High-hardness self-cleaning antireflection coating and preparation method thereof

Abstract

The invention discloses a high-hardness self-cleaning antireflection coating and a preparation method thereof, and belongs to the technical field of nano composite materials. The coating comprises an antireflection functional coating and a hydrophobic modified coating on the surface of the antireflection functional coating, the antireflection functional coating comprises at least one periodic film layer formed by alternately overlapping low-refractive-index film layers and high-refractive-index film layers; the low-refractive-index film layer is a modified hollow silicon dioxide film layer wrapped by an oxide; and the high refractive index film layer is a silicon oxide-aluminum oxide-titanium oxide composite film layer. The preparation process is simple, reaction conditions are mild and controllable, and the prepared coating has excellent wide-spectrum light transmittance, high hardness, good dielectric property and good hydrophobic self-cleaning capacity.

Description

Technical Field

[0001] This invention belongs to the field of nanocomposite materials technology, specifically relating to a high-hardness self-cleaning antireflective coating and its preparation method. Background Technology

[0002] Anti-reflective (AR) coatings are a type of optical coating that utilizes the interference effect of light to reduce light reflection from the surface of optical components, thereby increasing the transmittance of the optical device interface. They play an important role in applications such as solar panels, architectural glass, fiber optic communication, and displays. However, during use, AR coatings often experience scratches, electrostatic dust adsorption, and the accumulation of air pollutants. Long-term use can lead to a decrease in the coating's transmittance, affecting its anti-reflective effect. Therefore, developing AR coatings with high transmittance, high hardness, high dielectric constant, and self-cleaning properties has broad application prospects.

[0003] Most antireflective coatings increase light transmittance by applying a single layer. However, a single layer can only reduce reflectivity near a certain wavelength. In contrast, multi-layer antireflective coatings can achieve superior antireflective performance over a wider wavelength range and have received increasing attention in recent years. Chinese patent CN118151267A discloses a broadband ultra-low reflective AR antireflective film and its preparation method. By stacking silicon oxide, titanium oxide, aluminum oxide, magnesium fluoride, and fluorine-containing silane-based ultra-hard waterproof film layers, an AR antireflective film with advantages such as high transmittance, high hardness, and anti-fogging and anti-oil properties is obtained. This antireflective film has 33 layers, but it is costly, has a complex preparation process, is cumbersome, and is not easy to operate. Chinese patent CN112661415A discloses an antireflective film for photovoltaic glass and its preparation method. The antireflective film includes a main layer prepared from nano-silica dispersion, hollow silica particles, pore-forming agent, and solvent, and an auxiliary layer prepared from fluorinated resin, curing agent, nano-sized inorganic particles, and organic solvent. The antireflective film prepared by this method has excellent water resistance and moisture resistance, but its wear resistance is generally poor. Summary of the Invention

[0004] To address the shortcomings of existing technologies, the first objective of this invention is to provide a high-hardness self-cleaning antireflective coating. This coating consists of a periodic film layer composed of alternating low-refractive-index and high-refractive-index film layers, which exhibits excellent antireflective effects over a wide spectral range. Simultaneously, the composite addition of silicon oxide, aluminum oxide, and titanium oxide, along with the oxide-encapsulated modified hollow silica coating, synergistically enhances the coating's self-cleaning performance and photostability while reducing yellowing of the polymer substrate.

[0005] The second objective of this invention is to provide a method for preparing a high-hardness self-cleaning antireflective coating, which has the advantages of simple operation, mild reaction conditions, and low production cost.

[0006] To achieve the above-mentioned technical objectives, the present invention provides a high-hardness self-cleaning antireflective coating, which includes an antireflective functional coating and a hydrophobic modified coating on its surface; the antireflective functional coating includes at least one periodic film layer composed of alternating low-refractive-index film layer and high-refractive-index film layer; the low-refractive-index film layer is an oxide-encapsulated modified hollow silica film layer; the high-refractive-index film layer is a silica-alumina-titanium oxide composite film layer.

