JPH03181588A - Production of anti-fogging coating film - Google Patents

Abstract

PURPOSE:To form anti-fogging coating films having excellent durability and water resistance by applying a coating composition consisting essentially of a specific PVA and a crosslinking agent, curing under heating and further immersing in an aqueous solution of acid in a specific condition. CONSTITUTION:A coating composition comprising (A) a PVA having >=70mol% saponification degree and >=300 (preferably <=3,000) average molecular weight and (B) a crosslinking agent preferably composed of silane coupling agent as main components is applied, heated to about 50-250 deg.C, cured and further immersed in an aqueous solution of acid composed of preferably HCI, having pH <=5 for 0.5 minute to 5 hours to give the objective anti-fogging coating film.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a coating having excellent durability and antifogging properties.

[Prior Art] Inorganic glass, plastic materials, and the like are widely used in articles such as mirror surfaces, window glasses, eyeglass lenses, and goggles, taking advantage of their properties as transparent base materials.

However, articles using these transparent substrates have the problem that dew condensation occurs on the surface of the article, causing it to become cloudy, due to environmental changes such as when the temperature and humidity change significantly from a place of high temperature and high humidity, or from a place of low temperature and low humidity. Particularly among transparent substrates, it has been a serious problem that the surfaces of articles such as mirror surfaces, window glasses, and eyeglass lenses are easily clouded and scratched.

Therefore, attempts have been made to impart antifogging properties to various articles including transparent substrates. For example, a technique for improving the wettability of an article surface by applying or mixing a hydrophilic substance such as a surfactant is disclosed in U.S. Patent No. 3.479.30.
It is disclosed in No. 8. However, this technique only provides temporary anti-fogging properties to articles, but does not have a lasting effect.

In addition, a method of coating a hydrophilic polymer in order to impart durability to antifogging properties has also been used. For example, U.S. Pat.
No. 127.682 contains polyvinyl alcohol (PVA)
) is crosslinked with zirconium nitrate and formaldehyde. Further, coatings made of PVA and silica particles are also disclosed in US Pat. No. 3.773.776, US Pat. No. 4.016.129, and the like.

However, these techniques have the disadvantage that the inherent hydrophilicity of PVA is significantly reduced, thereby reducing the antifogging effect or having insufficient water resistance.

[Problem 3 to be solved by the present invention] As described above, the conventional techniques do not satisfy long-lasting antifogging properties and water resistance, and are poor in practicality.

The present invention aims to eliminate the drawbacks of the prior art, and aims to provide an anti-fog film that has excellent anti-fog properties, lasts long, and has excellent water resistance.

[Means for Solving the Problems] The present invention has the following configuration to achieve the above object.

"A step of applying a coating composition mainly composed of the following A component and Bd component, followed by a step of curing by heating, and further immersed in an acidic aqueous solution of 0.01 wt% or more and 40 wt% or less for 0.5 minutes or more for 5 hours. A method for producing an antifogging film, comprising the following steps of dipping.

Component A: polyvinyl alcohol with a degree of saponification of 70 mol% or more and an average degree of polymerization of 300 or more Component B: crosslinking agent" In the present invention, the polyvinyl alcohol used as A is produced by partial hydrolysis or complete hydrolysis of polyvinyl acetate. The average degree of polymerization (JIS
Polyvinyl alcohol having a hydroxyl group with a saponification degree (value determined according to IIs K 6726) of 300 or more and a saponification degree (value determined according to IIs K 6726) of 70 mol% or more is used in the present invention. If the average degree of polymerization is less than 300, durability and water resistance will decrease, and the upper limit is 3.
000 or less, and if it is greater than 3000, the viscosity will increase when used as a paint, and there will be a problem in work that it will be difficult to obtain a smooth coating film. Further, if the degree of saponification is lower than 70 mol%, it is difficult to exhibit sufficient antifogging performance.

The crosslinking agent used as component B in the present invention is not particularly limited as long as it can make polyvinyl alcohol insoluble in water, and many known crosslinking agents can be used. Specific crosslinking agents include epoxy resins, melamine resins, silane coupling agents, various metal compounds, and urea resins. Among the crosslinking agents, silane coupling agents are preferred from the viewpoint of many properties such as transparency, ease of crosslinking, improved hardness, and water resistance, and in particular compounds represented by the following general formula (I) or (n), and their Hydrolysates are preferably used.

