JP2021143795A - Radiation cooling type box - Google Patents

Abstract

To provide a radiation cooling type box capable of cooling the inside of a housing for storing goods under a daytime solar environment by a radiation cooling action.SOLUTION: A radiation cooling type box is configured in such a form that a radiation cooling layer CP is attached to the outer surface of a housing E for storing goods, the radiation cooling layer CP comprises an infrared radiation layer A that emits infrared light IR from a radiation surface H, and a light reflection layer B located on the side opposite to the existing side of the radiation surface H in the infrared radiation layer A. The infrared radiation layer A is a resin material layer J whose thickness is adjusted to emit thermal radiation energy larger than absorbed solar energy in the band of wavelength 8 μm to wavelength 14 μm. The light reflection layer B comprises silver or a silver alloy.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radiative cooling type box having a radiative cooling action.

Radiative cooling is a phenomenon in which a substance emits electromagnetic waves such as infrared rays to its surroundings, causing its temperature to drop. By utilizing this phenomenon, for example, a radiative cooling device (radiative cooling layer) that cools the object to be cooled without consuming energy such as electricity can be configured.

As a conventional example of a radiation cooling device (radiation cooling layer), an infrared radiation layer that emits infrared light from a radiation surface and a light reflection layer that is located on the opposite side of the infrared radiation layer from the side where the radiation surface exists. The infrared radiation layer is formed of a single crystal, a polycrystal, a sintered body, or the like of magnesium oxide, and the light reflecting layer is configured to include silver or a silver alloy. There are some (see, for example, Patent Document 1).

That is, in the radiant cooling device (radiant cooling layer), the infrared radiant layer radiates a large amount of thermal radiation energy in the band of wavelength 8 μm to 14 μm, and the light reflecting layer is the light transmitted through the infrared radiant layer (ultraviolet light, Visible light, infrared light) is reflected and radiated from the radiation surface, and the light transmitted through the infrared radiation layer (ultraviolet light, visible light, infrared light) is projected onto the cooling target, and the cooling target is heated. By avoiding this, it is possible to cool the object to be cooled even in a daytime radiant environment.

In addition to the light transmitted through the infrared radiation layer, the light reflection layer also has the effect of reflecting the light emitted from the infrared radiation layer to the existing side of the light reflection layer toward the infrared radiation layer. However, in the following description, it is assumed that the light reflecting layer is provided for the purpose of reflecting the light (ultraviolet light, visible light, infrared light) transmitted through the infrared emitting layer.

JP-A-2019-168174

A housing for storing various items such as a power distribution case for storing electrical equipment for power distribution, a storage battery case for storing storage batteries, an electric case for storing electrical equipment, and a container for storing various items for transportation. In the provided box, it is desired to suppress an increase in the internal temperature of the housing in a daytime solar radiation environment.

That is, for example, when the storage battery case is applied to a combustion battery system, if the temperature of the stored storage battery exceeds 40 ° C., it is necessary to protect the equipment, and measures such as turning off the power or reducing the output are taken. Therefore, it is desired to suppress an increase in the internal temperature of the housing for accommodating the storage battery as much as possible.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide a radiative cooling type box capable of cooling the inside of a housing for storing articles by a radiative cooling action in a daytime solar radiation environment. It is in.

In the radiative cooling type box of the present invention, a radiative cooling layer is attached to the outer surface of the housing for storing articles.
The radiative cooling layer is configured to include an infrared radiating layer that radiates infrared light from the radiating surface and a light reflecting layer that is located on the opposite side of the radiating layer from the existing side of the radiating surface. ,
The infrared radiant layer is a resin material layer adjusted to a thickness that emits thermal radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm.
The light reflecting layer is characterized in that it is provided with silver or a silver alloy.

That is, sunlight incident from the radiation surface of the resin material layer as the infrared radiation layer in the radiative cooling layer passes through the resin material layer and then reflects light on the side opposite to the existing side of the radiation surface of the resin material layer. It is reflected by the layer and escapes from the radiation surface to the outside of the system.
In the description of the present specification, when simply referred to as light, the concept of the light includes ultraviolet light (ultraviolet light), visible light, and infrared light. When these are described in terms of the wavelength of light as an electromagnetic wave, the electromagnetic wave having a wavelength of 10 nm to 20000 nm (electromagnetic wave of 0.01 μm to 20 μm) is included.

Further, the heat transfer (heat input) to the radiative cooling layer is converted into infrared rays by the resin material layer and is released from the radiant surface to the outside of the system.
In this way, the radiative cooling layer reflects the sunlight radiated to the radiative cooling layer, and also transfers heat to the radiative cooling layer (for example, heat transfer from the atmosphere or from a housing in which the radiative cooling layer cools). Heat transfer) can be radiated to the outside of the system as infrared light.

Further, since the resin material layer is adjusted to have a thickness that emits thermal radiation energy larger than the absorbed solar energy in the band of wavelength 8 μm to wavelength 14 μm, sunlight is emitted by a light reflecting layer provided with silver or a silver alloy. The cooling function can be exhibited even in a daytime solar environment while appropriately reflecting the light.

Therefore, even in the daytime solar radiation environment, the housing can be cooled by the radiative cooling layer mounted on the outer surface of the housing for storing articles, and as a result, the inside of the housing in the daytime solar radiation environment. It is possible to suppress the temperature rise of.

By the way, since the resin material layer is formed of a highly flexible resin material, the resin material layer can be made flexible, and the light reflecting layer is formed as, for example, a silver thin film. It is possible to provide flexibility by such means.
Therefore, the radiative cooling layer including the resin material layer and the light reflection layer can be made flexible, and the radiative cooling layer can be satisfactorily mounted while being along the outer surface of the housing.

In short, according to the characteristic configuration of the radiative cooling type box of the present invention, it is possible to provide a radiative cooling type box capable of cooling the inside of the housing for storing articles by a radiative cooling action in a daytime solar radiation environment.

A further characteristic configuration of the radiative cooling type box of the present invention is configured to include a protective layer between the infrared radiating zone and the light reflecting layer.
The protective layer is a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate having a thickness of 17 μm or more and 40 μm or less.

That is, sunlight incident from the radiation surface of the resin material layer as the infrared radiation layer passes through the resin material layer and the protective layer, and then is a light reflection layer on the opposite side of the radiation surface of the resin material layer. It is reflected by and escaped from the radiation surface to the outside of the system.

Further, since the protective layer is formed of a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or an ethylene terephthalate resin having a thickness of 17 μm or more and 40 μm or less. Since it is possible to suppress discoloration of the silver or silver alloy of the light-reflecting layer even in the daytime sunlight environment, it is cooled even in the daytime sunlight environment while appropriately reflecting sunlight in the light-reflecting layer. The function can be exerted accurately.

That is, when the protective layer does not exist, the radicals generated in the resin material layer reach the silver or silver alloy forming the light reflecting layer, and the moisture transmitted through the resin material layer forms the light reflecting layer. When the silver or silver alloy is reached, the silver or silver alloy in the light reflecting layer may be discolored in a short period of time, resulting in a state in which the light reflecting function is not properly exerted. It is possible to prevent the silver or silver alloy of the layer from discoloring in a short period of time.

The explanation will be given about suppressing the discoloration of silver or the silver alloy of the light reflecting layer by the protective layer.
When the protective layer is formed of a polyolefin resin having a thickness of 300 nm or more and a form of 40 μm or less, the polyolefin resin has ultraviolet rays in the entire wavelength range of ultraviolet rays having a wavelength of 0.3 μm to 0.4 μm. Since it is a synthetic resin having a light absorption rate of 10% or less, the protective layer is less likely to be deteriorated by absorption of ultraviolet rays.

Since the thickness of the polyolefin-based resin forming the protective layer is 300 nm or more, the radicals generated in the resin material layer are blocked from reaching the silver or silver alloy forming the light-reflecting layer, and also. It exerts a good blocking function such as blocking the moisture transmitted through the resin material layer from reaching the silver or silver alloy forming the light reflecting layer, and discolors the silver or silver alloy forming the light reflecting layer. Can be suppressed.

That is, the protective layer formed of the polyolefin resin deteriorates while forming radicals on the surface side away from the reflective layer due to the absorption of ultraviolet rays, but since the thickness is 300 nm or more, the formed radicals. Does not reach the light-reflecting layer, and even if it deteriorates while forming radicals, the progress of deterioration is slow due to low absorption of ultraviolet rays, so that the above-mentioned blocking function can be used for a long period of time. Will be demonstrated.

When the protective layer is formed of an ethylene terephthalate resin having a thickness of 17 μm or more and a form of 40 μm or less, the ethylene terephthalate resin has a wavelength of 0.3 μm to 0.4 μm as compared with the polyolefin resin. Although it is a synthetic resin having a high light absorption rate of ultraviolet rays in the wavelength range of ultraviolet rays, since the thickness is 17 μm or more, the radicals generated in the resin material layer reach the silver or silver alloy forming the light reflecting layer. In addition, the protective layer exhibits a blocking function such as blocking the moisture transmitted through the resin material layer from reaching the silver or silver alloy forming the light reflecting layer for a long period of time. It is possible to suppress discoloration of the silver or silver alloy forming the above.

That is, the protective layer formed of the ethylene terephthalate resin deteriorates while forming radicals on the surface side away from the reflective layer due to the absorption of ultraviolet rays, but it is formed because the thickness is 17 μm or more. The radicals do not reach the reflective layer, and even if they deteriorate while forming radicals, the thickness is 17 μm or more, so that the above-mentioned blocking function is exhibited for a long period of time.

When the protective layer is formed of a polyolefin resin and an ethylene terephthalate resin, the reason for setting the upper limit of the thickness is to prevent the protective layer from exhibiting heat insulating properties that do not contribute to radiative cooling as much as possible. .. In other words, the thicker the protective layer, the more heat insulating properties that do not contribute to radiative cooling. Therefore, the upper limit of the thickness will be set.

In short, according to a further characteristic configuration of the radiative cooling box of the present invention, the radiative cooling box capable of satisfactorily cooling the inside of the housing while suppressing discoloration of the silver or silver alloy of the light reflecting layer in a short period of time. Can be provided.

A further characteristic configuration of the radiative cooling box of the present invention is that the radiative cooling layer is attached to the outer surface of the housing with an adhesive or adhesive connecting layer having a thickness of 5 μm or more and 100 μm or less. At the point.

That is, the outer surface of the housing formed of a metal material or the like may have irregularities of several μm level instead of a mirror surface, but the connection of an adhesive or adhesive having a thickness of 5 μm or more and 100 μm or less. By mounting the radiant cooling layer on the outer surface of the housing as a layer, it is possible to prevent the unevenness of the outer surface of the housing from being reflected on the light reflecting layer even when the outer surface of the housing has irregularities. Therefore, the light reflecting layer can be maintained in a flat state.

That is, when the unevenness of the outer surface of the housing is reflected on the light reflecting layer, the light scattering caused by the unevenness of the outer surface of the housing lowers the reflectance of the light reflecting layer, and the light is absorbed. However, by maintaining the light-reflecting layer in a flat state, it is possible to suppress a decrease in the reflectance of the light-reflecting layer.

Incidentally, the reason for setting the upper limit of the thickness of the connecting layer is to prevent the connecting layer from exhibiting the heat insulating property between the radiative cooling layer and the housing as much as possible. In other words, the thicker the connection layer, the more heat insulating it becomes. Therefore, in order to avoid the heat insulating property between the radiative cooling layer and the housing as much as possible, the upper limit of the thickness is set. become.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, it is possible to suppress a decrease in the reflectance of the light reflecting layer.

A further characteristic configuration of the radiative cooling type box of the present invention is that the radiative cooling layer is mounted on an outer surface portion of the outer surface of the housing excluding the bottom surface portion.

That is, the bottom surface portion on the outer surface of the housing faces the ground surface or the like that does not contribute to the radiative cooling action, but by mounting the radiative cooling layer on the outer surface portion excluding the bottom surface portion on the outer surface of the housing, the housing The housing can be cooled more satisfactorily while effectively using the outer surface of the body as a surface for radiative cooling.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the housing can be cooled more satisfactorily.

A further characteristic configuration of the radiative cooling type box of the present invention is that the radiant surface in the radiative cooling layer is formed in an uneven shape.

That is, the surface area of the radiating surface can be increased by forming the radiating surface in an uneven shape, and as a result, the radiative cooling layer can be cooled by wind to improve the cooling function.

In particular, when the housing is a housing that forms a container for storing various items for transportation, the truck or railroad vehicle travels when the container is loaded and transported on the truck or railroad vehicle. Along with this, the cooling function can be improved by ventilating the radial surface.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the cooling function can be improved.

A further characteristic configuration of the radiative cooling type box of the present invention is that an infrared absorbing layer is mounted on the inner surface of the housing.

That is, since the infrared absorption layer is mounted on the inner surface of the housing, the heat inside the housing can be cooled well by appropriately absorbing the heat inside the housing and transferring it to the radiative cooling layer. It can be carried out.

That is, when the housing is made of a metal such as stainless steel, it is difficult to transfer the heat inside the housing to the radiative cooling layer, such as the housing reflecting infrared rays from the inside. Even in such a case, the inside of the housing can be cooled well.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the inside of the housing can be satisfactorily cooled.

A further characteristic configuration of the radiative cooling type box of the present invention is that the light reflecting layer has a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectance of 96% or more of a long wave from a wavelength of 0.5 μm. There is a certain point.

That is, the sunlight spectrum exists from a wavelength of 0.3 μm to 4 μm, and the intensity increases as the wavelength increases from 0.4 μm, and the intensity increases particularly from the wavelength of 0.5 μm to the wavelength of 2.5 μm.
When the light reflecting layer has a reflectance of 90% or more from a wavelength of 0.4 μm to 0.5 μm and a reflectance of a long wave from a wavelength of 0.5 μm of 96% or more, the light reflecting layer is subjected to sunlight. It absorbs less than about 5% of energy.

As a result, the solar energy absorbed by the light-reflecting layer ^{can be reduced to about 50 W / m 2} or less in the middle of the south in summer, and radiative cooling by the resin material layer can be performed satisfactorily.
In this specification, the spectrum of sunlight is defined as AM1.5G unless otherwise specified.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, it is possible to suppress the absorption of solar energy by the light reflecting layer and satisfactorily perform radiative cooling by the resin material layer.

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

The wavelength average of the light absorption rate of the wavelength of 0.4 μm to 0.5 μm means the average value of the light absorption rate for each wavelength in the range of 0.4 μm to 0.5 μm, and the wavelength is 0.5 μm. The same applies to the wavelength average of the light absorption rate from 0.8 μm to the wavelength average, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm. Is. Further, other similar descriptions including the emissivity also mean the same average value, and the same applies hereinafter in the present specification.

That is, the light absorption rate and the emissivity (light emissivity) of the resin material layer change depending on the thickness. Therefore, it is necessary to adjust the thickness of the resin material layer so as not to absorb sunlight as much as possible and to emit large heat radiation in the wavelength band of the so-called atmospheric window region (the region of light wavelength of 8 μm to 20 μm).

