JP6794151B2 - Coating film, method for producing coating film, and coating composition - Google Patents

Description

The present invention relates to a coating film, a method for producing a coating film, and a coating composition.

In recent years, awareness of the environment has increased due to the global warming phenomenon, and new energy systems that do not generate warming gases such as carbon dioxide are attracting attention. Among them, solar cells are attracting particular attention because of their excellent safety and ease of handling.

In order to increase the output of the solar cell, a method of forming an antireflection film on the surface of the solar cell cover glass to increase the transmittance is known.

In addition, since solar cells are used outdoors for a long period of time, there is a problem that the output is reduced due to the accumulation of pollutants. In order to solve this problem, a method of forming an antifouling film on the surface of the solar cell cover glass is known.

For example, Patent Document 1 discloses an antireflection film having excellent antifouling properties, which forms pores by using beaded silica.

Further, Patent Document 2 discloses an antireflection film having excellent antifouling property, which forms pores by burning off organic components in a coating film.

International Publication No. 2013/11783 Japanese Unexamined Patent Publication No. 2015-108061

In general, an antireflection film having antifouling property often forms pores inside the coating film and also forms a fine uneven structure on the film surface. Since the hydrophilic film having a fine surface uneven structure has a cleaning function with rainwater and the contact area of pollutants such as sand dust is reduced, the antifouling property due to the dust adhesion prevention function can be exhibited even under drying.

On the other hand, in the manufacturing process of the solar cell module, the tape may be laminated with the tape attached to the surface of the cover glass. However, when the tape adhesive component adheres to the coating film having the above-mentioned surface fine uneven structure, there is a problem that the adhesive component permeates into the fine pores on the film surface and the tape adhesion mark cannot be easily removed.

Poor tape adhesion is presumed to be due to the anchor effect due to the fine uneven structure on the film surface, and smoothing the film surface makes it possible to easily remove tape adhesion marks, but with smooth films, contact with contaminants such as dust Since the area becomes large, there is a problem that the dust adhesion prevention function is deteriorated. That is, it has been difficult to achieve both prevention of tape adhesion and dust adhesion prevention with conventional techniques.

Therefore, an object of the present invention is to provide an antireflection coating film which has good antireflection property and also has both good antireflection property for dust adhesion and antireflection property for tape.

As a result of diligent studies to solve the above-mentioned problems of the prior art, the present inventors have pores inside the film, the pore ratio is 20% or more and less than 50%, and the film surface has an uneven structure. , It was found that a coating film having 1 to 15 irregularities with a height difference of 10 nm to 100 nm on a 2 μm line on the film surface has good antireflection performance, dust adhesion prevention property, and tape adhesion prevention property. , The present invention has been completed.

That is, the present invention is as follows.
[1]
A coating film having pores inside the film and an uneven structure on the surface of the film.
The vacancy rate is 20% or more and less than 50%.
A coating film in which the number of irregularities with a height difference of 10 nm to 100 nm on a 2 μm line of the film surface observed by AFM measurement is 1 to 15.
[2]
The coating film according to [1], wherein the static contact angle with water at 25 ° C. is less than 25 ° C.
[3]
The coating film according to [1] or [2], which contains the metal oxide particles (A).
[4]
The coating film according to any one of [1] to [3], which is formed on the surface of a cover glass for a solar cell.
[5]
The method for producing a coating film according to any one of [1] to [4].
A method for producing a coating film, which comprises a step of applying a coating composition containing metal oxide particles (A), polymer particles (B), and a hydrolyzable silicon compound (C) to a substrate.
[6]
The method for producing a coating film according to [5], further comprising a step of sintering the coating composition at a temperature of 500 ° C. or higher after the coating step.
[7]
The coating composition for the coating film according to any one of [1] to [4].
Contains metal oxide particles (A), polymer particles (B) and hydrolyzable silicon compound (C).
The number average particle diameter of the metal oxide particles (A) is 1.0 nm to 100 nm, the number average particle diameter of the polymer particles (B) is 10 nm to 100 nm, and the metal oxide particles (A). A coating composition in which the sum of the number average particle diameter of the polymer particles (B) and the number average particle diameter of the polymer particles (B) is 50 nm to 150 nm.
[8]
The coating composition according to [7], wherein the mass ratio (A) / (B) of the metal oxide particles (A) to the polymer particles (B) is 0.05/1 or more and 1/1 or less. ..
[9]
In [7] or [8], the mass ratio (C) / (B) of the hydrolyzable silicon compound (C) to the polymer particles (B) is 0.1 / 1 or more and 1/1 or less. The coating composition described.
[10]
The polymer particles (B) are obtained by polymerizing a hydrolyzable silicon compound (b1) and a vinyl monomer having a secondary and / or tertiary amide group in the presence of water and an emulsifier. The coating composition according to any one of [7] to [9], which comprises polymer particles.
[11]
The hydrolyzable silicon compound (b1) contained in the polymer particles (B) is a hydrolyzable silicon compound (b3) containing four or more hydrolyzable functional groups, and the hydrolyzable silicon compound (b1) in the polymer particles (B). The coating composition according to [10], wherein the hydrolyzed condensate of the hydrolyzable silicon compound (b3) has a mass ratio of 20% or more and 50% or less.

