Highly transparent antireflective composite self-cleaning coating and method

Abstract

The application discloses a high-transmittance anti-reflection composite self-cleaning coating and a method, which comprises a bottom anti-reflection film layer and a surface self-cleaning film layer, and the bottom anti-reflection film layer is attached to the surface of a transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflection film layer. The application relates to the technical field of optical functional coating. The high-transmittance anti-reflection composite self-cleaning coating and the method realize the continuous refractive index transition of air, the coating and the substrate through the gradient refractive index bottom structure, completely eliminate the interface light reflection loss, have high-transmittance wide-band anti-reflection, excellent optical performance, greatly improved light transmittance and anti-reflection uniformity compared with traditional single-layer coatings, no spectral reflection peak defect, through the double-layer functional partition design, the bottom focuses on optical performance, the surface focuses on self-cleaning protection, the composite titanium dioxide system considers both photocatalytic degradation and ultraviolet protection, the functions are synergistic without conflict, and the self-cleaning is long-acting and stable.

Description

Technical Field

[0001] This invention relates to the field of optical functional coating technology, specifically to a high-transmittance anti-reflection composite self-cleaning coating and method. Background Technology

[0002] Transparent optical substrates (glass, acrylic, PC sheets, etc.) are widely used in many fields such as photovoltaic new energy, optical instruments, building curtain walls, automotive displays, and smart wearables. The surface of these substrates inherently suffers from light reflection loss; ordinary transparent glass has a visible light reflectance of approximately 4% to 8%, which directly reduces the light transmission efficiency, imaging clarity, and photoelectric conversion efficiency of optical devices and photovoltaic modules. Furthermore, the substrate surface easily absorbs dust, oil, and moisture from the air, leading to dirt accumulation over time, further reducing light transmission performance. Manual cleaning is difficult and costly, and the substrate surface is also prone to scratches and damage.

[0003] In existing technologies, antireflective coatings mostly employ single-layer silica sol-gel coatings, achieving antireflection through a single refractive index adjustment. However, the refractive index adjustment range is limited, failing to achieve broad-spectrum, high-transmittance antireflection. Furthermore, the coating's simple pore structure results in poor mechanical properties and insufficient wear and weather resistance. To achieve self-cleaning functionality, existing solutions often directly dope photocatalytic nanoparticles into the antireflective coating. However, nanoparticles are prone to aggregation, causing optical scattering and significantly reducing transmittance, leading to a problem of "mutual constraint between antireflection and self-cleaning performance."

[0004] Some dual-layer composite coating technologies have significant drawbacks: poor matching of refractive indices and coefficients of thermal expansion between the upper and lower layers, leading to interfacial stress during curing, resulting in delamination and coating cracking; lack of coupling modification at the film interface, resulting in weak adhesion and easy localized peeling after long-term use; and the fact that self-cleaning coatings often employ a single hydrophilic or hydrophobic system, failing to simultaneously guarantee long-term dustproofing and oil degradation performance, easily failing and yellowing after UV aging, and exhibiting poor optical stability. Furthermore, existing preparation processes often employ one-time high-temperature curing, which easily causes thermal failure of nano-functional particles and substrate deformation, resulting in low product yield and hindering large-scale application.

[0005] In summary, there is an urgent need for a composite coating that combines broad-spectrum high transmittance and anti-reflection, long-lasting self-cleaning, high adhesion, and weather and wear resistance, along with a compatible, stable, and industrially scalable preparation process to solve the core problems of performance contradictions, structural defects, and process instability in existing technologies. Summary of the Invention

[0006] (a) Technical problems to be solved To address the shortcomings of existing technologies, this invention provides a high-transmittance anti-reflection composite self-cleaning coating and method, which solves the technical problems of low light transmittance, poor anti-reflection effect, conflict between self-cleaning and optical performance, weak interlayer bonding, poor weather resistance and wear resistance, and insufficient process stability of existing coatings. It achieves integrated modification of transparent substrates with wide-spectrum high transmittance anti-reflection, long-lasting self-cleaning, and high-stability protection.

