Glass composite

Abstract

To enhance electromagnetic wave transmittance and light transmission while reducing reflection at nighttime or the like.SOLUTION: A glass composite W comprises an infrared-emitting glass layer G1 that emits infrared light from a first emission surface H1 serving as an emission surface H, and a light-reflecting layer B located on the side opposite to the presence side of the first emission surface H1 in the infrared-emitting glass layer G1, with those layers laminated in this order. The light-reflecting layer B includes a thick portion B3 in a laminating direction Z and a thin portion B2 having a thickness in the laminating direction that is less than or equal to two-thirds the thickness of the thick portion B3. The thin portion B2 includes a first metal thin portion that is continuously and integrally provided in a plan view orthogonal to the first emission surface H1 and has a planar area of 5 cm2 or more in the plan view, and a second metal thin portion B2 that is continuously and integrally provided in the plan view and has a planar area smaller than that of the first metal thin portion.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a glass composite having an infrared emitting glass layer and exhibiting radiative cooling function. [Background technology]

[0002] Radiative cooling is known as a function for cooling objects. Radiative cooling is a phenomenon in which a substance's temperature drops when it radiates electromagnetic waves such as infrared rays into its surroundings. By utilizing this phenomenon, it is possible to realize, for example, a hybrid cooling device that cools an object without consuming energy such as electricity.

[0003] Patent Document 1 discloses a glass composite in which a high-emissivity coating layer that emits infrared light from its radiation surface and a low-emissivity coating layer that reflects light are laminated on a glass substrate. Here, it is noted that the low-emissivity coating layer includes a shielding layer that blocks infrared and ultraviolet rays, and that the shielding layer is made of a metal material such as silver. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2022-543529 Summary of the Invention [Problem to be solved by the invention]

[0005] When a glass composite has a shielding layer made of a metal material such as silver, as in the glass composite disclosed in Patent Document 1, for example, in a structure such as a vehicle having a window that separates an external area from an internal area with the glass composite, there are problems such as the blocking of electromagnetic waves used for communication between the external area and the internal area, poor light transmission from the external area to the internal area, and increased reflection when viewing the external area from the internal area through the glass composite at night. However, the technology disclosed in Patent Document 1 does not recognize this problem, and there is room for improvement.

[0006] The present invention has been made in view of the above-mentioned problems, and an object of the present invention is to provide a glass composite that can improve electromagnetic wave transmittance and daylighting properties and can reduce glare at night, etc. [Means for solving the problem]

[0007] The glass composite to achieve the above object has the following characteristic configuration: a glass composite comprising: an infrared radiation glass layer that emits infrared light from a first radiation surface that is a radiation surface; and a light reflecting layer that is located on an opposite side of the infrared radiation glass layer from a side where the first radiation surface is present, stacked in the order described; the light reflecting layer has a thick portion in a stacking direction and a thin portion whose thickness in the stacking direction is 2 / 3 or less of the thickness of the thick portion, The thin portion is provided continuously and integrally in a plan view perpendicular to the first radiation surface, and has an area of ​​5 cm 2 a first metal thin portion having an area equal to or greater than the area of ​​the first metal thin portion, and a second metal thin portion provided integrally and continuously in the plan view and having an area in the plan view less than the area of ​​the first metal thin portion, The second thin metal portion is provided in a plurality of portions in a dispersed and distributed manner in the plan view, The overall surface average solar reflectance is 40% or more, and the surface average emissivity, which is the wavelength average of the emissivity of infrared light in the range of 8 μm to 13 μm, is 80% or more.

[0008] According to the above characteristic configuration, the light reflecting layer has a thick portion having a large thickness in the stacking direction and a thin portion having a thickness in the stacking direction that is 2 / 3 or less of the thickness of the thick portion, and the thin portion is provided continuously and integrally in a plan view perpendicular to the first radiation surface and has an area of ​​5 cm in a plan view. 2Since the glass composite has a first thin metal portion with the above area, by setting the thickness of the first thin metal portion to an appropriate thickness that allows electromagnetic waves for communication to pass through, it becomes possible to communicate via electromagnetic waves through the glass composite. Furthermore, as the thin-walled portion of the light-reflecting layer, a plurality of second thin-walled metal portions are provided as continuous, integral portions in a planar view and whose area in a planar view is less than the area of ​​the first thin-walled metal portion, and are provided in a dispersed and distributed form in a planar view, so that a predetermined amount of light can be obtained through the glass composite in a dispersed form in the surface direction along the radiating surface. Furthermore, the second thin metal portions, which are provided in a dispersed manner in a plan view, have a smaller area in a plan view than the first thin metal portions, so that a certain degree of reflectivity can be ensured as a light reflective layer. With the above-described configuration, a glass composite can be realized that has an overall surface average solar reflectance of 40% or more and an average surface emissivity, which is the wavelength average of the emissivity of infrared light of 8 μm or more and 13 μm or less, of 80% or more, thereby improving electromagnetic wave transmittance and daylighting properties and reducing glare at night, etc.

[0009] Further characteristic features of the glass composite include: In the stacking direction, the thickness of each of the first thin metal portion and the second thin metal portion is 0 nm or more and 50 nm or less, and more preferably 0 nm or more and 10 nm or less.

[0010] The inventors have determined that the thickness of the first metal thin portion in the product direction is 50 nm or less, and that the area in plan view is 5 cm2 as described above. 2 It has been confirmed that by doing the above, electromagnetic waves for communication can be transmitted well and communication can be carried out. Furthermore, by having a certain area ratio of thick sections and making the thickness of the second metal thin section in the product direction 50 nm or less, it has been confirmed that the glass laminate as a whole can achieve an average surface solar reflectance of 40% or more while also achieving appropriate lighting properties.

[0011] Further characteristic features of the glass composite include: In the plan view, the area of ​​the second metal thin portion is 0.03 cm 2 That's all there is to it.

[0012] The inventors have determined that the area of ​​the second metal thin section is 0.03 cm 2 It has been confirmed that if the thickness is less than this, it is difficult to obtain sufficient light transmission throughout the glass laminate, even if the number of second thin metal portions is increased to the extent that the light-reflecting layer can be maintained as a thin metal film.

[0013] Further characteristic features of the glass composite include: a protective layer for protecting the light reflecting layer on the side of the light reflecting layer opposite to the side where the infrared radiation glass layer is present; The protective layer is an auxiliary infrared emitting layer that emits infrared light from a second emitting surface, which is an emitting surface on the opposite side to the side where the light reflecting layer is present.

[0014] According to the above characteristic configuration, a protective layer for protecting the light reflecting layer is provided on the side of the light reflecting layer opposite to the side on which the infrared radiation glass layer is present. Therefore, even if the light reflecting layer is made of, for example, a metal vapor deposition film that is vulnerable to external forces, the protective layer prevents the light reflecting layer from being exposed to external forces, and therefore the light reflecting layer can be effectively prevented from peeling off due to external forces. Furthermore, by appropriately selecting the resin material for forming the above-mentioned protective layer, the protective layer can function as an auxiliary infrared radiation layer capable of emitting infrared light, thereby realizing a glass composite that can also emit infrared light from the second radiation surface opposite to the first radiation surface.

[0015] Further characteristic features of the glass composite include: a rear glass layer on the side of the auxiliary infrared radiation layer opposite to the side on which the light reflecting layer is present; the rear surface glass layer is an infrared radiation rear surface glass layer that emits infrared light from a third radiation surface, which is an radiation surface on the opposite side to the side on which the auxiliary infrared radiation layer is present, The intermediate resin that bonds the auxiliary infrared radiation layer and the infrared radiation rear glass layer is made of at least one of polyvinyl butyral, polyethylene vinyl acetate, and polyurethane.

[0016] In the glass composite described above, a back surface glass layer may be provided on the side opposite to the side where the light reflecting layer of the auxiliary infrared emission layer is present, and the back surface glass layer may be an infrared emission back surface glass layer that emits infrared light from the third emission surface, which is the emission surface on the side opposite to the side where the auxiliary infrared emission layer is present, thereby making it possible to obtain a glass composite having laminated glass. Here, by using one or more of polyvinyl butyral, polyethylene vinyl acetate, and polyurethane as the intermediate resin that bonds the auxiliary infrared radiation layer and the infrared radiation back surface glass layer, it is possible to achieve good adhesion between the auxiliary infrared radiation layer and the infrared radiation back surface glass layer while appropriately maintaining the radiative cooling function.

[0017] A further characteristic configuration of the glass composite is that the infrared emitting glass layer is The glass is made of at least one of alkali-free glass, soda-lime glass, alkali borosilicate glass, and acrylic resin glass.

[0018] Further characteristic features of the glass composite include: The infrared radiation glass layer and the infrared radiation back surface glass layer are The glass is made of at least one of alkali-free glass, soda-lime glass, alkali borosilicate glass, and acrylic resin glass.

