Composite cooling material

Abstract

To provide a composite cooling material capable of improving usability.　The present invention comprises: a magnetic material layer E that includes a magnetic material; and a cooling layer CP that is provided on the outer surface of the magnetic material layer E. The present invention has a first optical characteristic such that solar reflectance is 80% or more.

Description

Composite Cooling Material

[0001] The present disclosure relates to a composite cooling material that has the ability to cool the back side of the material.

[0002] Radiative cooling is known as a function for cooling the reverse side of a material. Radiative cooling is a phenomenon in which a material's temperature drops when it radiates electromagnetic waves such as infrared rays into its surroundings. By utilizing this phenomenon, it is possible to create a composite cooling material (composite cooling device) that cools an object without consuming energy such as electricity.

[0003] A conventional example of a composite cooling material (composite cooling device) is one that is configured by stacking an infrared radiation layer that emits infrared light from a radiation surface and a light reflecting layer that is positioned on the side of the infrared radiation layer opposite to the side where the radiation surface is present (see, for example, Patent Document 1).

[0004] In other words, the composite cooling material (composite cooling device) has an infrared radiation layer that emits large amounts of thermal radiation energy in the wavelength band of 8 μm to 14 μm, and the light reflecting layer reflects light (ultraviolet light, visible light, infrared light) that has passed through the infrared radiation layer and radiates it from the radiation surface, thereby preventing the object to be cooled from being heated and allowing it to cool even in a daytime solar environment.

[0005] 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, and infrared light) that has passed through the infrared radiation layer.

[0006] Special table 2018-526599 publication

[0007] For example, the composite cooling material may be used to attach (mount) the composite cooling material to the outer surface of a metal (e.g., iron, iron alloy, steel plate, etc.) plate, such as the outer surface of an automobile or container, with an adhesive or pressure-sensitive adhesive. In such cases, the layer of the composite cooling material located on the rearmost side, such as the separation-side protective layer, is used for connection to the object to be attached. In other words, the separation-side protective layer is attached to the outer surface of the metal plate with an adhesive or pressure-sensitive adhesive.

[0008] However, when the separating-side protective layer is made of acrylic resin, it becomes impossible to properly attach the separating-side protective layer to the metal plate with adhesive, and conventional composite cooling materials can be difficult to use, so improvements are desired.

[0009] The present disclosure has been made in consideration of the above-mentioned problems, and its purpose is to provide a composite cooling material that can improve usability.

[0010] A characteristic configuration of a composite cooling material according to one embodiment of the present disclosure is that it comprises a magnetic material layer containing a magnetic material, and a cooling layer provided on the outer surface of the magnetic material layer, and the cooling layer has a first optical property of a solar reflectance of 80% or more.

[0011] According to this configuration, the cooling layer has the first optical property of a solar reflectance of 80% or more, and therefore can satisfactorily exhibit a predetermined solar reflecting function.

[0012] Furthermore, according to the composite cooling material of this configuration, a magnetic material layer that can be attached to a target metal plate by magnetic force is provided on the back side opposite the outer surface of the cooling layer, so the composite cooling material can be attached to the target. That is, by appropriately selecting a metal plate that can be attached by magnetic force generated by the magnetic material layer as the target, the composite cooling material can be successfully attached to the plate. In short, the characteristic configuration of the composite cooling material can improve usability.

[0013] Further characteristic configurations of the composite cooling material are that the cooling layer is configured to include an infrared radiation layer that emits infrared light from its radiation surface, and a light reflecting layer that is located on the infrared radiation layer opposite to the side where the radiation surface is present, and has a second optical characteristic of an average emissivity of 80% or more, which is the wavelength average of the emissivity of infrared light of 8 μm or more and 14 μm or less, the infrared radiation layer is a resin material layer made of vinyl chloride resin or vinylidene chloride resin that has a thickness 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, the light reflecting layer comprises silver or a silver alloy, and the cooling layer and the magnetic material layer are connected by a connecting layer that includes one or more of vinyl chloride resin, vinylidene chloride resin, polyolefin resin, polyester resin, acrylic resin, urethane resin, silicone resin, and rubber resin.

[0014] Sunlight incident from the radiation layer of the infrared radiation layer in the cooling layer passes through the resin material layer, is reflected by the light-reflecting layer located on the opposite side of the radiation surface of the resin material layer, and is then released from the radiation surface to the outside of the system. In this specification, when simply referring to light, the concept of light includes ultraviolet light (ultraviolet light), visible light, and infrared light. These are described in terms of the wavelength of light as electromagnetic waves, and 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 to the cooling layer (heat input) is converted into infrared light by the resin material layer acting as an infrared radiation layer and is then released from the radiation surface to the outside of the system. In this way, the cooling layer reflects sunlight irradiating the cooling layer, and can also radiate heat transferred to the cooling layer (for example, heat transferred from the atmosphere or heat transferred from the film material cooled by the cooling layer) to the outside of the system as infrared light.

[0016] In addition, the cooling layer has a second optical characteristic of an average emissivity of 80% or more, which is the wavelength average of the emissivity of infrared light from 8 μm to 14 μm, and the resin material layer is adjusted to a thickness that emits thermal radiation energy in the wavelength range of 8 μm to 14 μm that is greater than the absorbed solar light energy.Therefore, the cooling function can be exerted even in a daytime solar radiation environment while the light-reflecting layer comprising silver or a silver alloy appropriately reflects sunlight.

[0017] Therefore, even in a daytime solar radiation environment, the cooling layer can cool the region inside the cooling layer (the side where the magnetic material layer exists) by radiative cooling.

[0018] Thin-film vinyl chloride resin or vinylidene chloride resin becomes flexible by adding a plasticizer, and thus can flexibly change shape to accommodate contact with other objects, avoiding damage and maintaining a beautiful appearance for a long period of time. Thin-film fluororesin, on the other hand, is hard and therefore cannot flexibly change shape when contacted with other objects, making it prone to scratches and difficult to maintain a beautiful appearance. Furthermore, adding a plasticizer to vinyl chloride resin allows it to deform when heated to 80°C or higher, eliminating and smoothing the surface, even if scratched, thereby self-repairing the damage. This characteristic is not found in fluororesins or silicone rubber. This property of soft vinyl chloride resin allows it to maintain a beautiful appearance for a long period of time, which leads to the maintenance of radiative cooling performance over a long period of time. Furthermore, vinyl chloride resin is flame-retardant and not easily biodegradable, making it suitable as a resin material for forming the resin material layer of a radiative cooling device used outdoors. 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.

[0019] Furthermore, in addition to the flexibility of the thin film vinyl chloride resin, the vinyl chloride resin is softened by mixing a plasticizer into it, which makes the resin material layer even more flexible, and as a result, the radiative cooling device is flexible.

[0020] Furthermore, as in this configuration, by connecting the cooling layer and the magnetic material layer with a connecting layer containing one or more of vinyl chloride resin, vinylidene chloride resin, polyolefin resin, acrylic resin, urethane resin, silicone resin, and rubber resin, the cooling layer and the magnetic material layer can be well connected.

[0021] A further characteristic feature of the composite cooling material is that the connection layer contains at least one of vinyl chloride resin and polyolefin resin.

[0022] According to this configuration, by forming the connection layer that connects the cooling layer and the magnetic material layer from at least one of vinyl chloride resin and polyolefin resin, the cooling layer and the magnetic material layer can be connected even better.

[0023] A further characteristic feature of the composite cooling material is that the magnetic material layer contains at least ferrite and a binder resin, and has a thickness of 0.2 mm or more and 2.0 mm or less.

[0024] As in this configuration, the magnetic material layer can be composed of a material containing at least ferrite and a binder resin. In particular, by making the thickness of the magnetic material layer 0.2 mm or more, the magnetic force acting as an attachment force to the metal plate to be attached can be effectively exerted, thereby improving long-term adhesion stability. Furthermore, by making the thickness 2.0 mm or less, even if a heat source is present on the back side of the composite cooling material, heat dissipation from the back side to the outer surface can be maintained at a certain level or higher.

[0025] A further characteristic feature of the composite cooling material is that the cooling layer includes an infrared radiation layer that emits infrared light from its radiation surface, and the infrared radiation layer includes a plurality of granular light-reflecting portions that reflect light.

[0026] According to this configuration, the infrared radiation layer of the cooling layer is provided with a plurality of granular light-reflecting portions that reflect light. For example, by providing a sufficient number of such granular light-reflecting portions in the infrared radiation layer, the infrared radiation layer itself as a radiation layer can also function as a light-reflecting layer that reflects light. In some cases, this eliminates the need to separately provide a light-reflecting layer made of a metal such as silver or a silver alloy, thereby enabling cost reductions.

