CN117025076B

CN117025076B - Self-cleaning anti-reflection nano film and preparation method thereof

Info

Publication number: CN117025076B
Application number: CN202311164037.3A
Authority: CN
Inventors: 汪怀远; 彭建文; 叶鹏; 徐飞; 王瑞涛; 朱艳吉; 耿昊雷; 包迪; 白子恒; 裴鲁超
Original assignee: Tianjin University
Current assignee: Tianjin University
Priority date: 2023-09-11
Filing date: 2023-09-11
Publication date: 2024-01-30
Anticipated expiration: 2043-09-11
Also published as: CN117025076A

Abstract

The application discloses a self-cleaning anti-reflection nano film and a preparation method thereof, and the self-cleaning anti-reflection nano film is formed by coating and curing a nano film crosslinking prepolymer, wherein the nano film crosslinking prepolymer is a crosslinking reactant of a silicon fluoropolymer and fluorine modified nano silicon dioxide; the silicon fluorine polymer is a mixture of fluorocarbon resin and organosilicon modified isocyanate crosslinking agent; the fluorine modified nano silicon dioxide is cluster nano silicon dioxide which is synthesized by a sol-gel method through alkali and acid catalysis and is modified by in-situ fluorination and has a silicon dioxide spherical particle inner core; the problem that the existing photovoltaic panel coating film cannot simultaneously achieve self-cleaning, anti-reflection and weather resistance is effectively solved.

Description

Self-cleaning anti-reflection nano film and preparation method thereof

Technical Field

The present disclosure relates to an anti-reflection coating film for surfaces of optical equipment such as solar photovoltaic panels, and in particular relates to a coating film which is self-cleaning, weather resistance and anti-reflection and a preparation method thereof.

Background

The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.

Among various practical applications of renewable energy sources, solar photovoltaic cells have become a major way of utilizing solar energy due to their advantages of high efficiency, safety, environmental friendliness, and the like. Along with the diversification of the installation area of the photovoltaic module, the photovoltaic module is not only required to be subjected to the tests of high/low temperature, high humidity, drought, ultraviolet radiation, acid rain and salt fog, but also is required to be subjected to the deposition problem of stains such as straight dust, sandy soil and the like. In recent years, in order to alleviate and solve the problems of dust and various pollutants deposition and improvement of the light transmittance and the power generation efficiency of the photovoltaic module in the operation process, researchers have carried out various works such as:

chinese patent CN101805135B realizes double-layer coating of high refractive index metal oxide/low refractive index silicon dioxide on the surface of glass by using a sol-gel method, and compared with a single-layer antireflection film, the double-layer coating can realize higher transmittance in a visible light wave band and can improve the power generation efficiency of a photovoltaic module. However, the double-layer coating film does not show self-cleaning and lyophobic properties, and does not meet the self-cleaning requirement of the photovoltaic module under the actual working condition.

Chinese patent CN102531406B discloses that the light transmittance of the glass in the visible light wavelength range can be improved by 2.5% by coating anti-reflection coating liquid containing metal oxides such as silicon dioxide, titanium dioxide, zirconium dioxide, cerium dioxide and the like, a stabilizer and a surface modifier on the surface of the photovoltaic glass in a roller coating manner, and performing heat treatment and tempering to obtain the anti-reflection coating on the surface of the glass. However, the self-cleaning performance of the coating film is limited, and particularly, only hydrophobicity can be achieved, but liquid repellency to an oily medium and an organic solvent cannot be achieved. In addition, the weatherability of the antireflective coating is unknown.

Chinese patent CN113088190B, a fluorine-containing organopolysiloxane coating film having superhydrophobic and self-cleaning properties is prepared by directly mixing a fluorine-containing siloxane precursor and a siloxane prepolymer, and hydrolyzing/condensing ethoxy or methoxy groups in the precursor and the prepolymer under alkaline conditions. Although the polymer coating film is excellent in hydrophobicity and self-cleaning property, the polymer coating film does not exhibit anti-reflection property, and is difficult to use in optical equipment such as photovoltaic glass.

In view of the above, the existing self-cleaning and anti-reflective coating films for photovoltaic panels still have a number of disadvantages. First, most of the anti-reflective coating films on the market facing optical equipment are composed of low refractive index inorganic nanoparticles (e.g., silica), which are easily contaminated in outdoor environments, resulting in loss of anti-reflective properties. In addition, with the development of super-wetted surface science, various super-hydrophilic or super-hydrophobic anti-reflective coating films have been developed in recent years, but all have fine micro/nano structures, which make them difficult to withstand outdoor long-term wind and sand erosion, and oily media and organic solvent media having low surface tension do not have liquid repellency and are easily contaminated. Finally, the existing self-cleaning anti-reflection coating film has poor weather resistance and cannot meet the requirement of long-term stable operation of the photovoltaic module. Therefore, there is still a need to develop a multifunctional, durable photovoltaic panel coating film that can achieve both self-cleaning, anti-reflection and total lyophobic properties.

