Long-acting PET material anti-fog film for rearview mirror and preparation method of long-acting PET material anti-fog film

Abstract

The invention belongs to the field of preparation of anti-fog film materials, and particularly relates to a long-acting PET material anti-fog film for rearview mirrors and a preparation method of the long-acting PET material anti-fog film. The anti-fog film disclosed by the invention is prepared from the following raw materials in parts by mass: 90 to 100 parts of acrylamide monomers, 0.1 to 1.5 parts of an initiator, 1 to 1.3 parts of sodium pyrosulfite, 85 to 95 parts of absolute ethyl alcohol, 1 to 5 parts of functionalized nano silicon dioxide and 3 to 10 parts of deionized water. According to the preparation method disclosed by the invention, the functionalized nano silicon dioxide is used as functional particles to be added into polymerization of acrylamide monomers, and then the film precursor is soaked in the functional liquid, so that the anti-fog film with excellent comprehensive performance is prepared, the service life of the anti-fog film is prolonged, and the driving safety is improved.

Description

Technical Field

[0001] The present invention belongs to the field of preparation of anti-fog film materials, and particularly relates to a long-lasting anti-fog film for rearview mirrors made of PET material and a preparation method thereof. Background Art

[0002] Automobile anti-fog films play an important role in automobile driving. Keeping the windows and rearview mirrors clean is crucial for driving safety. Dirty windows and rearview mirrors can interfere with the driver's line of sight, increasing the driving difficulty and potential safety hazards. The self-cleaning performance of the anti-fog film can ensure that the windows and rearview mirrors always remain clean during driving, providing a clear field of vision for the driver. The core principle of the anti-fog film lies in its special nano-material coating, which has two major characteristics: one is "anti-fog", and the other is "self-cleaning". When water vapor in the air contacts the anti-fog film, the tiny structures on the coating can quickly disperse the water vapor, preventing it from condensing into fog on the window or rearview mirror. In this way, even in a foggy environment, the windows and rearview mirrors can remain clear and transparent, improving driving safety.

[0003] Although the main function of the anti-fog film is to prevent the window from fogging up, in some cases, it may affect the clarity of the line of sight. Especially when driving in low light or at night, the anti-fog film may reduce the light transmittance of the window and rearview mirror, thus affecting the driver's line of sight. And currently, some anti-fog films contain small molecules soluble in water, which will cause streaks and coloration after anti-fogging, and there are problems such as low hardness, difficult-to-persist anti-fog effect, poor film-forming property during coating, poor water resistance, and poor heat aging resistance. Patent CN 113698656A discloses an anti-fog film material and a preparation method thereof, including the following steps: adding allyl succinimidyl carbonate, ethylene glycol dimethacrylate, polyethylene glycol monoallyl ether, N-vinyl carbazole, vinyl β-cyclodextrin quaternary ammonium salt, 2,3,5,6-tetrafluoroterephthalic acid, terminal isocyanate group polyurethane prepolymer, initiator, catalyst, and nano-titanium dioxide into an organic solvent, stirring evenly, coating on a polytetrafluoroethylene plate or a glass plate, placing it in an inert gas atmosphere, drying to constant weight at 85-95 °C, and then peeling off the film to obtain a polymer film; radiation grafting to obtain the anti-fog film material. The anti-fog film material of the present invention has a significant anti-fog effect, good anti-oil and dust pollution performance, excellent thermal stability, abrasion resistance, mechanical properties, durability, and performance stability. However, the water resistance of the anti-fog film material in this invention still needs to be improved.

[0004] Therefore, it is of great practical significance to develop an anti-fog film with good water resistance and a long-lasting anti-fog effect. Summary of the Invention

[0005] The invention discloses a long-lasting anti-fog film for a rearview mirror made of PET material and a preparation method thereof. Functionalized nano silicon dioxide is added as reinforcing particles into the polymerization of acrylamide monomers, and then the film precursor is immersed in a functional liquid to prepare an anti-fog film with excellent comprehensive performance, which is beneficial to improving the life of the anti-fog film and driving safety.

