Radiation cooling device

Abstract

To provide a radiation cooling film material which prevents a reflection factor from decreasing as time passes for a relatively long period, and prevents radiation performance from lowering while wear resistance of a surface (radiation surface) is maintained.SOLUTION: A radiation cooling film material is provided with a coat layer which has silica as a main component on a presence side of a radiation surface in an infrared radiation layer. A film thickness of the coat layer is between 30 nm and 500 nm, a coating material generating the coat layer dries up mixture dispersing granular silica in alcohol solvent. In the coating material forming the coat layer, a value of (first residual quantity mass-second residual quantity mass) / first residual quantity mass satisfies a condition being between 0.05 and 0.45 in the case that a mass remaining when the coating material in mass before heat drying to be mass before drying is heated at 200°C for a prescribed determination heating time is a first residual quantity mass and a mass remaining when the coating material to be mass before heat drying is heated at 700°C for a determination heating time is a second residual quantity mass.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a radiative cooling device having a radiative cooling effect.

Background Art

[0002] Radiative cooling refers to a phenomenon in which the temperature of a substance decreases by emitting electromagnetic waves such as infrared rays to the surroundings. By utilizing this phenomenon, for example, a radiative cooling layer (radiative cooling device) that cools a cooling target without consuming energy such as electricity can be configured.

[0003] As a conventional example of a radiative cooling layer (radiative cooling device), an infrared radiation layer that emits infrared light from a radiation surface and a light reflection layer that is located on the side opposite to the presence side of the radiation surface in the infrared radiation layer are provided in a laminated state. The infrared radiation layer is formed using a dimethylsiloxane resin, a vinylidene fluoride resin, an acrylic acid resin, or a methyl methacrylate resin, and the light reflection layer is configured in a form including silver or a silver alloy (see, for example, Patent Document 1).

[0004] That is, in the radiative cooling layer (radiative cooling device), the infrared radiation layer emits large thermal radiation energy in the wavelength band of 8 μm to 14 μm, and the light reflection layer reflects the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer and emits it from the radiation surface, so that the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer is not projected onto the cooling target and the cooling target is not heated. Thus, the cooling target can be cooled even in a daytime solar radiation environment.

[0005] In addition, the light reflection layer also has the effect of reflecting the light radiated from the infrared radiation layer to the presence side of the light reflection layer back toward the infrared radiation layer in addition to the light that has passed through the infrared radiation layer. However, in the following description, it will be described on the assumption that the purpose of providing the light reflection layer is to reflect the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer.

Prior Art Documents

Patent Documents

[0006] [Patent Document 1] Japanese Patent Publication No. 2018-526599 [Summary of the Invention] [Problems to be Solved by the Invention]

[0007] When the film material having a radiation cooling layer shown in the above Patent Document 1 is used for a relatively long period of time, problems may occur such as a decrease in reflectivity over time due to foreign matter adhering to the surface (radiation surface), a decrease in reflectivity over time due to yellowing of the infrared radiation layer by ultraviolet rays, or wear of the surface (radiation surface). Therefore, it has been desired to develop a radiation cooling film material that prevents a decrease in reflectivity over time for a relatively long period of time, maintains the abrasion resistance of the surface (radiation surface), and does not reduce the radiation performance.

[0008] The present invention has been made in view of such a situation, and its object is to provide a radiation cooling film material that prevents a decrease in reflectivity over time for a relatively long period of time, maintains the abrasion resistance of the surface (radiation surface), and does not reduce the radiation performance. [Means for Solving the Problems]

[0009] The radiation cooling device of the present invention has a radiation cooling layer attached to the outer surface of a base material, wherein the radiation cooling layer is configured in a form including an infrared radiation layer that radiates infrared light from a radiation surface and a light reflection layer that is located on the side opposite to the side where the radiation surface exists in the infrared radiation layer, the infrared radiation layer is a resin material layer made of vinyl chloride resin or vinylidene chloride resin adjusted to a thickness that emits thermal radiation energy greater than the absorbed solar energy in a band from wavelength 8 μm to wavelength 14 μm, the light reflection layer includes silver or a silver alloy, and a coating layer mainly composed of granular silica is provided on the side where the radiation surface exists in the infrared radiation layer. The layer thickness of the coat layer is 30 nm or more and less than 500 nm, The coat material for forming the coat layer is When the coat material with the mass before drying (mass before heat drying) is heated at 200°C for a predetermined determination heating time, the remaining mass is defined as the first remaining mass, and when the coat material with the mass before heat drying is heated at 700°C for the determination heating time, the remaining mass is defined as the second remaining mass, the value of (first remaining mass - second remaining mass) / first remaining mass satisfies the condition of being 0.05 or more and less than 0.45.

[0010] That is, the sunlight incident from the radiation layer of the infrared radiation layer in the radiative cooling layer passes through the resin material layer, and then is reflected by the light reflection layer on the side opposite to the side where the radiation surface of the resin material layer exists, and escapes from the radiation surface to the outside of the system. In the description of this specification, when simply referred to as light, the concept of the light includes ultraviolet light (ultraviolet rays), visible light, and infrared light. Stated in terms of the wavelength of light as an electromagnetic wave, it includes electromagnetic waves with a wavelength of 10 nm to 20,000 nm (electromagnetic waves of 0.01 μm to 20 μm).

[0011] Also, the heat transfer (heat input) to the radiative cooling layer is converted into infrared rays by the resin material layer as the infrared radiation layer, and escapes from the radiation surface to the outside of the system. In this way, the radiative cooling layer can reflect the sunlight irradiated to the radiative cooling layer, and also radiate the heat transfer to the radiative cooling layer (for example, heat transfer from the atmosphere or heat transfer from the film material cooled by the radiative cooling layer) to the outside of the system as infrared light.

[0012] Also, since the resin material layer is adjusted to a thickness that emits heat radiation energy larger than the absorbed solar light energy in the band from a wavelength of 8 μm to a wavelength of 14 μm, it is possible to appropriately reflect the sunlight with the light reflection layer including silver or a silver alloy, and also exhibit a cooling function even in the daytime solar radiation environment.

[0013] Therefore, even in the daytime solar radiation environment, the radiation cooling layer attached to the outer surface of the film material can cool the film material. As a result, the interior (internal space) of the film material can be cooled by the radiation cooling effect in the daytime solar radiation environment.

[0014] Since the thin-film vinyl chloride resin or vinylidene chloride resin becomes soft by adding a plasticizer, even if it comes into contact with other objects, it can avoid being damaged by changing its shape flexibly according to the other objects, and thus can be maintained in a beautiful state for a long time. Incidentally, since the thin-film fluororesin is hard, it cannot change its shape flexibly due to contact with other objects and is easily damaged, making it difficult to maintain a beautiful state. In addition, by adding a plasticizer to the vinyl chloride-based resin, even if it is damaged, it can be deformed by heating to 80°C or higher to eliminate surface scratches and be smoothed, that is, the scratches can be self-repaired. Fluororesin and silicone rubber do not have this property. Due to this property of the soft vinyl chloride-based resin, a beautiful state can be maintained for a long time. This leads to the maintenance of the radiation cooling performance over a long period. Moreover, since the vinyl chloride-based resin is flame-retardant and difficult to biodegrade, it is suitable as a resin material for forming the resin material layer of the radiation cooling device used outdoors. The vinyl chloride-based resin used in the present invention is a homopolymer of vinyl chloride or vinylidene chloride and a copolymer of vinyl chloride or vinylidene chloride, and its production method is carried out by a conventionally known polymerization method.

[0015] In addition to the thin-film vinyl chloride-based resin being flexible, since a plasticizer is mixed into the vinyl chloride-based resin to make it soft, as a result, the resin material layer has further flexibility, and the radiation cooling device has flexibility.

[0016] Furthermore, as a result of intensive studies, the inventors configured the radiation cooling layer to include, in addition to the infrared radiation layer and the light reflection layer, a coat layer mainly composed of silica on the side where the radiation surface exists in the infrared radiation layer. The thickness of the coat layer was set to be 30 nm or more and less than 500 nm. When the coat material, which is the mass before drying, was heated at 200°C for a predetermined determination heating time, the remaining mass was defined as the first remaining mass, and when the coat material with the mass before heating and drying was heated at 700°C for the determination heating time, the remaining mass was defined as the second remaining mass. By satisfying the condition that the value of (the first remaining mass - the second remaining mass) / the first remaining mass is 0.05 or more and less than 0.45, as shown in the test results described later, it is possible to suppress the adhesion of foreign substances to the surface (radiation surface) over a relatively long period of time, suppress the decrease in reflectivity over time, suppress the yellowing of the infrared radiation layer due to ultraviolet rays and suppress the decrease in reflectivity over time, and improve the abrasion resistance of the surface (radiation surface) while maintaining the radiation cooling function.

[0017] In addition, by using silica as the main component of the coat material, from the viewpoint of improving antifouling properties, it is possible to obtain the effect of suppressing the decrease in reflectivity due to dirt. Also, since the silica absorbs (or reflects) ultraviolet rays with a wavelength of about 300 nm to 400 nm, it is possible to suppress the discoloration of the infrared radiation layer due to ultraviolet rays. Here, although it is conceivable to use titania or fluorine as the main component of the coat layer, titania has the demerits that haze tends to increase and the absorption of ultraviolet rays and visible light tends to increase, and fluorine has the demerit that the cleaning property of dirt by running water such as rainwater is low. Therefore, they are not suitable as the main component of the coat layer.

[0018] By making the coating layer mainly composed of silica and having organic terminal groups, the inventors can suppress the adhesion of foreign substances to the surface (radiating surface) and can exhibit the effect of suppressing the decrease in reflectance over time. By setting the value of (first remaining mass - second remaining mass) / first remaining mass to 0.45 or less, the average emissivity of the surface in the range of 8 to 13 μm can be made 0.95 or more. By setting the value of (first remaining mass - second remaining mass) / first remaining mass to 0.05 or more, the abrasion resistance of the surface (radiating surface) can be improved. By setting the film thickness to 30 to 500 nm, it has been experimentally confirmed that yellowing of the infrared radiation layer due to ultraviolet rays can be suppressed and a decrease in reflectance over time can be suppressed.

[0019] Furthermore, adding an explanation, the coating layer can adsorb moisture in the air on the upper surface of the coating layer to form a water film. As a result, even when new dirt components come into contact from the outside, they will float on the formed water film. Consequently, when water splashes from the outside such as rainwater on the upper surface of the coating layer, the splashed water will affinity with the water under the dirt, floating the dirt from the coating layer and making it easy for the dirt to fall off. Furthermore, when there is a lot of water splash from the outside and a water flow is formed on the upper surface of the coating layer, the dirt will be washed away along with the water flow, thereby suppressing a decrease in reflectance due to the adhesion of dirt.

[0020] In short, according to the characteristic configuration of the radiative cooling device of the present invention, it is possible to provide a radiative cooling film material that can prevent the reflectance from decreasing over time for a relatively long period, maintain the abrasion resistance of the surface (radiating surface), and also prevent the radiative performance from decreasing.

[0021] A further characteristic configuration of the radiative cooling device of the present invention is that the radiative cooling layer is mounted on the outer surface of the film material by an adhesive or adhesive connection layer.

[0022] That is, the radiative cooling layer can be accurately mounted in a state of being adhered to the outer surface of the flexible film material by an adhesive or adhesive connection layer. Incidentally, the outer surface of the film material is generally formed in a state with unevenness rather than a mirror surface. However, since the radiation cooling layer is connected to the outer surface of the film material by the connection layer of the adhesive or the pressure-sensitive adhesive, it is possible to suppress the reflection of the unevenness of the outer surface of the film material on the light reflection layer and maintain the light reflection layer in a flat state.

[0023] That is, if the unevenness of the outer surface of the film material is reflected on the light reflection layer, the reflectance of the light reflection layer will decrease due to the scattering of light caused by the unevenness of the outer surface of the film material, resulting in a state where light is absorbed. However, by maintaining the light reflection layer in a flat state, it is possible to suppress the decrease in the reflectance of the light reflection layer.