[0027] Furthermore, even if the composite cooling layer is configured to include an infrared radiation layer that emits infrared light as well as a light reflection layer that reflects light, by providing the infrared radiation layer with multiple granular light reflection portions, light is reflected (solar radiation is reflected) not only by the light reflection layer but also by the light reflection portions of the infrared radiation layer, so that better cooling function can be achieved when sunlight irradiation is strong.

[0028] Furthermore, with this configuration, even if the silver or silver alloy in the light-reflecting layer breaks and cracks when attaching the composite cooling material to an object, the light can be reflected by the light-reflecting portion of the infrared radiation layer, thereby preventing a decrease in cooling performance.

[0029] In the composite cooling materials described above, it is preferable that the particle size of the light reflecting portion is 1 nm or more and 300 μm or less.

[0030] Furthermore, in the composite cooling materials described above, it is preferable that the light reflecting portion is porous.

[0031] Furthermore, in the composite cooling material described above, it is preferable that the light reflecting portion includes at least one of an inorganic filler and an organic filler, the inorganic filler includes at least one of glass microbeads, ceramic microbeads, silicon oxide particles, silicon carbide particles, silicon nitride particles, barium sulfate particles, and calcium carbonate particles, and the organic filler includes at least one of polymers having any one of the functional groups C—O, C—Cl, C—F, C—N, C—Si, and Si—O.

[0032] In the composite cooling material described above, the cooling layer preferably contains an inorganic filler, and the inorganic filler preferably contains at least one of glass microbeads, ceramic microbeads, silicon oxide particles, silicon carbide particles, silicon nitride particles, barium sulfate particles, and calcium carbonate particles.

[0033] A further characteristic feature of the composite cooling material is that the film thickness of the resin material layer is adjusted to a thickness that provides light absorption characteristics such that the wavelength average light absorptance at wavelengths of 0.4 μm to 0.5 μm is 13% or less, the wavelength average light absorptance at wavelengths of 0.5 μm to 0.8 μm is 4% or less, the wavelength average light absorptance at wavelengths of 0.8 μm to 1.5 μm is within 1%, and the wavelength average light absorptance at wavelengths of 1.5 μm to 2.5 μm is 40% or less.

[0034] The wavelength average of the light absorptance at wavelengths 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 at wavelengths of 0.5 μm to 0.8 μm, the wavelength average of the light absorptance at wavelengths of 0.8 μm to 1.5 μm, and the wavelength average of the light absorptance at wavelengths 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.

[0035] That is, the light absorptivity and emissivity (light emissivity) of the resin material layer change depending on the thickness, so 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 20 μm).

[0036] Specifically, in terms of the light absorptance (light absorption characteristics) of sunlight in the resin material layer, the wavelength-average light absorptance for wavelengths from 0.4 μm to 0.5 μm must be 13% or less, the wavelength-average light absorptance for wavelengths from 0.5 μm to 0.8 μm must be 4% or less, the wavelength-average light absorptance for wavelengths from 0.8 μm to 1.5 μm must be within 1%, and the wavelength-average light absorptance for wavelengths from 1.5 μm to 2.5 μm must be 40% or less. Regarding the light absorptance for wavelengths from 2.5 μm to 4 μm, it is sufficient that the wavelength-average light absorptance is 100% or less. With such a distribution of light absorptance, the light absorptance of sunlight will be 10% or less, which corresponds to 100 W or less in terms of energy.

[0037] In other words, the light absorption rate of sunlight increases as the thickness of the resin material layer increases. When 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 The solar light absorption in the light reflecting layer is 50 W / m ２ Therefore, it is preferable that the sum of the solar absorption in the resin material layer and the light reflective layer is 150 W / m or less. 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.

[0038] In addition, from the viewpoint of the emissivity (thermal radiation characteristics) of the resin material layer emitting infrared light, the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm needs to be 40% or more. ２ In order to release the thermal radiation of sunlight from the resin material layer into space, the resin material layer must 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 of 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."

[0039] In addition, the environment in which the composite cooling material 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 with 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.

[0040] In consideration of this situation, the wavelength average of the emissivity of the wavelength from 8 μm to 14 μm is set to 40% or more (thermal radiation intensity in the atmospheric window band is 50 W / m ２Unless the thickness of the resin material layer is within the above-mentioned optical specification range, the heat output from the atmospheric window becomes greater than the heat input due to the absorption of sunlight, enabling radiative cooling outdoors even in a daytime solar radiation environment. In other words, when the resin material layer is formed of a vinyl chloride resin or a vinylidene chloride resin, the thickness of the resin material layer is preferably 100 μm or less and 10 μm or more.

[0041] In short, according to a further characteristic configuration of the composite cooling material, the heat output at the atmospheric window is greater than the heat input due to the absorption of sunlight, enabling radiative cooling outdoors even in a solar radiation environment.

[0042] A further characteristic feature of the composite cooling material is that the light reflecting layer has a reflectance of 90% or more for wavelengths of 0.4 μm to 0.5 μm and a reflectance of 96% or more for wavelengths longer than 0.5 μm.

[0043] That is, the solar spectrum exists in the wavelength range of 0.295 μm to 4 μm, and the intensity increases as the wavelength increases from 0.4 μm, with the intensity being particularly high in the wavelength range of 0.5 μm to 2.5 μm. If the light-reflective layer has reflective characteristics 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 in wavelengths longer than 0.5 μm, the light-reflective layer will only absorb about 5% or less of the solar energy.

[0044] As a result, the solar energy absorbed by the light-reflecting layer at noon in summer was 50 W / m ２ The 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.

[0045] In short, this further characteristic configuration of the composite cooling material makes it possible to suppress the absorption of solar energy by the light reflecting layer and to perform effective radiative cooling by the resin material layer.

[0046] A further characteristic feature of the composite cooling material is that the light reflecting layer has a thickness of 50 nm or more.

[0047] That is, in order to give the light-reflecting layer 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, the reflective material on the radiation surface side of the light-reflecting layer needs to be silver or a silver alloy, as described above. And, as in the above-mentioned characteristic configuration, when a light-reflecting layer made only of silver or a silver alloy reflects sunlight while having the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required.

[0048] In short, according to the further characteristic configuration of the composite cooling material of the present invention, the absorption of solar energy by the light reflecting layer can be appropriately suppressed, and radiative cooling by the resin material layer can be performed well.

[0049] A further characteristic feature of the composite cooling material is that the light-reflecting layer has a laminated structure of silver or a silver alloy located closer to the resin material layer and aluminum or an aluminum alloy located farther from the resin material layer.

[0050] That is, to give the light-reflecting layer the aforementioned reflectivity characteristics, a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated may be used. Note that in this case, the reflective material on the radiation surface side must also be silver or a silver alloy. In this case, the thickness of the silver must be 10 nm or more, and the thickness of the aluminum must be 30 nm or more.

[0051] Furthermore, since aluminum or an aluminum alloy is cheaper than silver or a silver alloy, it is possible to reduce the cost of the light-reflecting layer while maintaining appropriate reflectivity characteristics. In other words, by reducing the thickness of expensive silver or a silver alloy to reduce the cost of the light-reflecting layer, and by forming the light-reflecting layer into a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy, it is possible to reduce the cost of the light-reflecting layer while maintaining appropriate reflectivity characteristics.

[0052] In short, this further characteristic configuration of the composite cooling material makes it possible to reduce the cost of the light reflecting layer while still providing appropriate reflectance characteristics.

[0053] 1 is a diagram illustrating the basic configuration of a composite cooling material; FIG. 2 is a diagram illustrating the relationship between light absorptance and wavelength of a resin material; FIG. 3 is a diagram illustrating the emissivity spectrum of vinyl chloride resin; FIG. 4 is a diagram illustrating the emissivity spectrum of vinylidene chloride resin; FIG. 5 is a diagram illustrating the light reflectance spectrum of a silver-based light-reflecting layer; FIG. 6 is a diagram illustrating a specific configuration of a composite cooling material; FIG. 7 is a diagram illustrating a specific configuration of a composite cooling material; FIG. 8 is a diagram illustrating a specific configuration of a composite cooling material; FIG. 9 is a diagram illustrating a specific configuration of a composite cooling material; FIG. 10 is a diagram illustrating the relationship between light transmittance and wavelength of polyethylene; FIG. 11 is a diagram illustrating a test configuration; FIG. 12 is a diagram illustrating test results when the protective layer is polyethylene; FIG. 13 is a diagram illustrating test results when the protective layer is ultraviolet-absorbing acrylic; FIG. 14 is a diagram illustrating the emissivity spectrum of polyethylene; FIG. 15 is a diagram illustrating experimental results for a plasticizer mixed into a vinyl chloride resin; FIG. 16 is a diagram illustrating another configuration of a cooling layer; FIG. 17 is a diagram illustrating a configuration in which a cooling layer is formed with an uneven shape; FIG. 18 is a diagram illustrating a specific example of the uneven shape of a cooling layer; FIG. 19 is a diagram illustrating a configuration in which a resin material layer has a light-reflecting portion; FIG. 20 is a diagram illustrating a configuration in which a glue layer has a light-reflecting portion. 10 is a diagram illustrating a configuration in which a glue layer is provided with a light reflecting portion, FIG. 11 is a graph illustrating experimental results, and FIG. 12 is a diagram illustrating a configuration in which the front and back surfaces of a resin material layer are uneven.