Specifically, from the viewpoint of the light absorption rate (light absorption characteristic) of sunlight in the resin material layer, the wavelength average of the light absorption rate of the wavelengths of 0.4 μm to 0.5 μm is 13% or less, and the wavelength is 0.5 μm. The wavelength average of the light absorption rate of 0.8 μm is 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm is within 1%, and 1.5 μm to 2.5 μm. It is necessary that the wavelength average of the light absorption rate up to is 40% or less. Regarding the light absorption rate from 2.5 μm to 4 μm, the wavelength average may be 100% or less.
When such a light absorption rate is distributed, the light absorption rate of sunlight is 10% or less, and the energy is 100 W or less.

That is, the light absorption rate of sunlight increases as the film thickness of the resin material layer is increased. When the resin material layer to a thick film, approximately 1 becomes the emissivity of the atmospheric windows, heat radiation to release the universe that time becomes 160 W / ^{m 2} from 125W / ^{m 2.}
As described above, the sunlight absorption in the light reflecting layer ^{is preferably 50 W / m 2} or less.
Therefore, if the sum of the sunlight absorption in the resin material layer and the light reflecting layer is 150 W / m ² or less and the atmospheric condition is good, cooling proceeds. As the resin material layer, it is preferable to use a resin material layer having a small absorption rate near the peak value of the sunlight spectrum as described above.

Further, from the viewpoint of the emissivity (thermal radiation characteristic) of emitting infrared light of the resin material layer, the wavelength average of the emissivity having a wavelength of 8 μm to 14 μm needs to be 40% or more.
^{That is, in order for the heat radiation of sunlight of about 50 W / m 2} absorbed by the light reflection layer to be emitted from the resin material layer into space, it is necessary for the resin material layer to emit more heat radiation.
For example, when the outside air temperature is 30 ° C., the maximum thermal radiation of an atmospheric window having a wavelength of 8 μm to 14 μm is 200 W / m ² (calculated assuming an emissivity of 1). This value can be obtained in fine weather, such as in high mountains, where the air is thin and well-dried. In lowlands, the thickness of the atmosphere is thicker than that of high mountains, so the wavelength band of the windows of the atmosphere becomes narrower and the transmittance decreases. By the way, this is called "the window of the atmosphere becomes narrower".

In addition, the environment in which the radiative cooling device is actually used may be humid, and even in that case, the window of the atmosphere becomes narrow. The thermal radiation generated in the window area of the atmosphere when used in lowlands ^{is estimated to be 160 W / m 2} at 30 ° C. in good condition (calculated as emissivity 1).
Also, as is often the case in Japan, when there is haze in the sky or when smog is present, the atmospheric window becomes even narrower, and the radiation to space is about ^{125 W / m 2.}

In view of these circumstances, the wavelength average of the emissivity of 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the window zone of the atmosphere is 50 W / m ² or more) before it can be used in the lowlands of the mid-latitude band.
Therefore, by adjusting the thickness of the resin material layer so as to be within the above-mentioned optical specification range, the heat output from the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and the daytime solar radiation It will be possible to radiatively cool outdoors even in the environment.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the heat output from the window of the atmosphere is larger than the heat input due to the absorption of sunlight, and the radiative cooling can be performed outdoors even in a solar radiation environment. ..

A further characteristic configuration of the radiant cooling type box of the present invention is that the resin material forming the resin material layer has a carbon-fluorine bond, a siloxane bond, a carbon-chlorine bond, a carbon-oxygen bond, an ether bond, an ester bond, and benzene. The point is that it is selected from resins having at least one of the rings.

That is, as the resin material forming the resin material layer, carbon-fluorine bond (CF), siloxane bond (Si—O—Si), carbon-chlorine bond (C—Cl), carbon-oxygen bond (CO). ), An ether bond (R-COO-R), an ester bond (COC), or a colorless resin material having at least one of a benzene ring can be used.

According to Kirchhoff's law, the emissivity (ε) and the light absorption rate (A) are equal. The light absorption rate (A) can be obtained from the absorption coefficient (α) by the following equation 1.
A = 1-exp (−αt) ... (Equation 1) t is the film thickness.
That is, when the thickness of the resin material layer is increased, a large amount of heat radiation can be obtained in a wavelength band having a large absorption coefficient. In the case of radiative cooling outdoors, it is preferable to use a material having a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere. Further, in order to suppress the absorption of sunlight, it is preferable to use a material having no absorption coefficient or a small material in the wavelength range of 0.3 μm to 4 μm, particularly 0.4 μm to 2.5 μm. As can be seen from the relational expression between the absorption coefficient and the light absorption rate of the above formula 1, the light absorption rate (emissivity) changes depending on the film thickness of the resin material layer.

In order to lower the temperature from the surrounding atmosphere by radiative cooling in a solar radiation environment, the resin material that forms the resin material layer has a large absorption coefficient in the wavelength band of the window of the atmosphere and the absorption coefficient in the wavelength band of sunlight. If you choose a material that has almost no sunlight, by adjusting the thickness of the resin material layer, it will hardly absorb sunlight, but it will emit more heat radiation from the windows of the atmosphere, that is, the output by radiative cooling rather than the input of sunlight. A larger state can be created.

The absorption spectrum of the resin material forming the resin material layer will be described.
Regarding the carbon-fluorine bond (CF), _{the absorption coefficient due to CHF and CF 2} spreads widely over a wide band from the wavelength of 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm. At the same time, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient at wavelengths of 0.3 μm to 2.5 μm, which have large energies.

As a resin material having a CF bond,
Polytetrafluoroethylene (PTFE), a completely fluorinated resin,
Polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), which are partially fluorinated resins,
Perfluoroalkoxy alkane resin (PFA), which is a fluororesin copolymer,
Ethylene tetrafluoride / propylene hexafluoride copolymer (FEP),
Ethylene / ethylene tetrafluoride copolymer (ETFE),
Ethylene / chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

The binding energies of CC bond, CH bond, and CF bond of the basic structural part represented by polyvinylidene fluoride (PVDF) are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to a wavelength of 0.275 μm, a wavelength of 0.278 μm, and a wavelength of 0.246 μm, respectively, and absorb light on a wavelength side shorter than these wavelengths.
Since the sunlight spectrum has only long waves having a wavelength of 0.300 μm, when a fluororesin is used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.
In addition, ultraviolet rays have a wavelength on the shorter wavelength side than 0.400 μm, visible rays have a wavelength of 0.400 μm to 0.800 μm, near infrared rays have a wavelength of 0.800 μm to 3 μm, and mid-infrared rays have a wavelength of 3 μm. The range is from 8 μm, and far infrared rays are in the range on the longer wavelength side than the wavelength of 8 μm.

Examples of the resin material having a siloxane bond (Si—O—Si) include silicone rubber and silicone resin. In the resin, a large absorption coefficient due to expansion and contraction of the C—Si bond appears broadly around a wavelength of 13.3 μm, and an absorption coefficient due to the out-of-plane variation angle (pitch) of _{CSiH 2 has a wavelength of 10 μm.} It appears broad in the center, and the absorption coefficient due to the in-plane in-plane variation (scissors) of _{CSiH 2 appears small near a wavelength of 8 μm.} Thus, it has a large absorption coefficient in the window of the atmosphere. In the ultraviolet region, the binding energy of Si—O—Si in the main chain is 4.60 eV, which corresponds to a wavelength of 0.269 μm and absorbs light on a wavelength side shorter than this wavelength. Since the sunlight spectrum has only waves longer than the wavelength of 0.300 μm, when a siloxane bond is used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.

Regarding the carbon-chlorine bond (C-Cl), the absorption coefficient due to C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Further, as a resin material having a carbon-chlorine bond (C-Cl), polyvinyl chloride (PVC) can be mentioned, but in the case of polyvinyl chloride, the C of the alkene contained in the main chain is affected by the electron suction of chlorine. The absorption coefficient derived from the eccentric vibration of −H appears around the wavelength of 10 μm. That is, it is possible to emit a large amount of heat radiation in the wavelength band of the window of the atmosphere. The binding energy of carbon and chlorine of alkene is 3.28 eV, its wavelength corresponds to 0.378 μm, and it absorbs light on the shorter wavelength side than this wavelength. That is, it absorbs the ultraviolet rays of sunlight, but has almost no absorption in the visible region.

The ether bond (R-COO-R) and ester bond (C-OC) have an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, with respect to the carbon-oxygen bond contained in the ester bond and the ether bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm.
When the benzene ring is introduced into the side chain of the hydrocarbon resin, absorption widely appears from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.
Resins having these bonds include polymethylmethacrylate resin, ethylene terephthalate resin, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, and polybutylene naphthalate. For example, the binding energy of the CC bond of methyl methacrylate is 3.93 eV, which corresponds to a wavelength of 0.315 μm and absorbs sunlight having a wavelength shorter than this wavelength, but has almost no absorption in the visible region.

If the resin material forming the resin material layer has the above-mentioned radiation coefficient and absorption rate characteristics, the resin material layer may be a single-layer film of one type of resin material or a multilayer film of a plurality of types of resin materials. A single-layer film of a resin material in which a plurality of types are blended or a multilayer film of a resin material in which a plurality of types are blended may be used. The blend also includes copolymers such as alternating copolymers, random copolymers, block copolymers, and graft copolymers, and modified products in which side chains are replaced.

In short, according to a further characteristic configuration of the radiative cooling box of the present invention, the radiative cooling layer can create a state in which the output by radiative cooling is larger than the input of sunlight.

A further characteristic configuration of the radiative cooling type box of the present invention is that the main component of the resin material forming the resin material layer is siloxane.
The point is that the thickness of the resin material layer is 1 μm or more.

That is, as can be seen from A = 1-exp (−αt) in the above formula 1, the light absorption rate (emissivity) changes depending on the thickness t. The light absorption rate (emissivity) of the resin material needs to be thick enough to have a large absorption coefficient in the window of the atmosphere.
In the case of a resin material whose main component is a siloxane bond (Si—O—Si), if the film thickness is 1 μm or more, the radiant intensity in the window of the atmosphere becomes large, and the output by radiative cooling is higher than the input of sunlight. A larger state can be created.

In short, according to a further characteristic configuration of the radiative cooling type box of the present invention, when the main component of the resin material forming the resin material layer is siloxane, the radiative cooling layer outputs by radiative cooling rather than the input of sunlight. Can create a larger state.

A further characteristic configuration of the radiative cooling type box of the present invention is that the thickness of the resin material layer is 10 μm or more.

That is, carbon-fluorine bond (CF), carbon-chlorine bond (C-Cl), carbon-oxygen bond (CO), ester bond (R-COO-R), ether bond (COC). ), In the case of a resin material whose main component is one of the benzene rings, if there is a film thickness of 10 μm or more, the radiant intensity in the window of the atmosphere becomes large, and the output by radiant cooling is higher than the input of sunlight. You can create a big state.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the resin material forming the resin material layer is carbon-fluorine bond (CF), carbon-chlorine bond (C-Cl), carbon-. In the case of a resin material whose main component is an oxygen bond (CO), an ester bond (R-COO-R), an ether bond (COC), or a benzene ring, the radiative cooling layer is sunlight. The output by radiative cooling can create a larger state than the input of.

A further characteristic configuration of the radiative cooling type box of the present invention is that the thickness of the resin material layer is 20 mm or less.

That is, the thermal radiation of the atmospheric window of the resin material forming the resin material layer is generated within a range of about 100 μm from the material surface.
That is, even if the thickness of the resin material is increased, the thickness that contributes to radiative cooling does not change, and the remaining thickness has the effect of insulating the cold heat after radiative cooling. If a resin material layer that ideally does not absorb sunlight at all is formed, sunlight is absorbed only by the light reflecting layer of the radiative cooling device.

The thermal conductivity of the resin material is generally about 0.2 W / m · K, and when the thickness of the resin material layer exceeds 20 mm, the cooling surface (resin material layer in the light reflecting layer) is calculated in consideration of this thermal conductivity. The temperature of the surface opposite to the side where the plastic exists) rises. Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of the resin material is generally about 0.2 W / m · K, so if the thickness is 20 mm or more, the heat radiation of the resin material layer Due to (radiant cooling), the housing to be cooled on the cooling surface cannot be cooled, and the housing is heated by the sunlight, so that the film thickness cannot be 20 mm or more.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the housing can be appropriately cooled.

A further characteristic configuration of the radiative cooling type box of the present invention is that the resin material forming the resin material layer is fluororesin or silicone rubber.

That is, a fluororesin whose main component is a carbon-fluorine bond (CF), that is, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyfluorovinylidene (PVDF), and polyvinyl fluoride (PVF). ), Perfluoroalkoxy alkane resin (PFA), and ethylene tetrafluoride / propylene hexafluoride copolymer (FEPP) have almost no light absorption in the ultraviolet light region, visible light, and near infrared region of the sunlight spectrum.

Further, a resin having a siloxane bond (Si—O—Si) as a main chain and a small side chain molecular weight, that is, silicone rubber, has an ultraviolet light region, visible light, and near infrared region of the sunlight spectrum, like a fluororesin. Has almost no light absorption.
The thermal conductivity of the fluororesin and the silicone rubber is 0.2 W / m · K, and in view of this point, these resins exhibit a radiative cooling function even if the thickness is increased to 20 mm.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, when the resin material of the resin material layer is fluororesin or silicone rubber, the radiative cooling layer can appropriately exert the radiative cooling function. ..

A further characteristic configuration of the radiation-cooled box of the present invention is that the resin material forming the resin material layer has at least one carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, or benzene ring. A resin having a hydrocarbon as a main chain, or a silicone resin having two or more carbon atoms in a side chain hydrocarbon.
The point is that the thickness of the resin material layer is 500 μm or less.

That is, the resin material forming the resin material layer is a carbon-chlorine bond (CF), a carbon-oxygen bond (CO), an ester bond (R-COO-R), and an ether bond (COC). ), When the resin has a hydrocarbon as the main chain having one or more of the benzene rings, or when the side chain hydrocarbon is a silicone resin having two or more carbon atoms. In addition to the absorption of ultraviolet rays by covalently bonded electrons, absorption based on vibration such as bending angle and expansion and contraction of the bond appears in the near infrared region.

Specifically, the _{absorption by the reference sound of the transition of CH 3} , CH ₂ , and CH to the first excited state is changed from 1.6 μm to 1.7 μm in wavelength, 1.65 μm to 1.75 μm in wavelength, and 1.7 μm in wavelength, respectively. appear. Further, the _{absorption of the combined sound of CH 3} , CH ₂ , and CH by the reference sound appears at a wavelength of 1.35 μm, a wavelength of 1.38 μm, and a wavelength of 1.43 μm, respectively. Further, _{the overtones of the transition of CH 2} and CH to the second excited state appear around the wavelength of 1.24 μm, respectively. The reference sound of the angle change and expansion / contraction of the CH bond is distributed over a wide band from the wavelength of 2 μm to 2.5 μm. Further, _{when it has a structural formula such as R 1-} CO _2- R ₂ , there is a large light absorption around a wavelength of 1.9 μm.