R', R2b S I X4(a+b+ (I
)R3R5 Q3-(e+ll S i Y S i Q3-
fe+fl (n) R4, R6゜ (here, R1, R3, R5 are organic groups having 4 to 14 carbon atoms and having an epoxy group, R2, R4, and R6 are organic groups having 1 to 1 carbon atoms)
4 hydrocarbon group, or halogen group, mercapto group,
A hydrocarbon group having 1 to 14 carbon atoms having a substituent selected from a cyano group, a (meth)acryloxy group, and an amine group,
X and Q represent hydrolyzable groups. a, C, and e are each 0 or I, and b, d, and f are each 0. I or 2. Furthermore, (a+b), (c
+d).

(e+f) are 0, 1 or 2, respectively.

Y is an organic group having 2 to 40 carbon atoms. ) In general formula (I), examples of the epoxy group contained in R+ include aliphatic epoxy groups such as glycidoxy group, alicyclic epoxy groups such as 3,4-epoxycyclohexyl group, etc., and as R1, It is an organic group having 4 to 14 carbon atoms including these epoxy groups, and 5t- as a -valent organic group.
It is included in silane compounds due to C bonds.

In addition, R2 is a methyl group, an ethyl group, a vinyl group,
1 or more carbon atoms such as propyl group, octyl group, phenyl group, etc.
14 hydrocarbon groups and substituent derivatives of these hydrocarbon groups. Such substituents include halogen groups such as chloro group and fluoro group, mercapto group, cyano group, (
Examples include a meta)acroxy group and an amino group. R2 is also R
Similar to 1, it is a -valent organic group and is included in the silane compound as a 5i-C bond. In addition, X is a hydrolyzable group, such as an alkoxy group such as a methoxy group, an ethoxy group, a butoxy group, a carboxy group such as an acetoxy group, a halogen group such as a chloro group or a bromo group, a methoxyethoxy group, an ethoxyethoxy group, etc. Examples include alkoxyalkoxy groups, ketoxime groups, propenyl groups, and the like.

Furthermore, a is O or 1, and b is 0, or 2. Furthermore, (a+b) is 0.1 or 2. When b is 2, R2 may be the same or different.