[0006] To achieve the above purpose, the technical solution adopted by the present invention is as follows:

[0007] The first aspect of the present invention provides a long-lasting anti-fog film for a rearview mirror made of PET material. The anti-fog film is prepared by the following raw materials, calculated by weight:

[0008] 90-100 parts of acrylamide monomer, 0.1-1.5 parts of initiator, 1-1.3 parts of sodium pyrosulfite, 85-95 parts of anhydrous ethanol, 1-5 parts of functionalized nano-silicon dioxide and 3-10 parts of deionized water;

[0009] The raw materials also include a functional liquid containing silica sol.

[0010] In some embodiments, the preparation steps of the functionalized nano-silica are:

[0011] (1) adding 1,4-butane sultone and 3-(2-aminoethyl)aminopropyltrimethoxysilane to a solvent, stirring and reacting at 20-30° C. for 3-5 hours, filtering and drying to obtain a product;

[0012] (2) Dispersing nano-silica in deionized water, adding the product of step (1) thereto, reacting at 60-70° C. for 4-5 hours, centrifuging, washing, and drying to obtain functionalized nano-silica.

[0013] In some embodiments, the molar ratio of 1,4-butane sultone to 3-(2-aminoethyl)aminopropyltrimethoxysilane is (1-1.2):1.

[0014] Preferably, the molar ratio of 1,4-butanesultone to 3-(2-aminoethyl)aminopropyltrimethoxysilane is 1.1:1.

[0015] In some embodiments, the particle size of the nano-silica is 5-50 nm.

[0016] Preferably, the particle size of the nano-silicon dioxide is 10-30 nm.

[0017] In some embodiments, the mass ratio of nano-silicon dioxide to product in step (2) is (4.5-5.5):1.

[0018] Preferably, in step (2), the mass ratio of nano-silicon dioxide to product is 5:1.

[0019] In some embodiments, the acrylamide monomer includes one or more of methacrylamide, AMPS, DMC, and N-substituted acrylamide compounds.

[0020] In some embodiments, the amount of the functionalized nano-silica is 1.5-4.5 wt% of the acrylamide monomer.

[0021] Preferably, the amount of the functionalized nano-silica is 3 wt% of the acrylamide monomer.

[0022] The second aspect of the present invention provides a preparation method of an anti-fog film for a rearview mirror made of long-lasting PET material, including the following preparation steps:

[0023] S1. Add deionized water to the functionalized nano-silica and disperse it by ultrasonic wave to obtain a functionalized nano-silica aqueous solution.

[0024] S2. Mix the acrylamide monomer, initiator, sodium metabisulfite, and the functionalized nano-silica aqueous solution obtained in step S1 evenly, react at 40-50 °C, then add absolute ethanol thereto and mix evenly to obtain a long-lasting anti-fog coating.

[0025] S3. Apply the long-lasting anti-fog coating obtained in step S2 on the surface of the substrate and dry it to obtain a film precursor.

[0026] S4. Immerse the film precursor obtained in step S3 in the functional liquid, separate it, and cure it to obtain the anti-fog film.

[0027] In some embodiments, the functional liquid is a 3-5 wt% aqueous solution of silicon sol.

[0028] Preferably, the functional liquid is a 4 wt% aqueous solution of silicon sol.

[0029] In some embodiments, the thickness of the anti-fog film in the above scheme is 1-50 μm.