[0054] Hereinafter, an embodiment of the present invention will be described with reference to the drawings. [Basic configuration of composite cooling material] As shown in Fig. 1, the composite cooling material W is configured such that a film-like cooling layer CP is connected (adhered) to the outer surface of a magnetic material layer E containing a magnetic material having magnetic force, and the back side of the magnetic material layer E (the lower side in Fig. 1: the side of the magnetic material layer E opposite to the side where the cooling layer CP is present) is cooled by the radiative cooling action of the cooling layer CP. In Fig. 1, the cooling layer CP is connected to the outer surface of the magnetic material layer E by a connecting layer S made of resin, which will be described later.

[0055] 1 illustrates an example in which a composite cooling material W is attached to a warehouse 1 having a roof and side surfaces made of metal plates. That is, a plurality of composite cooling materials W are attached to the roof and surrounding side surfaces of the warehouse 1. Suitable examples of the metal plates to be attached include iron, iron alloys, steel plates, etc., which can be attached by the magnetic force generated by a magnetic material.

[0056] The cooling layer CP is formed in a film-like state and includes an infrared radiation layer A that emits infrared light IR from the radiation surface H, a light reflecting layer B that is located on the infrared radiation layer A on the side opposite to the side where the radiation surface H exists, and a protective layer D between the infrared radiation layer A and the light reflecting layer B. In other words, the cooling layer CP is configured as a radiative cooling film. The cooling layer CP has a first optical property of solar reflectance of 80% or more and a second optical property of average emissivity of 80% or more, which is the wavelength average of the emissivity of infrared light from 8 μm to 14 μm.

[0057] The light-reflecting layer B reflects light L, such as sunlight, that has passed through the infrared radiation layer A and the protective layer D, and has reflection characteristics such that the reflectance is 90% or more at wavelengths of 400 nm to 500 nm and 96% or more at wavelengths longer than 500 nm. The sunlight spectrum exists in the wavelength range of 300 nm to 4000 nm, and the intensity increases as the wavelength increases from 400 nm, with the intensity being particularly high in the wavelength range of 500 nm to 1800 nm.

[0058] In this embodiment, light L includes ultraviolet light (ultraviolet rays), visible light, and infrared light, and when these are expressed 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). Incidentally, in this specification, the wavelength range of ultraviolet light (ultraviolet rays) is assumed to be between 295 nm and 400 nm.

[0059] The light-reflecting layer B exhibits a reflectivity of 90% or more in the wavelength range of 400 nm to 500 nm, and a reflectivity of 96% or more for wavelengths longer than 500 nm, so that the solar energy absorbed by the cooling layer CP (radiative cooling film) in the light-reflecting layer B can be reduced to 5% or less. In other words, the solar energy absorbed at noon in summer can be reduced to about 50 W.

[0060] The light-reflecting layer B is made of silver or a silver alloy, or is constructed as a laminated structure of silver or a silver alloy located adjacent to the protective layer D and aluminum or an aluminum alloy located away from the protective layer D, and is flexible, details of which will be described later.

[0061] The infrared radiation layer A is constructed as a resin material layer J made of vinyl chloride resin or vinylidene chloride resin whose thickness is adjusted so that it emits thermal radiation energy greater than the absorbed solar light energy in the wavelength range of 8 μm to 14 μm, and details of which will be described later.

[0062] Therefore, the cooling layer CP is configured to reflect a portion of the light L incident on the cooling layer CP at the radiation surface H of the infrared radiation layer A, and to reflect the light (sunlight, etc.) that has passed through the resin material layer J and the protective layer D from the light incident on the cooling layer CP at the light reflection layer B and to allow it to escape to the outside from the radiation surface H.

[0063] The heat input to the cooling layer CP from the magnetic material layer E, which is located on the opposite side of the resin material layer J in the light-reflecting layer B (for example, heat input due to thermal conduction from the magnetic material layer E), is converted into infrared light IR by the resin material layer J and radiated, thereby cooling the magnetic material layer E (more specifically, the side of the magnetic material layer E opposite to the side where the cooling layer CP is located).

[0064] That is, the cooling layer CP is configured to reflect the light L irradiated onto the cooling layer CP, and to radiate heat transferred to the cooling layer CP (for example, heat transferred from the atmosphere or from the magnetic material layer E) to the outside as infrared light IR. Furthermore, the resin material layer J, the protective layer D, and the light reflecting layer B are flexible, so that the cooling layer CP (radiative cooling film) is configured to be flexible.

[0065] The magnetic material layer E contains ferrite as a magnetic material and a binder resin. The thickness of the magnetic material layer E is, for example, about 0.2 mm to 2.0 mm. Specifically, the magnetic material layer E is a magnet sheet made by mixing pulverized ferrite and a binder resin, forming the mixture into a sheet, and then magnetizing the sheet.

[0066] [Overview of Resin Material Layer] The light absorptivity and emissivity (light emissivity) of the resin material forming 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).

[0067] Specifically, from the viewpoint of the light absorptance of sunlight, the thickness of the resin material layer J needs to be adjusted so that the wavelength-average light absorptance of the light from 0.4 μm to 0.5 μm is 13% or less, the wavelength-average light absorptance of the light from 0.5 μm to 0.8 μm is 4% or less, the wavelength-average light absorptance of the light from 0.8 μm to 1.5 μm is within 1%, the wavelength-average light absorptance of the light from 1.5 μm to 2.5 μm is 40% or less, and the wavelength-average light absorptance of the light from 2.5 μm to 4 μm is 100% or less. With such an absorptance distribution, the light absorptance of sunlight is 10% or less, which corresponds to 100 W or less in terms of energy.

[0068] As will be described later, the light absorption rate of the resin material increases as the resin material film thickness 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 protective layer D 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 protective layer D, and the light-reflecting layer B is 150 W / m or less. ２ As described above, it is preferable to use a resin material that has a small light absorptance near the peak value of the solar spectrum as the resin material for forming the resin material layer J.

[0069] From the viewpoint of infrared radiation (thermal radiation), the thickness of the resin material layer J needs to be adjusted so that the wavelength average of the emissivity in the wavelength range of 8 μm to 14 μm is 40% or more. ２ In order to release the thermal energy of sunlight of about 100 W / m² from the resin material layer J into space through the thermal radiation of the resin material layer J, the resin material layer J must emit a thermal radiation of more than that. For example, when the outside temperature is 30°C, the maximum thermal radiation of an atmospheric window of 8 μm to 14 μm is 200 W / m². 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."

[0070] In addition, the environment in which the cooling layer CP (radiative cooling film) 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 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 In consideration of this situation, the wavelength average of the emissivity in the wavelength range from 8 μm to 14 μm is set to 40% or more (when the 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.

[0071] Therefore, if the thickness of the resin material layer J is adjusted to fall within the optically specified range in consideration of the above matters, the heat output at the atmospheric window will be greater than the heat input due to sunlight absorption, and radiative cooling will be possible outdoors even in a solar radiation environment. In this embodiment, the thickness of the vinyl chloride resin or vinylidene chloride resin forming the resin material layer J is 100 μm or less and 10 μm or more.

[0072] [Resin Material Details] According to Kirchhoff's law, the emissivity (ε) and the optical absorptivity (A) are equal. The optical absorptivity can be calculated from the absorption coefficient (α) using the equation A = 1 - exp(-αt) (hereinafter referred to as the optical absorptivity equation), where t is the film thickness. In other words, adjusting the film thickness of the resin material layer J allows for greater thermal radiation in wavelength bands with larger absorption coefficients. When performing radiative cooling outdoors, it is recommended to use a material with a large absorption coefficient in the wavelength range of 8 μm to 14 μm, which is the atmospheric window wavelength band. Furthermore, to suppress the absorption of sunlight, it is recommended to use a material with no or a small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, especially 0.4 μm to 2.5 μm. As can be seen from the equation for the absorption coefficient and absorptivity, the optical absorptivity (emissivity) varies depending on the film thickness of the resin material.

