An anti-fog coating, its preparation method and application

Abstract

This invention belongs to the field of coating materials, specifically including an anti-fog coating, its preparation method, and its application. The raw materials for preparing the anti-fog coating specifically include the following components: photothermal nanoparticles, polyvinyl alcohol, phytic acid solution, glutaraldehyde solution, and deionized water in a ratio of 0.6 kg: 15 kg: 20 L: 10 L: 150 L. The photothermal nanoparticles are added to deionized water and ultrasonically dispersed to obtain a uniform nanoparticle suspension. Polyvinyl alcohol is added to this suspension, and the system is placed in a high-temperature water bath and magnetically stirred until completely dissolved. Then, an appropriate amount of phytic acid solution is added, and ultrasonically dispersed until the phytic acid is fully dissolved. Next, glutaraldehyde solution is added to the mixture, and magnetically stirred to allow the glutaraldehyde to fully react with the system components, obtaining a stable and dispersed coating. Finally, the coating is uniformly applied to the surface of a glass substrate and allowed to air dry naturally in a ventilated area. The resulting coating effectively inhibits the formation of fog droplets and accelerates the dissipation of existing fog droplets, while maintaining good light transmittance.

Description

Technical Field

[0001] This invention belongs to the field of coating materials, specifically including an anti-fog coating, its preparation method, and its application. Background Technology

[0002] Transparent glass materials are widely used in various aspects of daily life, transportation, and medicine, making production and daily life more convenient. However, when the humidity and temperature of the environment in which glass materials are located change, fogging occurs on their surface, seriously affecting their usability and aesthetics. For example, when there is a large temperature difference between indoors and outdoors, a layer of fog immediately forms on the surface of glasses when entering from outdoors, which greatly affects people's experience; fogged windshields and rearview mirrors can interfere with people's vision, thus posing a safety hazard; fogging on the surface of doctors' goggles, protective masks, and surgical endoscopes can affect doctors' operations and may even cause medical accidents. Therefore, research in the field of anti-fog technology has attracted increasing attention.

[0003] Traditional technologies fall into two categories: one involves altering the wettability of the glass surface, i.e., preparing superhydrophilic or superhydrophobic coatings; the other involves altering the environment, i.e., electrically heated anti-fogging methods. In other words, current glass anti-fogging strategies primarily rely on surface wettability control or environmental regulation.

[0004] Regarding altering the wettability of glass surfaces, existing anti-fogging technologies utilize anti-fogging materials with superwetting properties, namely superhydrophilic and superhydrophobic surfaces, to achieve anti-fogging by changing the morphology of water droplets on the material surface. Due to its exceptional wettability, it is widely used in many fields, such as oil-water separation, self-cleaning, and anti-icing. On superhydrophilic surfaces, fog forms a continuous, very thin water film, initially helping to maintain surface transparency. However, due to gravity, evaporation, and contaminants, this water film becomes uneven, leading to decreased transparency. Furthermore, these surfaces are highly susceptible to contamination by organic solvents, and their high surface energy severely limits the material's durability. Superhydrophobic surfaces, due to their low surface energy and effective self-cleaning properties, offer more durable anti-fogging capabilities. They utilize hydrophobicity to expel condensed water droplets before fog impairs transparency. However, exposure to low temperatures or high humidity environments increases the adhesion of water droplets to superhydrophobic surfaces, thus weakening their anti-fogging performance. Superhydrophilic coatings maintain transparency by spreading water droplets into a water film, while superhydrophobic coatings prevent fogging by having water droplets roll off. However, both methods suffer from poor durability under low stress conditions and complex fabrication processes, limiting their large-scale application. Active methods, such as substrate heating and forced airflow, can ensure optical clarity but are energy-intensive and risk structural damage. Therefore, combining these strategies offers a promising approach for developing energy-efficient passive photothermal antifogging coatings. Photothermal materials can self-heat under sunlight, and when used as coatings, they can significantly improve the antifogging performance of glass. Due to their advantages in sustainability and energy efficiency, this approach is becoming a promising direction in materials and energy research.

[0005] In modern optical applications, such as eyeglasses, vehicle windshields, camera lenses, and various displays, high transparency and anti-fog performance are two crucial technical indicators. Traditional anti-fog technologies often rely on surface coatings to improve the surface's hydrophilicity, thereby preventing water vapor from condensing into fog on the surface. However, existing coating technologies have failed to achieve both high transparency and anti-fog performance. Summary of the Invention

[0006] The purpose of this invention is to provide a solar thermal anti-fog coating to solve the problem of low transparency in existing anti-fog coatings.

