A method for preparing corrosion-resistant and UV-resistant SiO2 nano-antireflective thin films

Abstract

The application discloses a preparation method of a SiO2 nano anti-reflection film with corrosion resistance and ultraviolet radiation resistance, characterized in that the sol-gel process adopts isobutyl triethoxysilane (IBTS) which is a silane with aging resistance and corrosion resistance. First, silicate, IBTS and deionized water are hydrolyzed in an organic solvent under an acidic condition at a certain proportion, an organic pore-forming agent is added after reflux, and a sol is obtained by dissolution; the sol is coated on the surface of an object by using a spin coating or a pulling process, and a SiO2 gel thin film is obtained after drying, and the SiO2 nano anti-reflection film is obtained after heat treatment at 100-400 DEG C. The thin film improves the transmittance of photovoltaic glass by 4-6 percentage points; after irradiation of a 250W ultraviolet lamp for 100 hours, the transmittance only decreases by 0.45 percentage points, the hardness and the adhesion do not attenuate; after immersion in a 0.5mol / L hydrochloric acid solution for 100 hours, the hardness decreases to 8H, the adhesion decreases to level 1, and the light transmittance increases by 1.0 percentage points.

Description

Technical Field

[0001] This invention belongs to the field of optical antireflective thin film material preparation technology, specifically relating to a method for preparing a high-performance corrosion-resistant and UV-irradiation-resistant SiO2 nano-antireflective thin film. Background Technology

[0002] Antireflective coatings are widely used in the cover glass of solar cells to effectively reduce sunlight reflection loss and improve photoelectric conversion efficiency. Commonly used materials for antireflective coatings include SiO2, TiO2, and MgF2. Among them, the sol-gel method for preparing SiO2 porous antireflective coatings allows for better matching of the refractive index with the cover glass by adjusting the porosity, thus achieving high antireflection performance. The sol-gel method for preparing antireflective coatings is divided into alkaline catalysis and acid catalysis.

[0003] SiO2 nanofilms prepared on glass substrates using alkaline catalysis typically exhibit high porosity and good antireflection effects, but their adhesion and surface hardness are relatively low, making them unsuitable for the harsh working environment of photovoltaic glass covers. Patent application CN105399340A discloses a method for preparing antireflection films using trimethylchlorosilane-modified SiO2, synthesizing SiO2 sol under alkaline catalysis to prepare the antireflection film. Similar technologies include authorized patent CN108761581B and patent applications CN110564187A, CN106477909A, and CN104230178A. This alkaline-catalyzed SiO2 antireflective film is composed of loosely packed solid SiO2 nanoparticles, with numerous open pores between the particles [WANG Y, NIE L, LIU J. Inorganic Chemistry, 2020, 5(53) 10220-10227.], and the particle surface contains abundant hydroxyl groups [Sui Xueye, Liu Shiquan, Cheng Xin. China Powder Technology, 2006, (03): 35-39.]. This polar porous structure readily adsorbs polar pollutants from the environment, leading to a decline in the optical performance of the antireflective film. More importantly, the film generally exhibits poor mechanical properties, with a hardness below 2H, making it easily damaged with a light touch, thus hindering its application as an antireflective film on the surface of solar cell glass covers.

[0004] Antireflective films of SiO2 nanoparticles prepared by acid catalysis on glass substrates generally exhibit low porosity and high adhesion and surface hardness. However, a drawback is that monolayer acid-catalyzed antireflective films have a high refractive index, which is too close to the refractive index n0 (1.42–1.55) of silicate glasses such as photovoltaic glasses, far from the ideal refractive index. The antireflection effect is quite limited. The SiO2 molecules in the micro / nanoparticles prepared under acid catalysis are chain-like. After forming a thin film, the exposed polar hydroxyl groups on the molecules form silicon-oxygen bonds with the glass surface, exhibiting excellent adhesion. Furthermore, by controlling the composition and ratio of the catalyst, the film can achieve high hardness. Patent applications CN105776883A and CN102617045A report similar results, but neither addresses the characterization of film adhesion and hardness. Moreover, the dense film material does not significantly reduce the refractive index, indicating that the antireflection effect of acid-catalyzed SiO2 is far from ideal.

