Architectural structural windows with optically transparent self-cooling coatings

Abstract

The present invention relates to a window for a building structure, comprising an optically transparent, self-cooling coating on a substrate. The optically transparent, self-cooling coating has a multi-layer structure comprising a passive cooling layer, a near-infrared radiation absorbing layer, and a near-infrared radiation reflecting layer. The optically transparent, self-cooling coating has a visible light transmittance exceeding approximately 70%. Furthermore, the air temperature beneath the window is reduced by at least approximately 2°C under ventilation conditions and by at least approximately 8°C under insulation conditions.

Description

Technical Field

[0001] The invention relates to a high-transparency self-cooling building structure window film or coating. Background Art

[0002] A greenhouse is a structure with transparent walls and a roof. It helps protect against typhoons, acid rain, and insect pests, while keeping temperatures low in the summer and sufficiently high in the winter. Because greenhouses provide a suitable growing environment for plants or crops, they are often used to cultivate plants or crops with high economic value.

[0003] The walls and roof of a greenhouse determine the spectrum, and therefore the amount of light energy, that enters the greenhouse's interior. This determines the air temperature within the greenhouse. While solar radiation can heat the greenhouse air and keep crops warm in the winter, the same radiation can cause overheating in the summer or when the greenhouse is near the equator. In these cases, greenhouse temperatures can rise above 50°C, which is detrimental to vegetation and reduces plant productivity. Greenhouse productivity can be improved by allowing in a portion of the solar radiation spectrum that contains plant-productive visible light, while shielding the greenhouse from the non-productive infrared spectrum.

[0004] Therefore, given the shortcomings of existing greenhouses in selectively letting in parts of the solar radiation spectrum, a coating system is needed on the walls and roof of the greenhouse to reduce the amount of non-productive solar radiation entering the greenhouse. However, the coating system must remain transparent to a certain extent to the visible light produced. Summary of the Invention

[0005] Therefore, the present invention provides a building window comprising an optically transparent self-cooling coating on a window substrate. This building window comprises an optically transparent self-cooling coating on the window, wherein the optically transparent self-cooling coating comprises a multilayer structure. The multilayer structure includes a passive cooling layer and a near-infrared radiation absorbing layer. The multilayer structure is applied to the building window, wherein the optically transparent self-cooling coating has a visible light transmittance greater than 70%, and reduces the air temperature beneath the building window by at least 2°C under ventilation conditions and by at least 8°C under insulation conditions.

[0006] According to one embodiment, the passive cooling layer includes 20-45 weight percent of a metal oxide, 3.0-55 weight percent of a binder, 1.0-5.0 weight percent of a dispersant, 5.0-10 weight percent of a wetting agent, and 10-50 weight percent of water.

[0007] According to one embodiment, the metal oxide includes silicon oxide, silicon nitride, silicon carbide, or a material with an infrared emissivity of 8-13 μm.

[0008] According to one embodiment, the silicon oxide is spherical, the particle size of the silicon oxide sphere is in the range of 1 to 15 μm, and the particle size of the antimony-doped tin oxide is in the range of 20 to 400 nm.

[0009] According to one embodiment, the dispersant is a low molecular weight dispersant selected from the group consisting of hexametaphosphate, triphosphate, pyrophosphate, citrate, tartrate and succinate, and ammonium cations, Group 1A or Group 2A metal cations.

[0010] According to one embodiment, the near-infrared radiation absorbing layer includes 40-50 weight percent of a metal oxide, 20-40 weight percent of a binder, 0.5-3.0 weight percent of a dispersant, 7.0-15 weight percent of a wetting agent, and 5-15 weight percent of water.

[0011] According to one embodiment, the metal oxide includes antimony tin oxide, indium tin oxide, transition metal oxide, post-transition metal oxide, or metal-like oxide having near-infrared absorption characteristics and high transparency in the visible light region.

[0012] According to one embodiment, the dispersant is a low molecular weight dispersant selected from the group consisting of hexametaphosphate, triphosphate, pyrophosphate, citrate, tartrate and succinate, and ammonium cations, Group 1A or Group 2A metal cations.

[0013] According to one embodiment, the building structure window further comprises a near-infrared radiation reflecting layer comprising 1.0-5.0 weight percent of a binder, 20-40 weight percent of a metal oxide, 2.0-7.0 weight percent of a wetting agent, and 50-70 weight percent of water.

