A photothermal composite transparent substrate and a preparation method thereof

Abstract

This invention discloses a photothermal composite transparent substrate and its preparation method, belonging to the technical field of transparent substrate functional coating and sandwich composite structure preparation. The photothermal composite transparent substrate comprises, from bottom to top: a first transparent substrate, a first hybrid hydrogel coating, a photothermal absorption coating, a second hybrid hydrogel coating, and a second transparent substrate; wherein the first hybrid hydrogel coating and the second hybrid hydrogel coating are respectively disposed on the upper and lower sides of the photothermal absorption coating, and together with the photothermal absorption coating, constitute a sandwich-type composite anti-fogging functional unit. The photothermal composite transparent substrate provided by this invention maintains high transparency while achieving solar-driven heating and anti-fogging / defogging effects, and is beneficial to improving the long-term stability and service reliability of the photothermal absorption coating. It can be applied to building lighting components, transparent windows for vehicles, automotive glass, and transparent covers for automotive headlights, taillights, and other vehicle lighting components.

Description

Technical Field

[0001] This invention relates to the field of transparent substrate functional coating and sandwich composite structure preparation technology, and particularly to a photothermal composite transparent substrate and its preparation method. Background Technology

[0002] In applications such as building lighting, transparent windows in transportation vehicles, and automotive lighting, transparent substrates are often exposed to environments with large temperature differences, high humidity, and alternating hot and cold conditions. Taking vehicles as an example, windshields, side windows, and transparent covers for headlights and taillights are prone to condensation and the formation of fog droplets or water films after rain, fog, low temperatures, high humidity, or car washes. This reduces light transmittance, visibility, and lighting clarity, affecting driving safety and aesthetic reliability. Existing automotive glass anti-fogging and defogging technologies primarily employ electrothermal laminated glass solutions. For instance, patent CN201119031Y discloses a heat-reflective coated laminated glass with intelligent electrothermal heating. This glass includes an outer glass sheet, an inner glass sheet, and an intermediate interlayer. A low-emissivity film is applied to either the outer or inner glass sheet, and conductive busbars are positioned on both sides of the low-emissivity film. This solution heats the low-emissivity film by electricity, causing the glass to heat up quickly, thus achieving defrosting and defogging functions. In this existing technology, the sandwich structure serves as a connection and support, the low-emissivity film acts as a heating layer, and the conductive busbar provides power. These three components work together to achieve active heating and defogging of the entire glass panel. While it can achieve defogging to a certain extent, several shortcomings remain: First, this type of technology typically relies on external electrical energy to drive heating, resulting in relatively high energy consumption. Second, in environments with low temperatures and high humidity, the defogging effect of existing solutions may still be limited. Third, this type of solution is primarily designed around the glass substrate, lacking sufficient compatibility with commonly used transparent plastic materials in automotive lights, such as polycarbonate (PC) and polymethyl methacrylate (PMMA). Fourth, once the sandwich sealing structure or surface functional layer is damaged, problems such as internal bubbling, fogging, and reduced light transmittance can easily occur, leading to complex maintenance, repair, and replacement.

[0003] Patent CN117645414A discloses a method for preparing a highly transparent superhydrophobic / photothermal composite anti-fog glass. This anti-fog glass primarily involves constructing a photothermal coating on the surface of a single piece of glass, and forming a superhydrophobic surface through plasma etching and low surface energy modification. It mainly relies on surface hydrophobic drainage and photothermal heating. For automotive headlight transparent covers, PC and PMMA materials are more sensitive to solvents, temperature, and surface etching conditions. Furthermore, the internal space of automotive headlights is relatively enclosed, and during service, they undergo photothermal aging, thermal cycling, and humid environments. Therefore, solutions relying solely on a single surface hydrophobic coating or a single photothermal coating still need improvement in long-term stability, substrate compatibility, and anti-fog persistence. For these reasons, existing technologies cannot simultaneously achieve high transparency, low energy consumption, excellent anti-fog and defogging performance, good durability, and compatibility with various transparent substrates such as glass, PC, and PMMA. Therefore, a new photothermal composite transparent substrate and its preparation method are needed to overcome the shortcomings of existing technologies. Summary of the Invention

[0004] The purpose of this invention is to provide a photothermal composite transparent substrate and its preparation method to solve the problems of high energy consumption, limited anti-fog effect in low temperature and high humidity environments, insufficient compatibility with automotive lighting materials such as PC and PMMA, and complex maintenance of existing anti-fog transparent components, and to achieve high transparency, good anti-fog and defogging performance and large-scale preparation.

