as with methyl methacrylate resin.

[0071] As long as the infrared radiation layer J uses a resin material having the above-mentioned emissivity (light emissivity) and light absorptivity characteristics, it may be a single layer film of one type of resin material, a multilayer film of multiple types of resin materials, a single layer film of a resin material in which multiple types of resin materials are blended, or a multilayer film of a resin material in which multiple types of resin materials are blended. The blends include copolymers such as alternating copolymers, random copolymers, block copolymers and graft copolymers, as well as modified products with substituted side chains.

[0072] [Emissivity of polyvinyl chloride resin and vinylidene chloride resin] Figure 5 shows the emissivity of polyvinyl chloride resin (PVC) at the atmospheric window as a representative example of resin with carbon-chlorine bonds, and Figure 6 shows the emissivity of polyvinylidene chloride resin (PVDC) at the atmospheric window. For carbon-chlorine bonds, the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. In the case of polyvinyl chloride resin, the absorption coefficient due to the bending vibration of CH of the alkene contained in the main chain appears at a wavelength of around 10 μm due to the electron-withdrawing effect of chlorine. The same is true for vinylidene chloride resin. Due to these effects, the wavelength average of the emissivity of a 10 μm thick film is 43% at wavelengths from 8 μm to 13 μm, which falls within the regulation of a wavelength average of 43% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0073] [Emissivity of ethylene terephthalate resin] Figure 7 shows the emissivity of ethylene terephthalate resin at the atmospheric window as a representative example of a resin having an ester bond or a benzene ring. Ester bonds have an absorption coefficient in the wavelength range from 7.8 μm to 9.9 μm. Furthermore, the carbon-oxygen bonds contained in ester bonds have a strong absorption coefficient in the wavelength range from 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, absorption appears in a wide range from 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements caused by the influence of the benzene ring. Due to these effects, the wavelength average of the emissivity of a 10 μm thick film is 71% at wavelengths from 8 μm to 13 μm, which falls within the regulation of a wavelength average of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0074] [Surface temperature of light reflecting layer and infrared emitting layer] Thermal radiation from the atmospheric window of the infrared radiation layer J occurs near the surface of the resin material. As can be seen from Figure 5, in the case of polyvinyl chloride resin, even if the thickness exceeds 100 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of polyvinyl chloride resin, thermal radiation in the atmospheric window occurs within a depth of about 100 μm from the surface, and radiation from deeper parts does not escape to the outside. From FIG. 6, it can be seen that vinylidene chloride resin is similar to vinyl chloride resin.

[0075] As shown in Fig. 7, in the case of ethylene terephthalate resin, even if the thickness exceeds 125 μm, there is almost no increase in thermal radiation in the air window region. In other words, in the case of ethylene terephthalate resin, thermal radiation in the air window occurs at a depth of about 100 μm from the surface, and radiation from deeper parts does not escape to the outside.

[0076] As described above, the thermal radiation from the atmospheric window region generated from the surface of the resin material occurs within a depth of approximately 100 μm from the surface. If the resin thickness increases beyond this, the cold generated by radiation cooling of the resin laminate film is insulated by the resin material that does not contribute to thermal radiation. Ideally, the infrared emitting layer J is made of a first resin that does not absorb any sunlight, and the infrared emitting layer J is fabricated on the light reflecting layer B. In this case, sunlight is absorbed only by the light reflecting layer B of the resin laminate film CP. The thermal conductivity of resin materials is generally about 0.2 W / m / K. When calculations are made taking this thermal conductivity into consideration, if the thickness of the infrared emitting layer J exceeds 20 mm, the temperature of the cooling surface (the surface of the light reflecting layer B opposite the side where the infrared emitting layer J is present) will rise.

[0077] Even if an ideal resin material that does not absorb any sunlight exists, the thermal conductivity of the first resin of the infrared radiation layer J is generally about 0.2 W / m / K, so if the thickness exceeds 20 mm as shown in Figure 8, the light reflecting layer B will be heated by the sunlight, and the object to be cooled placed on the side of the light reflecting layer B will be heated. In other words, the thickness of the first resin of the infrared radiation layer J needs to be 20 mm or less.