For example, polymethylmethacrylate resin, ethylene terephthalate resin, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polyvinyl chloride are _{caused by CH 3} , CH ₂ , and CH in the near infrared region. It shows similar light absorption characteristics. When these resin materials are thickened to a thickness of 20 mm specified from the viewpoint of thermal conductivity, they are heated by absorbing near infrared rays contained in sunlight. Therefore, when these resin materials are used, the thickness needs to be 500 μm or less.

In short, according to a further characteristic configuration of the radiated cooling box of the present invention, the resin material is a hydrocarbon having at least one of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring. Absorption of near infrared rays can be suppressed in the case of a resin having hydrogen as a main chain or a silicone resin having two or more carbon atoms in a hydrocarbon in a side chain.

A further characteristic configuration of the radiation-cooled box of the present invention is that the resin material forming the resin material layer is a blend of a resin containing a carbon-fluorine bond and a siloxane bond and a resin having a hydrocarbon as a main chain. The point is that the thickness of the resin material layer is 500 μm or less.

That is, the resin material forming the resin material layer is a blend of a resin having a carbon-fluorine bond (CF) or a siloxane bond (Si—O—Si) as a main chain and a resin having a hydrocarbon as a main chain. In the case of the prepared resin material, light absorption in the near infrared region due to _{CH, CH 2} , CH _3, etc. appears depending on the ratio of the resin having the blended hydrocarbon as the main chain. When the carbon-fluorine bond or the siloxane bond is the main component, the light absorption in the near infrared region due to the hydrocarbon becomes small, so that the thickness can be increased to the upper limit of 20 mm from the viewpoint of thermal conductivity. However, when the blended hydrocarbon resin is the main component, the thickness needs to be 500 μm or less.

For blends of fluororesin or silicone rubber and hydrocarbons, those in which the side chains of fluororesin or silicone rubber are replaced with hydrocarbons, alternating copolymers of fluorine monomers and silicone monomers and hydrocarbon monomers, random copolymers, etc. Block copolymers and graft copolymers are also included. Examples of the alternating copolymer of the fluorine monomer and the hydrocarbon monomer include fluoroethylene vinyl ester (FEVE), fluoroolefin-acrylic acid ester copolymer, ethylene / tetrafluoroethylene copolymer (ETFE), and ethylene. Chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

Light absorption in the near infrared region due to _{CH, CH 2} , CH _3, etc. appears depending on the molecular weight and proportion of the hydrocarbon side chain to be substituted.
When the monomer introduced as a side chain or copolymer is a small molecule, or when the density of the introduced monomer is small, the light absorption in the near infrared region due to hydrocarbons becomes small, so from the viewpoint of thermal conductivity. It can be thickened up to the limit of 20 mm in.
When introducing a high molecular weight hydrocarbon as a side chain of a fluororesin or a silicone rubber or a monomer to be copolymerized, the thickness of the resin needs to be 500 μm or less.

In short, according to a further characteristic configuration of the radiative cooling type box of the present invention, when the resin material is a blend of a resin containing a carbon-fluorine bond and a siloxane bond and a resin having a hydrocarbon as a main chain, it is close. The absorption of infrared rays can be suppressed.

A further characteristic configuration of the radiative cooling type box of the present invention is that the resin material forming the resin material layer is a fluororesin.
The point is that the thickness of the resin material layer is 300 μm or less.

That is, from the viewpoint of practical use, the radiative cooling layer should have a thin resin material layer. The thermal conductivity of resin materials is generally lower than that of metals and glass. In order to effectively cool the object to be cooled, the film thickness of the resin material layer should be the minimum necessary. The thicker the thickness of the resin material layer, the larger the heat radiation of the window of the atmosphere, and when the thickness exceeds a certain thickness, the heat radiation energy of the window of the atmosphere is saturated.

The film thickness of the saturated resin material layer depends on the resin material, but in the case of fluororesin, about 300 μm is sufficient for saturation. Therefore, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness of the resin material layer to 300 μm or less rather than 500 μm.
Incidentally, although the heat radiation is not saturated, sufficient heat radiation can be obtained in the window region of the atmosphere even if the thickness is about 100 μm. The thinner the thickness, the higher the thermal transmission rate and the more effectively the temperature of the object to be cooled can be lowered. Therefore, for example, in the case of a fluororesin, the thickness may be about 100 μm or less.

Further, in the case of fluororesin, the absorption coefficient derived from the carbon-silicon bond, carbon-chlorine bond, carbon-oxygen bond, ester bond, and ether bond is larger than the absorption coefficient caused by the CF bond. Naturally, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm, but if the film thickness is further reduced to increase the thermal conductivity, a larger radiative cooling effect can be expected.
Incidentally, as an example of the fluororesin, polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF) can be preferably used.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the radiative cooling effect can be improved when the resin material is a fluororesin.

A further characteristic configuration of the radiative cooling type box of the present invention is that the resin material forming the resin material layer has one or more carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, or benzene ring. It is a resin material that has
The point is that the thickness of the resin material layer is 50 μm or less.

That is, in the case of a resin material containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, the thermal radiation energy in the window of the atmosphere is saturated even if the thickness is 100 μm. Sufficient thermal radiation can be obtained in the window region of the atmosphere even with a thickness of 50 μm.
The thinner the resin material, the higher the thermal transmission rate and the more effectively the temperature of the object to be cooled can be lowered. Therefore, a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring. In the case of, if the thickness is 50 μm or less, the heat insulating property becomes small and the object to be cooled can be effectively cooled.

The effect of thinning is other than lowering the heat insulation and making it easier to transfer cold heat. It carbon - chlorine bond, a carbon - oxygen bond, an ester bond, exhibits a resin having an ether bond, a CH, CH _2, CH ₃ of the light absorption in the near-infrared region from the suppression of the near infrared region. If it is made thinner, the sunlight absorption due to these can be reduced, so that the cooling capacity of the radiative cooling device is increased.
From the above viewpoint, in the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, a thickness of 50 μm or less can more effectively produce a radiative cooling effect in sunlight. ..

In short, according to a further characteristic configuration of the radiative cooling box of the present invention, the radiative cooling effect in a resin material having one or more of carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, and benzene ring. Can be improved.

A further characteristic configuration of the radiative cooling type box of the present invention is that the resin material forming the resin material layer is a resin material having a carbon-silicon bond.
The point is that the thickness of the resin material layer is 10 μm or less.

That is, in the case of a resin material having a carbon-silicon bond, heat radiation is completely saturated in the window region of the atmosphere even at a thickness of 50 μm, and sufficient heat radiation can be obtained in the window region of the atmosphere even at a thickness of 10 μm. The thinner the resin material, the higher the thermal transmission rate and the more effectively the temperature of the object to be cooled can be lowered. Therefore, in the case of a resin material containing a carbon-silicon bond, if the thickness is 10 μm or less, the heat insulating property is improved. It becomes smaller and the object to be cooled can be cooled effectively. If it is made thinner, the sunlight absorption can be reduced, so that the cooling capacity of the radiative cooling type box is increased.

From the above viewpoint, in the case of a resin material containing a carbon-silicon bond, if the thickness is 10 μm or less, the radiative cooling effect can be obtained more effectively in the sunlight.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, the radiative cooling effect can be improved in the resin material having a carbon-silicon bond.

A further characteristic configuration of the radiative cooling type box of the present invention is that the resin material forming the resin material layer is a vinyl chloride resin or a vinylidene chloride resin.
The thickness of the resin material layer is 100 μm or less and 10 μm or more.

That is, the vinyl chloride resin (polyvinyl chloride) or vinylidene chloride resin (polyvinylidene chloride) having a thickness of 100 μm or less and 10 μm or more can obtain sufficient thermal radiation in the window region of the atmosphere.
Vinyl chloride resin or vinylidene chloride resin is slightly inferior to fluororesins that can obtain large heat radiation in the window region of the atmosphere, but is superior to other resin materials such as silicone rubber and considerably better than fluororesins. Since it is inexpensive, it is effective for inexpensively constructing a radiant cooling type box whose temperature is lower than the ambient temperature in direct sunlight.

Further, since the thin-film vinyl chloride resin or vinylidene chloride resin is soft, it is not easily scratched even if it comes into contact with another object, so that it can be maintained in a beautiful state for a long period of time. By the way, since the thin-film fluororesin is hard, it is easily scratched by contact with other objects, and it is difficult to maintain a beautiful state.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, it is possible to inexpensively obtain a radiative cooling layer whose temperature is lower than the ambient temperature and is not easily scratched in direct sunlight.

A further characteristic configuration of the radiative cooling type box of the present invention is that the light reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more.

That is, the light reflecting layer has the above-mentioned reflectance characteristic, that is, the reflectance characteristic of a wavelength of 0.4 μm to 0.5 μm is 90% or more, and the reflectance of a long wave from a wavelength of 0.5 μm is 96% or more. In order to make the light-reflecting layer, the reflective material on the radiation surface side of the light-reflecting layer needs to be silver or a silver alloy.
When sunlight is reflected with only silver or a silver alloy having the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, it is possible to accurately suppress the absorption of solar energy by the light reflecting layer and satisfactorily perform radiative cooling by the resin material layer.

A further characteristic configuration of the radiant cooling type box of the present invention is a laminated structure in which the light reflecting layer is a silver or silver alloy located adjacent to the protective layer and an aluminum or aluminum alloy located on the side away from the protective layer. It is in the point that it is.

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

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 having appropriate reflectance characteristics.
In other words, it is appropriate to make the light-reflecting layer a laminated structure of silver or silver alloy and aluminum or aluminum alloy while thinning the expensive silver or silver alloy to reduce the cost of the light-reflecting layer. It is possible to reduce the cost of the light-reflecting layer while having a good reflectance characteristic.

In short, according to the further characteristic configuration of the radiative cooling type box of the present invention, it is possible to reduce the cost of the light reflecting layer while having appropriate reflectance characteristics.

It is a figure explaining the basic structure of a radiative cooling type box. It is a figure which shows the relationship between the absorption coefficient of a resin material and a wavelength band. It is a figure which shows the relationship between the light absorption rate of a resin material, and a wavelength. It is a figure which shows the emissivity spectrum of a silicone rubber. It is a figure which shows the emissivity spectrum of PFA. It is a figure which shows the emissivity spectrum of a vinyl chloride resin. It is a figure which shows the emissivity spectrum of an ethylene terephthalate resin. It is a figure which shows the emissivity spectrum of an olefin metamorphic material. It is a figure which shows the relationship between the temperature of a radiation surface and the temperature of a light reflection layer. It is a figure which shows the light absorption spectrum of the silicone rubber and the perfluoroalkoxy alkane resin. It is a figure which shows the light absorption spectrum of the ethylene terephthalate resin. It is a figure which shows the light reflectance spectrum of the light-reflecting layer based on silver. It is a figure which shows the emissivity spectrum of fluoroethylene vinyl ether. It is a figure which shows the emissivity spectrum of vinylidene chloride resin. It is a table which shows the experimental result. It is a figure which shows the specific structure of a radiative cooling type box. It is a figure which shows the specific structure of a radiative cooling type box. It is a figure which shows the specific structure of a radiative cooling type box. It is a figure which shows the specific structure of a radiative cooling type box. It is a figure which shows the relationship between the light absorption rate of a resin material, and a wavelength. It is a figure which shows the relationship between the light transmittance and the wavelength of polyethylene. It is a figure explaining the structure for a test. It is a figure which shows the test result when the protective layer is polyethylene. It is a figure which shows the test result when the protective layer is ultraviolet-absorbing acrylic. It is a figure which shows the emissivity spectrum of polyethylene. It is a figure explaining another structure of a radiative cooling layer. This is an explanation showing the installation state of the connection layer. It is explanatory drawing which shows the outer surface state of a housing. It is a figure which shows the experimental state of a radiative cooling type box. It is a graph which shows the experimental result. It is a figure which shows the experimental state of a radiative cooling type box. It is a figure which shows the experimental result. It is a figure which shows the experimental state of a radiative cooling type box. It is a graph which shows the experimental result. It is a graph which shows the experimental result. It is a graph which shows the experimental result. It is a figure explaining another installation form of a radiative cooling layer. It is a figure which shows the truck of a van body. It is a figure which shows the container. It is a figure which shows the structure which formed the radiative cooling layer in an uneven shape. It is a figure which shows the case of transporting a container by a truck. It is a figure which shows the specific example of the concavo-convex shape of a radiative cooling layer. It is a figure which shows the specific example of the concavo-convex shape of a radiative cooling layer. It is a figure explaining the structure which mixed the filler in the resin material layer. It is a figure explaining the structure which made the front and back of the resin material layer uneven.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
[Basic configuration of radiative cooling box]
As shown in FIG. 1, in the radiative cooling type box W, a film-shaped radiative cooling layer CP is attached to the outer surface of the housing E for storing articles, and the radiative cooling action of the radiative cooling layer CP causes the housing E to have a radiative cooling action. It is configured to cool the inside.
The illustrated housing E is made of metal, for example, stainless steel, is formed in a rectangular parallelepiped shape, and the radiative cooling layer CP is an outer surface portion (that is, an upper surface portion and 4) excluding the bottom surface portion on the outer surface of the housing E. It is attached to one side surface).

An infrared absorption layer Z is mounted on the inner surface of the housing E. The infrared absorption layer Z is provided in order to satisfactorily cool the inside of the housing E by appropriately absorbing the heat inside the housing E and transferring it to the radiative cooling layer CP. ..
That is, when the housing E is made of a metal such as stainless steel, it is difficult to transfer the heat inside the housing E to the radiative cooling layer CP, such as the housing E reflecting infrared rays from the inside. However, even in such a case, the inside of the housing E can be cooled well.
The infrared absorption layer Z is formed by applying a resin material to the inner surface of the housing E or by applying a resin material mixed with a filler for increasing the absorption rate to the inner surface of the housing E.
When the housing E is made of resin, the infrared absorption layer Z is unnecessary.

The radiation cooling layer CP includes an infrared radiation layer A that emits infrared light IR from the radiation surface H, a light reflection layer B that is located on the opposite side of the infrared radiation layer A from the side where the radiation surface H exists. The protective layer D between the infrared radiation layer A and the light reflection layer B is provided in a laminated state and is formed in a film shape.
That is, the radiative cooling layer CP is configured as a radiative cooling film.
Then, the radiative cooling layer CP is attached to the housing E with the light reflecting layer B positioned adjacent to the housing E.