It should be noted that the information disclosed in the foregoing background section is only for enhancing understanding of the background of the present disclosure, and thus may contain information that does not constitute prior art.

Disclosure of Invention

In view of the above, the present disclosure provides a self-cleaning anti-reflection nano film, which solves the problem that the existing photovoltaic panel coating film cannot simultaneously achieve self-cleaning, anti-reflection and weather resistance.

In addition, the disclosure also provides a preparation method of the self-cleaning anti-reflection nano film.

In a first aspect, the self-cleaning anti-reflective nanomembrane is formed by coating and curing a nanomembrane cross-linked prepolymer, wherein:

the nano-film crosslinking prepolymer is a crosslinking reactant of a silicon fluoropolymer and fluorine modified nano-silicon dioxide;

the silicon fluorine polymer is a mixture of fluorocarbon resin and organosilicon modified isocyanate crosslinking agent;

the fluorine modified nano silicon dioxide is cluster nano silicon dioxide which is synthesized by a sol-gel method through alkali and acid catalysis and is fluorinated and modified in situ and provided with a silicon dioxide spherical particle inner core.

In a second aspect, the method for preparing the self-cleaning anti-reflection nano film according to the first aspect includes:

obtaining fluorocarbon resin containing hydroxyl and carboxyl groups;

after adding organosilicon into a mixture containing isocyanate, a catalyst and a solvent, carrying out reaction under the nitrogen atmosphere and in a stirring state to obtain organosilicon modified isocyanate;

according to the fluorocarbon resin: the mass ratio of the organosilicon modified isocyanate is 3-10:1, mixing the two materials in proportion to obtain a silicon fluorine polymer;

and mixing the silicon fluorine polymer with modified nano silicon dioxide to obtain the nano film cross-linked prepolymer.

In the present disclosure and possible embodiments, the fluorocarbon resin includes chlorotrifluoroethylene and alkyl vinyl ester copolymer resin, tetrafluoroethylene and alkyl vinyl ether copolymer resin, and chlorotrifluoroethylene and alkyl vinyl ether copolymer resin; and/or the number of the groups of groups,

the organosilicon comprises reactive polydimethylsiloxane with hydroxyl or amino at a single end, double ends or side chains; and/or the number of the groups of groups,

the isocyanate is one or more of toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dimethylbiphenyl diisocyanate, polymethylene polyphenyl isocyanate, hexamethylene diisocyanate (or a terpolymer thereof), trimethyl hexamethylene diisocyanate, isophorone diisocyanate, tetramethyl benzyl methylene diisocyanate, methylcyclohexyl isocyanate and cyclohexane dimethylene diisocyanate.

In the present disclosure and possible embodiments, the molecular weight of the silicone is mn=500-20000 g/mol; and/or the number of the groups of groups,

the catalyst is at least one of dibutyl tin dilaurate and stannous isooctanoate; and/or the number of the groups of groups,

the solvent is at least one of acetone, butanone, ethylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol dimethyl ether, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether.

In the present disclosure and possible embodiments, a method for preparing a silicone modified isocyanate comprises:

taking organic silicon accounting for 0.5-20.0% of the total mass of the fluorocarbon resin and the isocyanate, adding the organic silicon into the isocyanate crosslinking agent, the catalyst and the solvent, wherein the dosage of the catalyst is 0.5-3.0% of the total solid mass; and under the nitrogen atmosphere and in a stirring state, reacting at the constant temperature of 60-90 ℃ for 1-12 h to obtain the organosilicon isocyanate crosslinking agent.

In the present disclosure and possible embodiments, the synthesis method of fluorine modified nano-silica includes:

synthesizing alkali-catalyzed silica sol by alkali catalysis by adopting the sol-gel method, and thermally treating the alkali-catalyzed silica sol to obtain concentrated silica sol; and adding the concentrated silica sol and the fluorinated modifier into a reaction solution for acid-catalyzed synthesis of the silica sol, and carrying out acid-catalyzed synthesis reaction to obtain the fluorine modified nano-silica.

In the present disclosure and possible embodiments, the base catalyst for base catalysis is at least one of ammonia water, sodium hydroxide, and potassium hydroxide; and/or the number of the groups of groups,

the acid catalyst for acid catalysis is at least one of hydrochloric acid, sulfuric acid, nitric acid and acetic acid; and/or the number of the groups of groups,

the fluorination modifier is at least one of 1H, 1H, 2H, 2H-perfluoro octyl trimethoxysilane, 1H, 2H, 2H-perfluoro octyl triethoxysilane, 1H, 2H, 2H-perfluoro decyl trimethoxysilane, 1H, 2H, 2H-perfluoro decyl triethoxysilane; and/or the number of the groups of groups,

the particle size of the cluster nano silicon dioxide is 10-500 nm.