[0007] The coating of this invention exhibits excellent self-cleaning properties, high hardness, and superior antireflection effects over a wide spectral range. The key lies in the selection and alternating combination of low-refractive-index and high-refractive-index film layers. Specifically, the low-refractive-index film layer in this invention employs an oxide-encapsulated and modified hollow silica structure. This hollow structure achieves an extremely low refractive index (significantly lower than conventional dense silica), which is crucial for meeting the low-refractive-index layer requirements of antireflection interference, especially for wide-spectrum applications. The hollow structure effectively reduces the overall average refractive index of the material. Simultaneously, the oxide encapsulation modification of the outer layer solves the inherent problems of weak mechanical strength and easy collapse in pure hollow silica structures, significantly and uniformly improving the density and hardness of the layer, providing a fundamental support for the high hardness of the entire coating. The high-refractive-index film layer utilizes a silica-alumina-titanium oxide composite layer, which fully leverages the synergistic effects of titanium oxide as the high-refractive-index substrate, alumina as an intermediate refractive-index bridge and stress buffer, and silica as a low-absorption stabilizing component. This homogeneous single-layer composite structure, compared to a three-layer composite structure of alumina, titanium oxide, and silica, can form an effective refractive index gradient or optimize the average refractive index within a single layer. This not only enhances the optical performance bandwidth of the single layer but also significantly reduces parasitic reflection losses caused by sharp interfaces when traditional high- and low-refractive-index materials are stacked alternately. Furthermore, the high hardness of alumina in the composite coating effectively enhances the coating's hardness and abrasion resistance. While titanium oxide has lower hardness, it possesses strong antibacterial properties under ultraviolet irradiation, effectively removing microbial contamination from the coating surface and improving its self-cleaning performance. Finally, the hydrophobic modification layer ensures the high durability of the composite coating under atmospheric moisture conditions, giving it a hydrophobic and self-cleaning effect, preventing the accumulation of dust and other contaminants on the coating surface, extending the coating's service life, and avoiding the potential environmental and human health hazards associated with commonly used fluorinated hydrophobic agents.

[0008] Experiments have shown that when two specially designed films with significant refractive index differences are alternately superimposed in a periodic structure using the present invention, a strong multilayer optical interface is formed between them. For the reflected light from adjacent interfaces, the combination of phase difference caused by film thickness and phase abrupt change caused by interface reflection results in half-wave loss between reflected light of certain specific wavelengths, thus causing destructive interference. The alternating multilayer film not only generates destructive interference at multiple different wavelengths, but also forms a refractive index gradient effect, which disperses the refractive index to multiple interfaces and cancels it out more effectively, thereby broadening the low reflectivity region from a single wavelength point to a continuous wideband.

[0009] The refractive index range of the high refractive index film of the present invention is 1.30~1.45, and the refractive index range of the low refractive index film is 1.10~1.25.

[0010] As a preferred embodiment, the total number of antireflective coating layers is 2 to 10, and the thickness of a single layer is 9 to 340 nm.

[0011] As a preferred embodiment, the high-hardness self-cleaning antireflective coating has a silicon oxide-alumina-titanium oxide composite film layer in contact with the substrate, and an oxide-encapsulated and modified hollow silicon dioxide film layer in contact with the hydrophobic coating. The antireflective functional coating has a lower equivalent refractive index in the contact layer with the hydrophobic modified coating, while the contact layer closer to the substrate has a higher equivalent refractive index. This facilitates the formation of a refractive index gradient along the light propagation direction, further enhancing the antireflective effect.

[0012] As a preferred embodiment, the preparation process of the oxide-encapsulated modified hollow silica film is as follows: polyethylene glycol (PEG) and tetraethyl orthosilicate are reacted in an organic solvent-water mixture under alkaline conditions via a sol-gel reaction to obtain a core-shell structured silica sol; an oxide precursor is added to the core-shell structured silica sol for modification, resulting in an oxide-encapsulated modified silica sol, which is then calcined. The oxide-encapsulated modification of hollow silica directly affects the anti-reflective effect and hardness of the coating. During the preparation process, tetraethyl orthosilicate first undergoes a hydrolysis-condensation reaction to form Si-O-Si bonds. PEG, acting as a template, guides the deposition and growth of silica oligomers formed by the hydrolysis-condensation around the PEG molecular chains. As the condensation reaction continues, the silica network continuously cross-links, ultimately forming a core-shell structure with silica as the outer shell and PEG as the core. The added oxide precursor is then hydrolyzed into aluminum oxide, which interacts with the silanol groups on the surface of the core-shell silica to form an aluminum oxide-encapsulated silica sol. Finally, the PEG in the core and the residual organic solvent are decomposed by calcination, leaving a cavity inside the silica framework, thus forming an oxide-encapsulated modified hollow silica film.

[0013] As a preferred embodiment, the organic solvent in the organic solvent-water mixed solution is at least one of methanol, ethanol, isopropanol, and n-butanol; the alkaline condition is the addition of ammonia; the tetraethyl orthosilicate is added dropwise; and the sol-gel reaction conditions are: stirring at room temperature followed by standing for 10-16 hours.

[0014] As a preferred embodiment, the conditions for modification with the addition of the oxide precursor are: reaction at room temperature for 10-20 hours.

[0015] As a preferred embodiment, the calcination conditions are: a temperature of 450~500℃ and a time of 4~6h.

[0016] As a preferred embodiment, the oxide precursor is at least one of a metal salt and a metal alkoxide; wherein the metal is at least one of aluminum, titanium, antimony, tantalum, lanthanum, niobium and zirconium, and is more preferably aluminum isopropoxide.

[0017] As a preferred embodiment, the molar ratio of the oxide precursor to tetraethyl orthosilicate is (0.5~5):1.