[0014] According to one embodiment, the metal oxide includes zinc oxide, aluminum oxide, or other transition metal oxides, post-transition metal oxides, or metal-like oxides having near-infrared absorption characteristics and high transparency in the visible light region.

[0015] According to one embodiment, the building structure window comprises glass, polyolefin, polyethylene film, polycarbonate, polymethyl methacrylate or polyvinyl chloride.

[0016] The present invention also provides a window for a building structure, comprising a single layer of near-infrared radiation that reflects, absorbs and self-cools on a substrate, wherein the single layer reduces the average transmittance of near-infrared radiation and medium-wavelength infrared radiation of the window to 60% and 25%, respectively, and under ventilation conditions, the air temperature under the window of the building structure is reduced by at least 4°C to 5°C.

[0017] According to one embodiment, the near-infrared radiation reflecting and absorbing self-cooling monolayer includes 10-20 weight percent of titanium oxide particles, at least one of the titanium oxide particles deposited on one or more large particles, 1-10 weight percent of a binder, 5-15 weight percent of a wetting agent, and 65-75 weight percent of water.

[0018] According to one embodiment, the one or more large particles include fly ash, glass beads, hollow glass microspheres, polyethylene terephthalate, macroscopic particles having an average particle size between 1-10 μm, or a combination thereof.

[0019] According to one embodiment, at least one titanium oxide particle is deposited on the surface of one or more macroscopic particles by spraying.

[0020] According to one embodiment, the average particle size of the titanium oxide particles is nanometer-scale.

[0021] According to one embodiment, the substrate includes glass, polyolefin, polyethylene film, polycarbonate, polymethyl methacrylate, and polyvinyl chloride.

[0022] The present invention also provides a greenhouse comprising a building window having an optically transparent self-cooling coating on a window substrate. This building window comprises an optically transparent self-cooling coating on the window, wherein the optically transparent self-cooling coating comprises a multilayer structure. The multilayer structure includes a passive cooling layer and a near-infrared radiation absorbing layer. The multilayer structure is disposed on the building window, wherein the optically transparent self-cooling coating has a visible light transmittance greater than 70%, and reduces the air temperature beneath the building window by at least 2°C under ventilation conditions and by at least 8°C under insulation conditions.

[0023] The present invention also provides a greenhouse comprising a window for a building structure, comprising a near-infrared radiation reflecting, absorbing and self-cooling single layer on a substrate, wherein the single layer reduces the average transmittance of near-infrared radiation and medium-wavelength infrared radiation of the window to 60% and 25%, respectively, and under ventilation conditions, the air temperature under the window of the building structure is reduced by at least 4°C to 5°C.

[0024] The present invention provides chemical formulations for window films or coatings that provide advanced heat and sunlight management for greenhouse building materials. These window films and coatings have the following advantages: (1) high suppression of infrared sunlight; (2) radiative passive cooling; (3) localized heating coating; (4) high visible light transparency; (5) improved thermal efficiency within the greenhouse; scattering effects and internal reflection. BRIEF DESCRIPTION OF THE DRAWINGS

[0025] Figure 1 Schematic diagram depicting the coating on the composite polyethylene film.

[0026] Figure 2A Schematic diagram of a composite polyethylene film with a single-layer coating is depicted.

[0027] Figure 2B Schematic representation of another composite polyethylene membrane containing metal oxides suspended in a polymer matrix is ​​depicted.

[0028] Figure 3 Shown is the transmittance of near-infrared light through coated and uncoated composite polyethylene films.

[0029] Figure 4 Shown is the transmission of near-infrared light through a blank polyethylene film, a metal oxide polyethylene film suspended in a polymer matrix, or a metal oxide polyethylene film deposited on macroparticles.

[0030] Figure 5 Shown from Figure 1 Emission of the obtained composite polyethylene films at different wavelengths.

[0031] Figure 6 Shown from Figure 2A and Figure 2B Emission of the obtained composite polyethylene films at different wavelengths.

[0032] Figure 7A Schematic diagram depicting a composite polyethylene membrane with a passive cooling coating.

[0033] Figure 7B Schematic diagram depicting a composite polyethylene film without a passive cooling coating.

[0034] Figure 8 Shown are the temperatures of the composite polyethylene films with and without passive cooling at different points in time.