[0007] (II) Technical Solution To achieve the above objectives, the present invention is implemented through the following technical solution: a high-transparency anti-reflection composite self-cleaning coating, comprising a bottom anti-reflection film layer and a surface self-cleaning film layer compositely attached to the surface of a transparent substrate, wherein the bottom anti-reflection film layer is attached to the surface of the transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflection film layer. The bottom antireflective film is a gradient refractive index nano-silica film, and its raw materials are formulated in the following proportions by mass: 8-15 parts modified hollow silica nanoparticles, 20-30 parts tetraethyl orthosilicate, 40-55 parts anhydrous ethanol, 8-12 parts deionized water, 0.3-0.8 parts acidic catalyst, and 1.2-2 parts interface coupling agent; The self-cleaning surface film is a hydrophobic and hydrophilic bifunctional nanocomposite film, and its raw materials are formulated in the following proportions by weight: 5-10 parts of modified nano titanium dioxide, 3-6 parts of hydrophobic modified fumed silica, 0.8-1.5 parts of silane coupling agent, 2-4 parts of film-forming aid, 0.2-0.5 parts of UV stabilizer, and 35-45 parts of anhydrous ethanol; The bottom antireflective film and the surface self-cleaning film are connected by covalent bonds formed by interfacial coupling molecules, without interfacial delamination or optical scattering defects.

[0008] Preferably, the modified hollow silica nanoparticles are treated with ethanolamine for surface hydroxyl modification, and the acid catalyst is dilute hydrochloric acid or glacial acetic acid, and the interfacial coupling agent is γ-aminopropyltriethoxysilane.

[0009] Preferably, the modified nano-titanium dioxide is a composite titanium dioxide of rutile and anatase types, with a rutile to anatase mass ratio of 1:3-4, and is hydrophobically modified with silane, and the specific surface area of ​​the hydrophobically modified fumed silica is 200-300 m² / g. 2 / g, wherein the film-forming aid is ethylene glycol monobutyl ether, and the UV stabilizer is a hindered amine UV stabilizer.

[0010] Preferably, the transparent substrate is any one of ultra-white float glass, acrylic sheet, or PC optical transparent sheet.

[0011] This invention also provides a method for preparing a high-transmittance anti-reflection composite self-cleaning coating, specifically including the following steps: S1. Substrate pretreatment: The transparent substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove surface oil, dust and impurities. The ultrasonic cleaning time is 10-15 minutes for each step. After cleaning, the substrate is dried in an oven at 60-70℃. Then, the surface of the substrate is activated by plasma with an activation power of 80-120W and an activation time of 3-5 minutes to obtain an activated substrate. S2. Preparation of bottom antireflection coating solution: Mix anhydrous ethanol, deionized water and acidic catalyst according to the formula and stir. Slowly add tetraethyl orthosilicate and stir at room temperature for 30-40 min to carry out hydrolysis reaction. Then add modified hollow silica nanoparticles and interface coupling agent, heat to 40-50℃ and stir at a constant temperature for 1.5-2 h. Let stand and age for 12-18 h. After filtration, a uniform and transparent bottom antireflection coating solution is obtained. S3. Base film coating and pre-curing: The base antireflective coating liquid is uniformly coated onto the surface of the activated substrate using spin coating or dip coating processes. The spin coating speed is 2000-3000 r / min and the spin coating time is 30-50s; the dip coating speed is 8-12cm / min. After coating, the solvent is allowed to evaporate at room temperature for 10-15min, and then the substrate is placed in an oven at 80-100℃ for pre-curing for 30-40min to form a dense base film with a gradient refractive index. S4. Preparation of surface self-cleaning coating solution: Mix anhydrous ethanol, film-forming aid, and silane coupling agent evenly, add modified nano titanium dioxide and hydrophobic modified fumed silica, disperse at high speed for 20-30 min at a dispersion speed of 8000-10000 r / min, finally add UV stabilizer, stir at low speed for 10-15 min, and ultrasonically defoam for 15-20 min to obtain a uniformly dispersed surface self-cleaning coating solution; S5. Surface film coating and overall curing: Apply the self-cleaning coating liquid evenly to the pre-cured bottom film surface, using the same coating method as the bottom surface. Allow the solvent to evaporate at room temperature for 10 minutes. Use a segmented gradient curing process: first, cure at a low temperature of 90-110℃ for 40-50 minutes, then raise the temperature to 140-160℃ for a high temperature of 60-80 minutes, and allow it to cool naturally to room temperature to obtain a high-transmittance anti-reflection composite self-cleaning coating.