[0018] As a preferred embodiment, the oxide in the oxide-coated modified hollow silica film is at least one selected from aluminum oxide, titanium dioxide, antimony oxide, tantalum pentoxide, lanthanum titanate, niobium pentoxide, and zirconium dioxide. Aluminum oxide is more preferred; experiments have shown that using aluminum oxide for coating modification can improve the hardness of the hollow silica, reduce damage during use, and extend its service life.

[0019] As a preferred embodiment, the hollow silica particles in the oxide-coated modified hollow silica film have a particle size of 50-400 nm. The hollow silica particles in this invention have a nanometer-scale particle size and uniform particle size, which, within the scope of this invention, ensures a certain level of light transmittance and hardness.

[0020] This invention also provides a method for preparing a high-hardness self-cleaning antireflective coating, comprising the following steps:

[0021] S1 First, a silica-alumina-titanium oxide composite sol is coated on the substrate surface. After drying and sintering, a high refractive index film layer is generated. Then, an oxide-encapsulated modified silica sol is coated. After drying and calcination, a low refractive index film layer is generated. Thus, a periodic film layer consisting of alternating low refractive index film layers and high refractive index film layers is generated on the substrate surface.

[0022] or;

[0023] On the substrate surface, a silica-alumina-titanium oxide composite sol is first coated, and after drying and sintering, a high refractive index film layer is generated. Then, an oxide-encapsulated modified silica sol is coated, and after drying and calcination, a low refractive index film layer is generated. The above operation is repeated several times to generate multiple periodic film layers on the substrate surface, which are composed of alternating low refractive index film layers and multiple high refractive index film layers.

[0024] S2 is obtained by surface hydrophobic modification of the periodic film layer formed on the substrate surface in S1.

[0025] As a preferred embodiment, the sintering conditions are: temperature 350~800℃, time 30~90min. The sintering temperature can be adjusted according to the highest withstand temperature of the glass substrate, and sintering ensures a tight bond between the coating and the substrate. In the repeated process of coating the oxide-modified silica sol, different types of oxides can be used for coating modification as needed.

[0026] As a preferred embodiment, the silica-alumina-titanium oxide composite sol is obtained by mixing silica sol, alumina sol, and titanium oxide sol, wherein the silica sol, alumina sol, and titanium oxide sol are in a molar ratio of Si, Al, and Ti of (4~10):1:(0.1~1). This invention prepares sols of silica, alumina, and titanium oxide separately, mixes the three sols uniformly to obtain a composite sol, and then gels it to prepare a coating, resulting in a composite material with uniform distribution and controllable thickness. Experiments show that when silica is used as the main coating component, cracks gradually appear in the coating as the content of alumina or titanium oxide increases, and the higher the content of alumina or titanium oxide, the more severe the cracking. Therefore, it is necessary to control the content of alumina and titanium oxide during the preparation process. Furthermore, the mixing time of the silica sol, alumina sol, and titanium oxide sol is 0.5~5 hours.

[0027] As a preferred embodiment, the preparation process of the silica sol is as follows: tetraethyl orthosilicate is stirred in an organic-water two-phase solvent in the presence of acid catalyst A and then allowed to stand.

[0028] As a preferred embodiment, the acid catalyst A is at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and oxalic acid; the organic solvent in the organic-water two-phase solvent is at least one of methanol, ethanol, isopropanol, and n-butanol; the molar ratio of tetraethyl orthosilicate, organic solvent, and water is 1:(2~30):(2~12), and the pH of the sol after adding the acid catalyst is 2~3; the standing time of the silica sol is 1~12h.

[0029] As a preferred embodiment, the alumina sol is prepared by stirring aluminum salt and chelating agent A in an organic-water two-phase solvent.

[0030] As a preferred embodiment, the aluminum salt is at least one of aluminum nitrate, aluminum chloride, aluminum sec-butoxide, and aluminum isopropoxide; the chelating agent A is at least one of acetylacetone, ethyl acetoacetate, ethylenediaminetetraacetic acid, and EDTA; the organic solvent in the organic-water two-phase solvent is an alcohol solvent; furthermore, the molar ratio of the aluminum salt, chelating agent A, alcohol solvent, and deionized water is 1:(0.1~1):(4~15):(5~40), the stirring time is 30~150 min, and the reaction temperature is 25~100℃.

[0031] As a preferred embodiment, the preparation process of the titanium dioxide sol is as follows: titanium alkoxide and chelating agent B are added to an alcohol solvent and stirred evenly to obtain mixture 1; acid catalyst B is added to an organic-water two-phase solvent and stirred to obtain a dilute acid solution, which is then added to mixture 1 and stirred to obtain the final product.