[0035] Figure 9 Shown is the visible light transmission through the composite polyethylene films with or without coating.

[0036] Figure 10 Visible light transmission through commercial polymer films is shown.

[0037] Figure 11 Shows the Figure 1 Obtain the ventilation temperature under the composite polyethylene film.

[0038] Figure 12 Shows the Figure 1 The unventilated temperature under the composite polyethylene film was obtained.

[0039] Figure 13Shown are the temperatures at different time points for a blank polyethylene film, a metal oxide polyethylene film suspended in a polymer matrix, or a metal oxide polyethylene film deposited on large particles.

[0040] Figure 14 Two different arrangements of antimony tin oxide and silicon dioxide coatings with respect to the substrate are depicted.

[0041] Figure 15 Shown by Figure 14 Visible light transmittance for two different arrangements shown.

[0042] Figure 16 Two different arrangements between the polyurethane dispersion (PUD) coating and the substrate are depicted.

[0043] Figure 17 Shown by Figure 16 Visible light transmittance for two different arrangements shown. DETAILED DESCRIPTION

[0044] To reduce the amount of unproductive light entering a greenhouse, the present invention provides a window having an optically clear self-cooling coating on a window substrate. Figure 1 As shown, the optically transparent self-cooling coating has a multi-layer structure, including a passive cooling layer having a formulation A, a near-infrared radiation absorbing layer having a formulation B, and an optional near-infrared radiation reflecting layer having a formulation C. In some embodiments, the window material itself has radiation-reflecting properties. In other embodiments of the present invention, the multi-layer structure may not include the near-infrared radiation reflecting layer.

[0045] In one embodiment, the passive cooling layer, the near-infrared radiation absorbing layer, and the near-infrared radiation reflecting layer comprise at least one metal oxide capable of absorbing infrared radiation, reflecting infrared radiation, and emitting long-wave infrared light.

[0046] In another embodiment, the passive cooling layer comprises at least one metal oxide, a binder, a dispersant, a wetting agent, and water. The near-infrared radiation absorbing layer comprises at least two metal oxides (at least one for infrared absorption and at least one for infrared emission), a binder, a dispersant, a wetting agent, and water. The near-infrared radiation reflecting layer comprises a binder, at least one metal oxide, a wetting agent, and water. For example, the compositions of Formulations A, B, and C are listed in Tables 1, 2, and 3, respectively.

[0047] Table 1 - Composition of Formulation A

[0048] Element Weight percentage (wt%) water 42.09％ Silica spheres 42.09％ Sodium hexametaphosphate 2.80％ Polyurethane Dispersion-1591 3.26％ Wetting agent (J1703) 9.77％

[0049] In Table 1, silica spheres are used as the metal oxide, sodium hexametaphosphate is used as the dispersant, polyurethane dispersion-1591 is used as the binder, and the wetting agent J1703 is a mixture of α-phenylmethyl-ω-[(1,1,3,3-tetramethylbutyl)phenoxy]-poly(oxy-1,2-ethylene), polyoxyethylene octylphenol ether, and polyethylene glycol. In addition to silica spheres, other materials with an infrared emissivity of 8-13 μm can also be used in the present invention, including but not limited to silicon nitride and silicon carbide. The size of the silica spheres ranges from about 1 micron to about 15 microns. In some embodiments, a smaller silica sphere size range can be used, for example, silica spheres between 7 and 9 microns can be used.

[0050] The dispersant used in the present invention is a low molecular weight dispersant. In addition to sodium hexametaphosphate, other low molecular weight dispersants can also be used, such as hexametaphosphoric acid, triphosphate, pyrophosphate, citrate, tartrate and succinate, as well as ammonium cations, Group 1A or Group 2A metal cations (e.g., sodium ions, magnesium ions, potassium ions, calcium ions, etc.).