Specific representative examples of the organosilicon compound represented by general formula (I) include methyltrimethoxysilane, methyltriethoxysilane, methyltrimethoxyethoxysilane,
Methyltriacetoxysilane, methyltripropoxysilane, methyltributoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, vinyltrimethoxysilane, vinyltriethoxysilane, vinyltriacetoxysilane, vinyltrimethoxyethoxysilane, phenyltrimethoxysilane , phenyltriethoxysilane, phenyltriacetoxysilane, γ-chloropropyltrimethoxysilane, γ-chloropropyltriethoxysilane, γ-chloropropyltriacetoxysilane,
3,3.3-trifluoropropyltrimethoxysilane,
γ-methacryloxypropyltrimethoxysilane, γ-
Aminopropyltrimethoxysilane, γ-aminopropyltriethoxysilane, γ-mercaptopropyltrimethoxysilane, γ-mercaptopropyltrimethoxyethoxysilane, γ-mercaptopropyltriethoxysilane, N-β-(aminoethyl)γ-amino Propyltrimethoxysilane, β-cyanoethyltriethoxysilane, methyltriphenoxysilane, chloromethyltrimethoxysilane, chloromethyltriethoxysilane, glycidoxymethyltrimethoxysilane, glycidoxymethyltriethoxysilane, α-glycidoxy Ethyltrimethoxysilane, α-glycidoxyethyltriethoxysilane, β-glycidoxyethyltrimethoxysilane, β-
Glycidoxyethyltriethoxysilane, α-glycidoxypropyltrimethoxysilane, α-glycidoxypropyltriethoxysilane, β-glycidoxypropyltrimethoxysilane, β-glycidoxypropyltriethoxysilane, γ -glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyl I-ribroboxysilane,
γ-Glycidoxypropyltributoxysilane, γ-Glycidoxypropyltrimethoxyethoxysilane, γ-
glycidoxypropyltriphenoxysilane, α-glycidoxybutyltrimethoxysilane, α-glycidoxybutyltriethoxysilane, β-glycidoxybutyl)
・Rime I xysilane, β-glycidoxybutyltriethoxysilane, γ-glycidoxybutyltrimethoxysilane, γ-glycidoxybutyltriethoxysilane, δ
-glycidoxybutyltrimethoxysilane, δ-glycidoxybutyltriethoxysilane, (3,4-epoxycyclohexyl)methyltrimethoxysilane, (3,4
-Epoxycyclohexyl)methyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyl Tripropoxysilane, β-
(3,4-Epoxycyclohexyl)ethyltributoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxyethoxysilane, β-(3,4-epoxycyclohexyl)ethyltriphenoxysilane, γ-
(3,4-epoxycyclohexyl)propyltrimethoxysilane, γ-(3,4-epoxycyclohexyl)
Propyltriethoxysilane, β-(3,4-epoxycyclohexyl)butyltrimethoxysilane, β-(3
, 4-epoxycyclohexyl)butyltriethoxysilane, triazyloxysilane, or triphenoxysilanes or their hydrolysates, and dimethyldimethoxysilane, phenylmethyldimethoxysilane, dimethyljethoxysilane, phenylmethylsilane, etc. Toxysilane, γ-chloropropylmethyldimethoxysilane, γ-chloropropylmethyljethoxysilane, dimethyldiacetoxysilane, γ-methacryloxypropylmethyldimethoxysilane, γ-methacryloxypropylmethyljethoxysilane, γ-mercaptopropylmethyldimethoxy Silane, γ-mercaptopropylmethyljethoxysilane, γ-aminopropylmethyldimethoxysilane, γ-aminopropylmethyljethoxysilane, methylvinyldimethoxysilane, methylvinyljethoxysilane, glycidoxymethylmethyldimethoxysilane, glycidoxy Ethylmethyljethoxysilane, α-glycidoxyethylmethyldimethoxysilane, α-glycidoxymethylmethyljethoxysilane, β
-Glycidoxyethylmethyldimethoxysilane, β-glycidoxyethylmethyljethoxysilane, α-glycidoxypropylmethyldimethoxysilane, α-glycidoxypropylmethyljethoxysilane, β-glycidoxypropylmethyldimethoxysilane , β-glycidoxypropylmethyljethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, γ-glycidoxypropylmethyljethoxysilane, γ-glycidoxypropylmethyldipropoxysilane, γ-glycid Xypropylmethyldibutoxysilane, γ-glycidoxypropylmethyldimethoxyethoxysilane, γ-glycidoxypropylmethyl, diphenoxysilane, γ-glycidoxypropylmethyldiacetoxysilane, γ-glycidoxypropylethyldimethoxy Silane, γ-glycidoxypropylethyljethoxysilane, γ-glycidoxypropylvinyldimethoxysilane, γ-glycidoxypropylvinyljethoxysilane, γ-glycidoxypropylphenyldimethoxysilane, γ-glycid Examples include dialkoxysilanes such as xyprobylphenyldiethoxysilane, diphenoxysilane or diacyloxysilanes, or hydrolysates thereof.

On the other hand, in the compound represented by general formula (II), which is another preferred silane coupling agent, R
3. Examples of R5 include the same examples as R1 in the general formula (I). Examples of R4R6 include the same examples as R2 in the above general formula (1). Also,
As the hydrolyzable group for Q, the same examples as for X in the general formula (I) can be mentioned. Further, C and e are each 0 or 1, and d and f are 0, 1 or 2, respectively. Furthermore, (c+d) and (e+f) are 0, 1, or 2, respectively. When d or f is 2, R4 and R6 may be of the same type or different types, respectively.

Moreover, Y is an organic group having 2 to 4 carbon atoms.

That is, Y is a functional group contained in the molecule with two Si atoms and a 5i-C bond, and the functional group contains a different atom other than carbon or hydrogen, such as an oxygen atom or a nitrogen atom. There is no problem either. Furthermore, within the range of 2 to 40 carbon atoms, the organic group may be chain or cyclic, and there is no problem even if oxygen atoms etc. are present as epoxy rings etc. In particular, when an oxygen atom is present as an epoxy ring or the like, it is preferable since it contributes as a functional group during curing.

A specific example of Y is CHC82CH2- C■13 CH3-CH2C
H2CH2C- H3 -C)h CHI CH2-0-C-0→CH2CH2
0←]-C-0-C1h C1h Cth-11j 0 (However, g is an integer from t to 4) 0 and the like.