[0032] As a preferred embodiment, the titanium alkoxide satisfies the general chemical formula Ti(OR)4, wherein R is a C2-4 alkyl group; the chelating agent B is at least one of acetylacetone, ethyl acetoacetate, ethylenediaminetetraacetic acid, and EDTA; the acid catalyst B is at least one of hydrochloric acid, sulfuric acid, nitric acid, acetic acid, and oxalic acid; the organic solvent in the organic-water two-phase solvent is at least one of methanol, ethanol, isopropanol, and n-butanol; furthermore, the molar ratio of the titanium alkoxide, chelating agent B, and organic solvent is 1:(0.1-1):(10-30).

[0033] As a preferred embodiment, the surface hydrophobic modification is achieved by impregnation with a solution containing at least one hydrophobic modifier selected from stearic acid, isostearic acid, and stearate.

[0034] As a preferred embodiment, the concentration of the hydrophobic modifier in the solution is 0.01~0.5M, and the immersion treatment time is 1~4 days.

[0035] Furthermore, the drying temperature of the hydrophobically modified substrate coating is 25~100℃, and the drying time is 12~72h.

[0036] Compared with the prior art, the present invention has the following beneficial effects:

[0037] (1) The present invention has excellent anti-reflection effect over a wide spectral range by using a periodic film layer composed of alternating low refractive index film layer and high refractive index film layer; at the same time, the composite addition of silicon oxide, aluminum oxide and titanium oxide and the oxide-encapsulated modified hollow silicon dioxide coating synergistically improve the self-cleaning performance and light stability of the coating and reduce the yellowing of the polymer substrate.

[0038] (2) The present invention modifies the antireflective functional layer by hydrophobic modification. The raw materials used are non-toxic, inexpensive, biodegradable, and environmentally friendly, giving the coating good hydrophobic self-cleaning ability.

[0039] (3) The preparation method provided by the present invention prepares two coatings by sol-gel method, and the preparation process is simple. In the preparation of the composite coating of silica, alumina and titanium dioxide, the three oxide sols are mixed to obtain a composite sol and then gelled. The sol preparation process is controllable, the mixing ratio of different sols is easy to adjust and the dispersibility is good. It has the advantages of simple operation and mild reaction conditions.

[0040] (4) The low refractive index film in the coating of the present invention adopts an oxide-encapsulated and modified hollow silica structure. Its hollow structure can achieve an extremely low refractive index, which is crucial for meeting the low refractive index layer required in anti-reflection interference conditions. Especially for wide spectrum applications, the hollow structure effectively reduces the overall average refractive index of the material. At the same time, the encapsulation and modification of the outer oxide layer solves the problem of weak mechanical strength and easy collapse inherent in the pure hollow silica structure, and significantly and uniformly improves the density and hardness of the layer, providing a basic support for the high hardness of the entire coating. Attached Figure Description

[0041] Figure 1 The image shows the initial water droplet angle test result of the coating surface prepared in Example 1. Wherein, L: left water droplet angle, R: right water droplet angle, and CA: average water droplet angle.

[0042] Figure 2 The image shows the initial water droplet angle test results for the coating surface prepared in Comparative Example 1. Where L represents the left water droplet angle, R represents the right water droplet angle, and CA represents the average water droplet angle.

[0043] Figure 3 The transmittance curve of the coating prepared in Example 1 at light wavelengths of 180~1800nm.

[0044] Figure 4 The transmittance curves of the coating prepared for Comparative Example 2 at light wavelengths of 180~1800nm. Detailed Implementation

[0045] The technical solution of the present invention will be further described below with reference to specific embodiments. It should be noted that the described embodiments are only some embodiments of the present invention, and not all embodiments; these embodiments are only for better understanding of the present invention, and not for limiting the scope of protection of the present invention.

[0046] Unless otherwise specified, all reagents and raw materials used in this invention are commercially available products or products that can be prepared by known methods.

[0047] The room temperature of this invention is 25°C.

[0048] Example 1

[0049] S1. Add 2g of tetraethyl orthosilicate (TEOS) to 1mL of deionized water and 4mL of ethanol, add hydrochloric acid dropwise until the pH is 2.5, stir for 20min and let stand for 12h to obtain silica sol.

[0050] S2 Weigh 2.4g Al(Cl)3·6H2O and dissolve it in 10mL ethanol. After complete dissolution, add 5mL deionized water and 0.9g ethyl acetoacetate. Stir at room temperature for 1h to obtain alumina sol.

[0051] S3 mixes 3.4g tetrabutyl titanate (340g / mol), 0.9g ethyl acetoacetate and 12ml ethanol, adds dilute hydrochloric acid and stirs vigorously for 1h to carry out hydrolysis and condensation reaction, and lets stand for 1h to obtain titanium dioxide sol.

[0052] S4 mixes three sols—silica sol, alumina sol, and titanium dioxide sol—at a Si:Al:Ti molar ratio of 5:1:1 for 1 hour. The mixed gel is then deposited on a clean glass substrate by spraying. The substrate is then dried in an oven at 50°C for 12 hours and sintered at 550°C for 1 hour to obtain a silica-alumina-titanium dioxide film.