[0051] Table 2 - Composition of Formulation B

[0052] Element Weight percentage (wt%) water 10.52％ Silica spheres 10.52％ Sodium hexametaphosphate 0.70％ Polyurethane Dispersion-1591 34.74％ Wetting agent (J1703) 9.59％ Antimony tin oxide 33.93％

[0053] In Table 2, silica spheres are used as the metal oxide, sodium hexametaphosphate as the dispersant, polyurethane dispersion-1591 as the binder, J1703 as the wetting agent, and antimony tin oxide as the metal oxide with infrared absorption properties. The silica spheres are a metal oxide with infrared emissivity in the 8-13 μm range. Since the near-infrared radiation absorbing layer acts as a heat sink when exposed to sunlight, silica can be used to cool the layer through its infrared emission properties. The near-infrared radiation absorbing layer of Formulation B, acting in conjunction with the passive cooling layer, can further reduce the indoor temperature.

[0054] In addition to antimony tin oxide, Formulation B can also utilize other metal oxides, such as indium tin oxide, transition metal oxides, post-transition metal oxides, and metalloid oxides with near-infrared absorption and high transparency in the visible region. In addition to silica spheres, Formulation B can also utilize other materials with infrared emissivity of 8-13 μm, including but not limited to silicon nitride and silicon carbide.

[0055] The dispersant used in Formulation B is a low molecular weight dispersant. In addition to sodium hexametaphosphate, other low molecular weight dispersants may be used in Formulation B, such as hexametaphosphate, triphosphate, pyrophosphate, citrate, tartrate, and succinate, as well as ammonium cations, Group 1A or Group 2A metal cations (e.g., sodium ion, magnesium ion, potassium ion, calcium ion, etc.).

[0056] Table 3 - Composition of Formulation C

[0057] Element Weight percentage (wt%) water 60.00％ Polyurethane Dispersion-1591 3.53％ Titanium oxide dispersion (TIO-WPR010) 31.76％ Wetting agent (J1703) 4.71％

[0058] In Table 3, PUD-1591 is used as a binder, titanium oxide dispersion (TIO-WPR010) is used as a metal oxide, and J1703 is used as a wetting agent. In addition to titanium oxide dispersion (TIO-WPR010), other metal oxides such as zinc oxide, aluminum oxide, or other transition metal oxides, post-transition metal oxides, or metalloid oxides with near-infrared reflectivity and high transparency in the visible region can also be used in Formulation C.

[0059] The traditional method of coating transparent substrates is by sputtering, but it is expensive and has limitations on the size of the substrate. In contrast, the formulation of the present invention allows the coating to be applied by spraying, which is relatively more economical, especially when using very large films. The film of the present invention can be formed in large areas of about at least 1 square meter, at least 2 square meters or more. The thickness of the coating varies about the median of the (design) thickness, for example, plus or minus 10-20% of the (design) thickness. Such a thickness level is sufficient to minimize the visual distortion of the window. That is, for applications such as greenhouse windows, a highly uniform thickness is not required because allowing users to view the external environment through the window is not the main purpose. By having the flexibility of thickness variation with a median "design thickness", large-area, economically viable coatings can be formed. The median thickness of each layer is about 10-20μm.

[0060] In one embodiment, the substrate window comprises glass or a polymer film, such as polyethylene (PE), polyolefin, polycarbonate, polymethyl methacrylate, and polyvinyl chloride films. The base materials for these coatings are commonly used as greenhouse wall materials. For example, composite polyethylene films can reduce the temperature beneath the film by 2°C to 8°C, depending on the ventilation conditions beneath the film. This keeps the air temperature beneath the film within a controlled range, ideal for plant growth.

[0061] In another aspect, the present invention provides a window comprising a near infrared radiation reflecting, absorbing and self-cooling monolayer on a substrate. Figure 2A As shown, the near-infrared radiation reflecting, absorbing and self-cooling monolayer has the formula E. For the control group, Figure 2B Another composite polyethylene film having a metal oxide suspended in a polymer matrix is ​​shown having Formulation D.

[0062] In one embodiment, the near-infrared radiation reflecting, absorbing, and self-cooling monolayer is composed of at least one titanium oxide particle deposited on one or more macroparticles, a binder, a wetting agent, and water. The ingredients of the control Formulation D are listed in Table 4, and the ingredients of Formulation E are listed in Table 5.

[0063] Table 4 - Composition of Control Group Formulation D

[0064]

[0065]

[0066] Table 5 - Composition of Control Group Formulation E

[0067] Element Weight percentage (wt%) Polyurethane Dispersion-1591 3.37％ water 70.79％ Titanium oxide deposited on fly ash 16.85％ Wetting agent (J1703) 8.99％

[0068] In Tables 4 and 5, polyurethane dispersion-1591 was used as a binder, J1703 was used as a wetting agent, and titanium oxide dispersion (TIO-WPR010) was used as a metal oxide.