In the present disclosure and possible embodiments, the method for synthesizing a concentrated silica sol includes: the base catalyst was added to the catalyst in the following 1: stirring and reacting the mixture of ethyl orthosilicate and absolute ethyl alcohol in a volume ratio of 10-50 at room temperature for 12-24 h to obtain alkali-catalyzed silica sol; thermally treating the base-catalyzed silica sol to remove the absolute ethanol and the base catalyst to obtain the concentrated silica sol; and/or the number of the groups of groups,

the acid catalyzed synthesis method comprises the following steps: according to the ethyl silicate, the water and the acid catalyst are 6-10:1-4: and (3) after mixing according to the volume ratio of 1, adding the absolute ethyl alcohol dispersion liquid of the concentrated silica sol, stirring at room temperature for reaction for 12-24 h, adding a fluorinated modifier into the reaction liquid, wherein the volume of the fluorinated modifier is 1-10% of the total volume of the system, and removing the solvent from the reaction product through rotary evaporation, reduced pressure distillation and vacuum drying to obtain the clustered nano silica.

In the present disclosure and possible embodiments, dispersing the fluorine modified nano-silica in a diluent to obtain a dispersion having a solids content of 5-50%;

according to fluorocarbon resin: the organosilicon modified isocyanate is 3-10:1 and diluting the mixture with the diluent to obtain a solution of the silicon fluorine polymer with the solid content of 20-50 percent;

and (3) dropwise adding the silicon dioxide dispersion into the silicon fluorine polymer solution under the conditions of ultrasonic treatment for 10-30 min and stirring for 10-60 min, and carrying out a crosslinking reaction to obtain the nano-film crosslinking prepolymer.

In the present disclosure and possible embodiments, the mass ratio of the silicon fluoropolymer solution to the dispersion is 0.07-0.6:1, a step of; and/or the number of the groups of groups,

the diluent is at least one of butyl acetate, propylene glycol methyl ether acetate and xylene; and/or the number of the groups of groups,

the curing is 24-48 h at room temperature or 1-12 h at 50-120 ℃; the thickness of the coated film is 100-900 nm.

The self-cleaning anti-reflection nano film disclosed by the invention comprises a nano film crosslinking prepolymer which is formed by the self-cleaning anti-reflection nano film, wherein the nano film crosslinking prepolymer contains a silicon-fluorine polymer and modified nano silicon dioxide, the silicon-fluorine polymer contains fluorocarbon resin and an organosilicon modified isocyanate crosslinking agent, so that isocyanate groups can be used for carrying out crosslinking reaction with branched hydroxyl/carboxyl groups of the fluorocarbon resin and hydroxyl groups on the surface of the nano silicon dioxide to obtain the nano film crosslinking prepolymer, and the nano film is further obtained by the crosslinking prepolymer; in the first aspect, because the modified nano silicon dioxide in the crosslinked prepolymer is a cluster material with a silicon dioxide spherical particle kernel, multiple refraction/reflection of incident light inside a coating film is increased, so that the anti-reflection performance of the nano coating film is enhanced, and because the nano silicon dioxide is subjected to fluorination modification, the nano coating film has low surface energy characteristic, and the self-cleaning performance of the anti-reflection nano film is further enhanced; in a second aspect, the high bond energy of the C-F bonds in the fluorocarbon resin and the Si-O-Si bonds in the silicone, together with the inorganic nanosilicon dioxide particles, enhance the weatherability of the nanomembrane to enable it to withstand thousands of hours of uv irradiation and wet heat damage; in the third aspect, through the organosilicon modified isocyanate, the organosilicon can endow the nano coating with certain full lyophobicity and self-cleaning property, and the refractive index matching of fluorocarbon resin and nano silicon dioxide particles is facilitated, so that the requirement of optical equipment on high light transmittance is further met; in addition, the nano coating film has a higher contact angle and an extremely low sliding angle for water, oil and organic solvents, various liquid drops can easily slide off the surface of the nano coating film, and dirt such as dust on the surface of the nano coating film can be taken away in the sliding process, so that high-efficiency self-cleaning is realized; in conclusion, the self-cleaning anti-reflection nano film disclosed by the invention can have self-cleaning, anti-reflection and weather resistance.

Drawings

The above and other objects, features and advantages of the present disclosure will become more apparent from the following description of embodiments thereof with reference to the accompanying drawings in which:

FIG. 1 is a graph showing the water contact angle results for the nanomembrane of comparative example 2;

FIG. 2 is a graph showing the transmittance results of the nanomembrane of comparative example 2;

FIG. 3 is a water contact angle result of the nanomembrane of comparative example 3;

FIG. 4 is a graph showing the transmittance results of the nanomembrane of comparative example 3;

FIG. 5 is a TEM image of clustered nano silica particles of example 1;

FIG. 6 is the water contact angle results for the nanomembrane surface of example 1;

fig. 7 is a light transmittance result of the nano-film of example 1;

FIG. 8 is a plot of short circuit current density versus voltage for a battery die, and after the photovoltaic cell has been covered with the nanofilm-coated ultrawhite glass of example 1, contaminated, and cleaned;

Detailed Description

The present disclosure is described below based on embodiments, but it is worth noting that the present disclosure is not limited to these embodiments. In the following detailed description of the present disclosure, certain specific details are set forth in detail. However, for portions not described in detail, those skilled in the art can also fully understand the present disclosure.