[0005] To achieve the above objectives, firstly, the present invention provides a method for preparing a photothermal composite transparent substrate, comprising the following steps:

[0006] S1: Preparation of the first hybrid hydrogel coating

[0007] The first transparent substrate is cleaned and set aside. A compound containing highly chemically active components is used as a precursor, dissolved in a solvent, and subjected to hydrolysis and condensation reactions at 20-50°C and pH 2.0-6.0 to form a stable transparent sol system in the solution. The first transparent substrate is immersed in the above sol by an impregnation method. After aging, the resulting sol particles polymerize to form a three-dimensional network structure gel. After drying, the above structure gel is heat-treated and heat-cured for 2-3 hours to obtain a first hybrid hydrogel coating on the surface of the first transparent substrate.

[0008] The first transparent substrate is glass, polycarbonate (PC) material, or polymethyl methacrylate (PMMA) material;

[0009] The precursor is any one or more of the following: polyvinyl alcohol / polyN-isopropylacrylamide composite hydrogel, tannic acid / silk fibroin photothermal composite hydrogel, thermochromic polyvinyl butyral film, black phosphorus hybrid hydrogel, organosilicon sol, acrylic modified polyurethane, acrylic resin, polyurethane, water glass or silica sol.

[0010] When the first transparent substrate is glass, the solvent is any one or more of water, ethanol, acetone, n-propanol, isopropanol, and ethylene glycol; the thermosetting temperature is 60℃-110℃.

[0011] When the first transparent substrate is polycarbonate (PC) or polymethyl methacrylate (PMMA), the solvent is any one or more of water, ethanol, or isopropanol; the thermosetting temperature is 60℃-90℃.

[0012] S2: Preparation of the photothermal absorption layer

[0013] The photothermal absorption layer is prepared by low-temperature deposition or solution coating. When the photothermal absorption layer is prepared by low-temperature deposition, the specific steps include:

[0014] Low-temperature deposition: Photothermal absorption layer nanomaterials are selected for deposition, and appropriate reaction gases are selected according to different nanomaterials; the transparent substrate with the first hybrid hydrogel coating obtained in step S1 is placed in the reaction vessel, and after evacuation, a protective gas is introduced for pre-purging, and the selected reaction gas is introduced; during the deposition process, the gas pressure is maintained in a low-pressure range. After the deposition reaction proceeds for 20 minutes, the supply of reaction gas is stopped, and the protective gas is continued to purge the reaction chamber. At the same time, the residual reaction gas and by-products in the reaction chamber are discharged using a vacuum system; after the reaction chamber cools to room temperature, the sample is taken out, and a substrate with a photothermal absorption layer deposited on the surface of the first hybrid hydrogel layer is obtained; during the deposition process, when the transparent substrate is glass, the substrate temperature is controlled at 60-120℃; when the transparent substrate is PC material, the substrate temperature is controlled at 40-80℃; when the transparent substrate is PMMA, the substrate temperature is controlled at 40-60℃ during the deposition process.

[0015] The photothermal absorption layer nanomaterials include any one or more of the following: gold nanoparticles, copper sulfide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, nickel nanoparticles, Cu7S4 nanoparticles, CuCoMnOx, cesium tungsten oxide nanoparticles, indium tin oxide nanoparticles, CuS nanoparticles, SiC nanoparticles, PbS nanoparticles, GaAs nanoparticles, GaN nanoparticles, polythiophene organic polymers, polypyrrole organic polymers, polyaniline organic polymers, or polyacetylene organic polymers.

[0016] The reacting gases include any one or more of the following: methane, ethylene, acetylene, silane, borane, ammonia, nitrogen, argon, hydrogen, or oxygen;

[0017] When preparing a photothermal absorption layer using a solution coating method, the specific steps include:

[0018] Photothermal absorbing nanomaterials are added to a solvent to prepare a photothermal dispersion with a mass concentration of 0.1–5 mg / mL. Then, a dispersant or binder is added to stabilize the photothermal particles and enhance their bonding force with the hydrogel coating. The mixture is magnetically stirred at room temperature for 30–60 min and then ultrasonically dispersed for 20–40 min to obtain a uniform and stable photothermal coating solution.

[0019] A transparent substrate with a first hybrid hydrogel coating is fixed on a horizontal coating stage. Gas is introduced to blow away surface dust. Then, the photothermal coating liquid is uniformly coated onto the surface of the first hybrid hydrogel coating by spin coating, blade coating, spray coating or dip coating. After coating, the sample is placed in a forced-air drying oven for low-temperature drying treatment. For glass substrates, drying is carried out at 60–100℃ for 1–2 hours. For PC or PMMA substrates, the drying temperature is controlled at 40–70℃.

[0020] After cooling to room temperature, rinse the sample surface with deionized water or ethanol, and then dry it again at 40–60°C for 30–60 min to obtain a substrate with a photothermal absorption layer coated on the surface of the first hybrid hydrogel layer.

[0021] The photothermal absorbing nanomaterial is one or more of the following: cesium tungsten oxide nanoparticles, copper sulfide nanoparticles, CuS nanoparticles, indium tin oxide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, polypyrrole, and polyaniline materials.

