Radiative cooling film, how to use it, and how to make it

Abstract

To provide a radiation cooling film that has an increased shape followability to an attachment target.SOLUTION: A filter body F includes: an infrared radiation layer A for radiating infrared light IR from a radiation surface H; a light reflection layer B made of silver or silver alloy located in an opposite side to a side of the infrared radiation layer A where the radiation surface H is present; an adjacent side protection layer Du located in a side of the light reflection layer B which is adjacent to the infrared radiation layer A; and a separation side protection layer Ds located in a side of the light reflection layer B which is away from the infrared radiation layer A. The infrared radiation layer A is a resin material layer J adjusted to have a thickness which allows the resin material layer to emit a larger thermal radiation energy than an absorbed solar light energy in a band with wavelengths of 8 μm to 14 μm. The resin material forming the separation side protection layer Ds and the separation side protection layer Ds is one of urethane resin, acrylic urethane resin, and polyolefin resin.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention is configured in a film body including an infrared emitting layer that emits infrared light from a radiation surface, a light reflecting layer made of silver or a silver alloy and located on the infrared emitting layer on the side opposite to the side on which the radiation surface is present, an adjacent-side protective layer located on the side of the light reflecting layer that is adjacent to the infrared emitting layer, and a remote-side protective layer located on the side of the light reflecting layer that is remote from the infrared emitting layer, The present invention relates to a radiative cooling film in which the infrared radiation layer is a resin material layer whose thickness is adjusted to emit thermal radiation energy in the wavelength band of 8 μm to 14 μm that is greater than the absorbed solar light energy. [Background technology]

[0002] Radiative cooling is a phenomenon in which a substance's temperature drops when it radiates infrared or other electromagnetic waves into its surroundings. This phenomenon can be used to create, for example, a radiative cooling film that cools an object without consuming any energy, such as electricity.

[0003] In the radiative cooling film, the infrared emitting layer emits thermal radiation energy in the wavelength band of 8 μm to 14 μm, which is greater than the absorbed solar energy. Therefore, the light reflective layer sufficiently reflects sunlight, allowing the cooling target to be cooled even in a daytime solar radiation environment.

[0004] In other words, the light reflecting layer reflects the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer and radiates it from the radiation surface, preventing the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer from being projected onto the object to be cooled and heating the object, thereby making it possible to cool the object to be cooled even in a daytime solar environment. The light reflecting layer has the effect of reflecting, toward the infrared radiation layer, not only the light that has passed through the infrared radiation layer but also the light that is emitted from the infrared radiation layer toward the side where the light reflecting layer is present. However, in the following description, it will be explained that the purpose of providing the light reflecting layer is to reflect the light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer.

[0005] Furthermore, by providing an adjacent-side protective layer located on the side of the light-reflecting layer adjacent to the infrared radiation layer and a distant-side protective layer located on the side of the light-reflecting layer away from the infrared radiation layer, it is possible to prevent discoloration of silver and silver alloys due to moisture, and to ensure that the light-reflecting layer properly reflects light.

[0006] Conventional examples of radiative cooling films include those in which the adjacent-side protective layer and the distant-side protective layer are made of acrylic resin, silicone resin, fluororesin, or oxide film (SiO2, Al2O3) (see, for example, Patent Document 1 (Fig. 15)). Moreover, Fig. 17 of Patent Document 1 describes a radiative cooling film in which a film layer made of PET (polyethylene terephthalate) is provided as a separating-side protective layer, a light-reflecting layer and an adjacent-side protective layer are sequentially formed on the film layer, and the infrared radiative layer and the adjacent-side protective layer are bonded together with an adhesive layer (glue layer). [Prior art documents] [Patent documents]

[0007] [Patent Document 1] International Publication No. 2020 / 195743 Summary of the Invention [Problem to be solved by the invention]

[0008] As an example of the use of radiative cooling films, adhesive (glue) is applied to the back of the film body and then attached to the target (the construction target to be cooled), such as the exterior surface of a car. However, conventional films (radiative cooling films) have little extensibility (ease of stretching), so the shapes they can be attached to are limited to flat or quadratic curved surfaces, and it is not possible to fine-tune the attachment state by stretching the film body during attachment.

[0009] That is, since silver or silver alloy has ductility (ease of stretching), the light reflective layer has ductility (ease of stretching). However, in conventional radiative cooling films, the materials forming the adjacent-side protective layer and the separating-side protective layer are difficult to stretch, for example, acrylic resin is a material with high tensile strength that breaks when stretched slightly, and therefore conventional film bodies (radiative cooling films) have little ductility (ease of stretching). Incidentally, silicone resin has extremely poor adhesion to silver (silver alloy), and is therefore unsuitable as a material for forming the adjacent-side protective layer and the spaced-side protective layer.

[0010] Furthermore, even when the separating-side protective layer is made of PET, PET is a material that is difficult to stretch, and so similarly the extensibility (ease of stretching) of the film body (radiative cooling film) will be low.

[0011] As described above, conventional radiative cooling films have poor conformability to the shape of the object to which they are attached (the object of application), which limits the objects to which they can be attached (the object of application). In other words, they cannot provide radiative cooling performance to the surfaces of various objects. Incidentally, if the film body (radiative cooling film) has low extensibility (ease of stretching), it is prone to wrinkles (folded creases) when folded, making it difficult to use.

[0012] The present invention has been made in view of the above circumstances, and its purpose is to provide a radiative cooling film that has improved conformability to the shape of the object to which it is attached. [Means for solving the problem]

[0013] The radiative cooling film of the present invention is configured in a film body including an infrared emitting layer that emits infrared light from a emitting surface, a light reflecting layer made of silver or a silver alloy and located on the side of the infrared emitting layer opposite to the side where the emitting surface exists, an adjacent-side protective layer located on the side of the light reflecting layer adjacent to the infrared emitting layer, and a distant-side protective layer located on the side of the light reflecting layer away from the infrared emitting layer, The infrared radiation layer is a resin material layer whose thickness is adjusted to emit thermal radiation energy in a wavelength band of 8 μm to 14 μm that is greater than the absorbed solar light energy, and its characteristic configuration is as follows: The resin material forming the adjacent-side protective layer and the spaced-side protective layer is any one of a urethane resin, an acrylic urethane resin, and a polyolefin resin. the law of nature, The film body has a tensile strength of 140 N / 2.5 cm or less at room temperature and an elongation at break of 30% or more, The thickness of the light-reflecting layer is 70 nm or more and 300 nm or less. It's at the point.

[0014] First, the fact that the object to be cooled can be cooled even in a daytime solar radiation environment will be explained. That is, sunlight incident from the emitting layer of the infrared emitting layer in the film body passes through the resin material layer, is reflected by the light reflecting layer located on the opposite side to the side where the emitting surface of the resin material layer is present, and is then released outside the system from the emitting surface. In this specification, when simply referring to light, the concept of light includes ultraviolet light (ultraviolet rays), visible light, and infrared light. When these are described in terms of the wavelength of light as electromagnetic waves, they include electromagnetic waves with wavelengths of 10 nm to 20,000 nm (electromagnetic waves of 0.01 μm to 20 μm).

[0015] Furthermore, heat transferred (heat input) to the film body is converted into infrared rays in the resin material layer serving as the infrared radiation layer, and is released outside the system from the radiation surface. In this way, the film body reflects sunlight irradiating onto it and can also radiate heat transferred to the film body (for example, heat transferred from the atmosphere or heat transferred from the object being cooled by the film body) outside the system as infrared light.

[0016] The thickness of the resin material layer is adjusted so that it emits greater thermal radiation energy in the wavelength range of 8 μm to 14 μm than the absorbed solar energy, so that the light-reflecting layer appropriately reflects sunlight, while still providing cooling functionality even in a daytime solar radiation environment.

[0017] To explain further the ability of the light-reflecting layer to appropriately reflect sunlight, a light-reflecting layer made of silver or a silver alloy has reflectance characteristics of 90% or more at wavelengths of 0.4 μm to 0.5 μm and 96% or more at wavelengths longer than 0.5 μm, and can appropriately reflect sunlight. That is, the solar spectrum exists in the wavelength range from 0.295 μm to 4 μm, and the intensity increases as the wavelength increases from 0.4 μm, and the intensity is particularly high in the wavelength range from 0.5 μm to 2.5 μm. The light-reflecting layer made of silver or a silver alloy has reflective properties that show a reflectance of 90% or more in the wavelength range of 0.4 μm to 0.5 μm and a reflectance of 96% or more at wavelengths longer than 0.5 μm, so the light-reflecting layer absorbs only about 5% or less of the solar energy.

[0018] As a result, the solar energy absorbed by the light-reflecting layer at noon in summer was 50 W / m 2 The thickness can be set to about 100 μm or less, and radiation cooling by the resin material layer can be performed satisfactorily. In this specification, unless otherwise specified, the spectrum of sunlight is based on the AM1.5G standard. As described above, the object to be cooled can be cooled by radiative cooling even in a daytime solar radiation environment.

[0019] Furthermore, since the light-reflecting layer is provided with an adjacent-side protective layer and a distant-side protective layer, deterioration of the light-reflecting layer can be suppressed, such as by preventing moisture from reaching the silver or silver alloy that constitutes the light-reflecting layer, thereby preventing the silver or silver alloy from discoloring due to moisture, thereby allowing the light-reflecting layer to reflect light appropriately. Incidentally, the adjacent-side protective layer also prevents radicals generated in the resin material layer from reaching the silver or silver alloy that forms the light-reflecting layer, and also prevents the silver or silver alloy of the light-reflecting layer from discoloring in a short period of time due to radicals generated in the resin material layer reaching the silver or silver alloy that forms the light-reflecting layer.

[0020] According to the characteristic configuration of the radiative cooling film of the present invention, the resin material forming the adjacent-side protective layer and the distant-side protective layer is any one of urethane resin, acrylic urethane resin, and polyolefin resin, so that the film body (radiative cooling film) can be provided with extensibility (ease of stretching).

[0021] In other words, the light-reflecting layer has ductility (ease of stretching) because silver or a silver alloy is malleable, and by making the infrared radiation layer a resin material layer using a resin material that has ductility (ease of stretching), the infrared radiation layer can be made ductile (ease of stretching). In addition, urethane resin, acrylic urethane resin, and polyolefin resin have extensibility (ease of stretching), and therefore can provide extensibility (ease of stretching) to the adjacent-side protective layer and the separating-side protective layer. As a result, the film body (radiative cooling film) can be made extensible (easily stretchable), and its ability to conform to the shape of the object to which it is attached can be improved.

[0022] In short, the characteristic configuration of the radiative cooling film of the present invention can increase the shape-following ability of the film to the object to which it is attached.

[0023] Furthermore, The radiative cooling filter of the present invention M is The film has a tensile strength of 140 N / 2.5 cm or less at room temperature and an elongation at break of 30% or more. This characteristic configuration provides the following advantages. In the present invention, room temperature is defined as 23°C (the temperature defined by JIS K 6732). Furthermore, since the adjacent-side protective layer and the separating-side protective layer are formed of urethane resin, acrylic urethane resin, or polyolefin resin and have sufficiently large extensibility (ease of stretching), in the present invention, the tensile strength and elongation at break (elongation limit) of the film body at room temperature are determined by the extensibility (ease of stretching) of the resin material layer (infrared radiation layer) and the light-reflecting layer.

[0024] In other words, since the tensile strength of the film body at room temperature is 140 N / 2.5 cm or less and the elongation at break (elongation limit) of the film body is 30% or more, it accurately increases the shape-following ability of the object to which it is attached (object to be applied) and suppresses the occurrence of creases.

[0025] To explain further, if the tensile strength per 2.5 cm of the film (JIS K 6732) is 70 N / 2.5 cm or less, the film will have excellent applicability to curved surfaces. When applying the film to a curved surface, the film is stretched while heated to 80°C or higher using a heat gun or similar device. When the film is heated to 80°C or higher, the tensile strength of the resin material layer (e.g., polyvinyl chloride resin mixed with plasticizer) generally drops to less than half of its normal temperature value. Therefore, considering that the film will be heated to 80°C or higher during application, it is desirable for the tensile strength at 23°C to be 140 N / 2.5 cm or less.