[0030] In the present invention, the product obtained by reacting 1,4-butanesultone with 3-(2-aminoethyl)aminopropyltrimethoxysilane is used to modify nano-silica and applied to an anti-fog film, which can significantly improve the water resistance, aging resistance and abrasion resistance of the anti-fog film, enabling it to maintain good performance and service life in a wider range of environments. 1,4-Butanesultone is an organic sulfonate compound containing a sulfonic acid group and has strong reactivity; 3-(2-aminoethyl)aminopropyltrimethoxysilane is a compound containing an amino group and a silyl group, and its silyl part can react with the hydroxyl groups on the surface of nano-silica to form stable chemical bonds. The applicant found that by controlling the reaction conditions, 1,4-butanesultone reacts with 3-(2-aminoethyl)aminopropyltrimethoxysilane, and a sulfonate product may be formed. This product undergoes a hydrolysis reaction during the modification process to generate silanol groups (Si-OH). These silanol groups undergo a condensation reaction with the hydroxyl groups on the surface of nano-silica to graft organic groups onto the surface of nano-silica. At the same time, the generated sulfonate substances are introduced onto the surface of nano-silica by chemical bonding or physical adsorption, which not only improves the dispersibility and stability of nano-silica in the polymer matrix but also endows nano-silica with new functional characteristics. The sulfonic acid groups in the functionalized nano-silica have hydrophilicity, but through bonding with nano-silica, this hydrophilicity is effectively controlled and converted into water repellency. At the same time, the modified nano-silica particles form a dense network structure in the polymer matrix, further blocking the penetration of water molecules, thereby improving the water resistance of the anti-fog film; the functionalized nano-silica can also absorb ultraviolet light and convert it into harmless heat energy, thereby reducing the direct damage of ultraviolet light to nano-silica and the polymer matrix, and improving the aging resistance, thermal stability and antioxidant properties; in addition, a stronger interaction force is formed between the functionalized nano-silica and the polymer matrix, making the distribution of nano-particles in the matrix more uniform and firm, improving the hardness and abrasion resistance of the anti-fog film, and making the anti-fog film less likely to produce scratches and abrasions when subjected to external frictional forces.

[0031] The compatibility between the functionalized nano-silica and the polymer in the present invention helps to form a uniform and dense membrane structure during the subsequent polymerization process. In the present invention, acrylamide monomers are used as polymerization monomers, and polymerization reactions occur under the action of initiators. During the polymerization process, the functionalized nano-silica is uniformly dispersed in the polymer matrix as a filler or reinforcing agent. Its presence restricts the movement of polymer chains, improving the rigidity and wear resistance of the polymer. As the polymerization reaction proceeds, the polymer matrix gradually solidifies and wraps the nano-silica particles, forming an anti-fog film with a specific thickness and surface morphology. Moreover, the surface of the anti-fog film has micro-nano structures due to the presence of the functionalized nano-silica. These structures can reduce the contact angle between water droplets and the film surface, enabling the water droplets to spread rapidly on the film surface and form a uniform water film, thereby achieving the anti-fog effect. A good interaction force is formed between the functionalized nano-silica and the polymer matrix, enabling the surface of the anti-fog film to remain wet and quickly expel water droplets, thus having excellent anti-fog performance. In addition, the sulfonic acid groups in the functionalized nano-silica also have ion exchange properties, which can further improve the wettability and anti-fouling performance of the anti-fog film.

[0032] In addition, the present invention also immerses the film precursor in a functional liquid of silica sol with a specific concentration, which can improve the anti-fog performance of the anti-fog film, making it have more excellent anti-fog performance and durability. When the anti-fog film is immersed in this silica sol solution, the silicate ions in the silica sol will undergo hydrolysis and polycondensation reactions on the film surface, forming a dense and smooth silica protection layer, which can improve the anti-fog effect, reduce the surface energy, regulate the micro-nano structure, increase the roughness, and further enhance the durability of the anti-fog film and improve the light transmittance.

[0033] Compared with the prior art, the beneficial effects of the present invention are as follows:

[0034] 1. The present invention discloses a long-lasting anti-fog film for rearview mirrors made of PET material and its preparation method. By adding functionalized nano-silica as functional particles to the polymerization of acrylamide monomers and then immersing the film precursor in the functional liquid, an anti-fog film with excellent comprehensive performance is prepared, which is beneficial to improving the lifespan of the anti-fog film and driving safety.