Meanwhile, unless the context clearly requires otherwise, throughout the description and the claims, the words "comprise", "comprising", and the like are to be construed in an inclusive sense as opposed to an exclusive or exhaustive sense; that is, it is the meaning of "including but not limited to".

In order to enable those skilled in the art to better understand the technical solutions of the present application, a detailed description of preferred embodiments of the present application is provided below by way of specific examples in conjunction with the accompanying drawings. In this application, all equipment and materials are commercially available, and the test methods and testing methods are conventional.

Fluorocarbon resins used in the examples described below were purchased from Daikin, japan.

Example 1

1. Preparation of nanomembrane crosslinked prepolymer

Step (1): adding 0.03. 0.03 g hydroxyl-terminated polydimethylsiloxane into a flask containing 0.4. 0.4 g hexamethylene diisocyanate trimer, 0.025. 0.025 g dibutyl tin dilaurate and 1. 1 g propylene glycol methyl ether, stirring under nitrogen atmosphere, keeping the temperature at 90 ℃, and reacting 1. 1h to obtain an organosilicon modified hexamethylene diisocyanate trimer; dissolving 4 g tetrafluoroethylene and alkyl vinyl ester copolymer resin and 0.4 g organosilicon modified hexamethylene diisocyanate trimer in 5 g dimethylbenzene by ultrasonic treatment for 10 min and stirring for 30 min to obtain a silicon-fluorine polymer solution for later use;

step (2): mixing 2 mL tetraethoxysilane with 20 mL absolute ethyl alcohol, stirring for 5 min, adding 5 mL ammonia water solution, stirring at room temperature, and reacting 15 h to obtain base-catalyzed silica sol; heating the alkali-catalyzed silica sol, removing a solvent and an alkali catalyst, dispersing in 40 mL absolute ethyl alcohol again, continuously adding 2.4 mL tetraethoxysilane, 0.8 mL deionized water and 0.4 mL sulfuric acid, stirring at room temperature, reacting 12H, adding 0.45 mL of 1H, 2H, 2H-perfluoro decyl triethoxysilane, and continuously reacting 3H; finally removing the solvent by rotary evaporation to obtain cluster nano silicon dioxide;

step (3): dispersing 2 g cluster nano silicon dioxide in 20 g xylene, dropwise adding the mixture into the silicon-fluorine polymer solution, carrying out ultrasonic treatment for 10 min, and stirring and reacting for 30 min to obtain the nano film crosslinked prepolymer.

2. Preparation of self-cleaning anti-reflection nano film

1: fixing the ultra-white glass substrate on a pressing table, and rolling the nano-film crosslinked prepolymer on the surface of the substrate;

2: the above substrate coated with the nanofilm cross-linked prepolymer was placed in a forced air drying oven at 120 ℃ for heat treatment 2h to give a final cured nanofilm with a thickness of about 300 a nm a.

Example 2

1. Preparation of nanomembrane crosslinked prepolymer

Step (1): adding 0.8. 0.8 g amino-terminated polydimethylsiloxane into a flask containing 0.5 g isophorone diisocyanate, 0.01 g dibutyltin dilaurate and 1.5 g dipropylene glycol butyl ether, stirring under nitrogen atmosphere, maintaining the temperature at 60 ℃, and reacting 12 h to obtain organosilicon modified isophorone diisocyanate; 4 g trifluoro vinyl chloride and alkyl vinyl ester copolymer resin and 0.5 g organosilicon modified isophorone diisocyanate are dissolved in 5 g propylene glycol methyl ether acetate by ultrasonic treatment for 10 min and stirring for 30 min to obtain a silicon-fluorine polymer solution for standby;

step (2): mixing 2.5 mL tetraethoxysilane with 75 mL absolute ethyl alcohol, stirring for 10 min, adding 6 mL sodium hydroxide solution, stirring at room temperature, and reacting for 24 h to obtain base-catalyzed silica sol; removing the solvent and the catalyst of the base-catalyzed silica sol, dispersing in 50 mL absolute ethyl alcohol again, continuously adding 3 mL tetraethoxysilane, 0.5 mL deionized water and 0.3 mL sulfuric acid, stirring at room temperature, reacting 18H, adding 5 mL of 1H, 2H, 2H-perfluoro decyl trimethoxysilane, and continuously reacting 4H; finally removing the solvent by rotary evaporation to obtain cluster nano silicon dioxide;

step (3): dispersing 3 g cluster nano silicon dioxide in 18 g propylene glycol methyl ether acetate, dropwise adding the mixture into the silicon-fluorine polymer solution, carrying out ultrasonic treatment for 10 min, and stirring for 45 min to obtain the nano film crosslinked prepolymer.