[0024] In short, according to a further characteristic configuration of the radiation cooling device of the present invention, it can be accurately mounted in a state where the radiation cooling layer is in close contact with the outer surface of the flexible film material.

[0025] A further characteristic configuration of the radiation cooling device of the present invention is that the film thickness of the resin material layer is The wavelength average of the light absorption rate from a wavelength of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from a wavelength of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the light absorption rate from a wavelength of 0.8 μm to 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less. It has light absorption characteristics, and It is adjusted to a thickness in a state having thermal radiation characteristics in which the wavelength average of the emissivity from 8 μm to 14 μm is 40% or more.

[0026] In addition, the wavelength average of the light absorption rate from a wavelength of 0.4 μm to 0.5 μm means the average value of the light absorption rate for each wavelength in the range from 0.4 μm to 0.5 μm. The same applies to the wavelength average of the light absorption rate from a wavelength of 0.5 μm to 0.8 μm, the wavelength average of the light absorption rate from a wavelength of 0.8 μm to 1.5 μm, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm. Also, other similar descriptions including the emissivity mean the same average value, and the same applies hereinafter in this specification.

[0027] That is, the light absorption rate and emissivity (light emission rate) of the resin material layer change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer so that it does not absorb sunlight as much as possible and emits a large amount of thermal radiation in the wavelength band in the so-called atmospheric window region (the region with a light wavelength of 8 μm to 20 μm).

[0028] Specifically, from the perspective of the light absorption rate (light absorption characteristics) of sunlight in the resin material layer, the wavelength average of the light absorption rate at a wavelength of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate at a wavelength of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the light absorption rate from a wavelength of 0.8 μm to a wavelength of 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm needs to be 40% or less. Note that for the light absorption rate from 2.5 μm to 4 μm, the wavelength average only needs to be 100% or less. When such a light absorption rate is distributed, the light absorption rate of sunlight becomes 10% or less, and in terms of energy, it becomes 100 W or less.

[0029] That is, the light absorption rate of sunlight increases as the film thickness of the resin material layer increases. When the resin material layer is made into a thick film, the emissivity of the atmospheric window becomes almost 1, and the thermal radiation emitted into space at that time is 125 W / m 2 to 160 W / m 2 and becomes. As described above, the sunlight absorption in the light reflection layer is preferably 50 W / m 2 or less. Therefore, the sum of the sunlight absorption in the resin material layer and the light reflection layer is 150 W / m 2 or less, and cooling progresses if the atmospheric conditions are good. For the resin material layer, it is good to use one with a small absorption rate near the peak value of the sunlight spectrum as described above.

[0030] Also, from the perspective of the emissivity (thermal radiation characteristics) of the resin material layer for emitting infrared light, the wavelength average of the emissivity at a wavelength of 8 μm to 14 μm needs to be 40% or more. That is, 50 W / m absorbed by the light reflection layer 2In order to allow the resin material layer to emit the heat radiation of sunlight to space, the resin material layer needs to emit more heat radiation. For example, when the outside air temperature is 30°C, the maximum heat radiation of the atmospheric window with a wavelength of 8 μm to 14 μm is 200 W / m 2 (calculated with an emissivity of 1). This value can be obtained on a clear day in an environment with thin and dry air such as a high mountain. In lowlands, etc., since the thickness of the atmosphere is thicker than that of a high mountain, the wavelength band of the atmospheric window becomes narrower and the transmittance decreases. Incidentally, this is called "the atmospheric window becomes narrower".

[0031] Also, the environment where a radiative cooling device is actually used may be humid, and in that case too, the atmospheric window becomes narrower. The heat radiation generated in the atmospheric window region when used in lowlands is estimated to be 160 W / m at 30°C in good conditions 2 (calculated with an emissivity of 1). Also, although it is common in Japan, when there is haze in the sky or when smog exists, the atmospheric window becomes even narrower, and the radiation to space becomes about 125 W / m 2 .

[0032] In view of such circumstances, the wavelength average of the emissivity from 8 μm to 14 μm must be 40% or more (the heat radiation intensity in the atmospheric window band is 50 W / m 2 or more) in order to be used in lowlands in the mid-latitude zone. Therefore, by adjusting the thickness of the resin material layer to be within the range of the above-described optical regulations, the heat output in the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and radiative cooling can be performed outdoors even in a daytime solar radiation environment. That is, when the resin material layer is formed of vinyl chloride resin or vinylidene chloride resin, the thickness of the resin material layer is preferably 100 μm or less and 10 μm or more.

[0033] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, the heat output in the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and radiative cooling can be performed outdoors even in a solar radiation environment.

[0034] A further characteristic configuration of the radiative cooling device of the present invention is that the light reflection layer has a reflectivity of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectivity of 96% or more at a wavelength longer than 0.5 μm.

[0035] That is, the solar spectrum exists from a wavelength of 0.295 μm to 4 μm, and as the wavelength increases from 0.4 μm, the intensity increases, and particularly the intensity is high from a wavelength of 0.5 μm to a wavelength of 2.5 μm. When the light reflection layer has a reflection characteristic in which the reflectivity is 90% or more from a wavelength of 0.4 μm to 0.5 μm and the reflectivity of a wavelength longer than 0.5 μm is 96% or more, the light reflection layer absorbs only about 5% or less of the solar energy.

[0036] As a result, at noon in summer, the solar energy absorbed by the light reflection layer can be reduced to 50 W / m 2 or less, and radiative cooling by the resin material layer can be performed well. In this specification, unless otherwise specified, the spectrum of sunlight shall conform to the AM1.5G standard.

[0037] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, absorption of solar energy by the light reflection layer can be suppressed, and radiative cooling by the resin material layer can be performed well.

[0038] A further characteristic configuration of the radiative cooling device of the present invention is that the light reflection layer is made of silver or a silver alloy and has a thickness of 50 nm or more.

[0039] That is, in order to give the light reflection layer the above-described reflectivity characteristics, that is, the reflectivity characteristics in which the reflectivity is 90% or more at a wavelength of 0.4 μm to 0.5 μm and the reflectivity of a wavelength longer than 0.5 μm is 96% or more, the reflection material on the radiation surface side of the light reflection layer needs to be silver or a silver alloy. And when reflecting sunlight with only silver or a silver alloy having the above-described reflectivity characteristics, a thickness of 50 nm or more is required.

[0040] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, the absorption of solar energy by the light reflection layer can be accurately suppressed, and radiative cooling by the resin material layer can be performed well.

[0041] A further characteristic configuration of the radiative cooling device of the present invention is that the light reflection layer has a laminated structure of silver or a silver alloy located adjacent to the resin material layer and aluminum or an aluminum alloy located on the side away from the resin material layer.

[0042] That is, in order to give the light reflection layer the aforementioned reflectivity characteristics, a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated may be used. In this case as well, the reflective material on the radiation surface side needs to be silver or a silver alloy. In this case, the thickness of silver needs to be 10 nm or more, and the thickness of aluminum needs to be 30 nm or more.

[0043] And since aluminum or an aluminum alloy is less expensive than silver or a silver alloy, it is possible to reduce the cost of the light reflection layer while having appropriate reflectivity characteristics. That is, while thinning the expensive silver or silver alloy to reduce the cost of the light reflection layer, by forming the light reflection layer into a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy, it is possible to reduce the cost of the light reflection layer while having appropriate reflectivity characteristics.

[0044] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, it is possible to reduce the cost of the light reflection layer while having appropriate reflectivity characteristics.

[0045] A further characteristic configuration of the radiative cooling device of the present invention is that the resin material forming the resin material layer is a vinyl chloride-based resin mixed with a plasticizer, and the plasticizer consists of one or more compounds selected from the group consisting of phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters.

[0046] That is, vinyl chloride resins can obtain sufficient thermal radiation in the atmospheric window region. That is, the thermal radiation characteristics of vinyl chloride resins are equivalent to those of fluororesins and silicone rubbers that can obtain large thermal radiation in the atmospheric window region, and they are much cheaper than these resins. Therefore, they are effective for constructing a radiative cooling device that can lower the temperature below the ambient temperature under direct sunlight at low cost. When forming a resin material layer with a vinyl chloride resin, as described above, it is preferable that the thickness is 100 μm or less and 10 μm or more.

[0047] In addition, since the thin-film vinyl chloride resin becomes soft by adding a plasticizer, it can avoid being damaged by changing its shape flexibly according to other objects even when it comes into contact with other objects, and thus can be maintained in a beautiful state for a long time. Incidentally, since the thin-film fluororesin is hard, it cannot change its shape flexibly due to contact with other objects and is easily damaged, making it difficult to maintain a beautiful state.

[0048] Moreover, by adding a plasticizer to the vinyl chloride resin, even if it is damaged, it can be deformed by heating to 80 °C or higher to smooth the surface scratches, that is, the scratches can be self-healed. Fluororesins and silicone rubbers do not have this property. Due to this property of the soft vinyl chloride resin, a beautiful state can be maintained for a long time. This leads to the maintenance of radiative cooling performance over a long period.

[0049] Furthermore, since the plasticizer mixed into the vinyl chloride resin is composed of one or more compounds selected from the group consisting of phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters, the plasticizer is less likely to absorb ultraviolet rays (ultraviolet light with a wavelength of 295 nm to 400 nm) contained in sunlight. Therefore, the weather resistance of the vinyl chloride resin mixed with the plasticizer can be improved. That is, when the plasticizer mixed in the vinyl chloride resin absorbs ultraviolet rays, as a result, the hydrolysis of the plasticizer proceeds, and the vinyl chloride resin generates dehydrochloric acid or the like and becomes colored (brown). Moreover, there is a risk of a decrease in mechanical strength. However, since the plasticizer is difficult to absorb the ultraviolet rays contained in sunlight, the weather resistance of the vinyl chloride resin mixed with the plasticizer can be improved.

[0050] Incidentally, it is also preferable to mix a plasticizer in the resin layer on the film material side formed on the back surface portion of the film material. In this case, in the resin layer on the film material side, the absorption of ultraviolet rays by the plasticizer mixed in the resin layer on the film material side can be suppressed by mixing an ultraviolet absorber or coloring it in a color that easily absorbs ultraviolet rays. Therefore, as the plasticizer to be mixed in the resin layer on the film material side, in addition to phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters, trimellitic acid ester (TOTM) and epoxidized fatty acid ester (epoxidized soybean oil) can be used as plasticizers.

[0051] In short, according to the further characteristic configuration of the radiative cooling type film material of the present invention, it is possible to provide a radiative cooling type device that can achieve sufficient flexibility while reducing costs and can improve weather resistance.

[0052] A further characteristic configuration of the radiative cooling type device of the present invention is that the plasticizer is mixed in a range of 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin.

[0053] That is, since the plasticizer mixed in the vinyl chloride resin is mixed in a range of 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin, the vinyl chloride resin can be provided with appropriate flexibility.

[0054] A further characteristic configuration of the radiative cooling type device of the present invention is that the phosphoric acid ester of the plasticizer is a triester phosphate or an aromatic phosphoric acid ester.

[0055] That is, by using a triester phosphate or an aromatic phosphate ester as the phosphate ester plasticizer, it is possible to appropriately make it difficult for the plasticizer to absorb ultraviolet rays contained in sunlight.

[0056] A further characteristic configuration of the radiative cooling device of the present invention is configured in a form provided with a protective layer between the infrared radiation layer and the light reflection layer. The protective layer is a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate resin having a thickness of 17 μm or more and 40 μm or less.

[0057] That is, sunlight incident from the radiation surface of the resin material layer as the infrared radiation layer is reflected by the light reflection layer on the side opposite to the side where the radiation surface of the resin material layer is present after passing through the resin material layer and the protective layer, and escapes from the radiation surface to the outside of the system.

[0058] In addition, since the protective layer is formed in a form having a thickness of 300 nm or more and 40 μm or less with a polyolefin resin, or in a form having a thickness of 17 μm or more and 40 μm or less with an ethylene terephthalate resin, even in a daytime solar radiation environment, discoloration of the silver or silver alloy of the light reflection layer can be suppressed. Therefore, while appropriately reflecting sunlight with the light reflection layer, the cooling function can be accurately exhibited even in a daytime solar radiation environment.