[0022] S3: Preparation of photothermal composite transparent substrate

[0023] According to the method in step S1, another hybrid hydrogel coating, namely the second hybrid hydrogel coating, is prepared on the surface of the photothermal absorption layer. The second transparent substrate is laid on the hybrid hydrogel coating, and after heating and pressing, a photothermal composite transparent substrate is obtained. The second transparent substrate is glass, polycarbonate (PC) material or polymethyl methacrylate (PMMA) material. When the second transparent substrate is glass, the heating and pressing temperature is 60-120℃; when the second transparent substrate is PC material, the heating and pressing temperature is 40-80℃; when the second transparent substrate is PMMA material, the heating and pressing temperature is 40-60℃.

[0024] Preferably, the glass materials of the first transparent substrate and the second transparent substrate are float glass or tempered glass.

[0025] In addition, the present invention also provides a photothermal composite transparent substrate prepared according to the above-described method for preparing photothermal composite transparent substrate.

[0026] Preferably, the photothermal composite transparent substrate comprises, from bottom to top: a first transparent substrate, a first hybrid hydrogel coating, a photothermal absorption coating, a second hybrid hydrogel coating, and a second transparent substrate. The first hybrid hydrogel coating and the second hybrid hydrogel coating are respectively bonded to opposite sides of the photothermal absorption coating to form a double-sided clamping structure for the photothermal absorption coating. The double-sided clamping structure and the photothermal absorption coating together constitute a photothermal-moisture-absorbing synergistic anti-fogging unit, which provides support, bonding, moisture absorption and regulation, and auxiliary transparency functions, and is beneficial to improving the interlayer bonding stability, heat transfer capacity, and anti-fogging and defogging performance of the photothermal absorption coating.

[0027] The photothermal absorption coating is used to absorb ultraviolet, near-infrared and visible light in the solar spectrum and convert them into heat energy; the first transparent substrate and the second transparent substrate are used to provide the mechanical strength, transparency and safety required for the overall structure.

[0028] Preferably, the transmittance of the photothermal composite transparent substrate surface in the visible light wavelength range is higher than 65%.

[0029] Preferably, the effective solar thermal absorption spectrum range of the photothermal absorption coating is 0.25-2.5 μm, and the absorption rate is not less than 80% within this band.

[0030] Beneficial effects of the present invention

[0031] The photothermal composite transparent substrate provided by this invention achieves significant photothermal heating and anti-fogging / defogging effects while maintaining high transparency by setting a hybrid hydrogel coating and a photothermal absorption coating between two transparent substrates. First, compared with ordinary electrothermal laminated glass or electrothermal vehicle headlight defogging structures, it has independent anti-fogging and defogging performance, which can reduce the consumption of the vehicle's own electrical energy and has energy-saving and environmental protection effects. Second, the transparent substrate can be made of glass, PC, or PMMA materials, which can cover the application needs of automotive glass, transparent building components, and transparent covers for automotive headlights, taillights, and other vehicle headlights. At the same time, the double-sided hybrid hydrogel layers can clamp and encapsulate the photothermal absorption coating for protection, which is beneficial to improving interface stability and long-term service reliability, and still has good anti-fogging ability and potential anti-frost and anti-icing effects in low temperature and high humidity environments. Furthermore, this application constructs a composite anti-fogging functional unit of "hydrogel / photothermal absorption layer / hydrogel". In high humidity or low temperature environments, the hybrid hydrogel coating can preferentially adsorb and fix water vapor near the interlayer interface, reducing the possibility of water vapor rapidly nucleating and forming fog droplets on the surface of the transparent substrate. When the photothermal absorption coating is irradiated by sunlight, the heat generated can further promote the desorption, diffusion and evaporation of adsorbed water in the hydrogel layer, thereby forming a synergistic anti-fogging mechanism of "first absorbing moisture to suppress fog, then photothermal defogging". Compared with the solution of only setting a single photothermal coating or superhydrophobic photothermal coating on the surface of glass, PC or PMMA, it not only improves the anti-fogging and defogging effect, but also reduces the impact of external pollution, friction, cleaning and environmental water vapor erosion on the photothermal layer, thereby improving the long-term stability and reliability of the composite transparent substrate.

[0032] Furthermore, this invention employs a process route combining solution gelation, rapid heat treatment, chemical vapor deposition, and thermo-pressing, resulting in a simple and easy-to-operate preparation process suitable for mass and large-scale production. Attached Figure Description

[0033] Figure 1 This is a schematic diagram illustrating the preparation of the photothermal composite transparent substrate provided by the present invention.

[0034] Figure 2 A comparison chart of the average temperature rise of ordinary glass, electrothermal laminated glass, and photothermal composite transparent substrate in Embodiment 1 of the present invention.

[0035] Figure 3 The spectral transmission spectrum of the electrothermal laminated glass and photothermal composite transparent substrate in Embodiment 1 of the present invention.