2. Preparation of self-cleaning anti-reflection nano film

1: placing a super white glass substrate on a platform, and spraying the nano film crosslinked prepolymer on the surface of the substrate;

2: the above-described substrate coated with the nanofilm cross-linked prepolymer was left at room temperature 36 a h a final cured nanofilm was obtained to a thickness of about 900 a nm a.

Example 3

1. Preparation of nanomembrane crosslinked prepolymer

Step (1): adding 0.2. 0.2 g hydroxyl-terminated polydimethylsiloxane into a flask containing 0.3 g hexamethylene diisocyanate, 0.01 g dibutyl tin dilaurate and 2 g propylene glycol butyl ether, stirring under nitrogen atmosphere, keeping the temperature at 80 ℃, and reacting 6 h to obtain an organosilicon modified hexamethylene diisocyanate crosslinking agent; 2.4 g of chlorotrifluoroethylene and alkyl vinyl ether copolymer resin and 0.3 g of organosilicon modified hexamethylene diisocyanate are dissolved in 6 g butyl acetate by ultrasonic treatment for 10 min and stirring for 30 min to obtain a silicon-fluorine polymer solution for standby;

step (2): mixing 3 mL tetraethoxysilane with 100 mL absolute ethyl alcohol, stirring for 10 min, adding 4 mL potassium hydroxide solution, stirring at room temperature, and reacting 18 h to obtain base-catalyzed silica sol; after the solvent and the catalyst of the base-catalyzed silica sol are removed, the base-catalyzed silica sol is dispersed in 60 mL absolute ethyl alcohol again, 4 mL tetraethoxysilane, 0.5 mL deionized water and 0.6 mL hydrochloric acid are continuously added, stirring is kept at room temperature, 4 mL of 1H, 2H, 2H-perfluorooctyl trimethoxysilane are added after reaction 20H, and reaction 6H is continuously carried out; finally removing the solvent by rotary evaporation to obtain cluster nano silicon dioxide;

step (3): dispersing 2 g cluster nano silicon dioxide in 22 g butyl acetate, dropwise adding the mixture into the silicon-fluorine polymer solution, carrying out ultrasonic treatment for 10 min, and stirring for 60 min to obtain the nano film crosslinked prepolymer.

2. Preparation of self-cleaning anti-reflection nano film

2: the above-mentioned substrate coated with the nanofilm cross-linked prepolymer was placed in a forced air drying oven at 100 ℃ for heat treatment of 3 h to obtain a final cured nanofilm having a thickness of about 100 nm.

Comparative example 1

Step (1): 4 g trifluoro vinyl chloride and alkyl vinyl ester copolymer resin and 0.24 g isophorone diisocyanate are dissolved in 5 g butyl acetate by ultrasonic treatment for 10 min and stirring for 20 min to obtain coating liquid;

step (2): fixing the ultra-white glass substrate on a pressing table, and scraping the coating liquid on the surface of the substrate;

step (3): the substrate coated with the coating liquid was heat-treated in a forced air drying oven at 80℃for 2h to obtain a final cured coating layer having a thickness of about 500. 500 nm.

Comparative example 2

Step (1): 4 g tetrafluoroethylene and alkyl vinyl ester copolymer resin, 0.25 g hexamethylene diisocyanate and 0.02 g hydroxyl terminated polydimethylsiloxane are dissolved in 6 g butyl acetate by ultrasonic treatment for 10 min and stirring for 20 min to obtain coating liquid;

step (2): mixing the coating liquid with the silicon dioxide dispersion liquid, carrying out ultrasonic treatment for 10 min, and stirring for 30 min to obtain a mixed coating liquid;

step (3): placing an ultra-white glass substrate on a platform, and spraying the mixed coating liquid on the surface of the substrate;

step (4): the substrate coated with the coating liquid was placed in a 100 ℃ forced air drying oven for heat treatment 2h to obtain a final cured nanofilm with a thickness of about 500 a nm a.

