JP2022146658A - Radiation cooling type light-shielding device - Google Patents

Abstract

To provide a radiation cooling type light-shielding device that can suppress the temperature rise of a shading target in daytime sunlight environment.SOLUTION: Provided is a radiation cooling type light-shielding device in which a light-shielding body M having a radiation cooling layer CP is provided on the outer surface side, and the sunlight absorptivity of the inner surface of the light-shielding body M is 70% or more.SELECTED DRAWING: Figure 1

Description

The present invention relates to a radiative cooling shading device having a radiative cooling action.

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

As a conventional example of a radiative cooling device (radiative cooling layer), an infrared radiation layer that emits infrared light from a radiation surface and a light reflection layer that is positioned on the opposite side of the radiation layer to the side where the radiation surface exists and are provided in a laminated state, the infrared radiation layer is formed of a single crystal, polycrystal, or sintered body of magnesium oxide, and the light reflection layer is configured to include silver or a silver alloy. There is a thing (for example, see patent document 1).

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

In addition to the light transmitted through the infrared radiation layer, the light reflection layer also has the function of reflecting the light emitted from the infrared radiation layer toward the side where the light reflection layer exists 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 light (ultraviolet light, visible light, infrared light) transmitted through the infrared radiation layer.

JP 2019-168174 A

Light shielding devices used for various purposes such as parasols, awnings, awning tents (tents with a roof and open side portions), turf, etc. Although it is desired that the light shielding device suppresses the temperature rise of the light shielding target whose upper side is covered, the conventional light shielding device cannot suppress the temperature rise of the light shielding target.

That is, for example, in a parasol as a light shielding device, it is possible to prevent the user (light shielding target) using the parasol from being irradiated with sunlight. (membrane material such as cloth) becomes hot by irradiation with sunlight, and there is a risk that the user (light shielding target) is heated by heat transfer from the light shielding body (membrane material such as cloth) which has become hot.
In addition, the inner surface of the light shielding body (membrane material such as cloth) that forms a parasol by reflecting the sunlight irradiated to the ground surface such as the road surface or concrete road surface on which the user (light shielding target) is located. In other words, when sunlight is reflected back, the irradiated sunlight is reflected on the inner surface of the light shielding material (film material such as cloth) that forms the parasol. There is a possibility that the user (light shielding target) may be heated by being irradiated to the person (light shielding target).

In other words, in the conventional light shielding device, there is a risk that the light shielding body heated to a high temperature due to the irradiation of sunlight may heat the light shielding object, and when the sunlight is reflected, the sunlight is reflected on the inner surface of the light shielding body. There is a possibility that the target to be shielded may be heated by being radiated to the target to be shielded, and as a result, the temperature rise of the target to be shielded cannot be suppressed.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a radiative cooling light shielding device capable of suppressing a temperature rise of a light shielding object in a daytime sunlight environment.

The radiation-cooling light-shielding device of the present invention is characterized in that a light-shielding body having a radiation-cooling layer is provided on the outer surface side, and the sunlight absorptivity of the inner surface of the light-shielding body is 70% or more.

That is, since the radiation cooling layer is provided on the outer surface side of the light shielding body arranged so as to cover the light shielding object, the light shielding body is cooled by the radiation cooling action of the radiation cooling layer. Also, by avoiding the temperature rise of the light shielding body, it is possible to avoid the light shielding body from heating the light shielding object.

In addition, since the sunlight absorption rate of the inner surface of the light shielding body is 70% or more, most of the sunlight is absorbed even if the sunlight is reflected on the inner surface of the light shielding body when reflected sunlight occurs. Therefore, it is possible to avoid the sunlight irradiated to the inner surface of the light shielding body from being reflected by the inner surface and heating the light shielding object.
Incidentally, the temperature of the light shielding body rises as it absorbs the sunlight irradiated on its inner surface. conversion will be avoided.

In this way, the temperature of the light shielding body arranged to cover the light shielding object is avoided, and moreover, the heat of the light shielding object due to reflection of the reflected sunlight on the inner surface of the light shielding object is avoided. Therefore, it is possible to suppress the temperature rise of the light-shielded object under the sunlight environment in the daytime.

In short, according to the characteristic structure of the radiative cooling type light shielding device of the present invention, it is possible to suppress the temperature rise of the light shielding object under the sunlight environment in the daytime.

A further characteristic configuration of the radiation-cooled light-shielding device of the present invention is that the light-shielding body includes the radiation-cooling layer on the outer surface of the body-forming base material, and the inner surface of the body-forming base material has a solar absorptivity. It is characterized by a form having a solar absorption layer of 70% or more.

In other words, the light shielding body is configured to have a solar absorption layer having a solar absorption rate of 70% or more on the inner surface of the main body forming substrate having the radiation cooling layer on the outer surface.
In this way, since the solar absorption layer is formed as a separate layer from the main body forming substrate having the radiation cooling layer on the outer surface, for example, the main body forming substrate constitutes a light shielding body suitable for the application. By using a material suitable for light shielding and providing a solar light absorption layer on the inner surface of the light shielding member, the solar light absorption rate of the inner surface of the light shielding member can be increased to 70% or more.

The solar absorption layer is formed by laminating a film colored in a color suitable for absorbing sunlight, such as black or dark brown, on the inner surface of the main body forming member. The inner surface of the body-forming member can be provided with the solar absorbing layer in various forms, such as by applying a coating of a color suitable for absorbing sunlight.

In short, according to the characteristic configuration of the radiation cooling type light shielding device of the present invention, a light shielding body suitable for various uses can be favorably produced.

A further characteristic configuration of the radiation-cooling light-shielding device of the present invention is that the light-shielding body includes the radiation-cooling layer on the outer surface of the body-forming substrate, and the body-forming substrate has a sunlight absorptivity of 70%. It is in that it is formed with the material which is above.

That is, the light-shielding body is formed of the body-forming base material having the radiation cooling layer on its outer surface, and the body-forming base material is formed of a material having a solar absorptivity of 70% or more. Become.
That is, by forming the body-forming member having the radiative cooling layer on the outer surface thereof with a material having a solar absorptivity of 70% or more, the solar absorptance of the inner surface of the light shielding body is configured to be 70% or more. Therefore, in order to use the main body forming base material itself having the radiation cooling layer on the outer surface as a sunlight absorbing material, the structure of the light shielding body whose inner surface has a sunlight absorption rate of 70% or more is simplified. be able to.

In short, according to the characteristic structure of the radiation cooling type light shielding device of the present invention, the structure of the light shielding body can be simplified.

A further characteristic configuration of the radiation cooling type light shielding device of the present invention is that the light shielding body is formed of a flexible film-like body.

That is, since the light-shielding body is formed of a flexible film-like body, the light-shielding body can be used for parasols, awnings, awning tents (tents with a roof portion and side portions open), A shading device such as a turf can be constructed. In other words, it is possible to appropriately produce a light shielding device in which the light shielding body needs to be flexible.

In short, according to the characteristic configuration of the radiation-cooled light shielding device of the present invention, a light shielding device requiring flexibility of the light shielding body can be appropriately manufactured.

A further characteristic configuration of the radiation cooling type light shielding device of the present invention is that the light shielding body is provided in a state of covering the upper side of the light shielding target and opening the sides of the light shielding target.

That is, since the light shielding body is provided in a state in which the upper side of the light shielding target is covered and the side of the light shielding target is opened, sunlight is reflected on the inner surface of the light shielding body covering the upper side of the light shielding target. Then, the reflected sunlight is irradiated, but the irradiated sunlight is absorbed by the light shielding body.

In other words, even if the light shielding body having the radiative cooling layer on the outer surface side is provided in a state in which the upper side of the light shielding target is covered and the side of the light shielding target is open, the light shielding body is cooled by the radiation cooling effect of the radiative cooling layer. It is possible to avoid a rise in temperature, and to prevent the reflection of sunlight from reflecting on the inner surface of the light shielding body and heating the light shielding object, so that the temperature of the light shielding object can be properly increased in a daytime sunlight environment. can be suppressed.

In short, according to the characteristic configuration of the radiative cooling type light shielding device of the present invention, when the light shielding body is provided in a state in which the upper side of the light shielding target is covered and the side of the light shielding target is open, the daytime sunlight environment It is possible to appropriately suppress the temperature rise of the light shielding object under the light.

In the radiative cooling type light shielding device of the present invention, the radiative cooling layer is positioned on the opposite side of the infrared radiation layer that emits infrared light from the radiation surface and the side of the infrared radiation layer on which the radiation surface exists. and a light reflecting layer,
The infrared radiation layer is a resin material layer having a thickness adjusted to emit thermal radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm,
wherein the light reflective layer comprises silver or a silver alloy;
It is characterized in that the sunlight absorption rate of the sunlight absorption layer is 70% or more.

That is, the sunlight incident from the radiation surface of the resin material layer serving as the infrared radiation layer in the radiation cooling layer passes through the resin material layer, and then passes through the radiation surface of the resin material layer. It is reflected by the layer and escapes out of the system from the emitting surface.
In the description of this specification, when light is simply referred to, the concept of light includes ultraviolet light (ultraviolet light), visible light, and infrared light. In terms of wavelengths of light as electromagnetic waves, these include electromagnetic waves with wavelengths of 10 nm to 20000 nm (electromagnetic waves of 0.01 μm to 20 μm).

In addition, the heat transfer (heat input) to the radiative cooling layer is converted into infrared rays by the resin material layer and escaped from the radiation surface to the outside of the system.
In this way, the radiative cooling layer reflects sunlight irradiating the radiative cooling layer, and heat transfer to the radiative cooling layer (for example, heat transfer from the atmosphere or heat transfer from the light shield cooled by the radiative cooling layer). heat transfer) can be radiated out of the system as infrared light.

Since the thickness of the resin material layer is adjusted to emit thermal radiation energy larger than the absorbed sunlight energy in a wavelength band of 8 μm to 14 μm, sunlight is reflected by the light reflecting layer comprising silver or a silver alloy. It is possible to exhibit a cooling function even in a daytime sunlight environment while appropriately reflecting light.

Therefore, even in a daytime sunlight environment, the radiation cooling layer provided on the outer surface side of the light shielding body can cool the light shielding body. can be suppressed.
Of course, the presence of the radiative cooling layer suppresses the transmission of sunlight through the light shielding body, so that the sunlight does not pass through the light shielding body and irradiate the light shielding target.
Therefore, even in a daytime sunlight environment, it is possible to appropriately avoid heating of the light-shielding object by cooling the light-shielding body by the radiative cooling effect.

Incidentally, since the resin material layer is formed of a highly flexible resin material, the resin material layer can be made flexible. For example, flexibility can be provided.
Therefore, the radiative cooling layer including the resin material layer and the light reflecting layer can be made flexible, and the radiative cooling layer can be appropriately provided on the outer surface side of the light shielding member.

In short, according to the characteristic configuration of the radiative cooling type light shielding device of the present invention, it is possible to appropriately suppress the temperature rise of the light shielding body even when the usage environment is a solar environment with direct sunlight.

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

That is, the 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 passes through the light reflecting layer on the side opposite to the radiation surface of the resin material layer. , and escapes from the radiation surface to the outside of the system.

In addition, the protective layer is made of polyolefin resin and has a thickness of 300 nm or more and 40 μm or less, or is made of ethylene terephthalate resin and has a thickness of 17 μm or more and 40 μm or less. Even in a daytime sunlight environment, discoloration of the silver or silver alloy of the light reflection layer can be suppressed. can be performed accurately.

That is, in the absence of the protective layer, radicals generated in the resin material layer reach silver or silver alloy forming the light reflecting layer, and moisture passing through the resin material layer forms the light reflecting layer. By reaching the silver or silver alloy, the silver or silver alloy of the light reflecting layer may discolor in a short period of time, resulting in a state in which the light reflecting function is not properly exhibited. Short-term discoloration of silver or silver alloy in the layer can be suppressed.

A description will be added about suppressing discoloration of the silver or silver alloy of the light reflecting layer in the protective layer.
When the protective layer is made of polyolefin resin and has a thickness of 300 nm or more and 40 μm or less, the polyolefin resin is exposed to ultraviolet rays in the entire ultraviolet wavelength range of 0.3 μm to 0.4 μm. Since the protective layer is a synthetic resin having a light absorption rate of 10% or less, the protective layer is less likely to deteriorate due to the absorption of ultraviolet rays.

Since the thickness of the polyolefin-based resin forming the protective layer is 300 nm or more, radicals generated in the resin material layer are blocked from reaching the silver or silver alloy forming the light reflecting layer, and It satisfactorily exhibits a blocking function such as blocking moisture passing through the resin material layer from reaching the silver or silver alloy forming the light reflecting layer, thereby preventing discoloration of the silver or silver alloy forming the light reflecting layer. can be suppressed.