The light reflecting layer B reflects light L such as sunlight transmitted through the infrared emitting layer A and the protective layer D, and its reflection characteristics are such that the reflectance at a wavelength of 400 nm to 500 nm is 90% or more and the wavelength is 500 nm. The reflectance of longer waves is 96% or more.
As shown in FIG. 10, the sunlight spectrum exists from a wavelength of 300 nm to 4000 nm, and the intensity increases as the wavelength increases from 400 nm, and the intensity increases particularly from a wavelength of 500 nm to a wavelength of 1800 nm.

In the present embodiment, the light L includes ultraviolet light (ultraviolet rays), visible light, and infrared light, and when these are described in terms of the wavelength of light as an electromagnetic wave, the wavelength is 10 nm to 20000 nm (0). Includes electromagnetic waves of 0.01 μm to 20 μm). Incidentally, in this document, it is assumed that the wavelength range of ultraviolet light (ultraviolet light) is between 300 nm and 400 nm.

The light reflecting layer B exhibits a reflection characteristic of 90% or more from a wavelength of 400 nm to 500 nm, and a reflectance of a long wave from a wavelength of 500 nm is 96% or more. The solar energy absorbed by the reflective layer B can be suppressed to 5% or less, that is, the solar energy absorbed in the south and middle of summer can be reduced to about 50 W.

The light reflecting layer B is composed of silver or a silver alloy, or is configured as a laminated structure of a silver or silver alloy located adjacent to the protective layer D and an aluminum or aluminum alloy located on the side away from the protective layer D. It is flexible, and the details will be described later.

The infrared radiating zone A is configured as a resin material layer J whose thickness is adjusted to emit heat radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm, and the details thereof will be described later. do.

Therefore, the radiation cooling layer CP reflects a part of the light L incident on the radiation cooling layer CP on the radiation surface H of the infrared radiation layer A, and the light L incident on the radiation cooling layer CP. The light (sunlight, etc.) transmitted through the resin material layer J and the protective layer D is reflected by the light reflecting layer B and is configured to escape from the radiating surface H to the outside.

Then, heat input to the radiative cooling layer CP from the housing E located on the side opposite to the existing side of the resin material layer J in the light reflecting layer B (for example, heat input by heat conduction from the housing E) is applied. The housing E is configured to be cooled by being converted into infrared light IR by the resin material layer J and radiated.

That is, the radiative cooling layer CP reflects the light L irradiated to the radiative cooling layer CP, and heat transfer to the radiative cooling layer CP (for example, heat transfer from the atmosphere or heat transfer from the housing E). ) Is configured to radiate to the outside as infrared light IR.
Further, the resin material layer J, the protective layer D, and the light reflecting layer B have flexibility, so that the radiative cooling layer CP (radiative cooling film) has flexibility.

[Overview of resin material layer]
The light absorption rate 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 as not to absorb sunlight as much as possible and to emit a large amount of heat radiation in the wavelength band of the so-called atmospheric window (the band having a wavelength of 8 μm to 14 μm).

Specifically, from the viewpoint of the light absorption rate of sunlight, the thickness of the resin material layer J is such that the wavelength average of the light absorption rate with a wavelength of 0.4 μm to 0.5 μm is 13% or less, and the wavelength is from 0.5 μm. The wavelength average of the light absorption rate of 0.8 μm is 4% or less, the wavelength average of the light absorption rate from 0.8 μm to 1.5 μm is within 1%, and the wavelength is 1.5 μm to 2.5 μm. It is necessary to adjust the thickness so that the wavelength average of the light absorption rates up to is 40% or less and the wavelength average of the light absorption rates from 2.5 μm to 4 μm is 100% or less.
In the case of such an absorption rate distribution, the light absorption rate of sunlight is 10% or less, and the energy is 100 W or less.

As will be described later, the light absorption rate of the resin material increases as the film thickness of the resin material increases. When the resin material to thick, approximately 1 becomes the emissivity of the atmospheric windows, heat radiation to release the universe that time becomes 160 W / ^{m 2} from 125W / ^{m 2.} The sunlight absorption in the protective layer D and the light reflecting layer B is 50 W / m ² or less. The sum of sunlight absorption in the resin material layer J, the protective layer D, and the light reflecting layer B is 150 W / m ² or less, and cooling proceeds if the atmospheric condition is good. As the resin material forming the resin material layer J, it is preferable to use a resin material having a small light absorption rate near the peak value of the sunlight spectrum as described above.

Further, the thickness of the resin material layer J needs to be adjusted from the viewpoint of infrared radiation (heat radiation) so that the wavelength average of the emissivity of 8 μm to 14 μm is 40% or more.
^{In order to release the heat energy of sunlight of about 50 W / m 2} absorbed by the protective layer D and the light reflecting layer B from the resin material layer J to the space from the heat radiation of the resin material layer J, more heat radiation is required. Needs to be released by the resin material layer J.
For example, when the outside air temperature is 30 ° C., the maximum thermal radiation of an atmospheric window of 8 μm to 14 μm is 200 W / m ² (calculated assuming an emissivity of 1). This value can be obtained in fine weather, such as in high mountains, where the air is thin and well-dried. In lowlands, the thickness of the atmosphere is thicker than that of high mountains, so the wavelength band of the windows of the atmosphere becomes narrower and the transmittance decreases. By the way, this is called "the window of the atmosphere becomes narrower".

In addition, the environment in which the radiative cooling layer CP (radiative cooling film) is actually used may be humid, and even in that case, the window of the atmosphere becomes narrow. The thermal radiation generated in the window area of the atmosphere when used in lowlands ^{is estimated to be 160 W / m 2} at 30 ° C. in good condition (calculated as emissivity 1). Also, as is often the case in Japan, when there is haze in the sky or when smog is present, the atmospheric window becomes even narrower, and the radiation to space is about ^{125 W / m 2.}
In view of these circumstances, the wavelength average of the emissivity of 8 μm to 14 μm must be 40% or more (heat radiation intensity in the window zone of the atmosphere is 50 W / m ² ) before it can be used in lowlands in the mid-latitude zone.

Therefore, if the thickness of the resin material layer J is adjusted so as to fall within the optically specified range in consideration of the above items, the heat output from the atmospheric window becomes larger than the heat input due to the light absorption of sunlight, and the solar radiation environment. It will be possible to radiatively cool outdoors even underneath.

[Details of resin material]
The resin material includes carbon-fluorine bond (CF), siloxane bond (Si-O-Si), carbon-chlorine bond (C-Cl), carbon-oxygen bond (CO), and ester bond (R-). A colorless resin material containing COO-R), an ether bond (COC bond), and a benzene ring can be used.
For each resin material (excluding carbon-oxygen bonds), the wavelength range having an absorption coefficient in the wavelength band of the window of the atmosphere is shown in FIG.

According to Kirchhoff's law, the emissivity (ε) and the light absorption rate (A) are equal. The light absorption rate can be obtained from the absorption coefficient (α) by a relational expression of A = 1-exp (−αt) (hereinafter, referred to as a light absorption rate relational expression). In addition, t is a film thickness.
That is, when the film thickness of the resin material layer J is adjusted, a large amount of heat radiation can be obtained in a wavelength band having a large absorption coefficient. In the case of radiative cooling outdoors, it is preferable to use a material having a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere.
Further, in order to suppress the absorption of sunlight, it is preferable to use a material having no absorption coefficient or a small material in the wavelength range of 0.3 μm to 4 μm, particularly 0.4 μm to 2.5 μm. As can be seen from the relational expression between the absorption coefficient and the absorptivity, the light absorptivity (emissivity) changes depending on the film thickness of the resin material.

In order to lower the temperature from the surrounding atmosphere by radiant cooling in a solar radiation environment, select a material that has a large absorption coefficient in the wavelength band of the window of the atmosphere and almost no absorption coefficient in the wavelength band of sunlight. By adjusting the thickness, it absorbs almost no sunlight, but it emits a lot of heat radiation from the windows of the atmosphere, that is, it can create a state where the output by radiant cooling is larger than the input of sunlight.

Regarding the carbon-fluorine bond (CF), _{the absorption coefficient due to CHF and CF 2} spreads widely over a wide band from the wavelength of 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm. At the same time, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient at wavelengths of 0.3 μm to 2.5 μm, which have a large energy intensity.

As a resin material having a carbon-fluorine bond (CF),
Polytetrafluoroethylene (PTFE), a completely fluorinated resin,
Polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF), which are partially fluorinated resins,
Perfluoroalkoxy alkane resin (PFA), which is a fluororesin copolymer,
Ethylene tetrafluoride / propylene hexafluoride copolymer (FEP),
Ethylene / ethylene tetrafluoride copolymer (ETFE),
Ethylene / chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

Examples of the resin material having a siloxane bond (Si—O—Si) include silicone rubber and silicone resin.
In the resin, a large absorption coefficient due to expansion and contraction of the C—Si bond appears broadly around a wavelength of 13.3 μm, and an absorption coefficient due to the out-of-plane variation angle (pitch) of _{CSiH 2 has a wavelength of 10 μm.} It appears broad in the center, and the absorption coefficient due to the in-plane in-plane variation (scissors) of _{CSiH 2 appears small near a wavelength of 8 μm.}

Regarding the carbon-chlorine bond (C-Cl), the absorption coefficient due to C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Examples of the resin material include vinyl chloride resin (PVC) and vinylidene chloride resin (PVDC). In the case of vinyl chloride resin, the change in CH of the alkene contained in the main chain is affected by the electron suction of chlorine. The absorption coefficient derived from the angular vibration appears around the wavelength of 10 μm.

The ester bond (R-COO-R) and the ether bond (C-OC bond) have an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, with respect to the carbon-oxygen bond contained in the ester bond and the ether bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm.
When the benzene ring is introduced into the side chain of the hydrocarbon resin, absorption widely appears from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.

Examples of the resin having these bonds include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, ethylene naphthalate resin, and butylene naphthalate resin.

[Consideration of light absorption]
Consider the light absorption in the ultraviolet-visible region of the resin material having the above-mentioned bonds and functional groups, that is, the absorption of sunlight. The origin of absorption of visible light from ultraviolet light is the transition of electrons that contribute to the bond. Absorption in this wavelength range can be found by calculating the binding energy.
First, let us consider the wavelength at which the absorption coefficient occurs in the ultraviolet to visible region of a resin material having a carbon-fluorine bond (CF). The binding energies of CC bond, CH bond, and CF bond of the basic structural part represented by polyvinylidene fluoride (PVDF) are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to a wavelength of 0.275 μm, a wavelength of 0.278 μm, and a wavelength of 0.246 μm, respectively, and absorb light of these wavelengths.

Since the sunlight spectrum has only long waves having a wavelength of 0.300 μm, when a fluororesin is used, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight. The definition of ultraviolet rays is on the shorter wavelength side than the wavelength of 0.400 μm, the definition of visible light is on the wavelength range of 0.400 μm to 0.800 μm, the near infrared rays are in the range of 0.800 μm to 3 μm, and the mid infrared rays are 3 μm to 8 μm. The range is defined as far infrared rays having a wavelength longer than 8 μm.

The absorptivity spectrum of PFA (perfluoroalkoxy alkane resin) having a thickness of 50 μm in the ultraviolet to visible region is shown in FIG. 3, and it can be seen that it has almost no absorptivity. A slight increase in the absorptivity spectrum is observed on the wavelength side shorter than 0.4 μm, but this increase only shows the effect of scattering of the sample used for the measurement, and the absorptivity actually increases. Not done.

Regarding the ultraviolet region of the siloxane bond (Si—O—Si), the binding energy of Si—O—Si in the main chain is 4.60 eV, which corresponds to a wavelength of 269 nm. Since the sunlight spectrum has only waves longer than the wavelength of 0.300 μm, when the majority of siloxane bonds are present, it hardly absorbs ultraviolet rays, visible rays, and near infrared rays of sunlight.

The absorptivity spectrum of the silicone rubber having a thickness of 100 μm in the ultraviolet to visible region is shown in FIG. 3, and it can be seen that the silicone rubber has almost no absorptivity. A slight increase in the absorptivity spectrum is observed on the wavelength side shorter than the wavelength of 0.4 μm, but this increase only shows the effect of scattering of the sample used for the measurement, and the absorptivity is actually Not increasing.

Regarding the carbon-chlorine bond (C-Cl), the carbon-chlorine bond energy of Alken is 3.28 eV and its wavelength is 0.378 μm, so it absorbs a lot of ultraviolet rays in sunlight, but in the visible range. Has little absorption.
The absorptivity spectrum of a vinyl chloride resin having a thickness of 100 μm in the ultraviolet to visible region is shown in FIG. 3, and the light absorption becomes larger on the shorter wavelength side than the wavelength of 0.38 μm.
The absorptivity spectrum of the vinylidene chloride resin having a thickness of 100 μm in the ultraviolet to visible region is shown in FIG. 3, and a slight increase in the absorptivity spectrum is observed on the wavelength side shorter than the wavelength of 0.4 μm.

Resins having an ester bond (R-COO-R), an ether bond (C-OC bond), and a benzene ring include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, and ethylene na. There are phthalate resin and butylene naphthalate resin. For example, the binding energy of the CC bond of acrylic is 3.93 eV, which absorbs sunlight having a wavelength shorter than 0.315 μm, but has almost no absorption in the visible region.

As an example of a resin material having these bonds and functional groups, FIG. 3 shows an absorption rate spectrum in the ultraviolet to visible region of a methyl methacrylate resin having a thickness of 5 mm. The methyl methacrylate resin exemplified is generally commercially available, and contains a benzotriazole-based ultraviolet absorber.
Since the plate is as thick as 5 mm, the wavelength having a small absorption coefficient also becomes large, and the light absorption becomes larger on the short wave side than the long wave of 0.38 μm than the wavelength of 0.315.

As an example of the resin material having these bonds and functional groups, the absorption rate spectrum in the ultraviolet to visible region of an ethylene terephthalate resin having a thickness of 40 μm is shown in FIG.
As shown in the figure, the absorptivity increases as the wavelength approaches 0.315 μm, and the absorptivity sharply increases at a wavelength of 0.315 μm. As the thickness of the ethylene terephthalate resin is increased, the absorption rate due to the absorption edge derived from the CC bond increases on the long wave side of the wavelength of 0.315 μm, which is the same as that of the commercially available methyl methacrylate resin. In addition, the absorption rate in ultraviolet rays increases.

If the resin material layer J uses a resin material having the above-mentioned radiation rate (light radiation rate) and light absorption rate characteristics, it is a single-layer film of one type of resin material or a multilayer film of a plurality of types of resin materials. , A single-layer film of a resin material in which a plurality of types of resin materials are blended, or a multilayer film of a resin material in which a plurality of types of resin materials are blended may be used.
The blend also includes copolymers such as alternating copolymers, random copolymers, block copolymers, and graft copolymers, and modified products in which side chains are replaced.