[0036] Figure 4 A comparison of the spectral absorption curves of the photothermal composite transparent substrate and ordinary glass in Embodiment 1 of the present invention;

[0037] Figure 5Electron micrographs of the photothermal coated glass and the photothermal composite transparent substrate in Embodiment 1 of the present invention;

[0038] Figure 6 The anti-fogging test diagram of the photothermal coated glass and photothermal composite transparent substrate in Embodiment 1 of the present invention;

[0039] Figure 7 A comparison diagram of the average temperature rise of the photothermal coated glass and the photothermal composite transparent substrate in Embodiment 1 of the present invention.

[0040] In the figure, 1 is the first transparent substrate; 2 is the first hybrid hydrogel coating; 3 is the photothermal absorption coating; 4 is the second hybrid hydrogel coating; and 5 is the second transparent substrate. Detailed Implementation

[0041] First, this invention provides a method for preparing a photothermal composite transparent substrate, comprising the following steps:

[0042] S1: Preparation of the first hybrid hydrogel coating

[0043] The first transparent substrate 1 is cleaned and set aside. A compound containing highly chemically active components is used as a precursor, dissolved in a solvent, and subjected to hydrolysis and condensation reactions at 20-50°C and pH 2.0-6.0 to form a stable transparent sol system in the solution. The first transparent substrate 1 is immersed in the above sol by impregnation. After aging, the resulting sol polymerizes between the gel particles to form a three-dimensional network structure gel. After drying, the above structure gel is heat-treated and heat-cured for 2-3 hours to obtain a first hybrid hydrogel coating 2 on the surface of the first transparent substrate 1.

[0044] The first transparent substrate 1 is made of glass, polycarbonate (PC) or polymethyl methacrylate (PMMA); preferably, the glass material of the first transparent substrate 1 and the second transparent substrate 5 is float glass or tempered glass.

[0045] The precursor is any one or more of the following: polyvinyl alcohol / polyN-isopropylacrylamide composite hydrogel, tannic acid / silk fibroin photothermal composite hydrogel, thermochromic polyvinyl butyral film, black phosphorus hybrid hydrogel, organosilicon sol, acrylic modified polyurethane, acrylic resin, polyurethane, water glass or silica sol.

[0046] When the first transparent substrate 1 is glass, the solvent is any one or more of water, ethanol, acetone, n-propanol, isopropanol, and ethylene glycol; the thermosetting temperature is 60℃-110℃.

[0047] When the first transparent substrate 1 is a polycarbonate (PC) material or a polymethyl methacrylate (PMMA) material, the solvent is any one or more of water, ethanol or isopropanol; the thermosetting temperature is 60℃-90℃; used to control the curing temperature not to exceed the heat distortion temperature of the transparent substrate;

[0048] S2: Preparation of the photothermal absorption layer

[0049] The photothermal absorption layer is prepared by low-temperature deposition or solution coating. When the photothermal absorption layer is prepared by low-temperature deposition, the specific steps include:

[0050] Low-temperature deposition: Photothermal absorption layer nanomaterials are selected for deposition, and appropriate reaction gases are selected according to different nanomaterials; the transparent substrate with the first hybrid hydrogel coating 2 obtained in step S1 is placed in the reaction vessel, and after evacuation, protective gas is introduced for pre-purging, and the selected reaction gas is introduced; during the deposition process, the gas pressure is maintained in a low-pressure range. After the deposition reaction proceeds for 20 min, the supply of reaction gas is stopped, and protective gas is continued to purge the reaction chamber. At the same time, the residual reaction gas and by-products in the reaction chamber are discharged using a vacuum system; after the reaction chamber cools to room temperature, the sample is taken out, and a substrate with a photothermal absorption layer 3 deposited on the surface of the first hybrid hydrogel layer 2 is obtained; during the deposition process, when the transparent substrate is glass, the substrate temperature is controlled at 60-120℃; when the transparent substrate is PC material, the substrate temperature is controlled at 40-80℃; when the transparent substrate is PMMA, the substrate temperature is controlled at 40-60℃ during the deposition process.

[0051] The photothermal absorption layer nanomaterials include any one or more of the following: gold nanoparticles, copper sulfide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, nickel nanoparticles, Cu7S4 nanoparticles, CuCoMnOx, cesium tungsten oxide nanoparticles, indium tin oxide nanoparticles, CuS nanoparticles, SiC nanoparticles, PbS nanoparticles, GaAs nanoparticles, GaN nanoparticles, polythiophene organic polymers, polypyrrole organic polymers, polyaniline organic polymers, or polyacetylene organic polymers.

[0052] The reacting gases include any one or more of the following: methane, ethylene, acetylene, silane, borane, ammonia, nitrogen, argon, hydrogen, or oxygen;

[0053] When preparing a photothermal absorption layer using a solution coating method, the specific steps include:

[0054] Photothermal absorbing nanomaterials are added to a solvent to prepare a photothermal dispersion with a mass concentration of 0.1–5 mg / mL. Then, a dispersant or binder is added to stabilize the photothermal particles and enhance their bonding force with the hydrogel coating. The mixture is magnetically stirred at room temperature for 30–60 min and then ultrasonically dispersed for 20–40 min to obtain a uniform and stable photothermal coating solution.