In other words, the protective layer formed of 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 the low absorption of ultraviolet rays. It will be demonstrated.

When the protective layer is made of ethylene terephthalate resin and has a thickness of 17 μm or more and 40 μm or less, the ethylene terephthalate resin has a wavelength range of 0.3 μm to 0.4 μm than the polyolefin resin. Although the resin material has a high 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 do not reach the silver or silver alloy forming the light reflecting layer. In addition, the protective layer satisfactorily exhibits a blocking function such as blocking moisture passing through the resin material layer from reaching the silver or silver alloy forming the light reflecting layer for a long period of time. Discoloration of the silver or silver alloy that forms the can be suppressed.

In other words, the protective layer formed of ethylene terephthalate resin deteriorates while forming radicals on the surface side away from the reflective layer due to the absorption of ultraviolet rays. Radicals do not reach the reflective layer, and even if the reflective layer deteriorates while forming radicals, the thickness is 17 μm or more, so the above shielding function is exhibited over a long period of time.

In the case of forming the protective layer with polyolefin resin and ethylene terephthalate resin, the reason for setting the upper limit of the thickness is to avoid as much as possible that the protective layer exhibits heat insulation properties that do not contribute to radiative cooling. . In other words, the thicker the protective layer is, the more heat insulation it does not contribute to radiation cooling. In order to do so, the upper limit of the thickness will be determined.

In short, according to the further characteristic configuration of the radiative cooling type light shielding device of the present invention, the light shielding body can be satisfactorily cooled while suppressing discoloration of the silver or silver alloy of the light reflecting layer in a short period of time.

A further characteristic configuration of the radiation-cooling light-shielding device of the present invention is that the radiation-cooling layer is attached to the outer surface of the light-shielding body with a connection layer of adhesive or pressure-sensitive adhesive.

That is, when the light shielding member has flexibility, the radiative cooling layer can be attached to the outer surface of the flexible light shielding member in a state of being in close contact with the connecting layer of the adhesive or pressure-sensitive adhesive.
Incidentally, the outer surface of the light shield is generally not a mirror surface but is formed in a state in which unevenness exists. Therefore, it is possible to suppress the unevenness of the outer surface of the light-shielding body from being reflected on the light-reflecting layer, and to maintain the light-reflecting layer in a flat state.

That is, when the unevenness of the outer surface of the light shielding member is reflected in the light reflecting layer, light is scattered due to the unevenness of the outer surface of the light shielding member, the reflectance of the light reflecting layer decreases, and the light is absorbed. However, by maintaining the light reflecting layer in a flat state, it is possible to suppress the decrease in the reflectance of the light reflecting layer.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the radiation cooling layer can be accurately attached to the outer surface of the light shielding body having flexibility in such a state that the radiation cooling layer is in close contact with the outer surface.

A further characteristic configuration of the radiation cooling type light shielding device of the present invention is that the radiation surface of the radiation cooling layer is formed in an uneven shape.

That is, the surface area of the radiation surface can be increased by forming the radiation surface in an uneven shape, and as a result, the radiation cooling layer can be cooled by wind, and the cooling function can be improved.
For example, when natural wind is blown to the location where the light blocking body exists, the cooling function can be improved by blowing the natural wind to the radiation surface.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the cooling function can be improved.

A further characteristic configuration of the radiation-cooled light shielding device 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 at a wavelength longer than 0.5 μm. It is in the point that it is.

That is, the sunlight spectrum exists from 0.3 μm to 4 μm in wavelength, and the intensity increases as the wavelength increases from 0.4 μm, especially from 0.5 μm to 2.5 μm.
When the light reflective layer exhibits a reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and has a reflectance of 96% or more at a wavelength longer than 0.5 μm, the light reflective layer can reflect sunlight. Absorbs less than 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 during the middle of summer, and radiative cooling by the resin material layer can be performed satisfactorily.
In this specification, unless otherwise specified, the spectrum of sunlight is based on the AM1.5G standard.

In short, according to the further characteristic configuration of the radiation-cooling light-shielding device of the present invention, it is possible to suppress the absorption of sunlight energy by the light reflecting layer and to perform the radiation cooling by the resin material layer satisfactorily.

A further characteristic configuration of the radiation cooling type light shielding device of the present invention is that the film thickness of the resin material layer is
The average wavelength of light absorptance at a wavelength of 0.4 μm to 0.5 μm is 13% or less, the average wavelength of light absorptance at a wavelength of 0.5 μm to 0.8 μm is 4% or less, and the wavelength from 0.8 μm The wavelength average of the light absorption rate up to a wavelength of 1.5 μm is within 1%, and the light absorption characteristic is such that the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less, and
The thickness is adjusted so as to provide thermal radiation characteristics such that the wavelength average of the emissivity from 8 μm to 14 μm is 40% or more.

The wavelength average of light absorptance at a wavelength of 0.4 μm to 0.5 μm means the average value of light absorptance for each wavelength in the range of 0.4 μm to 0.5 μm. The same applies to the average wavelength of light absorptance from 0.8 μm to 0.8 μm, the average of light absorptance from 0.8 μm to 1.5 μm, and the average of light absorptance from 1.5 μm to 2.5 μm. is. Other similar descriptions including emissivity mean similar average values, and the same applies hereinafter in this specification.

That is, the resin material layer changes its light absorption rate and emissivity (light emissivity) depending on its thickness. Therefore, it is necessary to adjust the thickness of the resin material layer so that it absorbs as little sunlight as possible and emits a large amount of thermal radiation in the so-called atmospheric window wavelength range (light wavelength range of 8 μm to 14 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 at a wavelength 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 absorptance from the wavelength of 0.8 μm is 4% or less, the wavelength average of the light absorptance from the wavelength of 0.8 μm to the wavelength of 1.5 μm is within 1%, and from 1.5 μm to 2.5 μm The wavelength average of the light absorptance up to is required to be 40% or less. As for the light absorptance from 2.5 μm to 4 μm, the wavelength average should be 100% or less.
In the case of such a distribution of light absorptance, the light absorptance of sunlight is 10% or less, which is 100 W or less in terms of energy.

That is, the light absorption rate of sunlight increases as the film thickness of the resin material layer increases. When the resin material layer is made thick, the emissivity of the atmospheric window becomes approximately 1, and the thermal radiation emitted into space at that time is 125 W/m ² to 160 W/m ² .
As described above, the absorption of sunlight by the light reflecting layer is preferably 50 W/m ² or less.
Therefore, the sum of sunlight absorption in the resin material layer and the light reflecting layer is 150 W/m ² or less, and if the atmospheric conditions are favorable, cooling proceeds. As described above, it is preferable to use a resin material layer having a small absorptance near the peak value of the sunlight spectrum.

In addition, from the viewpoint of the emissivity of the resin material layer for emitting infrared light (thermal radiation characteristics), the average wavelength of the emissivity at wavelengths of 8 μm to 14 μm must be 40% or more.
That is, in order for the resin material layer to emit into space about 50 W/m ² of solar thermal radiation absorbed by the light reflecting layer, the resin material layer needs to emit more thermal radiation.
For example, when the outside air temperature is 30° C., the maximum thermal radiation of an atmospheric window with a wavelength of 8 μm to 14 μm is 200 W/m ² (calculated as an emissivity of 1). This value can be obtained in fine weather in a very dry environment with thin air, such as in high mountains. Since the atmosphere is thicker in lowlands and the like than in high mountains, the wavelength band of the window of the atmosphere becomes narrower and the transmittance decreases. By the way, this phenomenon is called "the window of the atmosphere becomes narrower".

In addition, the environment in which the radiative cooling type shading device is actually used may be humid, and in that case the window to the atmosphere is also narrow. The thermal radiation generated in the atmospheric window region in low-lying applications is estimated to be 160 W/m ² at 30° C. under good conditions (calculated as an emissivity of 1).
Also, when there is haze in the sky or smog, which is common in Japan, the window of the atmosphere becomes even narrower and the radiation into space is about 125 W/m ² .

In view of this situation, the average wavelength of the emissivity of wavelengths 8 μm to 14 μm must be 40% or more (the thermal radiation intensity in the window zone of the atmosphere must be 50 W/m ² or more) to be used in the lowlands of the mid-latitudes.
Therefore, by adjusting the thickness of the resin material layer so as to fall within the optically specified range described above, the heat output from the atmospheric window becomes greater than the heat input due to the absorption of sunlight, and the sunlight in the daytime becomes larger. Radiative cooling can also be performed outdoors in the environment.

In short, according to the further characteristic configuration of the radiant cooling type light shielding device of the present invention, the heat output from the atmospheric window is greater than the heat input due to light absorption of sunlight, and radiative cooling can be performed even in a solar environment.

A further characteristic configuration of the radiative cooling type light shielding device of the present invention is that the resin material forming the resin material layer comprises a carbon-fluorine bond, a siloxane bond, a carbon-chlorine bond, a carbon-oxygen bond, an ether bond, an ester bond, It is selected from resin materials having one or more benzene 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 (C-O ), an ether bond (R--COO--R), an ester bond (C--O--C), or a benzene ring.

According to Kirchhoff's law, emissivity (ε) and light absorption (A) are equal. The light absorptance (A) can be calculated from the absorption coefficient (α) by the following formula 1.
A=1−exp(−αt) (Equation 1) where t is the film thickness.
That is, when the thickness of the resin material layer is increased, a large amount of thermal radiation can be obtained in a wavelength band with a large absorption coefficient. In the case of radiative cooling outdoors, it is preferable to use a material with a large absorption coefficient in the wavelength range of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere. In order to suppress the absorption of sunlight, it is preferable to use a material that has no or a small absorption coefficient 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 absorptance in Equation 1, the light absorptance (emissivity) varies 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 environment, the resin material that forms the resin material layer should have a large absorption coefficient in the wavelength band of the window of the atmosphere and a absorption coefficient in the wavelength band of the sunlight. By adjusting the film thickness of the resin material layer, it absorbs little sunlight, but emits more thermal radiation from the window of the atmosphere. can create a larger state.

The absorption spectrum of the resin material forming the resin material layer will be explained.
As for the carbon-fluorine bond (CF), the absorption coefficient due to CHF and CF ₂ spreads widely over a wide wavelength range from 8 μm to 14 μm, which is the atmospheric window, and the absorption coefficient is particularly large at 8.6 μm. In addition, regarding the wavelength band of sunlight, there is no conspicuous absorption coefficient in the wavelength range from 0.3 μm to 2.5 μm where the energy is large.

As a resin material having a CF bond,
Polytetrafluoroethylene (PTFE), which is a fully fluorinated resin,
partially fluorinated resins polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF),
perfluoroalkoxy fluororesin (PFA), which is a fluorinated resin copolymer;
ethylene tetrafluoride/propylene hexafluoride copolymer (FEP),
ethylene/tetrafluoroethylene copolymer (ETFE),
Ethylene-chlorotrifluoroethylene copolymer (ECTFE) may be mentioned.

The bond energies of the C—C bond, C—H bond, and C—F bond of the basic structure of polyvinylidene fluoride (PVDF) as a representative are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and absorb light shorter than these wavelengths.
Since the sunlight spectrum consists only of wavelengths longer than 0.300 μm, the use of fluororesin hardly absorbs ultraviolet rays, visible rays, and near-infrared rays of sunlight.
In addition, the ultraviolet rays are in the wavelength range shorter than 0.400 μm, the visible rays are in the wavelength range of 0.400 μm to 0.800 μm, the near infrared rays are in the wavelength range of 0.800 μm to 3 μm, and the middle infrared rays are in the wavelength range of 3 μm. to 8 μm, and the far-infrared rays are in the range on the longer wavelength side than the wavelength of 8 μm.

Examples of resin materials having siloxane bonds (Si--O--Si) include silicone rubbers and silicone resins. In this resin, 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 an absorption coefficient due to the out-of-plane deformation (pitch) of CSiH ₂ appears at a wavelength of 10 μm. It appears broadly at the center, and the absorption coefficient due to the in-plane deformation angle (scissors) of CSiH ₂ appears small around a wavelength of 8 μm. Thus, it has a large absorption coefficient in the atmospheric window. As for the ultraviolet region, the bond 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 the shorter wavelength side than this wavelength. Since the spectrum of sunlight consists only of wavelengths longer than 0.300 μm, the use of siloxane bonds hardly absorbs ultraviolet rays, visible rays, and near-infrared rays of sunlight.