[0019] By selecting the materials in this way, the infrared-emitting glass layer or the infrared-emitting back surface glass layer can function well as an infrared-emitting layer that emits infrared rays. Furthermore, when connecting with the above-mentioned intermediate resin, hydroxyl groups in the infrared-emitting glass layer or the infrared-emitting back surface glass layer can be bonded to hydroxyl groups in the intermediate resin, thereby achieving good adhesion.

[0020] Further characteristic features of the glass composite include: In the plan view, The ratio of the area of ​​the thin portion to the entire area of ​​the light reflecting layer is 1% or more and 50% or less.

[0021] According to the above characteristic configuration, a glass composite having an overall surface average solar reflectance of 40% or more can be successfully realized.

[0022] Further characteristic features of the glass composite include: the light reflecting layer is a metal vapor-deposited layer formed by vapor-depositing a metal on the side of the infrared radiation glass layer opposite to the side on which the first radiation surface is present, The metal is at least one of silver, a silver alloy, aluminum, an aluminum alloy, and a copper alloy.

[0023] As described above, by using at least one of silver, a silver alloy, aluminum, an aluminum alloy, and a copper alloy as the light reflecting layer, which is vapor-deposited on the side of the infrared radiation glass layer opposite to the side where the first radiation surface is present, there is no need to bond the light reflecting layer and the infrared radiation glass layer with a resin material or the like, and therefore the glass laminate can be realized by a relatively simple manufacturing process.

[0024] Further characteristic features of the glass composite include: The auxiliary infrared radiation layer has a light-controlling layer on the side opposite to the side where the light-reflecting layer is present.

[0025] Further characteristic features of the glass composite include: The infrared radiation rear surface glass layer has a light control layer having a light control function on the side opposite to the side on which the auxiliary infrared radiation layer is present.

[0026] As explained above, the glass composite of the present invention has an overall surface average solar reflectance of 40% or more by providing thin sections in the light-reflecting layer, so it is expected that in some cases, the amount of light passing through the gas composite may be too great. As described above, by having a dimming layer with dimming function, it is possible to adjust the light transmission by increasing the amount of light attenuation by the dimming layer, for example, when the amount of light passing through the glass composite is too large. [Brief explanation of the drawings]

[0027] [Figure 1]1A and 1B are schematic cross-sectional views of a glass composite and a vehicle as a structure including the glass composite; [Figure 2] 10A and 10B are diagrams for explaining the sequential sputtering of a material for a light reflecting layer and a material for an infrared emitting layer onto an infrared emitting glass. [Figure 3] 1 is an example of a plan view of a glass composite (or a light-reflecting layer). [Figure 4] FIG. 10 is a diagram showing a schematic cross-sectional configuration of another embodiment of a glass composite. [Figure 5] FIG. 10 is a diagram showing a schematic cross-sectional configuration of another embodiment of a glass composite. [Figure 6] FIG. 10 is a diagram showing a schematic cross-sectional configuration of another embodiment of a glass composite. [Figure 7] FIG. 10 is a diagram showing a schematic cross-sectional configuration of another embodiment of a glass composite. [Figure 8] FIG. 2 is a diagram showing a schematic cross-sectional configuration of a glass composite according to a comparative example. [Figure 9] FIG. 10 is a diagram showing the relationship between the absorption coefficient of a resin material and a wavelength band. [Figure 10] FIG. 10 is a diagram showing the relationship between the light absorptance of a resin material and wavelength. [Figure 11] FIG. 1 is a diagram showing the emissivity spectrum of silicone rubber. [Figure 12] FIG. 1 is a diagram showing the emissivity spectrum of PFA. [Figure 13] FIG. 1 is a diagram showing the emissivity spectrum of vinyl chloride resin. [Figure 14] FIG. 1 is a diagram showing the emissivity spectrum of ethylene terephthalate resin. [Figure 15] FIG. 1 is a diagram showing the emissivity spectrum of an olefin-modified material. [Figure 16] FIG. 10 is a diagram showing the relationship between the temperature of the radiation surface and the temperature of the light reflecting layer. [Figure 17] FIG. 1 is a diagram showing the light absorptance spectra of silicone rubber and perfluoroalkoxy fluororesin. [Figure 18] FIG. 1 is a diagram showing the light absorptance spectrum of ethylene terephthalate resin. [Figure 19] FIG. 1 shows the light reflectance spectrum of a silver-based light-reflecting layer. [Figure 20] FIG. 1 shows the emissivity spectrum of fluoroethylene vinyl ether. [Figure 21] FIG. 1 is a diagram showing the emissivity spectrum of vinylidene chloride resin. [Figure 22] 10 is a table showing experimental results. [Figure 23] FIG. 10 is a diagram showing the relationship between the light absorptance of a resin material and wavelength. [Figure 24] FIG. 1 is a diagram showing the relationship between light transmittance and wavelength of polyethylene. [Figure 25] FIG. 1 is a diagram illustrating a test configuration. [Figure 26] FIG. 10 is a diagram showing test results when the protective layer is made of polyethylene. [Figure 27] FIG. 10 is a diagram showing test results when the protective layer is made of ultraviolet absorbing acrylic. [Figure 28] FIG. 1 shows the emissivity spectrum of polyethylene. DETAILED DESCRIPTION OF THE INVENTION

[0028] The glass composite W according to the embodiment of the present invention can improve electromagnetic wave transparency and lighting properties, and can also reduce glare at night and other times. Hereinafter, an embodiment of the glass composite W will be described with reference to the drawings.

[0029] As shown in Fig. 1 , the glass composite W is preferably provided, for example, as window glass fitted into a frame C1 of a vehicle C, which serves as a structure that separates an internal space IS from an external environment OS. The window may be a front window, rear window, side window, sunroof, or the like of the vehicle C. Other examples of structures include commercial buildings and residential buildings, and the glass composite W can be suitably used as window glass for these. In this embodiment, the side of the atmosphere from which infrared rays are radiated is the side indicated by the arrow in the stacking direction Z.

[0030] As shown in FIG. 1 , the glass composite W includes an infrared-emitting glass layer G1 that emits infrared light from a first emission surface H1, which is an emission surface H, and a light-reflecting layer B that is located on the infrared-emitting glass layer G1 on the opposite side to the first emission surface H1, stacked in the order shown. The light reflecting layer B has a thick portion B3 in the stacking direction Z and a thin portion B2 whose thickness L1 in the stacking direction Z is 2 / 3 or less of the thickness L2 of the thick portion B3. In the thin portion B2, the proportion of transmitted light Lt in the incident light L from the first radiation surface H1 side is relatively high, and the proportion of reflected light Lr is relatively low, compared to the thick portion B3.

[0031] Regarding the thinned portion of the light reflecting layer B, as shown in the plan view of the light reflecting layer B (or the glass composite W) in FIG. 3, the thinned portion is provided continuously and integrally in a plan view perpendicular to the first radiation surface H1 and has an area of ​​5 cm2 in a plan view. 2 The metal thin portion has a first thin metal portion B1 having the above area, and a second thin metal portion B2 that is provided integrally and continuously in a plan view and has an area in a plan view less than the area of ​​the first thin metal portion B1. Here, the second thin metal portions B2 are provided in a form that is dispersed and distributed in a plan view, and the area of ​​one second thin metal portion B2 is 0.03 cm 2 That's all.

[0032] The light-reflecting layer B is preferably a metal-deposited layer formed by depositing a metal on the side of the infrared-emitting glass layer G1 opposite to the side where the first radiation surface H1 is present. The deposited metal is preferably at least one of silver, a silver alloy, aluminum, an aluminum alloy, and a copper alloy.

[0033] Furthermore, with regard to the light-reflecting layer B, the thickness of each of the first thin metal portion B1 and the second thin metal portion B2 in the stacking direction Z is preferably 0 nm or more and 50 nm or less, more preferably 0 nm or more and 10 nm or less. Incidentally, the thickness of the thick portion B3 is preferably 50 nm or more and 500 nm or less, more preferably 70 nm or more and 200 nm or less. With the above configuration, the first thin metal portion B1 can effectively transmit electromagnetic waves for communication (e.g., electromagnetic waves with frequencies of approximately 300 MHz or more and 300 GHz or less), and the second thin metal portion B2 can effectively transmit visible light for lighting. Furthermore, glare can be reduced, especially at night.

[0034] In plan view, the ratio of the area of ​​the thin portions to the entire area of ​​the light reflecting layer B is preferably 1% or more and 50% or less. From the viewpoint of light transmission, the ratio of the area of ​​the second metal thin portions B2 to the entire area of ​​the light reflecting layer B is preferably 1% or more. In the plan view of FIG. 3, the first thin metal portion B1 is rectangular and the second thin metal portion B2 is circular, but they are not limited to this and may be various shapes such as oval or polygonal.