[Radance rate of silicone rubber]
FIG. 4 shows an emissivity spectrum of a silicone rubber having a siloxane bond in an atmospheric window.
From the silicone rubber, a large absorption coefficient due to the expansion and contraction of the C—Si bond appears broadly around the wavelength of 13.3 μm, and the absorption coefficient due to the out-of-plane variation (pitch) of _{CSiH 2 is at a wavelength of 10 μm.} The absorption coefficient due to the in-plane in-plane variation (scissors) of _{CSiH 2 appears small in the vicinity of the wavelength of 8 μm.}
Due to this effect, the wavelength average of the emissivity with a thickness of 1 μm is 80% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

Incidentally, FIG. 4 also shows an emission spectrum when quartz having a thickness of 1 μm, which is an inorganic material, is present on silver. Quartz has only a narrow band of radiation peaks between wavelengths of 8 μm and 14 μm when the thickness is 1 μm.
When this thermal radiation is averaged in the wavelength range of 8 μm to 14 μm, the radiation rate of 8 μm to 14 μm is 32%, and it is difficult to show the radiative cooling performance.

The radiative cooling layer CP (radiative cooling film) of the present invention using the resin material layer J can obtain radiative cooling performance even in an infrared radiative layer A thinner than the conventional technique in which an inorganic material is used as the light reflecting layer B. That is, when the infrared radiating zone A is formed of quartz or Tempax glass, which is an inorganic material, the radiative cooling performance cannot be obtained when the infrared radiating zone A has a thickness of 1 μm, but the resin material layer J is used. In the radiative cooling layer CP of the present invention, the resin material layer J exhibits radiative cooling performance even when the film thickness is 1 μm.

[PFA emissivity]
FIG. 5 shows the emissivity of perfluoroalkoxy alkane resin (PFA) in an atmospheric window as a typical example of a resin having a carbon-fluorine bond. The absorption coefficient due to CHF and CF ₂ is widely spread over a wide band from 8 μm to 14 μm, which is the window of the atmosphere, and the absorption coefficient is particularly large at 8.6 μm.
Due to this effect, the wavelength average of the emissivity with a thickness of 10 μm is 45% at wavelengths of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Radance rate of vinyl chloride resin and vinylidene chloride resin]
FIG. 6 shows the emissivity of vinyl chloride resin (PVC) in an atmospheric window as a typical example of a resin having a carbon-chlorine bond. In addition, FIG. 14 shows the emissivity of vinylidene chloride resin (PVDC) in the atmospheric window.
Regarding the carbon-chlorine bond, the absorption coefficient due to C-Cl expansion and contraction vibration appears in a wide band with a half width of 1 μm or more centered on a wavelength of 12 μm.
Further, in the case of a vinyl chloride resin, the absorption coefficient derived from the angular vibration of CH of the alkene contained in the main chain appears around the wavelength of 10 μm due to the influence of electron suction of chlorine. The same applies to vinylidene chloride resin.
Due to these effects, the wavelength average of the emissivity with a thickness of 10 μm is 43% at a wavelength of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Ethylene terephthalate resin]
FIG. 7 shows the emissivity of an ethylene terephthalate resin in an atmospheric window as a typical example of a resin having an ester bond or a benzene ring.
Regarding the ester bond, it has an absorption coefficient from a wavelength of 7.8 μm to 9.9 μm. Further, regarding the carbon-oxygen bond contained in the ester bond, a strong absorption coefficient appears in the wavelength band of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, absorption appears widely from a wavelength of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements due to the influence of the benzene ring.
Due to these effects, the wavelength average of the emissivity with a thickness of 10 μm is 71% at a wavelength of 8 μm to 14 μm, which falls within the regulation that the wavelength average is 40% or more. As shown in the figure, the emissivity in the window region of the atmosphere increases as the film thickness increases.

[Radance of olefin metamorphic material]
FIG. 8 contains a carbon-fluorine bond (CF), a carbon-chlorine bond (C-Cl), an ester bond (R-COO-R), an ether bond (COC bond), and a benzene ring. The radiance spectrum of the olefin-modified material, which is not present and whose main component is benzene, is shown. The sample was prepared by applying an olefin resin on the vapor-deposited silver with a bar coater and drying it.
As shown in the figure, the emissivity in the window region of the atmosphere is small, and due to this effect, the wavelength average of the emissivity with a thickness of 10 μm is 27% at wavelengths of 8 μm to 14 μm, and the wavelength average is 40% or more. not enter.

The emissivity shown is that of an olefin resin modified for application as a bar coater, and in the case of a pure olefin resin, the emissivity in the window region of the atmosphere is even smaller.
As described above, it does not contain carbon-fluorine bond (CF), carbon-chlorine bond (C-Cl), ester bond (R-COO-R), ether bond (COC bond), and benzene ring. And radiative cooling is not possible.

[Temperature of the surface of the light reflecting layer and the resin material layer]
Thermal radiation from the atmospheric window of the resin material layer J is generated near the surface of the resin material.
From FIG. 4, in the case of silicone rubber, if it is thicker than 10 μm, heat radiation in the window region of the atmosphere does not increase. That is, in the case of silicone rubber, most of the heat radiation in the window of the atmosphere is generated in the portion within about 10 μm in depth from the surface, and the radiation in the deeper portion does not come out.

From FIG. 5, in the case of fluororesin, even if the thickness is thicker than 100 μm, there is almost no increase in thermal radiation in the window region of the atmosphere. That is, in the case of fluororesin, heat radiation in the window of the atmosphere is generated in a portion within a depth of about 100 μm from the surface, and radiation in a deeper portion does not come out.
From FIG. 6, in the case of the vinyl chloride resin, even if the thickness is thicker than 100 μm, the increase in thermal radiation in the window region of the atmosphere is almost eliminated. That is, in the case of vinyl chloride resin, heat radiation in the window of the atmosphere is generated in a portion within a depth of about 100 μm from the surface, and radiation in a deeper portion does not come out.
From FIG. 14, it can be seen that the vinylidene chloride resin is similar to the vinyl chloride resin.

From FIG. 7, in the case of the ethylene terephthalate resin, the increase in thermal radiation in the window region of the atmosphere is almost eliminated even if the thickness is thicker than 125 μm. That is, in the case of ethylene terephthalate resin, heat radiation in the window of the atmosphere is generated at a depth of about 100 μm from the surface, and radiation at a deeper part does not come out.

As described above, the heat radiation of the window region of the atmosphere generated from the surface of the resin material is generated in the portion where the depth from the surface is approximately 100 μm or less, and when the thickness of the resin is further increased, the heat radiation is generated. The radiatively cooled cold heat of the radiative cooling layer CP is insulated by the resin material that does not contribute to.
Consider forming a resin material layer J that ideally does not absorb sunlight at all on the light reflecting layer B. In this case, sunlight is absorbed only by the light reflecting layer B of the radiative cooling layer CP.
The thermal conductivity of the resin material is generally about 0.2 W / m / K, and when calculated in consideration of this thermal conductivity, when the thickness of the resin material layer J exceeds 20 mm, the cooling surface (in the light reflecting layer B). The temperature of the surface of the resin material layer J opposite to the existing side) rises.

Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of the resin material is generally about 0.2 W / m / K, so if it exceeds 20 mm as shown in FIG. 9, the light reflecting layer B Is heated by the sunlight, and the housing E installed on the light reflecting layer side is heated. That is, the thickness of the resin material of the radiative cooling layer CP needs to be 20 mm or less.

FIG. 9 is a plot of the surface temperature of the radiative surface H of the radiative cooling layer (radiative cooling film) CP and the temperature of the light reflecting layer B calculated assuming the southern part of a sunny day in western Japan in midsummer. .. The sunlight is AM1.5 and the energy density is ^{1000 W / m 2.} The outside air temperature is 30 ° C., and the radiant energy varies depending on the temperature, but is 100 W at 30 ° C. The calculation is based on the assumption that the resin material layer does not absorb sunlight. Assuming no wind, the convective heat transfer coefficient is 5 W / m ² / K.

[About light absorption rate of silicone rubber, etc.]
FIG. 10 shows the _{light absorption rate with respect to the sunlight spectrum when the thickness of the silicone rubber having CH 3 as} the side chain is 100 μm, and the light absorption rate spectrum with respect to the sunlight spectrum of the perfluoroalkoxy alkane resin having a thickness of 100 μm. .. As described above, it can be seen that both resins have almost no light absorption rate in the ultraviolet region.

Regarding silicone rubber, in the near-infrared region, the light absorption rate increases in the region on the long wave side of the wavelength of 2.35 μm. However, since the intensity of the sunlight spectrum in this wavelength range is weak, the solar energy absorbed is 20 W / m ² even if the light absorption rate on the long wave side from the wavelength of 2.35 μm is 100%.

The perfluoroalkoxy alkane resin has almost no light absorption rate in the wavelength range of 0.3 μm to 2.5 μm, and has light absorption on the wavelength side longer than the wavelength of 2.5 μm. However, even if the film thickness of the resin is increased and the light absorption rate on the wavelength side longer than the wavelength of 2.5 μm becomes 100%, the absorbed solar energy is about 7 W.

As the thickness (film thickness) of the resin material layer J is increased, the emissivity of the window region of the atmosphere becomes approximately 1. That is, in the case of a thick film, the heat radiation that radiates into space at atmospheric window region when used in low-lying becomes 125W / ^{m 2} order of 160 W / ^{m 2} at 30 ° C.. The light absorption in the light reflecting layer B is ^{about 50 W / m 2} as specified above, and the light absorption of the light reflecting layer B and the sunlight absorption when the silicone rubber or the perfluoroalkoxyfluororesin is made into a thick film are added. Even smaller than the thermal radiation radiated into space.
From the above, the maximum film thickness of the silicone rubber and the perfluoroalkoxy fluororesin is 20 mm from the viewpoint of thermal conductivity.

[About light absorption of hydrocarbon resins]
When the resin material forming the resin material layer J is a resin having a hydrocarbon as a main chain having one or more carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, or silicone. When the hydrocarbon is a resin and has two or more carbon atoms in the side chain, absorption based on vibration such as bond angle change and expansion and contraction is observed in the near infrared region in addition to the above-mentioned absorption of ultraviolet rays by covalent bond electrons.

Specifically, the _{absorption by the reference sound of the transition of CH 3} , CH ₂ , and CH to the first excited state is changed from 1.6 μm to 1.7 μm in wavelength, 1.65 μm to 1.75 μm in wavelength, and 1.7 μm in wavelength, respectively. appear. Further, the _{absorption of the combined sound of CH 3} , CH ₂ , and CH by the reference sound appears at a wavelength of 1.35 μm, a wavelength of 1.38 μm, and a wavelength of 1.43 μm, respectively. Further, _{the overtones of the transition of CH 2} and CH to the second excited state appear around the wavelength of 1.24 μm, respectively. The reference sound of the angle change and expansion / contraction of the CH bond is distributed over a wide band from the wavelength of 2 μm to 2.5 μm.

Further, when it has an ester bond (R-COO-R) and an ether bond (COC), there is a large light absorption around a wavelength of 1.9 μm.
According to the above-mentioned light absorption rate relational expression, the light absorption rate due to these becomes smaller and less noticeable when the film thickness of the resin material is thin, but becomes larger when the film thickness is thicker.

FIG. 11 shows the relationship between the light absorption rate and the spectrum of sunlight when the film thickness of the ethylene terephthalate resin having an ester bond and a benzene ring is changed.
As shown in the figure, as the film thickness increases to 25 μm, 125 μm, and 500 μm, the light absorption in the long wave region increases from the wavelength of 1.5 μm caused by the respective vibrations.
Further, not only the long wavelength side but also the light absorption from the ultraviolet region to the visible region is increased. This is due to the spread of the light absorption edge due to the chemical bond.

When the film thickness is thin, the light absorption coefficient increases at the wavelength having the largest absorption coefficient, but when the film thickness is thick, the absorption coefficient with a broad absorption edge and a weak absorption coefficient is based on the above-mentioned light absorption coefficient relational expression. Appears next. As a result, as the film thickness increases, the light absorption from the ultraviolet region to the visible region increases.
Absorption of solar spectrum when a thickness of 25μm is 15W / ^{m 2,} the absorption of the solar spectrum when the absorption of the solar spectrum when the thickness is 125μm is 41W / ^{m 2,} the thickness of 500μm is 88W / It is m ^2.

Since the light absorption of the light reflecting layer B is 50 W / m ² according to the above regulation, when the film thickness is 500 μm, the sum of the sunlight absorption of the ethylene terephthalate resin and the sunlight absorption of the light reflecting layer B is 138 W. It becomes / m ^2. As mentioned above, the maximum value of infrared radiation in the wavelength band of the window of the atmosphere in the lowland summer of Japan is about 160 W on a day when the atmospheric condition is good at 30 ° C., and usually about 125 W.
From the above, when the film thickness of the ethylene terephthalate resin is 500 μm or more, the radiative cooling performance is not exhibited.

The origin of the absorption spectrum in the wavelength band of 1.5 μm to 4 μm is not the functional group but the vibration of the hydrocarbon in the main chain, and if it is a hydrocarbon-based resin, it behaves in the same manner as the ethylene terephthalate resin. In addition, the hydrocarbon resin has light absorption due to chemical bonds in the ultraviolet region, and exhibits the same behavior as the ethylene terephthalate resin from the ultraviolet to the visible.
That is, if it is a hydrocarbon resin, it behaves in the same manner as an ethylene terephthalate resin from a wavelength of 0.3 μm to 4 μm. From the above, the thickness of the hydrocarbon-based resin needs to be thinner than 500 μm.

[About light absorption of blended resin]
When the resin material is a resin material in which a resin having a carbon-fluorine bond or a siloxane bond as a main chain and a resin having a hydrocarbon as the main chain are blended, the resin having the blended hydrocarbon as the main chain is used. Light absorption in the near-infrared region due to _{CH, CH 2} , CH 3, etc. appears according to the ratio of CH, CH _{2, CH 3, and the like.}
When the carbon-fluorine bond or the siloxane bond is the main component, the light absorption in the near infrared region due to the hydrocarbon becomes small, so that the thickness can be increased to the upper limit of 20 mm from the viewpoint of thermal conductivity. However, when the blended hydrocarbon resin is the main component, the thickness needs to be 500 μm or less.

For blends of fluororesin or silicone rubber and hydrocarbons, the side chains of fluororesin or silicone rubber are replaced with hydrocarbons, alternating copolymers of fluoropolymers and silicone monomers and hydrocarbon monomers, and random copolymers. , Block copolymers and graft copolymers are also included. Examples of the alternating copolymer of the fluorine monomer and the hydrocarbon monomer include fluoroethylene vinyl ester (FEVE), fluoroolefin-acrylic acid ester copolymer, ethylene / tetrafluoroethylene copolymer (ETFE), and ethylene. Chlorotrifluoroethylene copolymer (ECTFE) can be mentioned.