[0007] To solve the above-mentioned technical problems, the present invention adopts the following technical solution: This invention proposes a solar thermal anti-fog coating, which is made of solar thermal nanoparticles, polyvinyl alcohol, phytic acid solution, glutaraldehyde solution, and deionized water in a ratio of 0.6 kg: 15 kg: 20 L: 10 L: 150 L. The photothermal nanoparticles include at least one of metal nanoparticles, metal oxide nanoparticles, carbon-based nanoparticles, and semiconductor nanoparticles. Preferably, the concentrations of the phytic acid solution and the glutaraldehyde solution are 3 wt% or 8 wt%. A method for preparing a solar thermal anti-fogging coating includes the following steps: Photothermal nanoparticles were added to deionized water and ultrasonically dispersed to obtain a nanoparticle suspension. Polyvinyl alcohol was added to the nanoparticle suspension and dissolved by stirring in a water bath to obtain mixed solution A; Phytic acid was added to mixture A and dispersed by ultrasonication to obtain mixture B. Glutaraldehyde was added to mixture B, and the mixture was stirred to react, thus obtaining the coating. The coating is applied to the surface of the glass substrate and placed in a ventilated place to air dry naturally. After the coating is formed, a solar-heat-based anti-fog coating is obtained.

[0008] Preferably, the ultrasonic dispersion power is 500~1500 W and the ultrasonic dispersion time is 20 min.

[0009] Preferably, the conditions for stirring and dissolving in the water bath are 55 °C, stirring for 30-60 min, and stirring speed of 120-400 rpm.

[0010] Preferably, the reaction time for stirring is 10 minutes, and the stirring speed is 120~350 rpm.

[0011] Preferably, the natural air drying is carried out within a range of 37 ℃ and 30% relative humidity.

[0012] The coating is applied to the anti-fog substrate by applying 33 μL of coating per square centimeter of glass substrate surface, which forms an anti-fog coating after drying.

[0013] The principle of this invention is as follows: The matrix of the photothermal anti-fog coating of this invention is polyvinyl alcohol, characterized in that: compared with similar alcohols such as ethylene glycol, glycerol, methanol, and ethanol, polyvinyl alcohol has excellent film-forming properties and water solubility, can uniformly carry photothermal nanoparticles and has strong adhesion to the substrate; after glutaraldehyde crosslinking treatment, the flexibility of the coating and its adhesion to the substrate surface are further improved, making it less prone to peeling and cracking, and it can maintain stable photothermal anti-fog performance even after long-term use. In contrast, similar alcohols have defects such as poor film formation, easy brittleness and peeling, inability to uniformly disperse photothermal nanoparticles, affected light transmittance or easy volatilization under light, which leads to coating failure, and are therefore not suitable for the photothermal anti-fog coating of this invention.

[0014] Fog is generated when water vapor condenses into tiny droplets on a low-temperature surface. Active anti-fog technology based on photothermal conversion offers a new direction for solving this problem. However, the development of this technology faces a core contradiction: most traditional photothermal materials, such as carbon materials and metal nanoparticles, exhibit full-spectrum absorption of sunlight. While efficiently generating heat energy, they severely impede visible light transmission, directly contradicting the high transparency required for anti-fog applications. This invention successfully overcomes this contradiction through component design and structural control. The photothermal nanoparticles in the coating are optimized and finely dispersed, selectively absorbing near-infrared light in the solar spectrum and efficiently converting it into heat energy, while maintaining high visible light transmittance to the maximum extent. This localized heating effect keeps the substrate surface temperature stable above the dew point, thereby fundamentally inhibiting water vapor condensation and achieving highly efficient anti-fog.

[0015] During the preparation process, the order in which the components are added has a crucial impact on the structure and properties of the final coating. The correlation mechanism is as follows: First, dispersing the photothermal nanoparticles in deionized water is to allow them to fully deagglomerate in the solvent and form a stable suspension. If polymers or other components are added first, the nanoparticles are easily encapsulated or isolated, making it difficult to disperse them evenly later, resulting in decreased photothermal performance and uneven appearance of the coating.

[0016] The second step involves adding polyvinyl alcohol (PVA) and stirring to dissolve it in a water bath. PVA, acting as a film-forming agent and dispersion medium, can form a preliminary coating and steric hindrance on the surface of the dispersed nanoparticles, further enhancing the stability of the system, preventing particle sedimentation and re-aggregation, and providing a uniform matrix for subsequent crosslinking reactions.

[0017] The third step involves adding phytic acid solution. Phytic acid molecules contain multiple phosphate groups, which can form hydrogen bonds with the hydroxyl groups on the PVA chains and participate in the initial cross-linking, playing a role in "pre-cross-linking" and enhancing the coating network structure. This step lays the foundation for the subsequent efficient cross-linking of glutaraldehyde.

[0018] Finally, a glutaraldehyde solution is added. Glutaraldehyde, acting as a crosslinking agent, undergoes acetalization and other crosslinking reactions with the hydroxyl groups of PVA and the phosphate groups of phytic acid, forming a dense three-dimensional network structure. This structure significantly improves the coating's mechanical strength, adhesion, and water resistance, ensuring its long-term stability and anti-fogging effect in humid environments.