[0035] 2. The present invention modifies the nano-silica, not only improving its dispersibility and stability in the polymer matrix, but also firmly fixing the nano-particles in the film structure through chemical bonding. This structure enables the anti-fog film to maintain stable performance when subjected to external factors such as moisture, ultraviolet rays, and mechanical friction. It improves the anti-fog performance, water resistance, aging resistance, and wear resistance of the anti-fog film.

[0036] 3. The present invention also immerses the film precursor in a functional liquid of silica sol with a specific concentration, which can improve the anti-fog performance of the anti-fog film, making it have more excellent anti-fog performance and durability. Detailed implementation manners

[0037] The various exemplary implementation manners of the present invention will now be described in detail. This detailed description should not be considered as a limitation on the present invention, but rather as a more detailed description of certain aspects, characteristics, and implementation schemes of the present invention. It should be understood that the terms used in the present invention are only for describing specific implementation manners and are not used to limit the present invention. Additionally, for the numerical ranges in the present invention, it should be understood that each intermediate value between the upper and lower limits of the range is also specifically disclosed. Each intermediate value within any stated value or stated range, as well as each smaller range between any other stated value or intermediate value within the stated range, is also included in the present invention. The upper and lower limits of these smaller ranges may be independently included or excluded from the range.

[0038] Unless otherwise specified, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the art to which the present invention pertains. Although the present invention only describes preferred methods and materials, any methods and materials similar or equivalent to those described herein can also be used in the implementation or testing of the present invention. Without departing from the scope or spirit of the present invention, various improvements and variations can be made to the specific implementation manners of the present invention specification, which are obvious to those skilled in the art. Other implementation manners obtained from the present invention specification are obvious to those skilled in the art. The specification and examples of this application are merely exemplary.

[0039] Regarding "comprising", "including", "having", "containing", etc. used herein, they are all open-ended terms, meaning including but not limited to.

[0040] It should be noted that the post-treatment steps such as "suction filtration", "drying", "centrifugation", "stirring", "ultrasonic dispersion", etc. that appear in the following examples are conventional operations of those skilled in the art and can be selected according to actual operations.

[0041] The initiator used in the present invention is ammonium persulfate; the nano-silica used in Preparation Examples 1-3 and Comparative Example 1 is spherical nano-silica with an average particle size of 7 nm; the substrate used is a PET substrate and is subjected to corona treatment; the silica sol used is purchased from Shanghai Shuanglun Industrial Co., Ltd. with the product number HS-40; the coating method used is the spraying method. The pH of the silica sol aqueous solution is adjusted to 4.0 using acetic acid aqueous solution.

[0042] Preparation Example 1

[0043] The preparation steps of the functionalized nano-silica are as follows:

[0044] (1) Add 0.11 mol of 1,4-butanesulfonic acid lactone and 0.1 mol of 3-(2-aminoethyl)aminopropyltrimethoxysilane to 400 mL of acetone, stir and react at 25 °C for 4 h, filter by suction and dry to obtain the product;

[0045] (2) Ultrasonically disperse 1 g of nano-silica in 100 mL of deionized water, add 0.2 g of the product from step (1) thereto, react at 65 °C for 4.5 h, centrifuge, wash with deionized water 3 times and dry to obtain functionalized nano-silica.

[0046] Preparation Example 2

[0047] The preparation steps of the functionalized nano-silica are the same as those of Preparation Example 1, except that 0.13 mol of 1,4-butanesulfonic acid lactone is used.

[0048] Preparation Example 3

[0049] The preparation steps of the functionalized nano-silica are the same as those of Preparation Example 1, except that 0.8 g of nano-silica is used.

[0050] Preparation Example 4

[0051] The preparation steps of the functionalized nano-silica are the same as those of Preparation Example 1, except that the used nano-silica is spherical nano-silica with an average particle size of 100 nm.