Light absorption in the near infrared region due to _{CH, CH 2} , CH _3, etc. appears depending on the molecular weight and proportion of the hydrocarbon side chain to be substituted. When the monomer introduced as a side chain or copolymer is a small molecule, or when the density of the introduced monomer is small, the light absorption in the near infrared region due to hydrocarbons becomes small, so from the viewpoint of thermal conductivity. It can be thickened up to the limit of 20 mm in.
When introducing a high molecular weight hydrocarbon as a side chain of a fluororesin or a silicone rubber or a monomer to be copolymerized, the thickness of the resin needs to be 500 μm or less.

[Thickness of resin material layer]
From the viewpoint of practical use of the radiative cooling layer CP, the thickness of the resin material layer J should be thin. The thermal conductivity of resin materials is generally lower than that of metals and glass. In order to effectively cool the housing E, the film thickness of the resin material layer J should be the minimum necessary. The thicker the thickness of the resin material layer J, the larger the heat radiation of the window of the atmosphere, and when the thickness exceeds a certain thickness, the heat radiation energy of the window of the atmosphere is saturated.

The film thickness to be saturated depends on the resin material, but in the case of fluororesin, about 300 μm is sufficient for saturation. Therefore, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm. Further, although the heat radiation is not saturated, sufficient heat radiation can be obtained in the window region of the atmosphere even if the thickness is about 100 μm. The thinner the thickness, the higher the thermal transmission rate and the more effectively the temperature of the housing E can be lowered. Therefore, in the case of the fluororesin, the thickness should be about 100 μm or less.

The absorption coefficient derived from the carbon-silicon bond, carbon-chlorine bond, carbon-oxygen bond, ester bond, and ether bond is larger than the absorption coefficient caused by the CF bond. Naturally, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm, but if the film thickness is further reduced to increase the thermal conductivity, a larger radiative cooling effect can be expected.
In the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, even if the thickness is 100 μm, it is saturated, and even if the thickness is 50 μm, sufficient heat radiation is emitted in the window region of the atmosphere. can get. The thinner the resin material, the higher the thermal transmission rate and the more effectively the temperature of the housing E can be lowered. Therefore, a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring. In the case of, if the thickness is 50 μm or less, the heat insulating property becomes small and the housing E can be effectively cooled. In the case of a carbon-chlorine bond, the housing E can be effectively cooled if the thickness is 100 μm or less.

The effect of thinning is other than lowering the heat insulation and making it easier to transfer cold heat. It carbon - chlorine bond, a carbon - oxygen bond, an ester bond, exhibits a resin having an ether bond, a CH, CH _2, CH ₃ of the light absorption in the near-infrared region from the suppression of the near infrared region. If it is made thinner, the sunlight absorption due to these can be reduced, so that the cooling capacity of the radiative cooling layer CP is increased.
From the above viewpoint, in the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, a thickness of 50 μm or less can more effectively produce a radiative cooling effect in sunlight. can.

In the case of the carbon-silicon bond, the heat radiation is completely saturated in the window region of the atmosphere even if the thickness is 50 μm, and sufficient heat radiation can be obtained in the window region of the atmosphere even if the thickness is 10 μm. The thinner the resin material layer J, the higher the thermal transmission rate and the more effectively the temperature of the housing E can be lowered. Therefore, in the case of a resin containing a carbon-silicon bond, if the thickness is 10 μm or less, the heat insulating property is improved. Can be reduced and the housing E can be effectively cooled. When it is made thinner, the sunlight absorption can be reduced, so that the cooling capacity of the radiative cooling layer CP is increased.
From the above viewpoint, in the case of a resin containing a carbon-silicon bond, if the thickness is 10 μm or less, the radiative cooling effect can be obtained more effectively in the sunlight.

[Details of 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. 12, if the light reflecting layer B is formed based on silver, the reflectance required for the light reflecting layer B can be obtained.

When reflecting sunlight with only silver or a silver alloy with the above-mentioned reflectance characteristics, a thickness of 50 nm or more is required.
However, in order to provide the light reflecting layer B with flexibility, the thickness needs to be 100 μm or less. If it is thicker than this, it will be difficult to bend.
By the way, as the "silver alloy", an alloy in which any one of copper, palladium, gold, zinc, tin, magnesium, nickel and titanium is added to silver, for example, about 0.4% by mass to 4.5% by mass is added. Can be used. As a specific example, "APC-TR (made of Furuya metal)", which is a silver alloy prepared by adding copper and palladium to silver, can be used.

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

Incidentally, as the "aluminum alloy", an alloy obtained by adding copper, manganese, silicon, magnesium, zinc, carbon steel for machine structure, ittrium, lantern, gadrinium, and terbium to aluminum can be used.

Silver and silver alloys are vulnerable to rain and humidity and need to be protected from them, and their discoloration needs to be suppressed. Therefore, as shown in FIGS. 16 to 19, a protective layer D that protects silver is required in a form adjacent to silver or a silver alloy.
Details of the protective layer D will be described later.

[Experimental results]
Silver is formed on a glass substrate to a thickness of 300 nm, and a silicone rubber having a siloxane bond, a fluoroethylene vinyl ether having a carbon-fluorine bond, an olefin modified product (olefin modified material), and a vinyl chloride resin are placed on the bar coater. The coating was applied while controlling the film thickness, and the radiant cooling performance was measured.
The evaluation of the radiative cooling performance was carried out at an outside air temperature of 35 ° C. in late June, 3 hours after the south, middle, and south, and the temperature (° C.) of the back surface of the substrate was measured after maintaining the substrate with high heat insulation. However, the vinyl chloride resin was carried out when the outside air temperature was 29 ° C. It was evaluated whether or not there was a radiative cooling effect depending on whether the temperature 5 minutes after installation in the jig was lower or higher than the outside air temperature.
The result of the radiative cooling test is shown in FIG.

Incidentally, the emissivity of the window region of the atmosphere of fluoroethylene vinyl ether is as shown in FIG. The radiance of the silicone rubber is as shown in FIG. 4, the radiance of the modified olefin (olefin modified material) is as shown in FIG. 8, and the radiance of the vinyl chloride resin is shown in FIG. It's a street.

In the case of silicone rubber having a siloxane bond, it was found that the radiative cooling ability is exhibited at a thickness of 1 μm or more as expected from theory.
It was found that the fluoroethylene vinyl ether having a carbon-fluorine bond exhibits radiative cooling ability at a film thickness of 5 μm, which is thinner than the theoretically predicted 10 μm. The reason for this is that not only the light absorption of the window of the atmosphere by the carbon-fluorine bond but also the light absorption by the ether bond of vinyl ether is added, and the light absorption rate of the window of the atmosphere is increased as compared with the case of each alone.
The olefin modified product (olefin modified material) does not have a radiative cooling capacity because there is almost no heat radiation in the window region of the atmosphere.

[Specific configuration of radiative cooling box]
In the radiative cooling layer CP, since the resin material forming the resin material layer J and the protective layer D is flexible, if the light reflecting layer B is made into a thin film, the light reflecting layer B can also be made flexible. As a result, the radiative cooling layer CP can be a flexible film (radiative cooling film).

Then, as shown in FIGS. 16 to 19, a film-shaped radiative cooling layer CP (radiative cooling film) is attached to the outer surface of the housing E with the adhesive or adhesive connecting layer S, thereby mounting the housing. The inside of E can be cooled.
Examples of the adhesive or adhesive used for the connection layer S include urethane-based adhesive (adhesive), acrylic-based adhesive (adhesive), EVA (ethylene vinyl acetate) -based adhesive (adhesive), and the like.

Various forms are conceivable for producing the radiative cooling layer CP in the form of a film. For example, it is conceivable to apply the protective layer D and the resin material layer J to the light reflecting layer B produced in the form of a film. Alternatively, it is conceivable to attach the protective layer D and the resin material layer J to the light reflecting layer B produced in the form of a film. Alternatively, a protective layer D is applied or pasted on the resin material layer J produced in the form of a film, and a light reflecting layer is formed on the protective layer D by vapor deposition, sputtering, ion plating, silver mirror reaction, or the like. It is conceivable to produce B.

Specifically, in the radiation cooling layer CP (radiation cooling film) of FIG. 16, when the light reflection layer B is formed as a layer of silver or a silver alloy, or when silver (silver alloy) and aluminum (aluminum alloy) are used. In the case of two layers, the protective layer D is formed on the upper side of the light reflecting layer B, the resin material layer J is formed on the upper part of the protective layer D, and the bottom of the light reflecting layer B is formed. The lower protective layer Ds is also formed on the side.

As a method of producing the radiative cooling layer CP (radiative cooling film) of FIG. 16, the protective layer D, the light reflecting layer B, and the lower protective layer Ds are sequentially coated on the film-shaped resin material layer J and integrated. A method of molding can be adopted.

In the radiation cooling layer CP (radiation cooling film) of FIG. 17, the light reflection layer B is composed of an aluminum layer B1 formed of an aluminum foil functioning as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy. A protective layer D is formed on the upper side of the light reflecting layer B, and a resin material layer J is formed on the upper part of the protective layer D.

As a method of producing the radiative cooling layer CP (radiative cooling film) of FIG. 17, a silver layer B2, a protective layer D, and a resin material layer J are sequentially coated on an aluminum layer B1 made of aluminum foil. A method of integrally molding can be adopted.
As another production method, the resin material layer J is formed in a film shape, the protective layer D and the silver layer B2 are sequentially coated on the film-shaped resin material layer J, and the aluminum layer B1 is a silver layer. A method of pasting on B2 can be adopted.

The radiation cooling layer CP (radiation cooling film) of FIG. 18 is a case where the light reflection layer B is formed as one layer of silver or a silver alloy, or a case where the light reflection layer B is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy). In, a protective layer D is formed on the upper side of the light reflecting layer B, a resin material layer J is formed on the upper part of the protective layer D, and a film layer F such as PET is formed on the lower side of the light reflecting layer B. It was done.

As a method for producing the radiation cooling layer CP (radiation cooling film) in FIG. 18, a light reflecting layer is formed on a film layer F (corresponding to a base material) formed in the form of a PET (ethylene terephthalate resin) or the like. A method can be adopted in which B and the protective layer D are sequentially applied, integrally molded, and the separately formed film-shaped resin material layer J is adhered to the protective layer D with the glue layer N.
The adhesive (adhesive) used in the glue layer N includes, for example, urethane-based adhesive (adhesive), acrylic-based adhesive (adhesive), EVA (ethylene vinyl acetate) -based adhesive (adhesive), and the like. Yes, it is desirable to have high transparency to sunlight.

In the radiation cooling layer CP (radiation cooling film) of FIG. 19, the light reflection layer B is composed of an aluminum layer B1 that functions as aluminum (aluminum alloy) and a silver layer B2 made of silver or a silver alloy (alternative silver). , The aluminum layer B1 is formed on the upper part of the film layer F (corresponding to the base material) formed in the form of a PET (ethylene terephthalate resin) or the like, and the protective layer D is formed on the upper side of the silver layer B2. , The resin material layer J is formed on the upper side of the protective layer D.

As a method of producing the radiative cooling layer CP (radiative cooling film) of FIG. 19, an aluminum layer B1 is applied on the film layer F, the film layer F and the aluminum layer B1 are integrally molded, and separately. The protective layer D and the silver layer B2 are coated on the film-shaped resin material layer J to integrally form the resin material layer J, the protective layer D, and the silver layer B2, and the aluminum layer B1 and the silver layer B2 are glued together. A method of bonding with the layer N can be adopted.
The adhesive (adhesive) used in the glue layer N includes, for example, urethane-based adhesive (adhesive), acrylic-based adhesive (adhesive), EVA (ethylene vinyl acetate) -based adhesive (adhesive), and the like. Yes, it is desirable to have high transparency to sunlight.

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

FIG. 20 shows the ultraviolet absorption rates of polyethylene, vinylidene chloride resin, ethylene terephthalate resin, and vinyl chloride resin.
Further, FIG. 21 shows the light transmittance of polyethylene suitable as a synthetic resin for forming the protective layer D.

Since the radiant cooling layer CP (radiant cooling film) exerts a radiant cooling action not only at night but also in a solar radiation environment, in order to maintain the state in which the light reflection layer B exerts a light reflection function. By protecting the light reflecting layer B with the protective layer D, it is necessary to prevent the silver of the light reflecting layer B from being discolored in a solar radiation environment.

When the protective layer D is formed of a polyolefin resin having a thickness of 300 nm or more and a form of 40 μm or less, the polyolefin resin has a wavelength of 0.3 μm to 0.4 μm in the entire ultraviolet wavelength range. Since the synthetic resin has an ultraviolet light absorption rate of 10% or less, the protective layer D is less likely to be deteriorated by the absorption of ultraviolet rays.

Since the thickness of the polyolefin-based resin forming the protective layer D is 300 nm or more, the radicals generated in the resin material layer J are blocked from reaching the silver or silver alloy forming the light-reflecting layer. In addition, it satisfactorily exerts a blocking function such as blocking the moisture transmitted through the resin material layer J from reaching the silver or silver alloy forming the light reflecting layer B, and the silver forming the light reflecting layer B. Alternatively, discoloration of the silver alloy can be suppressed.

Incidentally, the protective layer D formed of the polyolefin resin deteriorates while forming radicals on the surface side away from the light reflecting layer B due to the absorption of ultraviolet rays, but since the thickness is 300 nm or more, The formed radicals do not reach the light reflecting layer, and even if they deteriorate while forming radicals, the progress of deterioration is slow due to the low absorption of ultraviolet rays. It will be demonstrated over a long period of time.

When the protective layer D is formed of an ethylene terephthalate resin having a thickness of 17 μm or more and a form of 40 μm or less, the ethylene terephthalate resin has a wavelength of 0.3 μm to 0.4 μm as compared with the polyolefin resin. Although it is a synthetic resin having a high light absorption rate of ultraviolet rays in the ultraviolet wavelength range of the above, since the thickness is 17 μm or more, the radicals generated in the resin material layer J form a silver or silver alloy forming the light reflecting layer B. It is intended to satisfactorily exhibit a blocking function for a long period of time, such as blocking the arrival of water and blocking the moisture transmitted through the resin material layer J from reaching the silver or silver alloy forming the light reflecting layer. Therefore, discoloration of the silver or the silver alloy forming the light reflecting layer B can be suppressed.

That is, the protective layer formed of the ethylene terephthalate resin deteriorates while forming radicals on the surface side away from the light reflecting layer B due to the absorption of ultraviolet rays, but since the thickness is 17 μm or more, The formed radicals do not reach the reflective layer, and even if they deteriorate while forming radicals, the thickness is 17 μm or more, so that the above-mentioned blocking function is exhibited for a long period of time.

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

For example, when the ethylene terephthalate resin (PET) is irradiated with ultraviolet rays of high intensity in Osaka, the ester bond of the ethylene terephthalate resin (PET) having a diameter of about 9 nm is cleaved in order from the irradiated surface per day. .. Since the ethylene terephthalate resin (PET) is sufficiently polymerized, the ethylene terephthalate resin (PET) on the cleaved surface does not attack the silver (silver alloy) of the light reflecting layer B, but the ethylene terephthalate resin When the cracked end of (PET) reaches the light reflecting layer B silver (silver alloy), the silver (silver alloy) is discolored.