[0012] Preferably, in step S2, the stirring speed during the hydrolysis reaction is 300-400 r / min, the aging temperature is 20-25℃, and the filtration is performed using a 0.22μm organic filter membrane.

[0013] Preferably, in the high-speed dispersion process of step S4, an ice-water bath is used for temperature control, and the system temperature is controlled below 25°C to avoid the agglomeration and failure of nanoparticles.

[0014] Preferably, the heating rate of the segmented gradient curing in step S5 is 3-5℃ / min, and the curing process adopts a dust-free hot air circulation environment.

[0015] (III) Beneficial Effects This invention provides a high-transmittance anti-reflective composite self-cleaning coating and method. Compared with the prior art, it has the following advantages: (1) The high-transmittance anti-reflection composite self-cleaning coating and method achieves continuous refractive index transition of air, coating and substrate by adopting a gradient refractive index bottom structure, completely eliminating interface light reflection loss, high transmittance and wide-band anti-reflection, excellent optical performance, compared with traditional single-layer coating, the transmittance is greatly improved, the anti-reflection uniformity is greatly improved, and there is no spectral reflection peak defect.

[0016] (2) The high transmittance anti-reflection composite self-cleaning coating and method adopt a dual-layer functional partition design, with the bottom surface focusing on optical performance and the surface focusing on self-cleaning protection, avoiding optical loss caused by functional particle doping. The composite titanium dioxide system takes into account both photocatalytic degradation and ultraviolet protection, with synergistic and conflict-free functions, long-term and stable self-cleaning, and the super-hydrophilic microstructure achieves a dual self-cleaning effect of passive dust prevention and active decontamination. There is no dirt accumulation after long-term use, and the light transmittance performance decays very little.

[0017] (3) The high-transmittance anti-reflection composite self-cleaning coating and method are connected by covalent bonds through interface coupling agent, which greatly enhances the bonding force of the double film layer. After wear and wiping, there is no peeling or scratches. The interlayer bonding force is strong and the mechanical weather resistance is excellent. With the addition of UV stabilizer and rutile titanium dioxide, there is no yellowing, cracking or delamination after UV aging test, which is suitable for long-term complex outdoor working conditions.

[0018] (4) The high-transparency anti-reflection composite self-cleaning coating and method adopts a sol-gel low-temperature film formation + segmented gradient curing process. The process conditions are mild and will not cause deformation or aging of transparent substrates. It is suitable for various substrates such as glass, acrylic, and PC. The coating process is simple, stable and controllable, and has wide applicability. It can be mass-produced through spin coating and dip coating. The raw material cost is low and the industrialization feasibility is high. Attached Figure Description

[0019] Figure 1 This is a flowchart of the method for preparing the high-transmittance anti-reflection composite self-cleaning coating of the present invention. Detailed Implementation

[0020] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0021] Please see Figure 1The present invention provides three technical solutions: a high-transmittance anti-reflective composite self-cleaning coating and a method, specifically including the following embodiments: Example 1: A high-transmittance anti-reflection composite self-cleaning coating, comprising a bottom anti-reflection film layer and a surface self-cleaning film layer adhered to the surface of a transparent substrate, wherein the bottom anti-reflection film layer is attached to the surface of the transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflection film layer. The bottom antireflective film is a gradient refractive index nano-silica film, and its raw materials are formulated by mass ratio as follows: 10 parts modified hollow silica nanoparticles, 25 parts tetraethyl orthosilicate, 48 parts anhydrous ethanol, 10 parts deionized water, 0.5 parts acidic catalyst, and 1.8 parts interface coupling agent. The modified hollow silica nanoparticles are modified with hydroxyl groups on the surface of ethanolamine, and the acidic catalyst is dilute hydrochloric acid or glacial acetic acid. The interface coupling agent is γ-aminopropyltriethoxysilane. The surface self-cleaning film is a hydrophobic and hydrophilic bifunctional nanocomposite film. Its raw materials, by weight, are: 7 parts modified nano-titanium dioxide, 5 parts hydrophobically modified fumed silica, 1.2 parts silane coupling agent, 3 parts film-forming aid, 0.3 parts UV stabilizer, and 40 parts anhydrous ethanol. The modified nano-titanium dioxide is a composite of rutile and anatase types, with a rutile to anatase mass ratio of 1:3.5. It is hydrophobically modified with silane, and the hydrophobically modified fumed silica has a specific surface area of ​​250 m². 2 / g, the film-forming aid is ethylene glycol monobutyl ether, and the UV stabilizer is a hindered amine UV stabilizer; The bottom antireflective coating and the surface self-cleaning coating are connected by covalent bonds formed by interfacial coupling molecules, eliminating interfacial delamination and optical scattering defects.