[0078] Figure 8 is a plot of the surface temperature of the radiative surface H of the resin laminated film (radiative cooling film) and the temperature of the light-reflecting layer B, calculated assuming a clear day in the south in summer in western Japan. The sunlight is AM1.5, and the average value of the solar radiation intensity during the day in summer is 350 W / m 2 The outside temperature is 30°C, and the radiant energy varies depending on the temperature, but is 100 W at 30°C. This calculation assumes that no sunlight is absorbed by infrared radiation layer J. It is assumed that there is no wind, and the convective heat transfer coefficient is 5 W / m2 / K.

[0079] [Light absorption of hydrocarbon resins] When the resin material (first resin, second resin) is a resin whose main chain is a hydrocarbon having one or more carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, or benzene rings, in addition to the ultraviolet absorption due to the covalent bond electrons mentioned above, absorption due to vibrations such as bond bending and stretching is observed in the near-infrared region.

[0080] Specifically, the absorption due to the reference tones of the transitions to the first excited state of CH3, CH2, and CH appears at wavelengths of 1.6 μm to 1.7 μm, 1.65 μm to 1.75 μm, and 1.7 μm, respectively. Furthermore, the absorption due to the reference tones of the combination tones of CH3, CH2, and CH appears at wavelengths of 1.35 μm, 1.38 μm, and 1.43 μm, respectively. Furthermore, the overtones of the transitions to the second excited state of CH2 and CH appear at around 1.24 μm. The reference tones of the bending and stretching of the CH bond are distributed over a wide band from 2 μm to 2.5 μm.

[0081] Furthermore, when an ester bond (R-COO-R) or an ether bond (COC) is present, a large optical absorption occurs at a wavelength of around 1.9 μm. According to the above-mentioned relational expression of light absorptance, the light absorptance caused by these factors becomes small and inconspicuous when the film thickness of the resin material is thin, but becomes large when the film thickness is thick.

[0082] FIG. 9 shows the relationship between the light absorptance and the spectrum of sunlight when the film thickness of ethylene terephthalate resin having an ester bond and a benzene ring is changed. As shown in the figure, as the film thickness increases from 25 μm to 125 μm to 500 μm, the optical absorption in the wavelength range longer than 1.5 μm caused by the respective vibrations increases. In addition, the light absorption increases not only on the long wavelength side but also from the ultraviolet region to the visible region. This is due to the broadening of the light absorption edge caused by chemical bonds.

[0083] When the film thickness is thin, the light absorption rate is high at the wavelength with the largest absorption coefficient, but when the film thickness is thick, the weak absorption coefficient at the absorption edge with a broader spread appears as the absorption rate according to the above-mentioned light absorption rate relational expression. As a result, the light absorption increases from the ultraviolet region to the visible region as the film thickness increases. Regarding reflectance, if the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 400 nm to 800 nm, is 80% or more, and the arithmetic mean reflectance, which is the wavelength average of the light reflectance at wavelengths from 800 nm to 1200 nm, is 43% or more, then if the solar energy absorption energy is 350 W / m and the wavelength average of the emissivity at wavelengths from 8 μm to 13 μm is 43% or more, 2 For absorption of 85W / m 2 If the emissivity is 43% or more, the radiation can be suppressed to about 200 W / m on a day with good atmospheric conditions. 2 For radiation of about 85W / m 2 In other words, the laminated resin layer including the light reflecting layer and the infrared emitting layer preferably has an arithmetic mean reflectance of 80% or more, which is the wavelength average of the light reflectance at wavelengths of 400 nm to 800 nm, an arithmetic mean reflectance of 70% or more, which is the wavelength average of the light reflectance at wavelengths of 800 nm to 1200 nm, and an average of the emissivity at wavelengths of 8 μm to 13 μm, which is 43% or more.