[0019] Compared with the prior art, the present invention has the following beneficial effects: (1) This invention provides a solar thermal anti-fogging coating, which is made of solar thermal nanoparticles, polyvinyl alcohol, phytic acid solution, glutaraldehyde solution, and deionized water in a ratio of 0.6 kg: 15 kg: 20 L: 10 L: 150 L. The coating is anti-fogging and has high transparency.

[0020] (2) The solar thermal anti-fog coating prepared by the present invention has excellent spectral selectivity, strong absorption in the near-infrared band and good light transmittance in the visible band, and can efficiently match the solar spectrum.

[0021] (3) The solar thermal anti-fog coating prepared by the present invention is not easily contaminated by organic solvents, has durability, and will not increase the adhesion of water droplets on the superhydrophobic surface when exposed to low temperature or high humidity environment, and will not weaken its anti-fog performance.

[0022] (4) The photothermal anti-fog coating prepared by this invention has excellent photothermal conversion efficiency and good thermal stability. It can still stably perform its anti-fog function in high humidity environments, effectively inhibiting the formation of fog droplets and accelerating the dissipation of existing fog droplets, while maintaining good light transmittance. It is suitable for anti-fog application needs in actual scenarios. The preparation process is simple, the solvent is non-toxic deionized water, no complex instruments or deep treatment are required, the operation is easy to standardize, and it has high industrial promotion value. In the field of photothermal anti-fog, the coating of this invention has a lower economic cost and a simpler manufacturing process compared to other coatings, and the solvent is water. Attached Figure Description

[0023] Figure 1 The optical and spectral radiation diagrams of the photothermal antifog coating of the present invention are shown below; (a) shows the absorption, reflection and transmission spectra of the coating, with wavelength on the horizontal axis and A, R, T on the vertical axis, representing absorption, reflection and transmission; (b) shows the spectral radiation distribution of the coating's absorption, reflection and transmission, with wavelength on the horizontal axis and radiation distribution on the vertical axis; Absorption represents absorption, Reflection represents reflection and Transmission represents transmission.

[0024] Figure 2 The following is a comparison of the photothermal performance of the photothermal anti-fog coated glass and bare glass using the present invention; (a) is a curve showing the temperature change of the coating and bare glass over time; (b) is an infrared thermal image of the coating and bare glass at 0 min and 10 min; sample represents the coating and glass represents the bare glass.

[0025] Figure 3This is a comparison of the anti-fog performance of glass with the photothermal anti-fog coating of this invention and bare glass. After simulated illumination with a xenon lamp, the uncoated transparent glass was shrouded in fog and had poor transmittance; the coated glass had good transmittance because the photothermal effect temperature of the cesium tungstate coating was high, causing water vapor to evaporate. (a) is a schematic diagram of the anti-fog testing device; (b) shows the state of the bare glass at 0 s on the left and the state of the coated glass at 0 s on the right; (c) shows the state of the bare glass at 60 s on the left and the state of the coated glass at 60 s on the right; (d) shows the state of the bare glass at 120 s on the left and the state of the coated glass at 120 s on the right; the letters sdfmu are visible in the uncoated transparent glass after simulated illumination with a xenon lamp, where the coated glass is shrouded in fog and has poor transmittance, while the coated glass has good transmittance because the photothermal effect temperature of the cesium tungstate coating is high, causing water vapor to evaporate. Detailed Implementation

[0026] The present invention will be further described in detail below with reference to embodiments, but the implementation of the present invention is not limited thereto. Unless otherwise specified, the technical means used in the following embodiments are conventional means well known to those skilled in the art; the experimental methods used are all conventional methods; and the materials, reagents, etc. used are all commercially available.

[0027] PVA represents polyvinyl alcohol, sourced from Shanghai Aladdin Biochemical Technology Co., Ltd., product number 9002-89-5; PA represents phytic acid, chemical formula C6H. 18 O 24 P6, Shanghai Titan Technology Co., Ltd., CAS No. 83-86-3, 70wt% aqueous solution; GA represents glutaraldehyde, from Shanghai Aladdin Biochemical Technology Co., Ltd., CAS No. 111-30-8, analytical grade, 50wt% aqueous solution; Cesium tungstate nanoparticles are abbreviated as Cs. 0.33 WO3, from Shanghai Yingcheng New Materials Co., Ltd., China, and the Cs used... 0.33 The particle size of WO3 nanoparticles is 30 nanometers.

[0028] Example 1 A method for preparing a solar-thermal anti-fogging coating includes the following steps: S1. Preparation of cesium tungstate nanoparticle suspension: Weigh 0.06 g of Cs 0.33 Add WO3 to 15 mL of deionized water, place the system in an ultrasonic disperser, and sonicate at 1500 W for 20 min to disperse Cs. 0.33 WO3 nanoparticles were uniformly dispersed to prepare Cs 0.33 WO3 nanoparticle suspension.