[0026] Furthermore, when attaching (sticking) a film body to an object to be attached (for example, a car hood or the edge of a truck container), a minimum elongation of 30% is required, and 30% elongation is sufficient for the attachment. Furthermore, if the film has an elongation of 30%, it can prevent wrinkles (creases) from forming when the film body is folded.

[0027] In short, the further characteristic configuration of the radiative cooling film of the present invention can accurately increase the conformability to the shape of the object to which it is attached, and can suppress the occurrence of creases.

[0028] Furthermore, The radiative cooling filter of the present invention M is The thickness of the light-reflecting layer is 70 nm or more and 300 nm or less. This characteristic configuration provides the following advantages.

[0029] In other words, when sunlight is to be reflected while the light-reflecting layer has the above-mentioned reflectance characteristics, i.e., a reflectance of 90% or more at wavelengths of 0.4 μm to 0.5 μm and a reflectance of 96% or more at wavelengths longer than 0.5 μm, it is desirable that the thickness of the light-reflecting layer be 50 nm or more. Furthermore, since a silver or silver alloy light-reflecting layer will break if stretched beyond 40%, considering that the light-reflecting layer will be stretched by 40% when applied to the curved surface of the film body, by making the thickness of the light-reflecting layer 70 nm or more, which is 1.4 times 50 nm, the light-reflecting layer can be provided with appropriate reflective properties even when applied to the film body in a stretched state.

[0030] Furthermore, if the light-reflecting layer were to break, the tensile strength of the light-reflecting layer would become zero. However, if the tensile strength of the light-reflecting layer accounts for a large proportion of the overall tensile strength of the film body, the change in the tensile strength of the film body would be large when the light-reflecting layer breaks, making it difficult to apply. If the tensile strength of the light-reflecting layer is set to 1 N / 2.5 cm or less, the proportion of the tensile strength of the film body as a whole (for example, if the tensile strength of the film body as a whole is 140 N / 2.5 cm, this will be 1% or less), and when the light-reflecting layer breaks, the change in the tensile strength of the film body will be small, which will reduce the difficulty of application.

[0031] In the case of silver or silver alloys, there is no change in tensile strength even when heated from room temperature to about 80°C. Therefore, it is desirable that the thickness of the light-reflecting layer be 300 nm or less, and that the tensile strength of the light-reflecting layer be 1 N / 2.5 cm or less.

[0032] In other words, the silver or silver alloy that makes up the light-reflecting layer will break if it is stretched by more than 40%, so while the light-reflecting layer is unlikely to break when the film is stretched during application, even if the light-reflecting layer does break, the change in the tensile strength of the film can be minimized, and the film can be maintained in a state that makes it easy to apply.

[0033] In summary, according to a further characteristic feature of the radiative cooling film of the present invention, the film body can be stretched and attached to the object while maintaining the light-reflecting layer with appropriate reflective properties even when the film body is stretched and attached to the object.

[0034] Further characteristic features of the radiative cooling film of the present invention are: The thickness of the resin material layer is The thickness is adjusted to have optical absorption characteristics in which the wavelength average of the optical absorptance in the wavelength range of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the optical absorptance in the wavelength range of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the optical absorptance in the wavelength range of 0.8 μm to 1.5 μm is within 1%, and the wavelength average of the optical absorptance in the wavelength range of 1.5 μm to 2.5 μm is 40% or less, and thermal radiation characteristics in which the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is 40% or more, The resin material layer has a tensile strength of 139 N / 2.5 cm or less, an elongation at break of 50% or more, and the tensile strength decreases with increasing temperature.

[0035] The wavelength average of the light absorptance in the wavelength range of 0.4 μm to 0.5 μm means the average value of the light absorptance for each wavelength in the range of 0.4 μm to 0.5 μm, and the same applies to the wavelength average of the light absorptance in the wavelength range of 0.5 μm to 0.8 μm, the wavelength average of the light absorptance in the wavelength range of 0.8 μm to 1.5 μm, and the wavelength average of the light absorptance in the wavelength range of 1.5 μm to 2.5 μm. Other similar terms, including emissivity, also mean similar average values, and the same applies hereinafter in this specification.

[0036] That is, the light absorptivity and emissivity (light emissivity) 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 absorbs as little sunlight as possible and emits large thermal radiation in the wavelength band of the so-called atmospheric window region (the region of light wavelengths from 8 μm to 14 μm).

[0037] Specifically, in terms of the light absorptance (light absorption characteristics) of sunlight in the resin material layer, the wavelength average light absorptance in the wavelength range of 0.4 μm to 0.5 μm must be 13% or less, the wavelength average light absorptance in the wavelength range of 0.5 μm to 0.8 μm must be 4% or less, the wavelength average light absorptance in the wavelength range of 0.8 μm to 1.5 μm must be within 1%, and the wavelength average light absorptance in the wavelength range of 1.5 μm to 2.5 μm must be 40% or less. Note that for the light absorptance in the wavelength range of 2.5 μm to 4 μm, it is sufficient if the wavelength average light absorptance is 100% or less. When the light absorption rate is distributed in this way, the light absorption rate of sunlight is 10% or less, which corresponds to 100W or less in terms of energy.

[0038] In other words, the light absorption rate of sunlight increases as the thickness of the resin material layer increases. If the resin material layer is made thick, 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 This becomes: The sunlight absorption in the light-reflecting layer is 50W / m 2 It is preferable that: Therefore, the sum of the solar light absorption in the resin material layer and the light reflective layer is 150 W / m 2 As described above, it is preferable to use a resin material layer that has a small absorption rate near the peak value of the solar spectrum.

[0039] Furthermore, in terms of the emissivity (thermal radiation characteristics) of the resin material layer for emitting infrared light, the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm must be 40% or more. That is, 50W / m absorbed by the light-reflecting layer 2 In order to emit the same amount of thermal radiation as sunlight from a resin material layer into space, the resin material layer needs to emit more thermal radiation than that. For example, when the outside temperature is 30°C, the maximum thermal radiation of the atmospheric window with wavelengths from 8 μm to 14 μm is 200 W / m 2(calculated with an emissivity of 1). This value can be obtained on clear days in dry environments with thin air, such as high mountains. In lowlands, the atmosphere is thicker than in high mountains, so the wavelength band of the atmospheric window narrows and the transmittance decreases. Incidentally, this is called "the atmospheric window narrowing."

[0040] In addition, the environment in which the radiative cooling film is actually used may be humid, and in that case the atmospheric window will also be narrow. When used in lowlands, the thermal radiation generated in the atmospheric window area is 160 W / m at 30°C under good conditions. 2 (calculated assuming emissivity of 1). Also, when there is haze or smog in the sky, as is common in Japan, the atmospheric window becomes even narrower, and radiation into space is 125 W / m 2 It will be about that amount.

[0041] In consideration of this situation, the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is set to 40% or more (thermal radiation intensity in the atmospheric window band is 50 W / m 2 Without this, it cannot be used in low altitude areas in the mid-latitudes. Therefore, by adjusting the thickness of the resin material layer so that it falls within the above-mentioned optical specification range, the heat output at the atmospheric window becomes greater than the heat input due to sunlight absorption, making it possible to achieve radiative cooling outdoors even in a daytime solar radiation environment.

[0042] Furthermore, the resin material layer has a tensile strength of 139 N / 2.5 cm or less, an elongation at break of 50% or more, and the tensile strength decreases with increasing temperature. Therefore, even if the thickness of the resin material layer is increased to improve the ease of attaching the film body to the object to be attached, when attaching the film body to a curved surface, the film body can be attached well to the curved surface by stretching it while heating it to 80°C or more using a heat gun or the like.

[0043] In short, according to the further characteristic configuration of the radiative cooling film of the present invention, the heat output at the atmospheric window is greater than the heat input due to sunlight absorption, so radiative cooling can be performed outdoors even under solar radiation, and the film body can be well attached to curved surfaces.

[0044] Further characteristic features of the radiative cooling film of the present invention are: The resin material forming the resin material layer is a vinyl chloride resin mixed with a plasticizer, and the thickness of the resin material layer is 14 μm or more and 330 μm or less. The vinyl chloride resin used in the present invention is a homopolymer of vinyl chloride or vinylidene chloride or a copolymer of vinyl chloride or vinylidene chloride, and can be produced by a conventionally known polymerization method.

[0045] That is, if vinyl chloride resin has a thickness of 10 μm or more, it can obtain sufficient thermal radiation in the atmospheric window region, and as a result, it can provide appropriate radiative cooling outdoors even in a solar radiation environment. In other words, vinyl chloride resin has thermal radiation properties equivalent to those of fluororesin and silicone rubber, which obtain large thermal radiation in the atmospheric window region, and is considerably cheaper than these resins, so it is effective for inexpensively constructing a film (radiative cooling film) whose temperature drops below the ambient temperature under direct sunlight.

[0046] Moreover, since a plasticizer is mixed into the vinyl chloride resin, the resin material layer has sufficient extensibility (ease of stretching), and as a result, the radiative cooling film has sufficient extensibility (ease of stretching). Therefore, the film body can be smoothly attached to the object while being stretched.

[0047] By the way, vinyl chloride resins can be made soft by adding plasticizers, and when they come into contact with other objects, they can flexibly change shape to fit the object, avoiding damage and allowing them to maintain a beautiful appearance for a long period of time.By the way, thin film fluororesins are hard, so they cannot flexibly change shape when they come into contact with other objects, are easily damaged, and it is difficult to maintain a beautiful appearance. Furthermore, by adding a plasticizer to vinyl chloride resin, even if it is scratched, it can be deformed by heating it to 80°C or above, eliminating the surface scratches and smoothing it out, meaning it can self-repair. Fluorocarbon resin and silicone rubber do not have this property. This property of soft vinyl chloride resin allows it to maintain a clean state for a long period of time. This leads to the maintenance of radiative cooling performance over a long period of time. In this way, by adding a plasticizer, the durability of the film body (radiative cooling film) is improved. Furthermore, vinyl chloride resins are flame retardant and difficult to biodegrade, making them suitable as resin materials for forming the resin material layer of radiative cooling films that are used outdoors for long periods of time.

[0048] Furthermore, the silver or silver alloy light-reflecting layer will break if it is stretched by more than 40%, and taking into consideration that the film body will be stretched by 40% when applied to the curved surface of the film body, the thickness of the resin material layer is made 14 nm or more, which is 1.4 times 10 nm, so that the resin material layer can have appropriate thermal radiation properties even when the film body is applied in a stretched state.

[0049] Furthermore, since the thickness of the resin material layer formed from vinyl chloride resin is 330 μm or less, the tensile strength of the resin material layer can be 139 N / 2.5 cm or less. As described above, when applying to a curved surface, the film body can be heated to 80°C or more using a heat gun or the like while being stretched, allowing the film body to be applied to the curved surface well.

[0050] In short, the further characteristic configuration of the radiative cooling film of the present invention makes it possible to reduce the cost of the film body that can perform radiative cooling outdoors even under solar radiation, and also makes it possible to apply the film body to curved surfaces, especially three-dimensional curved surfaces, with good performance.

[0051] A further characteristic feature of the radiative cooling film of the present invention is that the thickness of the resin material layer is 50 μm or more and 330 μm or less.

[0052] In other words, since the thickness of the resin material layer formed from vinyl chloride resin is 50 μm or more, even if the film body is applied in a state where it is stretched by 40%, the thickness of the resin material layer will be approximately 36 μm, which will provide it with sufficiently large thermal radiation properties. As a result, proper radiative cooling can be achieved outdoors even in a solar radiation environment. Incidentally, since the thickness of the resin material layer formed from vinyl chloride resin is 330 μm or less, the film body can be applied to curved surfaces satisfactorily as described above.

[0053] In short, according to the further characteristic configuration of the radiative cooling film of the present invention, it can perform appropriate radiative cooling outdoors even under solar radiation environment.

[0054] A further characteristic feature of the radiative cooling film of the present invention is that the plasticizer comprises one or more compounds selected from the group consisting of phthalate esters, aliphatic dibasic acid esters, and phosphate esters.

[0055] In other words, since the plasticizer mixed into the vinyl chloride resin is one or more compounds selected from the group consisting of phthalate esters, aliphatic dibasic acid esters, and phosphate esters, the plasticizer is less likely to absorb the ultraviolet rays contained in sunlight (ultraviolet light with wavelengths of 295 nm to 400 nm), and the weather resistance of the vinyl chloride resin mixed with the plasticizer can be appropriately improved.