[0084] By having the light-reflecting layer B exhibit a reflectance of 80% or more from 400nm to 800nm ​​and a reflectance of 70% or more from 800nm ​​to 1200nm, the solar energy absorbed by the light-reflecting layer B in the radiative cooling device (radiative cooling film) can be reduced to 25% or less, i.e., the solar energy absorbed at noon in summer can be reduced to about 85W. In addition, when humidity is high, the atmospheric window narrows, but even if radiation drops to about 125W / m2, for example, if the emissivity is 70% or more, it is desirable because it is possible to emit more energy than solar energy.

[0085] As mentioned above, the maximum value of infrared radiation in the wavelength band of the atmospheric window in the summer in lowlands of Japan is about 160 W at 30°C on a day with good atmospheric conditions, and usually about 125 W. If the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B are both ethylene terephthalate resin, which is a hydrocarbon resin, and the thickness of each is 500 μm, the sum of the solar light absorption of the laminated resin layer M (both the infrared emitting layer J and the light reflecting layer B) is 176 W / m 2 It becomes. From the above, when the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B are both made of ethylene terephthalate resin, which is a hydrocarbon-based resin, the film thickness of each of the infrared emitting layer J and the light reflecting layer B is 500 μm or more, that is, when the film thickness of the laminated resin layer M is 1000 μm or more, the radiative cooling performance is not exhibited. In other words, the thickness of the first resin of the infrared emitting layer J and the thickness of the second resin of the light reflecting layer B are each preferably 500 μm or less. The thickness of the first resin of the infrared emitting layer J and the thickness of the second resin of the light reflecting layer B are each preferably 10 μm or more, and the lower limit of the film thickness is determined from the viewpoint of ensuring infrared emissivity and light reflectivity.

[0086] [Light absorption of blended resins] When the resin material (first resin, second resin) is a blend of a resin having a carbon-fluorine bond as its main chain and a resin having a hydrocarbon as its main chain, light absorption in the near-infrared region caused by CH, CH2, CH3, etc. appears according to the ratio of the blended resin having a hydrocarbon as its main chain. When the main component is carbon-fluorine bonds, the light absorption in the near infrared region caused by hydrocarbons is small, so the thickness can be increased up to the upper limit of 20 mm from the viewpoint of thermal conductivity. However, when the main component is a blended hydrocarbon resin, the thickness of each of the first resin and the second resin must be 500 μm or less.

[0087] The blend of fluororesin and hydrocarbon also includes those in which the fluororesin is substituted with a hydrocarbon, and alternating copolymers, random copolymers, block copolymers and graft copolymers of a fluoromonomer and a hydrocarbon monomer.

[0088] Depending on the molecular weight and ratio of the substituted hydrocarbon side chains, optical absorption in the near infrared region caused by CH, CH2, CH3, etc. appears. When the monomers introduced as side chains or copolymers are low molecular weight, or when the density of the monomers introduced is low, optical absorption in the near infrared region caused by hydrocarbons becomes small, so the thickness can be increased up to 20 mm, which is the limit from the viewpoint of thermal conductivity. When a high molecular weight hydrocarbon is introduced as a side chain of the fluororesin or as a copolymerizable monomer, the thickness of each of the first resin and the second resin must be 500 μm or less.

[0089] [Thickness of the infrared radiation layer] From the viewpoint of practical use of the resin laminate film CP, it is preferable that the thickness of the infrared radiation layer J is thin. The thermal conductivity of resin materials is generally lower than that of metals and glass. In order to effectively cool an object to be cooled, it is preferable that the thickness of the infrared radiation layer J is the minimum necessary. The thicker the infrared radiation layer J is, the greater the thermal radiation of the atmospheric window becomes, and above a certain thickness, the thermal radiation energy of the atmospheric window becomes saturated.