[0073] 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.

[0074] 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 as the range of wavelengths from 0.4 μm to 0.8 μm, near-infrared light as the range of wavelengths from 0.8 μm to 3 μm, mid-infrared light as the range of wavelengths from 3 μm to 8 μm, and far-infrared light as the range of wavelengths longer than 8 μm.

[0075] Regarding carbon-chlorine bonds (C-Cl), the bond energy between carbon and chlorine in alkenes is 3.28 eV, and the wavelength is 0.378 μm, so they absorb a lot of ultraviolet light in sunlight, but have almost no absorption in the visible range. Figure 2 shows the absorptance spectrum from ultraviolet to visible range for a 100 μm thick vinyl chloride resin, which exhibits increased light absorption at wavelengths shorter than 0.38 μm. Figure 2 shows the absorptance spectrum from ultraviolet to visible range for a 100 μm thick vinylidene chloride resin, which exhibits a slight increase in the absorptance spectrum at wavelengths shorter than 0.4 μm.

[0076] Incidentally, FIG. 2 also shows the absorption spectrum of an ethylene terephthalate resin having a thickness of 40 μm in the ultraviolet to visible region, and the absorption spectrum of an ethylene resin in the ultraviolet to visible region.

[0077] Figure 3 shows the emissivity of polyvinyl chloride (PVC) resin with carbon-chlorine bonds at the atmospheric window. Figure 4 shows the emissivity of polyvinylidene chloride (PVDC) resin with carbon-chlorine bonds at the atmospheric window. Regarding carbon-chlorine bonds, the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. Furthermore, in the case of polyvinyl chloride resin, due to the electron-withdrawing effect of chlorine, an absorption coefficient resulting from the C-H bending vibration of the alkene contained in the main chain appears at a wavelength of around 10 μm. The same is true for polyvinylidene chloride resin. Due to these effects, the wavelength-averaged emissivity of a 10 μm-thick film is 43% from 8 μm to 14 μm, which falls within the wavelength-averaged emissivity requirement of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0078] 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. As shown in Figure 4, it can be seen that vinylidene chloride resin is similar to vinyl chloride resin.

[0079] As described above, thermal radiation from the atmospheric window region generated from the surface of the resin material occurs within a depth of approximately 100 μm from the surface. As the resin thickness increases beyond this, the cold generated by the radiation cooling of the cooling layer CP is insulated by the resin material, which does not contribute to thermal radiation. Ideally, consider fabricating a resin material layer J on the light-reflecting layer B, which does not absorb any sunlight. In this case, sunlight is absorbed only by the light-reflecting layer B of the cooling layer CP. The thermal conductivity of resin materials is generally about 0.2 W / m / K. Taking this thermal conductivity into account, calculations show that if the thickness of the 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.

[0080] Even if an ideal resin material that does not absorb sunlight at all exists, the thermal conductivity of resin materials is generally about 0.2 W / m / K, so if the thickness exceeds 20 mm, the light reflecting layer B will be heated by sunlight, and the magnetic material layer E placed on the light reflecting layer side will also be heated. In other words, the thickness of the resin material of the cooling layer CP needs to be 20 mm or less.

[0081] [Regarding the thickness of the resin material layer] From the viewpoint of practical use of the cooling layer CP, it is preferable that the thickness of the resin material layer J is thin. The thermal conductivity of resin materials is generally lower than that of metals, glass, etc. In order to effectively cool the magnetic material layer E, it is preferable that the film thickness of the resin material layer J is kept to the minimum necessary. The thicker the film thickness of the resin material layer J, the greater the thermal radiation from the atmospheric window, and once a certain film thickness is exceeded, the thermal radiation energy from the atmospheric window becomes saturated.

[0082] The film thickness at which saturation occurs depends on the resin material, but in the case of a resin 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 magnetic material layer E can be lowered, so in the case of a resin containing carbon-chlorine bonds, a thickness of 50 μm or less reduces the heat insulating properties and allows the magnetic material layer E to be cooled effectively. In the case of carbon-chlorine bonds, a thickness of 100 μm or less allows the magnetic material layer E to be cooled effectively.

[0083] The benefit of making the material thinner is not only that it reduces heat insulation and makes it easier to conduct heat. This is because resins containing carbon-chlorine bonds exhibit CH, CH in the near-infrared region. ２ , C.H. ３ The reason is the suppression of light absorption in the near-infrared region caused by the cooling layer CP. By making the layer thinner, the solar absorption caused by these factors can be reduced, thereby increasing the cooling capacity of the cooling layer CP. From the above perspective, in the case of vinyl chloride resin and vinylidene chloride resin, which are resins containing carbon-chlorine bonds, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0084] [Details of the Light Reflecting Layer] In order for the light reflecting layer B to have the above-mentioned reflectance characteristics, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) needs to be silver or a silver alloy. As shown in Fig. 5, if the light reflecting layer B is formed based on silver, the desired reflectance of the light reflecting layer B can be obtained.

[0085] When reflecting sunlight with only silver or a silver alloy while maintaining the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required. However, in order to provide flexibility to the light-reflecting layer B, the thickness needs to be 100 μm or less. If it is thicker than this, it becomes difficult to bend. Incidentally, as a "silver alloy," 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 can be used. As a specific example, "APC-TR (manufactured by Furuya Metal)," a silver alloy made by adding copper and palladium to silver, can be used.

[0086] In order to provide the light-reflecting layer B with the above-mentioned reflectivity characteristics, a laminated structure may be used in which silver or a silver alloy is located adjacent to the protective layer D and aluminum or an aluminum alloy is located away from the protective layer D. Even in this case, the reflective material on the side where the radiation surface H exists (the side where the resin material layer J exists) must be silver or a silver alloy. When configured with two layers of silver (silver alloy) and aluminum (aluminum alloy), the thickness of the silver must be 10 nm or more, and the thickness of the aluminum must be 30 nm or more. However, in order to provide flexibility to the light-reflecting layer B, the total thickness of the silver and aluminum must be 100 μm or less. If it is thicker than this, it will be difficult to bend.

[0087] Incidentally, as an "aluminum alloy," an alloy in which copper, manganese, silicon, magnesium, zinc, carbon steel for mechanical structures, yttrium, lanthanum, gadolinium, or terbium is added to aluminum can be used.

[0088] Silver and silver alloys are vulnerable to rain and humidity and need to be protected from these and to prevent discoloration. For this reason, a protective layer D is required to protect the silver and silver alloy, and is placed adjacent to the silver or silver alloy, as shown in Figures 6 to 9. Details of the protective layer D will be described later.

[0089] [Specific configuration of composite cooling material] Since the resin material forming the resin material layer J and the protective layer D of the cooling layer CP is flexible, when the light reflecting layer B is made thin, the light reflecting layer B can also be made flexible, and as a result, the cooling layer CP can be made into a flexible film (radiative cooling film).

[0090] 6 to 9, the magnetic material layer E can be cooled by attaching the cooling layer CP (radiative cooling film) to the outer surface of the magnetic material layer E with a connecting layer S made of an adhesive or pressure-sensitive adhesive. The adhesive or pressure-sensitive adhesive used in the connecting layer S includes one or more of vinyl chloride resin, vinylidene chloride resin, polyolefin resin, polyester resin, acrylic resin, urethane resin, silicone resin, and rubber resin. Preferably, the connecting layer S includes at least one of vinyl chloride resin and polyolefin resin.

[0091] There are various possible ways to prepare the cooling layer CP in the form of a film. For example, it is possible to prepare it by applying a protective layer D and a resin material layer J to a light-reflecting layer B prepared in the form of a film. Alternatively, it is possible to prepare it by attaching a protective layer D and a resin material layer J to a light-reflecting layer B prepared in the form of a film. Alternatively, it is possible to prepare it by applying or attaching a protective layer D to a resin material layer J prepared in the form of a film, and then prepare a light-reflecting layer B on the protective layer D by vapor deposition, sputtering, ion plating, silver mirror reaction, or the like.

[0092] Specifically, the cooling layer CP (radiative cooling film) in Fig. 6 is configured such that, when the light reflecting layer B is formed as a single layer of silver or silver alloy, or is configured as two layers of silver (silver alloy) and aluminum (aluminum alloy), a protective layer D is formed on the upper side of the light reflecting layer B, and a resin material layer J is formed on the protective layer D, and a lower protective layer Ds is also formed below the light reflecting layer B. Incidentally, the lower protective layer Ds is formed of, for example, acrylic resin.