[0056] In other words, when a plasticizer mixed into a vinyl chloride resin absorbs ultraviolet light, the hydrolysis of the plasticizer progresses, causing the vinyl chloride resin to undergo dechlorination, discoloration (brown), and there is a risk of a decrease in mechanical strength. However, because the plasticizer becomes less able to absorb the ultraviolet light contained in sunlight, the weather resistance of the vinyl chloride resin mixed with the plasticizer can be improved.

[0057] In summary, the characteristic configuration of the radiative cooling film of the present invention provides a radiative cooling film that can improve weather resistance.

[0058] A further characteristic feature of the radiative cooling film of the present invention is that the plasticizer is mixed in the range of 7 parts by weight or more and 50 parts by weight or less with respect to 100 parts by weight of the vinyl chloride resin.

[0059] In other words, the plasticizer mixed into the vinyl chloride resin is in the range of 7 parts by weight or more and 50 parts by weight or less per 100 parts by weight of the vinyl chloride resin, so that the resin material layer is given appropriate extensibility (ease of stretching) while suppressing a decrease in the durability of the resin material layer.

[0060] In other words, since the plasticizer mixed into the vinyl chloride resin is 7 parts by weight or more per 100 parts by weight of the vinyl chloride resin, the resin material layer can be given appropriate extensibility (ease of stretching). Furthermore, since the plasticizer mixed into the vinyl chloride resin is 50 parts by weight or less per 100 parts by weight of the vinyl chloride resin, a decrease in the durability of the resin material layer can be suppressed.

[0061] In short, according to the further characteristic configuration of the radiative cooling film of the present invention, the resin material layer can be provided with appropriate extensibility (ease of stretching) and the deterioration of the durability of the resin material layer can be suppressed.

[0062] A further characteristic feature of the radiative cooling film of the present invention is that the plasticizer is mixed in the range of 15 to 50 parts by weight relative to 100 parts by weight of the vinyl chloride resin.

[0063] That is, since the plasticizer mixed into the vinyl chloride resin is 15 parts by weight or more per 100 parts by weight of the vinyl chloride resin, the extensibility (ease of stretching) of the resin material layer can be sufficiently improved.

[0064] In short, according to the further characteristic configuration of the radiative cooling film of the present invention, the extensibility (ease of stretching) of the resin material layer can be sufficiently improved.

[0065] A further characteristic feature of the radiative cooling film of the present invention is that the thicknesses of the adjacent-side protective layer and the distant-side protective layer are not less than 300 nm and not more than 40 μm.

[0066] In other words, since the thickness of each of the adjacent-side protective layer and the separating-side protective layer is 300 nm or more, it is possible to appropriately prevent moisture that passes through the resin material layer from reaching the silver or silver alloy that forms the light-reflecting layer, and to appropriately prevent moisture from the object to be cooled (for example, the object to which the film body is attached) from reaching the silver or silver alloy that forms the light-reflecting layer, thereby appropriately suppressing deterioration of the light-reflecting layer. Furthermore, since the thickness of the adjacent-side protective layer is 300 nm or more, radicals generated in the resin material layer are appropriately prevented from reaching the silver or silver alloy that forms the light-reflecting layer.

[0067] Furthermore, since the thickness of the adjacent-side protective layer and the separating-side protective layer is 40 μm or less, the adjacent-side protective layer and the separating-side protective layer increase the insulating properties of the film body, thereby preventing a decrease in the radiative cooling performance of the film body.

[0068] In summary, according to the further characteristic configuration of the radiative cooling film of the present invention, the deterioration of the light reflecting layer can be appropriately suppressed, and the deterioration of the radiative cooling performance of the film body can be suppressed.

[0069] A further characteristic configuration of the radiative cooling film of the present invention is that the resin material layer and the adjacent-side protective layer are bonded together by an adhesive layer, The adhesive layer is formed from any one of a urethane resin adhesive, an acrylic urethane resin adhesive, and a polyolefin resin adhesive.

[0070] That is, since the resin material layer and the adjacent-side protective layer are bonded together by an adhesive layer, for example, the separating-side protective layer, the light-reflecting layer, and the adjacent-side protective layer can be integrally formed in a laminated state, and a separately manufactured resin material layer and the adjacent-side protective layer can be bonded together by an adhesive layer, thereby enabling the resin material layer, the adjacent-side protective layer, the light-reflecting layer, and the separating-side protective layer to be formed in a well-laid state.

[0071] The thickness of the adhesive layer is preferably 1 μm or more and 30 μm or less. In addition, since the urethane resin adhesive, acrylic urethane resin adhesive, and polyolefin resin adhesive that form the adhesive layer have particularly excellent extensibility (ease of stretching), such as the elongation at break of urethane resin being in the range of 100% to 10,000%, in the present invention, even when an adhesive layer is present, the tensile strength and elongation at break (elongation limit) of the film body at room temperature are determined by the extensibility (ease of stretching) of the resin material layer (infrared radiation layer) and the light-reflecting layer.

[0072] Incidentally, when an adhesive layer is located between the resin material layer and the adjacent-side protective layer, radicals will also be generated from the adhesive layer, but the adjacent-side protective layer can prevent the radicals generated in the adhesive layer from reaching the light-reflecting layer.

[0073] In summary, according to a further characteristic feature of the radiative cooling film of the present invention, the resin material layer, the adjacent-side protective layer, the light-reflecting layer, and the distant-side protective layer can be well formed in a laminated state.

[0074] The characteristic configuration of the method for using the radiative cooling film of the present invention is the method for using the radiative cooling film described above, The film is used in a state where the elongation of the film is 40% or less.

[0075] In other words, the silver and silver alloy in the light-reflecting layer will break if it stretches beyond 40%, so by using the film body in a state where the stretch is within 40%, the film body can be successfully attached to the object to be attached while preventing the light-reflecting layer from breaking.

[0076] In short, according to the characteristic configuration of the method of using the radiative cooling film of the present invention, the film body can be well attached to the attachment target while suppressing breakage of the light reflecting layer.

[0077] The method for producing a radiative cooling film of the present invention is the method for producing the radiative cooling film described above, a release layer, the spacing-side protective layer, the reflective layer, and the adjacent-side protective layer are sequentially laminated on an upper portion of a substrate to form a reflective layer-side laminate; The resin material layer is separately formed, the resin material layer and the reflective layer-side laminate are bonded together by the adhesive layer; Thereafter, the release layer is separated from the separating-side protective layer.

[0078] That is, when preparing a film body in which a resin material layer, an adjacent-side protective layer, a light-reflecting layer, and a separating-side protective layer are laminated, a release layer, a separating-side protective layer, a reflective layer, and an adjacent-side protective layer are laminated in this order on top of a substrate to form a reflective layer-side laminate. In addition, a resin material layer is separately formed.

[0079] Next, the resin material layer and the reflective layer side laminate are bonded together with an adhesive layer. Thereafter, the release layer is removed from the separating-side protective layer, and the substrate is separated. The release layer is preferably made of either a silicone resin or a fluororesin, and the substrate can be made of ethylene terephthalate resin (PET).

[0080] In other words, by using a procedure in which the separating-side protective layer, the light-reflecting layer, and the adjacent-side protective layer are integrally formed in a laminated state, and a separately manufactured resin material layer and the adjacent-side protective layer are bonded together with an adhesive layer, the resin material layer, the adjacent-side protective layer, the light-reflecting layer, and the separating-side protective layer can be formed in a laminated state. In this case, when forming the separating-side protective layer, the light-reflecting layer, and the adjacent-side protective layer integrally in a laminated state, by using a substrate with an appropriate thickness and appropriate shape retention, the release layer, the separating-side protective layer, the reflective layer, and the adjacent-side protective layer are sequentially laminated on top of the substrate to form a reflective layer-side laminate, which makes it possible to form the separating-side protective layer, the light-reflecting layer, and the adjacent-side protective layer in a well-laid state.

[0081] After the resin material layer and the reflective layer side laminate are bonded together with the adhesive layer, the release layer is removed from the separating side protective layer to separate the substrate, thereby forming a film body in which the resin material layer, adjacent side protective layer, light reflecting layer and separating side protective layer are laminated.

[0082] In short, the characteristic features of the method for producing a radiative cooling film allow for good formation of a film body.

[0083] Further characteristic features of the method for producing a radiative cooling film of the present invention are as follows: The resin material layer and the reflective layer-side laminate are bonded together by the adhesive layer, and then the release layer is separated from the separation-side protective layer.

[0084] In other words, the resin material layer and the reflective layer side laminate are bonded together with an adhesive layer, and then the release layer is removed from the separating side protective layer to separate the substrate, thereby forming a film body in which the resin material layer, adjacent side protective layer, light reflecting layer and separating side protective layer are laminated.

[0085] In short, the characteristic features of the method for producing a radiative cooling film allow for good formation of a film body. [Brief explanation of the drawings]

[0086] [Figure 1] FIG. 1 illustrates the basic configuration of a radiative cooling film. [Figure 2] FIG. 10 is a diagram showing the relationship between the light absorptance of a resin material and wavelength. [Figure 3] FIG. 1 is a diagram showing the emissivity spectrum of vinyl chloride resin. [Figure 4] FIG. 1 is a diagram showing the emissivity spectrum of vinylidene chloride resin. [Figure 5] FIG. 1 is a diagram showing a specific configuration of a radiative cooling film. [Figure 6] FIG. 1 illustrates the fabrication procedure for a radiative cooling film. [Figure 7] 1 is a table showing the relationship between the amount of plasticizer added and tensile strength. [Figure 8] 1 is a table showing the relationship between the amount of plasticizer added and the elongation limit. [Figure 9] FIG. 10 is a diagram showing the transmittance of a resin material layer to which an ultraviolet absorber is added. [Figure 10] FIG. 1 shows the light reflectance spectrum of a silver-based light-reflecting layer. [Figure 11] FIG. 1 is a diagram showing the relationship between light transmittance and wavelength of polyethylene. [Figure 12] FIG. 1 is a diagram illustrating a test configuration. [Figure 13] FIG. 10 is a diagram showing test results when the adjacent-side protective layer is made of polyethylene. [Figure 14] FIG. 10 is a diagram showing test results when the adjacent-side protective layer is made of ultraviolet-absorbing acrylic. [Figure 15] FIG. 1 shows the emissivity spectrum of polyethylene. [Figure 16] FIG. 10 is a diagram showing test results in which a plasticizer is mixed into a vinyl chloride resin. [Figure 17] FIG. 1 is a diagram showing the relationship between wavelength and absorbance of a plasticizer. [Figure 18] FIG. 1 is a diagram showing the relationship between wavelength and absorbance of a plasticizer. [Figure 19] FIG. 1 is a diagram showing the relationship between wavelength and absorbance of a plasticizer. [Figure 20] FIG. 1 is a diagram showing the relationship between wavelength and absorbance of a plasticizer. [Figure 21] 10A and 10B are diagrams illustrating a configuration in which the front and back surfaces of a resin material layer are uneven. [Figure 22] 10A and 10B are diagrams illustrating a configuration in which a filler is mixed into a resin material layer. [Figure 23]1 is a table showing the relationship between plasticizer, tensile strength, and elongation at break. DETAILED DESCRIPTION OF THE INVENTION

[0087] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic structure of radiative cooling film] As shown in Fig. 1, the radiative cooling film CP is composed of a film body F including an infrared emitting layer A that emits infrared light IR from an emitting surface H, a light reflecting layer B located on the side of the infrared emitting layer A opposite to the side where the emitting surface H exists, an adjacent-side protective layer Du on the surface of the light reflecting layer B adjacent to the infrared emitting layer A, and a distant-side protective layer Ds on the surface of the light reflecting layer B away from the infrared emitting layer A.

[0088] The film body F has a tensile strength of 140 N / 2.5 cm or less at room temperature and an elongation at break of 30% or more. In this embodiment, the infrared radiation layer A has a tensile strength of 139 N / 2.5 cm or less at room temperature and an elongation at break of 50% or more, and the light-reflecting layer B has a tensile strength of 1 N / 2.5 cm or less at room temperature and an elongation at break of 30% or more. By the way, room temperature is defined as 23°C (the temperature specified in JIS K 6732).