Among the organosilicon compounds represented by the above general formula (I) or (II), organosilicon compounds containing an epoxy group or a glycidoxy group are particularly suitable for the purpose of improving low-temperature curability and hardness. Further, from the viewpoint of curing speed, ease of hydrolysis, etc., an alkoxy group or an alkoxyalkoxy group having 1 to 4 carbon atoms is preferably used as X and Q.

Among these organosilicon compounds and/or their hydrolysates, hydrolysates are preferred in order to lower the curing temperature and promote crosslinking.

Hydrolysis is produced by adding pure water or an acidic aqueous solution such as hydrochloric acid, acetic acid, or sulfuric acid and stirring.

Furthermore, the degree of hydrolysis can be easily controlled by adjusting the amount of pure water or acidic aqueous solution added. During hydrolysis, it is particularly preferable to add pure water or acidic aqueous solution in an amount equal to or more than 3 times the mole of the X group or Q group in -formation (I) or (n) from the viewpoint of accelerating curing.

During hydrolysis, alcohol and other substances are generated, so it is possible to hydrolyze without a solvent, but in order to make the hydrolysis more uniform, it is possible to mix the organosilicon compound and a solvent before hydrolysis. It is also possible. Depending on the purpose, it is also possible to remove an appropriate amount of the hydrolyzed alcohol etc. under heating and/or reduced pressure before use, and it is also possible to add an appropriate solvent afterwards.

These solvents include water, alcohols, esters, ethers, ketones, halogenated hydrocarbons or toluene,
Examples include aromatic hydrocarbons such as xylene, N,N-dimethylformamide, dimethylimidazolidinone, and the like. Moreover, these solvents can also be used as a mixed solvent of two or more types as required. Furthermore, depending on the purpose, it is possible to accelerate the hydrolysis reaction and further advance reactions such as precondensation by heating above room temperature, or to suppress precondensation, the hydrolysis temperature can be lowered to below room temperature. Needless to say, it is possible to do so.

The addition ratio of polyvinyl alcohol and crosslinking agent in the present invention should be appropriately optimized depending on the desired antifogging property and the substrate to which it is applied, especially the substrate on which the coating of the present invention is to be applied. If the heat resistance is 100'C or more, or if it has a heat resistance of more than 100'
Preferably it is 300 parts by weight. In particular, when both high surface hardness and antifogging functions are to be satisfied at the same time, polyvinyl alcohol should be added in an amount of 7.5 parts by weight per 10 parts by weight of the crosslinking agent component.
A range of 5 to 150 parts by weight is preferred.

In addition, when adding a solvent, the addition ratio should be optimized depending on the desired antifogging property, the applied substrate, the coating method, etc., but the ease of preparing the coating composition should be Considering that 50wt% in the composition
It is preferable that it is above.

Performance can be improved and modified by adding other components other than the above-mentioned components to the coating of the present invention.

For example, as a surface hardness improver, addition of particulate silica or the like is preferably applied.

It is also preferable to add dyes and pigments within a range that does not impair transparency, and it is also possible to dye the cured film.

Further, in order to improve weather resistance and adhesion, it is preferable to use various epoxy resins, urethane resins, and acrylic resins. Among them, aliphatic epoxy resins are particularly preferred since their improvement effects can be greatly improved.

Furthermore, various surfactants are used in the coating composition used to form the film of the present invention in order to improve the flow during application, improve the smoothness of the paint film, and lower the coefficient of friction on the surface of the paint film. In particular, block or graft polymers of dimethylpolysiloxane and alkylene oxide, and fluorine-based surfactants are effective. We can also disperse dyes and pigments and fillers, dissolve organic polymers, and color paint films.
It is also easily possible to improve its practicality as a coating agent, such as by improving its applicability, adhesion to substrates, and physical properties.

Furthermore, it is easily possible to add an ultraviolet absorber for the purpose of improving weather resistance or an antioxidant as a method for improving heat deterioration resistance.

Further, various curing agents can be used in combination for the purpose of accelerating curing and enabling low-temperature curing. As the curing agent, various epoxy resin curing agents or various organosilicon resin curing agents are used. Specific examples of these curing agents include various organic acids and their acid anhydrides, nitrogen-containing organic compounds, various metal complex compounds, metal alkoxides, and various salts such as alkali metal organic carboxylates and carbonates. Can be mentioned. It is also possible to use a mixture of two or more of these curing agents.

Among these curing agents, the stability of the coating composition,
The aluminum chelate compounds shown below are particularly useful from the viewpoint of whether or not the coating film is colored after coating.