[0059] That is, when the protective layer does not exist, radicals generated in the resin material layer reach the silver or silver alloy forming the light reflection layer, or moisture passing through the resin material layer reaches the silver or silver alloy forming the light reflection layer, whereby the silver or silver alloy of the light reflection layer may discolor in a short period of time and the light reflection function may not be appropriately exhibited. However, the presence of the protective layer can suppress discoloration of the silver or silver alloy of the light reflection layer in a short period of time.

[0060] An explanation will be added regarding suppressing discoloration of the silver or silver alloy of the light reflection layer by the protective layer. When the protective layer is formed of a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, since the polyolefin resin is a synthetic resin with an ultraviolet light absorption rate of 10% or less in the entire ultraviolet wavelength range from 0.295 μm to 0.4 μm, the protective layer is less likely to deteriorate due to ultraviolet absorption.

[0061] And since the thickness of the polyolefin resin forming the protective layer is 300 nm or more, it can effectively block the radicals generated in the resin material layer from reaching the silver or silver alloy forming the light reflection layer, and also block the moisture permeating through the resin material layer from reaching the silver or silver alloy forming the light reflection layer. Thus, it can suppress the discoloration of the silver or silver alloy forming the light reflection layer.

[0062] That is, the protective layer formed of the polyolefin resin will deteriorate while forming radicals on the surface side away from the reflection layer due to ultraviolet absorption. However, since the thickness is 300 nm or more, the formed radicals will not reach the light reflection layer. Moreover, even if it deteriorates while forming radicals, the progress of deterioration is slow due to the low ultraviolet absorption, so the above-mentioned blocking function can be exerted over a long period.

[0063] When the protective layer is formed of ethylene terephthalate resin with a thickness of 17 μm or more and 40 μm or less, although the ethylene terephthalate resin has a higher ultraviolet light absorption rate than the polyolefin resin in the ultraviolet wavelength range from 0.295 μm to 0.4 μm, since the thickness is 17 μm or more, it can effectively block the radicals generated in the resin material layer from reaching the silver or silver alloy forming the light reflection layer, and also block the moisture permeating through the resin material layer from reaching the silver or silver alloy forming the light reflection layer. Thus, it can suppress the discoloration of the silver or silver alloy forming the protective layer over a long period.

[0064] That is, the protective layer formed of polyethylene terephthalate resin deteriorates while forming radicals on the surface side away from the reflective layer by absorbing ultraviolet rays. However, since the thickness is 17 μm or more, the formed radicals do not reach the reflective layer. Further, even if it deteriorates while forming radicals, since the thickness is 17 μm or more, the above-described blocking function will be exhibited over a long period of time.

[0065] In addition, when forming the protective layer with a polyolefin resin and a polyethylene terephthalate resin, the reason for determining the upper limit of the thickness is to avoid as much as possible the heat insulation property in which the protective layer does not contribute to radiative cooling. That is, since the protective layer exhibits a heat insulation property that does not contribute to radiative cooling as the thickness increases, in order to avoid as much as possible the heat insulation property that does not contribute to radiative cooling while exhibiting the function of protecting the reflective layer, the upper limit of the thickness is determined.

[0066] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, it is possible to provide a radiative cooling device that can cool the inside of the film material well while suppressing discoloration of silver or a silver alloy of the light reflective layer in a short period of time.

[0067] A further characteristic configuration of the radiative cooling device of the present invention lies in that an adhesive layer connecting the resin material layer and the protective layer is provided between the resin material layer and the protective layer.

[0068] That is, when the adhesive layer connecting the resin material layer and the protective layer is provided between the infrared radiation layer and the protective layer, for example, the light reflective layer and the protective layer are formed in a laminated state, and the resin material layer and the protective layer separately manufactured are joined with an adhesive layer, so that the resin material layer, the protective layer, and the light reflective layer can be favorably formed in a laminated state. That is, a radiative cooling layer can be favorably produced.

[0069] In addition, when the adhesive layer is located between the resin material layer and the protective layer, radicals are generated from the adhesive layer. However, the protective layer can suppress the radicals generated in the adhesive layer from reaching the light reflective layer.

[0070] In short, according to the characteristic configuration of the radiative cooling device of the present invention, a radiative cooling layer can be well formed.

[0071] A further characteristic configuration of the radiative cooling device of the present invention lies in that the adhesive or pressure-sensitive adhesive used for the sizing layer is any one of urethane-based, acrylic-based, and ethylene vinyl acetate-based adhesives.

[0072] That is, the adhesive or pressure-sensitive adhesive used for the sizing layer is any one of urethane-based, acrylic-based, and ethylene vinyl acetate-based adhesives, and such an adhesive or pressure-sensitive adhesive can provide high transparency to sunlight. That is, even with a sizing layer, the radiative cooling effect can be appropriately exerted.

[0073] A further characteristic configuration of the radiative cooling device of the present invention lies in that an inorganic material filler is mixed into the resin material layer.

[0074] That is, since an inorganic material filler is mixed into the resin material layer, due to the light scattering effect of the inorganic material filler, the color of the radiative cooling device when viewed from the side where the radiation surface exists becomes white, and the aesthetic appearance can be improved.

[0075] That is, when no inorganic material filler is mixed into the resin material layer, the silver of the light reflection layer can be seen by looking through the transparent resin material layer, but due to the light scattering effect of the inorganic material filler, the color of the radiative cooling device when viewed from the side where the radiation surface exists becomes white, and the aesthetic appearance can be improved.

[0076] In short, according to the further characteristic configuration of the radiative cooling device of the present invention, the color of the radiative cooling device when viewed from the side where the radiation surface exists can be made white.

[0077] A further characteristic configuration of the radiative cooling device of the present invention lies in that an inorganic material filler is mixed into the sizing layer.

[0078] That is, since the filler of the inorganic material is mixed into the adhesive layer that connects the resin material layer and the protective layer, the adhesive layer is protected by the resin material layer, so that moisture contained in rain or air is suppressed from penetrating into the adhesive layer. As a result, the filler of the inorganic material mixed into the adhesive layer is suppressed from being affected by the moisture contained in rain or air, avoiding early deterioration of the radiative cooling layer and improving the durability of the radiative cooling layer.

[0079] Also, even when a filler of an inorganic material is mixed into the adhesive layer that connects the resin material layer and the protective layer, when the radiative cooling layer is viewed from the side where the radiation surface exists, the filler of the inorganic material mixed into the adhesive layer can be seen through the transparent resin material layer. Therefore, due to the light scattering effect of the filler of the inorganic material, the color of the radiative cooling device when viewed from the side where the radiation surface exists becomes white, and the aesthetic appearance can be improved.

[0080] In short, according to a further characteristic configuration of the radiative cooling device of the present invention, the durability can be improved while making the color of the radiative cooling device white when viewed from the side where the radiation surface exists.

[0081] A further characteristic configuration of the radiative cooling device of the present invention is that the weight ratio of the filler to the adhesive layer is 0.1 to 40 wt%.

[0082] That is, since the weight ratio of the filler to the adhesive layer is 0.1 to 40 wt%, it is possible to appropriately make the color of the radiative cooling device white when viewed from the side where the radiation surface exists.

[0083] A further characteristic configuration of the radiative cooling device of the present invention is that the filler includes any one selected from the group consisting of silicon dioxide, titanium oxide, aluminum oxide, magnesium oxide, and calcium carbonate.

[0084] That is, since the filler contains any one selected from the group consisting of silicon dioxide, titanium oxide, aluminum oxide, magnesium oxide, and calcium carbonate, it is possible to appropriately make the color of the radiative cooling device white when viewed from the side where the radiative surface exists.

[0085] A further characteristic configuration of the radiative cooling device of the present invention is that the filler contains titanium oxide.

[0086] That is, by using titanium oxide having no photocatalytic activity, it is possible to appropriately suppress the filler mixed in the adhesive layer from deteriorating the resin material layer adjacent to the adhesive layer.

[0087] A further characteristic configuration of the radiative cooling device of the present invention is that at least one of an alumina coat, a silica coat, and a zirconia coat is provided on the titanium oxide.

[0088] That is, since at least one of an alumina coat, a silica coat, and a zirconia coat is provided on the titanium oxide, the filler can be appropriately made to have no photocatalytic activity, so that it is possible to more appropriately suppress the deterioration of the resin material layer adjacent to the adhesive layer.

[0089] A further characteristic configuration of the radiative cooling device of the present invention is that the radiative surface is formed in a concavo-convex shape.

[0090] That is, by forming the radiative surface in a concavo-convex shape, the surface area of the radiative surface can be increased. As a result, for example, when outside air flows, the outside air is ventilated with respect to the radiative surface, so that the cooling function can be improved.

[0091] In short, according to the further characteristic configuration of the radiative cooling device of the present invention, the cooling function can be improved.

Brief Description of the Drawings

[0092]

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Embodiments for Carrying Out the Invention

[0093] Hereinafter, embodiments of the present invention will be described with reference to the drawings. 〔Basic Configuration of Radiation Cooling Type Device〕 As shown in FIG. 1, in a radiation cooling type device W, a film-shaped radiation cooling layer CP is attached to the outer surface of a film material E (an example of a base material), and the film material E is cooled by the radiation cooling action of the radiation cooling layer CP. In FIG. 1, the radiation cooling layer CP is connected to the outer surface of the film material E by an adhesive or adhesive connection layer S.

[0094] FIG. 1 illustrates a case where a tent-type warehouse 1 is formed by the radiation cooling type device W. That is, the upper surface portion and the surrounding side surface portions of the tent-type warehouse 1 are formed of a canvas configured by joining a plurality of radiation cooling type devices W. The configuration of joining a plurality of radiation cooling type devices W will be described later.

[0095] The radiation cooling layer CP includes, in a laminated state, an infrared radiation layer A that radiates infrared light IR from a radiation surface H, a light reflection layer B that is positioned on the side opposite to the side where the radiation surface H exists in the infrared radiation layer A, and a protective layer D between the infrared radiation layer A and the light reflection layer B, and is formed in a film shape. That is, the radiation cooling layer CP is configured as a radiation cooling film. Note that a coat layer BC mainly composed of silica is provided on the side where the radiation surface H exists in the infrared radiation layer A of the radiation cooling film.

[0096] The light reflection layer B reflects light L such as sunlight that has passed through the infrared radiation layer A and the protective layer D, and its reflection characteristics are such that the reflectance at a wavelength of 400 nm to 500 nm is 90% or more, and the reflectance at a wavelength longer than 500 nm is 96% or more. The sunlight spectrum exists from a wavelength of 300 nm to 4000 nm, and the intensity increases as the wavelength increases from 400 nm, and particularly the intensity is large from a wavelength of 500 nm to a wavelength of 1800 nm.

[0097] Note that in this embodiment, the light L includes ultraviolet light (ultraviolet rays), visible light, and infrared light. When these are described in terms of the wavelength of light as an electromagnetic wave, it includes electromagnetic waves with a wavelength of 10 nm to 20000 nm (0.01 μm to 20 μm electromagnetic waves). Incidentally, in this document, it is assumed that the wavelength range of ultraviolet light (ultraviolet rays) is between 295 nm and 400 nm.

[0098] Since the light reflection layer B exhibits a reflection characteristic of 90% or more from a wavelength of 400 nm to 500 nm and a reflectance of 96% or more for wavelengths longer than 500 nm, the solar energy absorbed by the radiation cooling layer CP (radiation cooling film) by the light reflection layer B can be suppressed to 5% or less, that is, the solar energy absorbed at noon in summer can be made about 50 W.

[0099] The light reflection layer B is made of silver or a silver alloy, or is configured as a laminated structure of silver or a silver alloy adjacent to the protective layer D and aluminum or an aluminum alloy located on the side away from the protective layer D, and has flexibility, the details of which will be described later.

[0100] The infrared radiation layer A is configured as a resin material layer J made of vinyl chloride resin or vinylidene chloride resin adjusted to a thickness that emits thermal radiation energy greater than the absorbed solar energy in the wavelength band from 8 μm to 14 μm, and its details will be described later.