[0089] The light-reflecting layer B is made of silver or a silver alloy and reflects light L, such as sunlight, that has passed through the infrared radiation layer A and the adjacent-side protective layer Du. Its reflection characteristics are such that the reflectance is 90% or more for wavelengths of 0.4 μm to 0.5 μm and 96% or more for wavelengths longer than 0.5 μm. The solar spectrum spans wavelengths from 0.295 μm (295 nm) to 4 μm (4000 nm), with intensity increasing as wavelengths increase from 0.4 μm (400 nm), and is particularly intense from 0.5 μm (500 nm) to 1.8 μm (1800 nm).

[0090] In this embodiment, light L includes ultraviolet light (ultraviolet light), visible light, and infrared light, and when expressed in terms of the wavelength of light as electromagnetic waves, includes electromagnetic waves with wavelengths of 10 nm to 20,000 nm (electromagnetic waves of 0.01 μm to 20 μm). In this specification, the wavelength range of ultraviolet light (ultraviolet light) is defined as a range of 295 nm (0.295 μm) or more and 400 nm (0.4 μm) or less.

[0091] The light-reflecting layer B exhibits a reflectivity of 90% or more in the wavelength range of 0.4 μm to 0.5 μm, and a reflectivity of 96% or more for wavelengths longer than 0.5 μm. This enables the radiative cooling film CP (film body F) to reduce the solar energy absorbed by the light-reflecting layer B to 5% or less. In other words, the solar energy absorbed at noon in summer can be reduced to about 50 W.

[0092] The infrared radiation layer A is configured as a resin material layer J made of vinyl chloride resin with a thickness adjusted to emit thermal radiation energy greater than the absorbed solar energy in the wavelength band of 8 μm to 14 μm. The vinyl chloride resin used in the present invention is a homopolymer of vinyl chloride or vinylidene chloride or a copolymer of vinyl chloride or vinylidene chloride, and is produced by a conventionally known polymerization method.

[0093] Although details of the resin material layer J will be described later, in this embodiment, the resin material forming the resin material layer J is a vinyl chloride resin mixed with a plasticizer. In other words, the resin material forming the resin material layer J is a vinyl chloride resin mixed with a resin plasticizer, or a vinylidene chloride resin mixed with a plasticizer. PVC resins containing plasticizers have excellent ductility (ease of stretching) and exhibit the property of decreasing tensile strength as the temperature rises.

[0094] Therefore, the radiative cooling film CP (film body F) is configured so that a part of the light L incident on the radiative cooling film CP is reflected by the radiation surface H of the infrared radiation layer A, and the light (sunlight, etc.) that has passed through the resin material layer J and the adjacent-side protective layer Du is reflected by the light reflection layer B and escapes from the radiation surface H to the outside.

[0095] The radiative cooling film CP is configured to cool the object to be cooled E by converting the heat input from the object to be cooled E, which is located on the opposite side of the light reflecting layer B from the side where the resin material layer J is present, into infrared light IR by the resin material layer J and radiating it.

[0096] That is, the radiative cooling film CP (film body F) is configured to reflect the light L irradiated onto the radiative cooling film CP, and to radiate the heat transferred to the radiative cooling film CP (film body F) (for example, heat transferred from the atmosphere or the object to be cooled E) to the outside as infrared light IR. Furthermore, the resin material layer J, adjacent-side protective layer Du, light-reflecting layer B, and spacing-side protective layer Ds are configured to have extensibility, so that the radiative cooling film CP (film body F) is configured to have extensibility.

[0097] In addition, the radiative cooling film CP (film body F) is used to implement a radiative cooling method in which infrared light IR is radiated from the radiation surface H on the opposite side to the surface of the resin material layer J that is in contact with the light-reflecting layer B. Specifically, the radiation surface H is directed toward the sky, and the radiation cooling method is implemented in which infrared light IR is radiated from the radiation surface H that faces the sky.

[0098] The target (cooling target E) to which the radiative cooling film CP (radiative cooling film) of the present invention can be attached can be any object that requires cooling, such as the outer surface of various tents (membrane materials), the outer surface of boxes that store electrical equipment, the outer surface of containers for transporting goods, the outer surface of milk tanks that store milk, the outer surface of the milk storage section of a milk tanker truck, etc. Furthermore, the radiative cooling film CP (film body) of the present invention can be attached to existing objects to easily exert its radiative cooling capacity, such as by applying glue and wrapping it around the periphery of a car, the outer wall of a warehouse or building, or the periphery of a helmet.

[0099] [Outline of resin material layer] The light absorptivity and emissivity (light emissivity) of the resin material (vinyl chloride resin) that forms the resin material layer J change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer J so that it absorbs as little sunlight as possible and emits large thermal radiation in the so-called atmospheric window wavelength band (wavelength band from 8 μm to 14 μm).

[0100] Specifically, the thickness of the resin material layer J is adjusted to have light absorption characteristics in which the wavelength average of the light absorptance in the wavelength range of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorptance in the wavelength range of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the light absorptance in the wavelength range of 0.8 μm to 1.5 μm is within 1%, and the wavelength average of the light absorptance in the wavelength range of 1.5 μm to 2.5 μm is 40% or less, and thermal radiation characteristics in which the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is 40% or more.

[0101] In terms of the light absorption rate of sunlight, the light absorption rate of resin material increases as the film thickness of the resin material increases. When the resin material is made thick, 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 The solar light absorption in the adjacent protective layer Du and the light-reflecting layer B is 50 W / m 2 The sum of the solar light absorption in the resin material layer J, the adjacent-side protective layer Du, and the light-reflecting layer B is 150 W / m 2 The temperature is below 100°C, and cooling proceeds if the atmospheric conditions are good. As described above, it is preferable to use a resin material that forms the resin material layer J and that has a small light absorptance near the peak value of the solar spectrum.

[0102] Furthermore, from the viewpoint of infrared radiation (thermal radiation), the thickness of the resin material layer J needs to be adjusted to a thickness such that the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is 40% or more. 50 W / m absorbed by the adjacent protective layer Du and light-reflecting layer B 2 In order to release about this amount of thermal energy of sunlight from the resin material layer J into space through thermal radiation from the resin material layer J, the resin material layer J needs to emit more thermal radiation than this amount. For example, when the outside temperature is 30°C, the maximum thermal radiation of the atmospheric window between 8 μm and 14 μm is 200 W / m 2 (calculated with an emissivity of 1). This value can be obtained on clear days in dry environments with thin air, such as high mountains. In lowlands, the atmosphere is thicker than in high mountains, so the wavelength band of the atmospheric window narrows and the transmittance decreases. Incidentally, this is called "the atmospheric window narrowing."

[0103] In addition, the environment in which the radiative cooling film CP is actually used may be humid, and in that case the atmospheric window will be narrow. When used in lowlands, the thermal radiation generated in the atmospheric window area is 160 W / m at 30°C under good conditions. 2 (calculated with an emissivity of 1). When there is haze or smog in the sky, which is common in Japan, the atmospheric window becomes even narrower, and radiation into space is estimated at 125 W / m 2 It will be about that amount. In consideration of this situation, the wavelength average of the emissivity of wavelengths from 8 μm to 14 μm is set to 40% or more (thermal radiation intensity in the atmospheric window band is 50 W / m 2 ) it cannot be used in low altitude areas of the mid-latitudes.

[0104] Therefore, if the thickness of the resin material layer J is adjusted to fall within the optically specified range taking the above factors into consideration, the heat output at the atmospheric window will be greater than the heat input due to absorption of sunlight, and it will be possible to cool the temperature below the outside air temperature by radiative cooling outdoors even in a solar radiation environment.

[0105] In this embodiment, the thickness of the resin material layer J made of vinyl chloride resin is 14 μm or more and 330 μm or less. Preferably, the thickness of the resin material layer J made of vinyl chloride resin is 50 μm or more and 330 μm or less. By doing so, the resin material layer J made of vinyl chloride resin has a tensile strength of 139 N / 2.5 cm or less and an elongation at break (elongation limit) of 50% or more. Furthermore, the tensile strength of the resin material layer J made of vinyl chloride resin decreases with increasing temperature. For example, when heated to 80°C, the tensile strength of the resin material layer J made of vinyl chloride resin generally decreases to half or less compared to that at room temperature.

[0106] [Details of resin material] According to Kirchhoff's law, the emissivity (ε) and the light absorptance (A) are equal. The light absorptance can be calculated from the absorption coefficient (α) using the following formula (1) (hereinafter sometimes referred to as the light absorptance relational equation): A=1-exp(-αt) (1) where t is the film thickness. In other words, by adjusting the film thickness of the resin material layer J, it is possible to obtain a large thermal radiation in a wavelength band with a large absorption coefficient. When performing radiative cooling outdoors, it is recommended to use a material with a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the atmospheric window wavelength band. In addition, to suppress the absorption of sunlight, it is advisable to use a material that has no or a small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, especially 0.4 μm to 2.5 μm. As can be seen from the relationship between the absorption coefficient and absorptance (light absorptance relationship equation), the light absorptance (emissivity) changes depending on the film thickness of the resin material.

[0107] In order to lower the temperature below the surrounding atmosphere through radiative cooling in a solar radiation environment, if a material is selected that has a large absorption coefficient in the wavelength band of the atmospheric window and almost no absorption coefficient in the wavelength band of sunlight, then by adjusting the film thickness, it will absorb almost no sunlight but emit a lot of thermal radiation from the atmospheric window, meaning that it is possible to create a state in which the output from radiative cooling is greater than the input of sunlight.

[0108] The solar spectrum only contains wavelengths longer than 0.295 μm. Note that ultraviolet light is defined as the range of wavelengths shorter than 0.4 μm, visible light is defined as the range of wavelengths from 0.4 μm to 0.8 μm, near-infrared light is defined as the range of wavelengths from 0.8 μm to 3 μm, mid-infrared light is defined as the range of wavelengths from 3 μm to 8 μm, and far-infrared light is defined as the range of wavelengths longer than 8 μm.

[0109] Regarding the carbon-chlorine bond (C-Cl), the bond energy between carbon and chlorine in alkenes is 3.28 eV, and the wavelength is 0.378 μm, so they absorb a lot of ultraviolet light in sunlight, but have almost no absorption in the visible range. Figure 2 shows the absorption spectrum of a 100 μm thick vinyl chloride resin in the ultraviolet to visible region, and shows that light absorption increases at wavelengths shorter than 0.38 μm. Figure 2 shows the absorption spectrum of a 100 μm thick vinylidene chloride resin in the ultraviolet to visible region, and shows a slight increase in the absorption spectrum on the shorter wavelength side than 0.4 μm.

[0110] FIG. 2 also shows the absorptance spectrum of ethylene terephthalate resin (PET) with a thickness of 40 μm from the ultraviolet to the visible region, and the absorptance spectrum of polyethylene (olefin-based) from the ultraviolet to the visible region.

[0111] Figure 3 shows the emissivity of polyvinyl chloride resin (PVC) with carbon-chlorine bonds at the atmospheric window, and Figure 4 shows the emissivity of polyvinylidene chloride resin (PVDC) with carbon-chlorine bonds at the atmospheric window. Regarding the carbon-chlorine bond, the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. In addition, in the case of vinyl chloride resin, the electron-withdrawing effect of chlorine causes an absorption coefficient at a wavelength of around 10 μm, which is due to the bending vibration of the CH of the alkene contained in the main chain. The same is true for vinylidene chloride resin. Due to these effects, the wavelength average of the emissivity for a 10 μm thick film is 43% in the wavelength range from 8 μm to 14 μm, which falls within the wavelength average of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0112] As shown in Figure 3, in the case of vinyl chloride resin, even if the thickness exceeds 100 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of vinyl chloride resin, thermal radiation in the atmospheric window occurs within a depth of approximately 100 μm from the surface, and radiation from deeper parts does not escape to the outside. As shown in FIG. 4, it can be seen that vinylidene chloride resin is similar to vinyl chloride resin.