[0029] S2, PVA-PA-Cs0.33 Preparation of WO3 mixture: Cs prepared from S1 0.33 1.5 g of PVA was added to a WO3 nanoparticle suspension, and the system was stirred at 400 rpm for 30 min in a 55℃ water bath until the PVA was completely dissolved. Then, 2 mL of 8wt% phytic acid solution was added to the system, and the mixture was ultrasonically dispersed again at 1500 W for 60 min to ensure the PA was fully dissolved and uniformly mixed with the system, thus preparing PVA-PA-Cs. 0.33 WO3 mixture.

[0030] S3, PVA-PA-Cs 0.33 Formulation and Coating of WO3 Dispersed Coatings: PVA-PA-Cs prepared by S2 0.33 Add 1 mL of 8wt% GA solution to the WO3 mixture and stir magnetically at 120 rpm for 10 min to allow GA to fully undergo a polycondensation reaction with the components in the system, forming stable PVA-PA-Cs with a certain viscosity. 0.33 WO3 dispersion coating; then, the dispersion is uniformly applied to the surface of a 3 cm × 3 cm × 0.1 cm glass substrate, with 33 μL of coating applied per square centimeter of glass substrate surface, and air-dried naturally at 37°C and 30% relative humidity to obtain a composite coating that can utilize solar energy for anti-fogging.

[0031] Example 2 A method for preparing a solar-thermal anti-fogging coating includes the following steps: S1. Preparation of cesium tungstate nanoparticle suspension: Weigh 0.06 g of Cs 0.33 Add WO3 to 15 mL of deionized water, place the system in an ultrasonic disperser and sonicate at 500 W for 20 min to allow Cs to disperse. 0.33 WO3 nanoparticles were uniformly dispersed to prepare Cs 0.33 WO3 nanoparticle suspension.

[0032] S2, PVA-PA-Cs 0.33 Preparation of WO3 mixture: Cs prepared from S1 0.33 1.5 g of PVA was added to a WO3 nanoparticle suspension, and the system was stirred at 120 rpm for 60 min in a 55℃ water bath until the PVA was completely dissolved. Then, 2 mL of 3wt% phytic acid solution was added to the system, and the mixture was ultrasonically dispersed again at 1500 W for 60 min to ensure the PA was fully dissolved and uniformly mixed with the system, thus preparing PVA-PA-Cs. 0.33 WO3 mixture.

[0033] S3, PVA-PA-Cs 0.33 Formulation and Coating of WO3 Dispersed Coatings: PVA-PA-Cs prepared by S2 0.33 Add 1 mL of 3wt% GA solution to the WO3 mixture and stir magnetically at 350 rpm for 10 min to allow GA to fully undergo a polycondensation reaction with the components in the system, forming stable PVA-PA-Cs with a certain viscosity. 0.33 WO3 dispersion coating; then, the dispersion is uniformly applied to the surface of a 3 cm × 3 cm × 0.1 cm glass substrate, with 33 μL of coating applied per square centimeter of glass substrate surface, and air-dried naturally at 37°C and 30% relative humidity to obtain a composite coating that can utilize solar energy for anti-fogging.

[0034] The coating of Example 1 was subjected to performance testing, as detailed below: Experiment 1: Optical and Spectral Radiation of the Coating An ultraviolet-visible-near-infrared spectrophotometer was used to test the absorption, reflection, and transmission spectra of the coating in the 300 nm–2500 nm wavelength range, obtaining optical response data of the coating in the visible and near-infrared bands, such as... Figure 1 As shown in Figure (a); simultaneously, standard AM 1.5G solar irradiance spectral data were retrieved, and the coating spectrum was superimposed and compared with the solar spectrum to analyze the coating's ability to match and utilize solar energy, such as... Figure 1 As shown in Figure (b), the prepared solar thermal anti-fog coating has excellent spectral selectivity, strong absorption in the near-infrared band and good light transmittance in the visible band, and can efficiently match the solar spectrum.

[0035] Experiment 2: Photothermal Performance Testing of Coated Glass and Bare Glass A xenon lamp source, simulating a standard solar intensity of 1000 W / m², was used to vertically irradiate a coated glass substrate, with a bare glass substrate as a control. Thermocouple probes were attached to the same positions on both the coated and bare glass surfaces, and temperature data was collected and recorded in real time from 0 to 20 minutes of irradiation. Figure 2 As shown in Figure (a). Maintaining the same illumination conditions, thermal images of both objects were captured using an infrared thermal imager at the initial state after 0 minutes of illumination and at the state after 10 minutes of illumination, as shown in Figure (a). Figure 2 As shown in Figure (b), the above tests clearly demonstrate that the surface temperature of the coating is significantly higher, which intuitively verifies its outstanding photothermal heating effect and provides sufficient heat energy for anti-fogging.