[0090] The thickness at which the film saturates depends on the resin material, but in the case of fluororesin, 300 μm is generally sufficient for saturation. Therefore, from the perspective of thermal conductivity, it is preferable to keep the film thickness at 300 μm or less rather than 500 μm. Furthermore, although thermal radiation is not saturated, even a thickness of around 100 μm can provide sufficient thermal radiation in the atmospheric window region. The thinner the thickness, the higher the thermal conductivity and the more effectively the temperature of the object being cooled can be lowered, so in the case of fluororesin, it is best to keep the thickness at around 100 μm or less.

[0091] The absorption coefficients due to carbon-silicon bonds, carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds are greater than the absorption coefficient due to C-F bonds. Naturally, from the viewpoint of thermal conductivity, it is preferable to keep the film thickness to 300 μm or less rather than 500 μm, but an even greater radiative cooling effect can be expected if the film thickness is made even thinner to increase thermal conductivity. In the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, even a thickness of 100 μm is saturated, and even a thickness of 50 μm provides sufficient thermal radiation in the atmospheric window region. The thinner the resin material, the higher the thermal transmittance and the more effectively the temperature of the object to be cooled can be lowered, so in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, a thickness of 50 μm or less reduces the insulation and allows the object to be cooled effectively. In the case of carbon-chlorine bonds, a thickness of 100 μm or less allows the object to be cooled effectively.

[0092] The benefit of making the film thinner is not just that it reduces heat insulation and makes it easier to transfer heat. It also reduces the absorption of near-infrared light from CH, CH2, and CH3, which are caused by resins that contain carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds. By making the film thinner, the amount of sunlight absorbed by these bonds can be reduced, which increases the cooling ability of the resin laminate film CP. From the above perspective, in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0093] In the case of carbon-silicon bonds, even at a thickness of 50 μm, thermal radiation is saturated in the atmospheric window region, and even at a thickness of 10 μm, sufficient thermal radiation can be obtained in the atmospheric window region. The thinner the infrared radiation layer J, the higher the thermal transmittance and the more effectively the temperature of the object to be cooled can be lowered, so in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less reduces the insulating properties and allows the object to be cooled to be cooled effectively. Making the film thinner reduces solar absorption, thereby increasing the cooling ability of the resin laminate film CP. From the above perspective, in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0094] As described later, in the resin laminate film CP according to this embodiment, a resin is also used for the light reflecting layer B. Although the light reflecting layer B contains voids K at a certain volumetric ratio, a certain amount of heat radiation can be expected. In consideration of this point, it is preferable to further reduce the thickness of the infrared radiation layer J described above.

[0095] [Details of the light reflecting layer] The light reflecting layer B has the above-mentioned reflection characteristics (reflection characteristics as the laminated resin layer M) by making the refractive index of the second resin forming the light reflecting layer different from the refractive index of the material inside the multiple holes K contained in the second resin. Specifically, the second resin of the light reflecting layer B preferably contains at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate. On the other hand, polyimide and bakelite are not desirable as the second resin of the light reflecting layer B because the resin itself is easily colored and the reflectance is easily reduced.

[0096] Furthermore, various gases or fluids can be contained inside the pores K of the second resin of the light reflecting layer B, but air is preferably contained inside. The refractive index of the pores K (more specifically, the gas or fluid contained in the pores K) is smaller than that of the second resin. In addition, it is preferable that the arithmetic mean diameter of the holes K is 0.1 μm or more and 3.0 μm or less. In this embodiment, the arithmetic mean diameter of the holes K is short It is understood to mean the arithmetic mean of the inside diameter. The shape of the hole K can be various shapes such as spherical or elliptical, but from the viewpoint of improving light reflectance, it is preferable that it be flat, and more preferably, the long axis of the hole K is aligned in the direction along the film surface (radiating surface H) of the resin laminate film CP. Furthermore, the volume fraction of the voids K in the light reflecting layer B is preferably 0.1 volume % or more and 60 volume % or less, more preferably 1 volume % or more and 50 volume % or less, and more preferably 10 volume % or more and 40 volume % or less.