[0055] A transparent substrate with a first hybrid hydrogel coating is fixed on a horizontal coating stage. Gas is introduced to blow away surface dust. Then, the photothermal coating liquid is uniformly coated onto the surface of the first hybrid hydrogel coating by spin coating, blade coating, spray coating or dip coating. After coating, the sample is placed in a forced-air drying oven for low-temperature drying treatment. For glass substrates, drying is carried out at 60–100℃ for 1–2 hours. For PC or PMMA substrates, the drying temperature is controlled at 40–70℃.

[0056] After cooling to room temperature, rinse the sample surface with deionized water or ethanol, and then dry it again at 40–60°C for 30–60 min to obtain a substrate with a photothermal absorption layer 3 coated on the surface of the first hybrid hydrogel layer 2.

[0057] The photothermal absorbing nanomaterial is one or more of the following: cesium tungsten oxide nanoparticles, copper sulfide nanoparticles, CuS nanoparticles, indium tin oxide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, polypyrrole, and polyaniline materials.

[0058] S3: Preparation of photothermal composite transparent substrate

[0059] According to the method in step S1, another hybrid hydrogel coating, namely the second hybrid hydrogel coating 4, is prepared on the surface of the photothermal absorption layer. The second transparent substrate 5 is then laid on the hybrid hydrogel coating and heated and pressed to obtain a photothermal composite transparent substrate. The second transparent substrate 5 is glass, polycarbonate (PC) material, or polymethyl methacrylate (PMMA) material. When the second transparent substrate 5 is glass, the heating and pressing temperature is 60-120℃. When the second transparent substrate 5 is PC material, the heating and pressing temperature is 40-80℃. When the second transparent substrate 5 is PMMA material, the heating and pressing temperature is 40-60℃.

[0060] In addition, the present invention also provides a photothermal composite transparent substrate prepared according to the above-described method for preparing photothermal composite transparent substrate.

[0061] Preferably, according to claim 3, the photothermal composite transparent substrate is characterized in that, from bottom to top, the photothermal composite transparent substrate comprises: a first transparent substrate 1, a first hybrid hydrogel coating 2, a photothermal absorption coating 3, a second hybrid hydrogel coating 4, and a second transparent substrate 5. The first hybrid hydrogel coating 2 and the second hybrid hydrogel coating 4 are respectively bonded to opposite sides of the photothermal absorption coating 3 to form a double-sided clamping structure for the photothermal absorption coating 3. The double-sided clamping structure and the photothermal absorption coating 3 together constitute a photothermal-moisture-absorbing synergistic anti-fogging unit, which provides support, bonding, moisture absorption and humidity regulation, and auxiliary transparency functions, and is beneficial to improving the interlayer bonding stability, heat transfer capacity, and anti-fogging and defogging performance of the photothermal absorption coating 3.

[0062] The photothermal absorption coating 3 is used to absorb ultraviolet, near-infrared and visible light in the solar spectrum and convert them into heat energy; the first transparent substrate 1 and the second transparent substrate 5 are used to provide the mechanical strength, transparency and safety required for the overall structure.

[0063] Preferably, the transmittance of the photothermal composite transparent substrate surface in the visible light wavelength range is higher than 65%.

[0064] Preferably, the effective solar thermal absorption spectrum range of the photothermal absorption coating 3 is 0.25-2.5 μm, and the absorption rate is not less than 80% within this band.

[0065] Example 1

[0066] A piece of float glass was washed and set aside. Then, a first hybrid hydrogel coating 2 was formed on the surface of the float glass using a solution gelation method. The precursor used was a polyvinyl alcohol / polyN-isopropylacrylamide system, and the solvent used was water. The specific steps were as follows: the precursor was uniformly mixed under liquid phase conditions and reacted at 30°C and pH 3.0 for 30 min to form a transparent sol through hydrolysis and condensation reactions; the obtained sol was aged at 30°C for 1 h to form a three-dimensional network structure gel; then dried at 60°C for 2 h, and finally heat-treated at 90°C for 2.5 h to cure, thus obtaining the first hybrid hydrogel coating 2 on the surface of the float glass.

[0067] Subsequently, tungsten cesium oxide nanoparticles were deposited on the surface of the first hybrid hydrogel layer 2 using low-temperature chemical vapor deposition to form a photothermal absorption layer 3. The specific steps were as follows: the float tempered glass carrying the first hybrid hydrogel layer 2 was placed on a heating device within the deposition chamber; the deposition chamber was closed, and the gas was evacuated and purged with nitrogen for 10 min; the pressure in the deposition chamber was controlled at 800 Pa, and the substrate temperature was controlled at 90℃ and preheated for 10 min; then, a reaction gas containing the tungsten cesium oxide precursor was introduced, and deposition was carried out for 20 min under nitrogen at 150 mL / min and argon at 50 mL / min, allowing the reaction particles to be uniformly deposited on the surface of the first hybrid hydrogel layer 2; after deposition, nitrogen purging was continued for 5 min, while the residual reaction gas and byproducts in the reaction chamber were removed using a vacuum system; after cooling to room temperature, the sample was removed, yielding a tungsten cesium oxide photothermal absorption layer with a thickness of approximately 80 nm.