[0035] 1 , the glass composite W according to this embodiment further includes a protective layer for protecting the light-reflecting layer B on the side of the light-reflecting layer B opposite to the side on which the infrared-emitting glass layer G1 is present, and the protective layer is an auxiliary infrared-emitting layer J (hereinafter, may be referred to as the infrared-emitting layer J) that emits infrared light from a second emission surface H2, which is the emission surface H on the side opposite to the side on which the light-reflecting layer B is present. Details of the light-reflecting layer B and the auxiliary infrared-emitting layer J will be described later.

[0036] As shown in FIG. 2, the light reflecting layer B and the infrared emitting layer J are formed on the surface of the infrared emitting glass layer G1 opposite to the first emitting surface H1 by sputtering (depositing by physical vapor deposition (PVD)) a metal material as the light reflecting layer B and sputtering a resin material as the infrared emitting layer J via a punching metal PM. As shown in Fig. 2, the punched metal PM preferably has a configuration in which a first flat plate portion PM1 overlapping a first thin-metal portion B1 (shown in Fig. 3) in a plan view and a second flat plate portion PM2 overlapping a second thin-metal portion B2 (shown in Fig. 3) are integrally connected to a metal frame PM4. Note that, although a plurality of second flat plate portions PM2 are dispersed in a plan view, the plurality of second flat plate portions PM2 are connected to the metal frame PM4 by, for example, connection lines PM3 that are sufficiently thin in a plan view.

[0037] The method for forming the light reflecting layer B is not particularly limited, and may be a chemical vapor deposition (CVD) method, a plasma enhanced chemical vapor deposition (PECVD) method, magnetron sputtering, an ion beam assisted deposition method, or the like. The infrared emitting layer J may be formed by the same method as that for the light reflecting layer B or by a different method, and may be formed by spray coating, dip coating, or plasma enhanced chemical vapor deposition (PECVD).

[0038] As shown in FIG. 4, the glass composite W may have a structure obtained by inverting the glass composite W shown in FIG. 1 in the stacking direction Z, i.e., a structure obtained by stacking an auxiliary infrared-emitting layer J as a protective layer, a light-reflecting layer B, and an infrared-emitting glass layer G1 in this order from the air side.

[0039] 5, the glass composite W may have a laminated glass structure in which the light-reflecting layer B and the auxiliary infrared-emitting layer J are sandwiched between an infrared-emitting glass layer G1 and a back surface glass layer G2. In other words, the glass composite W shown in FIG. 1 may have a configuration in which the back surface glass layer G2 is provided on the side opposite to the side where the light-reflecting layer B of the auxiliary infrared-emitting layer J is present (the side where the second emission surface H2 is present). The back surface glass layer G2 may be an infrared-emitting back surface glass layer that emits infrared light from the third emission surface H3, which is the emission surface H on the side opposite to the side where the auxiliary infrared-emitting layer J is present. Here, the auxiliary infrared radiation layer J and the rear glass layer G2 (infrared radiation rear glass layer) are bonded together by an intermediate resin Tu, which is made of one or more of polyvinyl butyral, polyethylene vinyl acetate, and polyurethane. With this configuration, the infrared radiation glass layer G1 and the rear surface glass layer G2 (infrared radiation rear surface glass layer) can maintain the glass fragments when they are broken by impact.

[0040] The infrared radiation glass layer G1 and the back surface glass layer G2 (infrared radiation back surface glass layer) are preferably glass for vehicles, and more preferably made of at least one of alkali-free glass, soda-lime glass, alkali borosilicate glass, and acrylic resin glass. The infrared radiation glass layer G1 and the back surface glass layer G2 (infrared radiation back surface glass layer) may be made of the same material or different materials. The infrared radiation glass layer G1 and the rear surface glass layer G2 (infrared radiation rear surface glass layer) may be configured as tempered glass, and a single layer glass treated by heat treatment or chemical treatment can be suitably used, and the strength can be increased compared to ordinary glass (i.e., untempered glass such as soda-lime silica glass or annealed glass). Furthermore, the infrared-emitting glass layer G1 and the rear glass layer G2 (infrared-emitting rear glass layer) may be reinforced with fillers and / or fibers. The infrared radiation glass layer G1, the rear surface glass layer G2 (infrared radiation rear surface glass layer), and the intermediate resin Tu are preferably transparent to visible light.

[0041] In one example of a method for manufacturing the glass composite W shown in FIG. 5, a laminate in which an infrared emitting glass layer G1, a light reflecting layer B, and an auxiliary infrared emitting layer J are stacked as shown in FIG. 1 is laminated on a back surface glass layer G2 with an intermediate resin Tu interposed therebetween. Next, the glass composite W is temporarily compressed by a method such as a nipper roll method in which the laminated glass composite W is heated by heating it to about 70 to 100°C, then sandwiched between rollers and temporarily compressed while removing the air; a rubber channel method in which the ends (four sides) of the glass composite W in a plan view are tied with rubber tubing, the air is removed, and temporarily compressed; or a rubber bag method in which the glass composite W is placed in a rubber bag, the inside of the rubber bag is evacuated, and temporarily compressed. Finally, the final pressure bonding is carried out by an autoclave method, for example, at about 100 to 130° C. for about 1 to 2 hours under pressure to remove all air and to perform pressure bonding. Furthermore, when the intermediate resin Tu is heated during the pressing process, it flows into the area where the thin portion B2 of the light-reflecting layer B exists, and if the thickness of the thin portion B2 is 0 μm, it directly connects the infrared radiation glass layer G1 and the back surface glass layer G2.

[0042] As another example, as shown in FIG. 6, the glass composite W may be a structure obtained by inverting the glass composite W shown in FIG. 5 in the stacking direction Z, i.e., a back surface glass layer G2, an intermediate resin Tu, an auxiliary infrared radiation layer J as a protective layer, a light reflecting layer B, and an infrared radiation glass layer G1, stacked in this order from the air side.

[0043] As another example, the glass composite W may have a structure in which the auxiliary infrared radiation layer J is omitted from the glass composite W shown in FIG. 5, as shown in FIG.

[0044] From the viewpoint of exhibiting the above-mentioned infrared radiation performance, in the glass composite W shown in FIG. 1 , the thickness of the infrared-emitting glass layer G1 is preferably 200 μm or more and 10,000 μm or less; in the glass composite W shown in FIG. 5 , the thickness of the infrared-emitting glass layer G1 is preferably 200 μm or more and 10,000 μm or less; in the glass composite W shown in FIG. 1 , the thickness of the infrared-emitting glass layer G1 is preferably 200 μm or more and 10,000 μm or less; in the glass composite W shown in FIG. 6 , the thickness of the back surface glass layer G2 (infrared-emitting back surface glass layer) is preferably 200 μm or more and 10,000 μm or less; and in the glass composite W shown in FIG. 7 , the thickness of the infrared-emitting glass layer G1 is preferably 200 μm or more and 10,000 μm or less.

[0045] 1 to 6 described above are illustrated so that the auxiliary infrared emission layer J does not exist in the portions corresponding to the thin portions B1 and B2 of the light-reflecting layer B in plan view. However, from the viewpoints of improving electromagnetic wave transparency and lighting performance and reducing glare at night, etc., this configuration is not necessarily required. Specifically, the auxiliary infrared emission layer J may have a thickness in the portions corresponding to the thin portions B1 and B2 of the light-reflecting layer B in plan view.

[0046] The glass composite W described so far has an overall surface average solar reflectance of 40% or more, and an average surface emissivity, which is the wavelength average of the emissivity of infrared light in the wavelength range of 8 μm to 13 μm, of 80% or more. More preferably, the overall surface average solar reflectance is 60% or more, and the surface average average emissivity, which is the wavelength average of the emissivity of infrared light of 8 μm or more and 13 μm or less, is 85% or more.

[0047] [Details of the resin material that makes up the infrared radiation layer] In the following description, the description of the film thickness of the infrared radiation layer J is based on a configuration in which the infrared radiation layer J has a substantially uniform thickness in plan view and is directed toward the atmosphere. The resin material can be a colorless resin material containing a carbon-fluorine bond (CF), a siloxane bond (Si-O-Si), a carbon-chlorine bond (C-Cl), a carbon-oxygen bond (CO), an ester bond (R-COO-R), an ether bond (COC bond), or a benzene ring. For each resin material (excluding carbon-oxygen bonds), the wavelength ranges with absorption coefficients in the atmospheric window wavelength band are shown in Figure 9.

[0048] According to Kirchhoff's law, emissivity (ε) and light absorptance (A) are equal. Light absorptance can be calculated from the absorption coefficient (α) using the equation A=1-exp(-αt) (hereafter referred to as the light absorptance equation), where t is the film thickness. In other words, by adjusting the film thickness of the infrared radiation layer J, it is possible to obtain a large thermal radiation in a wavelength band with a large absorption coefficient. When performing radiative cooling outdoors, it is recommended to use a material with a large absorption coefficient in the wavelength band of 8 μm to 14 μm, which is the atmospheric window. In addition, to suppress the absorption of sunlight, it is advisable to use a material that has no or a small absorption coefficient in the wavelength range of 0.3 μm to 4 μm, especially in the range of 0.4 μm to 2.5 μm. As can be seen from the relationship between the absorption coefficient and absorptance, the light absorptance (emissivity) changes depending on the film thickness of the resin material.