[0093] The cooling layer CP (radiative cooling film) in Figure 6 can be produced by sequentially applying a protective layer D, a light-reflecting layer B, and a lower protective layer Ds onto a film-like resin material layer J, and molding them integrally.

[0094] The cooling layer CP (radiative cooling film) in Fig. 7 has a light-reflecting layer B composed of an aluminum layer B1 made of aluminum foil that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy, a protective layer D formed on the upper side of the light-reflecting layer B, and a resin material layer J formed on the upper side of the protective layer D.

[0095] The cooling layer CP (radiative cooling film) in Fig. 7 can be fabricated by sequentially applying a silver layer B2, a protective layer D, and a resin material layer J on an aluminum layer B1 made of aluminum foil, and molding them into an integrated structure. Alternatively, the resin material layer J can be formed into a film, and the protective layer D and silver layer B2 can be sequentially applied on the film-like resin material layer J, and the aluminum layer B1 can be attached to the silver layer B2.

[0096] The cooling layer CP (radiative cooling film) in Fig. 8 is obtained by forming a protective layer D on the upper side of the light reflecting layer B, forming a resin material layer J on the top of the protective layer D, and forming a film layer F such as PET on the lower side of the light reflecting layer B, when the light reflecting layer B is formed as a single layer of silver or silver alloy, or when it is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy).

[0097] The cooling layer CP (radiative cooling film) in Fig. 8 can be fabricated by sequentially applying a light-reflecting layer B and a protective layer D onto a film layer F (corresponding to the substrate) formed of PET (ethylene terephthalate resin) or the like, and integrally molding them, and then adhering a separately formed film-like resin material layer J to the protective layer D with an adhesive layer N. The adhesive (pressure-sensitive adhesive) used in the adhesive layer N can be, for example, a urethane-based adhesive (pressure-sensitive adhesive), an acrylic-based adhesive (pressure-sensitive adhesive), or an EVA (ethylene vinyl acetate)-based adhesive (pressure-sensitive adhesive), and preferably one with high transparency to sunlight.

[0098] The cooling layer CP (radiative cooling film) in Fig. 9 has a light-reflecting layer B composed of an aluminum layer B1 that functions as aluminum (aluminum alloy) and a silver layer B2 that is made of silver or a silver alloy (silver substitute), and the aluminum layer B1 is formed on top of a film layer F (corresponding to the substrate) that is made of PET (ethylene terephthalate resin) or the like in the form of a film, a protective layer D is formed on the silver layer B2, and a resin material layer J is formed on the protective layer D.

[0099] The cooling layer CP (radiative cooling film) in Fig. 9 can be fabricated by applying an aluminum layer B1 onto a film layer F to integrally form the film layer F and the aluminum layer B1, separately applying a protective layer D and a silver layer B2 onto a film-like resin material layer J to integrally form the resin material layer J, the protective layer D, and the silver layer B2, and then bonding the aluminum layer B1 and the silver layer B2 with a glue layer N. The adhesive (pressure-sensitive adhesive) used in the glue layer N can be, for example, a urethane-based adhesive (pressure-sensitive adhesive), an acrylic-based adhesive (pressure-sensitive adhesive), or an EVA (ethylene vinyl acetate)-based adhesive (pressure-sensitive adhesive), and preferably one with high transparency to sunlight.

[0100] [Details of Protective Layer] The protective layer D is made of a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or polyethylene terephthalate having a thickness of 17 μm or more and 40 μm or less. Examples of polyolefin resins include polyethylene and polypropylene.

[0101] As described above, the ultraviolet absorption rate of polyethylene is shown in Fig. 2. Also, the light transmittance of polyethylene, which is suitable as the synthetic resin for forming the protective layer D, is shown in Fig. 10.

[0102] The cooling layer CP (radiative cooling film) exerts a radiative cooling effect not only at night but also under a solar radiation environment. Therefore, in order to maintain the light reflecting layer B in a state in which it can reflect light, it is necessary to protect the light reflecting layer B with a protective layer D so that the silver of the light reflecting layer B does not discolor under a solar radiation environment.

[0103] When the protective layer D is formed from a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, the polyolefin resin is a synthetic resin whose ultraviolet light absorption rate is 10% or less over the entire ultraviolet wavelength range from 0.295 μm to 0.4 μm, and therefore the protective layer D is less likely to deteriorate due to absorption of ultraviolet rays.

[0104] Furthermore, since the thickness of the polyolefin resin forming protective layer D is 300 nm or more, it effectively performs blocking functions such as blocking radicals generated in resin material layer J from reaching the silver or silver alloy forming the light-reflecting layer, and blocking moisture that penetrates resin material layer J from reaching the silver or silver alloy forming light-reflecting layer B, thereby suppressing discoloration of the silver or silver alloy forming light-reflecting layer B.

[0105] Incidentally, the protective layer D made of polyolefin resin deteriorates by absorbing ultraviolet rays, 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 B. Furthermore, even if the protective layer D deteriorates by forming radicals, the rate of deterioration is slow due to the low absorption of ultraviolet rays, and therefore the above-mentioned blocking function can be maintained for a long period of time.

[0106] When the protective layer D is formed from ethylene terephthalate resin to a thickness of 17 μm or more and 40 μm or less, ethylene terephthalate resin is a resin material that has a higher ultraviolet light absorption rate in the ultraviolet wavelength range of 0.295 μm to 0.4 μm than polyolefin resin. However, since the thickness is 17 μm or more, it can effectively perform blocking functions for a long period of time, such as blocking radicals generated in the resin material layer J from reaching the silver or silver alloy that forms the light-reflecting layer B, and blocking moisture that penetrates the resin material layer J from reaching the silver or silver alloy that forms the light-reflecting layer, thereby suppressing discoloration of the silver or silver alloy that forms the light-reflecting layer B.

[0107] In other words, the protective layer D made of ethylene terephthalate resin deteriorates as it absorbs ultraviolet rays, forming radicals on the surface side away from the light-reflecting layer B. However, since the thickness is 17 μm or more, the formed radicals do not reach the light-reflecting layer B. Furthermore, even if the protective layer D deteriorates while forming radicals, the thickness is 17 μm or more, so the above-mentioned blocking function can be maintained for a long period of time.

[0108] To explain further, the deterioration of ethylene terephthalate resin (PET) is caused by ultraviolet light cleaving the ester bond between ethylene glycol and terephthalic acid to form radicals. This deterioration progresses from the surface of the PET that is irradiated with ultraviolet light.

[0109] For example, when ethylene terephthalate resin (PET) is irradiated with ultraviolet light of the intensity in Osaka, the ester bonds of the ethylene terephthalate resin (PET) are cleaved by about 9 nm per day, starting from the irradiated surface. Because the ethylene terephthalate resin (PET) is sufficiently polymerized, the cleaved ethylene terephthalate resin (PET) on the surface does not attack the silver (silver alloy) of the light-reflecting layer B. However, if the cleaved end of the ethylene terephthalate resin (PET) reaches the silver (silver alloy) of the light-reflecting layer B, the silver (silver alloy) will discolor.

[0110] Therefore, in order for the protective layer D to last for one year or more when used outdoors, a thickness of approximately 3 μm is required, calculated by multiplying 9 nm / day by 365 days. In order for the ethylene terephthalate resin (PET) of the protective layer D to last for three years or more, a thickness of 10 μm or more is required. In order for it to last for five years or more, a thickness of 17 μm or more is required.

[0111] When the protective layer D is formed of a polyolefin resin and an ethylene terephthalate resin, the reason for setting an upper limit on the thickness is to prevent the protective layer D from exhibiting heat insulating properties that do not contribute to radiative cooling. In other words, the thicker the protective layer D, the more heat insulating properties it exhibits that do not contribute to radiative cooling. Therefore, an upper limit on the thickness is set to prevent the protective layer D from exhibiting heat insulating properties that do not contribute to radiative cooling while still providing the function of protecting the light reflecting layer B.

[0112] In other words, while a thick protective layer D does not pose a disadvantage in terms of preventing coloration of the silver (silver alloy) in the light-reflecting layer B, it does cause problems in terms of radiative cooling. In other words, a thicker protective layer D increases the insulating properties of the radiative cooling material. For example, a resin whose main component is polyethylene, which is an excellent synthetic resin for forming the protective layer D, has a low emissivity at the atmospheric window, as shown in Figure 14, and therefore does not contribute to radiative cooling even if it is formed thick. On the contrary, a thicker protective layer D increases the insulating properties of the radiative cooling material. Next, a thicker protective layer D increases absorption in the near-infrared region due to main chain vibrations, enhancing the effect of increasing solar absorption. Due to these factors, a thick protective layer D is disadvantageous for radiative cooling. From this perspective, the thickness of the protective layer D formed from a polyolefin resin is preferably 5 μm or less, and even more preferably 1 μm.