[0053] S5 dissolves 5g of polyethylene glycol (molecular weight 2000) in 50mL of an ethanol-water mixture (ethanol to water volume ratio 7:3), adds 4.5mL of ammonia (25% by mass), stirs for 30min, then slowly adds 5mL of TEOS, continues stirring for 5min, and lets stand for 16h. The gel is separated by filtration, washed three times with ethanol, and centrifuged. Half of the core-shell structured silica precipitate is added to 10mL of anhydrous ethanol and 2g of aluminum isopropoxide, ultrasonically dispersed, and reacted with 1mL of deionized water for 12h. The sol is then sprayed onto a substrate, dried at room temperature, and calcined in a muffle furnace at 500℃ for 4h to remove the polyethylene glycol, yielding an alumina-coated modified hollow silica film.

[0054] S6 added 2g of tetrabutyl titanate and 12ml of ethanol to the remaining core-shell structured silica precipitate and ultrasonically dispersed it. After adding dilute hydrochloric acid, the mixture was stirred vigorously for 1 hour. It was then sprayed onto the substrate coating, dried at room temperature, and calcined in a muffle furnace at 500℃ for 4 hours to remove polyethylene glycol, thus obtaining a titanium dioxide-coated modified hollow silica film.

[0055] S7 was prepared by sequentially spraying a silicon oxide-alumina-titanium oxide film, a titanium oxide-coated modified hollow silica film, a silicon oxide-alumina-titanium oxide film, and an alumina-coated modified hollow silica coating, with the thicknesses of each film being 149 nm, 146 nm, 18 nm, and 136 nm, respectively.

[0056] S8 immerses the substrate coating in an ethanol solution containing 0.01M isostearic acid for 24 hours to modify the coating for hydrophobicity. Then, it is placed in an oven and dried at 60°C for 12 hours to obtain the target coating – a high-hardness self-cleaning anti-reflective coating.

[0057] Example 2

[0058] S1. Add 2g TEOS to 1mL deionized water and 4mL ethanol, add hydrochloric acid dropwise until the pH is 2.5, stir for 20min and let stand for 12h to obtain silica sol.

[0059] S2 Weigh 2.4g Al(Cl)3·6H2O and dissolve it in 10mL ethanol. After complete dissolution, add 5mL deionized water and 0.9g ethyl acetoacetate. Stir at room temperature for 1h to obtain alumina sol.

[0060] S3 mixes 3.4g tetrabutyl titanate (340g / mol), 0.9g ethyl acetoacetate and 12ml ethanol, adds dilute hydrochloric acid and stirs vigorously for 1h to carry out hydrolysis and condensation reaction, and lets stand for 1h to obtain titanium dioxide sol.

[0061] S4 mixes the three sols in a Si:Al:Ti molar ratio of 5:1:1 for 1 hour, deposits the mixed gel on a clean glass substrate by spraying, dries it in an oven at 50°C for 12 hours, and then sintersects it at 550°C for 1 hour to obtain a silicon oxide-aluminum oxide-titanium oxide film.

[0062] S5. 3g of polyethylene glycol (molecular weight 2000) was dissolved in 50mL of an ethanol-water mixture (ethanol:water volume ratio 7:3). 4.5mL of ammonia (25% by mass) was added, and the mixture was stirred for 30min. Then, 5mL of TEOS was slowly added dropwise, and stirring continued for 5min. The mixture was allowed to stand for 16h. The gel was separated by filtration, washed three times with ethanol, centrifuged, and then dispersed ultrasonically with 10mL of anhydrous ethanol and 2g of aluminum isopropoxide. 1mL of deionized water was added, and the mixture was reacted for 12h. The sol was sprayed onto a substrate coating, dried at room temperature, and then calcined in a muffle furnace at 500℃ for 4h to remove the polyethylene glycol, yielding an alumina-coated modified hollow silica film.

[0063] S6 was then sprayed twice alternately with a silica-alumina-titanium oxide composite sol and alumina-coated modified hollow silica sol. The thicknesses of each film layer were 121 nm, 165 nm, 10 nm, 340 nm, 177 nm, and 306 nm, respectively.

[0064] S7 immerses the substrate coating in an ethanol solution containing 0.01M isostearic acid for 24 hours to modify the coating for hydrophobicity. Then, it is placed in an oven and dried at 60°C for 12 hours to obtain the target coating.

[0065] Example 3

[0066] S1. Add 2g TEOS to 1mL deionized water and 4mL ethanol, add hydrochloric acid dropwise until the pH is 2.5, stir for 20min and let stand for 12h to obtain silica sol.

[0067] S2 Weigh 2.4g Al(Cl)3·6H2O and dissolve it in 10mL ethanol. After complete dissolution, add 5mL deionized water and 0.9g ethyl acetoacetate. Stir at room temperature for 1h to obtain alumina sol.