[0068] Then, a second hybrid hydrogel coating 4 is formed on the surface of the photothermal absorption layer 3 using the same method as described above; finally, another piece of float tempered glass is laid on the surface of the second hybrid hydrogel layer 4 and heated and pressed at 120°C to obtain a photothermal composite transparent substrate.

[0069] To verify the performance of the samples in this embodiment, electrothermal laminated glass (including resistance wire), ordinary glass, and the photothermal composite transparent substrate prepared in this embodiment (without resistance wire) were respectively placed in a solar simulator, a spectrometer, and an anti-fog testing device for testing. The test results showed that under simulated solar radiation intensity and a room temperature of 26°C, the average temperature rise of ordinary glass was 3°C, while the average temperature rise of the photothermal composite transparent substrate prepared in this embodiment reached approximately 50°C, which is not significantly different from the heating effect of the electrothermal laminated glass. Figure 2 Transmittance testing showed that, within the visible light wavelength range of 380–780 nm, the average visible light transmittance of the photothermal composite transparent substrate prepared in this embodiment was approximately 70%, generally higher than 65%, indicating that the structure maintains good transparency while achieving photothermal heating function. Figure 3 The electrothermal laminated glass was obtained through purchase and is from Fanchen Technology Co., Ltd.

[0070] To further investigate the photothermal conversion mechanism of the photothermal composite transparent substrate of this invention, the absorption characteristics of the sample in the main energy range (0.25-2.5 μm) of the full solar spectrum were characterized by a spectrometer. Figure 4 The figure shows a comparison of the spectral absorption curves of photothermal composite transparent substrate and ordinary float tempered glass. As can be seen from the figure, the spectral absorption rate of ordinary glass is extremely low in the entire 0.25-2.5 μm band; while the absorption rate of photothermal composite transparent substrate in this band is not less than 80%.

[0071] Anti-fog glass coated with a single photothermal coating (hereinafter referred to as: photothermal coated glass) was prepared according to the method disclosed in patent CN202311631928.5. This glass, along with the photothermal composite transparent substrate prepared in this embodiment, was simultaneously subjected to electron microscopy scanning. Figure 5 It is evident that there are significant differences in the surface microstructure between the photothermal coated glass alone and the photothermal composite transparent substrate after treatment. Compared to the photothermal coated glass alone, the surface of the photothermal composite transparent substrate is more uniform, with a significant reduction in surface bright spots and localized unevenness. This indicates that the introduction of hydrogel layers on both sides of the intermediate photothermal layer effectively encapsulates, protects, and regulates the structure of the photothermal layer, thereby improving the surface structure of the sample.

[0072] The above-mentioned photothermal coated glass and the photothermal composite transparent substrate prepared in this embodiment were compared in anti-fogging test and heating test. The anti-fogging test results showed that the photothermal coated glass alone entered a significant fogging state earlier in the condensation environment, while the photothermal composite transparent substrate could maintain good visibility for a longer period of time. The time when significant fogging appeared was relatively delayed, and the transparency recovery speed of the photothermal composite transparent substrate was significantly faster in the subsequent defogging stage. Figure 6 The results indicate that the photothermal coated glass alone mainly relies on photothermal heating to achieve defogging, while the photothermal composite transparent substrate, while retaining its photothermal response capability, also exhibits a more significant effect in delaying fogging, suggesting a synergistic anti-fogging and defogging effect between the hydrogel layers on both sides and the middle photothermal layer. Both can achieve anti-fogging effects, but the photothermal composite transparent substrate is superior.

[0073] As can be seen from the temperature rise test results ( Figure 7 Both the photothermal coated glass and the photothermal composite transparent substrate exhibited good photothermal response capabilities. Specifically, the photothermal composite transparent substrate showed a faster temperature rise trend in the initial and middle stages of heating, while the photothermal coated glass alone reached a slightly higher final temperature in the later stages. These results indicate that the introduction of hydrogel layers on both sides did not weaken the photothermal conversion function of the intermediate photothermal layer; rather, it enabled the sample to maintain an effective photothermal response while exhibiting a temperature rise behavior different from that of the photothermal coated glass alone.