[0049] In order to lower the temperature below the surrounding atmosphere through radiative cooling in a solar radiation environment, if a material is selected that has a large absorption coefficient in the wavelength band of the atmospheric window and almost no absorption coefficient in the wavelength band of sunlight, then by adjusting the film thickness, it will absorb almost no sunlight but emit a lot of thermal radiation from the atmospheric window, meaning that it is possible to create a state in which the output from radiative cooling is greater than the input of sunlight.

[0050] Regarding carbon-fluorine bonds (CF), the absorption coefficients due to CHF and CF2 are widely distributed over a wide wavelength band from 8 μm to 14 μm, which is the atmospheric window, with a particularly large absorption coefficient at 8.6 μm. In addition, in the solar wavelength band, there is no significant absorption coefficient in the wavelength range from 0.3 μm to 2.5 μm, where the energy intensity is high.

[0051] Resin materials with carbon-fluorine bonds (CF) include: Polytetrafluoroethylene (PTFE), a fully fluorinated resin; Partially fluorinated resins polychlorotrifluoroethylene (PCTFE), polyvinylidene fluoride (PVDF), and polyvinyl fluoride (PVF); Perfluoroalkoxy fluororesin (PFA), a fluorinated resin copolymer; Tetrafluoroethylene-hexafluoropropylene copolymer (FEP), Ethylene-tetrafluoroethylene copolymer (ETFE), Examples include ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0052] Resin materials having a siloxane bond (Si-O-Si) include silicone rubber and silicone resin. In this resin, a large absorption coefficient due to the stretching of C-Si bonds appears broadly around a wavelength of 13.3 μm, an absorption coefficient due to the out-of-plane bending angle (vertical shaking) of CSiH2 appears broadly around a wavelength of 10 μm, and a small absorption coefficient due to the in-plane bending angle (scissors) of CSiH2 appears around a wavelength of 8 μm.

[0053] For carbon-chlorine bonds (C-Cl), the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. Resin materials include polyvinyl chloride resin (PVC) and polyvinylidene chloride resin (PVDC). In the case of polyvinyl chloride resin, due to the electron-withdrawing effect of chlorine, an absorption coefficient originating from the bending vibration of the CH of the alkene contained in the main chain appears at a wavelength of around 10 μm.

[0054] Ester bonds (R-COO-R) and ether bonds (COC bonds) have absorption coefficients in the wavelength range of 7.8 μm to 9.9 μm. In addition, the carbon-oxygen bonds contained in ester bonds and ether bonds have strong absorption coefficients in the wavelength range of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, absorption appears over a wide wavelength range from 8.1 μm to 18 μm due to the vibration of the benzene ring itself and the vibration of surrounding elements caused by the influence of the benzene ring.

[0055] Resins having these bonds include methyl methacrylate resin, ethylene terephthalate resin, trimethylene terephthalate resin, butylene terephthalate resin, ethylene naphthalate resin, and butylene naphthalate resin.

[0056] [Considerations of light absorption] Let us consider the light absorption in the ultraviolet-visible region of resin materials with the bonds and functional groups described above, i.e., sunlight absorption. The origin of the absorption of ultraviolet to visible light is the transition of electrons that contribute to the bond. Absorption in this wavelength range can be understood by calculating the bond energy. First, let's consider the wavelengths at which resin materials with carbon-fluorine bonds (CF) have absorption coefficients in the ultraviolet to visible range. The bond energies of the CC, CH, and CF bonds in the basic structural parts of polyvinylidene fluoride (PVDF) are 4.50 eV, 4.46 eV, and 5.05 eV. These correspond to wavelengths of 0.275 μm, 0.278 μm, and 0.246 μm, respectively, and light of these wavelengths is absorbed.

[0057] Since the solar spectrum only contains wavelengths longer than 0.300 μm, when fluororesin is used, it hardly absorbs the ultraviolet, visible, or near-infrared rays of sunlight. Note that ultraviolet rays are defined as wavelengths shorter than 0.400 μm, visible light is defined as wavelengths from 0.400 μm to 0.800 μm, near-infrared rays are defined as wavelengths from 0.800 μm to 3 μm, mid-infrared rays are defined as wavelengths from 3 μm to 8 μm, and far-infrared rays are wavelengths longer than 8 μm.

[0058] The absorbance spectrum of 50 μm-thick PFA (perfluoroalkoxy fluororesin) in the ultraviolet to visible region is shown in Figure 10, which shows that it has almost no absorbance. Although a slight increase in the absorbance spectrum can be seen on the shorter wavelength side than 0.4 μm, this increase is merely due to the effect of scattering from the sample used in the measurement, and there is no actual increase in absorbance.

[0059] In the ultraviolet region of siloxane bonds (Si-O-Si), the bond energy of the Si-O-Si in the main chain is 4.60 eV, which corresponds to a wavelength of 269 nm. Because the sunlight spectrum only contains wavelengths longer than 0.300 μm, in the majority of cases, siloxane bonds hardly absorb any of the ultraviolet, visible, or near-infrared rays of sunlight.

[0060] The absorptance spectrum of 100 μm thick silicone rubber in the ultraviolet to visible region is shown in Figure 10, which shows that it has almost no absorptance. Although a slight increase in the absorptance spectrum can be seen on the shorter wavelength side than 0.4 μm, this increase is merely due to the effect of scattering from the sample used for measurement, and there is no actual increase in absorptance.

[0061] Regarding the carbon-chlorine bond (C-Cl), the bond energy between carbon and chlorine in alkenes is 3.28 eV, and the wavelength is 0.378 μm, so they absorb a lot of ultraviolet light in sunlight, but have almost no absorption in the visible range. Figure 10 shows the absorption spectrum of a 100 μm thick vinyl chloride resin in the ultraviolet to visible region, and shows that light absorption increases at wavelengths shorter than 0.38 μm. FIG. 10 shows the absorption spectrum of a 100 μm thick vinylidene chloride resin in the ultraviolet to visible region, and shows a slight increase in the absorption spectrum on the shorter wavelength side than 0.4 μm.

[0062] Resins with 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 naphthalate resin, and butylene naphthalate resin. For example, the bond energy of the C-C bond in acrylic is 3.93 eV, and it absorbs sunlight with wavelengths shorter than 0.315 μm, but has almost no absorption in the visible range.

[0063] As an example of a resin material having these bonds and functional groups, the absorbance spectrum from ultraviolet to visible light of a 5 mm thick methyl methacrylate resin is shown in Figure 10. The methyl methacrylate resin shown here is a commonly available product on the market, and contains a benzotriazole-based ultraviolet absorber. Because the plate is 5 mm thick, the wavelengths with small absorption coefficients are also large, and light absorption is greater on the shorter wavelength side than 0.38 μm, which is longer than the wavelength of 0.315 μm.

[0064] As an example of a resin material having these bonds and functional groups, the absorption spectrum from ultraviolet to visible light of a 40 μm thick ethylene terephthalate resin is shown in FIG. As shown in the figure, the absorptance increases as the wavelength approaches 0.315 μm, and absorptance increases sharply at a wavelength of 0.315 μm. Note that with ethylene terephthalate resin, as the thickness increases, the absorptance due to the absorption edge derived from C-C bonds increases slightly longer than 0.315 μm, and the absorptance in ultraviolet light increases, similar to that of commercially available methyl methacrylate resin.

[0065] The infrared radiation layer J may be a single layer film made of one type of resin material, a multilayer film made of multiple types of resin materials, a single layer film made of a resin material in which multiple types of resin materials are blended, or a multilayer film made of a resin material in which multiple types of resin materials are blended, as long as it is made of a resin material having the above-mentioned emissivity (light emissivity) and light absorptivity properties. The blends also include copolymers such as alternating copolymers, random copolymers, block copolymers and graft copolymers, as well as modified products with substituted side chains.

[0066] [Emissivity of silicone rubber] Figure 11 shows the emissivity spectrum of the air window of silicone rubber with siloxane bonds. Silicone rubber exhibits a large broad absorption coefficient caused by the stretching of C-Si bonds, centered around a wavelength of 13.3 μm; CSiH2 exhibits a broad absorption coefficient caused by the out-of-plane bending angle (vertical rocking) of the target object, centered around a wavelength of 10 μm; and CSiH2 exhibits a small absorption coefficient caused by the in-plane bending angle (scissors) of the target object, centered around a wavelength of 8 μm. Due to this effect, the wavelength average of the emissivity for a 1 μm thick film is 80% at wavelengths from 8 μm to 14 μm, which falls within the wavelength average of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0067] Incidentally, Figure 11 also shows the radiation spectrum when quartz, an inorganic material with a thickness of 1 μm, is placed on silver. When quartz is 1 μm thick, it only has a narrow band radiation peak in the wavelength range of 8 μm to 14 μm. When this thermal radiation is averaged over the wavelength range of 8 μm to 14 μm, the emissivity for wavelengths of 8 μm to 14 μm is 32%, making it difficult to demonstrate radiative cooling performance.