[0069] The binder matrix contains randomly dispersed and suspended metal oxide particles. The present invention also deposits metal oxide on the surface of large particles. Compared to metal oxide particles randomly dispersed and suspended in the binder matrix, the large particles with deposited surface material significantly increase the reflectivity of solar infrared light by more than 20%.

[0070] In one embodiment, at least one titanium oxide particle is deposited on the surface of one or more large particles by spraying. The one or more large particles may include, but are not limited to, fly ash, glass beads, hollow glass microspheres, polyethylene terephthalate, or large particles with a particle size range of 1-10 μm.

[0071] The following examples illustrate the present invention and are not intended to limit the present invention.

[0072] Example 1

[0073] Compared with polyethylene film without any coating, Figure 3 It was shown that a composite polyethylene film including a passive cooling layer having formulation A, a near-infrared radiation absorbing layer having formulation B, and a near-infrared radiation reflecting layer having formulation C can significantly reduce the amount of near-infrared light (700-2500 nm) passing through the composite PE film.

[0074] On average, 86% of near-infrared light can pass through the polyethylene film without a coating, but in the present invention, only 25% of the near-infrared light passes through the composite polyethylene film. The coating has an inhibition rate of more than 60% for near-infrared light.

[0075] Example 2

[0076] Figure 4The transmittance of near-infrared light through a single-layer coating on polyethylene film is shown. The results indicate that depositing the metal oxide on large particles (prepared in Formulation E) improves near-infrared light suppression. In contrast, when the metal oxide is randomly dispersed and suspended in the polymer matrix (Formulation D), the average transmittance is approximately 83%, but the transmittance decreases significantly by over 20%, to only 61%.

[0077] Example 3

[0078] like Figure 5 As shown, the coatings prepared by formulas A, B and C have a strong long-wave infrared light emission range (7000nm-14000nm), which is the so-called sky window. Within this range, the light emitted by the coating of the present invention is only slightly absorbed by the atmosphere. Most of the light leaves the atmosphere and enters space. However, the blank polyethylene film does not emit within this wavelength range. This means that the coating of the present invention can cool the greenhouse by radiation without the need for an external cooling system that provides energy.

[0079] Example 4

[0080] refer to Figure 6 The metal oxide coating deposited on large particles prepared by Formulation E exhibited radiative passive cooling, while the metal oxide coating prepared by Formulation D, which was randomly dispersed and suspended in a polymer matrix, did not clearly exhibit this function.

[0081] Example 5

[0082] In another aspect, the present invention also provides a composite polyethylene film having three passive cooling coatings. The first layer is prepared from Formulation F, the second layer is prepared from Formulation G, and the third layer is prepared from Formulation H ( Figure 7A ). The compositions of Formulation F, Formulation G, and Formulation H are listed in Table 5, Table 6, and Table 7, respectively.

[0083] For the control group, Figure 7B A composite PE film without a passive cooling coating is shown.

[0084] Table 6 - Composition of Control Group Formulation Formula F

[0085] Element Weight percentage (wt%) Polyurethane Dispersion-1591 3.33％ water 56.67％ Titanium oxide dispersion (TIO-WPR010) 30.00％ Wetting agent (J1703) 10.00％

[0086] In Table 6, PUD-1591 was used as a binder, TIO-WPR010 was used as a metal oxide, and J1703 was used as a wetting agent.

[0087] Table 7 - Composition of Control Group Formulation G

[0088] Element Weight percentage (wt%) Polyurethane Dispersion-1591 44.81％ Antimony Tin Oxide Dispersion (ATO-WP030) 44.81％ Wetting agent (J1703) 9.43％ Commercially available wetting agent (BYK-346) 0.94％

[0089] In Table 7, PUD-1591 is used as a binder, antimony tin oxide is used as a metal oxide having infrared absorption properties, J1703 is used as a wetting agent, and BYK-346 is another commercially available wetting agent.