According to the present invention, a coating film capable of imparting good antireflection performance, dust adhesion prevention property, and tape adhesion prevention property to a substrate can be obtained.

Hereinafter, a mode for carrying out the present invention (hereinafter, referred to as “the present embodiment”) will be described in detail.
The following embodiments are examples for explaining the present invention, and are not intended to limit the present invention to the following contents. The present invention can be appropriately modified and implemented within the scope of the gist thereof.
In addition, in this specification, "(meth) acrylate" means both acrylate and the corresponding methacrylate. Further, "(meth) acrylic acid" means both acrylic acid and methacrylic acid corresponding thereto.

[Coating film]
The coating film of the present embodiment is a coating film having pores inside the film and having an uneven structure on the surface of the film, and has a pore ratio of 20% or more and less than 50%, and is an atomic force microscope. The number of irregularities with a height difference of 10 nm to 100 nm on the 2 μm line of the film surface observed by AFM) measurement is 1 to 15. With such a structure, the coating film of the present embodiment can impart good antireflection performance, dust adhesion prevention property, and tape adhesion prevention property to the base material. A coating film that satisfies both the porosity and the unevenness of the film surface can be obtained by selecting a raw material for the coating composition and devising a method for producing the coating composition, as described later.

The coating film of the present embodiment preferably contains the metal oxide particles (A) described later from the viewpoint of adjusting the uneven structure of the coating film surface and the hydrophilicity of the coating film surface.

The base material forming the coating film of the present embodiment is not limited to the following, and examples thereof include glass, resin, mirror, and building material.

(Voids in the coating film)
The porosity of the coating film of the present embodiment is 20% or more and less than 50%, preferably 25% or more and less than 50%, and more preferably 30% or more and less than 50%.
When the pore ratio is 20% or more, excellent antireflection performance is obtained in the coating film of the present embodiment, and when the pore ratio is less than 50%, sprayed dust and the like and adhered dirt are obtained. Even when the cloth is wiped off, the occurrence of scratches and cracks is suppressed.

In order to keep the porosity within the above range, it is preferable to adjust the size and amount of the raw materials used in the coating composition described later. For example, metal oxide particles (A), polymer particles (B), and hydrolyzable silicon compound (C) may be used as raw materials, and their sizes and amounts will be described later.

The porosity of the coating film of the present embodiment can also be determined by direct observation with a nitrogen adsorption method or an electron microscope, but in the present specification, it is obtained by measuring the refractive index of the coating film as follows. The porosity to be obtained will be described.
For the base material on which the coating film is formed, the reflectance for each wavelength of 230 to 800 nm is measured using a reflection spectroscopic film thickness meter (Otsuka Electronics model: FE-3000).
Next, the intensity of the reflected light interfering with the coating film and the substrate such as the glass substrate for each wavelength of 230 to 800 nm on the coating film side is measured, and the measured values are fitted by the least squares method to coat the coating. Obtain the refractive index and film thickness (nm) of the film.
Further, the porosity is obtained from the refractive index of the material forming the coating film and the refractive index of air. For example, when the coating film is made of silica (refractive index 1.46), the porosity is calculated from the following formula.
(Vacancy rate) = (1.46- (refractive index of coating film)) /0.46 × 100
Since all or part of the pores are filled with air, the refractive index thereof is extremely close to 1.

