Temperature increase-suppressing member

Abstract

This temperature increase-suppressing member is obtained by a retroreflective body being adhered to a base material surface.　The retroreflective body is exposed from the adhesive layer and adhered to the base material surface, and thus it is possible to provide a temperature increase-suppressing member capable of efficiently reflecting incident near-infrared rays and suppressing a temperature increase.

Description

Temperature rise suppression material

[0001] The present invention relates to a temperature rise suppressing member, and more particularly to a temperature rise suppressing member that reflects near-infrared rays.

[0002] Windows are one of the routes through which heat can enter the interior of a car or building. In particular, in the case of a car, a large amount of heat enters through the windshield and rear window, and this heat warms interior materials such as the dashboard.

[0003] The heat emitted from these interior materials warms the air inside the car, so if the car is parked in the hot sun, the interior will become very hot, not only making passengers uncomfortable immediately after getting in, but also causing the air conditioner to consume a lot of energy to lower the temperature inside the car to a comfortable level.

[0004] For this reason, it is desirable to reflect the heat energy that flows into the vehicle interior to suppress the temperature rise inside the vehicle and reduce the energy consumption of the air conditioner.

[0005] Patent Document 1 discloses a radiative cooling functional paint in which a granular filler with high reflectivity to near-infrared rays is distributed in a radiative cooling resin with low solar energy absorption.

[0006] Japan Special Table No. 2021-528502

[0007] However, in the case of the coating described in Patent Document 1, since the granular filler is dispersed in the radiative cooling resin, near-infrared rays that enter the coating film of the radiative cooling functional paint first enter the radiative cooling resin, and the part of the near-infrared rays that is not absorbed by the radiative cooling resin is simply reflected by the granular filler, making it impossible to efficiently suppress temperature rise.

[0008] The present invention has been made in consideration of the problems associated with the prior art, and its purpose is to provide a temperature rise suppression member that can efficiently reflect near-infrared rays and suppress temperature rise.

[0009] As a result of extensive research into achieving the above-mentioned objective, the inventors discovered that by arranging a retroreflector exposed on the surface of a component, near-infrared rays incident on the temperature rise suppression component can be efficiently reflected, thereby achieving the above-mentioned objective, and thus completed the present invention.

[0010] That is, the temperature rise suppressing member of the present invention is formed by adhering a retroreflector to the surface of a substrate, and the retroreflector is exposed from the adhesive layer and adhered to the surface of the substrate.

[0011] According to the present invention, by exposing the retroreflector on the surface of the temperature rise suppression member, it is possible to provide a temperature rise suppression member that can efficiently reflect incident near-infrared rays and suppress temperature rise.

[0012] 1 is a cross-sectional view of a main part of a temperature rise suppressing member; 2 is a graph showing temperature rises of the temperature rise suppressing members of Examples and Comparative Examples;

[0013] The temperature-rise suppressing member of the present invention will be described in detail. The temperature-rise suppressing member of the present invention has a retroreflector on the surface of a substrate, and this retroreflector reflects near-infrared rays that are incident on the temperature-rise suppressing member, thereby suppressing a rise in the temperature of the substrate.

[0014] The retroreflector reflects near-infrared rays over the entire wavelength range of 780 nm to 3 μm, and suppresses the temperature rise of the retroreflector itself due to the incidence of near-infrared rays, thereby suppressing heat transfer from the retroreflector to the substrate.

[0015] Furthermore, as shown in the top of Figure 1, in the temperature rise suppression member of the present invention, the retroreflector is exposed on the surface without being embedded in the substrate, so the area of ​​the retroreflector accounts for a large proportion of the surface area of ​​the temperature rise suppression member onto which near-infrared rays can enter.

[0016] Therefore, compared to a case where the retroreflector is embedded in the adhesive layer or substrate, as shown at the bottom of Figure 1, the amount of near-infrared light that directly enters other parts other than the retroreflector, such as the adhesive layer, is reduced.