[0090] Table 8 - Composition of Control Group Formulation Formula H

[0091] Element Weight percentage (wt%) Polyurethane Dispersion-1591 19.19％ water 37.15％ Sodium hexametaphosphate 2.48％ Silica spheres 37.15％ Wetting agent (J1703) 4.04％

[0092] In Table 8, polyurethane dispersion-1591 was used as a binder, sodium hexametaphosphate was used as a dispersant, silica spheres were used as a metal oxide; and J1703 was used as a wetting agent.

[0093] Example 6

[0094] refer to Figure 8 , which shows that the blank polyethylene film is heated under sunlight. It also shows that the composite polyethylene film without passive cooling layer (prepared by formulations F and G, Figure 7B , control group), under sunlight, the temperature of this polyethylene film also rises, making the temperature of the space 7°C higher than that of the blank polyethylene film. By adding a passive cooling component to the coating, the composite polyethylene film of the present invention (prepared by formulas F, G and H, Figure 7A ) reduces the space temperature by 2°C. Therefore, passive cooling coatings will cause energy loss through light radiation in this wavelength range, which helps to cool the greenhouse.

[0095] Example 7

[0096] Figure 9 The visible light transmittance through the blank polyethylene film was about 90%. Figure 1 The prepared composite polyethylene film has a coating that transmits less than 20% of visible light, that is, more than 70% of visible light can pass through the composite polyethylene film.

[0097] Example 8 (control sample)

[0098] Figure 10 It shows that the visible light transmittance through commercial polymer films for thermal management is generally less than 60%, which is significantly lower than the visible light transmittance of the composite polyethylene film of the present invention.

[0099] Example 9

[0100] Example 9 uses Figure 1 The composite polyethylene film obtained, in this example, when the air in the area below the composite polyethylene film is well ventilated (ie, can be exchanged with the air outside the greenhouse), Figure 11 It was shown that the temperature of the space under the composite polyethylene film was reduced by 2°C relative to the temperature of the space under the blank polyethylene film.

[0101] When used Figure 1 In the case of the composite polyethylene film shown, and the air below the composite polyethylene film is insulated, Figure 12 The results show that compared with the blank polyethylene film, the cooling effect of the composite polyethylene film can reach at least 8°C. Therefore, the cooling effect of the composite polyethylene film of the present invention helps to stabilize the temperature in the greenhouse and reduce the energy consumption of the greenhouse cooling system.

[0102] Example 10

[0103] The coating of Example 10 is based on Figure 2A Preparation of coatings of metal oxides deposited on large particles. Figure 13 , This figure shows that the coating of the present invention has a significant cooling effect on the air. Figure 2B The prepared coating (metal oxides randomly dispersed and suspended in a polymer matrix) had a 4-5°C drop in the air temperature below the coating of the present invention.

[0104] Example 11

[0105] When using a reflective polymer such as polycarbonate as a window substrate, the layer arrangement can make a significant difference in visible light transmittance. Figure 14 and Figure 15 As shown, Arrangement 2 exhibits higher transmittance in the visible light region compared to Arrangement 1. This phenomenon is likely due to the light scattering and internal reflection of the silica particles. In Arrangement 1, some light is reflected by the polycarbonate, which serves as a top layer to block the light source, resulting in lower visible light transparency. In Arrangement 2, on the other hand, the silica particles in the top layer scatter more light. Furthermore, "reflected light" from the bottom polycarbonate substrate is also focused back by the silica particles. This scattering and internal reflection of the silica particles significantly improves visible light transmittance.

[0106] Example 12

[0107] Figure 16 and Figure 17 The visible light transmission spectra of two control samples without antimony tin oxide coating and silica coating on a polycarbonate substrate are shown. As shown in the spectra, there is no significant difference in visible light transmittance when the polycarbonate film is directly facing or not directly facing the light source. These results further demonstrate the influence of layer arrangement and silica particles on visible light transmittance.