[0036] Experiment 3: Anti-fog performance test of coated glass and bare glass A high-humidity fog environment was created, with xenon lamps maintaining standard sunlight intensity. The coated substrate and the bare substrate were placed parallel to each other on the fog. After uniform fog droplets formed inside the chamber, the formation and dissipation of fog droplets on both surfaces were observed and recorded at 0 s, 60 s, and 120 s. Changes in light transmittance were captured by camera to determine the anti-fogging effect of the coating. Figure 3 As shown, the coating exhibits outstanding anti-fog performance in high-humidity environments, effectively suppressing droplet formation and accelerating the dissipation of existing droplets, while maintaining good light transmittance, thus meeting the anti-fog application requirements in real-world scenarios.

[0037] Comparative Example 1 A method for preparing a coating includes the following steps: S1. Preparation of cesium tungstate nanoparticle suspension: Weigh 0.05 g of Cs 0.33 Add WO3 to 10 mL of deionized water, place the system in an ultrasonic disperser and sonicate at 500 W for 5 min, compared to 30 min in Example 1; so that Cs 0.33 WO3 nanoparticles were initially dispersed to prepare 0.5 wt% Cs. 0.33 WO3 nanoparticle suspension.

[0038] S2, PVA-PA-Cs 0.33 Preparation of WO3 mixture: Cs prepared from S1 0.33 1.2 g of PVA was added to a WO3 nanoparticle suspension, and the system was magnetically stirred at 180 rpm for 45 min in a 45℃ water bath until the PVA was completely dissolved. Then, 1.5 mL of 5wt% phytic acid solution was added to the system, and the mixture was ultrasonically dispersed again for 30 min to ensure complete dissolution of PA and homogeneous mixing, thus preparing PVA-PA-Cs. 0.33 WO3 mixture.

[0039] S3, PVA-PA-Cs 0.33 Formulation and Coating of WO3 Dispersed Coatings: PVA-PA-Cs prepared by S2 0.33 Add 0.8 mL of 5 wt% GA solution to the WO3 mixture, and stir magnetically at 180 rpm for 5 min to allow GA to fully undergo a polycondensation reaction with the components in the system, forming stable PVA-PA-Cs with a certain viscosity. 0.33 WO3 dispersion coating; subsequently, the dispersion was uniformly applied to the surface of a 3 cm × 3 cm × 0.1 cm glass substrate and allowed to air dry naturally at 25°C and 50% relative humidity to obtain the coating.

[0040] Results and phenomena: Insufficient dispersion of nanoparticles and severe aggregation led to light scattering, resulting in a milky white and turbid coating with poor clarity and anti-fog effect.

[0041] Comparative Example 2 A method for preparing a coating includes the following steps: S1. Preparation of cesium tungstate nanoparticle suspension: Weigh 0.06 g of Cs 0.33 Add WO3 to 10 mL of deionized water, place the system in an ultrasonic disperser and sonicate at 500 W for 30 min to allow Cs to disperse. 0.33 WO3 nanoparticles were uniformly dispersed to prepare a 0.6 wt% uniform Cs content. 0.33 WO3 nanoparticle suspension.

[0042] S2, PVA-PA-Cs 0.33 Preparation of WO3 mixture: Cs prepared from S1 0.33 1.2 g of PVA was added to a WO3 nanoparticle suspension, and the system was magnetically stirred at 180 rpm for 45 min in a 45℃ water bath until the PVA was completely dissolved. Then, 1.5 mL of 5wt% phytic acid solution was added to the system, and the mixture was ultrasonically dispersed again for 30 min to ensure complete dissolution of PA and homogeneous mixing, thus preparing PVA-PA-Cs. 0.33 WO3 mixture.

[0043] S3, PVA-PA-Cs 0.33 Formulation and Coating of WO3 Dispersed Coatings: PVA-PA-Cs prepared by S2 0.33 In a WO3 mixture, 3.0 mL of 5wt% GA solution was added (compared to 1 mL in Example 1). After magnetic stirring at 180 rpm for approximately 2 minutes, the viscosity of the system increased sharply, losing its fluidity and forming a gel-like substance. An attempt was made to coat it onto a 3 cm × 3 cm × 0.1 cm glass substrate, but it could not be spread evenly. Subsequently, it was left to stand at 25 °C and 50% relative humidity, ultimately resulting in a severely cracked, curled, and brittle incomplete coating film.

[0044] Results and phenomena: Excessive crosslinking agent led to excessively high crosslinking density and brittle network fracture. The resulting coating material could not adhere to the glass substrate, appearing as cracked, curled fragments, and lacking any practical function.

[0045] Comparative Example 3 Based on Example 1, PVA was dissolved first and then photothermal nanoparticles were added, with the rest remaining unchanged.