[0074] In summary, standalone photothermal coated glass primarily exhibits a single photothermal heating function. However, the photothermal composite transparent substrate, due to the presence of hydrogel layers on both sides of the photothermal layer, not only maintains excellent photothermal response capabilities but also demonstrates different technical effects in terms of surface structural stability and anti-fogging behavior compared to standalone photothermal coated glass. This represents a transformation from a single photothermal function to a composite functional structure with synergistic photothermal response and anti-fogging effects. Specifically, the photothermal absorption coating absorbs ultraviolet, visible, and near-infrared energy from the solar spectrum and converts it into heat energy; the hybrid hydrogel coatings located on its upper and lower sides simultaneously perform multiple functions, including interfacial bonding, flexible support, moisture absorption and regulation, heat transfer, photothermal layer protection, and auxiliary transparency.

[0075] In summary, the photothermal composite transparent substrate provided by this invention achieves significant photothermal heating and anti-fogging / defogging effects while maintaining high transparency by setting a hybrid hydrogel coating and a photothermal absorption coating between two transparent substrate layers. The transparent substrate can be glass, PC, or PMMA, making it suitable not only for automotive glass and transparent architectural components but also for anti-fogging and defogging needs of automotive headlights, taillights, and other transparent lighting covers. Specifically, the surface of the composite transparent substrate with the photothermal coating has a transmittance of over 65% in the visible light range, and the photothermal absorption layer achieves a high absorption rate within the 0.25-2.5 μm solar spectrum range, with the highest absorption rate exceeding 80%. The results of Example 1 show that under simulated solar intensity and a room temperature of 26°C, the average temperature rise of ordinary glass is only 3°C, while the average temperature rise of the photothermal composite transparent substrate of this invention can reach approximately 50°C, indicating that this invention has strong self-heating capability and excellent anti-fogging performance. Compared to ordinary transparent substrates, the photothermal composite transparent substrate prepared by this invention has excellent anti-fogging, moisture absorption, and wear resistance. Compared to ordinary electrothermal laminated glass or electrically heated vehicle headlight defogging structures, it has independent anti-fogging and defogging performance, consumes less energy from the vehicle itself, and has energy-saving and environmentally friendly effects. Compared to single photothermal coating glass, it has better anti-fogging effect and faster defogging speed. At the same time, the double-sided hybrid hydrogel layer can clamp and encapsulate the photothermal absorption coating, which is beneficial to improving interface stability and long-term reliability, and has good anti-fogging ability and potential anti-frost and anti-icing effects in low temperature and high humidity environments.