[0101] Therefore, the radiative cooling layer CP is configured to reflect a part of the light L incident on the radiative cooling layer CP at the radiation surface H of the infrared radiation layer A, and reflect the light (such as sunlight) that has passed through the resin material layer J and the protective layer D among the light L incident on the radiative cooling layer CP at the light reflection layer B, and escape it to the outside from the radiation surface H.

[0102] And the heat input to the radiative cooling layer CP from the film material E located on the side opposite to the side where the resin material layer J exists in the light reflection layer B (for example, heat input due to heat conduction from the film material E) is converted into infrared light IR by the resin material layer J and radiated, thereby cooling the film material E.

[0103] That is, the radiative cooling layer CP is configured to reflect the light L irradiated to the radiative cooling layer CP, and also radiate the heat transfer to the radiative cooling layer CP (for example, heat transfer from the atmosphere or heat transfer from the film material E) to the outside as infrared light IR. In addition, since the resin material layer J, the protective layer D, and the light reflection layer B have flexibility, the radiative cooling layer CP (radiative cooling film) is configured to have flexibility.

[0104] On the back surface of the film material E away from the radiative cooling layer CP, a film material side resin layer Ej formed of vinyl chloride resin or vinylidene chloride resin is provided. That is, the film material E is formed in a form in which a film material main body Eh and a film material side resin layer Ej are laminated. As the film material body Eh, there are those formed as woven fabrics of natural fibers such as cotton and hemp, those formed as woven fabrics of inorganic fibers, synthetic fibers, and special fibers, and those formed as non-woven fabrics such as spunbond, spunlace, and needle punch. Incidentally, the thickness of the film material body Eh is, for example, about 0.1 mm to 5 mm. Incidentally, as the inorganic fibers, there are metal fibers and glass fibers. As the synthetic fibers, there are polyamide-based, polyester-based, polyacrylonitrile-based, polyvinyl alcohol-based, polypropylene-based, and polyethylene-based fibers. As the special fibers, there are aramid fibers, carbon fibers, and biodegradable fibers.

[0105] 〔Overview of the resin material layer〕 The resin material forming the resin material layer J has a light absorption rate and an emissivity (light emission rate) that change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer J so that it does not absorb sunlight as much as possible and emits a large amount of thermal radiation in the so-called atmospheric window wavelength band (the band from wavelength 8 μm to wavelength 14 μm).

[0106] Specifically, from the viewpoint of the light absorption rate of sunlight, the thickness of the resin material layer J is such that the wavelength average of the light absorption rate from wavelength 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from wavelength 0.5 μm to wavelength 0.8 μm is 4% or less, the wavelength average of the light absorption rate from wavelength 0.8 μm to wavelength 1.5 μm is within 1%, the wavelength average of the light absorption rate from wavelength 1.5 μm to 2.5 μm is 40% or less, and the wavelength average of the light absorption rate from wavelength 2.5 μm to 4 μm is 100% or less. In the case of such an absorption rate distribution, the light absorption rate of sunlight is 10% or less, and in terms of energy, it is 100 W or less.

[0107] As described later, the light absorption rate of the resin material increases as the film thickness of the resin material increases. When the resin material is made into a thick film, the emissivity of the atmospheric window becomes almost 1, and at that time, the thermal radiation emitted into space is 125 W / m 2 to 160 W / m 2 and becomes. The sunlight absorption in the protective layer D and the light reflection layer B is 50 W / m 2The following is the case. The sum of the solar light absorption in the resin material layer J, the protective layer D, and the light reflection layer B is 150 W / m 2 or less, and cooling progresses if the atmospheric conditions are good. As the resin material for forming the resin material layer J, it is preferable to use a material with a low light absorption rate near the peak value of the solar light spectrum as described above.

[0108] Also, from the viewpoint of infrared radiation (thermal radiation), the thickness of the resin material layer J needs to be adjusted to a thickness in a state where the wavelength average of the emissivity from 8 μm to 14 μm is 40% or more. To release the thermal energy of sunlight of about 50 W / m 2 absorbed by the protective layer D and the light reflection layer B from the resin material layer J into space through the thermal radiation of the resin material layer J, it is necessary for the resin material layer J to emit more thermal radiation. For example, when the outside air temperature is 30 °C, the maximum of the thermal radiation of the atmospheric window from 8 μm to 14 μm is 200 W / m 2 (calculated with an emissivity of 1). This value is obtained on a clear day in an environment with thin and dry air such as in the mountains. In lowlands, etc., since the thickness of the atmosphere is thicker than in the mountains, the wavelength band of the atmospheric window becomes narrower and the transmittance decreases. Incidentally, this is called "the atmospheric window becomes narrower".

[0109] Also, the environment where the radiative cooling layer CP (radiative cooling film) is actually used may be humid, and in that case too, the atmospheric window becomes narrower. The thermal radiation generated in the atmospheric window region when used in lowlands is estimated to be 160 W / m 2 at 30 °C in good conditions (calculated with an emissivity of 1). Also, as is often the case in Japan, when there is haze in the sky or when smog exists, the atmospheric window becomes even narrower, and the radiation into space is about 125 W / m 2 . In view of such circumstances, the wavelength average of the emissivity from 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the atmospheric window band is 50 W / m 2 ) or it cannot be used in lowlands in the mid-latitude zone.

[0110] Therefore, when the thickness of the resin material layer J is adjusted so as to fall within the range of the optical regulation in view of the above matters, the heat dissipation in the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and it becomes possible to perform radiative cooling outdoors even in a solar radiation environment. In the present embodiment, the thickness of the vinyl chloride resin or vinylidene chloride resin forming the resin material layer J is 100 μm or less and 10 μm or more.

[0111] 〔Details of resin material〕 According to Kirchhoff's law, the emissivity (ε) and the light absorption rate (A) are equal. The light absorption rate can be obtained from the absorption coefficient (α) by the relational expression A = 1 - exp(-αt) (hereinafter referred to as the light absorption rate relational expression). Here, t is the film thickness. That is, when the film thickness of the resin material layer J is adjusted, large thermal radiation can be obtained in the wavelength band with a large absorption coefficient. When performing radiative cooling outdoors, it is preferable to use a material having a large absorption coefficient in the wavelength band of the atmospheric window, that is, from wavelength 8 μm to 14 μm. Further, in order to suppress the absorption of sunlight, it is preferable to use a material having no absorption coefficient or a small absorption coefficient in the range of wavelength 0.3 μm to 4 μm, particularly 0.4 μm to 2.5 μm. As can be seen from the relational expression between the absorption coefficient and the absorption rate, the light absorption rate (emissivity) changes depending on the film thickness of the resin material.

[0112] In order to lower the temperature from the surrounding atmosphere by radiative cooling in a solar radiation environment, if a material having a large absorption coefficient in the wavelength band of the atmospheric window and almost no absorption coefficient in the wavelength band of sunlight is selected, sunlight is hardly absorbed by adjusting the film thickness, but a large amount of thermal radiation in the atmospheric window is emitted. That is, it is possible to create a state where the output by radiative cooling is larger than the input of sunlight.

[0113] The sunlight spectrum only has wavelengths longer than 0.295 μm. The definition of ultraviolet rays is the range on the shorter wavelength side than wavelength 0.4 μm, the definition of visible light is the range from wavelength 0.4 μm to 0.8 μm, the definition of near-infrared rays is the range from wavelength 0.8 μm to 3 μm, the definition of mid-infrared rays is the range from 3 μm to 8 μm, and the definition of far-infrared rays is the range of wavelengths longer than 8 μm.

[0114] Regarding the carbon-chlorine bond (C-Cl), the bond energy between the carbon of the alkene and chlorine is 3.28 eV, and its wavelength is 0.378 μm. Therefore, it absorbs a lot of ultraviolet light in sunlight but has almost no absorption in the visible region. The absorption rate spectrum of a 100-μm-thick vinyl chloride resin from ultraviolet to visible light is shown in Fig. 2, and the light absorption increases on the shorter wavelength side than 0.38 μm. The absorption rate spectrum of a 100-μm-thick vinylidene chloride resin from ultraviolet to visible light is shown in Fig. 2, and a slight increase in the absorption rate spectrum is observed on the shorter wavelength side than 0.4 μm.

[0115] Incidentally, Fig. 2 also shows the absorption rate spectrum of a 40-μm-thick ethylene terephthalate resin from ultraviolet to visible light and the absorption rate spectrum of an ethylene resin from ultraviolet to visible light.

[0116] Fig. 3 shows the emissivity of vinyl chloride resin (PVC) with a carbon-chlorine bond in the atmospheric window. Fig. 4 also shows the emissivity of vinylidene chloride resin (PVDC) with a carbon-chlorine bond in the atmospheric window. Regarding the carbon-chlorine bond, the absorption coefficient due to C-Cl stretching vibration appears in a wide band with a half-value width of 1 μm or more centered at a wavelength of 12 μm. Also, in the case of vinyl chloride resin, due to the electron-withdrawing effect of chlorine, the absorption coefficient derived from the angular vibration of C-H of the alkene contained in the main chain appears at around a wavelength of 10 μm. 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% from a wavelength of 8 μm to 14 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.

[0117] As shown in Fig. 3, in the case of vinyl chloride resin, even if the thickness is more than 100 μm, there is almost no increase in the thermal radiation in the atmospheric window region. That is, in the case of vinyl chloride resin, the thermal radiation in the atmospheric window occurs in the portion within about 100 μm from the surface, and the radiation from deeper parts does not come out. As shown in FIG. 4, it can be seen that the vinylidene chloride resin is the same as the vinyl chloride resin.

[0118] As described above, the thermal radiation in the atmospheric window region generated from the surface of the resin material occurs in the portion where the depth from the surface is generally within 100 μm. As the thickness of the resin increases beyond this, the cold heat radiatively cooled by the radiative cooling layer CP is insulated by the resin material that does not contribute to the thermal radiation. Consider creating a resin material layer J that ideally does not absorb any sunlight on top of the light reflection layer B. In this case, sunlight is absorbed only by the light reflection layer B of the radiative cooling layer CP. The thermal conductivity of the resin material is generally about 0.2 W / m / K. When calculated considering this thermal conductivity, if the thickness of the resin material layer J exceeds 20 mm, the temperature of the cooling surface (the surface on the side opposite to the side where the resin material layer J exists in the light reflection layer B) will increase.

[0119] Even if there were an ideal resin material that does not absorb any sunlight, since the thermal conductivity of the resin material is generally about 0.2 W / m / K, when the thickness exceeds 20 mm, the light reflection layer B will be heated by receiving solar radiation, and the film material E installed on the light reflection layer side will be heated. That is, the thickness of the resin material of the radiative cooling layer CP needs to be 20 mm or less.

[0120] 〔Regarding the thickness of the resin material layer〕 From a practical perspective of the radiative cooling layer CP, it is better for the thickness of the resin material layer J to be thinner. The thermal conductivity of the resin material is generally lower than that of metals, glass, etc. To effectively cool the film material E, the film thickness of the resin material layer J should be the minimum required. The thermal radiation in the atmospheric window increases as the film thickness of the resin material layer J increases, and the thermal radiation energy in the atmospheric window saturates when it exceeds a certain film thickness.

[0121] The saturated film thickness depends on the resin material. In the case of resins containing carbon-chlorine bonds, even when the thickness is 100 μm, it is saturated, and sufficient thermal radiation can be obtained in the atmospheric window region even at a thickness of 50 μm. The thinner the resin material, the higher the heat transfer coefficient and the more effectively the temperature of the film material E can be lowered. Therefore, in the case of resins containing carbon-chlorine bonds, when the thickness is less than 50 μm, the heat insulation property becomes small and the film material E can be effectively cooled. In the case of carbon-chlorine bonds, if the thickness is 100 μm or less, the film material E can be effectively cooled.

[0122] The utility of making it thinner is not only to reduce the heat insulation property and make it easier to transfer cold heat. It is the suppression of near-infrared light absorption derived from CH, CH2, and CH3 in the near-infrared region exhibited by resins containing carbon-chlorine bonds. When it is made thinner, the sunlight absorption by these can be reduced, so the cooling capacity of the radiative cooling layer CP will increase. From the above viewpoints, in the case of vinyl chloride resin and vinylidene chloride resin, which are resins containing carbon-chlorine bonds, when the thickness is 50 μm or less, the radiative cooling effect can be more effectively exhibited under sunlight.