As for the carbon-chlorine bond (C--Cl), the absorption coefficient due to the C--Cl stretching vibration appears in a wide band with a half-value width of 1 μm or more around the wavelength of 12 μm.
In addition, polyvinyl chloride (PVC) is an example of a resin material having a carbon-chlorine bond (C-Cl). In the case of polyvinyl chloride, due to the electron attraction of chlorine, the C An absorption coefficient derived from bending vibration of −H appears around a wavelength of 10 μm. That is, it is possible to emit large thermal radiation in the wavelength band of the window of the atmosphere. The binding energy of carbon and chlorine in alkene is 3.28 eV, and its wavelength corresponds to 0.378 μm, and absorbs light on the shorter wavelength side than this wavelength. In other words, it absorbs ultraviolet rays of sunlight, but has almost no absorption in the visible range.

Ether bonds (R-COO-R) and ester bonds (C-O-C) have absorption coefficients in the wavelength range from 7.8 μm to 9.9 μm. In addition, a carbon-oxygen bond contained in an ester bond or an ether bond exhibits a strong absorption coefficient over a wavelength band of 8 μm to 10 μm.
When a benzene ring is introduced into the side chain of the hydrocarbon resin, absorption appears widely over the wavelength range of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements under the influence of the benzene ring.
Resins having these bonds include polymethyl methacrylate resin, ethylene terephthalate resin, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate and polybutylene naphthalate. For example, methyl methacrylate has a C—C bond energy of 3.93 eV, which corresponds to a wavelength of 0.315 μm, and absorbs sunlight 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-described emissivity and absorptivity 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 substituted.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the radiation cooling layer can create a state in which the radiation cooling output is greater than the sunlight input.

A further characteristic configuration of the radiation-cooled light-shielding device of the present invention is that the main component of the resin material forming the resin material layer is siloxane,
The thickness of the resin material layer is 1 μm or more.

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

In short, according to a further characteristic configuration of the radiation-cooling light-shielding device of the present invention, in the case where the main component of the resin material forming the resin material layer is siloxane, the radiation-cooling layer is cooled by radiation rather than by the input of sunlight. The output can create a larger state.

A further characteristic configuration of the radiation cooling type light shielding device of the present invention is that the thickness of the resin material layer is 10 μm or more.

That is, carbon-fluorine bond (C-F), carbon-chlorine bond (C-Cl), carbon-oxygen bond (C-O), ester bond (R-COO-R), ether bond (C-O-C ), in the case of a resin material whose main constituent is one of the benzene rings, if the film thickness is 10 μm or more, the radiation intensity at the window of the atmosphere increases, and the output by radiative cooling is greater than the input of sunlight. You can create big situations.

In short, according to a further characteristic configuration of the radiation-cooled light shielding device of the present invention, the resin material forming the resin material layer contains carbon-fluorine bonds (CF), carbon-chlorine bonds (C-Cl), carbon - In the case of a resin material whose main structural element is any of oxygen bonds (C-O), ester bonds (R-COO-R), ether bonds (C-O-C), and benzene rings, the radiative cooling layer is the sun A state can be created in which the output of radiative cooling is greater than the input of light.

A further characteristic configuration of the radiation cooling type light shielding device 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 occurs within a range of about 100 μm from the surface of the material.
That is, even if the thickness of the resin material increases, the thickness that contributes to radiative cooling does not change, and the remaining thickness acts to insulate cold heat after radiative cooling. Assuming that a resin material layer that does not absorb sunlight at all is ideally formed, sunlight is absorbed only by the light reflection layer of the radiative cooling light shielding device.

The thermal conductivity of resin materials is generally about 0.2 W/m·K, and when the thickness of the resin material layer exceeds 20 mm, the cooling surface (the resin material layer in the light reflection layer temperature rises on the side opposite to the side where the 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/mK. (Radiative cooling) cannot cool the light shielding member cooled by the cooling surface, and the light shielding member is heated by receiving solar radiation.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the light shielding body can be cooled appropriately.

A further characteristic configuration of the radiation cooling light shielding device of the present invention is that the resin material forming the resin material layer is fluororesin or silicone rubber.

That is, carbon-fluorine bonds (C-F) are the main constituent fluororesins, that is, polytetrafluoroethylene (PTFE), polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), polyvinyl fluoride (PVF) ), perfluoroalkoxy fluororesin (PFA), and ethylene tetrafluoride/propylene hexafluoride copolymer (FEPP) have almost no light absorption in the ultraviolet, visible, and near-infrared regions of the sunlight spectrum.

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

In short, according to a further characteristic configuration of the radiation cooling type light shielding device of the present invention, when the resin material of the resin material layer is fluororesin or silicone rubber, the radiation cooling layer can appropriately exhibit the radiation cooling function. can.

A further characteristic configuration of the radiative cooling light shielding device of the present invention is that the resin material forming the resin material layer has one of carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, and benzene ring. or a silicone resin having a hydrocarbon side chain with 2 or more carbon atoms,
The thickness of the resin material layer is 500 μm or less.

That is, the resin material forming the resin material layer has a carbon-chlorine bond (C-F), a carbon-oxygen bond (C-O), an ester bond (R-COO-R), an ether bond (C-O-C ), in the case of a resin whose main chain is a hydrocarbon having one or more benzene rings, or in the case of a silicone resin in which the number of carbon atoms in the side chain hydrocarbon is 2 or more, In addition to the ultraviolet absorption by covalent electrons, absorption based on vibrations such as bending and stretching of bonds appears in the near-infrared region.

Specifically, the absorption due to the reference tone of the transition to the first excited state of CH ₃ , CH ₂ , and CH from 1.6 μm to 1.7 μm, from 1.65 μm to 1.75 μm, and from 1.7 μm, respectively. appear. Furthermore, absorption by reference tones of CH ₃ , CH ₂ and CH combination tones appears at wavelengths of 1.35 μm, 1.38 μm and 1.43 μm, respectively. Furthermore, overtones of transitions of CH ₂ and CH to the second excited state appear at wavelengths around 1.24 μm. The reference tones for bending and stretching of C—H bonds are distributed over a wide band from 2 μm to 2.5 μm in wavelength. Further, when having 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, polymethyl methacrylate resin, ethylene terephthalate resin, polytrimethylene terephthalate, polybutylene terephthalate, polyethylene naphthalate, polybutylene naphthalate, and polyvinyl chloride are attributed to CH ₃ , CH ₂ , and CH in the near infrared region. It exhibits similar light absorption properties. When these resin materials are thickened to a thickness of 20 mm, which is defined from the viewpoint of thermal conductivity, they are heated by absorbing near-infrared rays contained in sunlight. Therefore, when using these resin materials, the thickness must be 500 μm or less.

In short, according to a further characteristic configuration of the radiative cooling light shielding device of the present invention, the resin material has one or more of carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings. Near-infrared absorption can be suppressed in the case of a resin having a hydrocarbon main chain or a silicone resin having a hydrocarbon side chain with 2 or more carbon atoms.

A further characteristic configuration of the radiative cooling light shielding device 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 or a siloxane bond and a resin having a hydrocarbon main chain. and the resin material layer has a thickness of 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 blended resin material, light absorption in the near-infrared region due to CH, CH ₂ , CH ₃ and the like appears depending on the proportion of the blended resin having a hydrocarbon as a main chain. When carbon-fluorine bonds or siloxane bonds are the main component, light absorption in the near-infrared region due to hydrocarbons is reduced, so the thickness can be increased up 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 must be 500 μm or less.

Blends of fluororesins or silicone rubbers and hydrocarbons include fluororesins or silicone rubbers in which the side chains are substituted with hydrocarbons, alternating copolymers of fluoromonomers, silicone monomers and hydrocarbon monomers, random copolymers, Block copolymers and graft copolymers are also included. Examples of alternating copolymers of fluorine monomers and hydrocarbon monomers include fluoroethylene-vinyl ester (FEVE), fluoroolefin-acrylic acid ester copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene- Chlorotrifluoroethylene copolymer (ECTFE) may be mentioned.

Light absorption in the near-infrared region due to CH, CH ₂ , CH ₃ and the like appears depending on the molecular weight and proportion of the substituted hydrocarbon side chain.
When the monomer introduced as a side chain or copolymerization has a low molecular weight, or when the density of the introduced monomer is small, the absorption of light in the near-infrared region caused by hydrocarbons becomes small, so the thermal conductivity is improved. It can be thickened up to the limit of 20 mm in .
When a high molecular weight hydrocarbon is introduced as a side chain of a fluororesin or a silicone rubber or a monomer to be copolymerized, the thickness of the resin must be 500 μm or less.

In short, according to a further characteristic configuration of the radiative cooling type light shielding device of the present invention, when the resin material is a blend of a resin containing a carbon-fluorine bond or a siloxane bond and a resin having a hydrocarbon main chain, Absorption of near-infrared rays can be suppressed.

A further characteristic configuration of the radiation-cooled light shielding device of the present invention is that the resin material forming the resin material layer is a fluororesin,
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 preferably have a thin resin material layer. The thermal conductivity of resin materials is generally lower than that of metals, glass, and the like. In order to effectively cool the object to be cooled (light-shielding body), the film thickness of the resin material layer should be the minimum necessary. As the film thickness of the resin material layer increases, the thermal radiation from the atmospheric window increases. When the film thickness exceeds a certain value, the thermal radiation energy from the atmospheric window becomes saturated.

Although the film thickness of the resin material layer to be saturated depends on the resin material, in the case of fluororesin, a thickness of approximately 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 thermal radiation is not saturated, sufficient thermal radiation can be obtained in the atmospheric window region even with a thickness of about 100 μm. The thinner the thickness, the higher the heat transfer coefficient and the more effectively the temperature of the object to be cooled can be lowered.

In the case of a fluororesin, the absorption coefficient derived from carbon-silicon bond, carbon-chlorine bond, carbon-oxygen bond, ester bond, and ether bond is larger than the absorption coefficient derived from CF bond. Of course, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm.
Incidentally, polyvinyl fluoride (PVF) and polyvinylidene fluoride (PVDF) can be preferably used as an example of the fluororesin.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the radiation cooling effect can be improved when the resin material is fluororesin.

A further characteristic configuration of the radiative cooling light shielding device of the present invention is that the resin material forming the resin material layer has one of carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, and benzene ring. It is a resin material having the above,
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, or a benzene ring, even if the thickness is 100 μm, the thermal radiation energy at the atmospheric window is saturated. Even with a thickness of 50 μm, sufficient heat radiation is obtained in the atmospheric window region.
The thinner the resin material, the higher the heat transfer coefficient and the more effectively the temperature of the object to be cooled can be lowered. 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 making it thinner is other than lowering the heat insulation and making it easier to convey cold heat. It is the suppression of light absorption in the near-infrared region originating from CH, CH ₂ and CH ₃ in the near-infrared region exhibited by resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds and ether bonds. When thinned, the absorption of sunlight by these can be reduced, thus increasing the cooling capacity of the radiative cooling device.
From the above point of view, in the case of a resin containing a carbon-chlorine bond, a carbon-oxygen bond, an ester bond, an ether bond, or a benzene ring, a thickness of 50 μm or less can produce a more effective radiative cooling effect under sunlight. .

In short, according to a further characteristic configuration of the radiation cooling type light shielding device of the present invention, radiation cooling is performed in a resin material having one or more of carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings. can improve effectiveness.

A further characteristic configuration of the radiation-cooled light shielding device of the present invention is that the resin material forming the resin material layer is a resin material having a carbon-silicon bond,
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, even with a thickness of 50 μm, thermal radiation is saturated in the window region of the atmosphere, and even with a thickness of 10 μm, sufficient thermal radiation is obtained in the window region of the atmosphere. The thinner the resin material, the higher the heat transmission coefficient and the more effectively the temperature of the object to be cooled can be lowered. It becomes possible to effectively cool the object to be cooled. Thinning can reduce sunlight absorption, thereby increasing the cooling capacity of the radiative cooling shading device.

From the above point of view, 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 produced more effectively in a solar radiation environment.

In short, according to the further characteristic configuration of the radiation cooling type light shielding device of the present invention, the radiation cooling effect can be improved in the resin material having the carbon-silicon bond.

A further characteristic configuration of the radiation-cooled light-shielding device of the present invention is that the resin material forming the resin material layer is vinyl chloride resin or vinylidene chloride resin,
The thickness of the resin material layer is 100 μm or less and 10 μm or more.