[0022] In this embodiment of the invention, the transparent substrate is ultra-white float glass.

[0023] This invention also provides a method for preparing a high-transmittance anti-reflection composite self-cleaning coating, specifically including the following steps: S1. Substrate pretreatment: The transparent substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove surface oil, dust and impurities. The ultrasonic cleaning time is 13 minutes for each. After cleaning, the substrate is dried in a 65℃ oven. Then, the substrate surface is activated by plasma with an activation power of 100W and an activation time of 4 minutes to obtain an activated substrate. S2. Preparation of bottom antireflection coating solution: Anhydrous ethanol, deionized water and acidic catalyst were mixed and stirred according to the formula. Tetraethyl orthosilicate was slowly added dropwise. The mixture was stirred at room temperature for 35 min to carry out hydrolysis reaction. Modified hollow silica nanoparticles and interfacial coupling agent were then added. The mixture was heated to 45℃ and stirred at a constant temperature for 1.8 h. After standing and aging for 16 h, a uniform and transparent bottom antireflection coating solution was obtained after filtration. The stirring speed during the hydrolysis reaction was 350 r / min, the aging temperature was 23℃, and filtration was carried out using a 0.22 μm organic filter membrane. S3. Coating and Pre-curing of the Bottom Film Layer: The bottom anti-reflective coating liquid is uniformly coated onto the surface of the activated substrate using spin coating or dip coating processes. The spin coating speed is 2500 r / min and the spin coating time is 40 s. The dip coating speed is 10 cm / min. After coating, the solvent is allowed to evaporate at room temperature for 13 min. Then, it is placed in a 90℃ oven for pre-curing for 35 min to form a dense bottom film layer with a gradient refractive index. S4. Preparation of surface self-cleaning coating solution: Anhydrous ethanol, film-forming aid, and silane coupling agent are mixed evenly, modified nano-titanium dioxide and hydrophobic modified fumed silica are added, and the mixture is dispersed at high speed for 25 min at a dispersion speed of 9000 r / min. Finally, UV stabilizer is added, and the mixture is stirred at low speed for 13 min and ultrasonically defoamed for 17 min to obtain a uniformly dispersed surface self-cleaning coating solution. During the high-speed dispersion process, an ice-water bath is used to control the temperature, and the system temperature is controlled below 25℃ to avoid the agglomeration and failure of nanoparticles. S5. Surface film coating and overall curing: The self-cleaning coating liquid is uniformly coated onto the pre-cured bottom film surface. The coating method is the same as that for the bottom surface. The solvent is allowed to evaporate at room temperature for 10 minutes. A segmented gradient curing process is adopted: first, the surface is cured at a low temperature of 100℃ for 45 minutes, then the temperature is raised to 150℃ for 70 minutes. The surface is then naturally cooled to room temperature to obtain a high-transmittance anti-reflection composite self-cleaning coating. The heating rate of the segmented gradient curing is 4℃ / min. The curing process adopts a dust-free hot air circulation environment.