Comparative example 3

Step (1): adding 1 g commercial alkali-catalyzed synthetic silica nanoparticles into a mixed solution of 50 mL absolute ethyl alcohol, 5 mL ammonia water and 0.6 mL of 1H, 2H, 2H-perfluorodecyl triethoxysilane, carrying out ultrasonic treatment for 20 min, stirring at room temperature for reaction 18H, filtering the mixed solution, washing 3 times by using ethanol, and drying the obtained filter cake in an oven at 80 ℃ to obtain fluorinated silica nanoparticles 12H;

step (2): dissolving 4 g trifluoro vinyl chloride and alkyl vinyl ester copolymer resin and 0.4 g hexamethylene diisocyanate trimer in 5 g butyl acetate by ultrasonic treatment for 10 min and stirring for 30 min to obtain a coating liquid; dispersing 0.025 g fluorinated silica nanoparticles in 3 g butyl acetate by ultrasonic treatment for 30 min to obtain a fluorinated silica dispersion;

step (3): mixing the coating liquid with the fluoridized silica dispersion liquid, carrying out ultrasonic treatment for 10 min, and stirring for 30 min to obtain a mixed coating liquid;

step (4): fixing the ultra-white glass substrate on a pressing table, and scraping the coating liquid on the surface of the substrate;

step (5): the substrate coated with the coating liquid was placed in a blast drying oven at 90 ℃ for heat treatment of 2h to obtain a final cured nanofilm with a thickness of about 500 a/nm a.

Further, in order to more clearly illustrate the advantages of the present disclosure, the performance test was performed on the coating films of the above examples and comparative examples, wherein the test method is as follows:

(1) Contact angle and sliding angle test of water/oil/organic solvent

The static contact angle of 10 mu L of deionized water, 10 mu L of sunflower seed oil and 10 mu L of absolute ethyl alcohol on the surface of the coating is measured by a contact angle measuring instrument, the dynamic sliding angle of 30 mu L of deionized water, 15 mu L of sunflower seed oil and 15 mu L of absolute ethyl alcohol on the surface of the coating is adopted, and the average value of measured values at different positions of at least 5 positions is taken as the final static contact angle or dynamic sliding angle of the coating.

(2) Light transmittance test

The transmittance of the nano film coated on the float ultra-white glass substrate was measured by using an ultraviolet-visible spectrophotometer, the wavelength range was 300-800 nm, and air was used as a blank background.

(3) Short circuit current density recovery rate (solar cell characteristics) test

Using a solar simulator (AM 1.5G, 100 mW/cm) ² ) And acquiring a short-circuit current-voltage curve of the monocrystalline silicon battery by matching with a data source table, and placing ultra-white glass with a film sample above the battery during testing. Spraying dust on the surface of the film sample by means of an electric powder gun to simulate dust deposition phenomenon in nature and control dust deposition density (g/cm) ² ) And keep the same. The dusted film samples were then cleaned with the same mass of deionized water at the same drip rate to simulate the rainfall and self-cleaning process in nature. The short-circuit current density recovery (%) is defined as follows:

short circuit current density recovery = (battery short circuit current density of coated glass sample after cleaning-battery short circuit current density of coated glass sample after dust contamination)/(battery short circuit current density of coated glass sample after initial coating film-battery short circuit current density of coated glass sample after dust contamination) ×100%

The results of the performance tests of the comparative examples and examples are shown in the following table 1:

table 1 comparison of the combined results of the above examples, comparative contact angle, slip angle, light transmittance and short circuit current density of the coating film to the photovoltaic cell

	Example 1	Example 2	Example 3	Comparative example 1	Comparative example 2	Comparative example 3
							Water contact angle/°	110.1	106.4	108.3	91.2	98.8	103.8
Oil contact angle/°	68.2	64.5	65.3	36.4	46.2	57.3
							Organic solvent contact angle/°	28.9	26.4	25.7	8.3	15.3	12.2
Water sliding angle/°	18.6	22.2	21.6	66.5	43.5	36.4
							Oil sliding angle/°	5.2	8.6	7.2	/	34.6	47.8
Sliding angle/° of organic solvent	13.5	14.8	15.1	/	/	/
							Transmittance-550 nm/%	93.0	92.3	92.7	91.3	82.7	84.6
Short circuit current density recovery/%	97.3	94.5	95.6	18.2	25.2	32.5

As shown in table 1, compared with the comparative example, the nano film prepared by the method disclosed by the invention integrates full lyophobic, anti-reflective and self-cleaning properties, and the ultra-white glass coated by the nano film disclosed by the invention can realize high-efficiency self-cleaning when being used as a photovoltaic cell panel, and the recovery rate of short-circuit current density can reach more than 94.5%.

As shown in table 1, comparative example 3 is a silica sol prepared directly using a single catalyst and subjected to fluorination modification, which is capable of improving the liquid contact angle of the nano-coating film, but is difficult to improve the sliding angle of the nano-coating film and enhance the anti-reflection performance. The reason is that: the silica obtained by base catalysis alone is spherical particles, and the lyophobicity of the coating film depends on the roughness, and only when the roughness is obviously increased, the contact angle of the coating film is increased, but the sliding angle is also increased. In addition, the refractive index of the silicon dioxide obtained by single base catalysis is low, and the anti-reflection performance is poor. Although silica with higher refractive index can be obtained by single acid catalysis, longer aging time is needed and the production period is long. In examples 1 to 3, spherical silica obtained by base catalysis was used as the core, and the silica shell was further coated with acid catalysis. The advantages of the two catalysis modes are combined to obtain clustered silica nanoparticles and free silica particles, the latter can be filled in the pores of the clusters formed by the former, the roughness of the nano coating is reduced, and the dependence of the lyophobicity of the coating on the roughness is reduced. In addition, the multiple refraction/reflection of the incident light inside the coating film is increased, so that the anti-reflection performance of the nano coating film is further enhanced.