That is, a vinyl chloride resin (polyvinyl chloride) or a vinylidene chloride resin (polyvinylidene chloride) having a thickness of 100 μm or less and 10 μm or more provides sufficient heat radiation in the window region of the atmosphere.
Vinyl chloride resin or vinylidene chloride resin is slightly inferior to fluororesin in terms of its heat radiation characteristics, which can obtain large heat radiation in the window region of the atmosphere, but it is superior to other resin materials such as silicone rubber, and considerably better than fluororesin. Since it is inexpensive, it is effective in constructing an inexpensive radiation cooling device in which the temperature is lower than the ambient temperature under direct sunlight.

Furthermore, since the thin film-like vinyl chloride resin or vinylidene chloride resin is soft, it is hard to be damaged even if it comes into contact with other objects, so that it can be maintained in a beautiful state for a long period of time. Incidentally, since the thin film-like fluororesin is hard, it is easily scratched by contact with other objects, and it is difficult to maintain a beautiful state.
In addition, since vinyl chloride resin is flame-retardant and hardly biodegradable, it is suitable as a resin material for forming a resin material layer of a radiant cooling device for outdoor use.

In short, according to the further characteristic configuration of the radiative cooling type light shielding device of the present invention, it is possible to obtain a radiative cooling layer at a low cost that is less susceptible to damage and whose temperature is lower than the ambient temperature even in a solar environment.

A further characteristic configuration of the radiation-cooled light shielding device 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 reflectance characteristics described above, that is, the reflectance of 90% or more at a wavelength of 0.4 μm to 0.5 μm and the reflectance of 96% or more at a wavelength longer than 0.5 μm. In order to achieve this, it is necessary that the reflective material on the emitting surface side of the light reflective layer is silver or a silver alloy.
In addition, when sunlight is reflected in a state in which only silver or a silver alloy has the reflectance characteristics described above, the thickness must be 50 nm or more.

In short, according to the further characteristic configuration of the radiation-cooling light-shielding device of the present invention, it is possible to appropriately suppress the absorption of sunlight energy by the light reflecting layer and to perform the radiation cooling by the resin material layer satisfactorily.

A further characteristic configuration of the radiation-cooled light shielding device of the present invention is that the light reflecting layer is a laminate of silver or a silver alloy positioned adjacent to the protective layer and aluminum or an aluminum alloy positioned away from the protective layer. It is in the point that it is a structure.

That is, in order to give the light reflection layer the reflectance characteristics described above, it may have a structure in which silver or a silver alloy and aluminum or an aluminum alloy are laminated. Also in this case, the reflecting material on the emitting surface side must be silver or a silver alloy. In this case, the thickness of silver is required to be 10 nm or more, and the thickness of aluminum is required 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 providing appropriate reflectance characteristics.
In other words, while making the expensive silver or silver alloy thinner to reduce the cost of the light reflecting layer, the light reflecting layer has a laminated structure of silver or a silver alloy and aluminum or an aluminum alloy. It is possible to reduce the cost of the light reflecting layer while providing good reflectance characteristics.

In short, according to the further characteristic configuration of the radiation-cooled light shielding device of the present invention, it is possible to reduce the cost of the light reflecting layer while providing appropriate reflectance characteristics.

It is a figure explaining the basic composition of a radiation cooling type light-shielding apparatus. 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 optical absorptance of a resin material, and a wavelength. It is a figure which shows the emissivity spectrum of silicone rubber. FIG. 4 is a diagram showing the emissivity spectrum of PFA; It is a figure which shows the emissivity spectrum of a vinyl chloride resin. FIG. 3 is a diagram showing an emissivity spectrum of ethylene terephthalate resin; FIG. 4 shows the emissivity spectrum of an olefin modified material; It is a figure which shows the relationship between the temperature of a radiation surface, and the temperature of a light reflection layer. FIG. 2 is a diagram showing optical absorption spectra of silicone rubber and perfluoroalkoxy fluororesin; It is a figure which shows the optical absorptance spectrum of ethylene terephthalate resin. FIG. 3 shows the light reflectance spectrum of a silver-based light reflective layer; FIG. 2 shows an emissivity spectrum of fluoroethylene vinyl ether; It is a figure which shows the emissivity spectrum of vinylidene chloride resin. 4 is a table showing experimental results of a radiative cooling layer; It is a figure which shows the specific structure of a radiation cooling type light-shielding apparatus. It is a figure which shows the specific structure of a radiation cooling type light-shielding apparatus. It is a figure which shows the specific structure of a radiation cooling type light-shielding apparatus. It is a figure which shows the specific structure of a radiation cooling type light-shielding apparatus. It is a figure which shows the relationship between the optical absorptance of a resin material, and a wavelength. It is a figure which shows the relationship between the light transmittance of polyethylene, and a wavelength. It is a figure explaining the structure for a test. FIG. 4 is a diagram showing test results when the protective layer is polyethylene. FIG. 10 is a diagram showing test results when the protective layer is UV-absorbing acrylic; FIG. 4 shows the emissivity spectrum of polyethylene; It is a graph which shows the experimental result of a radiation cooling type light-shielding apparatus. It is a graph which shows the experimental result of a radiation cooling type light-shielding apparatus. It is a figure explaining another structure of a radiative cooling layer. It is a figure which shows the structure which formed the radiative cooling layer in uneven|corrugated shape. FIG. 4 is a diagram showing a specific example of unevenness of a radiative cooling layer; FIG. 4 is a diagram showing a specific example of unevenness of a radiative cooling layer; It is a perspective view which shows an awning. 1 is a perspective view showing an awning tent; FIG.

BEST MODE FOR CARRYING OUT THE INVENTION An embodiment of the present invention will be described below with reference to the drawings.
[Basic configuration of radiation cooling type light shielding device]
As shown in FIG. 1, the radiation-cooling light-shielding device W is provided with a light-shielding body M having a radiation-cooling layer CP on the outer surface side, and the sunlight absorptivity of the inner surface of the light-shielding body M is set to 70% or more. there is
Specifically, the light shielding body M includes a radiation cooling layer CP on the outer surface of the main body forming substrate E, and a solar absorbing layer having a solar absorptance of 70% or more on the inner surface of the main body forming substrate E. It is configured in a form with K.

FIG. 1 exemplifies a parasol as the radiation cooling type light shielding device W, and the light shielding member M supported by the aggregate of the parasol is formed as a flexible film-like member.
That is, the light shielding body M is formed in a form in which a flexible radiative cooling layer CP is attached to the outer surface side of the main body forming base material E made of fabric, and is formed as a flexible film-like body, It is configured to be foldable.
The solar absorption layer K is formed by coating the inner surface of the main body forming substrate E with a paint having a solar absorption rate of 70% or more, such as black or dark brown. The sunlight absorption layer K can also be formed by adhering a synthetic resin or cloth film material having a sunlight absorption rate of 70% or more to the inner surface of the main body forming substrate E.

The parasol as the radiation-cooling light-shielding device W is used in a state in which the upper part of the user (light-shielding object) is covered with the light-shielding body M, and the radiation-cooling layer CP is provided, the light shielding member M is cooled by the radiative cooling action of the radiative cooling layer CP. This avoids heating the user (light-shielded object).

In addition, when the light L including sunlight irradiates the ground surface G such as the ground or a concrete road surface, reflection of the sunlight on the ground surface G may occur. Since the ratio is 70% or more, even if the sunlight is reflected on the inner surface of the light shielding member M, most of the sunlight is absorbed. This prevents the sunlight irradiated on the inner surface from reflecting on the inner surface and heating the user (light-shielded object).
Incidentally, the temperature of the light shielding body M rises as it absorbs the sunlight irradiated on its inner surface. An increase in temperature of the body M is avoided.

Therefore, in the parasol as the radiative cooling type light shielding device W, the temperature of the light shielding body M arranged to cover the upper part of the user (light shielding target) is avoided, and moreover, the reflection of the sunlight is prevented from increasing to the light shielding body M Since the user (light shielding object) is prevented from being heated by being reflected on the inner surface of the light, it is possible to suppress the temperature rise of the user (light shielding object) in the daytime sunlight environment.

[Details of radiative cooling layer]
As shown in FIG. 1, the radiation cooling layer CP is positioned on the opposite side of the infrared radiation layer A, which emits infrared light IR from the radiation surface H, and the radiation surface H of the infrared radiation layer A. A light reflective layer B and a protective layer D between the infrared radiation layer A and the light reflective layer B are laminated and formed into a film.
That is, the radiative cooling layer CP is configured as a radiative cooling film.

The light reflecting layer B reflects light L such as sunlight that has passed through the infrared radiation layer A and the protective layer D. is 90% or more, and the reflectance of wavelengths longer than 500 nm is 96% or more.
As shown in FIG. 10, the sunlight spectrum exists from 300 nm to 4000 nm in wavelength, and the intensity increases as the wavelength increases from 400 nm.

In this embodiment, the light L includes ultraviolet light (ultraviolet light), visible light, and infrared light. .01 μm to 20 μm electromagnetic waves). Incidentally, in this document, it is assumed that the wavelength range of ultraviolet light (ultraviolet rays) is between 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 exhibits a reflection characteristic of a reflectance of 96% or more for a wavelength longer than 500 nm. The solar energy absorbed by the reflective layer B can be suppressed to 5% or less, that is, the solar energy absorbed during the mid-summer season can be reduced to about 50W.

The light reflecting layer B is composed of silver or a silver alloy, or composed of a laminated structure of silver or a silver alloy positioned adjacent to the protective layer D and aluminum or an aluminum alloy positioned away from the protective layer D. and flexibility, the details of which will be described later.

The infrared radiation layer A is configured as a resin material layer J having a thickness adjusted to emit thermal radiation energy greater than the absorbed solar energy in a wavelength band of 8 μm to 14 μm, the details of which 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 is Light (sunlight, etc.) transmitted through the resin material layer J and the protective layer D is reflected by the light reflecting layer B and escaped from the radiation surface H to the outside.

Then, the heat input to the radiation cooling layer CP from the main body forming substrate E located on the opposite side of the light reflecting layer B from the side on which the resin material layer J exists (for example, the heat input due to heat conduction from the main body forming substrate E). heat) is converted into infrared light IR by the resin material layer J and radiated, thereby cooling the main body forming base material E. As shown in FIG.

That is, the radiative cooling layer CP reflects the light L irradiated to the radiative cooling layer CP, and also transfers heat to the radiative cooling layer CP (for example, heat transfer from the atmosphere or heat transfer from the main body forming base material E). heat transfer) to the outside as infrared light IR.
In addition, the resin material layer J, the protective layer D, and the light reflecting layer B are flexible, so that the radiation cooling layer CP (radiation cooling film) is flexible.

[Overview of Resin Material Layer]
The resin material forming the resin material layer J changes its light absorption rate and emissivity (light emissivity) depending on its thickness. Therefore, it is necessary to adjust the thickness of the resin material layer J so that it absorbs as little sunlight as possible and emits a large amount of thermal radiation in the so-called atmospheric window wavelength band (wavelength band from 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 average wavelength of the light absorption rate at wavelengths of 0.4 μm to 0.5 μm is 13% or less, and the wavelength is from 0.5 μm to 13%. The wavelength average of light absorption at a wavelength of 0.8 μm is 4% or less, the wavelength average of light absorption from a wavelength of 0.8 μm to a wavelength of 1.5 μm is within 1%, and a wavelength of 1.5 μm to 2.5 μm. It is necessary to adjust the thickness so that the wavelength average of light absorptance from 2.5 μm to 4 μm is 100% or less.
In the case of such an absorptance distribution, the light absorptance of sunlight is 10% or less, which is 100 W or less in terms of energy.

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 is used as a thick film, the emissivity of the atmospheric window becomes approximately 1, and the thermal radiation released into space at that time is 125 W/m ² to 160 W/m ² . The absorption of sunlight by the protective layer D and the light reflecting layer B is 50 W/m ² or less. The sum of the 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 if the atmospheric conditions are good, cooling proceeds. As the resin material forming the resin material layer J, it is preferable to use a resin material having a small light absorptance near the peak value of the sunlight spectrum as described above.

From the viewpoint of infrared radiation (thermal radiation), the thickness of the resin material layer J must be adjusted so that the average wavelength of emissivity at wavelengths from 8 μm to 14 μm is 40% or more.
In order for the thermal energy of the sunlight of about 50 W/m ² absorbed by the protective layer D and the light reflecting layer B to be emitted from the resin material layer J into space by the thermal radiation of the resin material layer J, the thermal radiation of more than that is required. must be provided by the resin material layer J.
For example, when the outside air temperature is 30° C., the maximum thermal radiation of an 8 μm to 14 μm atmospheric window is 200 W/m ² (calculated as an emissivity of 1). This value can be obtained in fine weather in a very dry environment with thin air, such as in high mountains. Since the atmosphere is thicker in lowlands and the like than in high mountains, the wavelength band of the window of the atmosphere becomes narrower and the transmittance decreases. By the way, this phenomenon 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 to the atmosphere is narrow. The thermal radiation generated in the atmospheric window region in low-lying applications is estimated to be 160 W/m ² at 30° C. under good conditions (calculated as an emissivity of 1). In addition, when there is haze in the sky or smog, which is common in Japan, the window of the atmosphere becomes narrower and the radiation to space is about 125 W/m ² .
In view of this situation, the average wavelength of the emissivity in the wavelength range 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 it cannot be used in the lowlands of the mid-latitudes.