[0052] Example 1

[0053] A preparation method of an anti-fog film for a rearview mirror of a long-lasting PET material, comprising the following preparation steps:

[0054] S1. According to the mass parts, add 3 parts of deionized water to 1.35 parts of functionalized nano-silica, ultrasonically disperse for 30 min to obtain a functionalized nano-silica aqueous solution;

[0055] S2. According to the mass parts, mix 90 parts of methacrylamide, 0.3 part of initiator, 1 part of sodium metabisulfite and the functionalized nano-silica aqueous solution in step S1 evenly, react at 50 °C for 15 min, then add 85 parts of absolute ethanol thereto and mix evenly to obtain a long-lasting anti-fog coating;

[0056] S3. Apply the long-lasting anti-fog coating in step S2 on the surface of the substrate, dry at 65 °C for 20 h to obtain a film precursor;

[0057] S4. Immerse the film precursor in step S3 in a 3 wt% aqueous solution of silicon sol for 10 min, separate, and cure at 170 °C for 4 h to obtain an anti-fog film with a thickness of 20 μm.

[0058] The functionalized nano-silica used is obtained from Preparation Example 1.

[0059] Example 2

[0060] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, comprising the following preparation steps:

[0061] S1. By mass, add 10 parts of deionized water to 4.5 parts of functionalized nano-silica, and ultrasonically disperse for 30 min to obtain a functionalized nano-silica aqueous solution;

[0062] S2. By mass, mix 100 parts of AMPS, 1.5 parts of initiator, 1.3 parts of sodium metabisulfite and the functionalized nano-silica aqueous solution in step S1 evenly, react at 40 °C for 35 min, then add 95 parts of absolute ethanol thereto, and mix evenly to obtain a long-lasting anti-fog coating;

[0063] S3. Apply the long-lasting anti-fog coating in step S2 on the surface of the substrate, and dry at 75 °C for 15 h to obtain a film precursor;

[0064] S4. Immerse the film precursor in step S3 in a 5 wt% aqueous solution of silicon sol for 20 min, separate, and cure at 180 °C for 3 h to obtain an anti-fog film with a thickness of 20 μm.

[0065] The functionalized nano-silica used is obtained from Preparation Example 1.

[0066] Example 3

[0067] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, comprising the following preparation steps:

[0068] S1. By mass, add 7 parts of deionized water to 2.85 parts of functionalized nano-silica, and ultrasonically disperse for 30 min to obtain a functionalized nano-silica aqueous solution;

[0069] S2. By mass, mix 95 parts of N-(2-hydroxyethyl)methacrylamide, 0.75 parts of initiator, 1.2 parts of sodium metabisulfite and the functionalized nano-silica aqueous solution in step S1 evenly, react at 45 °C for 25 min, then add 90 parts of absolute ethanol thereto, and mix evenly to obtain a long-lasting anti-fog coating;

[0070] S3. Apply the long-lasting anti-fog coating in step S2 on the surface of the substrate, and dry at 70 °C for 18 h to obtain a film precursor;

[0071] S4. Immerse the film precursor in step S3 in a 4 wt% aqueous solution of silicon sol for 15 min, separate, and cure at 175 °C for 3.5 h to obtain an anti-fog film with a thickness of 20 μm.

[0072] The functionalized nano-silica used is obtained from Preparation Example 1.

[0073] Example 4

[0074] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, the specific implementation manner is the same as that of Example 3, the difference is that the functionalized nano-silica used is obtained from Preparation Example 2.

[0075] Example 5

[0076] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, the specific implementation manner is the same as that of Example 3, the difference is that the functionalized nano-silica used is obtained from Preparation Example 3.

[0077] Example 6

[0078] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, the specific implementation manner is the same as that of Example 3, the difference is that the functionalized nano-silica used is obtained from Preparation Example 4.

[0079] Example 7

[0080] A preparation method of a long-lasting anti-fog film for a rearview mirror made of PET material, the specific implementation manner is the same as that of Example 3, the difference is that an equal mass of DMC is used instead of N-(2-hydroxyethyl) methacrylamide.

[0081] Comparative Example 1

[0082] A preparation method of an anti-fog film for a rearview mirror made of PET material, the specific implementation manner is the same as that of Example 3, the difference is that an equal mass of nano-silica is used instead of functionalized nano-silica.