[0024] Example 2: A high-transmittance anti-reflective composite self-cleaning coating, comprising a bottom anti-reflective film layer and a surface self-cleaning film layer adhered to the surface of a transparent substrate, wherein the bottom anti-reflective film layer is attached to the surface of the transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflective film layer. The bottom antireflective film is a gradient refractive index nano-silica film, and its raw materials are formulated by mass ratio as follows: 8 parts modified hollow silica nanoparticles, 20 parts tetraethyl orthosilicate, 40 parts anhydrous ethanol, 8 parts deionized water, 0.3 parts acidic catalyst, and 1.2 parts interface coupling agent. The modified hollow silica nanoparticles are modified with hydroxyl groups on the surface of ethanolamine, and the acidic catalyst is dilute hydrochloric acid or glacial acetic acid. The interface coupling agent is γ-aminopropyltriethoxysilane. The surface self-cleaning film is a hydrophobic and hydrophilic bifunctional nanocomposite film. Its raw materials, by weight, are: 5 parts modified nano-titanium dioxide, 3 parts hydrophobically modified fumed silica, 0.8 parts silane coupling agent, 2 parts film-forming aid, 0.2 parts UV stabilizer, and 35 parts anhydrous ethanol. The modified nano-titanium dioxide is a composite of rutile and anatase types, with a rutile to anatase mass ratio of 1:3. It is hydrophobically modified with silane, and the hydrophobically modified fumed silica has a specific surface area of ​​200 m². 2 / g, the film-forming aid is ethylene glycol monobutyl ether, and the UV stabilizer is a hindered amine UV stabilizer; The bottom antireflective coating and the surface self-cleaning coating are connected by covalent bonds formed by interfacial coupling molecules, eliminating interfacial delamination and optical scattering defects.

[0025] In this embodiment of the invention, the transparent substrate is an acrylic sheet.

[0026] This invention also provides a method for preparing a high-transmittance anti-reflection composite self-cleaning coating, specifically including the following steps: S1. Substrate pretreatment: The transparent substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove surface oil, dust and impurities. The ultrasonic cleaning time is 10 minutes for each. After cleaning, the substrate is dried in a 60℃ oven. Then, the surface of the substrate is activated by plasma with an activation power of 80W and an activation time of 3 minutes to obtain an activated substrate. S2. Preparation of bottom antireflection coating solution: Anhydrous ethanol, deionized water and acidic catalyst were mixed and stirred according to the formula. Tetraethyl orthosilicate was slowly added dropwise. The mixture was stirred at room temperature for 30 min to carry out hydrolysis reaction. Modified hollow silica nanoparticles and interfacial coupling agent were then added. The mixture was heated to 40℃ and stirred at a constant temperature for 1.5 h. After standing and aging for 12 h, a uniform and transparent bottom antireflection coating solution was obtained after filtration. The stirring speed during the hydrolysis reaction was 300 r / min, the aging temperature was 20℃, and filtration was carried out using a 0.22 μm organic filter membrane. S3. Coating and Pre-curing of the Bottom Film Layer: The bottom anti-reflective coating liquid is uniformly coated onto the surface of the activated substrate using spin coating or dip coating processes. The spin coating speed is 2000 r / min and the spin coating time is 30s. The dip coating speed is 8cm / min. After coating, the solvent is allowed to evaporate at room temperature for 10min. Then, it is placed in an 80℃ oven for pre-curing for 30min to form a dense bottom film layer with a gradient refractive index. S4. Preparation of surface self-cleaning coating solution: Mix anhydrous ethanol, film-forming aid, and silane coupling agent evenly, add modified nano-titanium dioxide and hydrophobic modified fumed silica, disperse at high speed for 20 min at a dispersion speed of 8000 r / min, finally add UV stabilizer, stir at low speed for 10 min, and ultrasonically defoam for 15 min to obtain a uniformly dispersed surface self-cleaning coating solution. During the high-speed dispersion process, an ice-water bath is used to control the temperature, and the system temperature is controlled below 25℃ to avoid nanoparticle agglomeration and failure. S5. Surface film coating and overall curing: The self-cleaning coating liquid is uniformly coated onto the pre-cured bottom film surface. The coating method is the same as that for the bottom surface. The solvent is allowed to evaporate at room temperature for 10 minutes. A segmented gradient curing process is adopted: first, low temperature curing at 90℃ for 40 minutes, then high temperature curing at 140℃ for 60 minutes, and then naturally cooled to room temperature to obtain a high-transmittance anti-reflection composite self-cleaning coating. The heating rate of the segmented gradient curing is 3℃ / min. The curing process adopts a dust-free hot air circulation environment.