Therefore, in order to make the protective layer D durable for one year or more when used outdoors, a thickness of about 3 μm is required by integrating 9 nm / day and 365 days. In order to make the ethylene terephthalate resin (PET) of the protective layer D durable for 3 years or more, a thickness of 10 μm or more is required. A thickness of 17 μm or more is required to make it durable for 5 years or more.

When the protective layer D is formed of the polyolefin resin and the ethylene terephthalate resin, the reason for setting the upper limit of the thickness is to prevent the protective layer D from exhibiting heat insulating properties that do not contribute to radiative cooling. be. That is, since the protective layer D exhibits a heat insulating property that does not contribute to radiative cooling as the thickness increases, the protective layer D exhibits a heat insulating property that does not contribute to radiative cooling while exerting a function of protecting the light reflecting layer B. In order to avoid the above, the upper limit of the thickness will be set.

That is, when the protective layer D becomes thick, there is no demerit in preventing the silver (silver alloy) of the light reflecting layer B from being colored, but a problem in radiative cooling occurs. That is, the thicker the material, the better the heat insulating property of the radiative cooling material.
For example, a resin whose main component is polyethylene, which is excellent as a synthetic resin for forming the protective layer D, has a small emissivity in the window of the atmosphere as shown in FIG. 25, and therefore does not contribute to radiative cooling even if it is formed thick. On the contrary, thickening will improve the heat insulation of the radiative cooling material. Next, as the thickness increases, the absorption in the near-infrared region derived from the vibration of the main chain increases, and the effect of increasing the sunlight absorption increases.
Due to these factors, a thick protective layer D is disadvantageous for radiative cooling. From such a viewpoint, the thickness of the protective layer D formed of the polyolefin resin is preferably 5 μm or less, more preferably 1 μm or less.

By the way, as shown in FIG. 18, when the glue layer N is located between the resin material layer J and the protective layer D, radicals are also generated from the glue layer N, but the protective layer D is formed. If the thickness of the polyolefin resin to be formed 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 reach the light reflecting layer B. Can be suppressed for a long period of time.

[Consideration of protective layer]
In order to examine the difference in how silver is colored by the protective layer D, a sample in which the protective layer D without the resin material layer J as the infrared radiation layer A as shown in FIG. 22 is exposed was prepared. , The coloration of silver after being irradiated with simulated sunlight was investigated.
That is, as the protective layer D, two types of a general acrylic resin that absorbs ultraviolet rays (for example, a methyl methacrylate resin mixed with a benzotriazole ultraviolet absorber) and polyethylene are used as a light reflecting layer B with a bar coater. A sample coated on the film layer F (corresponding to the base material) provided with silver was formed, and the function as the protective layer D was examined. The thickness of the applied protective layer D is 10 μm and 1 μm, respectively.
The film layer F (corresponding to the base material) is formed in the form of a film by PET (ethylene terephthalate resin) or the like.

As shown in FIG. 24, when the protective layer D is an acrylic resin that absorbs ultraviolet rays well, the protective layer D is decomposed by ultraviolet rays to form radicals, and silver immediately yellows and does not function as a radiative cooling layer CP. (It absorbs sunlight and rises in temperature when exposed to sunlight like ordinary materials).
The line of 600 h in the figure is a reflectance spectrum after performing a xenon weather test (ultraviolet light energy is 60 W / m ² ) for 600 h (hours) under the conditions of JIS standard 5600-7-7. The 0h line is the reflectance spectrum before the xenon weather test is performed.

As shown in FIG. 23, when the protective layer D is polyethylene having a low light absorption rate of ultraviolet rays, it can be seen that the reflectance does not decrease in the near-infrared region to the visible region. In other words, the resin whose main component is polyethylene (polyolefin resin) hardly absorbs the ultraviolet rays of sunlight that reaches the ground, so it is difficult to form radicals even when exposed to sunlight, so even when exposed to sunlight, it reflects light. Coloring of silver as layer B does not occur.
The line of 600 h in the figure is a reflectance spectrum after performing a xenon weather test (ultraviolet light energy is 60 W / m ² ) for 600 h (hours) under the conditions of JIS standard 5600-7-7. The 0h line is the reflectance spectrum before the xenon weather test is performed.

The reason why the reflectance spectrum in this wavelength band is wavy is the Fabry-Perot resonance of the polyethylene layer. It can be seen that this resonance position is slightly different between the 0h line and the 600h line due to the change in the thickness of the polyethylene layer due to the heat of the xenon weather test. No significant decrease in reflectance is observed in the visible region.

The fluororesin system can also be applied to the material forming the protective layer D from the viewpoint of absorbing ultraviolet rays, but when it is actually formed as the protective layer D, it is colored and deteriorated at the forming stage, so that the material forming the protective layer D is formed. Cannot be used as.
Further, silicone can also be applied to a material for forming the protective layer D from the viewpoint of absorbing ultraviolet rays, but the adhesion to silver (silver alloy) is extremely poor, and it cannot be used as a material for forming the protective layer D.

[Separate configuration of radiative cooling layer]
As shown in FIG. 26, the radiative cooling layer CP includes an anchor layer G on the upper part of the film layer F (corresponding to the base material), and the light reflection layer B, the protective layer D, and the infrared rays are on the upper part of the anchor layer G. It may be configured to include a radiation layer A.
The film layer F (corresponding to the base material) is formed in a film shape by, for example, PET (ethylene terephthalate resin) or the like.

The anchor layer is introduced to strengthen the adhesion between the film layer F and the light reflecting layer B. That is, when silver (Ag) is directly formed on the film layer F, peeling easily occurs. The anchor layer G is preferably composed mainly of acrylic, polyolefin, or urethane, and is mixed with a compound having an isocyanate group or a melamine resin. It is a coating on the part that is not directly exposed to sunlight, and there is no problem even if it is a material that absorbs ultraviolet rays.
As a method of strengthening the adhesion between the film layer F and the light reflecting layer B, there is a method other than inserting the anchor layer G. For example, if the film-forming surface of the film layer F is irradiated with plasma to roughen the surface, the adhesion is enhanced.

[Consideration of connection layer]
When the radiative cooling layer CP is mounted on the outer surface of the housing E, the thickness of the connection layer S is preferably 5 μm or more and 100 μm or less.
That is, the outer surface (surface) of the housing E of the power distribution box installed outdoors or the storage battery box installed outdoors is often not a mirror surface. FIG. 28 shows a schematic view of the outer surface (material surface) of the housing E, which is not a mirror surface. As shown in the illustrated figure, the outer surface (material surface) of the housing E, which is different from the mirror surface, has innumerable scratches and irregularities on the level of several μm.

When innumerable scratches and irregularities are present, light is scattered by these innumerable scratches and irregularities, and the appearance is different from that of a mirror surface. When sunlight is applied to a material surface different from the mirror surface, not only light rays whose interaction with the outer surface (material surface) is reflected at one time, as in the light L of (1), but also ( A light beam that is reflected after multiple interactions with the outer surface (material surface), such as light L in 2), and an infinite number of interactions with the outer surface (material surface), such as light L in (3). Therefore, a light beam that is almost absorbed by the housing E is generated.
When the interaction between the light L and the outer surface (material surface) increases, the light absorption rate increases. For example, if there is a surface with a reflectance of 80% when it is a mirror surface, and it is assumed that the light is reflected twice in the structure on average and the light is emitted to the outside, the reflectance is 64%.

In this way, the reflectance of a material having a surface different from the mirror surface (a surface that scatters light) is always lowered in terms of photoengineering. Then, when the μm-level unevenness existing on the outer surface (material surface) is transferred to the light reflecting layer B (silver layer) of the radiative cooling layer CP, the reflectance is lowered.
Therefore, it is necessary to introduce a structure that prevents the unevenness existing on the outer surface (material surface) from being reflected in the radiative cooling layer CP, and for this purpose, the radiative cooling layer CP is provided in the connecting layer S having a thickness of 5 μm to 100 μm. It is preferable to join it to the outer surface of the housing E.

When the connecting layer S composed of an adhesive or an adhesive is present, the connecting layer S absorbs the unevenness of the outer surface of the housing E, and the light reflecting layer B (silver layer) of the radiative cooling layer CP becomes flat.
When the light reflecting layer B (silver layer) becomes flat, the light L interacts with the light reflecting layer B (silver layer) once on average, and the sunlight reflectance decreases (in other words, the sunlight absorption rate increases). Will be prevented.

The surface roughness of the outer surface (material surface) of the housing E varies widely, but the unevenness of the general outer surface (material surface) is within ± 2.5 μm with respect to the reference line. Therefore, the thickness of the connecting layer S is preferably 5 μm or more.
However, as the thickness of the connection layer S increases, the heat insulating property improves. If the heat insulating property is improved, the cold heat of the radiative cooling layer CP is insulated, which is not good. From this point of view, an unnecessarily thick connection layer S is unnecessary, and a thickness of 100 μm is sufficient.

[Experimental results of radiative cooling box]
FIG. 29 shows a state in which a radiative cooling box W having a radiative cooling layer CP mounted on the outer surface of a rectangular parallelepiped housing E made of stainless steel is placed on the ground 1. In the radiative cooling type box W illustrated, the infrared absorption layer Z is not mounted on the inner surface of the housing E.
FIG. 30 shows the result of measuring the internal temperature of the radiative cooling type box W placed on the ground 1.
In addition, in FIG. 30, the stainless steel rectangular parallelepiped housing E, that is, the change in the internal temperature when the stainless steel box is placed on the ground 1, and the outer surface of the stainless steel rectangular parallelepiped housing E The change in the internal temperature when the box coated with the solar reflective paint, that is, the box using the solar reflective paint is placed on the ground 1, is also described.

When the radiative cooling box W is placed on the ground 1, the ground 1 on which the radiative cooling box W is placed is not exposed to solar radiation. In such a case, the soil stores cold heat at night, and the internal temperature of the radiative cooling box W is unlikely to rise. Therefore, when the radiative cooling box W is placed on the ground 1, cooling is promoted as compared with the gantry method described later, that is, the radiative cooling box W is placed on the gantry 2 (see FIG. 31). ..

In the case of a stainless steel box in the south, the internal temperature is about 7 ° C higher than that of the radiative cooling box W. Further, in the case of a box using a solar reflective paint at the time of south-central time, the internal temperature is about 3 ° C. higher than that of the radiative cooling type box W.
Based on the results of this test, an electrical case for storing electrical equipment, such as a distribution case for storing electrical equipment for distribution and a storage battery case for storing storage batteries, is configured as a radiative cooling box W and placed on the ground 1. If the form is adopted, an increase in the internal temperature can be suppressed.
If the infrared absorption layer Z is mounted on the inner surface of the housing E, the increase in the internal temperature can be further suppressed.

FIG. 31 shows a state in which the radiative cooling type box W is placed on the gantry 2. In the radiative cooling type box W illustrated, the infrared absorption layer Z is not mounted on the inner surface of the housing E.
FIG. 32 shows the results of measuring the internal temperature of the radiative cooling type box W mounted on the gantry 2.
In addition, FIG. 32 shows the change in the internal temperature when the stainless steel box is placed on the gantry 2 and the change in the internal temperature when the box using the solar reflective paint is placed on the gantry 2. To describe.

When the radiative cooling box W is placed on the gantry 2, the internal temperature tends to rise because the radiative cooling box W is not in contact with the ground 1. In addition, since heat is exchanged with the outside air on all six surfaces including the bottom surface, it is easily affected by the outside air.
In the case of a stainless steel box in the south, the internal temperature is about 6 ° C higher than that of the radiative cooling box W. Further, in the case of a box using a solar reflective paint at the time of south-central time, the internal temperature is about 1 ° C. higher than that of the radiative cooling type box W.

Based on the results of this test, an electrical case for storing electrical equipment, such as a distribution case for storing electrical equipment for distribution and a storage battery case for storing storage batteries, is configured as a radiative cooling box W and placed on the gantry 2. Even if the form is adopted, it is possible to suppress an increase in the internal temperature.
If the infrared absorption layer Z is mounted on the inner surface of the housing E, the increase in the internal temperature can be further suppressed.

FIG. 33 shows a state in which a stainless steel rectangular parallelepiped radiative cooling box W containing a storage battery is placed close to a wall 3 on the west side of a house and placed on a mounting portion 4 such as a balcony via sleepers 5. In the radiative cooling type box W illustrated, the radiative cooling layer CP is mounted on four surfaces excluding the bottom surface portion and the back surface portion facing the wall 3.
Changes in the top surface temperature of the housing E (the temperature corresponding to the back surface temperature of the radiative cooling layer CP, hereinafter abbreviated as the housing temperature with the radiative cooling layer) in the radiative cooling box W installed in the above state, and The results of measuring the change in the top surface temperature (hereinafter, abbreviated as the temperature of the storage battery with the radiative cooling layer) of the storage area housed in the radiative cooling box W are shown in FIGS. 34 to 36.

The housing E not provided with the radiative cooling layer CP is installed side by side in the radiative cooling type box W in the same state as the radiative cooling type box W, and the upper surface temperature of the housing E (hereinafter, the housing without the radiative cooling layer) is installed. The results of measuring the change in the body temperature (abbreviated as body temperature) and the change in the top surface temperature of the storage area stored in the housing E (hereinafter, abbreviated as the temperature of the storage battery without the radiative cooling layer) are shown in FIGS. 34 to 36. Describe.

In FIG. 34, the site temperature (outside air temperature) of the place where the radiative cooling box W and the housing E without the radiative cooling layer CP are installed is set to zero, and the housing temperature with the radiative cooling layer and without the radiative cooling layer are taken. The housing temperature of the above is shown, and the change in the amount of solar radiation on July 28, 2019 is also shown.
FIG. 35 shows the storage battery temperature with the radiative cooling layer and the storage battery temperature without the radiative cooling layer, where the site temperature of the place where the radiative cooling box W and the housing E without the radiative cooling layer CP are installed is zero degree. Moreover, the change in the amount of solar radiation on July 28, 2019 is also shown.
FIG. 36 is a diagram showing the correlation between the on-site temperature, the temperature of the storage battery with the radiative cooling layer, and the temperature of the storage battery without the radiative cooling layer.

Since the housing E without the radiative cooling box W and the radiative cooling layer CP is installed on the west side, the difference between the housing temperature with the radiative cooling layer and the housing temperature without the radiative cooling layer, and the radiative cooling The difference between the temperature of the storage battery with a layer and the temperature of the storage battery without a radiative cooling layer stands out after 12:00.
While the housing temperature with the radiative cooling layer maintains the temperature of about the site temperature throughout the day, the housing temperature without the radiative cooling layer rises by up to 15 ° C above the site temperature. ..