[0083] Comparative Example 2

[0084] A preparation method of an anti-fog film for a rearview mirror made of PET material, including the following preparation steps:

[0085] S1. By mass, 7 parts of deionized water are added to 2.85 parts of functionalized nano-silica, and ultrasonic dispersion is carried out for 30 min to obtain a functionalized nano-silica aqueous solution;

[0086] S2. By mass, 95 parts of N-(2-hydroxyethyl) methacrylamide, 0.75 part of initiator, 1.2 parts of sodium metabisulfite and the functionalized nano-silica aqueous solution in step S1 are mixed evenly, reacted at 45 °C for 25 min, and then 90 parts of absolute ethanol are added thereto and mixed evenly to obtain a long-lasting anti-fog coating;

[0087] S3. Apply the long-lasting anti-fog coating in Step S2 on the surface of the substrate and dry it at 70 °C for 18 h to obtain an anti-fog film with a thickness of 20 μm.

[0088] The functionalized nano-silica used is obtained from Preparation Example 1.

[0089] Comparative Example 3

[0090] A preparation method of an anti-fog film for a PET material rearview mirror includes the following preparation steps:

[0091] S1. By mass parts, mix 95 parts of N-(2-hydroxyethyl) methacrylamide, 0.75 part of initiator, 1.2 parts of sodium metabisulfite, and 0.475 part of the product in Step (1) of Preparation Example 1 evenly, react at 45 °C for 25 min, then add 90 parts of absolute ethanol thereto and mix evenly to obtain a long-lasting anti-fog coating.

[0092] S2. Apply the long-lasting anti-fog coating in Step S1 on the surface of the substrate and dry it at 70 °C for 18 h to obtain a film precursor.

[0093] S3. Immerse the film precursor in Step S2 in a 4 wt% aqueous solution of silicon sol for 15 min, separate it, and cure it at 175 °C for 3.5 h to obtain an anti-fog film with a thickness of 20 μm.

[0094] Performance testing of the anti-fog film

[0095] In the present invention, the anti-fog coating compositions of each example and comparative example are coated on the substrate by spraying method, and the leveling effect on the film surface during the curing process of the formed anti-fog coating is very good and the film-forming property is excellent. Then, the following performance tests are carried out on the anti-fog films obtained in each example and comparative example:

[0096] 1. Tensile strength: Test according to GB / T1040.1-2006;

[0097] 2. Heat aging resistance: Measured by the retention rate of tensile strength after the anti-fog film is placed in hot air at 85 °C for artificial accelerated aging for 96 h;

[0098] 3. Light transmittance: Measure according to the method specified in GB / T 2410;

[0099] 4. Abrasion resistance: Use 0000# steel wool, 300 g force, and record one back-and-forth friction as one time: After a certain number of frictions, observe whether there are scratches and record the maximum number of frictions that can be tolerated without scratches;

[0100] 5. Anti-fog grade: Measure according to the method specified in GB / T 31726-2015;

[0101] 6. Water resistance performance: Referring to GB / T 1733-1993, the anti-fog film was immersed in deionized water, and the appearance of blistering, whitening, and peeling was observed.

[0102] The specific test results are shown in Table 1.

[0103] Table 1

[0104]