[0005] Mesoporous antireflective films are formed by creating ordered pores on the surface of acid-catalyzed thin films, significantly reducing the refractive index of the film and improving the antireflective effect of acid-catalyzed SiO2 films. One method of preparation is to introduce a surfactant template, induce pore formation through evaporation, and then remove the template agent by high-temperature calcination after film formation to obtain a mesoporous SiO2 film. This film has a low refractive index and also possesses good mechanical properties. Patent application 202010264897 discloses a method for preparing mesoporous SiO2 films, in which a pore-forming agent is dispersed in an acid-catalyzed sol, sealed and aged to obtain a mesoporous acid-catalyzed sol; the sol is then stretched into a film and heat-treated to obtain a mesoporous antireflective film. Ye et al. used tetraethyl orthosilicate (TEOS) as a precursor and hexadecyltrimethylammonium bromide (CTAB) as a template to prepare an antireflective film with a weighted average transmittance of up to 98.7%; this film also has excellent mechanical abrasion resistance, and can withstand 20 repeated rubbings with a paper towel. [Ye L, Zhang S, Wang Q, et al. RSC Advances, 2014, 4(67): 35818]. Xu et al. prepared a stain-resistant SiO2 mesoporous antireflective film with good optical properties on a quartz glass substrate using TEOS as a precursor and nonionic triblock copolymer surfactant (F127) as a template agent. The film can increase the visible light transmittance of the quartz sheet by 5.3 percentage points. Furthermore, the surface treatment with FAS-17 can reduce the pore size and make it stain-resistant. [Sun J, Zhang Q, Ding R, et al. Physical Chemistry Chemical Physics, 2014, 16(31): 16684-16693].

[0006] However, if the surface pore size of the mesoporous membrane is too large, the film will absorb moisture from the air during service, severely reducing the transmittance of the antireflective film, damaging the antireflective film structure, and potentially further corroding the substrate, thus significantly shortening the service life of the antireflective film. Furthermore, because a large amount of organosiloxanes and organic modifiers are used in the sol-gel method for preparing SiO2, the prepared mesoporous SiO2 antireflective film contains a considerable amount of organic matter that cannot be completely removed by high temperatures. When the pore diameter on the surface of the antireflective film exceeds 500 nm, ultraviolet light will penetrate into the film (patent application: 202111125468.X), causing organic matter to age and become damaged, resulting in a decrease in the transmittance of the antireflective film.

[0007] In summary, acid-catalyzed mesoporous antireflective films have a relatively simple structure, and their refractive index can be altered by adjusting the porosity. They exhibit high light transmittance, along with strong adhesion and high hardness. However, issues such as capillary adsorption of water vapor and poor resistance to ultraviolet radiation in mesoporous films need to be properly addressed to meet the requirements of long-term, high-efficiency operation of solar cells in harsh outdoor environments. Summary of the Invention

[0008] The purpose of this invention is to address the problems of water vapor adsorption on the surface of acid-catalyzed mesoporous SiO2 nanoparticle antireflective films and the damage to internal organic matter caused by ultraviolet radiation. It provides an antireflective film resistant to acid corrosion and ultraviolet radiation, and its preparation method. While ensuring a significant antireflective effect, it significantly improves the film's adhesion, surface hardness, resistance to ultraviolet radiation, and resistance to acid corrosion. The method is a sol-gel method, including sol preparation, film coating, drying, and heat treatment. Its key feature is the use of isobutyltriethoxysilane (IBTS), which possesses excellent corrosion resistance and ultraviolet resistance, as a co-hydrolysis reactant. First, silicate ester, IBT, and deionized water are co-hydrolyzed in an organic solvent under acidic conditions, and after reflux, a sol is obtained. An organic porogen, polyethylene glycol monomethyl ether (mPEG), is added to the sol and fully dissolved. The sol is then coated onto a transparent substrate, dried, and then heat-treated to obtain a corrosion-resistant and ultraviolet-radiation-resistant SiO2 nanoparticle antireflective film.

[0009] This invention specifically consists of the following steps:

[0010] (1) Silicate, IBTS, and deionized water are co-hydrolyzed in an organic solvent under acidic conditions in a certain proportion. After reflux, an organic porogen is added and fully dissolved to obtain a sol-colloid. The volume ratio of silicate to IBTS is 1:0.1 to 1:1; the volume ratio of silicate to deionized water is 1:0.1 to 1:0.5; the volume ratio of silicate to organic solvent is 1:10 to 1:20; the mass ratio of organic porogen to sol is 1:20 to 1:50; and the hydrolysis reaction temperature is 25 to 100℃.

[0011] (2) Using the sol colloid obtained in (1), the sol colloid is uniformly coated on the surface of a transparent substrate by dip-coating, spin coating or scraping. After drying, a SiO2 gel film is obtained. The pore-forming agent is removed by heat treatment in a muffle furnace to obtain a porous SiO2 film. The drying temperature is 80℃ and the heat treatment temperature is 100℃~500℃.