[0113] As described above, the thermal radiation from the atmospheric window region generated from the surface of the resin material occurs within a depth of approximately 100 μm from the surface. If the resin thickness increases beyond this, the cold generated by the radiative cooling film CP (film body F) will be insulated by the resin material, which does not contribute to thermal radiation. Consider fabricating a resin material layer J, which ideally does not absorb any sunlight, on top of the light-reflecting layer B. In this case, sunlight is absorbed only by the light-reflecting layer B of the radiative cooling film CP (film body F). The thermal conductivity of resin materials is generally about 0.2 W / m / K, and when calculations are made taking this thermal conductivity into account, if the thickness of the resin material layer J exceeds 20 mm, the temperature of the cooling surface (the surface of the light-reflecting layer B opposite the side where the resin material layer J is present) will rise.

[0114] Even if an ideal resin material that does not absorb sunlight at all exists, the thermal conductivity of resin materials is generally around 0.2 W / m / K, so if the thickness exceeds 20 mm, the light-reflecting layer B will be heated by sunlight, and the object to be cooled E placed on the light-reflecting layer side will be heated. In other words, the thickness of the resin material of the radiative cooling film CP (film body F) needs to be 20 mm or less.

[0115] [Thickness of the resin material layer] From the viewpoint of practical use of the radiative cooling film CP, it is better for the thickness of the resin material layer J to be thin. The thermal conductivity of resin materials is generally lower than that of metals, glass, etc. To effectively cool the object to be cooled E, it is better for the thickness of the resin material layer J to be the minimum necessary. The thicker the resin material layer J is, the greater the thermal radiation from the atmospheric window becomes, and once the thickness exceeds a certain value, the thermal radiation energy at the atmospheric window becomes saturated.

[0116] The film thickness at which saturation occurs depends on the resin material, but in the case of resins containing carbon-chlorine bonds, saturation occurs even at a thickness of 100 μm, and sufficient heat radiation can be obtained in the atmospheric window region even at a thickness of 50 μm. The thinner the resin material, the higher the thermal conductivity and the more effectively the temperature of the object to be cooled can be lowered, so in the case of resins containing carbon-chlorine bonds, a thickness of 50 μm or less reduces the insulating properties and allows for effective cooling of object E. In the case of carbon-chlorine bonds, a thickness of 100 μm or less allows for effective cooling of object E.

[0117] The benefit of making the film thinner is not just that it reduces heat insulation and makes it easier to transfer cold. It also reduces the absorption of near-infrared light from CH, CH2, and CH3, which are present in resins containing carbon-chlorine bonds. By making the film thinner, the amount of sunlight absorbed by these compounds can be reduced, which increases the cooling capacity of the radiative cooling film CP. From the above perspective, in the case of vinyl chloride resin, which is a resin containing carbon-chlorine bonds, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0118] As mentioned above, if the thickness of the resin material layer J is 10 μm or more, it can produce a radiative cooling effect under sunlight, but if it is assumed that the radiative cooling film CP (film body F) will be stretched by nearly 40% when applied, the thickness of the resin material layer J needs to be 14 μm or more, as mentioned above. And if the thickness of the resin material layer J is 50 μm or more, the resin material layer J can produce a sufficiently large radiative cooling effect. Furthermore, in order to make the tensile strength of the resin material layer J 139 N / 2.5 cm or less, the thickness of the resin material layer J must be 300 μm or less.

[0119] (Regarding the tensile strength of resin material layer J) Fig. 7 illustrates the relationship between the thickness (µm) and tensile strength (N / 2.5cm) of the resin material layer J. Specifically, Fig. 7 illustrates the relationship between the thickness (µm) and tensile strength (N / 2.5cm) of the resin material layer J while changing the amount (parts by weight) of DOP (di-2-ethylhexyl phthalate) added as a plasticizer to the resin material layer J (vinyl chloride resin).

[0120] 7, the upper limit of the parts by weight of DOP added to 100 parts by weight of the resin material layer J is 50 parts by weight. That is, the amount of plasticizer added is limited to 50 parts by weight from the viewpoint of durability. As shown in Figure 7, when the amount of plasticizer added is 50 parts by weight per 100 parts by weight of the resin material layer J, in order to achieve a tensile strength of 139 N / 2.5 cm or less, the upper limit of the thickness of the resin material layer J is approximately 330 μm, and it is even better to set the upper limit of the thickness of the resin material layer J to 320 μm. Incidentally, if the type of plasticizer changes, the relationship between the thickness (μm) and tensile strength (N / 2.5cm) of the resin material layer J can be determined by multiplying the plasticizing efficiency of the plasticizer by the weight part.

[0121] [Details of the light-reflecting layer] In order to provide the light reflecting layer B with the above-mentioned reflectance characteristics, the reflective material on the side where the emitting surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy. As shown in FIG. 10, if the light-reflecting layer B is made of silver as a base, the reflectance required for the light-reflecting layer B can be obtained.

[0122] When reflecting sunlight with the above-mentioned reflectance characteristics using only silver or a silver alloy, a thickness of 50 nm or more is required. Incidentally, silver and silver alloys will break if they are elongated by more than 40%, so the radiative cooling film CP (film body F) needs to be used with an elongation of 40% or less. In other words, the radiative cooling film CP of the present invention needs to be used with an elongation of the film body F of 40% or less.

[0123] Even if the light reflecting layer B expands by 40%, in order to ensure that the thickness of the light reflecting layer B is 50 nm, the thickness of the light reflecting layer B needs to be 70 nm or more. In order to make the tensile strength of the light reflecting layer B 1 N / 2.5 cm or less, the upper limit of the thickness of the light reflecting layer B is 0.3 μm. That is, in the radiative cooling film CP (film body F) of the present invention, the thickness of the light reflecting layer B is set to 70 nm or more and 0.3 μm or less.

[0124] Incidentally, the "silver alloy" may be an alloy in which copper, palladium, gold, zinc, tin, magnesium, nickel, or titanium is added to silver in an amount of, for example, about 0.4% to 4.5% by mass. A specific example is "APC-TR (made by Furuya Metal)," a silver alloy made by adding copper and palladium to silver.

[0125] Silver and silver alloys are vulnerable to rain and humidity and need to be protected from these and to prevent discoloration. To this end, an adjacent-side protective layer Du and a distant-side protective layer Ds are required to protect the silver and silver alloy, as shown in Figure 1. The adjacent-side protective layer Du and the distant-side protective layer Ds will be described in detail later.

[0126] [Plasticizer details] The plasticizer mixed into the vinyl chloride resin forming the resin material layer J is one or more compounds selected from the group consisting of phthalate esters, aliphatic dibasic acid esters, and phosphate esters. The amount of the plasticizer added is 7 parts by weight or more and 50 parts by weight or less relative to 100 parts by weight of the vinyl chloride resin, and preferably 15 parts by weight or more and 50 parts by weight or less.

[0127] The aliphatic dibasic acid ester as a plasticizer may be composed of one or more compounds selected from the group consisting 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, and succinic acid ester copolymers.

[0128] The aliphatic dibasic acid ester as the plasticizer is preferably an aliphatic dibasic acid and two molecules of a saturated aliphatic alcohol bonded together via an ester bond. The phthalate ester of the plasticizer is preferably formed by ester bonding between phthalic acid and two molecules of a saturated aliphatic alcohol. The phosphate ester as the plasticizer may be a phosphate triester or an aromatic phosphate ester.

[0129] <Details of phthalate esters> The phthalate esters are listed below. 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.

[0130] <Details of aliphatic dibasic acid esters> The aliphatic dibasic acid esters are listed below. Dibutyl adipate (DBA), diisobutyl adipate (DIBA), di-2-ethylhexyl adipate (DOA), diisononyl adipate (DINA), diisodecyl adipate (DIDA), bis-2-ethylhexyl azelaate (DOZ), dibutyl sebacate (DBS), di-2-ethylhexyl sebacate (DOS), diisononyl sebacate (DINS), diethyl succinate (DESU), and the like. Also, an aliphatic polyester having a molecular weight of 400 to 4000 synthesized by copolymerization (polyesterification) of a dibasic acid such as adipic acid with a diol (difunctional alcohol or glycol).

[0131] <Phosphate triester> The phosphoric acid triesters are listed below. Trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), tris(2-ethylhexyl) phosphate (TOP).

[0132] <Aromatic phosphate ester> The aromatic phosphate esters are listed below. Triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), tresyl diphenyl phosphate (CDP), 2-ethylhexyl diphenyl phosphate.

[0133] <Relationship between plasticizers and elongation limits> Figure 8 shows the relationship between the amount of plasticizer added (parts by weight) and the elongation limit (elongation at break) of the resin material layer J (vinyl chloride resin) for each of adipic acid polyester (aliphatic dibasic acid esters), di-2-ethylhexyl phthalate (DOP), and di-2-ethylhexyl adipate (DOA). Referring to Figure 8, when di-2-ethylhexyl adipate (DOA) is added as a plasticizer in an amount of 7 parts by weight or more, the elongation limit (elongation at break) is 40% or more, and the radiative cooling film CP (film body F) satisfies the condition for use with an elongation of 40% or less. Furthermore, when 15 parts by weight or more of plasticizer is added, the elongation limits (limit elongation) of each of adipic acid polyester, di-2-ethylhexyl phthalate (DOP), and di-2-ethylhexyl adipate (DOA) are reliably 40% or more, and the radiative cooling film CP (film body F) reliably meets the condition of being used with an elongation of 40% or less.

[0134] <Appropriate evaluation of plasticizers> Plasticizers for vinyl chloride resin include phthalate esters, aliphatic dibasic acid esters, phosphate triesters, 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 each plasticizer was mixed with 100 parts by weight of vinyl chloride and evaluated using a xenon weather test. The vinyl chloride resin was mixed with 0.5 parts by weight of a triazine-based ultraviolet absorber and a hindered amine-based light stabilizer per 100 parts by weight of vinyl chloride.

[0135] Representative phthalate esters include di-2-ethylhexyl phthalate (DOP) and diisodecyl phthalate (DIDP). Representative aliphatic dibasic acid esters include di-2-ethylhexyl adipate (DOA), butanediol adipate copolymer (average molecular weight of about 1000), and diisononyl adipate (DINA). A representative phosphate triester is tributyl phosphate (TBP). Tricresyl phosphate (TCP) is a representative aromatic phosphate ester. A representative trimellitic acid ester is tri-2-ethylhexyl trimellitate (TOTM). Epoxidized soybean oil is a representative example of epoxidized fatty acid esters.

[0136] Durability tests were conducted using a xenon weather test for 1,920 hours (equivalent to four years of actual exposure), and the results were used to determine the superiority or inferiority of durability. Note that 487 hours is equivalent to one year of UV exposure. The conditions for the xenon weather test are as follows: UV intensity 180W / m 2 (wavelength 295-400nm). <Conditions without watering> BPT 89℃, humidity 50%, 1 hour 42 minutes. <Conditions with watering> Tank temperature 38°C, humidity 90%, 18 minutes.

[0137] The test results for 1920 hours are shown in Figure 16. Incidentally, although the experiment was conducted using vinyl chloride resin in this embodiment, the same results were obtained with vinylidene chloride resin. The results of the above experiment revealed that durability was significantly reduced when trimellitic acid ester (TOTM) and epoxidized fatty acid ester (epoxidized soybean oil) were used as plasticizers. Note that epoxidized fatty acid turned brown after 1,120 hours, making it impossible to continue the test, so it is not shown in the figure.

[0138] In contrast, it was found that when phthalate esters, aliphatic dibasic acid esters, phosphate triesters, or aromatic phosphate esters were used as plasticizers to be mixed into the vinyl chloride resin, the reflectance of the radiative cooling film CP did not decrease even after about four years, but when trimellitate esters or epoxidized fatty acid esters were used as plasticizers to be mixed into the vinyl chloride resin, the reflectance of the radiative cooling film CP decreased significantly even before about four years had passed.

[0139] The above test results show that phthalate esters, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters are excellent in durability as plasticizers for vinyl chloride resins, while trimellitate esters and epoxidized fatty acid esters are not durable.

[0140] [Other additives] The vinyl chloride resin forming the resin material layer J may contain a flame retardant, a stabilizer, a stabilizing aid, a filler, an antioxidant, an ultraviolet absorber, and a light stabilizer. <Flame retardant> Examples of flame retardants include inorganic compounds such as aluminum hydroxide, antimony trioxide, magnesium hydroxide, and zinc borate, phosphorus compounds such as cresyl diphenyl phosphate, trischloroethyl phosphate, trischloropropyl phosphate, and trisdichloropropyl phosphate, and halogen compounds such as chlorinated paraffin, etc. The amount of flame retardant to be blended per 100 parts by weight of vinyl chloride resin is about 0.1 to 20 parts by weight.