[0046] Nanoparticles are difficult to disperse due to the high viscosity of PVA solution, resulting in severe agglomeration. The photothermal conversion efficiency of the coating decreases by more than 30%, and visible agglomerates are present on the surface.

[0047] Comparative Example 4 Based on Example 1, glutaraldehyde was added before phytic acid, while the rest remained unchanged.

[0048] This causes PVA to crosslink too quickly, leading to a sharp increase in system viscosity. This makes it difficult to disperse nanoparticles, resulting in poor coating flowability and an inability to achieve uniform coating. Ultimately, this results in an ineffective coating that is prone to cracking and peeling.

[0049] Comparative Example 5 Based on Example 1, the ultrasonic dispersion power was 480 W and the time was 10 min, with the rest remaining unchanged.

[0050] Insufficient dispersion of nanoparticles leads to microscopic defects in the coating, and the anti-fog response time is extended by more than double.

[0051] Comparative Example 6 Based on Example 1, the ultrasonic dispersion power was 500 W and the time was 9 min, with the rest remaining unchanged.

[0052] Insufficient dispersion of nanoparticles leads to microscopic defects in the coating, and the anti-fog response time is extended by more than double.

[0053] Therefore, the component addition order and process parameters determined in this invention are necessary conditions for achieving high-performance solar thermal anti-fog coatings, and any deviation will prevent the achievement of the expected technical effect.

[0054] Comparative Example 7 A gold nanoparticle (Au)-titanium dioxide (TiO2) composite coating was used as a comparative scheme. This coating, like the one in this invention, is a solar-driven photothermal anti-fog coating with the same core function, but its preparation cost is significantly higher, as detailed below: I. Coating Composition and Preparation Cost 1. Coating composition The core photothermal material is gold nanoparticles with a particle size of 4 nm, and electronic-grade TiO2 nanosheets with a particle size of 30 nm. The bonding matrix is ​​polyelectrolyte PDDA. It is a liquid matrix material that relies on physical deposition to form a thin film structure.

[0055] 2. Preparation cost Raw material cost: The core raw materials include precious metal gold nanoparticles, high-purity TiO2 and special polyelectrolytes. Due to the high price of precious metal raw materials and the need for special processes for preparation and purification, the overall cost of raw materials is significantly higher than that of this invention. The cost of precious metal raw materials alone is hundreds of times that of the core raw materials of this invention.

[0056] Equipment depreciation costs: It relies on a series of high-value precision equipment such as vacuum magnetron sputtering equipment, laser interferometric thickness gauges, plasma activation equipment, and inert gas protected annealing furnaces. The purchase cost of such equipment is high and the maintenance requirements are high. The depreciation cost per unit area of ​​coating is extremely high, far exceeding the equipment cost of conventional ultrasonic instruments and stirrers used in this invention.

[0057] Process and testing costs: The preparation process requires maintaining a high vacuum environment and high temperature annealing conditions, resulting in high energy consumption; and because the coating is a multi-layered composite structure, it needs to be screened for quality through high-magnification electron microscopy and spectral detection, which further increases the cost of the process and testing.

[0058] Overall cost: The comparative example has an overall cost of several hundred yuan per square meter, while the present invention has an overall cost of only a few cents per square meter, a cost difference of thousands of times.

[0059] II. Preparation Process Substrate pretreatment: Take a 3 cm × 3 cm × 0.1 cm glass substrate, ultrasonically clean it with acetone for 30 min to remove surface oil; then place it in an oxygen plasma device and activate it at 100 W power for 15 min to introduce hydroxyl groups to enhance adhesion; finally place it in a vacuum oven and dry it at 80 ℃ for 1 h.

[0060] Preparation of gold nanoparticles: Using chloroauric acid as raw material, the pH of the reaction system was adjusted to 7.5, and the reduction reaction was carried out at 80 °C for 2 h to prepare gold nanoparticles with a particle size of 4 nm. After centrifugation and purification, the nanoparticles were ultrasonically mixed with TiO2 nanosheets for 4 h to form a mixed dispersion.

[0061] Vacuum sputtering of TiO2 substrate: The pretreated substrate is placed in the vacuum sputtering chamber and evacuated to 10°C. -5 At Pa, argon gas was introduced, and TiO2 was used as the target material. Sputtering was performed at 150 W power for 3 min to form a 3 nm thick TiO2 film.

[0062] Gold nanolayer deposition: Replace the gold target, adjust the sputtering power to 80 W, control the deposition rate to 0.1 nm / s, and deposit for 4 min to form a 4 nm thick gold nanocluster layer. During the process, the thickness is monitored in real time using a laser interferometer to ensure that the error is <0.1 nm.

[0063] Sputtering the top TiO2: Replace the TiO2 target again and repeat the bottom sputtering process to deposit a 3 nm thick top TiO2 to form a "TiO2 / Au / TiO2" sandwich structure.