[0068] [Emissivity of PFA] Figure 12 shows the emissivity in the atmospheric window of perfluoroalkoxy fluororesin (PFA), a typical example of a resin with carbon-fluorine bonds. The absorption coefficients due to CHF and CF2 are widely distributed 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. As a result of this effect, the wavelength average of the emissivity for a 10 μm thick film is 45% for wavelengths from 8 μm to 14 μm, which falls within the wavelength average of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0069] [Emissivity of vinyl chloride resin and vinylidene chloride resin] Figure 13 shows the emissivity of polyvinyl chloride resin (PVC) at the atmospheric window, as a representative example of resins with carbon-chlorine bonds. Also, Figure 21 shows the emissivity of polyvinylidene chloride resin (PVDC) at the atmospheric window. Regarding the carbon-chlorine bond, the absorption coefficient due to the C-Cl stretching vibration appears in a broad band with a half-width of 1 μm or more centered at a wavelength of 12 μm. In addition, in the case of vinyl chloride resin, the electron-withdrawing effect of chlorine causes an absorption coefficient at a wavelength of around 10 μm, which is due to the bending vibration of the CH of the alkene contained in the main chain. The same is true for vinylidene chloride resin. Due to these effects, the wavelength average of the emissivity for a 10 μm thick film is 43% at wavelengths from 8 μm to 14 μm, which falls within the wavelength average of 40% or more. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0070] [Ethylene terephthalate resin] FIG. 14 shows the emissivity of ethylene terephthalate resin in the atmospheric window as a typical example of a resin having an ester bond or a benzene ring. Ester bonds have an absorption coefficient in the wavelength range of 7.8 μm to 9.9 μm. Furthermore, the carbon-oxygen bond contained in the ester bond exhibits a strong absorption coefficient in the wavelength range of 8 μm to 10 μm. When a benzene ring is introduced into the side chain of a hydrocarbon resin, a wide range of absorption appears in 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 caused by the influence of the benzene ring. Due to these effects, the wavelength average of the emissivity for a 10 μm thick film is 71% at wavelengths from 8 μm to 14 μm, which falls within the wavelength average of 40% or more as specified. As shown in the figure, the emissivity in the atmospheric window region increases as the film thickness increases.

[0071] [Emissivity of olefin-modified materials] Figure 15 shows the emissivity spectrum of an olefin-modified material whose main component is olefin and does not contain carbon-fluorine bonds (CF), carbon-chlorine bonds (C-Cl), ester bonds (R-COO-R), ether bonds (COC bonds), or benzene rings. The sample was prepared by applying olefin resin onto evaporated silver using a bar coater and drying it. As shown in the figure, the emissivity in the atmospheric window region is small, and as a result, the wavelength average of the emissivity for a thickness of 10 μm is 27% at wavelengths from 8 μm to 14 μm, which does not fall within the requirement of a wavelength average of 40% or more.

[0072] The emissivity shown is that of an olefin resin modified for application with a bar coater, and in the case of a pure olefin resin, the emissivity in the atmospheric window region is even smaller. Thus, radiative cooling is not possible unless the molecule contains a carbon-fluorine bond (CF), a carbon-chlorine bond (C-Cl), an ester bond (R-COO-R), an ether bond (COC bond), or a benzene ring.

[0073] [Surface Temperature of Light Reflecting Layer and Resin Material Layer] The thermal radiation of the atmospheric window of the infrared radiation layer J occurs near the surface of the resin material. As can be seen from Figure 11, in the case of silicone rubber, if the thickness is greater 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 occurs within a depth of approximately 10 μm from the surface, and radiation from deeper regions does not escape.

[0074] As can be seen from Figure 12, in the case of fluororesin, even if the thickness exceeds 100 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of fluororesin, thermal radiation in the atmospheric window occurs within a depth of approximately 100 μm from the surface, and radiation from deeper parts does not escape to the outside. Figure 13 shows that in the case of vinyl chloride resin, even if the thickness exceeds 100 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of vinyl chloride resin, thermal radiation in the atmospheric window occurs within a depth of approximately 100 μm from the surface, and radiation from deeper parts does not escape to the outside. From FIG. 21, it can be seen that vinylidene chloride resin is similar to vinyl chloride resin.

[0075] 14, in the case of ethylene terephthalate resin, even if the thickness exceeds 125 μm, there is almost no increase in thermal radiation in the atmospheric window region. In other words, in the case of ethylene terephthalate resin, thermal radiation in the atmospheric window occurs in a region about 100 μm deep from the surface, and radiation from deeper regions does not escape to the outside.

[0076] As described above, the thermal radiation from the atmospheric window region generated from the surface of the resin material occurs within a depth of approximately 100 μm from the surface. If the resin thickness increases beyond this, the cold generated by the radiation cooling of the glass composite W is insulated by the resin material, which does not contribute to thermal radiation. Consider an infrared emitting layer J that ideally does not absorb any sunlight, formed on a light-reflecting layer B. In this case, sunlight is absorbed only by the light-reflecting layer B of the glass composite W. The thermal conductivity of resin materials is generally about 0.2 W / m / K. When this thermal conductivity is taken into account, calculations show that if the thickness of the infrared radiation layer J exceeds 20 mm, the temperature of the cooling surface (the surface of the light-reflecting layer B opposite to the side where the infrared radiation layer J is present) will rise.

[0077] Even if an ideal resin material that does not absorb any sunlight exists, the thermal conductivity of resin materials is generally around 0.2 W / m / K, so if the thickness exceeds 20 mm as shown in Figure 16, the light-reflecting layer B will be heated by sunlight, and the object to be cooled (not shown) placed on the light-reflecting layer side will also be heated. In other words, the thickness of the resin material used as the auxiliary infrared radiation layer J of the glass composite W needs to be 20 mm or less.

[0078] Figure 16 is a plot of the surface temperature of the radiating surface H of the glass composite W and the temperature of the light-reflecting layer B, calculated assuming a clear day in the west of Japan in midsummer at noon. The sunlight is AM1.5, 1000W / m 2 The outside temperature is 30°C, and the radiant energy varies depending on the temperature, but is 100W at 30°C. This calculation assumes that no sunlight is absorbed by the resin material layer. Assuming no wind, the convective heat transfer coefficient is 5W / m 2 / K.

[0079] [Light absorption rate of silicone rubber, etc.] Figure 17 shows the light absorptance of silicone rubber with CH3 side chains at a thickness of 100 μm against the sunlight spectrum, and the light absorptance spectrum of perfluoroalkoxy fluororesin at a thickness of 100 μm against the sunlight spectrum. As mentioned above, it can be seen that both resins have almost no light absorptance in the ultraviolet region.

[0080] For silicone rubber, in the near-infrared region, the light absorption rate increases in the region longer than 2.35 μm. However, because the intensity of the solar spectrum in this wavelength region is weak, even if the light absorption rate in the region longer than 2.35 μm is 100%, the solar energy absorbed is only 20 W / m 2 is.

[0081] Perfluoroalkoxy fluororesin has almost no light absorption in the wavelength range of 0.3 μm to 2.5 μm, but does absorb light at wavelengths longer than 2.5 μm. However, even if the resin film thickness is increased and the light absorption rate at wavelengths longer than 2.5 μm becomes 100%, the amount of solar energy absorbed is only about 7 W.

[0082] In addition, as the thickness (film thickness) of the infrared radiation layer J increases, the emissivity of the atmospheric window region becomes almost 1. In other words, in the case of a thick film, the thermal radiation radiated into space in the atmospheric window region when used at low altitudes is 160 W / m at 30°C. 2 to 125W / m 2 The light absorption in the light reflecting layer B is about 50 W / m as specified above. 2 Even if the light absorption of the light reflective layer B and the sunlight absorption when the silicone rubber or perfluoroalkoxy fluororesin is made into a thick film are added together, the total amount is smaller than the thermal radiation radiated into space. From the above, the maximum film thickness of silicone rubber and perfluoroalkoxy fluororesin is 20 mm from the viewpoint of thermal conductivity.

[0083] [Light absorption of hydrocarbon resins] If the resin material forming the infrared radiation layer J is a resin whose main chain is a hydrocarbon having one or more carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, or benzene rings, or if it is a silicone resin whose hydrocarbon side chains have two or more carbon atoms, absorption due to vibrations such as bond bending and stretching is observed in the near-infrared region in addition to the ultraviolet absorption due to the covalent bond electrons described above.