[0123] 〔Details of the light reflection layer〕 In order to give the light reflection layer B the above-described reflectance characteristics, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy. As shown in FIG. 5, if the light reflection layer B is configured based on silver, the reflectance required for the light reflection layer B can be obtained.

[0124] When reflecting sunlight with only silver or a silver alloy in a state having the above-described reflectance characteristics, a thickness of 50 nm or more is required. However, in order to give the light reflection layer B flexibility, it is necessary to make the thickness 100 μm or less. If it is thicker than this, it becomes difficult to bend. Incidentally, as the "silver alloy", an alloy in which any one of copper, palladium, gold, zinc, tin, magnesium, nickel, and titanium is added to silver, for example, in an amount of about 0.4% to 4.5% by mass can be used. As a specific example, "APC-TR (manufactured by Furuya Metal)" which is a silver alloy created by adding copper and palladium to silver can be used.

[0125] In order to give the light reflection layer B the above-described reflectance characteristics, a structure in which silver or a silver alloy located adjacent to the protective layer D and aluminum or an aluminum alloy located on the side away from the protective layer D are laminated may be used. Still, also in this case, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy. When composed of two layers of silver (silver alloy) and aluminum (aluminum alloy), the thickness of silver needs to be 10 nm or more, and the thickness of aluminum needs to be 30 nm or more. However, in order to make the light reflection layer B flexible, it is necessary to make the total of the thickness of silver and the thickness of aluminum 100 μm or less. If it is thicker than this, it becomes difficult to bend.

[0126] Incidentally, as the "aluminum alloy", an alloy in which copper, manganese, silicon, magnesium, zinc, carbon steel for mechanical structures, yttrium, lanthanum, gadolinium, and terbium are added to aluminum can be used.

[0127] Silver and silver alloys are vulnerable to rain and humidity and need to be protected from them, and it is also necessary to suppress their discoloration. For this purpose, as shown in FIGS. 6 to 9, a protective layer D for protecting silver is required in a form adjacent to silver or a silver alloy. Details of the protective layer D will be described later.

[0128] 〔Details of the coat layer〕 The coat layer BC is a layer mainly composed of particulate silica and is provided on the side where the radiation surface exists in the resin material layer J as the infrared radiation layer A. The layer thickness of the coat layer BC is preferably 30 nm or more and less than 500 nm, and more preferably 200 nm or more and less than 400 nm. In the present specification, "silicon dioxide" or "silica" does not only refer to SiO2, but also includes those with oxygen deficiency from silicon dioxide such as SiO, SiO 2-x (0 < x ≤ 1), etc. It may also contain groups other than Si-O-Si resulting from the synthesis of a part of silica, such as alkoxy groups and hydroxyl groups. Furthermore, those in which organic acids, amines, etc. are chemically bonded or hydrogen-bonded to the terminal hydroxyl groups are also included.

[0129] The coating material for forming the coating layer BC is obtained by dispersing granular silica in ethanol (an example of an alcohol solvent), mixing, and drying. That is, the film-forming method of the coating layer BC is to uniformly apply a mixture obtained by dispersing granular silica in ethanol (an example of an alcohol solvent) and mixing it onto the radiation surface H of the resin material layer J by a method such as gravure coating, and then dry ethanol as a solvent by heat or light to form a film.

[0130] Furthermore, for the coating material forming the coating layer BC, when the mass remaining after heating the coating material with the mass before heating and drying at 200 °C for a predetermined determination heating time is defined as the first remaining mass X, and the mass remaining after heating the coating material with the mass before heating and drying at 700 °C for the determination heating time is defined as the second remaining mass Y, the value of (first remaining mass X - second remaining mass Y) / first remaining mass X satisfies the condition of being 0.05 or more and less than 0.45.

[0131] This condition is a method for quantitatively indicating the surface-modified organic structure of silica. The coating layer BC satisfying this condition exhibits, in particular, the effect of suppressing the decrease in reflectance over time due to the improvement of antifouling property, the effect of suppressing the decrease in reflectance over time due to yellowing of the radiation layer by ultraviolet rays, the effect of suppressing the decrease in the infrared radiation performance from the radiation surface, and the effect of having sufficient abrasion resistance. The above condition quantitatively indicates the surface-modified organic structure of silica.

[0132] 〔Test showing the effect of the coating layer〕 In order to confirm the effect of the coating layer BC, the following four tests were conducted. The sample properties of the examples and Comparative Examples 1 to 4 are as shown in [Table 1] below.

[0133] [Regarding the First Test] The first test is a test related to the function of suppressing the decrease in reflectance over time due to the improvement of antifouling properties. Samples of the radiative cooling films according to the examples and comparative examples were exposed to the outdoor environment for 2,400 hours in a posture where their radiative surfaces faced south and were inclined at 35° with respect to the ground. Then, the color difference ΔE between the state after exposure and the state before exposure to the outdoor environment was determined, and it was judged whether or not the color difference was less than 2.0. Note that the color difference ΔE shall mean the "CIEDE2000 color difference" based on JIS Z8781. Incidentally, if the color difference ΔE is less than 2.0, it means that the dirt on the surface of the coating layer BC causes a sufficiently small decrease in reflectance.

[0134] [Regarding the Second Test] The second test is a test related to the function of suppressing the decrease in reflectance over time due to the yellowing of the radiation layer caused by ultraviolet rays. Samples of the radiative cooling films according to the examples and comparative examples were exposed to ultraviolet rays with a wavelength of 550 nm and an intensity of 180 W / m 2 in an environment with a black panel temperature (BPT) of 63°C using a xenon weather resistance tester (Suga Tester SX-75) for 3,000 hours. Then, the degree of change in the reflectance of sunlight (reflectance after ultraviolet ray exposure / reflectance before ultraviolet ray exposure) before and after the second test was determined, and it was judged whether or not the degree of change exceeded 0.97.

[0135] [Regarding the Third Test] The third test is a test related to the function of suppressing the decrease in the infrared radiation performance from the radiative surface after manufacturing samples of the radiative cooling films according to the examples and comparative examples and sufficiently drying the coating agent. For samples of the radiative cooling films according to the examples and comparative examples, the average emissivity of infrared rays from wavelength 8 μm to 13 μm was measured using a spectrometer, and it was judged whether or not the average emissivity exceeded 0.95.

[0136] Regarding the Fourth Test The Fourth Test is a Taber test for evaluating abrasion resistance as defined in JIS K7204. Samples of the radiation cooling films according to the examples and comparative examples were tested under the conditions of rotating the 1000 - rotation abrasion wheel at a load of 2.5 N and a rotational speed of 60 rpm for 1000 rotations for abrasion.

[0137] The test results of the First Test to the Fourth Test are shown in the following [Table 1].

[0138] [Table 1]

[0139] In the above First Test to Fourth Test, in the examples, it was confirmed that while the color difference ΔE and the change degree of the reflectance of ultraviolet rays (550 nm) could be suppressed to less than a certain level over the set test period, while exhibiting a certain level of abrasion resistance, the average emissivity could be maintained at a value equal to or higher than the desired value.

[0140] (Specific Configuration of the Radiation Cooling Device) Since the resin materials forming the resin material layer J and the protective layer D of the radiation cooling layer CP are flexible, if the light - reflecting layer B is made into a thin film, the light - reflecting layer B can also be made flexible. As a result, the radiation cooling layer CP can be made into a film with flexibility (radiation cooling film).

[0141] And as shown in FIGS. 6 - 9, by attaching the radiation cooling layer CP (radiation cooling film) to the outer surface of the film material E with the connection layer S of an adhesive or a pressure - sensitive adhesive, the film material E can be cooled. Examples of the adhesive or pressure - sensitive adhesive used for the connection layer S include urethane - based adhesives (pressure - sensitive adhesives), acrylic - based adhesives (pressure - sensitive adhesives), EVA (ethylene vinyl acetate) - based adhesives (pressure - sensitive adhesives), etc.

[0142] In FIGS. 6 to 9, as the film material E, an example is given of a film material E in which a film material main body Eh is immersed in a resin solution of vinyl chloride resin or vinylidene chloride resin so that the film material main body Eh is impregnated with vinyl chloride resin or vinylidene chloride resin. Therefore, in addition to including a film material side resin layer Ej formed of vinyl chloride resin or vinylidene chloride resin on the back surface portion away from the radiative cooling layer CP, the film material E is configured in a form including a surface side resin layer Ek formed of vinyl chloride resin or vinylidene chloride resin on the surface portion approaching the radiative cooling layer CP. That is, the film material E is formed in a form in which the surface side resin layer Ek, the film material main body Eh, and the film material side resin layer Ej are laminated.

[0143] Incidentally, as the film material E in FIGS. 6 to 9, it goes without saying that the surface side resin layer Ek may be omitted and the film material E may be formed in a form in which the film material main body Eh and the film material side resin layer Ej are laminated as shown in FIG. 1. To form the film material E in a form in which the film material main body Eh and the film material side resin layer Ej are laminated, production procedures such as applying vinyl chloride resin or vinylidene chloride resin to the film material main body Eh to form the film material side resin layer Ej, or attaching a separately produced film of vinyl chloride resin or vinylidene chloride resin to the film material main body Eh to form the film material side resin layer Ej can be used.

[0144] Various forms are conceivable for producing the radiative cooling layer CP in a film form. For example, it is conceivable to produce it by applying a protective layer D and a resin material layer J to a light reflection layer B produced in a film form. Alternatively, it is conceivable to produce it by attaching a protective layer D and a resin material layer J to a light reflection layer B produced in a film form. Or, it is conceivable to produce a protective layer D by applying or attaching it onto a resin material layer J produced in a film form, and then producing a light reflection layer B on the protective layer D by vapor deposition, sputtering, ion plating, silver mirror reaction, or the like.

[0145] Specifically, when the light reflection layer B is formed as a single layer of silver or a silver alloy, or when it is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy), the radiation cooling layer CP (radiation cooling film) in Fig. 6 has a protective layer D formed on the upper side of the light reflection layer B, a resin material layer J formed on the upper part of the protective layer D, and a lower protective layer Ds is also formed on the lower side of the light reflection layer B. Incidentally, the lower protective layer Ds is formed of, for example, an acrylic resin.

[0146] As a method for manufacturing the radiation cooling layer CP (radiation cooling film) in Fig. 6, a method can be adopted in which the protective layer D, the light reflection layer B, and the lower protective layer Ds are sequentially coated on the film-shaped resin material layer J and integrally formed.

[0147] The radiation cooling layer CP (radiation cooling film) in Fig. 8 is composed of an aluminum layer B1 formed of an aluminum foil that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy. A protective layer D is formed on the upper side of the light reflection layer B, and a resin material layer J is formed on the upper part of the protective layer D.

[0148] As a method for manufacturing the radiation cooling layer CP (radiation cooling film) in Fig. 8, a method can be adopted in which the silver layer B2, the protective layer D, and the resin material layer J are sequentially coated on the aluminum layer B1 composed of an aluminum foil and integrally formed. In addition, as another manufacturing method, a method can be adopted in which the resin material layer J is formed in a film shape, the protective layer D and the silver layer B2 are sequentially coated on the film-shaped resin material layer J, and the aluminum layer B1 is attached to the silver layer B2.

[0149] When the light reflection layer B is formed as a single layer of silver or a silver alloy, or when it is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy), the radiation cooling layer CP (radiation cooling film) in Fig. 8 has a protective layer D formed on the upper side of the light reflection layer B, a resin material layer J formed on the upper part of the protective layer D, and a film layer F such as PET is formed on the lower side of the light reflection layer B.

[0150] As a method for creating the radiative cooling layer CP (radiative cooling film) of FIG. 8, on a film layer F (corresponding to a base material) formed in a film shape with PET (ethylene terephthalate resin) or the like, a light reflection layer B and a protective layer D are sequentially coated and integrally formed, and a film-shaped resin material layer J separately formed is adhered to the protective layer D with an adhesive layer N. A method can be adopted. Examples of the adhesive (adhesive agent) used in the adhesive layer N include urethane-based adhesives (adhesive agents), acrylic-based adhesives (adhesive agents), EVA (ethylene vinyl acetate)-based adhesives (adhesive agents), etc., and those having high transparency to sunlight are desirable.