Therefore, when the thickness of the resin material layer J is adjusted so as to fall within the range of the optical regulation in view of the above matter, the heat output from the atmospheric window becomes larger than the heat input due to the absorption of sunlight, and the solar radiation environment. Radiative cooling can be done outdoors even at low temperatures.

[Details of resin material]
Resin materials include carbon-fluorine bonds (CF), siloxane bonds (Si-O-Si), carbon-chlorine bonds (C-Cl), carbon-oxygen bonds (CO), ester bonds (R- COO--R), ether bonds (C--O--C bonds), and colorless resin materials containing benzene rings can be used.
FIG. 2 shows the wavelength regions having absorption coefficients in the atmospheric window wavelength band for each resin material (excluding carbon-oxygen bonds).

According to Kirchhoff's law, emissivity (ε) and light absorption (A) are equal. The light absorptance can be obtained from the absorption coefficient (α) by the relational expression A=1-exp(-αt) (hereinafter referred to as the light absorptance relational expression). Note that t is the film thickness.
That is, by adjusting the film thickness of the resin material layer J, a large amount of thermal radiation can be obtained in a wavelength band with a large absorption coefficient. In the case of radiative cooling outdoors, it is preferable to use a material with a large absorption coefficient in the wavelength range of 8 μm to 14 μm, which is the wavelength band of the window of the atmosphere.
Also, in order to suppress the absorption of sunlight, it is preferable to use a material that has no or a small absorption coefficient 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 absorptance, the light absorptance (emissivity) varies depending on the film thickness of the resin material.

In order to lower the temperature from the surrounding atmosphere by radiative cooling in a daytime solar environment with direct sunlight irradiation, it is necessary to have a large absorption coefficient in the window wavelength band of the atmosphere and almost no absorption coefficient in the sunlight wavelength band. If you choose a material that does not have a film thickness, it absorbs little sunlight, but emits a lot of thermal radiation from the atmospheric window. can be done.

As for the carbon-fluorine bond (CF), the absorption coefficient due to CHF and CF ₂ spreads widely over a wide wavelength range from 8 μm to 14 μm, which is the atmospheric window, and the absorption coefficient is particularly large at 8.6 μm. In addition, regarding the wavelength band of sunlight, there is no noticeable absorption coefficient at wavelengths from 0.3 μm to 2.5 μm where the energy intensity is high.

As a resin material having a carbon-fluorine bond (CF),
Polytetrafluoroethylene (PTFE), which is a fully fluorinated resin,
partially fluorinated resins polychlorotrifluoroethylene (PCTFE) and polyvinylidene fluoride (PVDF) and polyvinyl fluoride (PVF),
perfluoroalkoxy fluororesin (PFA), which is a fluorinated resin copolymer;
ethylene tetrafluoride/propylene hexafluoride copolymer (FEP),
ethylene/tetrafluoroethylene copolymer (ETFE),
Ethylene-chlorotrifluoroethylene copolymer (ECTFE) may be mentioned.

Examples of resin materials having siloxane bonds (Si--O--Si) include silicone rubbers and silicone resins.
In this resin, a large absorption coefficient due to expansion and contraction of the C-Si bond appears broadly around the wavelength of 13.3 μm, and an absorption coefficient due to the out-of-plane deformation (pitch) of CSiH ₂ appears at a wavelength of 10 μm. It appears broadly at the center, and the absorption coefficient due to the in-plane deformation angle (scissors) of CSiH ₂ appears small around a wavelength of 8 μm.

As for the carbon-chlorine bond (C--Cl), the absorption coefficient due to the C--Cl stretching vibration appears in a wide band with a half-value width of 1 μm or more around the wavelength of 12 μm.
Examples of resin materials include vinyl chloride resin (PVC) and vinylidene chloride resin (PVDC). In the case of vinyl chloride resin, due to the electron attraction of chlorine, the CH of the alkene contained in the main chain changes. An absorption coefficient derived from angular vibration appears around a wavelength of 10 μm.

An ester bond (R--COO--R) and an ether bond (C--O--C bond) have absorption coefficients from 7.8 μm to 9.9 μm. In addition, a carbon-oxygen bond contained in an ester bond or an ether bond exhibits a strong absorption coefficient over a wavelength band of 8 μm to 10 μm.
When a benzene ring is introduced into the side chain of the hydrocarbon resin, absorption appears widely over the wavelength range of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements under the influence of the benzene ring.

Resins 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-described bonds and functional groups, that is, sunlight absorption. The origin of the absorption of ultraviolet to visible light is electron transitions that contribute to bonding. Absorption in this wavelength range can be found by calculating the binding energy.
First, let us consider the wavelength at which the resin material having a carbon-fluorine bond (CF) has an absorption coefficient in the ultraviolet to visible range. The bond energies of the C—C bond, C—H bond, and C—F bond of the basic structure of polyvinylidene fluoride (PVDF) as a representative are 4.50 eV, 4.46 eV, and 5.05 eV. They correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and absorb light of these wavelengths.

Since the sunlight spectrum consists only of wavelengths longer than 0.300 μm, the use of fluororesin hardly absorbs ultraviolet rays, visible rays, and near-infrared rays of sunlight. The definition of ultraviolet rays is on the side of wavelengths shorter than 0.400 μm, the definition of visible rays is from 0.400 μm to 0.800 μm, the near infrared rays are from 0.800 μm to 3 μm, and the mid-infrared rays are from 3 μm to 8 μm. The far-infrared rays have a wavelength longer than 8 μm.

FIG. 3 shows the absorptance spectrum of PFA (perfluoroalkoxy fluororesin) with a thickness of 50 μm in the ultraviolet to visible region. Although there is a slight increase in the absorptivity spectrum on the shorter wavelength side than 0.4 μm, this increase is only due to the scattering of the sample used for measurement, and the absorptance actually increases. not.

As for the siloxane bond (Si--O--Si) in the ultraviolet region, the bond energy of Si--O--Si in the main chain is 4.60 eV, corresponding to a wavelength of 269 nm. Since the sunlight spectrum consists only of wavelengths longer than 0.300 μm, the majority of siloxane bonds do not absorb ultraviolet rays, visible rays, and near-infrared rays of sunlight.

FIG. 3 shows the absorptance spectrum of silicone rubber having a thickness of 100 μm in the ultraviolet to visible region, and it can be seen that the absorptivity is almost non-existent. Although there is a slight increase in the absorptance spectrum on the shorter wavelength side than the wavelength of 0.4 μm, this increase is only due to the effect of scattering of the sample used for measurement, and in fact the absorptance is not increased.

Regarding the carbon-chlorine bond (C-Cl), the bond energy between carbon and chlorine in alkene 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 region has little absorption.
FIG. 3 shows the absorption spectrum of the vinyl chloride resin with a thickness of 100 μm in the ultraviolet to visible region.
FIG. 3 shows the absorption spectrum of the vinylidene chloride resin having a thickness of 100 μm in the ultraviolet to visible region.

Examples of resins having ester bonds (R-COO-R), ether bonds (C-O-C bonds), and benzene rings include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, ethylene sodium There are phthalate resin and butylene naphthalate resin. For example, acrylic has a C—C bond energy of 3.93 eV and absorbs sunlight with 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 spectrum of a methyl methacrylate resin having a thickness of 5 mm in the ultraviolet to visible region. The exemplified methyl methacrylate resin is generally commercially available and contains a benzotriazole-based ultraviolet absorber.
Since the plate is 5 mm thick, the wavelength with a small absorption coefficient also increases, and light absorption increases on the short wavelength side of 0.38 μm, which is longer than the wavelength of 0.315.

FIG. 3 shows an absorption spectrum of a 40 μm-thick ethylene terephthalate resin in the ultraviolet to visible range as an example of a resin material having these bonds and functional groups.
As shown in the figure, the absorptance increases as the wavelength approaches 0.315 μm, and abruptly increases at the wavelength of 0.315 μm. In addition, as the thickness of ethylene terephthalate resin increases, the absorption rate due to the absorption edge derived from the C—C bond increases on the longer wavelength side than the wavelength of 0.315 μm, similar to the commercially available methyl methacrylate resin. , the absorption rate in ultraviolet rays increases.

If the resin material layer J uses a resin material having the aforementioned characteristics of emissivity (light emissivity) and light absorptance, it may be a single layer film of one kind of resin material or a multilayer film of a plurality of kinds 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 substituted.

[Emissivity of silicone rubber]
FIG. 4 shows the emissivity spectrum in the atmospheric window of silicone rubber having siloxane bonds.
From the silicone rubber, a large absorption coefficient due to the 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 deformation angle (pitch) of CSiH ₂ appears at a wavelength of 10 μm. , and the absorption coefficient due to the in-plane deformation angle (scissors) of CSiH ₂ appears small around the wavelength of 8 μm.
Due to this influence, the wavelength average of the emissivity for a thickness of 1 μm is 80% at wavelengths from 8 μm to 14 μm, which falls within the definition of the wavelength average of 40% or more. As shown, as the film thickness increases, the emissivity in the atmospheric window region increases.

Incidentally, FIG. 4 also shows an emission spectrum when quartz, which is an inorganic material, with a thickness of 1 μm exists on silver. When quartz has a thickness of 1 μm, it has only a narrow-band radiation peak between wavelengths of 8 μm and 14 μm.
If the wavelength of this thermal radiation is averaged over the wavelength range of 8 μm to 14 μm, the emissivity in the wavelength range of 8 μm to 14 μm is 32%, making it difficult to exhibit 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 with a thinner infrared radiation layer A than the conventional technology using an inorganic material as the light reflecting layer B. In other words, when the infrared radiation layer A is made of inorganic materials such as quartz or Tempax glass, the radiation cooling performance cannot be obtained if the thickness of the infrared radiation layer A is 1 μm, but the resin material layer J is used. In the radiative cooling layer CP of the present invention, the radiative cooling performance is exhibited even when the resin material layer J has a thickness of 1 μm.

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

[Emissivity of vinyl chloride resin and vinylidene chloride resin]
FIG. 6 shows the emissivity of a vinyl chloride resin (PVC) as a representative example of a resin having a carbon-chlorine bond at an atmospheric window. Also, FIG. 14 shows the emissivity of a vinylidene chloride resin (PVDC) at an atmospheric window.
As for the carbon-chlorine bond, the absorption coefficient due to the C--Cl stretching vibration appears in a wide band with a half width of 1 μm or more around the wavelength of 12 μm.
In the case of vinyl chloride resin, due to the influence of electron attraction of chlorine, an absorption coefficient derived from bending vibration of C—H of alkene contained in the main chain appears around a wavelength of 10 μm. The same applies to vinylidene chloride resin.
Due to these effects, the wavelength average of the emissivity at a thickness of 10 μm is 43% at wavelengths from 8 μm to 14 μm, which falls within the definition of the wavelength average of 40% or more. As shown, as the film thickness increases, the emissivity in the atmospheric window region increases.

[Ethylene terephthalate resin]
FIG. 7 shows the emissivity at the atmospheric window of ethylene terephthalate resin, which is a typical example of resins having an ester bond or a benzene ring.
The ester bond has an absorption coefficient from 7.8 μm to 9.9 μm. In addition, the carbon-oxygen bond included in the ester bond exhibits a strong absorption coefficient in the wavelength band from 8 μm to 10 μm. When a benzene ring is introduced into the side chain of the hydrocarbon resin, absorption appears widely over a wavelength range of 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements under the influence of the benzene ring.
Due to these influences, the wavelength average of the emissivity at a thickness of 10 μm is 71% at wavelengths from 8 μm to 14 μm, which falls within the definition of the wavelength average of 40% or more. As shown, as the film thickness increases, the emissivity in the atmospheric window region increases.

[Emissivity of olefin modified material]
FIG. 8 includes carbon-fluorine bonds (C-F), carbon-chlorine bonds (C-Cl), ester bonds (R-COO-R), ether bonds (C-O-C bonds), and benzene rings. Figure 2 shows the emissivity spectrum of an olefin-modified material, which is not a component and whose main component is an olefin. A sample was prepared by applying an olefin resin on 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 average wavelength emissivity of the 10 μm-thick emissivity is 27% at wavelengths from 8 μm to 14 μm, which is within the stipulation that the average wavelength is 40% or more. not enter.