[0012] Preferably, in step (1), the silicate ester is tetramethyl silicate, tetraethyl silicate, n-propyl silicate, or tetrabutyl silicate;

[0013] Preferably, the organic porogen in step (1) is one or more of polyethylene glycol monomethyl ether (mPEG) 350, mPEG 750, mPEG 1000, and mPEG 1900;

[0014] Preferably, the acid used to adjust the acidity of the organic solvent in step (1) is one or more of hydrochloric acid, acetic acid, and nitric acid;

[0015] Preferably, the organic solvent in step (1) is one or more of ethanol, methanol, propanol, and ethylene glycol.

[0016] The beneficial effects of this invention are as follows: This invention effectively increases the UV resistance and acid corrosion resistance of SiO2 thin films prepared by the sol-gel method, making them suitable for outdoor use. The thin film prepared by this invention is composed of SiO2 nanoparticles, with uniform and fine pores between the nanoparticles, the pore size of which is 10nm to 50nm. The thin film adheres to the surface of photovoltaic glass, increasing the transmittance of the glass in the 380-1100nm range by 4-6 percentage points. The pencil hardness of the thin film reaches the highest grade 9H or above (GB / T1727-92), and the adhesion reaches the highest grade 0 (GB / T 1727-1992). After 100 hours of irradiation with a 250W ultraviolet lamp, the transmittance only decreases by 0.45 percentage points, but the hardness and adhesion remain unchanged. After immersion in a 0.5mol / L hydrochloric acid solution for 100 hours, the hardness decreases to 8H, and the adhesion decreases to grade 1, but the transmittance increases by 1.0 percentage point. Detailed Implementation

[0017] The present invention will be further illustrated below through specific implementation examples. These examples are descriptive and not limiting, and cannot limit the scope of protection of the present invention.

[0018] Example 1:

[0019] A corrosion-resistant, UV-resistant, and anti-reflective nanofilm and its preparation method are disclosed, comprising the following steps: Tetraethyl orthosilicate, isobutyltriethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a volume ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A certain amount of mPEG is then added to the sol to obtain a solution for preparing an anti-reflective coating. This solution is coated onto a photovoltaic white glass sheet using an dip-coating method at a speed of 500 μm / min. After the film material is dried, it is heated at 400℃ for 1 hour to obtain the anti-reflective film.

[0020] Example 2:

[0021] A corrosion-resistant, UV-resistant, and anti-reflective nanofilm and its preparation method are disclosed, comprising the following steps: tetrapropyl orthosilicate, isobutyltriethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a molar ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 3 using hydrochloric acid, and the mixture is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A measured amount of mPEG is then added to the solution to obtain a solution for preparing an anti-reflective coating. This solution is coated onto a photovoltaic white glass sheet using a dip-coating method at a speed of 400 μm / min. After the film material is dried, it is heated at 400℃ for 1 hour to obtain the anti-reflective film.

[0022] Example 3:

[0023] A corrosion-resistant, UV-resistant, and anti-reflective nanofilm and its preparation method are disclosed, comprising the following steps: Tetrabutyl orthosilicate, isobutyltriethoxysilane, and deionized water are co-hydrolyzed in anhydrous ethanol at a molar ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. This solution is then used to prepare the anti-reflective coating. The solution is coated onto a photovoltaic white glass substrate using a dip-coating method at a speed of 200 μm / min, and heated at 400℃ for 1 hour to obtain the anti-reflective film.

[0024] Example 4:

[0025] A corrosion-resistant, UV-resistant, and anti-reflective nanofilm and its preparation method include the following steps: Tetraethyl orthosilicate, isobutyltriethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a volume ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A certain amount of mPEG is then added to the sol to obtain a solution for preparing an anti-reflective coating. This solution is coated onto a photovoltaic white glass sheet using a coating method. After the film material is dried, it is heated at 400℃ for 1 hour to obtain the anti-reflective film.

[0026] Example 5:

[0027] A corrosion-resistant, UV-resistant, and anti-reflective nanofilm and its preparation method are disclosed, comprising the following steps: Tetraethyl orthosilicate, isobutyltriethoxysilane, and deionized water are hydrolyzed together in anhydrous ethanol at a volume ratio of 1:1:0.3 for 2 hours. The pH of the solution is adjusted to 5 using hydrochloric acid, and the solution is refluxed for 2 hours to obtain a stable modified nano-SiO2 colloidal solution. A certain amount of mPEG is then added to the sol to obtain a solution for preparing an anti-reflective coating. This solution is then spin-coated onto a photovoltaic white glass substrate at a speed of 800 rpm. After the film material dries, it is heated at 400°C for 1 hour to obtain the anti-reflective film. Attached Figure Description

[0028] Figure 1 The scanning electron microscope used in this invention to examine SiO2, with a magnification of 40,000, demonstrates that the film surface has uniform pores, which is beneficial for reducing the refractive index of the film.