The aluminum chelate compound mentioned here is, for example, -
Formation A1. It is an aluminum chelate compound represented by UnT3-4.

However, in the formula, U represents OL (L is a lower alkyl group having 1 to 6 carbon atoms), and T is a ligand derived from a compound represented by the general formula (lower alkyl group having 1 to 6 carbon atoms). , and -Formation%Formula% is also at least one substituent selected from a ligand derived from a compound represented by a lower alkyl group having 1 to 6 carbon atoms, and n is 0, 1 or 2.

Various compounds can be used as the aluminum chelate compound represented by AIUnT3□, but aluminum acetylacetonate, aluminum bis Ethyl acetoacetate monoacetylacetonate, aluminum di-n-butoxide monoethyl acetoacetate, aluminum di-1so-
Propoxide monomethyl acetoacetate and the like. It is also possible to use a mixture of two or more of these.

The film of the present invention is obtained by applying the above coating composition and then curing the coating composition.
Curing is performed by heat treatment. Note that the heating temperature can be used over a fairly wide range, and sufficiently good results can be obtained at 50 to 250°C.

The cured film obtained in the above manner has high hardness, adhesion, durability, and chemical resistance, but its antifogging properties are insufficient. Apply the immersion treatment described below. The immersion treatment here is 0.01w
0.0% in an acidic aqueous solution of t% or more and 40wt% or less. It is immersed for 5 minutes or more and 5 hours or less. 0.01w1
% or 0° for less than 5 minutes, a sufficient antifogging effect cannot be obtained. Furthermore, if the concentration exceeds 40w1% or the treatment time exceeds 5 hours, the membrane performance, especially the membrane adhesion, will be degraded. As the acidic aqueous solution, various aqueous solutions can be used, and an aqueous solution with a pH of 5 or less is preferably used.

Among them, I-I CI is most preferably used because it is easy to handle. In addition, the aqueous solution concentration and immersion treatment time are usually 0.01 wt% to 20 wt%, and 0.01 wt% to 20 wt%. It is preferable to carry out within the range of 5 minutes to 90 minutes. In addition, from the viewpoint of shortening treatment time and treatment effect, the aqueous solution to be immersed is 20%
It is preferably used at temperatures above ℃. These optimal processing conditions are appropriately determined within the above ranges experimentally depending on the required antifogging performance, film composition, etc.

By the above immersion treatment, the antifogging film of the present invention can have a spectral intensity difference of 0.3 or more between the horizontal component and the vertical component of the stretching vibration of hydroxyl groups within 1 μm from the surface. The surface here refers to the surface exposed to the outside air, where dew condensation generally occurs, and is particularly important for the function of an anti-fog coating. In addition,
Even in the film at a distance of more than 1 μm from the surface, from the perspective of improving antifogging properties, it is important that the difference in spectral intensity between the horizontal and vertical components of the stretching vibrations of hydroxyl groups is 0.0. It is preferable that it is 3 or more.

The horizontal and vertical components of the hydroxyl group were measured using A and T of a commercially available FT-iR (Fourier transform infrared spectrophotometer).
This can be carried out using an R device (total reflection absorption measurement device), for example, FTS-15E/D manufactured by Biorad Digilab.
It is possible to measure the polarized light (P, S) spectrum using a type of device. So-called P-polarized light excites bonds perpendicular to the sample surface, and S-polarized light excites bonds parallel to the sample surface. Therefore, the intensity of absorption bands corresponding to these becomes strong, making it possible to evaluate and obtain knowledge about orientation, and to measure each component.

The above measurement is carried out in the absorption band of 3,300 cm to 3,400 cm, which is the absorption band of the stretching movement of the hydroxyl group, because it has a strong absorption and there is no other absorption that would be a hindrance.

Furthermore, in the present invention, the "strength difference" between the horizontal and vertical components of the stretching vibration of the hydroxyl group is 1410 cm-' which is the bending vibration spectrum of the methylene bond.
It is expressed with the peak of , means the difference between the respective quotients in the horizontal and vertical components.

The thickness of the antifogging film of the present invention is preferably 1 μm or more. That is, when the thickness is less than 1 μm, the antifogging effect is poor and there is a tendency that only a product with low practicality can be obtained. On the other hand, the film thickness of 1 μm or more is not particularly limited and can be used in the form of a film or sheet, but from the viewpoint of mechanical properties, it is preferably 500 μm or less and used by coating on various base materials. . In particular, from the viewpoint of workability, the thickness is preferably 200 μm or less.