The emissivity shown is for an olefin resin modified for application as a bar coater, and for pure olefin resin, the emissivity in the atmospheric window region is also low.
Thus, carbon-fluorine bond (C-F), carbon-chlorine bond (C-Cl), ester bond (R-COO-R), ether bond (C-O-C bond), benzene ring and cannot be radiatively cooled.

[Surface Temperature of Light Reflecting Layer and Resin Material Layer]
Thermal radiation of the atmospheric window of the resin material layer J occurs near the surface of the resin material.
From FIG. 4, in the case of silicone rubber, if it is thicker than 10 μm, the thermal radiation in the atmospheric window region does not increase. In other words, in the case of silicone rubber, most of the thermal radiation in the atmospheric window is generated within a depth of about 10 μm from the surface, and the deeper radiation does not come out.

As can be seen from FIG. 5, in the case of the fluororesin, even if the thickness exceeds 100 μm, there is almost no increase in heat radiation in the atmospheric window region. In other words, in the case of fluororesin, heat radiation in the atmospheric window occurs within a depth of about 100 μm from the surface, and radiation from deeper portions does not come out.
As can be seen from FIG. 6, in the case of vinyl chloride resin, even if the thickness exceeds 100 μm, there is almost no increase in heat radiation in the atmospheric window region. In other words, in the case of vinyl chloride resin, thermal radiation at the atmospheric window occurs within a depth of about 100 μm from the surface, and radiation from deeper portions does not come out.
From FIG. 14, it can be seen that vinylidene chloride resin is similar to vinyl chloride resin.

As can be seen from FIG. 7, in the case of ethylene terephthalate resin, even if the thickness exceeds 125 μm, there is almost no increase in heat radiation in the atmospheric window region. In other words, in the case of ethylene terephthalate resin, heat radiation in the atmospheric window is generated at a depth of about 100 μm from the surface, and radiation at deeper portions does not come out.

As described above, the thermal radiation in the atmospheric window region generated from the surface of the resin material occurs at a depth of approximately 100 μm or less from the surface. The cold heat radiatively cooled in the radiative cooling layer CP is insulated by the resin material that does not contribute to .
Consider forming on the light reflecting layer B a resin material layer J that ideally does not absorb sunlight at all. In this case, sunlight is absorbed only by the light reflecting layer B of the radiative cooling layer CP.
The thermal conductivity of resin materials is generally about 0.2 W/m/K, and when calculating considering this thermal conductivity, if 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 opposite to the side where the resin material layer J exists) rises.

Even if there is an ideal resin material that does not absorb sunlight at all, the thermal conductivity of resin materials is generally about 0.2 W/m/K. is heated by receiving solar radiation, and the main body forming base material E placed on the light reflecting layer side is heated. That is, the thickness of the resin material of the radiative cooling layer CP must be 20 mm or less.

FIG. 9 is a plot of the surface temperature of the radiation surface H of the radiation cooling layer (radiation cooling film) CP and the temperature of the light reflecting layer B calculated assuming Nanchu on a sunny day in western Japan in midsummer. . The sunlight is AM1.5 and has an energy density of 1000 W/m ² . The outside air temperature is 30°C, and the radiant energy is 100W at 30°C although it varies depending on the temperature. The calculation is based on the assumption that the resin material layer does not absorb sunlight. A windless condition is assumed, and the convective heat transfer coefficient is assumed to be 5 W/m ² /K.

[About light absorption rate of silicone rubber, etc.]
FIG. 10 shows the light absorptance of the silicone rubber with a _CH3 side chain and a thickness of 100 μm for the sunlight spectrum, and the light absorptance spectrum of the perfluoroalkoxy fluororesin with a thickness of 100 μm for the sunlight spectrum. . As described above, it can be seen that both resins have almost no light absorptance in the ultraviolet region.

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

The perfluoroalkoxy fluororesin has almost no light absorptance in the wavelength range from 0.3 μm to 2.5 μm, but absorbs light at wavelengths longer than 2.5 μm. However, even if the film thickness of the resin is increased and the light absorptivity on the longer wavelength side than the wavelength of 2.5 μm becomes 100%, the absorbed sunlight energy is about 7W.

Incidentally, when 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 thermal radiation radiated into space in the window area of the atmosphere when used in lowlands is about 160 W/m ² to 125 W/m ² at 30°C. The light absorption in the light reflecting layer B is about 50 W/m ² as defined above, and the light absorption of the light reflecting layer B and the solar light absorption when the silicone rubber or perfluoroalkoxy fluororesin is made into a thick film are added. is smaller than the thermal radiation that radiates into space.
From the above, the maximum film thickness of silicone rubber and perfluoroalkoxy fluororesin is 20 mm from the viewpoint of thermal conductivity.

[About light absorption of hydrocarbon resin]
When the resin material forming the resin material layer J is a resin whose main chain is a hydrocarbon having at least one carbon-chlorine bond, carbon-oxygen bond, ester bond, ether bond, or benzene ring, or silicone In the case of a resin having two or more carbon atoms in the side chain hydrocarbon, in addition to the above-described ultraviolet absorption due to covalent electrons, absorption based on vibrations such as bond bending and stretching is observed in the near-infrared region.

Specifically, the absorption due to the reference tone of the transition to the first excited state of CH ₃ , CH ₂ , and CH from 1.6 μm to 1.7 μm, from 1.65 μm to 1.75 μm, and from 1.7 μm, respectively. appear. Furthermore, absorption by reference tones of CH ₃ , CH ₂ and CH combination tones appears at wavelengths of 1.35 μm, 1.38 μm and 1.43 μm, respectively. Furthermore, overtones of transitions of CH ₂ and CH to the second excited state appear at wavelengths around 1.24 μm. The reference tones for bending and stretching of C—H bonds are distributed over a wide band from 2 μm to 2.5 μm in wavelength.

Further, when having an ester bond (R--COO--R) or an ether bond (C--O--C), there is a large light absorption around a wavelength of 1.9 μm.
According to the above-mentioned optical absorption rate relational expression, the light absorption rate resulting from these factors becomes small and inconspicuous when the film thickness of the resin material is thin, but increases when the film thickness is large.

FIG. 11 shows the relationship between the light absorptance and the sunlight spectrum 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 absorption of light in the wavelength region longer than 1.5 μm caused by each vibration increases.
In addition, the absorption of light not only on the long wavelength side but also on the ultraviolet region to the visible region increases. This is due to the broadening of the light absorption edge caused by the chemical bond.

When the film is thin, the light absorptance increases at the wavelength with the largest absorption coefficient. It will appear. As a result, as the film thickness increases, light absorption from the ultraviolet region to the visible region increases.
At a thickness of 25 μm the absorption of the solar spectrum is 15 W/m ² , at a thickness of 125 μm the absorption of the solar spectrum is 41 W/m ² and at a thickness of 500 μm the absorption of the solar spectrum is 88 W/m 2 . ^m2 .

Since the light absorption of the light reflecting layer B is 50 W/m ² according to the above definition, 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. / ^m2 . The maximum value of infrared radiation in the wavelength band of the window of the atmosphere in the summertime in the lowlands of Japan is about 160 W at 30° C. on a day with good atmospheric conditions, and usually about 125 W, as described above.
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 from 1.5 μm to 4 μm is not the functional group but the vibration of the main chain hydrocarbon, and the hydrocarbon resin exhibits behavior similar to that of ethylene terephthalate resin. In addition, hydrocarbon-based resins have light absorption in the ultraviolet region due to chemical bonding, and exhibit the same behavior as ethylene terephthalate resins in the ultraviolet to visible range.
That is, the hydrocarbon resin behaves similarly to the ethylene terephthalate resin at wavelengths from 0.3 μm to 4 μm. From the above, the film thickness of the hydrocarbon-based resin must be thinner than 500 μm.

[About light absorption of blended resin]
When the resin material is a blend of a resin having a carbon-fluorine bond or a siloxane bond as a main chain and a resin having a hydrocarbon as a main chain, the blended resin having a hydrocarbon as a main chain. Light absorption in the near-infrared region due to CH, CH ₂ , CH ₃ and the like appears depending on the ratio of .
When carbon-fluorine bonds or siloxane bonds are the main component, light absorption in the near-infrared region due to hydrocarbons is reduced, so the thickness can be increased up 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 must be 500 μm or less.

Blends of fluororesins or silicone rubbers with hydrocarbons include fluororesins or silicone rubbers whose side chains are substituted with hydrocarbons, alternating copolymers of fluoromonomers, silicone monomers and hydrocarbon monomers, and random copolymers. , block copolymers, and graft copolymers. Examples of alternating copolymers of fluorine monomers and hydrocarbon monomers include fluoroethylene-vinyl ester (FEVE), fluoroolefin-acrylic acid ester copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), ethylene- Chlorotrifluoroethylene copolymer (ECTFE) may be mentioned.

Light absorption in the near-infrared region due to CH, CH ₂ , CH ₃ and the like appears depending on the molecular weight and proportion of the substituted hydrocarbon side chain. When the monomer introduced as a side chain or copolymerization has a low molecular weight, or when the density of the monomer introduced is low, light absorption in the near-infrared region caused by hydrocarbons becomes small, so from the viewpoint of thermal conductivity. It can be thickened up to the limit of 20 mm in .
When a high molecular weight hydrocarbon is introduced as a side chain of a fluororesin or a silicone rubber or a monomer to be copolymerized, the thickness of the resin must be 500 μm or less.

[Regarding the thickness of the resin material layer]
From the viewpoint of practical use of the radiative cooling layer CP, the thickness of the resin material layer J should preferably be thin. The thermal conductivity of resin materials is generally lower than that of metals, glass, and the like. In order to effectively cool the main body forming substrate E, the film thickness of the resin material layer J should be the minimum necessary. As the film thickness of the resin material layer J increases, the thermal radiation from the atmospheric window increases. When the film thickness exceeds a certain value, the thermal radiation energy from the atmospheric window becomes saturated.

Although the saturated film thickness depends on the resin material, in the case of fluororesin, a film thickness of approximately 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. Furthermore, although thermal radiation is not saturated, sufficient thermal radiation can be obtained in the atmospheric window region even with a thickness of about 100 μm. The thinner the thickness, the higher the heat transmission coefficient and the more effectively lowering the temperature of the main body forming substrate E. Therefore, in the case of fluororesin, the thickness is preferably about 100 μm or less.

The absorption coefficient derived from carbon-silicon bond, carbon-chlorine bond, carbon-oxygen bond, ester bond and ether bond is larger than the absorption coefficient derived from CF bond. Of course, from the viewpoint of thermal conductivity, it is desirable to suppress the film thickness to 300 μm or less rather than 500 μm.
Resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings are saturated even with a thickness of 100 μm, and even with a thickness of 50 μm, sufficient heat radiation occurs in the window region of the atmosphere. can get. The thinner the resin material, the higher the heat transmission coefficient and the more effectively lowering the temperature of the main body forming substrate E. In the case of the containing resin, if the thickness is 50 μm or less, the heat insulating property becomes small and the main body forming substrate E can be effectively cooled. In the case of carbon-chlorine bonds, the body-forming substrate E can be effectively cooled if the thickness is 100 μm or less.

The effect of making it thinner is other than lowering the heat insulation and making it easier to convey cold heat. It is the suppression of light absorption in the near-infrared region originating from CH, CH ₂ and CH ₃ in the near-infrared region exhibited by resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds and ether bonds. When the thickness is reduced, the absorption of sunlight by these can be reduced, so the cooling capacity of the radiative cooling layer CP is increased.
From the above point of view, in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, a thickness of 50 μm or less can produce a more effective radiative cooling effect under sunlight. can.

In the case of the carbon-silicon bond, even with a thickness of 50 μm, thermal radiation is saturated in the window region of the atmosphere, and even with a thickness of 10 μm, sufficient thermal radiation can be obtained in the window region of the atmosphere. The thinner the resin material layer J, the higher the heat transmission coefficient and the more effectively lowering the temperature of the main body forming substrate E. Therefore, in the case of a resin containing a carbon-silicon bond, the thickness should be 10 μm or less. The heat insulating property is reduced, and the main body forming base material E can be effectively cooled. When the thickness is reduced, the absorption of sunlight can be reduced, thereby increasing the cooling capacity of the radiative cooling layer CP.
From the above point of view, 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 more effectively obtained under sunlight.