Claims

1. A window for a building structure, characterized in that: The window is provided with an optically transparent self-cooling coating, and the optically transparent self-cooling coating comprises a multi-layer structure, wherein the multi-layer structure comprises: a passive cooling layer, wherein the passive cooling layer comprises: 20-45 weight percent of a first metal oxide; 3.0-55 weight percent of a binder; 1.0-5.0 weight percent of a dispersant; 5.0-10 weight percent of a wetting agent; and 10-50 weight percent of water; A near-infrared radiation reflecting layer, wherein the near-infrared radiation reflecting layer comprises: 1.0-5.0 weight percent of the binder; 20-40 weight percent of the second metal oxide; 2.0-7.0 weight percent of the wetting agent; and 50-70 weight percent of water; and a near-infrared radiation absorbing layer, wherein the near-infrared radiation absorbing layer comprises: 40-50 weight percent of a third metal oxide; 20-40 weight percent of the binder; 0.5-3.0 weight percent of the dispersant; 7.0-15 weight percent of the wetting agent; and 5-15 weight percent of water; The multi-layer structure is arranged on a building structure window; Wherein, the visible light transmittance of the optically transparent self-cooling coating is greater than 70%, Wherein, under ventilation conditions, the air temperature under the windows of the building structure is reduced by at least 2°C, wherein, under thermal insulation conditions, the air temperature under the windows of the building structure is reduced by at least 8°C, wherein the optically transparent self-cooling coating has an inhibition rate of greater than 60% for near-infrared light in the range of 700-2500nm and has a long-wave infrared light emission range of 7000nm-14000nm; The first, second and third metal oxides have high transparency in the visible light region.

2. The window provided with an optically transparent self-cooling coating according to claim 1, characterized in that: The first metal oxide includes silicon oxide, silicon nitride, silicon carbide or a material with an infrared emissivity of 8-13 μm.

3. The window provided with an optically transparent self-cooling coating according to claim 2, characterized in that: The silicon oxide is spherical, and the particle size of the silicon oxide sphere is in the range of 1 to 15 μm.

4. The window provided with an optically transparent self-cooling coating according to claim 1, characterized in that: The dispersant is a low molecular weight dispersant selected from the group consisting of hexametaphosphate, triphosphate, pyrophosphate, citrate, tartrate and succinate, and ammonium cations, Group 1A or Group 2A metal cations.

5. The window provided with an optically transparent self-cooling coating according to claim 1, characterized in that: The third metal oxide includes antimony tin oxide, indium tin oxide, transition metal oxide, post-transition metal oxide, and metal-like oxide with near-infrared absorption characteristics and high transparency in the visible light region, wherein the particle size of the antimony tin oxide is in the range of 20 to 400 nm.

6. The window provided with an optically transparent self-cooling coating according to claim 1, wherein: The second metal oxide includes zinc oxide, aluminum oxide or other transition metal oxides, post-transition metal oxides, and metal-like oxides having near-infrared absorption characteristics and high transparency in the visible light region.

7. The window provided with an optically transparent self-cooling coating according to claim 1, characterized in that: The window comprises glass, polyolefin, polyethylene film, polycarbonate, polymethyl methacrylate or polyvinyl chloride.

8. A window for a building structure, characterized in that: The window is provided with a near-infrared radiation reflecting, absorbing and self-cooling monolayer on a substrate to reduce the average transmittance of near-infrared radiation and mid-wavelength infrared radiation of the window to 60% and 25%, respectively, wherein the temperature of the air under the window is reduced by at least 4°C to 5°C under ventilation conditions; Wherein, the near-infrared radiation reflecting and absorbing self-cooling single layer comprises: 10-20 weight percent of titanium oxide particles, at least one of the titanium oxide particles being deposited on one or more large particles, the one or more large particles comprising fly ash, glass beads, hollow glass microspheres, polyethylene terephthalate, large particles having an average particle size between 1 and 10 μm, or a combination thereof; 1-10 weight percent of a binder; 5-15 weight percent of a wetting agent; and 65-75 weight percent water.

9. The window with a single layer of near infrared radiation reflecting, absorbing and self-cooling according to claim 8, characterized in that The at least one titanium oxide particle is deposited on the surface of the one or more large particles by spraying.

10. The window with a single layer of near infrared radiation reflecting, absorbing and self-cooling according to claim 8, characterized in that: The average particle size of the titanium oxide particles is nanometer scale.

11. The window with a single layer of near infrared radiation reflecting, absorbing and self-cooling according to claim 8, characterized in that: The substrate includes glass, polyolefin, polyethylene film, polycarbonate, polymethyl methacrylate and polyvinyl chloride.

12. A greenhouse, characterized in that: The greenhouse comprises the window provided with an optically clear self-cooling coating according to claim 1 .

13. A greenhouse, characterized in that: The greenhouse comprises the window of claim 8 provided with a single layer of near infrared radiation that reflects, absorbs and self-cools.

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