[0084] Specifically, absorption due to the fundamental tones of the transitions to the first excited states of CH3, CH2, and CH appears at wavelengths of 1.6 μm to 1.7 μm, 1.65 μm to 1.75 μm, and 1.7 μm, respectively. Furthermore, absorption due to the fundamental tones of the combination tones of CH3, CH2, and CH appears at wavelengths of 1.35 μm, 1.38 μm, and 1.43 μm, respectively. Furthermore, overtones of the transitions to the second excited states of CH2 and CH appear at wavelengths around 1.24 μm. The fundamental tones of the bending and stretching of the C-H bond are distributed over a wide band from 2 μm to 2.5 μm.

[0085] Furthermore, when an ester bond (R-COO-R) or an ether bond (COC) is present, there is a large optical absorption at a wavelength of around 1.9 μm. According to the above-mentioned optical absorptance relational expression, the optical absorptance caused by these factors becomes smaller and less noticeable when the resin material film is thin, but becomes larger when the film is thick.

[0086] FIG. 18 shows the relationship between the light absorptance and the spectrum of sunlight when the film thickness of an ethylene terephthalate resin having an ester bond and a benzene ring is changed. As shown in the figure, as the film thickness increases to 25 μm, 125 μm, and 500 μm, the light absorption in the wavelength range longer than 1.5 μm, which is caused by the respective vibrations, increases. Furthermore, the optical absorption increases not only on the long wavelength side but also from the ultraviolet region to the visible region, due to the broadening of the optical absorption edge caused by chemical bonding.

[0087] When the film thickness is thin, the light absorption rate is high at the wavelength with the largest absorption coefficient, but as the film thickness increases, a weak absorption coefficient at the broadened absorption edge appears as the absorptance according to the light absorption rate relational expression mentioned above. As a result, as the film thickness increases, light absorption increases from the ultraviolet region to the visible region. When the thickness is 25 μm, the absorption of the solar spectrum is 15 W / m 2 , when the thickness is 125 μm, the absorption of the solar spectrum is 41 W / m 2 , the absorption of the solar spectrum at a thickness of 500 μm is 88 W / m 2 is.

[0088] The light absorption of the light-reflecting layer B is 50 W / m 2 Therefore, when the film thickness is 500 μm, the sum of the solar light absorption of the ethylene terephthalate resin and the solar light absorption of the light-reflecting layer B is 138 W / m 2 As mentioned above, the maximum value of infrared radiation in the wavelength band of the atmospheric window in the summer in the lowlands of Japan is about 160W at 30°C on a day with good atmospheric conditions, and is usually about 125W. From the above, if the film thickness of the ethylene terephthalate resin is 500 μm or more, the radiative cooling performance will not be exhibited.

[0089] The origin of the absorption spectrum in the wavelength range from 1.5 μm to 4 μm is not the functional group but the vibration of the hydrocarbon main chain, and if it is a hydrocarbon-based resin, it will behave in the same way as ethylene terephthalate resin. Furthermore, hydrocarbon-based resins have light absorption in the ultraviolet range due to chemical bonds, and they will behave in the same way as ethylene terephthalate resin from the ultraviolet to visible range. In other words, hydrocarbon resins behave in the same way as ethylene terephthalate resins in the wavelength range of 0.3 μm to 4 μm. For these reasons, the film thickness of hydrocarbon resins must be thinner than 500 μm.

[0090] [Light absorption of blend resins] When a resin material is a blend of a resin whose main chain is a carbon-fluorine bond or a siloxane bond and a resin whose main chain is a hydrocarbon, light absorption in the near-infrared region due to CH, CH2, CH3, etc. appears depending on the proportion of the blended resin whose main chain is a hydrocarbon. When the main component is a carbon-fluorine bond or a siloxane bond, the light absorption in the near-infrared region caused by hydrocarbons is small, so the thickness can be increased up to the upper limit of 20 mm from the viewpoint of thermal conductivity. However, when a blended hydrocarbon resin is the main component, the thickness must be 500 μm or less.

[0091] Blends of fluororesin or silicone rubber with hydrocarbons include those in which the side chains of fluororesin or silicone rubber are substituted with hydrocarbons, as well as alternating copolymers, random copolymers, block copolymers, and graft copolymers of fluoromonomers or silicone monomers with hydrocarbon monomers. Examples of alternating copolymers of fluoromonomers and hydrocarbon monomers include fluoroethylene vinyl ester (FEVE), fluoroolefin-acrylate copolymer, ethylene-tetrafluoroethylene copolymer (ETFE), and ethylene-chlorotrifluoroethylene copolymer (ECTFE).

[0092] Depending on the molecular weight and proportion of the hydrocarbon side chains substituted, optical absorption in the near-infrared region due to CH, CH2, CH3, etc. appears. When the monomers introduced as side chains or copolymers are low molecular weight, or when the density of the introduced monomers is low, optical absorption in the near-infrared region due to hydrocarbons becomes small, so the thickness can be increased up to 20 mm, which is the limit from the viewpoint of thermal conductivity. When introducing a high molecular weight hydrocarbon as a side chain of fluororesin or silicone rubber or as a copolymerizable monomer, the thickness of the resin must be 500 μm or less.

[0093] [Thickness of the resin material layer] From the viewpoint of practical use of the glass composite W, it is preferable that the thickness of the infrared emitting layer J is thin. The thermal conductivity of resin materials is generally lower than that of metals, glass, etc. In order to effectively cool an object to be cooled (not shown), it is preferable that the thickness of the infrared emitting layer J is kept to the minimum necessary. The thicker the thickness of the infrared emitting layer J, the greater the thermal radiation from the atmospheric window, and once a certain thickness is exceeded, the thermal radiation energy from the atmospheric window becomes saturated.

[0094] The thickness at which the film saturates depends on the resin material, but in the case of fluororesin, saturation is generally sufficient at around 300 μm. Therefore, from the perspective of thermal conductivity, it is preferable to keep the film thickness below 300 μm rather than 500 μm. Furthermore, although thermal radiation does not saturate, even a thickness of around 100 μm can provide sufficient thermal radiation in the atmospheric window region. The thinner the thickness, the higher the thermal conductivity and the more effectively the temperature of the object to be cooled can be lowered, so in the case of fluororesin, it is best to keep the thickness below around 100 μm.

[0095] The absorption coefficients resulting from carbon-silicon bonds, carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds are greater than the absorption coefficient resulting from C—F bonds. Naturally, from the perspective of thermal conductivity, it is preferable to keep the film thickness to 300 μm or less rather than 500 μm, but an even greater radiative cooling effect can be expected if the film thickness is made even thinner and thermal conductivity is increased. In the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, and benzene rings, saturation occurs even at a thickness of 100 μm, and sufficient thermal radiation is obtained in the atmospheric window region at a thickness of 50 μm. The thinner the resin material, the higher the thermal transmittance and the more effectively the temperature of the object being cooled can be lowered, so 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 reduces the insulating properties and allows the object to be cooled effectively. In the case of carbon-chlorine bonds, a thickness of 100 μm or less allows the object to be cooled effectively.

[0096] Thinning the glass also has another benefit besides lowering its thermal insulation and making it easier to transfer heat and cold. It also reduces the absorption of near-infrared light from CH, CH2, and CH3 in the near-infrared region, which is exhibited by resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, and ether bonds. Thinning the glass reduces the amount of sunlight absorbed by these bonds, which increases the cooling capacity of the glass composite W. From the above perspective, in the case of resins containing carbon-chlorine bonds, carbon-oxygen bonds, ester bonds, ether bonds, or benzene rings, a thickness of 50 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0097] In the case of carbon-silicon bonds, thermal radiation is saturated in the atmospheric window region even at a thickness of 50 μm, and sufficient thermal radiation can be obtained in the atmospheric window region even at a thickness of 10 μm. The thinner the infrared emitting layer J, the higher the thermal transmittance and the more effectively the temperature of the object to be cooled can be lowered. Therefore, in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less reduces the heat insulating properties and allows the object to be cooled more effectively. A thinner layer reduces solar absorption, thereby increasing the cooling capacity of the glass composite W. From the above perspective, in the case of resins containing carbon-silicon bonds, a thickness of 10 μm or less can more effectively produce a radiative cooling effect under sunlight.

[0098] [Details of the light-reflecting layer] As shown in FIG. 19, if the light reflecting layer B is made of silver as a base, the reflectance required for the light reflecting layer B can be obtained satisfactorily.

[0099] Incidentally, the "silver alloy" may be an alloy in which copper, palladium, gold, zinc, tin, magnesium, nickel, or titanium is added to silver in an amount of, for example, about 0.4% to 4.5% by mass. A specific example is "APC-TR (made by Furuya Metal)," a silver alloy made by adding copper and palladium to silver.

[0100] In order to provide the light-reflecting layer B with appropriate reflectance characteristics, a laminated structure may be used in which silver or a silver alloy is located adjacent to the protective layer and aluminum or an aluminum alloy is located away from the protective layer. Even in this case, the reflective material on the side where the radiation surface H exists (the side where the infrared radiation layer J exists) must be silver or a silver alloy. When the film is made up of two layers of silver (silver alloy) and aluminum (aluminum alloy), the thickness of the silver must be 10 nm or more, and the thickness of the aluminum must be 30 nm or more.