[0151] The radiative cooling layer CP (radiative cooling film) of FIG. 9 is composed of an aluminum layer B1 that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy (substitute silver). The aluminum layer B1 is formed on top of a film layer F (corresponding to a base material) formed in a film shape with PET (ethylene terephthalate resin) or the like, a protective layer D is formed above the silver layer B2, and a resin material layer J is formed above the protective layer D.

[0152] As a method for creating the radiative cooling layer CP (radiative cooling film) of FIG. 9, an aluminum layer B1 is coated on the film layer F, and the film layer F and the aluminum layer B1 are integrally formed. Separately, a protective layer D and a silver layer B2 are coated on a film-shaped resin material layer J, and the resin material layer J, the protective layer D, and the silver layer B2 are integrally formed, and a method of adhering the aluminum layer B1 and the silver layer B2 with an adhesive layer N can be adopted. Examples of the adhesive (adhesive agent) used in the adhesive layer N include urethane-based adhesives (adhesive agents), acrylic-based adhesives (adhesive agents), EVA (ethylene vinyl acetate)-based adhesives (adhesive agents), etc., and those having high transparency to sunlight are desirable.

[0153] 〔Details of the protective layer〕 The protective layer D is a polyolefin-based resin with a thickness of 300 nm or more and 40 μm or less, or polyethylene terephthalate with a thickness of 17 μm or more and 40 μm or less. Examples of polyolefin resins include polyethylene and polypropylene.

[0154] As described above, Fig. 2 shows the ultraviolet absorption rate of polyethylene. Also, Fig. 10 shows the light transmittance of polyethylene, which is suitable as the synthetic resin for forming the protective layer D.

[0155] Since the radiative cooling layer CP (radiative cooling film) exhibits a radiative cooling effect not only at night but also in a solar radiation environment, in order to maintain the state in which the light reflection layer B exhibits its light reflection function, it is necessary to protect the light reflection layer B with the protective layer D so that the silver of the light reflection layer B does not discolor in a solar radiation environment.

[0156] When the protective layer D is formed of a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, the polyolefin resin is a synthetic resin with an ultraviolet light absorption rate of 10% or less in the entire ultraviolet wavelength range from 0.295 μm to 0.4 μm. Therefore, the protective layer D is less likely to deteriorate due to ultraviolet absorption.

[0157] And since the thickness of the polyolefin resin forming the protective layer D is 300 nm or more, it can effectively block the radicals generated in the resin material layer J from reaching the silver or silver alloy forming the light reflection layer, and also block the moisture passing through the resin material layer J from reaching the silver or silver alloy forming the light reflection layer B. Thus, it can suppress the discoloration of the silver or silver alloy forming the light reflection layer B.

[0158] Incidentally, the protective layer D formed of a polyolefin resin deteriorates while forming radicals on the surface side away from the light reflection layer B due to ultraviolet absorption. However, since the thickness is 300 nm or more, the formed radicals do not reach the light reflection layer B. Also, even though it deteriorates while forming radicals, the progress of deterioration is slow due to the low ultraviolet absorption, so the above-mentioned blocking function can be exerted over a long period.

[0159] When the protective layer D is formed of polyethylene terephthalate resin in a form with a thickness of 17 μm or more and 40 μm or less, the polyethylene terephthalate resin is a resin material with a higher ultraviolet light absorption rate in the ultraviolet wavelength range of 0.295 μm to 0.4 μm than the polyolefin-based resin. However, since the thickness is 17 μm or more, radicals generated in the resin material layer J are blocked from reaching the silver or silver alloy forming the light reflection layer B, and moisture permeating through the resin material layer J is blocked from reaching the silver or silver alloy forming the light reflection layer. Thus, the blocking function can be well exerted over a long period, and discoloration of the silver or silver alloy forming the light reflection layer B can be suppressed.

[0160] That is, the protective layer D formed of polyethylene terephthalate resin deteriorates while forming radicals on the surface side away from the light reflection layer B due to ultraviolet absorption. However, since the thickness is 17 μm or more, the formed radicals do not reach the light reflection layer B. Also, even when deteriorating while forming radicals, since the thickness is 17 μm or more, the above-described blocking function can be exerted over a long period.

[0161] To add an explanation, the deterioration of polyethylene terephthalate resin (PET) is caused by the cleavage of the ester bond between ethylene glycol and terephthalic acid by ultraviolet rays, forming radicals. This deterioration progresses in order from the surface of the surface of the polyethylene terephthalate resin (PET) irradiated with ultraviolet rays.

[0162] For example, when ultraviolet rays of a certain intensity in Osaka irradiate the polyethylene terephthalate resin (PET), about 9 nm of the ester bond of the polyethylene terephthalate resin (PET) cleaves in order from the irradiated surface per day. Since the polyethylene terephthalate resin (PET) is sufficiently polymerized, the polyethylene terephthalate resin (PET) on the cleaved surface does not attack the silver (silver alloy) of the light reflection layer B. However, when the cleavage end of the polyethylene terephthalate resin (PET) reaches the silver (silver alloy) of the light reflection layer B, the silver (silver alloy) discolors.

[0163] Therefore, in order to make the protective layer D durable for more than one year outdoors, multiplying 9 nm / day by 365 days results in a required thickness of approximately 3 μm. In order to make the ethylene terephthalate resin (PET) of the protective layer D durable for more than three years, a thickness of 10 μm or more is required. In order to make it durable for more than five years, a thickness of 17 μm or more is required.

[0164] In addition, when forming the protective layer D with a polyolefin resin and an ethylene terephthalate resin, the reason for determining the upper limit of its thickness is to avoid the heat insulation property that the protective layer D does not contribute to radiative cooling. That is, the thicker the protective layer D, the more heat insulation property it has that does not contribute to radiative cooling. Therefore, in order to avoid having a heat insulation property that does not contribute to radiative cooling while exerting the function of protecting the light reflection layer B, the upper limit of the thickness is determined.

[0165] That is, when the protective layer D becomes thicker, there is no demerit in preventing the coloring of silver (silver alloy) in the light reflection layer B, but problems occur in radiative cooling. That is, increasing the thickness increases the heat insulation property of the radiative cooling material. For example, as shown in Fig. 14, a resin whose main component is polyethylene, which is excellent as a synthetic resin for forming the protective layer D, has a low emissivity in the atmospheric window, so even if it is formed thickly, it does not contribute to radiative cooling. On the contrary, increasing the thickness increases the heat insulation property of the radiative cooling material. Next, as the thickness increases, the absorption in the near-infrared region due to the vibration of the main chain increases, and the effect of increasing the solar light absorption increases. Due to these factors, a thick protective layer D is disadvantageous for radiative cooling. From this perspective, the thickness of the protective layer D formed of a polyolefin resin is preferably 5 μm or less, and more preferably 1 μm.

[0166] Incidentally, as shown in FIG. 8, when the paste layer N is located between the resin material layer J and the protective layer D, radicals will also be generated from the paste layer N. However, if the thickness of the polyolefin resin forming the protective layer D is 300 nm or more and the thickness of the ethylene terephthalate resin forming the protective layer D is 17 μm or more, the radicals generated in the paste layer N can be suppressed from reaching the light reflection layer B over a long period of time.

[0167] 〔Consideration of the protective layer〕 In order to examine the difference in the way silver is colored by the protective layer D, a sample was prepared in which the protective layer D without the resin material layer J as the infrared radiation layer A as shown in FIG. 11 was exposed, and the coloring of silver after being irradiated with simulated sunlight was examined. That is, as the protective layer D, two types, a general acrylic resin that absorbs ultraviolet rays (for example, a methyl methacrylate resin mixed with a benzotriazole-based ultraviolet absorber) and polyethylene, were applied with a bar coater onto a film layer F (corresponding to the substrate) provided with silver as the light reflection layer B to form a sample, and the function as the protective layer D was examined. The thickness of the applied protective layer D was 10 μm and 1 μm, respectively. Incidentally, the film layer F (corresponding to the substrate) is formed in a film shape from PET (ethylene terephthalate resin) or the like.

[0168] As shown in FIG. 13, when the protective layer D is an acrylic resin that absorbs ultraviolet rays well, the protective layer D is decomposed by ultraviolet rays to form radicals, and immediately the silver turns yellow and no longer functions as the radiation cooling layer CP (absorbs sunlight and the temperature rises when exposed to solar radiation like a general material). Incidentally, the line at 600 h in the figure is the reflectance spectrum after performing a xenon weather test (ultraviolet light energy is 60 W / m 2 ) for 600 h (hours) under the conditions of JIS standard 5600-7-7. Also, the line at 0 h is the reflectance spectrum before performing the xenon weather test.

[0169] As shown in Fig. 12, when the protective layer D is made of polyethylene with a low ultraviolet light absorption rate, it can be seen that there is no decrease in reflectance from the near-infrared region to the visible region. That is, a resin (polyolefin resin) whose main component is polyethylene hardly absorbs the ultraviolet rays in sunlight reaching the ground, so it is difficult to form radicals even when sunlight hits, and even when sunlight hits, silver coloring as the light reflection layer B does not occur. Incidentally, the line of 600h in the figure is the reflectance spectrum after performing a xenon weather test (ultraviolet light energy is 60W / m 2 ) for 600h (hours) under the conditions of JIS standard 5600-7-7. Also, the line of 0h is the reflectance spectrum before performing the xenon weather test.

[0170] The reason why the reflectance spectrum in this wavelength band fluctuates is the Fabry-Perot resonance of the polyethylene layer. It can be seen that this is due to the change in the thickness of the polyethylene layer caused by heat in the xenon weather test, etc., and this resonance position changes slightly between the 0h line and the 600h line, but a large decrease in reflectance in the ultraviolet-visible region due to silver yellowing is not observed.

[0171] Incidentally, the fluororesin system can also be applied as a material for forming the protective layer D from the viewpoint of ultraviolet absorption, but when actually formed as the protective layer D, it colors and deteriorates during the formation stage, so it cannot be used as a material for forming the protective layer D. Also, silicone can also be applied as a material for forming the protective layer D from the viewpoint of ultraviolet absorption, but its adhesion to silver (silver alloy) is extremely poor, so it cannot be used as a material for forming the protective layer D.

[0172] 〔Regarding the mixing of plasticizers〕 When the resin material layer J is formed of a vinyl chloride resin, it is preferable to mix a plasticizer into the vinyl chloride resin to improve flexibility. The plasticizer to be mixed into the vinyl chloride resin is any one of phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters. And the plasticizer is mixed in a range of 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin. From the viewpoint of processing, it is desirable that the parts by weight of the plasticizer be 100 parts by weight or less.

[0173] The aliphatic dibasic acid ester of the plasticizer may be composed of adipic acid esters, adipic acid ester copolymers, azelaic acid esters, azelaic acid ester copolymers, sebacic acid esters, sebacic acid ester copolymers, succinic acid esters, succinic acid ester copolymers alone or in combination of a plurality thereof.

[0174] The aliphatic dibasic acid ester of the plasticizer is preferably one in which an aliphatic dibasic acid and two molecules of a saturated aliphatic alcohol are ester-bonded. The phthalic acid ester of the plasticizer is preferably one in which phthalic acid and two molecules of a saturated aliphatic alcohol are ester-bonded. The phosphoric acid ester of the plasticizer is preferably a triester of phosphoric acid or an aromatic phosphoric acid ester.

[0175] <Details of phthalic acid esters> The phthalic acid esters are listed as follows. Dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DPP), di-2-ethylhexyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), ditridecyl phthalate (DTDP), bis(2-ethylhexyl) terephthalate (DOTP), bis(2-ethylhexyl) isophthalate (DOIP), etc.