(Concave and convex structure on the surface of the coating film)
In the coating film of the present embodiment, the number of irregularities having a height difference of 10 nm to 100 nm on the 2 μm line of the film surface observed by AFM measurement is 1 to 15, preferably 2 to 12, and 3 to 10. Is more preferable.
When the number of unevenness having the height difference is one or more, the contact area between the pollutant and the coating film becomes small, and the pollutant can be easily removed.
Further, when the number of unevenness having the above-mentioned height difference is 15 or less, the adhesive component of the tape is less likely to enter between the unevenness, and the removal becomes easy.
In order to keep the number of irregularities having the height difference within the above range, the average particle diameter and amount of the metal oxide particles (A) and the average particle diameter and amount of the polymer particles (B), which will be described later, may be adjusted. ..
The height difference of the unevenness on the 2 μm line on the surface of the coating film and the number of unevenness can be calculated from the AFM measurement image at an arbitrary position on the coating film. Specific methods for AFM measurement include the following.
Any part of the surface of the coating film is observed with an atomic force microscope (AFM; Dimension Icon manufactured by Bruker) under the following conditions in a field of view of 2 μm × 2 μm. With respect to the obtained surface image, 10 line profiles having a length of 2 μm are extracted in parallel at intervals of 0.2 μm, and the number of irregularities having a height difference of 10 to 100 nm is counted and averaged.
<AFM observation conditions>
Observation mode: Tapping mode Cantilever: Si rectangular cantilever with a length of 125 μm (without contamination and wear at the tip of the probe; AR-10T manufactured by Nano World, etc.)
Spring constant: about 40 N / m

A coating film that satisfies both the porosity and the unevenness of the film surface can be obtained, for example, by selecting the raw material of the coating composition and by devising various conditions in the production of the coating composition as described later. it can.

(Water contact angle on the surface of the coating film)
The static contact angle of the coating film surface with water at 25 ° C. is preferably less than 30 °, more preferably less than 25 °, still more preferably less than 15 °.
When the water contact angle is in the above range, it tends to be easy to remove pollutants from rainwater or the like.
The water contact angle on the surface of the coating film can be measured by the method described in Examples described later, for example, depending on the amount of metal oxide particles (A) described later, the sintering temperature at the time of manufacturing the coating film, and the like. Can be adjusted.

(Film thickness of coating film)
The film thickness of the coating film of the present embodiment is preferably 50 nm or more and 1000 nm or less, more preferably 80 nm or more and 200 nm or less, and 80 nm or more and 150 nm or less from the viewpoint of producing sufficient antireflection performance and transparency. Is more preferable.
When the film thickness is 50 nm or more, the strength of the coating film tends to be sufficiently maintained, and when the film thickness is 1000 nm or less, a coating film having uniform antireflection performance tends to be obtained.
In order to obtain a coating film having a film thickness in the above range, the solid content concentration of the coating composition for forming the coating film may be adjusted, and the solid content concentration is 0.1 to 10% by mass. Is preferable, more preferably 0.5 to 7% by mass, and even more preferably 1 to 6% by mass.
It is also possible to adjust the film thickness of the coating film by adjusting the coating speed on the coating machine side.
The film thickness of the coating film can be calculated by measuring the cross section with an electron microscope, measuring the reflected light due to the interference of the thin film with an optical ellipsometer or a reflection spectroscopic film thickness meter, and using the measured value. is there.

[Manufacturing method of coating film]
The method for producing the coating film of the present embodiment is not particularly limited, but from the viewpoint of stable coating film formation, the metal oxide particles (A), the polymer particles (B), and the hydrolyzable silicon compound (C). ), It is preferable to include a step of applying the coating composition containing the above to the substrate.