As shown in Table 1, in comparative example 2, when the reactive silicone modifier is directly introduced into the reaction system of fluorocarbon polymer and isocyanate crosslinking agent to perform crosslinking reaction, the silicone modifier with low surface energy has poor compatibility in the system, and is easy to undergo macroscopic phase separation, so that the light transmittance is obviously reduced. Therefore, although the organosilicon modifier can give the nano-coating film a certain full liquid repellency and self-cleaning property, the requirement of the optical equipment for high light transmittance cannot be met. In examples 1-3, the silicone modifier and the excessive isocyanate crosslinking agent are subjected to grafting reaction in advance, so that the isocyanate crosslinking agent can be modified, the system compatibility is improved, and macroscopic phase separation is eliminated. In addition, the reasonable and effective distribution of the organosilicon chain segments and the nano particles in the resin system is beneficial to the refractive index matching between the resin and the nano particles, and the light transmittance of the nano film is improved together.

FIG. 1 is a graph showing the water contact angle results for the nanomembrane of comparative example 2; FIG. 2 is a graph showing the transmittance results of the nanomembrane of comparative example 2; fig. 1 and 2 show that although the liquid repellency of the nano film can be improved to a certain extent by directly adding the organic silicon into the fluorocarbon polymer and the isocyanate, the macroscopic phase separation of the organic silicon chain segments has obvious adverse effect on the light transmittance of the coating film, and the nano film cannot realize dynamic sliding on the organic solvent;

FIG. 3 is a water contact angle result of the nanomembrane of comparative example 3; FIG. 4 is a graph showing the transmittance results of the nanomembrane of comparative example 3; FIGS. 3 and 4 show that the introduction of fluorinated modified low surface energy silica particles directly into fluorocarbon polymers can improve the lyophobicity of the nanomembrane to some extent, but the light transmittance is reduced due to the agglomeration of the particles, the antireflection performance of the nanomembrane cannot be imparted, and the nanomembrane cannot realize dynamic slippage to an organic solvent;

FIG. 5 is a TEM image of clustered nano silica particles of example 1; FIG. 5 shows that the nano-silica has a core-shell structure, the outer shell has a villiated structure, the nano-silica is connected with each other and stacked into clusters, and the unique core-shell and cluster structure is beneficial to the multiple refraction and reflection of light inside the nano-film;

FIG. 6 is the water contact angle results for the nanomembrane surface of example 1; fig. 7 is a light transmittance result of the nano-film of example 1; FIGS. 6 and 7 show that the obtained nanomembrane cross-linked prepolymer, after curing into nanomembrane, combines the advantages of both core-shell cluster nanosilica particles and silicon fluoropolymers, has excellent total lyophobicity and anti-reflection properties;

FIG. 8 is a graph of short circuit current density versus voltage for a battery die, and battery after being covered on a photovoltaic cell, contaminated, and cleaned with the nanofilm coated ultrawhite glass of example 1; fig. 8 shows that the sample coated with the nano film can raise the short-circuit current density of the battery, even if it is polluted by dust, self-cleaning can be easily achieved by a small amount of water, and the recovery rate of the short-circuit current density after cleaning reaches 97.8%.

The above examples are merely representative of embodiments of the present disclosure, which are described in more detail and are not to be construed as limiting the scope of the present disclosure. It should be noted that modifications, equivalent substitutions, improvements, etc. can be made by those skilled in the art without departing from the spirit of the present disclosure, which are all within the scope of the present disclosure. Accordingly, the scope of protection of the present disclosure should be determined by the following claims.

Claims

1. The self-cleaning anti-reflection nano film is formed by coating and curing a nano film crosslinking prepolymer, and is characterized in that:

the fluorine modified nano silicon dioxide is cluster nano silicon dioxide which is synthesized by a sol-gel method through alkali and acid catalysis and is modified by in-situ fluorination and has a silicon dioxide spherical particle inner core;

the synthesis method of the fluorine modified nano silicon dioxide comprises the following steps:

synthesizing alkali-catalyzed silica sol by alkali catalysis by adopting the sol-gel method, and thermally treating the alkali-catalyzed silica sol to obtain concentrated silica sol; adding the concentrated silica sol and the fluorination modifier into a reaction solution for acid-catalyzed synthesis of the silica sol, and carrying out acid-catalyzed synthesis reaction to obtain the fluorine-modified nano-silica;