[0068] S3 mixes 3.4g tetrabutyl titanate (340g / mol), 0.9g ethyl acetoacetate and 12ml ethanol, adds dilute hydrochloric acid and stirs vigorously for 1h to carry out hydrolysis and condensation reaction, and lets stand for 1h to obtain titanium dioxide sol.

[0069] S4 mixes the three sols in a Si:Al:Ti molar ratio of 4:1:1 for 1 hour, deposits the mixed gel on a clean glass substrate by spraying, dries it in an oven at 50°C for 12 hours, and then sintersects it at 550°C for 1 hour to obtain a silicon oxide-alumina-titanium oxide film.

[0070] S5 dissolves 5g of polyethylene glycol (molecular weight 2000) in 50mL of an ethanol-water mixture (ethanol to water volume ratio 4:1), adds 4.5mL of ammonia (25% by mass), stirs for 30min, then slowly adds 5mL of TEOS, continues stirring for 5min, and allows to stand for 16h. The gel is separated by filtration, washed three times with ethanol, and centrifuged. Half of the core-shell structured silica precipitate is added to 10mL of anhydrous ethanol and 2g of aluminum isopropoxide, ultrasonically dispersed, and reacted with 1mL of deionized water for 12h. A portion of the sol is sprayed onto a substrate, dried at room temperature, and calcined in a muffle furnace at 500℃ for 4h to remove the polyethylene glycol, yielding an alumina-coated modified hollow silica coating.

[0071] S6 added 2g of tetrabutyl titanate and 12ml of ethanol to the remaining core-shell structured silica precipitate and ultrasonically dispersed it. After adding dilute hydrochloric acid, the mixture was stirred vigorously for 1 hour. It was then sprayed onto the substrate coating, dried at room temperature, and calcined in a muffle furnace at 500℃ for 4 hours to remove polyethylene glycol, thus obtaining a titanium dioxide-coated modified hollow silica film.

[0072] S7 was prepared by sequentially spraying a silicon oxide-alumina-titanium oxide film, a titanium oxide-coated modified hollow silica film, a silicon oxide-alumina-titanium oxide film, and an alumina-coated modified hollow silica film, with thicknesses of 149 nm, 146 nm, 18 nm, and 136 nm, respectively.

[0073] S8 involves immersing the substrate coating in an ethanol solution containing 0.01M isostearic acid for 24 hours to modify the coating for hydrophobicity. The coating is then placed in an oven and dried at 60°C for 12 hours to obtain the target coating.

[0074] Example 4

[0075] The only difference between this embodiment and Embodiment 2 is that the oxide precursor aluminum isopropoxide of S5 is replaced with tetrabutyl titanate, resulting in a titanium dioxide-encapsulated modified hollow silica coating.

[0076] S6 was then sprayed twice with a silica-alumina-titanium oxide composite sol and a titanium oxide-coated modified hollow silica sol. The thicknesses of each film layer were 121 nm, 148 nm, 10 nm, 126 nm, 15 nm, and 284 nm, respectively.

[0077] S7 The substrate coating was immersed in an ethanol solution containing 0.01M isostearic acid for 24 hours to modify the coating to be hydrophobic. Then it was placed in an oven and dried at 60°C for 12 hours to obtain the target coating.

[0078] Example 5

[0079] The difference between Example 1 and Example 2 is that S6 is omitted, resulting in a silicon oxide-alumina-titanium oxide composite film layer and an alumina-encapsulated modified hollow silicon dioxide film layer sequentially stacked on the substrate. The thicknesses of each film layer are 47 nm and 301 nm, respectively.

[0080] The substrate coating was immersed in an ethanol solution containing 0.01M stearic acid for 24 hours to modify its hydrophobicity. It was then placed in an oven and dried at 60°C for 12 hours to obtain the target coating.

[0081] Comparative Example 1

[0082] The difference between this comparative example and Example 1 is that isostearic acid was not used for modification, while the other steps and conditions are the same.

[0083] Comparative Example 2

[0084] The difference between this comparative example and Example 5 is that titanium dioxide sol, alumina sol, and silica sol were sprayed to prepare three-layer films, and an alumina-coated modified hollow silica film was then sprayed onto the three-layer films. After drying at room temperature, the films were calcined in a muffle furnace at 500°C for 4 hours. The thicknesses of each film were 76 nm, 81 nm, 81 nm, and 110 nm, respectively.

[0085] The cooled substrate coating was immersed in an ethanol solution containing 0.01M stearic acid for 24 hours to modify its hydrophobicity. It was then placed in an oven and dried at 60°C for 12 hours to obtain the target coating.

[0086] Comparative Example 3

[0087] The difference between this comparative example and Example 1 lies in the preparation of hollow silica. In this example, polyethylene glycol was not added, and TEOS was added to an ethanol-water-ammonia aqueous solution to obtain solid silica. The remaining steps and conditions are the same.