[0097] Furthermore, as a result of the inventor's intensive study, the thickness of the second resin of the light reflecting layer B is preferably 10 μm or more and 500 μM or less. By making the thickness of the second resin of the light reflecting layer B 10 μm or more, the light reflecting layer B made of the second resin having a plurality of pores K can satisfactorily secure the reflectance required for radiation cooling. In addition, by making the thickness 500 μm or less, the heat insulating effect of the second resin having the pores K containing air or the like can be made to be below a certain level, and the cooling performance of the object to be cooled can be secured to a certain level or more. The thickness of the second resin of the light reflecting layer B is preferably 50 to 300 um, and more preferably 75 to 200 um. When the thickness is 500 μm or more, the thermal conductivity in the thickness direction decreases and the heat insulating property becomes strong, so that when applied to a housing having a heat source inside, the heat storage in the housing increases, which is not preferable from the viewpoint of heat radiation.

[0098] 2, the resin laminate film CP may contain a filler F (F1, F2) in the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B. The filler F (F1, F2) may be contained in at least one of the first resin forming the infrared emitting layer J and the second resin forming the light reflecting layer B. The filler F (F1, F2) can be one or more of titanium oxide, glass microbeads, silicon dioxide, ground calcium carbonate powder, barium sulfate, zinc sulfate, aluminum silicate, ground calcium carbonate, aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, magnesium oxide, and barium titanate, and the filler F1 contained in the first resin and the filler F2 contained in the second resin may be different materials.

[0099] [Experimental Results] For the examples and comparative examples of the laminated resin film described above, various tests were carried out on antifouling properties, ultraviolet reflectance, reflectance at wavelengths of 400 nm to 800 nm, reflectance at wavelengths of 800 nm to 1200 nm, transmittance at wavelengths of 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic wave transmittance, and the results are shown in the following Tables 1 to 4. In the test results shown in the tables, the underlined parts indicate that the conditions of the various tests were not met. Incidentally, Tables 1 to 4 also show various conditions for the films constituting the Examples and Comparative Examples.

[0100] The stain resistance was evaluated by performing a one-month outdoor exposure test in Osaka City, using the color difference ΔE before and after, and a value of ΔE<2.0 was defined as high (good) stain resistance. Note that the color difference ΔE refers to the "CIEDE2000 color difference" based on JIS Z8781.

[0101] The UV reflectance was evaluated using the arithmetic mean of the reflectance at wavelengths from 340 nm to 400 nm measured with a UV-Visible spectrometer UV-2600 (Shimadzu Corporation). A reflectance of 50% or less was defined as meeting the condition (low UV reflectance).

[0102] The reflectance in the wavelength range of 400 to 800 nm was evaluated using the arithmetic mean of the reflectance in the wavelength range of 400 to 800 nm measured with an ultraviolet-visible spectrometer UV-2600 (Shimadzu Corporation). A reflectance of 80% or more was defined as satisfying the condition (high reflectance in the wavelength range of 400 to 800 nm).

[0103] The reflectance in the wavelength range of 800 nm to 1200 nm was evaluated using the arithmetic mean of the reflectance in the wavelength range of 800 nm to 1200 nm measured with an ultraviolet-visible spectrometer UV-2600 (manufactured by Shimadzu Corporation). A reflectance of 70% or more was defined as satisfying the condition (high reflectance in the wavelength range of 800 nm to 1200 nm).

[0104] The transmittance from 400 to 800 nm was evaluated using the arithmetic mean of the transmittance from 400 to 800 nm measured with a UV-Visible spectrometer UV-2600 (Shimadzu Corporation). A transmittance of 1% or more was defined as satisfying the condition (having a high transmittance from 400 to 800 nm).

[0105] The infrared emissivity was evaluated using the arithmetic mean of the emissivity at wavelengths from 8 μm to 13 μm measured with an FT-IR IR Tracker-100 (Shimadzu Corporation). Products with an emissivity of 70% or more were defined as meeting the condition (high reflectance at wavelengths from 400 nm to 800 nm).