[0027] Example 3: A high-transmittance anti-reflective composite self-cleaning coating, comprising a bottom anti-reflective film layer and a surface self-cleaning film layer adhered to the surface of a transparent substrate, wherein the bottom anti-reflective film layer is attached to the surface of the transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflective film layer. The bottom antireflective film is a gradient refractive index nano-silica film, and its raw materials are formulated by mass ratio as follows: 15 parts modified hollow silica nanoparticles, 30 parts tetraethyl orthosilicate, 55 parts anhydrous ethanol, 12 parts deionized water, 0.8 parts acidic catalyst, and 2 parts interface coupling agent. The modified hollow silica nanoparticles are modified with hydroxyl groups on the surface of ethanolamine, and the acidic catalyst is dilute hydrochloric acid or glacial acetic acid. The interface coupling agent is γ-aminopropyltriethoxysilane. The self-cleaning surface film is a hydrophobic and hydrophilic bifunctional nanocomposite film. Its raw materials, by weight, are: 10 parts modified nano-titanium dioxide, 6 parts hydrophobically modified fumed silica, 1.5 parts silane coupling agent, 4 parts film-forming aid, 0.5 parts UV stabilizer, and 45 parts anhydrous ethanol. The modified nano-titanium dioxide is a composite of rutile and anatase types, with a rutile to anatase mass ratio of 1:4. It is hydrophobically modified with silane, and the hydrophobically modified fumed silica has a specific surface area of ​​300 m². 2 / g, the film-forming aid is ethylene glycol monobutyl ether, and the UV stabilizer is a hindered amine UV stabilizer; The bottom antireflective coating and the surface self-cleaning coating are connected by covalent bonds formed by interfacial coupling molecules, eliminating interfacial delamination and optical scattering defects.

[0028] In this embodiment of the invention, the transparent substrate is a PC optical transparent plate.

[0029] This invention also provides a method for preparing a high-transmittance anti-reflection composite self-cleaning coating, specifically including the following steps: S1. Substrate pretreatment: The transparent substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove surface oil, dust and impurities. The ultrasonic cleaning time is 15 minutes for each. After cleaning, it is placed in a 70℃ oven to dry. Then, the substrate surface is activated by plasma with an activation power of 120W and an activation time of 5 minutes to obtain an activated substrate. S2. Preparation of bottom antireflection coating solution: Anhydrous ethanol, deionized water and acidic catalyst were mixed and stirred according to the formula. Tetraethyl orthosilicate was slowly added dropwise and stirred at room temperature for 40 min to carry out hydrolysis reaction. Modified hollow silica nanoparticles and interfacial coupling agent were then added. The temperature was raised to 50℃ and stirred at a constant temperature for 2 h. After standing and aging for 18 h, a uniform and transparent bottom antireflection coating solution was obtained after filtration. The stirring speed during the hydrolysis reaction was 400 r / min, the aging temperature was 25℃, and filtration was carried out using a 0.22 μm organic filter membrane. S3. Coating and Pre-curing of the Bottom Film Layer: The bottom antireflective coating liquid is uniformly coated onto the surface of the activated substrate using spin coating or dip coating processes. The spin coating speed is 3000 r / min and the spin coating time is 50s. The dip coating speed is 12cm / min. After coating, the solvent is allowed to evaporate at room temperature for 15min. Then, it is placed in a 100℃ oven for pre-curing for 40min to form a dense bottom film layer with a gradient refractive index. S4. Preparation of surface self-cleaning coating solution: Mix anhydrous ethanol, film-forming aid, and silane coupling agent evenly, add modified nano-titanium dioxide and hydrophobic modified fumed silica, disperse at high speed for 30 min at a dispersion speed of 10000 r / min, finally add UV stabilizer, stir at low speed for 15 min, and ultrasonically defoam for 20 min to obtain a uniformly dispersed surface self-cleaning coating solution. During the high-speed dispersion process, an ice-water bath is used to control the temperature, and the system temperature is controlled below 25℃ to avoid nanoparticle agglomeration and failure. S5. Surface film coating and overall curing: The self-cleaning coating liquid is uniformly coated onto the pre-cured bottom film surface. The coating method is the same as that for the bottom surface. The solvent is allowed to evaporate at room temperature for 10 minutes. A segmented gradient curing process is adopted: first, the temperature is raised to 110℃ for 50 minutes, and then the temperature is raised to 160℃ for 80 minutes. The coating is then allowed to cool naturally to room temperature to obtain a high-transmittance anti-reflection composite self-cleaning coating. The heating rate of the segmented gradient curing is 5℃ / min. The curing process adopts a dust-free hot air circulation environment.