[0141] <Stabilizer> Examples of stabilizers include metal soap compounds such as lithium stearate, magnesium stearate, magnesium laurate, calcium ricinoleate, calcium stearate, barium laurate, barium ricinoleate, barium stearate, zinc octoate, zinc laurate, zinc ricinoleate, and zinc stearate, organotin compounds such as dimethyltin bis-2-ethylhexylthioglycolate, dibutyltin maleate, dibutyltin bisbutylmaleate, and dibutyltin dilaurate, and antimony mercaptide compounds. The amount of stabilizer blended per 100 parts by weight of vinyl chloride resin is about 0.1 to 20 parts by weight.

[0142] <Stabilizing agent> Examples of stabilizing aids include phosphite compounds such as triphenyl phosphite, monooctyldiphenyl phosphite, tridecyl phosphite, etc., beta-diketone compounds such as acetylacetone, benzoylacetone, etc., polyol compounds such as glycerin, sorbitol, pentaerythritol, polyethylene glycol, etc., perchlorate compounds such as barium perchlorate, sodium perchlorate, etc., hydrotalcite compounds, zeolites, etc. The amount of stabilizing aid to be blended per 100 parts by weight of vinyl chloride resin is about 0.1 to 20 parts by weight.

[0143] <Filler> Examples of fillers include calcium carbonate, silica, alumina, clay, talc, diatomaceous earth, ferrite and other metal oxides, glass, carbon, metal fibers and powders, glass spheres, graphite, aluminum hydroxide, barium sulfate, magnesium oxide, magnesium carbonate, magnesium silicate, calcium silicate, etc. The amount of filler to be blended per 100 parts by weight of vinyl chloride resin is about 1 to 100 parts by weight.

[0144] <Antioxidants> Examples of antioxidants include phenolic compounds such as 2,6-di-tert-butylphenol, tetrakis[methylene-3-(3,5-tert-butyl-4-hydroxyphenol)propionate]methane, and 2-hydroxy-4-methoxybenzophenone; sulfur compounds such as alkyl disulfides, thiodipropionic acid esters, and benzothiazole; phosphoric acid compounds such as trisnonylphenyl phosphite, diphenylisodecyl phosphite, triphenyl phosphite, and tris(2,4-di-tert-butylphenyl)phosphite; and organometallic compounds such as zinc dialkyldithiophosphate and zinc diaryldithiophosphate. The amount of antioxidant to be blended per 100 parts by weight of vinyl chloride resin is approximately 0.2 to 20 parts by weight.

[0145] <UV absorber> Examples of ultraviolet absorbers include salicylate compounds such as phenyl salicylate and p-tert-butylphenyl salicylate, benzophenone compounds such as 2-hydroxy-4-n-octoxybenzophenone and 2-hydroxy-4-n-methoxybenzophenone, benzotriazole compounds such as 5-methyl-1H-benzotriazole and 1-dioctylaminomethylbenzotriazole, as well as cyanoacrylate compounds, triazine compounds, etc. The amount of ultraviolet absorber to be blended per 100 parts by weight of vinyl chloride resin is about 0.1 to 10 parts by weight.

[0146] It is desirable to compound an ultraviolet absorber in the resin material layer J (infrared radiation layer A) to reduce the transmittance of light with wavelengths of 290 nm or more and 330 nm or less through the resin material layer J (infrared radiation layer A) to 0%. When light with wavelengths of 290 nm or more and 330 nm or less is transmitted to the light-reflecting layer B, radicals are formed in the adjacent protective layer Du around the silver, which react with the silver and cause coloration of the light-reflecting layer B. FIG. 9 shows the transmittance of vinyl chloride resin using diisononyl phthalate (DINP) as a plasticizer.

[0147] <Light stabilizer> Light stabilizers include bis(2,2,6,6-tetramethyl-4-piperidyl) sebacate, bis(1,2,2,6,6-pentamethyl-4-piperidyl) sebacate and methyl 1,2,2,6,6-pentamethyl-4-piperidyl sebacate (mixture), bis(1,2,2,6,6-pentamethyl-4-piperidyl)[[3,5-bis(1,1-dimethylethyl)-4-hydroxyphenyl]methyl]butylmalonate, decanedioic acid bis(2,2,6,6-tetramethyl-1(octyloxy)phenyl]methyl, methyl methyl methyl malonate, methyl ... (ii)-4-piperidyl) esters and reaction products of 1,1-dimethylethyl hydroperoxide with octane, 4-benzoyloxy-2,2,6,6-tetramethylpiperidine, ester mixtures of 2,2,6,6-tetramethyl-4-piperidinol and higher fatty acids, tetrakis(2,2,6,6-tetramethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate, tetrakis(1,2,2,6,6-pentamethyl-4-piperidyl)-1,2,3,4-butanetetracarboxylate Xylate, polycondensation polymer of dimethyl succinate and 4-hydroxy-2,2,6,6-tetramethyl-1-piperidineethanol, poly[{(6-(1,1,3,3-tetramethylbutyl)amino-1,3,5-triazine-2,4-diyl){(2,2,6,6-tetramethyl-4-piperidyl)imino}hexamethylene{(2,2,6,6-tetramethyl-4-piperidyl)imino}}, dibutylamine·1,3,5-triazine·N,N'-bis(2,2,6,6-tetramethyl-4-piperidyl)imino Examples of the light stabilizer include a polycondensate of N-(2,2,6,6-tetramethyl-4-piperidyl)butylamine and a hindered amine such as N,N',N'',N'''-tetrakis-(4,6-bis-(butyl-(N-methyl-2,2,6,6-tetramethylpiperidin-4-yl)amino)-triazin-2-yl)-4,7-diazadecane-1,10-diamine. The amount of the light stabilizer to be blended per 100 parts by weight of the vinyl chloride resin is about 0.1 to 10 parts by weight.

[0148] [Specific configuration of radiative cooling film] The specific configuration of the radiative cooling film CP (film body) is as shown in Fig. 5, in which a resin material layer J and a laminated part consisting of an adjacent-side protective layer Du, a light-reflecting layer B, and a distant-side protective layer Ds are bonded together by an adhesive layer N. The adhesive layer N is, for example, a urethane resin adhesive (adhesive), an acrylic urethane resin adhesive (adhesive), or a polyolefin resin adhesive (adhesive), and it is desirable that the adhesive has high transparency to sunlight.

[0149] An example of fabricating a radiative cooling film CP (film body F) is shown in Figure 6. First, a release layer G is formed on top of a film-like substrate K such as PET, and then a separation-side protective layer Ds is applied or attached on top of the release layer G. A light-reflecting layer B is formed on the separation-side protective layer Ds by vapor deposition, sputtering, ion plating, silver mirror reaction, etc., and then an adjacent-side protective layer Du is applied or attached on top of the light-reflecting layer B. That is, a release layer G, a spacing-side protective layer Ds, a light-reflecting layer B, and an adjacent-side protective layer Du are sequentially laminated on top of a substrate K to form a reflective layer-side laminate P. In addition, a resin material layer J is separately formed in the form of a film.

[0150] Then, the resin material layer J fabricated in a film form and the reflective layer side laminate P are bonded together with an adhesive layer N. Thereafter, the release layer G is removed from the separating-side protective layer Ds, and the substrate K is separated. Incidentally, the release layer G is formed of either a silicone resin or a fluororesin.

[0151] <Considerations on adhesive layers> Resin materials with good ductility include the following resin materials. Soft vinyl chloride resin Urethane resin Acrylic-urethane copolymer resin (acrylic urethane resin) Polyolefin resin Silicone resin Among these resins, urethane resin, acrylic urethane resin, and polyolefin resin are suitable for adhesives. All of them have high elongation but low tensile strength. The thickness of the adhesive layer is preferably 1 μm or more and 30 μm or less.

[0152] Incidentally, acrylic resin has a tensile strength of approximately 48 MPa to 73 MPa and an elongation at break (elongation limit) of 2% to 7%. Since it is a material with a small elongation at break (elongation limit) and is difficult to stretch, acrylic resin alone cannot be used as the adhesive layer N. In contrast, urethane resin has a tensile strength of approximately 1 MPa to 69 MPa and an elongation at break (elongation limit) of 100% to 10,000%, making it a highly stretchable material. When an acrylic urethane resin, which is a copolymer of acrylic and urethane, is used, the elongation of urethane is added to the acrylic, resulting in good stretchability. Therefore, acrylic urethane resin is desirable.

[0153] [Details of the protective layer] The adjacent-side protective layer Du and the distant-side protective layer Ds are made of any of urethane resin, acrylic urethane resin, and polyolefin-based resin, and have a thickness of 300 nm or more and 40 μm or less. Polyolefin resins include polyethylene and polypropylene.

[0154] Figure 2 shows the ultraviolet absorption rates of polyethylene (olefin-based), vinylidene chloride resin, and vinyl chloride resin. Note that Figure 2 also shows the ultraviolet absorption rate of ethylene terephthalate resin (PET) for reference, but because ethylene terephthalate resin (PET) is a material that is difficult to stretch, it cannot be used as a material to fabricate the radiative cooling film CP (film body F), nor can it be used as the adjacent-side protective layer Du or the distant-side protective layer Ds. FIG. 11 shows the light transmittance of polyethylene, which is suitable as a synthetic resin for forming the adjacent-side protective layer Du and the separating-side protective layer Ds.

[0155] The radiative cooling film CP (film body F) exerts a radiative cooling effect not only at night but also in a solar radiation environment. Therefore, in order for the light-reflecting layer B to maintain its light-reflecting function, it is necessary to protect the light-reflecting layer B with the adjacent protective layer Du so that the silver of the light-reflecting layer B does not discolor in a solar radiation environment.

[0156] When the adjacent-side protective layer Du is formed from a polyolefin-based resin with a thickness of 300 nm or more and 40 μm or less, the polyolefin-based resin is a synthetic resin with an ultraviolet light absorption rate of 10% or less over the entire ultraviolet wavelength range of 0.3 μm to 0.4 μm, so the adjacent-side protective layer Du is less likely to deteriorate due to absorption of ultraviolet rays.

[0157] Furthermore, since the thickness of the polyolefin resin forming the adjacent side protective layer Du is 300 nm or more, it effectively performs blocking functions such as blocking radicals generated in the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer B, and blocking moisture that penetrates the resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer B, thereby suppressing discoloration of the silver or silver alloy forming the light-reflecting layer B.

[0158] Incidentally, the adjacent-side protective layer Du, which is made of a polyolefin resin, deteriorates by absorbing ultraviolet rays and forming radicals on the surface side away from the light-reflecting layer B. However, since the thickness is 300 nm or more, the formed radicals do not reach the light-reflecting layer. Furthermore, even if the layer deteriorates by forming radicals, the rate of deterioration is slow due to the low absorption of ultraviolet rays, so the above-mentioned blocking function can be maintained for a long period of time.

[0159] When the adjacent-side protective layer Du and the spacing-side protective layer Ds are formed from a polyolefin resin, a urethane resin, or an acrylic urethane resin, the reason for setting an upper limit on the thickness is to prevent the adjacent-side protective layer Du and the spacing-side protective layer Ds from exhibiting heat insulating properties that do not contribute to radiative cooling. In other words, the thicker the adjacent-side protective layer Du and the spacing-side protective layer Ds are, the more heat insulating properties they exhibit that do not contribute to radiative cooling. Therefore, an upper limit on the thickness is set to prevent heat insulating properties that do not contribute to radiative cooling while still providing the function of protecting the light reflecting layer B.

[0160] Incidentally, as shown in Figure 5, when an adhesive layer N is located between the resin material layer J and the adjacent-side protective layer Du, radicals will also be generated from the adhesive layer N. However, since the thickness of the polyolefin resin forming the adjacent-side protective layer Du is 300 nm or more, the radicals generated in the adhesive layer N can be prevented from reaching the light-reflecting layer B for a long period of time.