[0088] Comparative Example 4

[0089] The only difference between this comparative example and Example 1 is that the coatings were prepared by spraying in the following order: silicon oxide-alumina-titanium oxide film, silicon oxide-alumina-titanium oxide film, titanium oxide-coated modified hollow silica film, and alumina-coated modified hollow silica film. The thicknesses of each film were 149 nm, 18 nm, 146 nm, and 136 nm, respectively. All other steps and conditions were the same.

[0090] Comparative Example 5

[0091] Compared with Example 2, the difference in this comparative example is that after preparing the core-shell structured silica sol, it was not coated with alumina for modification, resulting in a hollow silica film.

[0092] S6 is then sprayed twice alternately with a silica-alumina-titanium oxide composite sol and a hollow silica sol. The thickness of each film layer is the same as in Example 2.

[0093] Comparative Example 6

[0094] The difference between this comparative example and Example 2 is that titanium dioxide sol is not added when preparing the silica-alumina-titanium dioxide composite sol, resulting in alumina-silica composite sol, which is then overlapped with alumina-encapsulated hollow silica to prepare a film layer, with the thickness of each film layer remaining unchanged.

[0095] The test results for properties such as light transmittance, initial water droplet angle, resistance to rubber friction, resistance to steel wool friction, resistance to chemical corrosion, and coefficient of dynamic friction of the substrate coating surface are shown in Table 1 below.

[0096] Transmittance test method: Transmittance is measured by a TH-110 transmittance haze meter. Place the coated substrate on the test platform, press the HOLD button on the instrument, and wait for the instrument to complete self-calibration before starting the test and recording the test results.

[0097] Hydrophobic angle test method: The static contact angle of the coating was measured using a JGW-360a contact angle meter. The test liquid volume was 2 μL, and the test environment was 24±1℃ and 45±1% relative humidity. Five points were measured for the water droplet contact angle, and the contact angles of the left and right sides of each droplet were measured, and the average value was taken.

[0098] Rubber abrasion resistance test method: The rubber abrasion resistance test is conducted by a ZJ-339-GSR abrasion tester. The coated substrate is fixed on the tester, the pressure is set to 1000g, the stroke is set to 40mm, and the speed is 40 cycles / min. After the test, the water droplet angle test result of the substrate is recorded.

[0099] Steel Wool Abrasion Resistance Test Method: The steel wool abrasion resistance test is conducted using a ZJ-339-GSR abrasion tester. The coated substrate is fixed on the tester, the rubber type is MUNBANGSAWOO, the pressure is set to 1000g, the stroke is set to 40mm, and the speed is 40 cycles / min. After the test, the water droplet angle test results of the substrate are recorded.

[0100] Dynamic friction coefficient test method: The dynamic friction coefficient of the substrate surface was measured using an MXD-02 friction coefficient meter with a load of 200g.

[0101] Relative permittivity test method: The relative permittivity of the sample is measured at 1 MHz according to the method of ASTM D150-22.

[0102]

[0103] In this invention, the average transmittance indicates the average light transmission effect over a wide spectral range of 180~1800nm ​​light wavelength. The higher the average transmittance, the better the light transmission effect.

[0104] As shown in Table 1, the high-hardness self-cleaning antireflective coatings prepared in Examples 1-5 all have a light transmittance higher than 98%, and exhibit good hydrophobicity, abrasion resistance, and high slip properties. Among them, the coating prepared in Example 1 has the best hydrophobicity, abrasion resistance, and slip properties.

[0105] The coating obtained in Comparative Example 1 had the worst hydrophobicity because the method did not use stearic acid for surface hydrophobic modification. Comparative Example 2 prepared coatings using silica, alumina, and titanium dioxide sols respectively. The transmittance was significantly lower than the example and lower than the blank glass, indicating that the composite coating prepared with these three materials had significantly better transmittance than the three-layer coatings prepared separately, and also better wear resistance. However, because titanium dioxide had the highest proportion, its relative permittivity was the highest. Comparative Example 3 used solid silica to prepare an alumina-modified silica coating. Although the wear resistance was better, the transmittance and smoothness of the coating were significantly lower than in Example 1. Comparative Example 4 prepared coatings in the order of high-refractive-index layer, high-refractive-index layer, low-refractive-index layer, and low-refractive-index layer. Its transmittance was lower than in Example 1. Comparative Example 5 did not perform encapsulation modification on the hollow silica, resulting in a significantly reduced wear resistance of the coating. The coating prepared in Comparative Example 6 without the addition of titanium oxide has a significantly lower relative dielectric constant than that in Example 2, and its transmittance also decreases to some extent. This indicates that the addition of titanium oxide can effectively improve the dielectric properties of the coating and has a synergistic effect on the overall antireflection effect across a wide spectral range of the coating.