[Details of light reflecting layer]
In order to give the light reflecting layer B the reflectance characteristics described above, the reflecting material on the side where the radiation surface H exists (the side where the resin material layer J exists) must be silver or a silver alloy.
As shown in FIG. 12, when the light reflecting layer B is composed of silver as a base, the required reflectance of the light reflecting layer B can be obtained.

In the case of reflecting sunlight with the reflectance characteristics described above, the thickness must be 50 nm or more only with silver or a silver alloy.
However, in order to make the light reflecting layer B flexible, the thickness must be 100 μm or less. If it is thicker than this, it will be difficult to bend.
Incidentally, the "silver alloy" is an alloy obtained by adding any of copper, palladium, gold, zinc, tin, magnesium, nickel, and titanium to silver, for example, about 0.4% to 4.5% by mass. can be used. As a specific example, it is possible to use "APC-TR (manufactured by Furuya Metal Co., Ltd.)" which is a silver alloy prepared by adding copper and palladium to silver.

In order to give the light reflecting layer B the reflectance characteristics described above, a structure in which silver or a silver alloy located adjacent to the protective layer D and aluminum or an aluminum alloy located on the side away from the protective layer D are laminated. can 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) must be silver or a silver alloy.
When composed of two layers of silver (silver alloy) and aluminum (aluminum alloy), the thickness of silver is required to be 10 nm or more, and the thickness of aluminum is required to be 30 nm or more.
However, in order to provide flexibility to the light reflecting layer B, the total thickness of silver and aluminum must 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 structural use, yttrium, lanthanum, gadolinium, 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 must be suppressed. Therefore, as shown in FIGS. 16 to 19, a protective layer D for protecting silver is required in a form adjacent to silver or a silver alloy.
Details of the protective layer D will be described later.

[About the experimental results]
A silver layer with a thickness of 300 nm is formed on a glass substrate, and silicone rubber having a siloxane bond, fluoroethylene vinyl ether having a carbon-fluorine bond, olefin-modified material (olefin-modified material), and vinyl chloride resin are coated on the silver with a bar coater. was applied while controlling the film thickness, and the radiative cooling performance was measured.
Evaluation of radiative cooling performance was carried out in late June, when the outside air temperature was 35° C., three hours after the south middle of the day. However, the vinyl chloride resin was tested when the outside air temperature was 29°C. Whether or not the temperature 5 minutes after installation in the jig was lower or higher than the outside air temperature was evaluated as to whether or not there was a radiative cooling effect.
The results of the radiative cooling test are shown in FIG.

Incidentally, the emissivity of the window region of the atmosphere of fluoroethylene vinyl ether is as shown in FIG. The emissivity of silicone rubber is as shown in FIG. 4, the emissivity of olefin-modified material (olefin-modified material) is as shown in FIG. 8, and the emissivity of vinyl chloride resin is shown in FIG. Street.

In the case of silicone rubber having a siloxane bond, it was found that a thickness of 1 μm or more exhibited the radiative cooling ability, as expected from theory.
Fluoroethylene vinyl ether with carbon-fluorine bonds was found to exhibit radiative cooling ability at a film thickness of 5 μm, which is thinner than 10 μm predicted by theory. The reason for this is that not only the light absorption of the atmospheric window 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 atmospheric window is increased more than when each of them is alone.
Olefin modified bodies (olefin-modified materials) do not have radiative cooling capacity because there is little thermal radiation in the window region of the atmosphere.

[Specific Configuration of Radiation Cooling Type Shading Device]
Since the resin material forming the resin material layer J and the protective layer D of the radiative cooling layer CP is flexible, if the light reflecting layer B is made thin, 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, by attaching a film-like radiative cooling layer CP (radiative cooling film) to the outer surface of the main body forming base material E with a connection layer S of adhesive or adhesive, The body-forming substrate E can be cooled. Further, the inner surface of the main body forming base material E is provided with a solar absorption layer K having a solar light rescue rate of 70% or more.
Examples of adhesives or adhesives used for the connection layer S include urethane-based adhesives (adhesives), acrylic adhesives (adhesives), EVA (ethylene vinyl acetate)-based adhesives (adhesives), 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 made in the form of a film. Alternatively, it is conceivable that the protective layer D and the resin material layer J are adhered to the light reflecting layer B which is made in the form of a film. Alternatively, the protective layer D is coated or attached on the resin material layer J formed in a film form, 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, the radiative cooling layer CP (radiative cooling film) in FIG. In the case of a two-layer structure, a protective layer D is formed above the light reflecting layer B, and a resin material layer J is formed above the protective layer D, and below the light reflecting layer B. A lower protective layer Ds is also formed on the side.

As a method for producing the radiative cooling layer CP (radiative cooling film) shown in FIG. It is possible to employ a method of forming the

In the radiation cooling layer CP (radiation cooling film) of FIG. 17, the light reflecting 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 light reflecting layer B, and a resin material layer J is formed on the protective layer D.

As a method for producing the radiative cooling layer CP (radiative cooling film) shown in FIG. A method of integrally molding can be adopted.
As another production method, the resin material layer J is formed into a film, the protective layer D and the silver layer B2 are sequentially applied on the film-shaped resin material layer J, and the aluminum layer B1 is coated with the silver layer. A method of attaching to B2 can be adopted.

The radiation cooling layer CP (radiation cooling film) in FIG. 18 is used when the light reflection layer B is formed as a single layer of silver or a silver alloy, or when it is composed of two layers of silver (silver alloy) and aluminum (aluminum alloy). 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 protective layer D, and a film layer F such as PET is formed on the lower side of the light reflecting layer B. It is what I did.

As a method for producing the radiative cooling layer CP (radiative cooling film) in FIG. B and protective layer D are successively applied and molded integrally, and a separately formed film-like resin material layer J is adhered to protective layer D with glue layer N.
Examples of adhesives (adhesives) used in the glue layer N include urethane adhesives (adhesives), acrylic adhesives (adhesives), EVA (ethylene vinyl acetate) adhesives (adhesives), and the like. It is desirable to have high transparency to sunlight.

The radiation cooling layer CP (radiation cooling film) of FIG. 19 comprises a light reflection layer B composed of an aluminum layer B1 functioning 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 film of PET (ethylene terephthalate resin) or the like, and the protective layer D is formed on the upper side of the silver layer B2. , a resin material layer J is formed on the upper side of the protective layer D.

As a method for producing the radiative cooling layer CP (radiative cooling film) in FIG. A protective layer D and a silver layer B2 are applied 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 adhering in the layer N can be adopted.
Examples of adhesives (adhesives) used in the glue layer N include urethane adhesives (adhesives), acrylic adhesives (adhesives), EVA (ethylene vinyl acetate) adhesives (adhesives), and the like. It is desirable to have high transparency to sunlight.

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

FIG. 20 shows the ultraviolet absorption rate of polyethylene, vinylidene chloride resin, ethylene terephthalate resin, and vinyl chloride resin.
21 shows the light transmittance of polyethylene, which is suitable as a synthetic resin for forming the protective layer D. As shown in FIG.

The radiative cooling layer CP (radiative cooling film) exerts a radiative cooling effect not only at night but also in a solar environment. 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 discoloring under the sunlight environment.

When the protective layer D is formed of polyolefin resin in a form having a thickness of 300 nm or more and 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 protective layer D is made of a synthetic resin having an ultraviolet light absorption rate of 10% or less, it is difficult for the protective layer D to deteriorate due to the absorption of ultraviolet rays.

Since the thickness of the polyolefin 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, the silver or silver alloy forming the light reflecting layer B exhibits a good shielding function such as blocking moisture passing through the resin material layer J from reaching the silver or silver alloy forming the light reflecting layer B. Alternatively, discoloration of the silver alloy can be suppressed.

Incidentally, the protective layer D formed of polyolefin resin deteriorates while forming radicals on the surface side away from the light reflecting layer B due to the absorption of ultraviolet rays. The formed radicals do not reach the light reflecting layer B, and even if it deteriorates while forming radicals, the progress of deterioration is slow due to the low absorption of ultraviolet rays. will be exhibited for a long period of time.

When the protective layer D is made of ethylene terephthalate resin and has a thickness of 17 μm or more and 40 μm or less, the ethylene terephthalate resin has a wavelength of 0.3 μm to 0.4 μm, which is higher than that of the polyolefin resin. However, since the resin material layer J has a thickness of 17 μm or more, the radicals generated in the resin material layer J are transferred to the silver or silver alloy forming the light reflecting layer B. It is possible to satisfactorily exhibit a blocking function over a long period of time, such as blocking moisture from reaching the resin material layer J and blocking moisture passing through the resin material layer J from reaching silver or a silver alloy forming the light reflecting layer. As a result, discoloration of silver or silver alloy forming the light reflecting layer B can be suppressed.

That is, the protective layer D formed of 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 the thickness is 17 μm or more. The formed radicals do not reach the light-reflecting layer B, and even if it deteriorates while forming radicals, the thickness is 17 μm or more, so the above-mentioned shielding function can be exhibited over a long period of time. become.

To explain, 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 progresses sequentially from the surface of the ethylene terephthalate resin (PET) irradiated with ultraviolet rays.

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

Therefore, in order to endure the protective layer D for one year or more in outdoor use, a thickness of about 3 μm is required by adding up 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, the thickness must be 10 μm or more. A thickness of 17 μm or more is required for durability of 5 years or more.

When the protective layer D is formed of polyolefin resin and ethylene terephthalate resin, the reason for setting the upper limit of the thickness is to prevent the protective layer D from exhibiting heat insulation that does not contribute to radiative cooling. be. In other words, the thicker the protective layer D, the more the protective layer D exhibits a heat insulating property that does not contribute to radiative cooling. In order to avoid the

In other words, if the protective layer D becomes thicker, there is no demerit in preventing the silver (silver alloy) of the light reflecting layer B from being colored, but there is a problem in radiative cooling. In other words, increasing the thickness increases the thermal insulation 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, does not contribute to radiative cooling even if it is formed thick because the emissivity of the window to the atmosphere is small, as shown in FIG. On the contrary, increasing the thickness increases the thermal insulation of the radiative cooling material. Next, as the thickness increases, absorption in the near-infrared region derived from vibration of the main chain increases, and the effect of increasing sunlight absorption increases.
Due to these factors, a thick protective layer D is disadvantageous for radiative cooling. From this point of view, the thickness of the protective layer D formed of polyolefin resin is preferably 5 μm or less, more preferably 1 μm.

By the way, as shown in FIG. 18, when the glue layer N is positioned 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. When the thickness of the polyolefin-based resin used to form the protective layer D is 300 nm or more and the thickness of the ethylene terephthalate resin forming the protective layer D is 17 μm or more, the radicals generated in the glue layer N reach the light reflecting layer B. can be suppressed over the long term.

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

As shown in FIG. 24, when the protective layer D is made of an acrylic resin that absorbs ultraviolet rays well, the protective layer D is decomposed by ultraviolet rays to form radicals, and the silver soon turns yellow and ceases to function as the radiative cooling layer CP. (It absorbs sunlight and heats up when exposed to sunlight like other materials).
The 600h line in the figure is the reflectance spectrum after a xenon weather test (ultraviolet light energy of 60W/m ² ) was performed for 600h (hours) under the conditions of JIS standard 5600-7-7. The 0h line is the reflectance spectrum before the xenon weather test.

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

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, etc. No significant drop in reflectance in the visible range is observed.

From the viewpoint of UV absorption, the fluororesin system can also be used as a material for forming the protective layer D. However, when it is actually formed as the protective layer D, it is colored and deteriorated during the formation stage. cannot be used as
In addition, silicone can also be used as a material for forming the protective layer D from the viewpoint of ultraviolet absorption, but it cannot be used as a material for forming the protective layer D because it has extremely poor adhesion to silver (silver alloy).

[Experimental results of radiation cooling type light shielding device]
A test on a parasol as a radiative cooling type shading device W was conducted. Using the following four types of parasols A to D as parasols used in the test, the membrane temperature and sensible temperature were measured from August 29th to 31st.
A: An umbrella with a black outer cloth and a silver inner cloth.
B: Umbrella with a silver outer cloth and a black inner cloth.
C: An umbrella (radiative cooling light shielding device W) having a radiative cooling layer CP on the outside and a black inside (sunlight absorptance of 70% or more).
D: Umbrella with radiative cooling layer CP on the outside and silver on the inside (solar absorption less than 70%).
These four types of umbrellas were arranged at a height of 2 m on the lawn with an interval of 1.5 m.

Then, a T-type thermocouple was attached to the membrane near the center of the umbrella to measure the membrane temperature of the umbrella. At the same time, a blackbody thermometer was attached at a position about 10 cm below the center of the film to measure the sensible temperature.
The blackbody thermometer is a thermometer for measuring the space temperature inside a spherical body with a black surface.