[0161] As mentioned above, if the adjacent-side protective layer Du becomes thicker, there is no disadvantage in terms of preventing coloration of the silver (silver alloy) of the light-reflecting layer B, but it does cause problems in terms of radiative cooling. In other words, if the thickness is increased, the heat insulating properties of the radiative cooling material will increase. For example, a resin whose main component is polyethylene, which is an excellent synthetic resin for forming the adjacent-side protective layer Du, has a low emissivity at the atmospheric window, as shown in Figure 15, so even if it is formed thick, it does not contribute to radiative cooling. In fact, increasing the thickness actually increases the thermal insulation properties of the radiative cooling material. Next, as the thickness increases, absorption in the near-infrared region due to main chain vibrations increases, increasing the effect of increasing solar absorption. Due to these factors, a thick adjacent-side protective layer Du is disadvantageous for radiative cooling. From this perspective, the thickness of the adjacent-side protective layer Du made of a polyolefin resin is preferably 5 μm or less, and more preferably 1 μm or less.

[0162] [Considerations on the protective layer] In order to examine the difference in the way silver is colored by the adjacent-side protective layer Du, a sample was prepared in which the adjacent-side protective layer Du was exposed and did not have the resin material layer J as the infrared radiation layer A, as shown in Figure 12, and the coloring of silver after irradiation with simulated sunlight was examined. Specifically, samples were prepared by applying two types of adjacent-side protective layer Du, a common acrylic resin that absorbs ultraviolet light (for example, methyl methacrylate resin mixed with a benzotriazole-based ultraviolet absorber) and polyethylene, using a bar coater, onto a film layer U (corresponding to the substrate) that includes silver as a light-reflecting layer B, and their function as adjacent-side protective layer Du was examined. The thicknesses of the applied adjacent-side protective layers Du were 10 μm and 1 μm, respectively. The film layer U (corresponding to the substrate) is formed into a film shape using PET (ethylene terephthalate resin) or the like.

[0163] As shown in Figure 14, if the adjacent-side protective layer Du is made of an acrylic resin that absorbs UV rays well, the adjacent-side protective layer Du is decomposed by UV rays to form radicals, and the silver quickly turns yellow and ceases to function as a radiative cooling film CP (it absorbs sunlight and, like general materials, its temperature rises when exposed to sunlight). The 600h line in the figure indicates the results of a xenon weather test (ultraviolet light energy 60W / m) under the conditions of JIS standard 5600-7-7. 2 The reflectance spectrum after 600 hours of xenon weathering is shown in Fig. 1. The 0h line is the reflectance spectrum before the xenon weathering test.

[0164] As shown in Figure 13, when the adjacent-side protective layer Du is made of polyethylene, which has low ultraviolet light absorption, no decrease in reflectance is observed from the near-infrared region to the visible region. In other words, resins whose main component is polyethylene (olefin-based resins) hardly absorb the ultraviolet light contained in sunlight that reaches the ground, and therefore do not easily form radicals even when exposed to sunlight, so that the silver serving as the light-reflecting layer B does not become discolored even when exposed to sunlight. The 600h line in the figure indicates the results of a xenon weather test (ultraviolet light energy 60W / m) under the conditions of JIS standard 5600-7-7. 2The reflectance spectrum after 600 hours of xenon weathering is shown in Fig. 1. The 0h line is the reflectance spectrum before the xenon weathering test.

[0165] The reason for the undulations in the reflectance spectrum in this wavelength range is the Fabry-Perot resonance of the polyethylene layer. This is due to changes in the thickness of the polyethylene layer caused by heat during the xenon weather test, and it can be seen that the resonance position changes slightly between the 0h line and the 600h line. However, no significant decrease in reflectance in the ultraviolet-visible range due to the yellowing of the silver is observed.

[0166] Furthermore, from the viewpoint of ultraviolet absorption, fluororesin-based materials can also be used to form the adjacent-side protective layer Du, but when actually formed as the adjacent-side protective layer Du, they become discolored and deteriorate during the formation stage, and therefore cannot be used as materials to form the adjacent-side protective layer Du. Furthermore, although silicone resin can also be used as a material for forming the adjacent-side protective layer Du from the viewpoint of ultraviolet absorption, it has extremely poor adhesion to silver (silver alloy) and cannot be used as a material for forming the adjacent-side protective layer Du.

[0167] [Considerations on plasticizers] The plasticizers mixed into vinyl chloride resins will be considered below. (Deterioration of vinyl chloride resin) The deterioration of vinyl chloride resin (film) due to sunlight is largely due to the deterioration of plasticizers by ultraviolet rays. PVC resins (mixed with plasticizers) that are normally used outdoors for long periods are protected from the ultraviolet rays contained in sunlight by coloring and additives. For example, they are often colored black or other colors to make them less susceptible to the effects of ultraviolet rays. On the other hand, in the case of radiative cooling film CP, it is necessary to minimize sunlight absorption in order to achieve radiative cooling performance. For this reason, it is not possible to add enough additives, dyes, or pigments to protect the plasticizer.

[0168] As shown in Fig. 5, the radiative cooling film CP (film body F) has an adhesive layer N and an adjacent-side protective layer Du under a resin material layer J made of vinyl chloride resin, and a light-reflecting layer B containing silver under that. The light-reflecting layer B makes the resin material layer J more susceptible to the effects of sunlight. In other words, sunlight that has once entered the radiative cooling film CP (film body F) is reflected by the light-reflecting layer B and then passes through the resin material layer J twice. This means that the influence of sunlight on degradation is about twice as strong as usual.

[0169] Furthermore, when comparing the resin material layer J formed on the light-reflecting layer B containing silver with the resin material layer J formed on aluminum, iron, or ceramics, which have low reflectivity, the radiative cooling film CP having the resin material layer J formed on the light-reflecting layer B containing silver is more affected by sunlight. These findings suggest that the vinyl chloride resin of the radiative cooling film CP (film body F), which has a resin material layer J on a light-reflecting layer B containing silver, is more sensitive to ultraviolet rays contained in sunlight than vinyl chloride resins for general use.

[0170] Degradation of ester-based plasticizers due to ultraviolet light occurs mainly due to the plasticizer absorbing ultraviolet energy. UV absorption occurs mainly due to electron transitions that exceed the bond energy of the ester bond in the plasticizer. The activation energy provided by UV light and water molecules accelerates the hydrolysis of the plasticizer mixed into the vinyl chloride resin. When the plasticizer bonds break, the broken bonds attack the surrounding vinyl chloride resin, causing dechlorination and discoloration, which also reduces the mechanical strength. When the vinyl chloride resin becomes discolored, the radiative cooling film CP (film body F) absorbs sunlight and is no longer able to cool during the day.

[0171] Therefore, as shown in the experimental results in Fig. 16, plasticizers (trimellitic acid esters, epoxidized fatty acid esters) used in outdoor applications exposed to direct sunlight cannot be used in the radiative cooling film CP, and phthalate esters, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters can be used as plasticizers for the radiative cooling film CP (film body F).

[0172] (Protective properties of resin material layer with UV absorber) The vinyl chloride resin forming the resin material layer J of the radiative cooling film CP (film body F) used in the experiment was mixed with an ultraviolet absorber, and the reflectance of the radiative cooling film CP (film body F) at the time of production was adjusted to be 10% or less in the wavelength range of 295 nm or more and 350 nm or less (see Figure 16). This ultraviolet absorber is present to protect the adhesive layer N, adjacent side protective layer Du, and silver-containing light-reflecting layer B below the resin material layer J, and its effect in protecting the resin material layer J from ultraviolet rays is limited.

[0173] The absorbance (A) of the ultraviolet absorber can be expressed by the following formula (2). A=1-exp(-αt) (2) where α is the absorption coefficient and t is the film thickness. From this equation, it can be seen that as light travels through the resin material layer J (vinyl chloride resin), it is gradually absorbed by the resin material layer J. In other words, the ultraviolet protection effect of the ultraviolet absorber cannot be expected, particularly on the sunlight incident side of the resin material layer J (vinyl chloride resin). In other words, the experimental results showed that when trimellitic acid was used as the plasticizer, the radiative cooling film CP deteriorated as it was gouged out from the sunlight-irradiated surface (radiation surface H).

[0174] (Regarding suitable and unsuitable plasticizers) Suitable plasticizers to be mixed into the vinyl chloride resin are, as mentioned above, phthalates, aliphatic dibasic acid esters, phosphate triesters, and aromatic phosphate esters. The aliphatic dibasic acid ester is preferably an ester bond between an aliphatic dibasic acid and two molecules of a saturated aliphatic alcohol, and the phthalic acid ester is preferably an ester bond between phthalic acid and two molecules of a saturated aliphatic alcohol. In addition, for each of the phthalic acid ester, aliphatic dibasic acid ester, and phosphate triester, it is desirable that the hydrocarbon group of the ester is an alkyl group.

[0175] As mentioned above, unsuitable plasticizers are trimellitic esters and epoxidized fatty acid esters. Furthermore, plasticizers in which the hydrocarbon group of the phthalate ester, aliphatic dibasic acid ester, or phosphate triester is an unsaturated hydrocarbon group are also unsuitable. In other words, it is desirable that the hydrocarbon group of the phthalate ester, aliphatic dibasic acid ester, or phosphate triester is a saturated hydrocarbon group. In other words, if the hydrocarbon group is unsaturated, the unsaturated bond causes coloration, absorbs sunlight well, and reduces the radiative cooling performance. In addition, the unsaturated bond absorbs sunlight and cleaves, promoting reactions with the surrounding oligomers and vinyl chloride, which causes embrittlement and coloration of the resin material layer J of the radiative cooling film CP. In short, the suitability of plasticizers depends on how easily they absorb ultraviolet light.

[0176] (About phthalates) First, we will compare phthalates, which are aromatic carboxylic acid esters, with trimellitates. An example of a phthalate ester is DOP (di-2-ethylhexyl phthalate), and an example of a trimellitate ester is TOTM (tri-2-ethylhexyl trimellitate). Decomposition outdoors under ultraviolet light occurs through hydrolysis of the ester bond. UV light provides the activation energy for this reaction. The bond energy of the ester bond in trimellitic esters is weaker than that of phthalic acid. This difference is reflected in the difference in UV absorption.

[0177] The following equation (3) is the absorption wavelength (λA) and bond energy (E). λ A =1240 / E---(3) This equation shows that as the bond energy (E) decreases, the UV absorption wavelength that activates the bond electron transfer shifts to longer wavelengths. Figure 17 shows an example. In Figure 17, DEHP and DINCH are phthalate esters, and TOTM is trimellitate ester. Note that DEHP is the same as DOP.

[0178] While terrestrial sunlight exists in wavelengths longer than 295 nm, TOTM effectively absorbs ultraviolet light in wavelengths longer than 295 nm. This absorption comes from the ester bond, and provides the activation energy for hydrolysis, in which ultraviolet light reacts with surrounding water. Incidentally, trimellitic acid ester is a plasticizer that is also used in soft PVC electric wires exposed to direct sunlight, but it cannot be used for the PVC that forms the resin material layer J of the radiative cooling film CP, even though it is for the same outdoor use. In general outdoor uses, the PVC layer is often sufficiently colored black or other colors, making it less susceptible to the effects of UV rays, and therefore less susceptible to deterioration due to UV rays.

[0179] On the other hand, in the case of radiative cooling film CP, it is necessary to minimize the absorption of sunlight in order to achieve radiative cooling performance, and therefore additives, dyes, and pigments to protect the plasticizer cannot be added in sufficient quantities. Therefore, plasticizers that are used in other outdoor applications where the film is exposed to direct sunlight cannot be used in this application. Trimellitic acid esters include tri-2-ethylhexyl trimellitate (TO™), triisononyl trimellitate (TINT™), triisodecyl trimellitate (TID™), and the like, but all of them are unsuitable.

[0180] FIG. 18 shows the absorbance of other phthalate esters, DOP (di-2-ethylhexyl phthalate) and DBP (dibutyl phthalate), and shows that they have almost no absorption in wavelengths longer than 295 nm.