[0101] Incidentally, as an "aluminum alloy," an alloy in which copper, manganese, silicon, magnesium, zinc, carbon steel for mechanical structures, yttrium, lanthanum, gadolinium, or terbium is added to aluminum can be used.

[0102] Silver and silver alloys are vulnerable to rain and humidity and need to be protected from them, and also need to be prevented from tarnishing. For this reason, it is preferable to provide a protective layer adjacent to the silver or silver alloy to protect the silver.

[0103] [About the experimental results] Silver was formed to a thickness of 300 nm on a glass substrate, and silicone rubber with siloxane bonds, fluoroethylene vinyl ether with carbon-fluorine bonds, olefin modified material (olefin modified material), and vinyl chloride resin were applied on top of it while controlling the film thickness using a bar coater, and the radiative cooling performance was measured. The evaluation of radiative cooling performance was carried out three hours after noon outdoors in late June at an outside temperature of 35°C, and the temperature (°C) on the backside of the substrate was measured while the substrate was kept highly insulated. However, for polyvinyl chloride resin, the evaluation was carried out when the outside temperature was 29°C. Whether or not there was a radiative cooling effect was evaluated based on whether the temperature five minutes after placement on the jig was higher or lower than the outside temperature. The results of the radiative cooling test are shown in Figure 22.

[0104] Incidentally, the emissivity of fluoroethylene vinyl ether in the atmospheric window region is as shown in Figure 20. The emissivity of silicone rubber is as shown in Figure 11, the emissivity of an olefin modified body (olefin modified material) is as shown in Figure 15, and the emissivity of vinyl chloride resin is as shown in Figure 13.

[0105] In the case of silicone rubber containing siloxane bonds, it was found that it exhibits radiative cooling ability at thicknesses of 1 μm or more, as predicted by theory. It was found that fluoroethylene vinyl ether, which has a carbon-fluorine bond, exhibits radiative cooling ability at a film thickness of 5 μm, which is thinner than the theoretically predicted 10 μm. This is because not only does the carbon-fluorine bond absorb light in the atmospheric window, but also the ether bond of the vinyl ether absorbs light, increasing the light absorption rate in the atmospheric window compared to when either is used alone. Olefin modified materials (olefin modified materials) do not have radiative cooling capabilities because they have almost no thermal radiation in the atmospheric window region.

[0106] [Details of the protective layer] The protective layer (auxiliary infrared radiation layer J) is preferably made of a polyolefin resin having a thickness of 300 nm or more and 40 μm or less, or polyethylene terephthalate having a thickness of 17 μm or more and 40 μm or less. Polyolefin resins include polyethylene and polypropylene.

[0107] FIG. 23 shows the ultraviolet absorption rates of polyethylene, vinylidene chloride resin, ethylene terephthalate resin, and vinyl chloride resin. FIG. 24 shows the light transmittance of polyethylene, which is a suitable synthetic resin for forming the protective layer.

[0108] Since the glass composite W exerts a radiative cooling effect not only at night but also in a solar radiation environment, in order to maintain the light-reflecting layer B in a state in which it can reflect light, it is necessary to protect the light-reflecting layer B with a protective layer so that the silver of the light-reflecting layer B does not discolor in a solar radiation environment.

[0109] When the protective layer is formed from a polyolefin resin with a thickness of 300 nm or more and 40 μm or less, the polyolefin resin is a synthetic resin with an ultraviolet light absorption rate of 10% or less over the entire ultraviolet wavelength range of 0.3 μm to 0.4 μm, so the protective layer is less likely to deteriorate due to ultraviolet absorption.

[0110] Furthermore, since the thickness of the polyolefin resin forming the protective layer is 300 nm or more, it effectively exhibits a blocking function, such as blocking radicals generated in the infrared radiation layer J from reaching the silver or silver alloy forming the light-reflecting layer B, and blocking moisture that penetrates the infrared radiation layer J from reaching the silver or silver alloy forming the light-reflecting layer B, thereby making it possible to suppress discoloration of the silver or silver alloy forming the light-reflecting layer B.

[0111] Incidentally, the protective layer made of polyolefin resin deteriorates as it absorbs ultraviolet rays, forming radicals on the surface side away from the light-reflecting layer B. However, since the thickness is 300 nm or more, the formed radicals do not reach the light-reflecting layer B. Furthermore, even if the protective layer deteriorates as radicals are formed, the rate of deterioration is slow due to the low absorption of ultraviolet rays, so the above-mentioned blocking function can be maintained for a long period of time.

[0112] When the protective layer is formed from ethylene terephthalate resin to a thickness of 17 μm or more and 40 μm or less, ethylene terephthalate resin is a resin material that has a higher ultraviolet light absorption rate than polyolefin resin in the ultraviolet wavelength range of 0.3 μm to 0.4 μm. However, since the thickness is 17 μm or more, the protective layer effectively exhibits blocking functions for a long period of time, such as blocking radicals generated in the infrared emitting layer J from reaching the silver or silver alloy that forms the light reflecting layer B and blocking moisture that penetrates the infrared emitting layer J from reaching the silver or silver alloy that forms the light reflecting layer B, and thus can suppress discoloration of the silver or silver alloy that forms the light reflecting layer B.

[0113] In other words, the protective layer made of ethylene terephthalate resin deteriorates as it absorbs ultraviolet rays, forming radicals on the surface side away from the light-reflecting layer B. However, because the thickness is 17 μm or more, the formed radicals do not reach the light-reflecting layer B. Furthermore, even if the protective layer deteriorates while forming radicals, the thickness is 17 μm or more, so the above-mentioned blocking function can be maintained for a long period of time.

[0114] To explain further, the deterioration of ethylene terephthalate resin (PET) is caused by ultraviolet light cleaving the ester bond between ethylene glycol and terephthalic acid, forming radicals. This deterioration progresses from the surface of the PET that is exposed to ultraviolet light.

[0115] For example, when ethylene terephthalate resin (PET) is irradiated with ultraviolet rays of the intensity found in Osaka, the ester bonds of the PET are cleaved by approximately 9 nm per day, starting from the irradiated surface. Because the ethylene terephthalate resin (PET) is sufficiently polymerized, the cleaved ethylene terephthalate resin (PET) on the surface does not attack the silver (silver alloy) of light-reflecting layer B. However, if the cleaved end of the ethylene terephthalate resin (PET) reaches the silver (silver alloy) of light-reflecting layer B, the silver (silver alloy) will discolor.

[0116] Therefore, for outdoor use, to make the protective layer last for more than one year, a thickness of approximately 3 μm is required, calculated by multiplying 9 nm / day by 365 days. To make the ethylene terephthalate resin (PET) protective layer last for more than three years, a thickness of 10 μm or more is required. To make it last for more than five years, a thickness of 17 μm or more is required.

[0117] In addition, when the protective layer is formed of a polyolefin resin and an ethylene terephthalate resin, the reason for setting an upper limit on the thickness is to prevent the protective layer from exhibiting heat insulating properties that do not contribute to radiative cooling. In other words, the thicker the protective layer is, the more heat insulating properties it exhibits that do not contribute to radiative cooling. Therefore, the upper limit on the thickness is set to prevent the protective layer from exhibiting heat insulating properties that do not contribute to radiative cooling while still functioning as a protective layer for the light reflecting layer B.

[0118] In other words, if the protective layer is made thicker, there is no disadvantage in terms of preventing coloration of the silver (silver alloy) in the light-reflecting layer B, but it does cause problems in terms of radiative cooling. In other words, making the protective layer thicker increases the thermal insulation properties of the radiative cooling material. For example, polyethylene resin, which is an excellent synthetic resin for forming protective layers, has a low emissivity at the atmospheric window, as shown in Figure 28, so even if it is formed thickly, it does not contribute to radiative cooling. On the contrary, making it thicker actually increases the insulating properties of the radiative cooling material. Next, as the thickness increases, absorption in the near-infrared region due to the vibration of the main chain increases, increasing the effect of increasing solar absorption. For these reasons, a thick protective layer is disadvantageous for radiative cooling. From this perspective, the thickness of the protective layer made of polyolefin resin is preferably 5 μm or less, and more preferably 1 μm.

[0119] [Considerations on the protective layer] To examine the difference in how the protective layer affects the coloring of silver, we prepared a sample with the protective layer exposed and no infrared emitting layer J, as shown in Figure 25, and examined the coloring of silver after irradiating it with simulated sunlight. Specifically, samples were prepared by applying two types of protective layers, a common acrylic resin that absorbs ultraviolet light (for example, methyl methacrylate resin mixed with a benzotriazole-based ultraviolet absorber) and polyethylene, using a bar coater onto a film layer F (corresponding to the substrate) containing silver as a light-reflecting layer B, and their function as protective layers was examined. The thicknesses of the applied protective layers were 10 μm and 1 μm, respectively. The film layer F (corresponding to the substrate) is formed into a film shape using PET (ethylene terephthalate resin) or the like.