FIG. 26 shows the measurement results of film temperature from August 29th to 31st, and FIG. 27 shows the measurement results of sensible temperature from August 29th to 31st.
Regarding the film temperature, the temperature of the canopy of A rose to nearly 70°C during the daytime, while the temperature of the canopy of B was about 60°C during the daytime. On the other hand, both the C umbrella and the D umbrella were about 35° C., which is about the outside air temperature.

Regarding the sensible temperature, umbrellas A and B are almost the same, umbrella D has a slightly lower temperature than umbrellas A and B, and only umbrella C has a significantly lower sensible temperature. I found out.
The sensible temperatures of the umbrellas A and B are high due to the high membrane temperature, but are lower than the membrane temperature due to the convection (wind) of the outside air.
On the other hand, the sensible temperatures of the umbrellas C and D equipped with the radiative cooling layer CP are the effects of the convection of the outside air, the reflection of sunlight from the ground surface G, and the thermal radiation of the ground surface G. By being affected, it tends to rise above the film temperature, which is low.

In particular, when the sunlight reflectance of the back surface of the umbrella (the inner surface of the umbrella) is high like the umbrella of D, the reflection of the sunlight on the ground surface G reflects and illuminates the person under the umbrella, so the sensible temperature increases. It tends to approach A's umbrella and B's umbrella.
On the other hand, when the sunlight absorption rate of the back side of the umbrella (the inner surface of the umbrella) is high like the umbrella in C, the umbrella absorbs the reflection of sunlight on the ground and prevents it from irradiating people, so the sensible temperature can be significantly reduced.

The reflectance of sunlight on the ground surface G at the test site was 20%, but the reflectance of sunlight on the ground surface G is 40% to 50% depending on the location, and 30%% for the entire earth. is the average. Since the intensity of the sunlight during the zenith is 1000 W/m ² , the reflected light during the zenith is about 200 W/m ² to 500 W/m ² , averaging 300 W/m ² .
In this experiment, a black film that absorbs 90% of the sunlight was used to make the back side (inner side) of the umbrella black. A similar effect can be obtained if a material that absorbs 80% or more, more preferably 90% or more, is used.

[Another configuration of the radiative cooling layer]
As shown in FIG. 28, the radiative cooling layer CP includes an anchor layer Q on top of a film layer F (corresponding to a base material), and on top of the anchor layer Q, a light reflecting layer B, a protective layer D, an infrared It may be configured in a form having a radiation layer A.
In addition, the film layer F (corresponding to the base material) is formed in a film shape with PET (ethylene terephthalate resin) or the like.

The anchor layer Q is introduced to strengthen the adhesion between the film layer F and the light reflecting layer B. In other words, if silver (Ag) is formed directly on the film layer F, there is a risk that it will easily come off. The anchor layer Q is preferably composed mainly of acrylic, polyolefin, or urethane mixed with a compound having an isocyanate group or a melamine resin. It is a coating for parts that are not directly exposed to sunlight, and there is no problem even if it is a material that absorbs ultraviolet rays.
It should be noted that there are methods other than inserting the anchor layer Q as a method for strengthening the adhesion between the film layer F and the light reflecting layer B. FIG. 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 attached to the outer surface of the main body forming base material 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 main body forming substrate E is often not a mirror surface. The outer surface (material surface) of the main body forming base material E, which is different from the mirror surface, often has numerous scratches and irregularities on the order of several μm.
When the unevenness of μm level existing on the outer surface (material surface) of the main body forming base material E is transferred to the light reflecting layer B (silver layer) of the radiation cooling layer CP, the reflectance is lowered.
Therefore, it is necessary to introduce a structure in which the unevenness existing on the outer surface (material surface) is not reflected in the radiative cooling layer CP. , it is preferable to join to the outer surface of the main body forming base material E.

When the connection layer S having a thickness of 5 μm or more made of an adhesive or pressure-sensitive adhesive is present, the connection layer S absorbs the unevenness of the outer surface of the main body forming base material E, and the light reflection layer B (silver layer) of the radiation cooling layer CP. becomes flat.
When the light reflecting layer B (silver layer) becomes flat, a decrease in sunlight reflectance (in other words, an increase in sunlight absorption) can be prevented.
However, when the thickness of the connection layer S is increased, the heat insulating property is improved. If the heat insulation 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 not required, and a thickness of 100 μm is sufficient.

[Another example of radiative cooling layer]
As shown in FIG. 29, the radiation surface H of the radiation cooling layer CP is preferably formed in an uneven shape.
That is, for example, the radiation surface H may be formed in a state in which the convex portion U exists.
Examples of the uneven shape include a line-and-space structure in which rectangular parallelepiped protrusions U are arranged (see FIG. 30), and a structure in which conical protrusions U are arranged vertically and horizontally (see FIG. 31). , a structure in which triangular prisms or pyramid-shaped protrusions U are arranged in a line-and-pace pattern, a structure in which rectangular protrusions U are arranged vertically and horizontally, a structure in which protrusions U are formed at random, etc., can be employed. .
Incidentally, the height difference when forming the radiating surface H in an uneven shape is about 100 μm.

The advantage of forming the radiating surface H in an uneven shape is that the surface area of the radiating surface H is increased, so that, for example, the convection (wind) of the outside air is passed through the radiating surface H, thereby providing a cooling function. can be improved.

Forming the radiating surface H in an uneven shape is also advantageous in terms of appearance. Sunlight is scattered more when the radiation surface H (upper surface) of the radiation cooling layer CP is uneven than when the radiation surface H (upper surface) of the radiation cooling layer CP is a mirror surface. reduced.
Even if the emitting 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 radiative cooling can be performed satisfactorily.

[Another embodiment]
Other embodiments are listed below.
(1) In the above embodiments, various resin materials are exemplified as the resin material forming the resin material layer J. Preferred resin materials include vinyl chloride resin (PVC), vinylidene chloride resin (PVDC), and fluorine. Vinylide resin (PVF) and vinylidene fluoride resin (PVDF) can be mentioned.

(2) In the above embodiment, the protective layer D is provided, but the protective layer D may be omitted.

(3) In the above-described embodiment, the inner surface of the main body forming substrate E is provided with the solar absorption layer K having a solar absorptivity of 70% or more. A configuration in which the outer surface of the material E is provided with the radiative cooling layer CP and the main body forming base material E may be formed of a material having a solar absorptivity of 70% or more may be employed. Examples of materials having a sunlight absorption rate of 70% or more include black synthetic resin films and black fabrics.

(4) In the above embodiment, the parasol was exemplified as the radiative cooling type shading device W. As the radiative cooling type shading device W, the awning 1 (see FIG. 32) installed in an overhang form from the wall surface 1A and the roof portion 2A. There is an awning tent 2 (see FIG. 33) with open side portions, and turf, etc., although not shown, can be mentioned.
In addition, the radiative cooling light shielding device W may be configured by providing the radiative cooling layer CP and the solar light absorbing layer K on an umbrella in which the film material as the main body forming base material E is formed of a synthetic resin material. .
Suitable synthetic resin materials for forming the main body forming base material E include vinyl chloride resin, ethylene terephthalate resin, acrylic resin, and ethylene resin. In addition, fluorine resin and polycarbonate resin can be used. .

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

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

Further, when 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 use hard vinyl chloride resin or semi-rigid vinyl chloride resin. In this case, the vinyl chloride of the emitting layer itself becomes the hard coat layer.

It should be noted that the configurations disclosed in the above embodiments (including other embodiments, the same shall apply hereinafter) can be applied in combination with configurations disclosed in other embodiments as long as there is no contradiction. The embodiments disclosed in this specification are exemplifications, and the embodiments of the present invention are not limited thereto, and can be modified as appropriate without departing from the object of the present invention.

A Infrared radiation layer B Light reflection layer D Protective layer E Main body forming substrate H Radiation surface J Resin material layer

Claims (24)

A radiation-cooling light-shielding device having a light-shielding body provided with a radiation-cooling layer on the outer surface side, wherein the sunlight absorption rate of the inner surface of the light-shielding body is 70% or more. The light shielding body includes the radiation cooling layer on the outer surface of the main body forming substrate, and the solar light absorbing layer having a solar absorptivity of 70% or more on the inner surface of the main body forming substrate. A radiation-cooled shading device according to claim 1. The light shielding body has the radiation cooling layer on the outer surface of the main body forming base material, and the main body forming base material is formed of a material having a solar absorptivity of 70% or more. 2. The radiation-cooled light shielding device according to 1. 4. The radiation cooling type light shielding device according to any one of claims 1 to 3, wherein the light shielding body is formed of a flexible film-like body. 5. The radiation cooling type light shielding device according to any one of claims 1 to 4, wherein the light shielding body is provided in a state of covering the upper side of the light shielding target and opening the side of the light shielding target. The radiative cooling layer comprises an infrared radiation layer that emits infrared light from a radiation surface, and a light reflection layer that is positioned on the side of the infrared radiation layer opposite to the side on which the radiation surface exists. ,
The infrared radiation layer is a resin material layer having a thickness adjusted to emit thermal radiation energy larger than the absorbed solar energy in a wavelength band of 8 μm to 14 μm,
wherein the light reflective layer comprises silver or a silver alloy;
3. The radiation-cooling light shielding device according to claim 2, wherein the sunlight absorption layer has a sunlight absorption rate of 70% or more. configured to include a protective layer between the infrared emitting layer and the light reflecting layer;
7. The radiative cooling light shielding device according to claim 6, wherein the protective layer is a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, or a polyethylene terephthalate resin with a thickness of 17 μm or more and 40 μm or less. 8. A radiative cooling light shielding device according to claim 6 or 7, wherein said radiative cooling layer is attached to the outer surface of said light shielding body with a connecting layer of adhesive or pressure sensitive adhesive. 9. The radiation cooling light shielding device according to claim 6, wherein the radiation surface of the radiation cooling layer is uneven. 10. The light reflecting layer according to any one of claims 6 to 9, 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 96% or more at a wavelength longer than 0.5 μm. Radiative cooling shading device. The film thickness of the resin material layer is
The average wavelength of light absorptance at a wavelength of 0.4 μm to 0.5 μm is 13% or less, the average wavelength of light absorptance at a wavelength of 0.5 μm to 0.8 μm is 4% or less, and the wavelength from 0.8 μm The wavelength average of the light absorption rate up to a wavelength of 1.5 μm is within 1%, and the light absorption characteristic is such that the wavelength average of the light absorption rate from 1.5 μm to 2.5 μm is 40% or less, and
11. The radiative cooling light shielding device according to claim 6, wherein the thickness is adjusted so as to provide thermal radiation characteristics such that the average wavelength of emissivity from 8 μm to 14 μm is 40% or more. The resin material forming the resin material layer is selected from resin materials having one or more of carbon-fluorine bond, siloxane bond, carbon-chlorine bond, carbon-oxygen bond, ether bond, ester bond, and benzene ring. The radiation cooling type light shielding device according to any one of claims 6 to 11. A main component of a resin material forming the resin material layer is siloxane,
13. The radiation cooling type light shielding device according to claim 6, wherein the resin material layer has a thickness of 1 μm or more. 13. The radiation cooling light shielding device according to claim 12, wherein the resin material layer has a thickness of 10 [mu]m or more. 15. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 20 mm or less. 16. The radiation cooling type light shielding device according to claim 15, 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 main chain having one or more of carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, or a side A silicone resin in which the number of carbon atoms in the chain hydrocarbon is 2 or more,
15. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 500 μm or less. The resin material forming the resin material layer is a blend of a resin containing carbon-fluorine bonds and siloxane bonds and a resin having a hydrocarbon main chain, and the thickness of the resin material layer is 500 μm or less. 15. The radiation-cooled light shielding device according to any one of 6 to 14. The resin material forming the resin material layer is a fluororesin,
15. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 300 μm or less. The resin material forming the resin material layer is a resin material having one or more of carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings,
15. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 50 μm or less. The resin material is a resin material having a carbon-silicon bond,
15. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 10 μm or less. The resin material forming the resin material layer is vinyl chloride resin or vinylidene chloride resin,
12. The radiation cooling light shielding device according to claim 6, wherein the resin material layer has a thickness of 100 μm or less and 10 μm or more. 23. The radiation cooling light shielding device according to claim 6, wherein the light reflecting layer is made of silver or a silver alloy and has a thickness of 50 nm or more. 23. The light reflecting layer according to any one of claims 7 to 22, wherein the light reflecting layer has a laminated structure of silver or a silver alloy positioned adjacent to the protective layer and aluminum or an aluminum alloy positioned away from the protective layer. radiation cooled shading device.

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