[0176] <Details of aliphatic dibasic acid esters> The aliphatic dibasic acid esters are listed as follows. Dibutyl adipate (DBA), diisobutyl adipate (DIBA), di-2-ethylhexyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate (DIDA), bis-2-ethylhexyl azelate (DOZ), dibutyl sebacate (DBS), di-2-ethylhexyl sebacate (DOS), diisononyl sebacate (DINS), diethyl succinate (DESU), etc. Also, an aliphatic polyester having a molecular weight of 400 to 4000 synthesized by copolymerization (polyesterification) of a dibasic acid such as adipic acid and a diol (a bifunctional alcohol or a glycol).

[0177] <Triester phosphate> When listing triester phosphates, it is as follows. Trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), tris(2-ethylhexyl) phosphate (TOP).

[0178] <Aromatic phosphate ester> When listing aromatic phosphate esters, it is as follows. Triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), cresyl diphenyl phosphate (CDP), 2-ethylhexyl diphenyl phosphate.

[0179] <Regarding the evaluation of appropriate plasticizers> Plasticizers for vinyl chloride resins include phthalic acid esters, aliphatic dibasic acid esters, triester phosphates, aromatic phosphate esters, trimellitic acid esters, and epoxidized fatty acid esters. The following compounds were selected from these plasticizers, and 43 parts by weight of various plasticizers were mixed with 100 parts by weight of vinyl chloride and evaluated by a xenon weather test. In addition, a triazine-based ultraviolet absorber and a hindered amine-based light stabilizer were kneaded into 100 parts by weight of vinyl chloride resin at 0.5 parts by weight each.

[0180] As representatives of phthalic acid esters, di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). As representatives of aliphatic dibasic acid esters, di-2-ethylhexyl adipate (DOA), butanediol adipate copolymer (average molecular weight of about 1000), and diisononyl adipate (DINA). As a representative of triester phosphates, tributyl phosphate (TBP). As a representative of aromatic phosphate esters, tricresyl phosphate (TCP). As a representative of trimellitic acid esters, tri-2-ethylhexyl trimellitate (TOTM). As a representative of epoxidized fatty acid esters, epoxidized soybean oil.

[0181] The durability test was carried out by performing a xenon weather test for 1920 hours (equivalent to 4 years of actual exposure). Note that 487 hours is equivalent to 1 year in terms of ultraviolet conversion. The conditions of the xenon weather test are as follows. Ultraviolet intensity 180W / m 2 (wavelength 295 - 400nm). 〈No watering condition〉BPT 89°C, humidity 50%, 1 hour 42 minutes. 〈With watering condition〉Tank temperature 38°C, humidity 90%, 18 minutes.

[0182] The test results for 1920 hours are shown in Figure 15. Incidentally, in this embodiment, experiments are carried out with vinyl chloride resin, but the same applies to vinylidene chloride resin. As a result of the above experiments, it became clear that when trimellitic acid ester (TOTM) and epoxidized fatty acid ester (epoxidized soybean oil) are used as plasticizers, the durability is significantly reduced. Note that the epoxidized fatty acid turned brown at 1120 hours and the test could not be continued, so it is not shown in the figure.

[0183] On the other hand, it was found that when phthalate esters, aliphatic dibasic acid esters, triester phosphates, or aromatic phosphate esters are used, they can last for about four years. That is, when phthalate esters, aliphatic dibasic acid esters, triester phosphates, or aromatic phosphate esters are used as plasticizers incorporated into vinyl chloride resins, even after about four years, the reflectance of the radiative cooling layer CP does not decrease. However, when trimellitic acid esters or epoxidized fatty acid esters are used as plasticizers incorporated into vinyl chloride resins, it was found that the reflectance of the radiative cooling layer CP significantly decreases before about four years have passed.

[0184] From the above test results, it can be seen that as plasticizers for vinyl chloride resins, phthalates, aliphatic dibasic acid esters, triester phosphates, and aromatic phosphate esters have excellent durability, while trimellitic acid esters and epoxidized fatty acid esters have no durability. Incidentally, the reason for this will be considered and systematized as described later.

[0185] 〔Regarding Other Additives〕 The vinyl chloride resin forming the resin material layer J may contain a flame retardant, a stabilizer, a stabilization aid, a filler, an antioxidant, an ultraviolet absorber, or a light stabilizer.

[0186] 〔Another Configuration of the Radiative Cooling Layer〕 As shown in FIG. 16, the radiative cooling layer CP may be configured to include an anchor layer G on top of the film layer F (corresponding to the base material), and on top of the anchor layer G, a light reflection layer B, a protective layer D, and an infrared radiation layer A. Incidentally, the film layer F (corresponding to the base material) is formed in a film shape, for example, from PET (ethylene terephthalate resin) or the like.

[0187] The anchor layer is introduced to enhance the adhesion between the film layer F and the light reflection layer B. That is, if silver (Ag) is directly deposited on the film layer F, there is a risk of easy peeling. The anchor layer G is preferably composed mainly of acrylic, polyolefin, or urethane, and mixed with a compound having an isocyanate group or a melamine resin. It is a coating for a part that is not directly exposed to sunlight, and there is no problem even if it is a material that absorbs ultraviolet rays. In addition, there are methods other than introducing the anchor layer G to enhance the adhesion between the film layer F and the light reflection layer B. For example, irradiating the film-forming surface of the film layer F with plasma to roughen the surface can improve the adhesion.

[0188] 〔Consideration of the connection layer〕 When the radiation cooling layer CP is attached to the outer surface of the film material E, it is advisable to make the thickness of the connection layer S 5 μm or more and 100 μm or less. That is, the outer surface (surface) of the film material E is often not a mirror surface. The outer surface (material surface) of the film material E, which is different from a mirror surface, often has innumerable scratches and irregularities on the order of several micrometers. When the micrometer-level irregularities existing on the outer surface (material surface) of the film material E are transferred to the light reflection layer B (silver layer) of the radiation cooling layer CP, the reflectivity will decrease. Therefore, it is necessary to introduce a structure that prevents the irregularities existing on the outer surface (material surface) from being reflected in the radiation cooling layer CP. For this purpose, the radiation cooling layer CP may be joined to the outer surface of the film material E with a connection layer S having a thickness of about 5 μm to 100 μm.

[0189] If there is a connection layer S of 5 μm or more composed of an adhesive or a sticky agent, the connection layer S absorbs the irregularities on the outer surface of the film material E, and the light reflection layer B (silver layer) of the radiation cooling layer CP becomes flat. When the light reflection layer B (silver layer) becomes flat, it is possible to prevent a decrease in the solar light reflectivity (in other words, an increase in the solar light absorption rate). However, as the thickness of the connection layer S increases, the heat insulation property improves. If the heat insulation property improves, the cold heat of the radiation cooling layer CP is insulated, which is not good. From this perspective, an unnecessarily thick connection layer S is unnecessary, and a thickness of 100 μm is sufficient.

[0190] [Connection of the radiation cooling device] To produce the canvas forming the upper surface portion and the surrounding side surface portions of the tent-shaped warehouse 1, a plurality of radiation cooling devices W will be joined together. On the surface side of the radiation cooling device W, there is a resin material layer J (infrared radiation layer A) made of vinyl chloride resin or vinylidene chloride resin, and on the back side of the radiation cooling device W, there is a resin layer Ej on the film material side made of vinyl chloride resin or vinylidene chloride resin. Therefore, as shown in Fig. 17, a plurality of radiation cooling devices W will be joined by heat welding.

[0191] That is, when forming the canvas constituting a tent or the like, for example, a plurality of radiation cooling devices W are joined in a form where the edges of the radiation cooling devices W formed as rectangular films are joined together. Since the joining can be performed by heat fusion welding, the productivity when forming the canvas can be improved. Incidentally, as the heat fusion welding, high-frequency welding, hot air welding, hot pressing welding, etc. can be applied.

[0192] [Another exemplary illustration of the radiation cooling device] The canvas formed by joining a plurality of radiation cooling devices W can be used for various purposes. That is, as shown in Fig. 18, the awning 2 in the truck with an awning can be constituted by the canvas joined with a plurality of radiation cooling devices W, or as shown in Fig. 19, the cargo bed sheet 3 covering the cargo bed of the truck can be constituted by the canvas joined with a plurality of radiation cooling devices W.

[0193] When the awning 2 or the cargo bed sheet 3 in the truck is constituted by the canvas joined with a plurality of radiation cooling devices W, as shown in Fig. 20, it is preferable to form the radiation surface H of the radiation cooling layer CP in a concavo-convex shape. Incidentally, even when the radiation surface H is formed in a concavo-convex shape in this way, it is preferable to provide a coat layer BC on the surface of the radiation surface H. That is, for example, it may be formed in a state where there are convex portions U on the radiation surface H. Specific examples of the concavo-convex shape include a line-and-space structure in which rectangular parallelepiped convex portions U are arranged (see Fig. 22), a structure in which conical column convex portions U are arranged vertically and horizontally (see Fig. 23), and although not shown in the figure, a structure in which triangular prism or pyramid-shaped convex portions U are arranged in a line-and-space manner, a structure in which rectangular parallelepiped-shaped convex portions U are arranged vertically and horizontally, a structure in which convex portions U are formed randomly, etc. Various configurations can be adopted. Incidentally, the height difference when forming the radiation surface H in a concavo-convex shape is about 100 μm.

[0194] The advantages of forming the radiation surface H in a concavo-convex shape will be described by taking a truck equipped with a canopy 2 as an example. As shown in Fig. 21, since the truck moves, the lower surface of the truck is always in contact with heated asphalt during the day. Due to the inflow of heat from the heated asphalt or the like, even if the film material E of the canopy 2 is covered with the radiation cooling layer CP, there is a risk that the internal temperature of the container 8 will rise above the environmental temperature (outside air temperature). In the case of a moving body, it is subjected to strong winds during movement. This wind is at a lower temperature than the temperature inside the container heated by asphalt or the like, and it is desirable to introduce a design that takes into account heat exchange (convection) due to the wind during driving.

[0195] Summarize the discussions so far. The heat input into the canopy 2 is as follows. The first point is heat input by sunlight. The second point is heat radiation from the heated asphalt (since it moves, the container is always directly above the hot asphalt). Due to the influence of these two points, there is a risk that the inside (internal space) of the canopy 2 will become hotter than the environmental temperature (outside air temperature).

[0196] When the awning 2 is configured by the radiative cooling device W, since the radiative cooling layer CP attempts to discharge the heat of the container 8, the temperature inside the awning 2 relatively decreases compared to the case where other materials such as solar radiation reflecting paint are applied. However, because the heat inflow from the asphalt in the second aspect is large, even though it is equipped with the radiative cooling layer CP, it is likely to have a temperature rise during the day compared to the environmental temperature (outside air temperature). When the internal temperature of the awning 2 is higher than the environmental temperature (outside air temperature), the external air acts as a heat source, and it is desirable to increase the heat exchange with the external air. In particular, since the moving body receives strong wind during movement, a structure that facilitates heat exchange when receiving wind is introduced into the radiative cooling layer CP. That is, to increase the heat exchange with the wind, it is good to increase the surface roughness and the surface area.

[0197] From such a perspective, as shown in FIG. 20, it is preferable to form the infrared radiation layer A of the radiative cooling layer CP in a concavo-convex shape by embossing or the like to increase the surface area. That is, this structure has a heat source other than sunlight and heated air, and it is preferable to introduce it when the temperature of the film material E on which the radiative cooling layer CP is mounted rises higher than the environmental temperature (outside air temperature) and the environmental temperature (outside air temperature) acts as a cold heat source.

[0198] Forming the radiation surface H in a concavo-convex shape also has advantages in terms of appearance. When the radiation surface H (upper surface) of the radiative cooling layer CP is formed in a concavo-convex shape rather than being a mirror surface, sunlight is scattered, so the glare of the radiative cooling layer CP is reduced. Since the radiative cooling layer CP being less glare improves visibility, the safety during running is enhanced. In addition, even if a function of "scattering" is imparted to the radiation surface H, the light absorption in the silver (silver alloy) of the light reflection layer B does not increase, so radiative cooling can be performed well.