[0030] In summary, this invention, by employing a gradient refractive index bottom structure, achieves a continuous refractive index transition between air, coating, and substrate, completely eliminating interfacial light reflection loss. It boasts high transmittance, wide-band anti-reflection, and excellent optical performance. Compared to traditional single-layer coatings, it significantly improves transmittance and anti-reflection uniformity, eliminating spectral reflectance peak defects. Through a dual-layer functional partition design, the bottom layer focuses on optical performance, while the surface layer focuses on self-cleaning protection, avoiding optical loss caused by functional particle doping. The composite titanium dioxide system balances photocatalytic degradation and UV protection, with synergistic and conflict-free functions, ensuring long-lasting self-cleaning stability. The superhydrophilic microstructure achieves both passive dust prevention and active decontamination, preventing dirt buildup even after long-term use. The film exhibits extremely low light transmittance degradation due to its layering and the use of interfacial coupling agents to construct covalent bonds, significantly enhancing the adhesion between the two layers. It remains scratch-free and resistant to wear and wiping, demonstrating strong interlayer bonding and excellent mechanical and weather resistance. The addition of UV stabilizers and rutile titanium dioxide ensures no yellowing, cracking, or delamination after UV aging tests, making it suitable for long-term, complex outdoor applications. Utilizing a sol-gel low-temperature film formation and segmented gradient curing process, the process conditions are mild and will not cause deformation or aging of the transparent substrate. It is compatible with various substrates such as glass, acrylic, and PC. The coating process is simple, stable, and controllable, with wide applicability. It can be mass-produced through spin coating and dip coating, with low raw material costs and high industrial feasibility.

[0031] Furthermore, any content not described in detail in this specification is existing technology known to those skilled in the art.

[0032] It should be noted that, in this document, relational terms such as "first" and "second" are used only to distinguish one entity or operation from another, and do not necessarily require or imply any such actual relationship or order between these entities or operations. Furthermore, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such process, method, article, or apparatus.

[0033] Although embodiments of the invention have been shown and described, it will be understood by those skilled in the art that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the invention, the scope of which is defined by the appended claims and their equivalents.

Claims

1. A high-transmittance anti-reflective composite self-cleaning coating, characterized in that: It includes a bottom anti-reflective film layer and a surface self-cleaning film layer that are compositely attached to the surface of a transparent substrate. The bottom anti-reflective film layer is attached to the surface of the transparent substrate, and the surface self-cleaning film layer covers the surface of the bottom anti-reflective film layer. The bottom antireflective film is a gradient refractive index nano-silica film, and its raw materials are formulated in the following proportions by mass: 8-15 parts modified hollow silica nanoparticles, 20-30 parts tetraethyl orthosilicate, 40-55 parts anhydrous ethanol, 8-12 parts deionized water, 0.3-0.8 parts acidic catalyst, and 1.2-2 parts interface coupling agent; The self-cleaning surface film is a hydrophobic and hydrophilic bifunctional nanocomposite film, and its raw materials are formulated in the following proportions by weight: 5-10 parts of modified nano titanium dioxide, 3-6 parts of hydrophobic modified fumed silica, 0.8-1.5 parts of silane coupling agent, 2-4 parts of film-forming aid, 0.2-0.5 parts of UV stabilizer, and 35-45 parts of anhydrous ethanol; The bottom antireflective film and the surface self-cleaning film are connected by covalent bonds formed by interfacial coupling molecules, without interfacial delamination or optical scattering defects.

2. The high-transmittance anti-reflective composite self-cleaning coating according to claim 1, characterized in that: The modified hollow silica nanoparticles are modified with ethanolamine for surface hydroxyl modification, and the acid catalyst is dilute hydrochloric acid or glacial acetic acid. The interfacial coupling agent is γ-aminopropyltriethoxysilane.