The anti-fog coating of the present invention can be applied to various base materials, and there are no particular restrictions on the base material as long as it does not impair the characteristics of the present invention; Substrates that have been widely recognized include plastics, inorganic glasses, transparent ceramics, metals, and mirror materials, and are particularly effective when applied to inorganic glass surfaces because of their good adhesion properties.

Further, as examples of great practical value, the coating of the present invention is preferably used for plastic and inorganic glass lenses, bathroom windows, mirrors, automobile or train windows, and the like.

In addition, various methods commonly known in the art can be used to apply the coating to the object, such as brush coating, dip coating, spin coating, flow coating, spray coating, roll coating, curtain flow coating, etc. It is.

After applying the anti-fog film to the base material using the method described above, it is further heat-treated to form a film that not only has the desired anti-fog property but also has abrasion resistance. can.

Further, in order to improve the adhesion to the base material, it is also possible to pre-treat the base material with various primers, activated gas treatment, or chemical treatment with acids, bases, etc.

The film of the present invention can be colored with dyes without any loss of its properties, and these have very high added value.

[Example code] Hereinafter, the present invention will be explained in more detail with reference to Examples.

Example 1 (1) Adjustment of γ-glycidoxypropyltrimethoxysilane hydrolyzate 236 g of γ-glycidoxypropyltrimethoxysilane was charged into a reactor equipped with a rotor, and the liquid temperature was brought to 10°C. 0.0↓ while stirring with a magnetic stirrer.
54 g of normal hydrochloric acid aqueous solution was gradually added dropwise. After the dropwise addition was completed, cooling was stopped to obtain hydrolyzed scraps of γ-glycidoxypropyltrimethoxysilane.

(2) Adjustment of paint polyvinyl alcohol (Nippon Gosei Chemical Industry ■ product, AL
-06, average degree of polymerization 6001 degree of saponification 91°0~94.
After weighing 532 g of a 27.1 wt% aqueous solution of 0 mol %) into a beaker, 62.4 g of the γ-glycidoxypropyltrimethoxysilane hydrolyzate and 107 g of 1,4-dioxane were added under stirring. 6g, methanol 52.
4g, dimethylimidazolidine 66. 63 g, 3.6 g of aluminum acetylacetone as a catalyst, and 0.6 g of a fluorine-based surfactant were mixed and dissolved to prepare a paint.

(3) Formation of antifogging film The paint prepared in (2) above was coated on a float glass plate, and after 20 minutes, it was dried in a hot air dryer at 140°C for 2 hours. Next, it was immersed in a 2vt% HCA' aqueous solution at 40°C and treated for 10 minutes. Thereafter, it was dried to obtain a glass substrate having an antifogging film.

(4) Evaluation The antifogging film obtained in (3) above had a film thickness of ↓3 μm, and there was no coating unevenness. Furthermore, the transparency was also good, with a total light transmittance of 93%.

In addition, apply 100 pieces of cellophane adhesive tape (product name:
Cellotape (Nichiban ■ product) was strongly applied and then rapidly peeled off in a 90 degree direction, but no peeling of the coating was observed and good adhesion was observed.

In addition, as an antifogging test, I breathed on the paint film, but it did not fog.

Furthermore, when the pencil hardness was measured using JTS K5400, it was 2H, indicating excellent surface hardness.

Comparative Example 1 Similar evaluations and measurements were performed on the sample that was not subjected to the treatment with the 2W1% HC1 aqueous solution at 40° C. in item (3) of Example 1. As a result, the appearance, adhesion, and surface hardness were good, but fogging occurred due to exhalation, and the antifogging property was poor.

[Effect of the invention] The antifogging film of the present invention has the following characteristics.

(1) Excellent antifogging properties, and the antifogging effect is maintained.

(2) Excellent durability such as water resistance.

(3) It has good adhesion to the base material.

(4) High surface hardness.

Claims (1)

[Claims] (1) A step of applying a coating composition mainly composed of the following components A and B, followed by a step of curing by heating, and further immersed in an acidic aqueous solution of 0.01 wt% or more and 40 wt% or less for 0.5 minutes or more, 1. A method for producing an antifogging film, comprising a step of immersion for 5 hours or less. Component A: Polyvinyl alcohol with saponification degree of 70 mol% or more and average degree of polymerization of 300 or more Component B: Crosslinking agent