the fluorocarbon resin comprises a chlorotrifluoroethylene and alkyl vinyl ester copolymer resin, a tetrafluoroethylene and alkyl vinyl ether copolymer resin and a chlorotrifluoroethylene and alkyl vinyl ether copolymer resin;

the preparation method of the organosilicon modified isocyanate cross-linking agent comprises the following steps:

the method comprises the steps of (1) adding organosilicon which is equivalent to 0.5-20.0% of the total mass of fluorocarbon resin and isocyanate crosslinking agent into the isocyanate crosslinking agent, catalyst and solvent, wherein the dosage of the catalyst is 0.5-3.0% of the total solid mass; reacting at the constant temperature of 60-90 ℃ under the nitrogen atmosphere and in a stirring state for 1-12 h to obtain the organosilicon modified isocyanate crosslinking agent;

the organosilicon comprises reactive polydimethylsiloxane with hydroxyl or amino at a single end, double ends or side chains;

the isocyanate crosslinking agent is one or more of toluene diisocyanate, diphenylmethane diisocyanate, naphthalene diisocyanate, p-phenylene diisocyanate, dimethylbiphenyl diisocyanate, polymethylene polyphenyl isocyanate, hexamethylene diisocyanate, trimethyl hexamethylene diisocyanate, isophorone diisocyanate, tetramethylxylylene diisocyanate, methylcyclohexyl isocyanate and cyclohexane dimethylene diisocyanate.

2. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the alkali catalyst for the alkali catalysis is at least one of ammonia water, sodium hydroxide and potassium hydroxide.

3. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the acid catalyst for acid catalysis is at least one of hydrochloric acid, sulfuric acid, nitric acid and acetic acid.

4. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the fluorination modifier is at least one of 1H, 1H, 2H, 2H-perfluoro octyl trimethoxysilane, 1H, 2H, 2H-perfluoro octyl triethoxysilane, 1H, 2H, 2H-perfluoro decyl trimethoxysilane and 1H, 1H, 2H, 2H-perfluoro decyl triethoxysilane.

5. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the particle size of the cluster nano silicon dioxide is 10-500 nm.

6. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

the synthesis method of the concentrated silica sol comprises the following steps: base catalyst was added to the catalyst in the following 1: stirring and reacting the mixture of ethyl orthosilicate and absolute ethyl alcohol in a volume ratio of 10-50 at room temperature for 12-24 h to obtain alkali-catalyzed silica sol; and thermally treating the base-catalyzed silica sol to remove the absolute ethyl alcohol and the base catalyst to obtain the concentrated silica sol.

7. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

8. The self-cleaning anti-reflective nanomembrane of claim 1, wherein:

9. The method for preparing the self-cleaning anti-reflection nano film according to any one of claims 1 to 8, comprising:

obtaining fluorocarbon resin containing hydroxyl and carboxyl groups;

after adding organosilicon into a mixture containing isocyanate crosslinking agent, catalyst and solvent, the organosilicon modified isocyanate crosslinking agent is obtained as a reaction product in a nitrogen atmosphere under a stirring state;

according to the fluorocarbon resin: the mass ratio of the organosilicon modified isocyanate crosslinking agent is 3-10:1, mixing the two materials in proportion to obtain a silicon fluorine polymer;

and mixing the silicon fluoropolymer with fluorine modified nano silicon dioxide to obtain the nano film crosslinking prepolymer.

10. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the molecular weight of the organic silicon is Mn=500-20000 g/mol.

11. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the catalyst is at least one of dibutyl tin dilaurate and stannous isooctanoate.

12. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

the solvent is at least one of acetone, butanone, ethylene glycol methyl ether, propylene glycol butyl ether, dipropylene glycol butyl ether, ethylene glycol methyl ether acetate, propylene glycol methyl ether acetate and dipropylene glycol dimethyl ether.

13. The method for preparing the self-cleaning anti-reflection nano film according to claim 9, wherein the method comprises the following steps:

dispersing the fluorine modified nano silicon dioxide in a diluent to obtain a dispersion liquid with the solid content of 5-50%;

according to fluorocarbon resin: the organosilicon modified isocyanate crosslinking agent is 3-10:1, mixing the two materials in a mass ratio, and diluting the mixture with a diluent to obtain a silicon-fluorine polymer solution with a solid content of 20-50%;

and (3) dripping fluorine modified nano silicon dioxide dispersion into the silicon-fluorine polymer solution in a state of ultrasonic treatment for 10-30 min and stirring for 10-60 min, and performing a crosslinking reaction to obtain the nano film crosslinking prepolymer.

14. The method for preparing the self-cleaning anti-reflection nano film according to claim 13, wherein:

the mass ratio of the silicon fluorine polymer solution to the fluorine modified nano silicon dioxide dispersion liquid is 0.07-0.6:1.

15. the method for preparing the self-cleaning anti-reflection nano film according to claim 13, wherein:

the diluent is at least one of butyl acetate, propylene glycol methyl ether acetate and xylene.