[0017] Therefore, the temperature rise suppression member of the present invention has a high proportion of incident near-infrared rays that enter the retroreflector and a low proportion that enters other parts, and therefore reflects and absorbs a small proportion of near-infrared rays, which, combined with the temperature rise suppression effect of the retroreflector itself, has a great effect in suppressing temperature rise.

[0018] The compound forming the retroreflector or adhesive layer is preferably a compound formed with a bond that does not absorb in the near-infrared region. Examples of such bonds include Si—O bonds, Si—Si bonds, Si—C bonds, C—F bonds, Ga—O bonds, and Zr—O bonds.

[0019] When the retroreflector or the adhesive layer is made of a compound having 40% or more of at least one type of bond selected from the above bonds, the effect of suppressing temperature rise is improved.

[0020] In the present invention, the proportion of the above bonds in a compound can be calculated by dividing the total number of bonds by the total number of bonds in the compounds that form the retroreflector or adhesive layer × 100. For example, the proportion of the above bonds in a compound having the following structure can be calculated as follows when n is 132:

[0021] SiO bond: 2+132×2=266 Si-C bond: 6+132×2=270 C-H bond: 3×6+132×6=810 (266+270) / (266+270+810)×100=40%

[0022] It is preferable that 28% or more of the surface area of ​​the retroreflector is exposed. By having 28% or more of the retroreflector exposed and in contact with air, the reflectance of near-infrared rays can be further improved.

[0023] There is no particular upper limit to the exposure ratio as long as the retroreflector does not detach from the substrate. Although this depends on the adhesive layer, if the exposure ratio is less than 56%, the retroreflector and the substrate can be firmly bonded together.

[0024] The substrate and the retroreflector can be bonded together by an adhesive layer formed by applying an adhesive to the surface of the substrate, and the exposed ratio of the retroreflector can be adjusted by the film thickness of the adhesive layer and the particle size of the retroreflector. Specifically, it is preferable that the thickness of the adhesive layer is 5 to 46 μm and the volume average particle size of the retroreflector is 38 to 106 μm.

[0025] The retroreflector preferably has a refractive index of 1.9% or more. By having a refractive index of 1.9% or more for near-infrared light with a wavelength of 780 nm, the reflectance can be increased.

[0026] In other words, if the refractive index of a retroreflector is large, the light incident on the retroreflector is refracted greatly at the interface between the retroreflector and air, and the distance to the focal point becomes short, so that the light reaches the opposite side of the retroreflector, i.e., the interface between the retroreflector and the substrate, at an angle. As a result, the reflection at the opposite interface becomes large, and less near-infrared light passes through the retroreflector and reaches the substrate.

[0027] Therefore, the diameter of the retroreflector can be reduced, making the retroreflector less noticeable when viewed from an angle different from the direction of light incidence, and allowing the color of the substrate to be seen.

[0028] Examples of materials with a high refractive index include silicon dioxide (SiO ２ ), aluminum oxide, zinc oxide, zirconium oxide, cerium oxide, lanthanum oxide, rhodium oxide, barium sulfate, titanium oxide, calcium carbonate, zinc sulfide, magnesium oxide, and aluminum silicate.

[0029] The shape of the retroreflector may be spherical, fibrous, cubic, tetrahedral or prismatic, and among these, spherical retroreflectors are preferred because of their high reflectivity.

[0030] Furthermore, for the adhesive layer, a transparent adhesive that has little absorption of near-infrared rays can be used, and examples thereof include silicone oligomers such as polydimethylsiloxane, silicone resins, and glass coatings.

[0031] As described above, the temperature rise suppression member of the present invention can suppress temperature rise by reflecting near-infrared rays, so it can suppress temperature rise even if the base material has a black resin surface that absorbs visible light and near-infrared rays and is prone to temperature rise.