[0029] Figure 2 The comparison of transmittance between the ultra-clear glass coated with an anti-reflective film and the uncoated glass selected in this invention shows that the coating has good anti-reflective properties.

[0030] Figure 3 The image shows the anti-reflective coating on the glass selected in this invention after 100 hours of UV irradiation, tested with a cross-cut adhesion tester, and then peeled off with 3M tape. It can be seen that there was no significant peeling after the tape was removed.

[0031] Figure 4 The image shows a pencil hardness marking on the glass coated with an anti-reflective film selected in this invention after 100 hours of ultraviolet light irradiation. The pencil used was 9H, and it can be seen that sufficient hardness has been achieved.

[0032] Figure 5 The image shows the glass coated with an anti-reflective film selected in this invention after being immersed in a 0.5 mol / L hydrochloric acid solution for 100 hours, tested with a cross-cut adhesion tester, and then peeled off with 3M tape. It can be seen that there was no significant peeling after the tape was removed.

[0033] Figure 6 The image shows a pencil hardness marking on the glass coated with an antireflective film selected in this invention after being immersed in a 0.5 mol / L hydrochloric acid solution for 100 hours. The pencil used was an 8H, and it can be seen that sufficient hardness has been achieved.

Claims

1. A method for preparing a corrosion-resistant and UV-irradiation-resistant SiO2 nano-antireflective film, the method being a sol-gel method, comprising sol preparation, thin film coating, drying, and heat treatment, characterized in that: Isobutyltriethoxysilane (IBTS), which has excellent corrosion resistance and UV resistance, was used as a common hydrolysis reactant. First, silicate ester, IBTS, and deionized water were hydrolyzed in an organic solvent under acidic conditions in a certain ratio. After reflux, a sol was obtained. An organic porogen, polyethylene glycol monomethyl ether (mPEG), was added to the sol and fully dissolved. The sol was then coated onto a transparent substrate, dried, and then heat-treated to obtain a corrosion-resistant and UV-resistant SiO2 nano-antireflective film.

2. The method for preparing the corrosion-resistant and UV-resistant antireflective film according to claim 1, characterized in that: The silicate ester is tetramethyl silicate, tetraethyl silicate, n-propyl silicate, or tetrabutyl silicate; the organic solvent is one or more of ethanol, methanol, and propanol; the acid used to regulate acidity is one or more of hydrochloric acid, acetic acid, and nitric acid; and the organic porogen, polyethylene glycol monomethyl ether, is one or more of mPEG 350, mPEG 750, mPEG 1000, and mPEG 1900.

3. The method for preparing the corrosion-resistant and UV-resistant antireflective film according to claim 1, characterized in that: The volume ratio of the silicate ester to IBTS is 1:0.1 to 1:1; the volume ratio of the silicate ester to deionized water is 1:0.1 to 1:0.5; the volume ratio of the silicate ester to the organic solvent is 1:10 to 1:20; and the mass ratio of the organic porogen to the sol is 1:20 to 1:

50.

4. The method for preparing the corrosion-resistant and UV-resistant antireflective film according to claim 1, characterized in that: The hydrolysis reaction temperature is 25–100℃, and the hydrolysis reaction time is 1–10h; the reflux temperature is 50–100℃, and the reflux time is 1–12h; the film heat treatment temperature is 100–550℃.

5. The method for preparing the corrosion-resistant and UV-resistant antireflective film according to claim 1, characterized in that: Methods for applying sol to transparent substrates include, but are not limited to, dip coating, spin coating, blade coating, and spray coating.

6. The method for preparing the corrosion-resistant and UV-resistant antireflective film according to claim 1, characterized in that: The thin film prepared by this method, when the transparent substrate is photovoltaic white glass, increases the light transmittance of the glass in the 380-1100nm range by 4-6 percentage points; the pencil hardness of the film reaches the highest grade 9H or above (GB / T1727-92), and the adhesion reaches the highest grade 0 or above (GB / T 1727-1992); after irradiation with a 250W ultraviolet lamp for 100h, the light transmittance of the coated glass only decreased by 0.45 percentage points, and the hardness and adhesion of the film did not decrease; after immersing the coated glass in a 0.5mol / L hydrochloric acid solution for 100h, the film hardness decreased to 8H, and the adhesion decreased to grade 1, but the light transmittance actually increased by 1.0 percentage point.

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