[0199] 〔Another configuration of the radiative cooling layer〕 As shown in FIGS. 24 and 25, an inorganic material filler Q may be mixed into the resin material layer J constituting the infrared radiation layer A to provide a light-scattering configuration. In addition, even when the inorganic material filler Q is mixed into the resin material layer J constituting the infrared radiation layer A in this way, it is preferable to provide a coating layer BC on the surface of the radiation surface of the resin material layer J. Also, as shown in FIGS. 26 and 27, when the adhesive layer N connecting the resin material layer J and the protective layer D is provided between the resin material layer J and the protective layer D, an inorganic material filler Q may be mixed into the adhesive layer N to provide a light-scattering configuration. Also in this case, a coating layer BC can be provided on the surface of the radiation surface of the resin material layer J. As the adhesive or pressure-sensitive adhesive used for the adhesive layer, urethane-based, acrylic-based, ethylene vinyl acetate-based, etc. can be preferably used. That is, the adhesive (pressure-sensitive adhesive) used in the adhesive layer N includes, for example, urethane-based adhesives (pressure-sensitive adhesives), acrylic-based adhesives (pressure-sensitive adhesives), EVA (ethylene vinyl acetate)-based adhesives (pressure-sensitive adhesives), etc., and those having high transparency to sunlight are applicable. Incidentally, the thickness of the adhesive layer N is, for example, about 10 μm.

[0200] Incidentally, the radiative cooling device W shown in FIGS. 24 to 27 has the same configuration as the radiative cooling device W shown in FIG. 8, but when the inorganic material filler Q is mixed into the resin material layer J, the radiative cooling device W having the configuration shown in FIGS. 6, 7, and 9 can be applied.

[0201] When the inorganic material filler Q is mixed into the resin material layer J, when the radiative cooling layer CP is viewed from the side where the radiation surface H exists, the inorganic material filler Q mixed into the transparent resin material layer J can be seen. Therefore, due to the light-scattering action of the inorganic material filler Q, the color of the radiative cooling device W when viewed from the side where the radiation surface H exists becomes white, and the aesthetic appearance can be improved.

[0202] Further, since the filler F of the inorganic material is mixed into the adhesive layer N that connects the resin material layer J and the protective layer D, when the radiation cooling layer CP is viewed from the side where the radiation surface H exists, the filler F of the inorganic material mixed into the adhesive layer N can be seen through the transparent resin material layer J. Therefore, due to the light scattering effect of the filler F of the inorganic material, the color of the radiation cooling device W when viewed from the side where the radiation surface H exists becomes white, and the aesthetic appearance can be improved. Incidentally, the filler F may be mixed into both the resin material layer J and the adhesive layer N.

[0203] As the inorganic material for forming the filler V, silicon dioxide (SiO2), titanium oxide (TiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), calcium carbonate (CaCO3), etc. can be preferably used. In particular, titanium oxide (TiO2) of about 200 nm without photocatalytic activity can be preferably used. Further, at least one of an alumina coat, a silica coat, and a zirconia coat may be provided on the titanium oxide (TiO2). By doing so, the filler can be appropriately made to have no photocatalytic activity, so that it is easy to suppress the deterioration of the resin material layer J.

[0204] Incidentally, when the filler V is mixed into the resin material layer J, both the front and back surfaces of the resin material layer J become uneven. When the back surface of the resin material layer J becomes uneven, it is desirable that the adhesive layer N is positioned between the resin material layer J and the protective layer D. That is, even if the back surface of the resin material layer J is uneven, since the adhesive layer N (bonding layer) is positioned between the resin material layer J and the protective layer D, the resin material layer J and the protective layer D can be appropriately bonded. Incidentally, when the back surface of the resin material layer J becomes uneven, for example, the resin material layer J and the protective layer D may be directly bonded by plasma bonding. Incidentally, plasma bonding is a form in which radicals are formed by the radiation of plasma on the bonding surface of the resin material layer J and the bonding surface of the protective layer D, and the bonding is performed by the radicals.

[0205] [Regarding the incorporation of fillers into the protective layer] Incidentally, when filler V is incorporated into the protective layer D, the back surface in contact with the light reflection layer B of the protective layer D becomes uneven, which causes the surface of the light reflection layer B to be deformed unevenly. Therefore, it is necessary to avoid incorporating filler V into the protective layer D. That is, if the surface of the light reflection layer B is deformed unevenly, light reflection cannot be properly performed, and as a result, radiant cooling cannot be properly performed.

[0206] The experimental results regarding this point will be described based on FIG. 28. "Directly forming an Ag layer on the light diffusion layer" in FIG. 28 means forming the light reflection layer B by depositing silver (Ag) by vapor deposition or the like on the surface of the infrared radiation layer A (resin material layer J) with embossed unevenness on the side of the Ag layer which is the light reflection layer B or by incorporating filler V. Also, "light diffusion layer on mirror-finish Ag" means that the upper surface of the Ag layer which is the light reflection layer B is formed in a mirror-finish state, and the upper part of the Ag layer, the protective layer D, and the infrared radiation layer A (resin material layer J) with embossed unevenness or incorporating filler V are laminated.

[0207] As shown in FIG. 28, in the case of "directly forming an Ag layer on the light diffusion layer", the surface of the light reflection layer B becomes uneven, so the light reflectance greatly decreases. However, in the case of "light diffusion layer on mirror-finish Ag", the surface of the light reflection layer B is maintained in a mirror-finish state, and an appropriate light reflectance can be obtained.

[0208] [Another configuration of the infrared radiation layer] As shown in FIG. 29, the front and back surfaces of the resin material layer J constituting the infrared radiation layer A may be formed unevenly to provide a light scattering configuration. With this configuration, when looking at the radiation surface H, the glare of the radiation surface H can be suppressed.

[0209] That is, the resin material layer J of the radiative cooling layer CP shown in FIGS. 6 to 9 has a flat structure on both the front and back surfaces and does not contain the filler Q. However, in such a configuration, since the radiation surface H becomes mirror-like, when looking at the radiation surface H, it will feel shiny. However, if a light scattering configuration is provided, this shininess can be suppressed.

[0210] To make the front and back surfaces of the resin material layer J uneven, it can be done by performing embossing or processing that damages the surface. Even if the back surface of the resin material layer J is uneven, if the adhesive layer N is positioned between the resin material layer J and the protective layer D, the resin material layer J and the protective layer D can be properly joined.

[0211] 〔Alternative Embodiment〕 The following lists alternative embodiments. (1) In the above embodiment, the case of providing the protective layer D was exemplified. However, it may also be implemented in a form where the protective layer D is omitted.

[0212] (2) In the above embodiment, the case where the canvas formed by joining a plurality of radiative cooling devices W is applied to the tent-type warehouse 1, the truck hood 2, and the cargo bed sheet 3 was exemplified. However, in addition, the canvas formed by joining a plurality of radiative cooling devices W can be applied to form various types of tents such as camping tents and sunshade tarps.

[0213] (3) In the above embodiment, the resin layer E on the film material side does not necessarily have to be provided. That is, the film material E as the base material may be composed only of the film material main body Eh.

[0214] Note that the configurations disclosed in the above embodiments (including alternative embodiments, the same applies hereinafter) can be applied in combination with the configurations disclosed in other embodiments as long as there is no contradiction. Also, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to this, and can be appropriately modified within the scope that does not deviate from the object of the present invention.

Industrial Applicability

[0215] The radiation cooling film material of the present invention can be effectively used as a radiation cooling film material that prevents the reflectance from decreasing over time for a relatively long period, maintains the wear resistance of the surface (radiation surface), and does not reduce the radiation performance.

Explanation of Reference Signs

[0216] A Infrared radiation layer B Light reflection layer BC Coating layer D Protective layer E Film material Eh Film material body H Radiation surface J Resin material layer Q Filler

Claims

1. A radiation cooling layer is attached to the outer surface of a base material, the radiation cooling layer is configured in a form including an infrared radiation layer that radiates infrared light from a radiation surface, and a light reflection layer positioned on the side opposite to the side where the radiation surface exists in the infrared radiation layer, the infrared radiation layer is a resin material layer made of vinyl chloride resin or vinylidene chloride resin adjusted to a thickness that emits thermal radiation energy greater than the absorbed solar energy in a band from wavelength 8 μm to wavelength 14 μm, the light reflection layer includes silver or a silver alloy, a coating layer mainly composed of granular silica is provided on the side where the radiation surface exists in the infrared radiation layer, the layer thickness of the coating layer is 30 nm or more and less than 500 nm, the coating material for forming the coating layer, when the mass remaining when the coating material with the pre-heating drying mass (mass before heating and drying) is heated at 200 °C for a predetermined determination heating time is defined as the first remaining mass, and the mass remaining when the coating material with the pre-heating drying mass is heated at 700 °C for the determination heating time is defined as the second remaining mass, a radiation cooling device that satisfies the condition that the value of (first remaining mass - second remaining mass) / first remaining mass is 0.05 or more and less than 0.

45.

2. The radiation cooling device according to claim 1, wherein the radiation cooling layer is attached to the outer surface of the film material by an adhesive or an adhesive connection layer.

3. The film thickness of the resin material layer, the wavelength average of the light absorption rate from wavelength 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from wavelength 0.5 μm to wavelength 0.8 μm is 4% or less, the wavelength average of the light absorption rate from wavelength 0.8 μm to wavelength 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less, and has light absorption characteristics, and The radiation cooling device according to claim 1 or 2, which is adjusted to a thickness having thermal radiation characteristics in which the wavelength average of the emissivity from 8 μm to 14 μm is 40% or more.

4. The radiation cooling device according to claim 1 or 2, wherein the light reflection layer has a reflectivity of 90% or more from wavelength 0.4 μm to 0.5 μm and a reflectivity of 96% or more for wavelengths longer than 0.5 μm.

5. The radiation cooling device according to claim 1 or 2, wherein the light reflection layer is composed of silver or a silver alloy and has a thickness of 50 nm or more.

6. The radiation cooling device according to claim 1 or 2, wherein the light reflection layer has a laminated structure of silver or a silver alloy located adjacent to the resin material layer and aluminum or an aluminum alloy located on the side away from the resin material layer.

7. The resin material forming the resin material layer is a vinyl chloride resin or a vinylidene chloride resin mixed with a plasticizer, The radiation cooling device according to claim 1 or 2, wherein the plasticizer is composed of one or more compounds selected from the group consisting of phthalic acid esters, aliphatic dibasic acid esters, and phosphoric acid esters.

8. The radiation cooling device according to claim 7, wherein the plasticizer is mixed in a range of 1 part by weight or more and 200 parts by weight or less with respect to 100 parts by weight of the vinyl chloride-based resin.

9. The radiation cooling device according to claim 7, wherein the phosphoric acid ester of the plasticizer is a triester of phosphoric acid or an aromatic phosphoric acid ester.

10. It is configured in a form provided with a protective layer between the resin material layer and the light reflection layer, The radiation cooling device according to claim 1 or 2, wherein the protective layer is a polyolefin-based resin having a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate resin having a thickness of 17 μm or more and 40 μm or less.

11. The radiation cooling device according to claim 10, wherein an adhesive layer connecting the resin material layer and the protective layer is provided between the resin material layer and the protective layer.

12. The radiation cooling device according to claim 11, wherein the adhesive or pressure-sensitive adhesive used for the adhesive layer is any one of urethane-based, acrylic-based, and ethylene vinyl acetate-based.

13. The radiation cooling device according to claim 1 or 2, wherein an inorganic material filler is mixed in the resin material layer.

14. The radiation cooling device according to claim 11, wherein an inorganic material filler is mixed in the adhesive layer.

15. The radiation cooling device according to claim 14, wherein the weight ratio of the filler to the adhesive layer is 0.1 to 40 wt%.

16. The radiation cooling device according to claim 13, wherein the filler contains any one selected from the group consisting of silicon dioxide, titanium oxide, aluminum oxide, magnesium oxide, and calcium carbonate.

17. The radiation cooling device according to claim 13, wherein the filler contains titanium oxide.

18. The radiative cooling device according to claim 17, wherein at least one of an alumina coat, a silica coat, and a zirconia coat is provided on the titanium oxide.

19. The radiative cooling device according to claim 1 or 2, wherein the radiation surface is formed in a concavo-convex shape.

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