[0106] Thermal conductivity was measured using the laser flash method defined in JIS R1611, and materials with a thermal conductivity of 0.3 W / m·K or higher were defined as having high (good) thermal conductivity.

[0107] Xenon weather resistance is measured in the xenon weather resistance test defined in JIS K5600, where the black panel temperature (BPT) is 63°C and the UV intensity is 180W / m 2 The sample was exposed to ultraviolet light for 3000 hours, and the color difference ΔE between before and after the test was measured. Samples with ΔE<2.0 were defined as having high (good) weather resistance.

[0108] The radio wave transmittance was measured at 800MHz using the KEC method at the Kansai Electronics Industry Development Center, a general incorporated association. A radio wave transmittance of 10dB or less was defined as high (good) radio wave transmittance.

[0109] In the table, PET stands for polyethylene terephthalate, PEN stands for polyethylene naphthalate, PVC stands for polyvinyl chloride, PVDC stands for polyvinylidene chloride, PVDF stands for polyvinylidene fluoride, and PP stands for polypropylene.

[0110] The sample of Example 1 was prepared by forming a thin film of PVC resin containing TiO2 by a calendaring method, and bonding it to a PET film containing TiO2 by a dry lamination method.

[0111] [Table 1]

[0112] [Table 2]

[0113] [Table 3]

[0114] [Table 4]

[0115] As shown by the above experimental results, the resin laminate films CP according to Examples 1 to 16 of the present invention satisfy the specified conditions in terms of antifouling properties, ultraviolet reflectance, reflectance at wavelengths of 400 nm to 800 nm, reflectance at wavelengths of 800 nm to 1200 nm, transmittance at wavelengths of 400 nm to 800 nm, infrared emissivity, thermal conductivity, xenon weather resistance, and electromagnetic wave transmittance.

[0116] On the other hand, in Comparative Examples 1 to 4, a relatively large number of pores K are formed in the infrared emitting layer J as a surface layer, so that the antifouling condition is not satisfied and dirt easily adheres thereto. In Comparative Examples 1 and 5, since the second resin as the light reflecting layer B is not provided, the conditions regarding the reflectance at wavelengths of 400 nm to 800 nm and the reflectance at wavelengths of 800 nm to 1200 nm are not satisfied, resulting in low reflectance. In Comparative Example 6, PET vapor-deposited with metallic silver is used as the light-reflecting layer B, so the condition for transmittance at wavelengths of 400 nm to 800 nm is not met, resulting in poor light gathering properties and not meeting the condition for radio wave transmittance. In Comparative Examples 1 and 5, the infrared emissivity does not satisfy the conditions because the second resin as the light reflecting layer B is not provided, and it is presumed that the second resin as the light reflecting layer B contributes to the infrared emissivity to a certain extent. In Comparative Examples 2 and 4, it is presumed that the infrared emissivity conditions are not satisfied because a plurality of holes K are provided in the relatively thin 100 μm infrared emitting layer J. In Comparative Examples 3 and 4, the resin layer having voids K was thick and the thermal conductivity of the material as a whole was low, so the thermal conductivity condition was not met. In Comparative Examples 1 to 5, the weather resistance of the PET against ultraviolet light was insufficient, and when the xenon weather resistance was evaluated, yellowing occurred, so the xenon weather resistance condition was not met.

[0117] [Another embodiment] (1) A configuration may be adopted in which the radiation surface H of the infrared radiation layer J is protected by a protective layer (not shown). The protective layer may be made of a material such as fluorine or acrylic fluorine, and the thickness of the protective layer is preferably about 0.1 μm or more and 100 μm or less. The material may be polyethylene or polypropylene, which has a low emissivity at the atmospheric window. The protective layer has a function of preventing dirt and scratches, and also serves as a sacrificial layer.