[0032] Furthermore, the temperature rise suppression member of the present invention has a retroreflector on its surface, which suppresses regular reflection on the surface of the temperature rise suppression member. Therefore, when applied to a vehicle dashboard, light from outside the vehicle is reflected in the direction of incidence and does not enter the vehicle interior, thereby not only suppressing temperature rise but also preventing window reflections on the windshield and glare for the driver, thereby ensuring clear visibility.

[0033] The present invention will be described in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0034] Example 1 0.7 g of a hexane solution containing 50% by mass of polydimethylsiloxane (KR-4000F2: manufactured by Shin-Etsu Chemical Co., Ltd.) was spray coated onto a black acrylic resin plate and dried at room temperature for 30 minutes to form an adhesive layer in the process of drying.

[0035] On the adhesive layer during drying, spherical SiO ２ 0.8 g of a retroreflector (refractive index: 1.9, particle size distribution in the particle size range of 38-45 μm: UB-R02M: manufactured by Unitika Ltd.) was sprinkled on the surface and dried at room temperature for 30 minutes to prepare a temperature rise suppressing member.

[0036] In this temperature rise suppressing member, the exposed ratio of the retroreflector was 28%, and the film thickness of the adhesive layer was 23 μm.

[0037] Comparative Example 1 A retroreflector was sprinkled onto the adhesive layer during drying, and then 0.7 g of a hexane solution containing 50% by mass of polydimethylsiloxane (KR-4000F2, manufactured by Shin-Etsu Chemical Co., Ltd.) was spray-coated to cover the retroreflector. A temperature rise suppression member was produced in the same manner as in Example 1.

[0038] In this temperature rise suppressing member, the exposed ratio of the retroreflector was 0%, and the film thickness of the adhesive layer was 47 μm.

[0039] Comparative Example 2 A temperature rise suppressing member was produced in the same manner as in Example 1, except that no retroreflectors were sprinkled on the member.

[0040] <Evaluation> The temperature rise suppressing members of the above examples and comparative examples were irradiated with a halogen lamp, and the rear surface temperature of the temperature rise suppressing member was measured with a thermocouple. The evaluation results are shown in FIG.

[0041] From the results in Figure 2, it was confirmed that Example 1 had a temperature drop of 3.1°C lower than Comparative Example 1 and a temperature drop of 7.9°C lower than Comparative Example 2, and that the retroreflector being exposed from the adhesive layer improved the effect of suppressing temperature rise due to near-infrared irradiation.

[0042] REFERENCE SIGNS LIST 1 Temperature rise suppression member 2 Retroreflector 3 Base material 4 Adhesive layer

Claims

1. A temperature rise suppression member comprising a retroreflector adhered to the surface of a substrate, the retroreflector reflecting near-infrared light having a wavelength of 780 nm to 3 μm, and the retroreflector exposed from the adhesive layer and adhered to the surface of the substrate.

2. The temperature rise suppression member according to claim 1, characterized in that 28% or more of the surface area of ​​the retroreflector is exposed.

3. A temperature rise suppression member as described in claim 1, characterized in that the refractive index of the retroreflector is 1.9% or more and its shape is spherical.

4. The temperature rise suppression member according to claim 3, characterized in that the adhesive layer has a thickness of 5 to 46 μm, and the particle size distribution of the retroreflector is in the particle size range of 38 to 106 μm.

5. The temperature rise suppression member according to claim 1, characterized in that the compound forming the retroreflector and the adhesive layer is made of a compound having 40% or more of at least one bond selected from the group consisting of Si-O bonds, Si-Si bonds, C-F bonds, Ga-O bonds and Zr-O bonds.

6. The temperature rise suppressing member according to claim 1, characterized in that the adhesive layer is formed from polydimethylsiloxane.

7. The temperature rise suppressing member according to claim 1, characterized in that the base material is a black resin.

8. The temperature rise suppressing member according to any one of claims 1 to 6, which is a dashboard for a vehicle.

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