[0113] As shown in Figure 8, when a glue layer N is located between the resin material layer J and the protective layer D, radicals will also be generated from the glue layer N. However, if the thickness of the polyolefin resin forming the protective layer D is 300 nm or more and the thickness of the ethylene terephthalate resin forming the protective layer D is 17 μm or more, the radicals generated in the glue layer N can be prevented from reaching the light-reflecting layer B for a long period of time.

[0114] [Considerations on the Protective Layer] To examine the difference in silver coloration due to the protective layer D, samples were prepared in which the protective layer D was exposed and did not include the resin material layer J serving as the infrared radiation layer A, as shown in FIG. 11 , and the coloration of the silver after irradiation with simulated sunlight was examined. Specifically, samples were prepared in which two types of protective layer D, a typical acrylic resin that absorbs ultraviolet light (e.g., methyl methacrylate resin mixed with a benzotriazole-based ultraviolet absorber) and polyethylene, were applied using a bar coater to a film layer F (corresponding to the substrate) containing silver serving as the light-reflecting layer B, and the function of the protective layer D was examined. The thicknesses of the applied protective layers D were 10 μm and 1 μm, respectively. The film layer F (corresponding to the substrate) was formed into a film shape using PET (ethylene terephthalate resin) or the like.

[0115] As shown in Figure 13, when the protective layer D is made of an acrylic resin that absorbs ultraviolet rays well, the protective layer D is decomposed by ultraviolet rays to form radicals, and the silver immediately turns yellow and ceases to function as a cooling layer CP (it absorbs sunlight and, like ordinary materials, its temperature rises when exposed to sunlight). The 600h line in the figure indicates the temperature of the protective layer D after a xenon weather test (ultraviolet light energy of 60 W / m) under the conditions of JIS standard 5600-7-7. ２ The line at 0h is the reflectance spectrum before the xenon weathering test.

[0116] As shown in Figure 12, when the protective layer D is made of polyethylene, which has a low ultraviolet light absorption rate, it can be seen that there is no decrease in reflectance from the near-infrared region to the visible region. In other words, a resin whose main component is polyethylene (polyolefin resin) hardly absorbs the ultraviolet light contained in sunlight that reaches the ground, and therefore is unlikely to form radicals even when exposed to sunlight, so that coloring of the silver serving as the light-reflecting layer B does not occur even when exposed to sunlight. The 600h line in the figure indicates the result of a xenon weather test (ultraviolet light energy of 60 W / m) under the conditions of JIS standard 5600-7-7. ２ The line at 0h is the reflectance spectrum before the xenon weathering test.

[0117] The reason for the undulation of the reflectance spectrum in this wavelength range is the Fabry-Perot resonance of the polyethylene layer. It can be seen that the resonance position is slightly different between the 0h line and the 600h line due to changes in the thickness of the polyethylene layer caused by heat during the xenon weather test, but no significant decrease in reflectance in the ultraviolet-visible region due to yellowing of the silver is observed.

[0118] From the viewpoint of ultraviolet absorption, fluororesin-based materials can also be used as materials for forming the protective layer D, but when actually formed as the protective layer D, they become discolored and deteriorate during the formation stage, and therefore cannot be used as materials for forming the protective layer D. Furthermore, from the viewpoint of ultraviolet absorption, silicone can also be used as materials for forming the protective layer D, but it has extremely poor adhesion to silver (silver alloys), and therefore cannot be used as materials for forming the protective layer D.

[0119] [Regarding the incorporation of plasticizers] When the resin material layer J is formed from a vinyl chloride resin, it is preferable to incorporate a plasticizer into the vinyl chloride resin to improve its flexibility. The plasticizer to be incorporated into the vinyl chloride resin is one of phthalate esters, aliphatic dibasic acid esters, and phosphate esters. The plasticizer is incorporated in an amount ranging from 1 part by weight to 200 parts by weight per 100 parts by weight of the vinyl chloride resin. From the viewpoint of processing, it is preferable that the amount of plasticizer be 100 parts by weight or less.

[0120] The aliphatic dibasic acid ester of the plasticizer may be composed of adipic acid esters, adipic acid ester copolymers, azelaic acid esters, azelaic acid ester copolymers, sebacic acid esters, sebacic acid ester copolymers, succinic acid esters, and succinic acid ester copolymers, either alone or in combination.

[0121] The aliphatic dibasic acid ester of the plasticizer is preferably an ester bond between an aliphatic dibasic acid and two molecules of a saturated aliphatic alcohol. The phthalic acid ester of the plasticizer is preferably an ester bond between phthalic acid and two molecules of a saturated aliphatic alcohol. The phosphate ester of the plasticizer is preferably a phosphate triester or an aromatic phosphate ester.

[0122] <Details of Phthalate Esters> Phthalate esters can be listed as follows: dimethyl phthalate (DMP), diethyl phthalate (DEP), dibutyl phthalate (DPP), di-2-ethylhexyl phthalate (DOP), diisononyl phthalate (DINP), diisodecyl phthalate (DIDP), diundecyl phthalate (DUP), ditridecyl phthalate (DTDP), bis(2-ethylhexyl) terephthalate (DOTP), bis(2-ethylhexyl) isophthalate (DOIP), etc.

[0123] <Details of Aliphatic Dibasic Acid Esters> Aliphatic dibasic acid esters include the following: 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), etc. Also, aliphatic polyesters 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).

[0124] <Phosphate Triester> The phosphate triesters are listed as follows: trimethyl phosphate (TMP), triethyl phosphate (TEP), tributyl phosphate (TBP), tris(2-ethylhexyl) phosphate (TOP).

[0125] <Aromatic Phosphate Ester> Aromatic phosphate esters are listed as follows: triphenyl phosphate (TPP), tricresyl phosphate (TCP), trixylenyl phosphate (TXP), tresyl diphenyl phosphate (CDP), and 2-ethylhexyl diphenyl phosphate.

[0126] <Evaluation of Appropriate Plasticizers> Plasticizers for vinyl chloride resin include phthalate esters, aliphatic dibasic acid esters, phosphate triesters, aromatic phosphate esters, trimellitates, 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. Furthermore, 0.5 parts by weight of a triazine-based ultraviolet absorber and a hindered amine-based light stabilizer were kneaded into the vinyl chloride resin per 100 parts by weight of vinyl chloride.

[0127] 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 approximately 1000), and diisononyl adipate (DINA). Representative phosphate triesters include tributyl phosphate (TBP). Representative aromatic phosphate esters include tricresyl phosphate (TCP). Representative trimellitic acid esters include tri-2-ethylhexyl trimellitate (TOTM). Representative epoxidized fatty acid esters include epoxidized soybean oil.

[0128] The durability test was a xenon weather test conducted for 1,920 hours (equivalent to four years of actual exposure), and the durability was judged based on the results. 487 hours is equivalent to one year of ultraviolet light. The conditions for the xenon weather test were as follows: ultraviolet light intensity 180 W / m ２ (Wavelength 295-400nm). <Conditions without watering> BPT 89°C, humidity 50%, 1 hour 42 minutes. <Conditions with watering> Tank temperature 38°C, humidity 90%, 18 minutes.

[0129] The results of the 1920-hour test are shown in Figure 15. 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. The epoxidized fatty acid turned brown after 1120 hours, making it impossible to continue the test, and therefore is not shown in the figure.

[0130] In contrast, it was found that when a phthalate ester, an aliphatic dibasic acid ester, a phosphate triester, or an aromatic phosphate ester was used as a plasticizer to be mixed into the vinyl chloride resin, the reflectance of the cooling layer CP did not decrease even after about four years, but when a trimellitate ester or an epoxidized fatty acid ester was used as a plasticizer to be mixed into the vinyl chloride resin, the reflectance of the cooling layer CP decreased significantly even before about four years had passed.

[0131] From the above test results, it can be seen 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. The reasons for this will be considered and systematized as described below.

[0132] [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.

[0133] 16 , the cooling layer CP may be configured to include an anchor layer G on top of a film layer F (corresponding to the substrate), and a light-reflecting layer B, a protective layer D, and an infrared radiation layer A on top of the anchor layer G. The film layer F (corresponding to the substrate) is formed into a film shape using, for example, PET (ethylene terephthalate resin) or the like.