Claims

1. A method for preparing a photothermal composite transparent substrate, characterized in that, Includes the following steps: S1: Preparation of the first hybrid hydrogel coating The first transparent substrate (1) is washed and set aside. A compound containing highly chemically active components is used as a precursor, dissolved in a solvent, and subjected to hydrolysis and condensation reactions at 20-50℃ and pH 2.0-6.0 to form a stable transparent sol system in the solution. The first transparent substrate (1) is immersed in the above sol by impregnation. After aging, the resulting sol polymerizes between the particles to form a three-dimensional network structure gel. After drying, the above structure gel is heat-treated and heat-cured for 2-3 hours to obtain a first hybrid hydrogel coating (2) on the surface of the first transparent substrate (1). The first transparent substrate (1) is glass, polycarbonate (PC) material or polymethyl methacrylate (PMMA) material; The precursor is any one or more of the following: polyvinyl alcohol / polyN-isopropylacrylamide composite hydrogel, tannic acid / silk fibroin photothermal composite hydrogel, thermochromic polyvinyl butyral film, black phosphorus hybrid hydrogel, organosilicon sol, acrylic modified polyurethane, acrylic resin, polyurethane, water glass or silica sol. When the first transparent substrate (1) is glass, the solvent is any one or more of water, ethanol, acetone, n-propanol, isopropanol, and ethylene glycol; the thermosetting temperature is 60℃-110℃. When the first transparent substrate (1) is a polycarbonate (PC) material or a polymethyl methacrylate (PMMA) material, the solvent is any one or more of water, ethanol or isopropanol; the thermosetting temperature is 60℃-90℃; S2: Preparation of the photothermal absorption layer The photothermal absorption layer is prepared by low-temperature deposition or solution coating. When the photothermal absorption layer is prepared by low-temperature deposition, the specific steps include: Low-temperature deposition: Select photothermal absorption layer nanomaterials for deposition, and select appropriate reaction gases according to different nanomaterials; place the transparent substrate with the first hybrid hydrogel coating (2) obtained in step S1 into the reaction container, evacuate the gas and introduce protective gas for pre-purging, and introduce the selected reaction gas; during the deposition process, the gas pressure is kept in the low pressure range. After the deposition reaction has been carried out for 20 min, the supply of reaction gas is stopped, and protective gas is continued to be introduced to purge the reaction chamber. At the same time, the residual reaction gas and by-products in the reaction chamber are discharged using the vacuum system; after the reaction chamber is cooled to room temperature, the sample is taken out to obtain a substrate with a photothermal absorption layer (3) deposited on the surface of the first hybrid hydrogel layer (2); during the deposition process, when the transparent substrate is glass, the substrate temperature is controlled at 60-120℃; when the transparent substrate is PC material, the substrate temperature is controlled at 40-80℃; when the transparent substrate is PMMA, the substrate temperature is controlled at 40-60℃ during the deposition process. The photothermal absorption layer nanomaterials include any one or more of the following: gold nanoparticles, copper sulfide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, nickel nanoparticles, Cu7S4 nanoparticles, CuCoMnOx, cesium tungsten oxide nanoparticles, indium tin oxide nanoparticles, CuS nanoparticles, SiC nanoparticles, PbS nanoparticles, GaAs nanoparticles, GaN nanoparticles, polythiophene organic polymers, polypyrrole organic polymers, polyaniline organic polymers, or polyacetylene organic polymers. The reacting gases include any one or more of the following: methane, ethylene, acetylene, silane, borane, ammonia, nitrogen, argon, hydrogen, or oxygen; When preparing a photothermal absorption layer using a solution coating method, the specific steps include: Photothermal absorbing nanomaterials are added to a solvent to prepare a photothermal dispersion with a mass concentration of 0.1–5 mg / mL. Then, a dispersant or binder is added to stabilize the photothermal particles and enhance their bonding force with the hydrogel coating. The mixture is magnetically stirred at room temperature for 30–60 min and then ultrasonically dispersed for 20–40 min to obtain a uniform and stable photothermal coating solution. A transparent substrate with a first hybrid hydrogel coating is fixed on a horizontal coating stage. Gas is introduced to blow away surface dust. Then, the photothermal coating liquid is uniformly coated onto the surface of the first hybrid hydrogel coating by spin coating, blade coating, spray coating or dip coating. After coating, the sample is placed in a forced-air drying oven for low-temperature drying treatment. For glass substrates, drying is carried out at 60–100℃ for 1–2 hours. For PC or PMMA substrates, the drying temperature is controlled at 40–70℃. After cooling to room temperature, rinse the sample surface with deionized water or ethanol, and then dry it again at 40–60°C for 30–60 min to obtain a substrate with a photothermal absorption layer (3) coated on the surface of the first hybrid hydrogel layer (2). The photothermal absorbing nanomaterial is one or more of the following: cesium tungsten oxide nanoparticles, copper sulfide nanoparticles, CuS nanoparticles, indium tin oxide nanoparticles, polydopamine-titanium dioxide hybrid nanoparticles, polypyrrole, and polyaniline materials. S3: Preparation of photothermal composite transparent substrate According to the method in step S1, another hybrid hydrogel coating is prepared on the surface of the photothermal absorption layer, namely the second hybrid hydrogel coating (4). The second transparent substrate (5) is laid on the hybrid hydrogel coating and heated and pressed to obtain the photothermal composite transparent substrate. The second transparent substrate (5) is glass, polycarbonate (PC) material or polymethyl methacrylate (PMMA) material. When the second transparent substrate (5) is glass, the heating and pressing temperature is 60-120℃. When the second transparent substrate (5) is PC material, the heating and pressing temperature is 40-80℃. When the second transparent substrate (5) is PMMA material, the heating and pressing temperature is 40-60℃.

2. The method for preparing a photothermal composite transparent substrate according to claim 1, characterized in that, The glass materials of the first transparent substrate (1) and the second transparent substrate (5) are float glass or tempered glass.

3. The photothermal composite transparent substrate prepared by the method described in claim 1.

4. The photothermal composite transparent substrate according to claim 3, characterized in that, The photothermal composite transparent substrate comprises, from bottom to top: a first transparent substrate (1), a first hybrid hydrogel coating (2), a photothermal absorption coating (3), a second hybrid hydrogel coating (4), and a second transparent substrate (5). The first hybrid hydrogel coating (2) and the second hybrid hydrogel coating (4) are respectively bonded to opposite sides of the photothermal absorption coating (3) to form a double-sided clamping structure for the photothermal absorption coating (3). The double-sided clamping structure and the photothermal absorption coating (3) together constitute a photothermal-moisture-absorbing synergistic anti-fog unit, which provides support, bonding, moisture absorption and humidity regulation and auxiliary transparency functions, and is beneficial to improving the interlayer bonding stability, heat transfer capacity and anti-fog and defogging performance of the photothermal absorption coating (3). The photothermal absorption coating (3) is used to absorb ultraviolet, near-infrared and visible light in the solar spectrum and convert them into heat energy; the first transparent substrate (1) and the second transparent substrate (5) are used to provide the mechanical strength, transparency and safety required for the overall structure.

5. The photothermal composite transparent substrate according to claim 4, characterized in that, The transmittance of the surface of the photothermal composite transparent substrate is higher than 65% in the visible light wavelength range.

6. The photothermal composite transparent substrate according to claim 4, characterized in that, The effective solar thermal absorption spectrum of the photothermal absorption coating (3) is 0.25-2.5 μm, and the absorption rate is not less than 80% in this band.

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