[0118] (2) A connecting resin layer may be provided on the side of the reflective layer B opposite to the infrared radiation layer J. As an example, the connecting resin layer may be a connecting layer made of polyvinyl chloride, which allows suitable connection to a polyvinyl chloride film material, a tarpaulin, or a steel plate.

[0119] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, provided that no contradiction arises. Furthermore, the embodiments disclosed in this specification are merely examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0120] The resin laminate film of the present invention can exhibit high cooling capacity under direct sunlight and high radio wave transmittance, and is capable of suppressing the deterioration of radiative cooling performance when holes are provided in the resin material. Down The resin laminate film can be effectively used to prevent such defects. [Explanation of symbols]

[0121] B: Light reflective layer CP: Resin laminated film F: Filler H: Radiation surface IR: Infrared light J: Infrared radiation layer K: Vacancy M: Laminated resin layer S: Connection layer

Claims

1. A resin laminate film comprising an infrared emitting layer that emits infrared light from a emitting surface, and a light reflecting layer located on a side of the infrared emitting layer opposite to a side on which the emitting surface is present, the light reflecting layer has a plurality of pores and is made of a second resin; the infrared radiation layer is made of a first resin that emits thermal radiation energy at a wavelength of 8 μm to 13 μm that is greater than the absorbed solar energy; the infrared emitting layer includes fewer voids than the light reflecting layer includes; a laminated resin layer including the light reflecting layer and the infrared emitting layer has an arithmetic mean reflectance, which is a wavelength average of light reflectance at wavelengths of 400 nm to 800 nm, of 80% or more, an arithmetic mean reflectance, which is a wavelength average of light reflectance at wavelengths of 800 nm to 1200 nm, of 70% or more, and a wavelength average of emissivity at wavelengths of 8 μm to 13 μm, of 43% or more; The thickness of the first resin is 10 μm or more and 500 μm or less, The thickness of the second resin is 10 μm or more and 500 μm or less, The second resin includes at least one of polyethylene terephthalate, polypropylene, polyethylene, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, polymethyl methacrylate, and polycarbonate; The first resin is a resin laminate film containing at least one of polyethylene terephthalate, polyethylene naphthalate, polyvinyl chloride, polyvinylidene chloride, polyvinyl fluoride, polyvinylidene fluoride, and polymethyl methacrylate.

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

3. The pores in the second resin have a refractive index smaller than that of the second resin, 3. The resin laminate film according to claim 1, wherein the pores have an arithmetic mean pore size of 0.1 μm or more and 3.0 μm or less.

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

5. 3. The resin laminate film according to claim 1, wherein a volume ratio of the voids in the light reflecting layer is from 1 volume % to 50 volume %.

6. 3. The resin laminate film according to claim 1, wherein a volume ratio of the voids in the light reflecting layer is 10 volume % or more and 40 volume % or less.

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

8. 3. The resin laminate film according to claim 1, wherein the laminate resin layer has an arithmetic mean transmittance, which is a wavelength average of light transmittance in the wavelength range of 400 nm to 800 nm, of 1% to 12%.

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

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

11. 3. The resin laminate film according to claim 2, wherein the filler is at least one 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.

12. The resin laminate film according to claim 10, wherein the filler is at least one 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.

13. 3. The resin laminate film according to claim 1, wherein the first resin contains at least one of polyvinyl chloride, polyvinylidene chloride, and polyvinylidene fluoride.

14. The first resin contains an ultraviolet absorbing agent, 3. The resin laminate film according to claim 1, wherein the infrared radiation layer has an arithmetic mean reflectance, which is a wavelength average of the reflectance of ultraviolet rays having a wavelength of 340 nm to 400 nm, of 50% or less.

15. 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, The resin laminate film according to claim 1 or 2, wherein the connection layer is included in the laminate resin layer.

16. The resin laminate film according to claim 15 , wherein the connection layer contains at least one of a filler and a hollow particle.

17. The resin laminate film according to claim 1 , wherein the pores in the second resin have a flat shape.

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