The temperature of the housing with the radiative cooling layer is higher than the on-site temperature by about 1 ° C to 2 ° C after 12:00, which is due to the fact that the house and the box are installed close to each other. The outer wall of the house is warmed by the sun, and it is heated when it receives the heat radiation. It is also heated by the heat radiation of nearby asphalt. Further, since the eastern sky cannot be seen from the radiative cooling box W, heat dissipation to outer space is reduced. From the above, the temperature rose a little.

The temperature of the storage battery with the radiative cooling layer is a little lower than the on-site temperature throughout the day, or even if it rises above the on-site temperature, it is about 1 ° C.
On the other hand, the temperature of the storage battery without the radiative cooling layer increased by about 7 ° C. at the maximum.
For example, in the case of a storage battery, if it is used in an environment where the temperature exceeds 40 ° C., the internal transmission board and the storage battery itself deteriorate faster. Therefore, a control logic is built in to stop the operation when the temperature exceeds 40 ° C. When the radiative cooling type box W is used, the frequency of equipment stoppage in summer is reduced as compared with a general distribution box not provided with the radiative cooling layer CP, although it depends on the site temperature (outside air temperature).

The same applies to various devices such as fuel cells, mega solar distribution boards, and electric vehicles. As a box for these devices, a radiant cooling box having a radiant cooling layer CP on the outer surface of the housing E. When configured to W, various effects can be obtained, such as extending the life of the electrical equipment stored in the box, preventing the device stored in the box from stopping, extending the mileage, and increasing safety.

[Another installation form of the radiative cooling layer]
As a form in which the radiative cooling layer CP is attached to the housing E, as shown in FIG. 37, a developed view of the rectangular parallelepiped excluding the bottom surface is formed according to the outer surface of the rectangular parallelepiped housing E excluding the bottom surface. The radiative cooling layer CP is formed.
Then, the magic tape 6 (registered trademark, the same applies hereinafter) is attached to the required portion of the developed radiative cooling layer CP.

Therefore, when the radiative cooling layer CP is attached to the housing E, the developed radiative cooling layer CP is wound so as to cover the housing E and fixed with the magic tape 6.
In this case, the radiative cooling layer CP can be attached without using the connection layer S.

[Another example of a radiative cooling box]
The article storage portion 7 of the truck of the van body shown in FIG. 38 is configured in the radiative cooling type box W, and the container 8 transported by the truck or railroad vehicle shown in FIG. 39 is configured in the radiative cooling type box W. be able to.
That is, the radiative cooling layer CP is attached to the housing E constituting the article storage section 7, and the article storage section 7 is configured as the radiative cooling box W.
Further, the radiative cooling layer CP is attached to the housing E constituting the container 8 to form the container 8 in the radiative cooling box W.

When the article storage portion 7 and the container 8 of the truck of the van body are configured in the radiative cooling type box W, the radiative surface H of the radiative cooling layer CP may be formed in an uneven shape as shown in FIG. 40.
That is, for example, it may be formed in a state where the convex portion U exists on the radiation surface H.
Examples of the uneven shape include a line-and-space structure in which line-shaped convex portions U are arranged (see FIG. 42), a structure in which convex portions U of conical columns are arranged vertically and horizontally (see FIG. 43), and a triangular prism, although not shown, is shown. , Pyramid-shaped convex parts U arranged in a line-and-pace pattern, although not shown, a structure in which square-shaped convex parts U are arranged vertically and horizontally, a structure in which convex parts U are randomly formed, and the like. The configuration can be adopted.
Incidentally, the height difference when the radial surface H is formed in an uneven shape is about 100 μm.

The advantage of forming the uneven portion U on the radial surface H will be described with the container 8 as a representative.
The container 8 is often used by being placed on a moving body such as a truck bed, a railroad vehicle, or a ship.
As shown in FIG. 41, since the truck moves, the underside of the truck during the day always has heated asphalt. Due to the inflow of heat from heated asphalt or the like, even if the housing E of the container 8 is covered with the radiative cooling layer CP, the internal temperature of the container 8 may rise above the ambient temperature (outside air temperature).
In the case of a moving body, it receives a strong wind while moving. This wind is lower than the temperature inside the container heated by asphalt or the like, and it is desirable to introduce a design that also considers heat exchange (convection) due to the running wind.

To summarize the discussion so far. The heat input of the container 8 is the following two points.
The first point is heat input by sunlight.
The second point is thermal radiation derived from heated asphalt (because it moves, the container is always directly above the hot asphalt).
Due to the influence of these two points, the inside of the container may become hotter than the ambient temperature (outside air temperature).

When the container 8 is configured as a radiative cooling box W, the radiative cooling layer CP tries to exhaust the heat of the container 8, so that the temperature inside the container is relative to that when other materials such as solar reflective paint are attached. Decreases to. However, since the heat inflow derived from asphalt at the second point is large, the temperature tends to rise higher than the ambient temperature (outside air temperature) during the daytime even though the radiative cooling layer CP is provided. When the temperature inside the container is higher than the ambient temperature (outside air temperature), it is desirable that the outside air acts as a cold heat source and increases heat exchange with the outside air. In particular, since the moving body receives a strong wind during movement, a structure that easily receives the wind and exchanges heat is introduced into the radiative cooling layer CP. That is, in order to increase the heat exchange with the wind, it is better to increase the surface roughness and the surface area.

From this point of view, as shown in FIG. 40, it is preferable to increase the surface area by forming the radiating surface H of the infrared radiating zone A of the radiative cooling layer CP into a concavo-convex shape by embossing or the like.
That is, in this structure, there is a heat source other than sunlight and the heated atmosphere, and the temperature of the housing E to which the radiant cooling layer CP is mounted rises above the ambient temperature (outside air temperature), and the ambient temperature (outside air temperature) rises. It is recommended to introduce it when it acts as cold heat.

Forming the radial surface H in an uneven shape also has an advantage in terms of appearance. When the radiant surface H (upper surface) of the radiative cooling layer CP is a mirror surface, sunlight is scattered when the radiant surface H is formed in an uneven shape, so that the radiative cooling layer CP is glaring. It will be reduced. If the radiative cooling layer CP is not glaring, the visibility is improved and the safety during running is improved.
Even if the radiation surface H is provided with the function of "scattering", the light absorption in the silver (silver alloy) of the light reflecting layer B does not increase, so that radiative cooling can be performed satisfactorily.

As another radiative cooling type box W, a radiative cooling type box W can be obtained by mounting a radiative cooling layer CP on the outer surface of a milk tank for storing milk or a milk storage portion of a milk tank lorry.

[Another configuration of the infrared radiation zone]
As shown in FIG. 44, the resin material layer J constituting the infrared radiation zone A may be mixed with the filler V of the inorganic material to provide a light scattering configuration. Further, as shown in FIG. 45, both the front and back surfaces of the resin material layer J constituting the infrared radiation layer A may be formed in an uneven shape to provide a light scattering configuration.
With this configuration, when the radiation surface H is viewed, the glare of the radiation surface H can be suppressed.

That is, the resin material layer J described above has a structure in which both the front and back surfaces are flat and the filler V is not mixed. However, in the case of such a structure, the radiation surface H becomes a mirror surface, so that the radiation surface H can be seen. At that time, glare is felt, but this glare can be suppressed by providing a light scattering configuration.
Further, when the filler V is mixed in the resin material layer J, if the protective layer D and the light reflection layer B are present, the case where only the resin material layer J in which the filler V is mixed is present or the case where only the light reflection layer B is present. The light reflectance is improved.

As the inorganic material for forming the filler V, silicon dioxide (SiO ₂ ) _, titanium oxide (TiO ₂ ), aluminum oxide (Al ₂ O ₃ ), magnesium oxide (MgO) and the like can be preferably used. When the filler V is mixed in the resin material layer J, both the front and back surfaces of the resin material layer J become uneven.
Further, in order to make both the front and back surfaces of the resin material layer J uneven, it can be performed by embossing or scratching the surface.

When the back surface of the resin material layer J is uneven, the glue layer N (bonding layer) is located between the resin material layer J and the protective layer D, as in the configuration described with reference to FIG. Is desirable.
That is, even if the back surface of the resin material layer J is uneven, the glue layer N (bonding layer) is located 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 separated. Can be joined properly.

When the back surface of the resin material layer J is uneven, for example, the resin material layer J and the protective layer D may be directly bonded by plasma bonding. The plasma bonding is a form in which radicals are formed by radiation of plasma on the bonding surface of the resin material layer J and the bonding surface of the protective layer D, and the radicals are used for bonding.

By the way, when the filler V is mixed in the protective layer D, the back surface of the protective layer D in contact with the light reflecting layer B becomes uneven, which causes the surface of the light reflecting layer B to be deformed in an uneven shape. It is necessary to avoid mixing the filler V. That is, if the surface of the light reflecting layer B is deformed into an uneven shape, light reflection cannot be performed properly, and as a result, radiative cooling cannot be performed properly.

[Another Embodiment]
Hereinafter, another embodiment will be listed.
(1) In the above embodiment, various resin materials for forming the resin material layer J have been exemplified, but the resin materials that can be preferably used include vinyl chloride resin (PVC), vinylidene chloride resin (PVDC), and foot. Examples thereof include vinyl chloride resin (PVF) and vinylidene fluoride resin (PVDF).

(2) In the above embodiment, a rectangular parallelepiped or cubic shape is exemplified as the housing E, but various shapes such as an ellipse shape and a spherical shape can be targeted for cooling.

(3) In the above embodiment, the case where the protective layer D is provided is illustrated, but the protective layer D may be omitted.

(4) In the above embodiment, the embodiment in which the radiation surface H of the resin material layer J is exposed is illustrated, but a hard coat covering the radiation surface H may be provided.
As the hard coat, there are UV-curable acrylic type, thermosetting acrylic type, UV-curable silicone type, thermosetting silicone type, organic-inorganic hybrid type, and vinyl chloride, and any of them may be used. An organic antistatic agent may be used as an additive.
Urethane acrylate is particularly good among UV-curable acrylics.

As a hard coat film forming method, a gravure coat method, a bar coat method, a knife coat method, a roll coat method, a blade coat method, a die coat method and the like can be used.
The thickness of the hard coat (coating film) is 1 to 50 μm, and particularly preferably 2 to 20 μm.

When a vinyl chloride resin is used as the resin material of the resin material layer J, the amount of the plasticizer of the vinyl chloride resin may be reduced to obtain a hard vinyl chloride resin or a semi-hard vinyl chloride resin. In this case, the vinyl chloride itself of the radiation layer becomes the hard coat layer.

The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in the present specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

A Infrared radiation layer B Light reflection layer D Protective layer E Housing H Radiation surface J Resin material layer U Concavo-convex part Z Infrared absorption layer

Claims (21)

A radiative cooling layer is attached to the outer surface of the housing for storing goods,
The radiative cooling layer is configured to include an infrared radiating layer that radiates infrared light from the radiating surface and a light reflecting layer that is located on the opposite side of the radiating layer from the existing side of the radiating surface. ,
The infrared radiant layer is a resin material layer adjusted to a thickness that emits thermal radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm.
A radiative cooling box in which the light reflecting layer is silver or a silver alloy. It is configured to have a protective layer between the infrared radiation layer and the light reflection layer.
The radiative cooling type box according to claim 1, wherein the protective layer is a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate resin having a thickness of 17 μm or more and 40 μm or less. The radiative cooling type box according to claim 1 or 2, wherein the radiative cooling layer is attached to the outer surface of the housing with an adhesive or adhesive connecting layer having a thickness of 5 μm or more and 100 μm or less. The radiative cooling type box according to any one of claims 1 to 3, wherein the radiative cooling layer is mounted on an outer surface portion of the outer surface of the housing excluding a bottom surface portion. The radiative cooling type box according to any one of claims 1 to 4, wherein the radiant surface in the radiative cooling layer is formed in an uneven shape. The radiative cooling type box according to any one of claims 1 to 5, wherein an infrared absorbing layer is mounted on the inner surface of the housing. The method according to any one of claims 1 to 6, wherein the light reflecting layer has a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and a reflectance of a long wave having a wavelength of 0.5 μm or more of 96% or more. Radiative cooling box. The film thickness of the resin material layer is
The wavelength average of the light absorption rate from 0.4 μm to 0.5 μm is 13% or less, the wavelength average of the light absorption rate from 0.5 μm to 0.8 μm wavelength is 4% or less, and the wavelength average is 0.8 μm. It has a light absorption characteristic in which the wavelength average of the light absorption rate up to a wavelength of 1.5 μm is within 1%, and the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less.
The radiative cooling type box according to any one of claims 1 to 7, wherein the thickness is adjusted to a state having a thermal radiation characteristic in which the wavelength average of the emissivity of 8 μm to 14 μm is 40% or more. The resin material forming the resin material layer is selected from a resin material having at least one of a carbon-fluorine bond, a siloxane bond, a carbon-chlorine bond, a carbon-oxygen bond, an ether bond, an ester bond, and a benzene ring. The radiant cooling type box according to any one of claims 1 to 8. The main component of the resin material forming the resin material layer is siloxane.
The radiative cooling type box according to any one of claims 1 to 8, wherein the thickness of the resin material layer is 1 μm or more. The radiative cooling type box according to claim 9, wherein the thickness of the resin material layer is 10 μm or more. The radiative cooling type box according to any one of claims 1 to 11, wherein the thickness of the resin material layer is 20 mm or less. The radiative cooling type box according to claim 12, wherein the resin material forming the resin material layer is fluororesin or silicone rubber. The resin material forming the resin material layer is a resin material having a hydrocarbon as a main chain having at least one of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring, or a side chain. A silicone resin having two or more carbon atoms in a chain hydrocarbon.
The radiative cooling type box according to any one of claims 1 to 11, wherein the thickness of the resin material layer is 500 μm or less. A claim that the resin material forming the resin material layer is a blend of a resin containing a carbon-fluorine bond and a siloxane bond and a resin having a hydrocarbon as a main chain, and the thickness of the resin material layer is 500 μm or less. The radiated cooling type box according to any one of 1 to 11. The resin material forming the resin material layer is a fluororesin.
The radiative cooling type box according to any one of claims 1 to 11, wherein the thickness of the resin material layer is 300 μm or less. The resin material forming the resin material layer is a resin material having at least one of a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, and a benzene ring.
The radiative cooling type box according to any one of claims 1 to 11, wherein the thickness of the resin material layer is 50 μm or less. The resin material forming the resin material layer is a resin material having a carbon-silicon bond.
The radiative cooling type box according to any one of claims 1 to 11, wherein the thickness of the resin material layer is 10 μm or less. The resin material forming the resin material layer is vinyl chloride resin or vinylidene chloride resin.
The radiative cooling type box according to any one of claims 1 to 8, wherein the thickness of the resin material layer is 100 μm or less and 10 μm or more. The radiative cooling type box according to any one of claims 1 to 17, wherein the light reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more. The invention according to any one of claims 1 to 17, wherein the light reflecting layer has a laminated structure of silver or a silver alloy located adjacent to the protective layer and aluminum or an aluminum alloy located on a side away from the protective layer. Radiative cooling box.

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