[0134] The anchor layer is introduced to strengthen the adhesion between the film layer F and the light-reflecting layer B. In other words, if silver (Ag) is deposited directly on the film layer F, there is a risk that peeling may occur easily. The anchor layer G is preferably made primarily of acrylic, polyolefin, or urethane, with a compound having an isocyanate group or melamine resin mixed in. Since it is a coating for areas not directly exposed to sunlight, it is acceptable for it to be made of a material that absorbs ultraviolet rays. Note that there are other methods for strengthening the adhesion between the film layer F and the light-reflecting layer B besides inserting the anchor layer G. For example, irradiating the deposition surface of the film layer F with plasma to roughen the surface will increase adhesion.

[0135] [Considerations on the Connection Layer] The magnetic material layer E and the cooling layer CP are connected by a connection layer S between the magnetic material layer E and the cooling layer CP, the connection layer S containing one or more of vinyl chloride resin, vinylidene chloride resin, polyolefin resin, acrylic resin, urethane resin, silicone resin, and rubber resin. More preferably, the connection layer S contains at least vinyl chloride resin and polyolefin resin.

[0136] The thickness of the magnetic material layer E is preferably about 0.2 mm or more and 2.0 mm or less. As shown in Table 1 below, by making the thickness 0.2 mm or more, the magnetic force acting as an attachment force to the metal plate to be attached can be effectively exerted, thereby improving long-term adhesion stability. Furthermore, by making the thickness 2.0 mm or less, even if a heat source is present on the back side of the composite cooling material W (the side opposite the side where the cooling layer CP is present), heat dissipation from the back side (the side opposite the side where the cooling layer CP is present) to the outer side (the side where the cooling layer CP is present) can be maintained at a certain level or higher.

[0137] Table 2 shows the results of tests comparing the peelability and reusability of the magnetic material, the temperature difference between the temperature on the backside and the air temperature on the outer surface, and the thermal conductivity from the backside to the cooling layer CP with other materials. In this test, SPACECOOL Film SCF-A25M-ONS manufactured by SPACECOOL was used as the adhesive-backed film used as the other material for comparison, and SPACECOOL-200E manufactured by SPACECOOL was used as the membrane material. The test showed that the peelability and reusability of the magnetic material was similar to that of the membrane material, but higher than that of the adhesive-backed film. Regarding thermal conductivity, the results showed that the magnetic material exhibited high thermal conductivity, similar to that of the adhesive-backed film, and higher thermal conductivity than membrane materials in which an air layer is formed.

[0138] The composite cooling material W may have an uneven radiation surface H of the cooling layer CP as shown in FIG. 17 . That is, for example, the radiation surface H may be formed so that protrusions U are present. Specific examples of the uneven surface include a line-and-space structure in which rectangular parallelepiped protrusions U are arranged (see FIG. 18 ), a structure in which conical prism-shaped protrusions U are arranged vertically and horizontally (see FIG. 19 ), a structure in which triangular prism- or pyramidal protrusions U are arranged in a line-and-space pattern (not shown), a structure in which rectangular prism-shaped protrusions U are arranged vertically and horizontally, and a structure in which protrusions U are formed randomly. Incidentally, the height difference when forming the radiation surface H unevenly is about 100 μm.

[0139] When the radiation surface H is formed in an uneven shape, there is heat inflow from various heat sources into the inside of the magnetic material layer E of the composite cooling material W (the side opposite to the side where the cooling layer CP is present), and even though the cooling layer CP is provided, the temperature is likely to rise above the environmental temperature (outside air temperature) during the day. When the temperature inside the magnetic material layer E of the composite cooling material W is higher than the environmental temperature (outside air temperature), the outside air acts as a cold heat source, and it is desirable to increase heat exchange with the outside air. From this perspective, it is preferable to form the radiation surface H of the composite cooling material W in an uneven shape to increase the surface area and increase heat exchange with the wind on the side of the radiation surface H of the composite cooling material W.

[0140] From this perspective, it is advisable to increase the surface area by forming the infrared radiation layer A of the cooling layer CP into an uneven shape by embossing or the like, as shown in Fig. 17. In other words, this structure is advisable to be introduced when there is a heat source other than sunlight or heated air, the temperature of the magnetic material layer E on which the cooling layer CP is attached rises above the environmental temperature (outside air temperature), and the environmental temperature (outside air temperature) acts as a cold source.

[0141] Forming the radiation surface H in an uneven shape also has advantages in terms of appearance. When the radiation surface H is formed in an uneven shape, sunlight is scattered more than when the radiation surface H (upper surface) of the cooling layer CP is a mirror surface, so glare on the cooling layer CP is reduced. A less glare-causing cooling layer CP improves visibility, thereby increasing safety during driving. Furthermore, even if the radiation surface H is given the function of "scattering," light absorption in the silver (silver alloy) of the light-reflecting layer B does not increase, so radiative cooling can be performed well.

[0142] [Alternative Cooling Layer Configuration] As shown in Figures 20 and 21 , the resin material layer J constituting the infrared radiation layer A may include a plurality of granular light-reflecting regions Q that reflect light. The light-reflecting regions Q are composed of bubbles Qa, inorganic fillers Qb, and organic fillers Qc. The particle size of the light-reflecting regions Q is 1 nm to 300 μm, and more preferably 10 nm to 100 μm from the viewpoint of dispersibility and cohesion. The particle size of the light-reflecting regions Q is preferably the "average particle size" specified by JIS. Methods for forming the light-reflecting regions Q in the resin material layer J include, for example, calendar molding of a compound resin obtained by kneading the light-reflecting regions Q with a binder resin. However, this is not limited to this. The proportion of the light-reflecting regions Q in the resin material layer J is preferably approximately 0.01 vol% to 20 vol%. The light-reflecting regions Q are porous.

[0143] The inorganic filler Qb contains at least one of glass microbeads, ceramic microbeads, silicon oxide particles, silicon carbide particles, silicon nitride particles, barium sulfate particles, and calcium carbonate particles, and the organic filler Qc contains at least one polymer having any one of the functional groups C—O, C—Cl, C—F, C—N, C—Si, and Si—O.

[0144] In this way, by providing the light-reflecting portions Q in the resin material layer J, it is possible to achieve the function of radiative cooling as well as the function of solar radiation reflection by the resin material layer J. If the solar radiation reflection function of the light-reflecting portions Q is sufficiently high, the light-reflecting layer B can be omitted.

[0145] 22 and 23 , when a glue layer N connecting the resin material layer J and the protective layer D is provided between the resin material layer J and the protective layer D, the light-reflecting portion Q may be formed on the glue layer N. Suitable adhesives or pressure-sensitive adhesives for use in the glue layer include urethane-based, acrylic-based, and ethylene vinyl acetate-based adhesives. In other words, adhesives (pressure-sensitive adhesives) used in the glue layer N include, for example, urethane-based adhesives (pressure-sensitive adhesives), acrylic-based adhesives (pressure-sensitive adhesives), and EVA (ethylene vinyl acetate)-based adhesives (pressure-sensitive adhesives), and those with high transparency to sunlight are used. Incidentally, the thickness of the glue layer N is, for example, about 10 μm.

[0146] Incidentally, the composite cooling material W shown in Figures 20 to 23 has a configuration equivalent to that of the composite cooling material W shown in Figure 8, but when the light reflecting portion Q is formed in the resin material layer J, the composite cooling material W having the configuration shown in Figures 6, 7 and 9 can be applied.

[0147] By forming the light-reflecting portion Q in the resin material layer J, when the cooling layer CP is viewed from the side where the radiation surface H exists, the light-reflecting portion Q formed in the transparent resin material layer J is seen, and due to the light scattering effect of the light-reflecting portion Q, the color of the composite cooling material W when viewed from the side where the radiation surface H exists becomes white, thereby improving the aesthetic appearance.

[0148] Furthermore, by forming the light reflecting portions Q in the glue layer N connecting the resin material layer J and the protective layer D, when the cooling layer CP is viewed from the side where the radiation surface H is present, the light reflecting portions Q mixed in the glue layer N can be seen through the transparent resin material layer J. Therefore, due to the light scattering effect of the light reflecting portions Q, the color of the composite cooling material W when viewed from the side where the radiation surface H is present appears white, thereby improving the aesthetic appearance. The light reflecting portions Q may be formed in both the resin material layer J and the glue layer N.

[0149] Incidentally, when the light reflecting portion Q is formed in the resin material layer J using an inorganic filler Qb or an organic filler Qc, both the front and back surfaces of the resin material layer J become uneven. When the back surface of the resin material layer J becomes uneven, it is desirable to position an adhesive layer N between the resin material layer J and the protective layer D. In other words, even if the back surface of the resin material layer J is uneven, the adhesive layer N (bonding layer) is positioned between the resin material layer J and the protective layer D, so that the resin material layer J and the protective layer D can be properly bonded. When the back surface of the resin material layer J becomes uneven, the resin material layer J and the protective layer D 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 protective layer D by radiating plasma.