[0105] As can be seen from Table 1, the anti-fog films prepared in Examples 1-3 and Example 7 have excellent comprehensive properties, with good tensile strength, heat aging resistance, and wear resistance, high light transmittance, high anti-fog grade, and good water resistance performance. Compared with Example 3, the preparation process of the functionalized nano-silica used in Examples 4-6 changed (raw material dosage, particle size of nano-silica), which affected the reaction of 1,4-butanesultone with 3-(2-aminoethyl) aminopropyltrimethoxysilane and the grafting of its product on the surface of nano-silica, resulting in a change in the performance of the functionalized nano-silica and a decrease in its dispersibility and stability in the anti-fog coating system, leading to a reduction in the comprehensive performance of the anti-fog film; in Comparative Example 1, nano-silica was used instead of functionalized nano-silica, and the dispersibility and stability of nano-silica in the anti-fog coating were poor, thus affecting the comprehensive performance of the anti-fog film; in Comparative Example 2, the anti-fog film was not impregnated in the functional liquid, and a dense and smooth silica protective layer was not formed on the surface, which reduced the comprehensive performance of the anti-fog film to a certain extent; in Comparative Example 3, instead of adding functionalized nano-silica, a certain amount of the product in step (1) of Preparation Example 1 was added, which also caused a reduction in the comprehensive performance of the anti-fog film.

[0106] The above is only a preferred embodiment of the present invention and does not impose any form of limitation on this application. Although this application is disclosed as a preferred embodiment, it is not intended to limit this application. Any person skilled in the art, without departing from the scope of the technical solution of this application, making some changes or modifications using the disclosed technical content is equivalent to an equivalent implementation case. However, as long as it does not depart from the content of the technical solution of the present invention, any simple modification, equivalent change, and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution.

Claims

1. A long-lasting anti-fog film for rearview mirrors made of PET material, characterized in that, The preparation of the anti-fog film comprises the following raw materials by mass parts: 90 - 100 parts of acrylamide monomer, 0.1 - 1.5 parts of initiator, 1 - 1.3 parts of sodium metabisulfite, 85 - 95 parts of absolute ethanol, 1 - 5 parts of functionalized nano-silica, and 3 - 10 parts of deionized water; The raw materials further include a functional liquid containing silica sol.

2. The anti-fog film according to claim 1, characterized in that, The preparation steps of the functionalized nano-silica are as follows: (1) Add 1,4-butanesultone and 3-(2-aminoethyl)aminopropyltrimethoxysilane into a solvent, stir and react at 20 - 30 °C for 3 - 5 h, filter by suction and dry to obtain a product; (2) Disperse nano-silica in deionized water, add the product of step (1) thereto, react at 60 - 70 °C for 4 - 5 h, centrifuge, wash and dry to obtain functionalized nano-silica.

3. The anti-fog film according to claim 2, characterized in that, The molar ratio of 1,4-butanesultone to 3-(2-aminoethyl)aminopropyltrimethoxysilane is (1 - 1.2):

1.

4. The anti-fog film according to claim 2, wherein The particle size of the nano-silica is 5 - 50 nm.

5. The anti-fog film according to claim 2, characterized in that, In step (2), the mass ratio of nano-silica to the product is (4.5 - 5.5):

1.

6. The anti-fog film according to claim 1, characterized in that, The acrylamide monomer is one or more of methacrylamide, AMPS, DMC, and N-substituted acrylamide compounds.

7. The anti-fog film according to claim 1, characterized in that, The dosage of the functionalized nano-silica is 1.5 - 4.5 wt% of the acrylamide monomer.

8. A method for preparing a long-lasting anti-fog film for a rearview mirror made of PET material according to any one of claims 1-7, characterized in that, It includes the following preparation steps: S1. Add deionized water to the functionalized nano-silica and disperse it by ultrasonic to obtain a functionalized nano-silica aqueous solution; S2. Mix the acrylamide monomer, initiator, sodium metabisulfite and the functionalized nano-silica aqueous solution in step S1 evenly, react at 40 - 50 °C, then add absolute ethanol thereto and mix evenly to obtain a long-acting anti-fog coating; S3. Apply the long-acting anti-fog coating in step S2 on the surface of a substrate and dry to obtain a film precursor; S4. Immerse the film precursor in step S3 in the functional liquid, separate and cure to obtain the anti-fog film.

9. The method for preparing the anti-fog film according to claim 8, wherein, The functional liquid is a 3 - 5 wt% silica sol aqueous solution.

10. The preparation method of the anti-fog film according to claim 8, characterized in that, The thickness of the anti-fog film is 1 - 50 μm.

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