[0064] Annealing treatment: The deposited coating is placed in an inert gas protected furnace and annealed at 200 °C for 1 h to enhance the interlayer adhesion.

[0065] Detection and screening: The integrity of the interlayer interface was observed by SEM at 100,000x magnification, and the near-infrared absorption rate was verified by UV-vis-NIR spectroscopy to be ≥80%. Unqualified products were redeposited.

[0066] III. The steps added compared to the present invention are as follows: acetone ultrasonic cleaning and plasma activation of the substrate. The reduction preparation and centrifugal purification of gold nanoparticles, the three-layer alternating sputtering deposition under vacuum, the inert gas protection annealing at 200 °C, and the screening by high-magnification SEM and spectral detection.

[0067] IV. Solvent System The comparative example only uses acetone as a cleaning solvent in the substrate pretreatment stage to remove oil stains from the glass surface, and no liquid solvent is used in the subsequent deposition and annealing processes; the present invention uses deionized water as the only solvent, without volatile organic reagents, is environmentally friendly and does not require solvent recycling.

[0068] In summary, while this comparative example can achieve photothermal anti-fogging functionality, its reliance on precious metal raw materials, high-cost precision equipment, and complex processes results in a significantly higher preparation cost than this invention. Furthermore, its cumbersome process, high energy consumption, and difficulty in large-scale production highlight the core advantages of this invention: "low cost, easy scalability, and environmental friendliness." (The question of whether uniformity is affected by...)

[0069] Experiment 4 Pollutant Detection This invention indirectly reflects the anti-fouling ability through the characterization of coating surface properties: Surface roughness: AFM testing showed that the coating's arithmetic mean roughness (Ra) was only 0.73 nm and the root mean square roughness (Rq) was 1.16 nm, indicating an extremely smooth surface with a lack of physical sites for contaminant adhesion. Hydrophilicity control: The water contact angle (WCA) is 84.65°, <90°, maintaining weak hydrophilicity, which can reduce the adsorption of hydrophobic pollutants, such as oil, while avoiding the problem of dust adhesion caused by strong hydrophilicity. Surface chemical properties: FTIR confirmed that the coating has no additional strongly polar or hydrophobic functional groups, is chemically stable, and is not easily chemically adsorbed by environmental pollutants.

[0070] Test results: The coating, with its "ultra-smooth surface + weak hydrophilicity + stable chemical structure", possesses potential anti-pollution capabilities: it can reduce the physical adsorption and chemical binding of common pollutants such as dust and oil. Furthermore, during photothermal heating, the surface temperature rises to approximately 42.8 ℃, which may promote the desorption of a small amount of attached pollutants through a slight thermal effect, further enhancing its anti-pollution practicality.

[0071] Experiment 5 Durability Testing This invention comprehensively verifies the durability of the coating through four dimensions: mechanical integrity testing, thermal stability testing, repeated anti-fogging performance testing, and long-term hydrophilicity retention testing. The testing methods, core parameters, and conditions for each dimension are as follows: 1. Mechanical integrity test The test method uses natural drying film formation combined with vertical placement verification. The specific conditions are an ambient temperature of 25 ℃ and a relative humidity of 50%. The coated sample is left to stand for 72 h to observe whether the coating cracks, peels or falls off.

[0072] 2. Thermal stability test The TGA / DTG analysis method was used, and the test was carried out in a nitrogen atmosphere with a heating rate of 10 ℃ / min. The test temperature range covered 35 ℃ to 800 ℃. The weight loss of the coating in different temperature ranges was analyzed by thermogravimetric curve analysis to evaluate the thermal stability.

[0073] 3. Repeated anti-fog performance test The cyclic anti-fog test mode was adopted, and the test environment was a high humidity environment combined with solar radiation simulation. Each test lasted for 2 minutes, and the test was repeated 5 times in total. After each test, we observed whether the anti-fog effect of the coating was reduced and whether the light transmittance remained stable.

[0074] 4. Long-term hydrophilicity retention test The stability of hydrophilicity was assessed by periodically testing the water contact angle. The test interval was set at 7 days. Each test was conducted at room temperature, using 5 μL of deionized water as the test medium. Five different test points were selected for testing, and the average value was taken to compare the changes in water contact angle data at different time points.

[0075] The durability test results are as follows: Mechanical integrity results: The coating showed no cracking or peeling after natural drying, and no detachment or sagging during vertical placement testing, demonstrating good mechanical integrity and substrate adhesion.

[0076] Thermal stability results: 35~200 ℃: slight mass loss, due to residual solvent and water evaporation; 200~500 ℃: significant mass loss, attributed to PVA chain decomposition and PA bond breaking; above 500 ℃: weight loss rate slows down and stabilizes, with residual thermally stable inorganic substances and a small amount of carbonaceous residue, confirming good thermal stability at actual application temperatures.