[0181] When the hydrocarbon group is an alkyl group, the strength of the ester bond is highly dependent on the type of carboxylic acid, and UV absorption shows similar trends for the same type of carboxylic acid. When the hydrocarbon group is an alkyl group, the light absorption at the longest wavelengths in the UV range below 400 nm is due to the bond energy of the ester bond. Phthalate esters, whose hydrocarbon group is an alkyl group, do not absorb light in the ultraviolet region longer than 295 nm, which is present in the terrestrial sunlight spectrum, and are not hydrolyzed by the ultraviolet energy of sunlight.

[0182] On the other hand, in trimellitic esters, whose hydrocarbon group is an alkyl group, the ester bond absorbs the ultraviolet energy of sunlight, and this energy accelerates hydrolysis. The acid and alcohol produced by hydrolysis absorb ultraviolet light and react with the surrounding oligomers and vinyl chloride, which causes embrittlement and coloration of the resin material layer J of the radiative cooling film CP. In other words, aromatic carboxylic acid esters used as plasticizers include phthalates and trimellitates, and while phthalates can be used as radiative cooling materials, trimellitates cannot.

[0183] (Aliphatic dibasic acid esters) When the hydrocarbon group is an alkyl group, the strength of the ester bond is highly dependent on the type of carboxylic acid, and as explained in the sections on phthalic acid and trimellitic acid, if the type of carboxylic acid is the same, the ultraviolet absorption will show similar trends. Consider the case where the aliphatic dibasic acid of the aliphatic dibasic acid ester is a saturated dicarboxylic acid such as adipic acid, azelaic acid, sebacic acid, or succinic acid, and the ester is an ester bond between such an acid and saturated glucose. This also includes copolymers of saturated dicarboxylic acids and saturated glucose. In this case, the only functional group that has optical characteristics in the ultraviolet region is the ester bond, and theoretically, the absorption spectrum in the ultraviolet region (200 nm or more and 400 nm or less) is the same for all aliphatic dibasic acid esters.

[0184] Let us consider DOA (di-2-ethylhexyl adipate), a typical example of an aliphatic dibasic acid ester. Figure 19 shows the absorbance of DOA in the ultraviolet region, and it can be seen that its solar light absorption rate is even lower than that of the aforementioned DOP (di-2-ethylhexyl phthalate), which has almost no absorption in wavelengths longer than 295 nm. In Figure 16, both the phthalate ester and the aliphatic dibasic acid ester endured 2000 hours in a xenon weather test, but optically, DOA had higher durability.

[0185] (About phosphate esters) Phosphate ester plasticizers include phosphate triesters and aromatic phosphate triesters. Phosphate esters have a large bond energy and do not hydrolyze under ultraviolet light with wavelengths longer than 295 nm. Therefore, they are excellent plasticizers for radiative cooling films (CP). Furthermore, when made into phosphate esters, they are flame retardant.

[0186] As mentioned above, the phosphate triester includes trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), and tris(2-ethylhexyl) phosphate (TOP). FIG. 20 shows the absorbance of tributyl phosphate (TBP), which shows that it hardly absorbs ultraviolet light with wavelengths longer than 295 nm.

[0187] As mentioned above, the aromatic phosphate esters include triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), tresyl diphenyl phosphate (CDP), and 2-ethylhexyl diphenyl phosphate. Although not shown in the figure, aromatic phosphate esters hardly absorb ultraviolet light with wavelengths longer than 295 nm.

[0188] (Epoxidized fatty acid esters) Epoxidized fatty acid esters, like the above-mentioned TOTM (trimellitic acid ester), effectively absorb ultraviolet light with wavelengths longer than 295 nm. In other words, the epoxy groups in epoxidized fatty acid esters absorb and decompose ultraviolet light with wavelengths longer than 295 nm. They are also decomposed by microorganisms. Therefore, they cannot be used outdoors. Epoxidized fatty acid esters include epoxidized soybean oil and epoxidized linseed oil, but none of them can be used as plasticizers to be mixed into the vinyl chloride resin of the radiative cooling film CP.

[0189] [Another configuration of the infrared radiation layer] As shown in Fig. 22, a light scattering structure may be provided by mixing inorganic filler V into a resin material layer J (vinyl chloride resin mixed with a plasticizer) constituting the infrared radiation layer A. Alternatively, as shown in Fig. 21, both 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 structure. With this configuration, glare from the radiation surface H can be suppressed when the radiation surface H is viewed.

[0190] In other words, the above-mentioned resin material layer J is flat on both the front and back sides and is configured so that no filler V is mixed in. In such a configuration, the radiation surface H is mirror-like, so when the radiation surface H is viewed, glare is perceived, but this glare can be suppressed by providing a light-scattering configuration. Furthermore, when filler V is mixed into the resin material layer J, if an adjacent side protective layer Du and a light-reflecting layer B are present, the light reflectivity is improved compared to when only the resin material layer J mixed with filler V is present or when only the light-reflecting layer B is present.

[0191] The inorganic material that forms Filler V is silicon dioxide (SiO2). 、 Titanium oxide (TiO2), aluminum oxide (Al2O3), magnesium oxide (MgO), etc. If filler V is mixed into the resin material layer J, both the front and back surfaces of the resin material layer J will have an uneven shape. In addition, the front and back surfaces of the resin material layer J can be made uneven by embossing or scratching the surface.

[0192] If the rear surface of the resin material layer J is uneven, it is desirable to position the adhesive layer N between the resin material layer J and the adjacent-side protective layer Du, similar to the configuration described in FIG. In other words, even if the back surface of the resin material layer J is uneven, the adhesive layer N (bonding layer) is located between the resin material layer J and the adjacent side protective layer Du, so the resin material layer J and the adjacent side protective layer Du can be properly bonded together.

[0193] In addition, when the back surface of the resin material layer J is uneven, the resin material layer J and the adjacent-side protective layer Du may be directly bonded by, for example, plasma bonding. Note that plasma bonding is a form of bonding in which radicals are formed on the bonding surfaces of the resin material layer J and the adjacent-side protective layer Du by emitting plasma.

[0194] Incidentally, if filler V is mixed into adjacent-side protective layer Du, the back surface of adjacent-side protective layer Du that contacts light-reflecting layer B will become uneven, causing the surface of light-reflecting layer B to deform unevenly, and therefore it is necessary to avoid mixing filler V into adjacent-side protective layer Du. In other words, if the surface of light-reflecting layer B deforms unevenly, it will not be able to reflect light properly, and as a result, radiative cooling will not be able to be performed properly.

[0195] Figure 23 shows an example of the tensile strength (N / 2.5cm) and elongation at break (%) of a resin material layer J (vinyl chloride resin) mixed with filler V (titanium oxide: TiO2) and a plasticizer (PE-based). The PE-based plasticizer is a polyester-based material (adipic acid polyester). In addition, Figure 23 illustrates the tensile strength (N / 2.5 cm) and elongation at break (%) of a resin material layer J (vinyl chloride resin) mixed with a plasticizer (PE-based) but not with filler V, as well as the tensile strength (N / 2.5 cm) and elongation at break (%) of a resin material layer J (vinyl chloride resin) mixed with a plasticizer (DOP: di-2-ethylhexyl phthalate) but not with filler V.

[0196] [Another embodiment] Other embodiments will be listed below. (1) In the above embodiment, an object (e.g., a membrane material) that is in close contact with the back surface of the radiative cooling film CP (film body F) is used as an example of the object to be cooled E. However, various types of objects to be cooled, such as a space to be cooled, can be used as the object to be cooled E.

[0197] (2) In the above embodiment, the radiation surface H of the resin material layer J is exposed as is. However, a hard coat may be provided to cover the radiation surface H. The hard coat may be any of UV-curable acrylic, thermosetting acrylic, UV-curable silicone, thermosetting silicone, organic-inorganic hybrid, or vinyl chloride. An organic antistatic agent may also be used as an additive. Among UV-curable acrylics, urethane acrylate is particularly good.

[0198] The hard coat can be formed by a method such as gravure coating, bar coating, knife coating, roll coating, blade coating, or die coating. The thickness of the hard coat (coating film) is 1 to 50 μm, and preferably 2 to 20 μm.

[0199] (3) As a method for producing the film body F, instead of the method described in the above embodiment, other formation methods may be used, such as forming an adhesive layer N on the resin material layer J, forming an adjacent protective layer Du on the adhesive layer N, directly depositing a light-reflecting layer B on the adjacent protective layer Du, and forming a separating protective layer Ds on the light-reflecting layer B.

[0200] The configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradiction arises. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Explanation of symbols]

[0201] A infrared radiation layer B Light reflective layer Ds Separation side protective layer Du adjacent side protective layer F Film body G Release layer H radiation surface J Resin material layer N Adhesive layer P Reflective side laminate

Claims

1. the film body includes an infrared radiation layer that emits infrared light from a radiation surface, a light reflection layer made of silver or a silver alloy and located on the side of the infrared radiation layer opposite to the side on which the radiation surface is present, an adjacent-side protective layer that is located on the side of the light reflection layer that is adjacent to the infrared radiation layer, and a remote-side protective layer that is located on the side of the light reflection layer that is remote from the infrared radiation layer, The radiative cooling film is a resin material layer whose thickness is adjusted to emit thermal radiation energy greater than absorbed solar light energy in a wavelength band of 8 μm to 14 μm, the resin material forming the adjacent-side protective layer and the distant-side protective layer is any one of a urethane resin, an acrylic urethane resin, and a polyolefin resin; The film body has a tensile strength of 140 N / 2.5 cm or less at room temperature and an elongation at break of 30% or more, The radiative cooling film, wherein the thickness of the light reflecting layer is 70 nm or more and 300 nm or less.

2. The film thickness of the resin material layer is The thickness is adjusted to have light absorption characteristics in which the wavelength average of the light absorptance in the wavelength range of 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorptance in the wavelength range of 0.5 μm to 0.8 μm is 4% or less, the wavelength average of the light absorptance in the wavelength range of 0.8 μm to 1.5 μm is within 1%, and the wavelength average of the light absorptance in the wavelength range of 1.5 μm to 2.5 μm is 40% or less, and thermal radiation characteristics in which the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is 40% or more, 2. The radiative cooling film according to claim 1, wherein the resin material layer has a tensile strength of 139 N / 2.5 cm or less, an elongation at break of 50% or more, and the tensile strength decreases with increasing temperature.

3. A radiative cooling film as described in claim 1 or 2, wherein the resin material forming the resin material layer is a vinyl chloride resin mixed with a plasticizer, and the thickness of the resin material layer is 14 μm or more and 330 μm or less.

4. A radiative cooling film as described in claim 3, wherein the thickness of the resin material layer is 50 μm or more and 330 μm or less.

5. A radiative cooling film as described in claim 3 or 4, wherein the plasticizer comprises one or more compounds selected from the group consisting of phthalate esters, aliphatic dibasic acid esters, and phosphate esters.

6. A radiative cooling film described in any one of claims 3 to 5, wherein the plasticizer is mixed in an amount ranging from 7 parts by weight to 50 parts by weight per 100 parts by weight of the vinyl chloride resin.

7. A radiative cooling film as described in Claim 6, wherein the plasticizer is mixed in an amount ranging from 15 parts by weight to 50 parts by weight per 100 parts by weight of the vinyl chloride resin.

8. A radiative cooling film described in any one of claims 1 to 7, wherein the thickness of the adjacent side protective layer and the distant side protective layer is 300 nm or more and 40 μm or less.

9. The resin material layer and the adjacent-side protective layer are bonded together by an adhesive layer, The radiative cooling film according to any one of claims 1 to 8, wherein the adhesive layer is formed of any one of a urethane resin-based adhesive, an acrylic urethane resin-based adhesive, and a polyolefin resin-based adhesive.

10. A method of using the radiative cooling film according to any one of claims 1 to 9, comprising: A method for using a radiative cooling film, wherein the film body is used in a state where its elongation is 40% or less.

11. A method for producing the radiative cooling film of claim 9, comprising: a release layer, the spacing-side protective layer, the light-reflecting layer, and the adjacent-side protective layer are sequentially laminated on an upper portion of a substrate to form a reflective layer-side laminate; The resin material layer is separately formed, a method for producing a radiative cooling film, wherein the resin material layer and the reflection layer side laminate are bonded together by the adhesive layer.

12. A method for producing a radiative cooling film as described in claim 11, wherein the resin material layer and the reflective layer side laminate are bonded together with the adhesive layer, and then the release layer is separated from the separation side protective layer.

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