3. The high-transmittance anti-reflective composite self-cleaning coating according to claim 1, characterized in that: The modified nano-titanium dioxide is a composite titanium dioxide of rutile and anatase types, with a rutile to anatase mass ratio of 1:3-4. It is hydrophobically modified with silane, and the specific surface area of ​​the hydrophobically modified fumed silica is 200-300 m² / g. 2 / g, wherein the film-forming aid is ethylene glycol monobutyl ether, and the UV stabilizer is a hindered amine UV stabilizer.

4. The high-transmittance anti-reflective composite self-cleaning coating according to claim 1, characterized in that: The transparent substrate is any one of ultra-white float glass, acrylic sheet, or PC optical transparent sheet.

5. A method for preparing a high-transmittance anti-reflective composite self-cleaning coating, characterized in that: The method for preparing the high-transmittance anti-reflection composite self-cleaning coating according to any one of claims 1-4 specifically includes the following steps: S1. Substrate pretreatment: The transparent substrate is ultrasonically cleaned sequentially with acetone, anhydrous ethanol and deionized water to remove surface oil, dust and impurities. The ultrasonic cleaning time is 10-15 minutes for each step. After cleaning, the substrate is dried in an oven at 60-70℃. Then, the surface of the substrate is activated by plasma with an activation power of 80-120W and an activation time of 3-5 minutes to obtain an activated substrate. S2. Preparation of bottom antireflection coating solution: Mix anhydrous ethanol, deionized water and acidic catalyst according to the formula and stir. Slowly add tetraethyl orthosilicate and stir at room temperature for 30-40 min to carry out hydrolysis reaction. Then add modified hollow silica nanoparticles and interface coupling agent, heat to 40-50℃ and stir at a constant temperature for 1.5-2 h. Let stand and age for 12-18 h. After filtration, a uniform and transparent bottom antireflection coating solution is obtained. S3. Base film coating and pre-curing: The base antireflective coating liquid is uniformly coated onto the surface of the activated substrate using spin coating or dip coating processes. The spin coating speed is 2000-3000 r / min and the spin coating time is 30-50s; the dip coating speed is 8-12cm / min. After coating, the solvent is allowed to evaporate at room temperature for 10-15min, and then the substrate is placed in an oven at 80-100℃ for pre-curing for 30-40min to form a dense base film with a gradient refractive index. S4. Preparation of surface self-cleaning coating solution: Mix anhydrous ethanol, film-forming aid, and silane coupling agent evenly, add modified nano titanium dioxide and hydrophobic modified fumed silica, disperse at high speed for 20-30 min at a dispersion speed of 8000-10000 r / min, finally add UV stabilizer, stir at low speed for 10-15 min, and ultrasonically defoam for 15-20 min to obtain a uniformly dispersed surface self-cleaning coating solution; S5. Surface film coating and overall curing: Apply the self-cleaning coating liquid evenly to the pre-cured bottom film surface, using the same coating method as the bottom surface. Allow the solvent to evaporate at room temperature for 10 minutes. Use a segmented gradient curing process: first, cure at a low temperature of 90-110℃ for 40-50 minutes, then raise the temperature to 140-160℃ for a high temperature of 60-80 minutes, and allow it to cool naturally to room temperature to obtain a high-transmittance anti-reflection composite self-cleaning coating.

6. The method for preparing the high-transmittance anti-reflection composite self-cleaning coating according to claim 5, characterized in that, In step S2, the stirring speed during the hydrolysis reaction is 300-400 r / min, the aging temperature is 20-25℃, and filtration is performed using a 0.22μm organic filter membrane.

7. The method for preparing the high-transmittance anti-reflection composite self-cleaning coating according to claim 5, characterized in that, In step S4, during the high-speed dispersion process, an ice-water bath is used for temperature control, and the system temperature is kept below 25°C.

8. The method for preparing the high-transmittance anti-reflection composite self-cleaning coating according to claim 5, characterized in that, In step S5, the heating rate of the segmented gradient curing is 3-5℃ / min, and the curing process adopts a dust-free hot air circulation environment.

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