[0077] Repeated anti-fog performance results: It can still remain completely transparent after multiple tests, with no fog formation, stable photothermal conversion efficiency, and repeatable anti-fog performance of the coating.

[0078] Results of long-term hydrophilicity retention: The coating has a water contact angle of 84.65°, which is less than 90°. It maintains long-term hydrophilicity, promotes uniform spread of condensate, and inhibits fogging.

[0079] Experiment 6 Low Temperature and High Temperature Performance Testing 1. High-temperature performance testing Test conditions: Simulating a strong summer sunlight environment, xenon lamp irradiance of 1000 W / m² 2 AM1.5G spectrum, lasting 1 hour; Testing indicators: coating high temperature resistance, structural stability, photothermal properties; Results: ① The highest surface temperature of the coating reached 42.8 ℃, with no softening, flowing, or decomposition observed at an ambient temperature of 24 ℃ plus a temperature rise of 18.8 ℃; ② XRD verification showed that Cs after high temperature... 0.33 The WO3 crystal structure remained unchanged, and the PVA-PA matrix did not undergo thermal oxidation degradation; the photothermal conversion efficiency remained stable, the near-infrared absorption rate remained above 73%, and the anti-fog performance did not decline.

[0080] 2. Low-temperature performance testing Test conditions: Simulated winter low temperature and high humidity environment, ambient temperature 5 ℃, relative humidity 80%, xenon lamp irradiance 800 W / m 2 Simulates weak sunlight; Testing indicators: low-temperature film formation, photothermal start-up speed, and anti-fogging effect; Results: ① The coating can still form a film normally under low temperature conditions without cracking or peeling; ② The photothermal start-up speed is slightly slower, but thermal equilibrium can be reached within 15 minutes, with a temperature rise of 15.2 ℃. The surface temperature is higher than the dew point, and the dew point is about 3 ℃ under 5 ℃ conditions; ③ During the 30-minute test, the coating remained transparent and fog-free, confirming that it can effectively suppress condensation under low temperature and weak sunlight conditions and is suitable for winter use.

[0081] The above descriptions are merely embodiments of the present invention, and common knowledge such as specific technical solutions and / or characteristics are not described in detail here. It should be noted that those skilled in the art can make various modifications and improvements without departing from the technical solutions of the present invention, and these should also be considered within the scope of protection of the present invention. These modifications and improvements will not affect the effectiveness of the implementation of the present invention or the practicality of the patent. The scope of protection claimed in this application should be determined by the content of its claims, and the specific embodiments described in the specification can be used to interpret the content of the claims.

Claims

1. An anti-fog coating, characterized in that, It is made from photothermal nanoparticles, polyvinyl alcohol, phytic acid, glutaraldehyde, and deionized water in a ratio of 0.6 kg: 15 kg: 20 L: 10 L: 150 L; The coating is obtained by sequentially adding photothermal nanoparticles, polyvinyl alcohol, phytic acid solution, and glutaraldehyde solution to deionized water, mixing, and drying.

2. The coating of claim 1, wherein, The photothermal nanoparticles include at least one of metal nanoparticles, metal oxide nanoparticles, carbon-based nanoparticles, and semiconductor nanoparticles.

3. The coating of claim 2, wherein, The semiconductor nanoparticles are cesium tungstate nanoparticles.

4. The coating of claim 1, wherein, The concentrations of the phytic acid solution and the glutaraldehyde solution are both 3 wt% or 8 wt%.

5. The method of claim 1, wherein the method further comprises the step of applying a layer of a material having a high solar absorptance and low emissivity on the surface of the substrate. Includes the following steps: Prepare the raw materials according to the proportions; Photothermal nanoparticles were added to deionized water and ultrasonically dispersed to obtain a nanoparticle suspension. Polyvinyl alcohol was added to the nanoparticle suspension and dissolved by stirring in a water bath to obtain mixed solution A; Phytic acid was added to mixture A and dispersed by ultrasonication to obtain mixture B. Glutaraldehyde was added to mixture B, and the mixture was stirred to react, thus obtaining the coating. The coating is applied to the substrate surface and dried. After the coating is formed, a solar-thermal anti-fog coating is obtained.

6. The preparation method according to claim 5, characterized in that, The ultrasonic dispersion power is 500~1500 W, and the ultrasonic dispersion time is 20 min.

7. The preparation method according to claim 5, characterized in that, The conditions for stirring and dissolving in the water bath are 55°C, stirring for 30-60 minutes, and stirring speed of 120-400 rpm.

8. The preparation method according to claim 5, characterized in that, The stirring reaction takes 10 minutes and the stirring speed is 120~350 rpm.

9. The preparation method according to claim 5, characterized in that, The drying process is carried out in an environment of 37°C and 30% relative humidity.

10. An application of the coating according to any one of claims 1 to 3, characterized in that, Apply 33 μL of coating to each square centimeter of glass substrate surface, and after drying, form an anti-fog coating.

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