[0106] This demonstrates that the coating obtained by the present invention through the alternating superposition of multiple layers of silicon oxide-alumina-titanium oxide and oxide-modified hollow silicon dioxide coatings has excellent broad-spectrum transmittance, high hardness, good hydrophobicity and dielectric properties.

Claims

1. A high-hardness self-cleaning anti-reflective coating, characterized in that: This includes anti-reflective coatings and hydrophobic modified coatings on their surfaces; The anti-reflective coating comprises at least one periodic film layer consisting of alternating layers of low-refractive-index and high-refractive-index films. The low refractive index film is an oxide-encapsulated modified hollow silicon dioxide film; The high refractive index film is a silicon oxide-alumina oxide-titanium oxide composite film.

2. The high-hardness self-cleaning anti-reflective coating according to claim 1, characterized in that: The total number of anti-reflective coating layers is 2 to 10, and the thickness of a single layer is 9 to 340 nm.

3. A high-hardness self-cleaning anti-reflective coating according to claim 1 or 2, characterized in that: The high-hardness self-cleaning antireflective coating has a silicon oxide-alumina-titanium oxide composite film layer in contact with the substrate, and an oxide-encapsulated and modified hollow silicon dioxide film layer in contact with the hydrophobic modified coating.

4. The high-hardness self-cleaning anti-reflective coating according to claim 3, characterized in that: The preparation process of the oxide-encapsulated modified hollow silica film is as follows: polyethylene glycol as a template agent and tetraethyl orthosilicate are reacted in an organic solvent-water mixture under alkaline conditions to obtain a core-shell structured silica sol; an oxide precursor is added to the core-shell structured silica sol for modification to obtain an oxide-encapsulated modified silica sol, which is then calcined to obtain the final product.

5. The high-hardness self-cleaning anti-reflective coating according to claim 4, characterized in that: The oxide precursor is at least one of a metal salt and a metal alkoxide, wherein the metal is at least one of aluminum, titanium, antimony, tantalum, lanthanum, niobium and zirconium; The oxide in the oxide-encapsulated modified hollow silica film is at least one of aluminum oxide, titanium dioxide, antimony oxide, tantalum pentoxide, lanthanum titanate, niobium pentoxide, and zirconium dioxide. The hollow silica particles in the oxide-coated modified hollow silica film have a particle size of 50~400nm.

6. A method for preparing a high-hardness self-cleaning antireflective coating as described in any one of claims 1 to 5, characterized in that: Includes the following steps: S1 first coats a silica-alumina-titanium oxide composite sol on the substrate surface, and after drying and sintering, a high refractive index film layer is generated. Then, an oxide-encapsulated modified silica sol is coated, and after drying and calcination, a low refractive index film layer is generated. Thus, a periodic film layer composed of alternating low refractive index film layers and high refractive index film layers is generated on the substrate surface. or; On the substrate surface, a silica-alumina-titanium oxide composite sol is first coated, and after drying and sintering, a high refractive index film layer is generated. Then, an oxide-encapsulated modified silica sol is coated, and after drying and calcination, a low refractive index film layer is generated. The above operation is repeated several times to generate multiple periodic film layers on the substrate surface, which are composed of alternating low refractive index film layers and multiple high refractive index film layers. S2 is obtained by surface hydrophobic modification of the periodic film layer formed on the substrate surface in S1.

7. The method for preparing a high-hardness self-cleaning antireflective coating according to claim 6, characterized in that: The silica-alumina-titanium oxide composite sol is obtained by mixing silica sol, alumina sol and titanium oxide sol, wherein the silica sol, alumina sol and titanium oxide sol are in the molar ratio of Si, Al and Ti as (4~10):1:(0.1~1).

8. The method for preparing a high-hardness self-cleaning antireflective coating according to claim 7, characterized in that: The preparation process of the silica sol is as follows: tetraethyl orthosilicate is stirred and allowed to stand in an organic-water two-phase solvent in the presence of acid catalyst A. The alumina sol is prepared by stirring aluminum salt and chelating agent A in an organic-water two-phase solvent. The preparation process of the titanium dioxide sol is as follows: titanium alkoxide and chelating agent B are added to an alcohol solvent and stirred evenly to obtain mixture 1; acid catalyst B is added to an organic-water two-phase solvent and stirred to obtain a dilute acid solution, which is then added to mixture 1 and stirred to obtain the final product.

9. A method for preparing a high-hardness self-cleaning antireflective coating according to claim 7 or 8, characterized in that: The surface hydrophobic modification is achieved by impregnation with a solution containing at least one hydrophobic modifier selected from stearic acid, isostearic acid and stearate.

10. The method for preparing a high-hardness self-cleaning antireflective coating according to claim 9, characterized in that: The concentration of the hydrophobic modifier in the solution is 0.01~0.5M, and the immersion treatment time is 1~4 days.

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