[0120] As shown in Figure 27, if the protective layer is made of acrylic resin, which has good ultraviolet absorption, the protective layer is decomposed by ultraviolet light to form radicals, causing the silver to quickly turn yellow and no longer function as a glass composite W (it absorbs sunlight and, like general materials, its temperature rises when exposed to sunlight). The 600h line in the figure indicates the results of a xenon weather test (ultraviolet light energy 60W / m) under the conditions of JIS standard 5600-7-7. 2 The reflectance spectrum after 600 hours of xenon weathering is shown in Fig. 1. The 0h line is the reflectance spectrum before the xenon weathering test.

[0121] As shown in Figure 26, when the protective layer is made of polyethylene, which has low ultraviolet light absorption, there is no decrease in reflectance from the near-infrared region to the visible region. In other words, resins whose main component is polyethylene (polyolefin resins) hardly absorb the ultraviolet light contained in sunlight that reaches the ground, and therefore do not easily form radicals even when exposed to sunlight, so the silver serving as the light-reflecting layer B does not become discolored even when exposed to sunlight. The 600h line in the figure indicates the results of a xenon weather test (ultraviolet light energy 60W / m) under the conditions of JIS standard 5600-7-7. 2 The reflectance spectrum after 600 hours of xenon weathering is shown in Fig. 1. The 0h line is the reflectance spectrum before the xenon weathering test.

[0122] The reason for the undulations in the reflectance spectrum in this wavelength range is the Fabry-Perot resonance of the polyethylene layer. This is due to changes in the thickness of the polyethylene layer caused by heat during the xenon weather test, and it can be seen that the resonance position changes slightly between the 0h line and the 600h line. However, no significant decrease in reflectance in the ultraviolet-visible range due to the yellowing of the silver is observed.

[0123] Furthermore, from the viewpoint of ultraviolet absorption, fluororesin-based materials can also be used as materials for forming protective layers, but when actually formed as protective layers, they become discolored and deteriorate during the formation stage, and therefore cannot be used as materials for forming protective layers. Silicone can also be used as a material for forming a protective layer from the viewpoint of ultraviolet absorption, but it has extremely poor adhesion to silver (silver alloys) and cannot be used as a material for forming a protective layer.

[0124] [Test results] With regard to the glass composite W described so far, those having the structure shown in Fig. 1 were designated as Examples 1, 5, and 6, those having the structure shown in Fig. 4 were designated as Example 2, those having the structure shown in Fig. 5 were designated as Examples 3 and 7, and those having the structure shown in Fig. 6 were designated as Example 4. Furthermore, as shown in Fig. 8, a structure in which an infrared emitting glass layer G, a light reflective layer B, and an infrared emitting layer J were laminated in this order from the air side was designated as Comparative Example 1, and an infrared emitting glass layer alone was designated as Comparative Example 2.

[0125] The conditions under which the glass composite W was tested for the Examples and Comparative Examples are shown in Table 2 below, and the test results are shown in Table 1.

[0126] [Table 1]

[0127] [Table 2]

[0128] The above test results show that the glass composites W according to Examples 1 to 7 achieved good results in terms of emissivity, visible light reflectance, radio wave transmittance, lighting properties, and glare resistance. On the other hand, in the glass composite W of Comparative Example 1, since the light-reflecting layer B does not have a thin portion, it is presumed that the test conditions for radio wave transmittance, lighting, and anti-reflection properties are not met. Furthermore, it is presumed that the glass composite W according to Comparative Example 2 does not satisfy the test conditions for visible light reflectance because it is configured without the light reflecting layer B.

[0129] [Another embodiment] (1) The glass composite W described above may have a light-controlling layer (not shown) having a light-controlling function on the side of the auxiliary infrared radiation layer J opposite to the side where the light-reflecting layer B is present. Alternatively, a light control layer (not shown) having a light control function may be provided on the side of the infrared radiation rear glass layer G2 opposite to the side on which the auxiliary infrared radiation layer J is present.

[0130] (2) The glass composite W described above may have a configuration in which an ultraviolet reflective layer that reflects ultraviolet rays is provided along the radiating surface H. In the case of the glass composite W, the ultraviolet reflective layer can be suitably made of a material such as an aluminum alloy.

[0131] Furthermore, the configurations disclosed in the above embodiments (including other embodiments, the same applies below) can be applied in combination with configurations disclosed in other embodiments, as long as no contradictions arise. Furthermore, the embodiments disclosed in this specification are examples, and the embodiments of the present invention are not limited to these, and can be modified as appropriate within the scope that does not deviate from the purpose of the present invention. [Industrial Applicability]

[0132] The glass composite of the present invention can be effectively used as a glass composite that can improve electromagnetic wave transmittance and daylighting properties and can also reduce glare at night, etc. [Explanation of symbols]

[0133] A: Infrared radiation layer B: Light reflective layer B1: 1st metal thin section B2: 2nd metal thin section B3:Thick part G1: Infrared radiation glass layer G2: Rear glass layer H: Radiation surface H1: 1st radiation surface H2: Second radiation surface H3: 3rd radiation surface J:Supplementary infrared radiation layer L1: Thickness of thin-walled part L2: Thickness of thick part Tu: Intermediate resin W: Glass composite Z:Lamination direction

Claims

1. a glass composite comprising: an infrared radiation glass layer that emits infrared light from a first radiation surface that is a radiation surface; and a light reflecting layer that is located on an opposite side of the infrared radiation glass layer from a side where the first radiation surface is present, stacked in the order described; the light reflecting layer has a thick portion in a stacking direction and a thin portion whose thickness in the stacking direction is 2 / 3 or less of the thickness of the thick portion, The thin portion is provided continuously and integrally in a plan view perpendicular to the first radiation surface and has an area of ​​5 cm ２ a first thin metal portion having an area equal to or greater than the area of ​​the first thin metal portion, and a second thin metal portion provided integrally and continuously in the plan view and having an area in the plan view less than the area of ​​the first thin metal portion, the second thin metal portion is provided in a plurality of portions in a dispersed and distributed manner in the plan view, A glass composite having an overall surface average solar reflectance of 40% or more and a surface average average emissivity, which is the wavelength average of the emissivity of infrared light of 8 μm or more and 13 μm or less, of 80% or more.

2. The glass composite according to claim 1 , wherein the thickness of each of the first thin metal portion and the second thin metal portion in the stacking direction is 0 nm or more and 50 nm or less.

3. The glass composite according to claim 1 , wherein the thickness of each of the first thin metal portion and the second thin metal portion in the stacking direction is 0 nm or more and 10 nm or less.

4. In the plan view, the area of ​​the second thin metal portion is 0.03 cm ２ 3. The glass composite according to claim 1 or 2, wherein

5. a protective layer for protecting the light reflecting layer on the side of the light reflecting layer opposite to the side where the infrared radiation glass layer is present; 3. The glass composite according to claim 1, wherein the protective layer is an auxiliary infrared emitting layer that emits infrared light from a second emitting surface that is an emitting surface on the side opposite to the side where the light reflecting layer is present.

6. a rear glass layer on the side of the auxiliary infrared radiation layer opposite to the side on which the light reflecting layer is present; the rear surface glass layer is an infrared radiation rear surface glass layer that emits infrared light from a third radiation surface, which is an radiation surface on the opposite side to the side on which the auxiliary infrared radiation layer is present, 6. The glass composite according to claim 5, wherein the intermediate resin bonding between the auxiliary infrared-emitting layer and the infrared-emitting rear glass layer is made of at least one of polyvinyl butyral, polyethylene vinyl acetate, and polyurethane.

7. The infrared radiation glass layer is 2. The glass composite according to claim 1, which is made of at least one of alkali-free glass, soda-lime glass, alkali borosilicate glass, and acrylic resin glass.

8. The infrared radiation glass layer and the infrared radiation back surface glass layer are 7. The glass composite according to claim 6, which is made of at least one of alkali-free glass, soda-lime glass, alkali borosilicate glass, and acrylic resin glass.

9. In the plan view, 3. The glass composite according to claim 1, wherein a ratio of an area of ​​the thin portion to an entire area of ​​the light-reflecting layer is 1% or more and 50% or less.

10. the light reflecting layer is a metal vapor-deposited layer formed by vapor-depositing a metal on a side of the infrared radiation glass layer opposite to a side on which the first radiation surface is present, 3. The glass composite according to claim 1, wherein the metal is at least one of silver, a silver alloy, aluminum, an aluminum alloy, and a copper alloy.

11. The glass composite according to claim 5 , further comprising a light-controlling layer having a light-controlling function on the side of the auxiliary infrared radiation layer opposite to the side on which the light-reflecting layer is present.

12. The glass composite according to claim 6 , further comprising a light control layer having a light control function on the side of the infrared radiation rear glass layer opposite to the side on which the auxiliary infrared radiation layer is present.

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