[0150] [Regarding Filler Mixing in Protective Layer] Incidentally, if a filler (at least one of an inorganic filler and an organic filler) is mixed into the protective layer D, the back surface of the protective layer D that contacts the light reflecting layer B becomes uneven, which causes the surface of the light reflecting layer B to deform into an uneven shape, and therefore it is necessary to avoid mixing a filler into the protective layer D. In other words, if the surface of the light reflecting layer B deforms into an uneven shape, it will not be possible to properly reflect light, and as a result, it will not be possible to properly perform radiative cooling.

[0151] The experimental results regarding this point will be described with reference to Fig. 24. In Fig. 24, "directly forming an Ag layer on a light diffusion layer" means that a silver (Ag) film is formed by vapor deposition or the like on the surface of an infrared radiation layer A (resin material layer J) that has filler mixed therein or has embossed irregularities on the Ag layer side, which is the light reflection layer B, to form a light reflection layer B. Furthermore, "a light diffusion layer on a mirror-finished Ag layer" means that the upper surface of the Ag layer that is the light reflection layer B is formed into a mirror-finished surface, and that the upper surface of the Ag layer, a protective layer D, and an infrared radiation layer A (resin material layer J) that has filler mixed therein or has embossed irregularities are laminated on top of the Ag layer.

[0152] As shown in Figure 24, in the case of "forming an Ag layer directly on the light diffusion layer," the surface of the light reflection layer B becomes uneven, resulting in a significant drop in light reflectance, but in the case of "forming a light diffusion layer on mirror-like Ag," the surface of the light reflection layer B is maintained in a mirror-like state, resulting in an appropriate light reflectance.

[0153] 25, 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 structure, glare from the radiation surface H can be suppressed when the radiation surface H is viewed.

[0154] In other words, the resin material layer J of the cooling layer CP shown in Figures 6 to 9 is flat on both the front and back sides and is configured so that no light-reflecting portions Q are mixed in. In such a configuration, the radiation surface H is mirror-like, so when you look at the radiation surface H, you will feel glare, but by providing the light-reflecting portions Q, this glare can be suppressed.

[0155] The front and back surfaces of the resin material layer J can be made uneven by embossing, scratching the surface, etc. Even if the back surface of the resin material layer J is uneven, the resin material layer J and the protective layer D can be properly bonded together by placing an adhesive layer N between them.

[0156] Other Embodiments Other embodiments are listed below: (1) In the above embodiment, the protective layer D is provided, but the protective layer D may be omitted.

[0157] (2) In the above embodiment, the cooling layer CP has a first optical characteristic of a solar reflectance of 80% or more and a second optical characteristic of an average emissivity of 80% or more, which is the wavelength average of the emissivity of infrared light from 8 μm to 14 μm. However, without being limited to this configuration, the cooling layer CP may have only the first optical characteristic. Furthermore, the cooling layer CP may be configured such that the resin material layer J does not have the second optical characteristic and includes a light-reflecting portion Q, but does not include a light-reflecting layer B. Furthermore, the cooling layer CP may be configured from a resin material layer J that does not have the second optical characteristic and a light-reflecting layer B. In this case, the resin material layer J may or may not include a light-reflecting portion Q.

[0158] (3) In the above embodiment, the resin material layer J constituting the infrared radiation layer A is shown to include a plurality of granular light-reflecting portions Q that reflect light. However, the light-reflecting portions Q do not necessarily have to be provided. Furthermore, the light-reflecting portions Q are shown to include bubbles Qa, inorganic fillers Qb, and organic fillers Qc. However, the present invention is not limited to such a configuration, and the light-reflecting portions Q may include at least one of bubbles Qa, inorganic fillers Qb, and organic fillers Qc. Furthermore, although the particle diameter of the light-reflecting portions Q is shown to be 1 nm or more and 300 μm or less, the light-reflecting portions Q may include light-reflecting portions Q having a particle diameter other than these.

[0159] (4) The light reflecting portion Q is made of silicon dioxide (SiO ２ ), titanium oxide (TiO ２ ), aluminum oxide (Al ２ O ３ ), magnesium oxide (MgO), calcium carbonate (CaCO ３ In particular, the photocatalytic layer may be formed using an inorganic material such as titanium oxide (TiO) of about 200 nm, which has no photocatalytic activity. ２ Titanium oxide (TiO ２) may be coated with at least one of alumina, silica, and zirconia. By doing so, the light reflecting portion Q can be appropriately made to have no photocatalytic activity, which makes it easier to suppress deterioration of the resin material layer J.

[0160] In addition, 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.

[0161] The present disclosure can be used for a composite cooling material that can improve usability.

[0162] A: Infrared radiation layer B: Light reflection layer E: Magnetic material layer H: Radiation surface J: Resin material layer Q: Light reflection portion Q2: Inorganic filler Q3: Organic filler

Claims

1. A composite cooling material comprising: a magnetic material layer containing a magnetic material; and a cooling layer provided on the outer surface of the magnetic material layer, wherein the cooling layer has a first optical property of a solar reflectance of 80% or more.

2. The composite cooling material according to claim 1, wherein the cooling layer is configured to include an infrared emitting layer that radiates infrared light from a radiation surface, and a light reflecting layer located on the side of the infrared emitting layer opposite to the side where the radiation surface is present, and the cooling layer has a second optical characteristic of an average emissivity of 80% or more, which is the wavelength average of the emissivity of infrared light from 8 μm to 14 μm, the infrared emitting layer is a resin material layer made of polyvinyl chloride resin or vinylidene chloride resin adjusted to a thickness such that it emits thermal radiation energy in the 8 μm to 14 μm wavelength band greater than the absorbed solar light energy, the light reflecting layer comprises silver or a silver alloy, and the cooling layer and the magnetic material layer are connected by a connecting layer containing one or more of polyvinyl chloride resin, vinylidene chloride resin, polyolefin resin, polyester resin, acrylic resin, urethane resin, silicone resin, and rubber resin.

3. The composite cooling material according to claim 1 or 2, wherein the connecting layer contains at least one of polyvinyl chloride resin and polyolefin resin.

4. The composite cooling material according to claim 1 or 2, wherein the magnetic material layer contains at least ferrite and a binder resin and has a thickness of 0.2 mm or more and 2.0 mm or less.

5. A composite cooling material as described in claim 1 or 2, wherein the cooling layer comprises an infrared emitting layer that emits infrared light from an emitting surface, and the infrared emitting layer comprises a plurality of granular light reflecting portions that reflect light.

6. The composite cooling material according to claim 5, wherein the particle size of the light reflecting portion is 1 nm or more and 300 μm or less.

7. The composite cooling material according to claim 6, wherein the light reflecting portion is porous.

8. The composite cooling material according to claim 6, wherein the light reflecting portion includes at least one of an inorganic filler and an organic filler, the inorganic filler includes at least one of glass microbeads, ceramic microbeads, silicon oxide particles, silicon carbide particles, silicon nitride particles, barium sulfate particles, and calcium carbonate particles, and the organic filler includes at least one of polymers having any one of functional groups selected from C-O, C-Cl, C-F, C-N, C-Si, and Si-O.

9. The composite cooling material according to claim 1 or 2, wherein the cooling layer contains an inorganic filler, and the inorganic filler contains at least one of glass microbeads, ceramic microbeads, silicon oxide particles, silicon carbide particles, silicon nitride particles, barium sulfate particles, and calcium carbonate particles.

10. The composite cooling material according to claim 2, wherein the film thickness of the resin material layer is adjusted to a thickness that provides light absorption characteristics such that the wavelength average light absorptance at wavelengths of 0.4 μm to 0.5 μm is 13% or less, the wavelength average light absorptance at wavelengths of 0.5 μm to 0.8 μm is 4% or less, the wavelength average light absorptance at wavelengths of 0.8 μm to 1.5 μm is within 1%, and the wavelength average light absorptance at wavelengths of 1.5 μm to 2.5 μm is 40% or less.

11. The composite cooling material according to claim 2, wherein the light reflective layer has a reflectance of 90% or more for wavelengths between 0.4 μm and 0.5 μm, and a reflectance of 96% or more for wavelengths longer than 0.5 μm.

12. The composite cooling material according to claim 2, wherein the light reflecting layer has a thickness of 50 nm or more.

13. The composite cooling material according to claim 2, wherein the light reflecting layer has a laminated structure of silver or a silver alloy located closer to the resin material layer and aluminum or an aluminum alloy located away from the resin material layer.

Images