The method of applying the above coating composition to the substrate is not particularly limited, and for example, a spray spraying method, a flow coating method, a roll coating method, a brush coating method, a dip coating method, a spin coating method, a screen printing method, and casting. Examples include the method, the gravure printing method, and the flexographic printing method.

Further, the coating film of the present embodiment is a step of applying a coating composition containing metal oxide particles (A), polymer particles (B), and a hydrolyzable silicon compound (C) to a substrate. After that, it is preferable to include a step of sintering the coating composition at a temperature of 500 ° C. or higher.
The sintering temperature is more preferably 500 ° C. or higher and 800 ° C. or lower, and further preferably 600 ° C. or higher and 750 ° C. or lower. Further, it may be sintered by performing treatments such as ultraviolet irradiation of a high-pressure mercury lamp at the same time or in series.
By sintering at the above temperature, the organic matter of the polymer particles (B) is decomposed, so that the water contact angle of the coating film tends to decrease, and the antifouling property tends to be further improved.
Further, by sintering at the above temperature, the metal oxide particles (A) are partially melted, and the organic matter of the polymer particles (B) tends to be decomposed, and as a result, vacancies are likely to be generated inside the film. The antireflection performance tends to be further improved by lowering the refractive index.
Further, during sintering, when the metal oxide particles (A) and the hydrolyzable silicon compound (C) around the polymer particles (B) are rapidly condensed and the entire coating film shrinks, the polymer It is presumed that the particles (B) relax the shrinkage of the coating film, thereby suppressing the pores from being crushed and coming into contact with the base material, and the exposure of the pores on the surface of the coating film. Therefore, it is possible to improve the adhesion to the base material and the durability to prevent deterioration of the coating film due to water permeation from the outside.

[Coating composition]
The coating composition preferably contains the metal oxide particles (A), the polymer particles (B), and the hydrolyzable silicon compound (C). Further, the number average particle diameter of the metal oxide particles (A) is 1.0 nm to 100 nm, the number average particle diameter of the polymer particles (B) is 10 nm to 100 nm, and the metal oxide particles (A). The sum of the number average particle diameter of the polymer particles (B) and the number average particle diameter of the polymer particles (B) is preferably 50 nm to 150 nm. Here, the number average particle diameters of the metal oxide particles (A) and the polymer particles (B) can be measured by the method described in Examples described later. Further, these number average particle diameters can be controlled in the above range by, for example, the concentration of the raw material or the emulsifier.
By combining the metal oxide particles (A) in the above range and the polymer particles (B), the height difference of the unevenness on the surface of the coating film can be adjusted to a desired range of the present embodiment.

In the present embodiment, the mass ratio (A) / (B) of the metal oxide particles (A) to the polymer particles (B) is preferably 0.05/1 or more and 1/1 or less, more preferably. It is preferably 0.05/1 or more and 0.5 / 1 or less, and more preferably 0.1 / 1 or more and 0.5 / 1 or less.
By combining the metal oxide particles (A) in the above range and the polymer particles (B), the number of irregularities on the surface of the coating film can be adjusted to a desired range in the present embodiment.

In the present embodiment, the mass ratio (C) / (B) of the hydrolyzable silicon compound (C) to the polymer particles (B) is preferably 0.1/1 or more and 1/1 or less. It is more preferably 0.2 / 1 or more and 0.8 / 1 or less, and further preferably 0.3 / 1 or more and 0.7 / 1 or less.
By combining the polymer particles (B) in the above range with the hydrolyzable silicon compound (C), the mechanical strength of the coating film can be improved.
The mass of the hydrolyzable silicon compound (C) is assumed to be the mass in terms of SiO ₂ after the hydrolyzable silicon compound (C) is hydrolyzed and condensed.

<Metal oxide particles (A)>
The metal oxide particles (A) are not particularly limited, and examples thereof include oxides such as silicon, aluminum, titanium, zirconium, zinc, tin, indium, gallium, germanium, antimony, and molybdenum. Silicon oxide is particularly preferable from the viewpoint of optical properties and durability.
Specific examples of the silicon oxide particles are not limited to the following, but for example, "Snowtex-OXS (registered trademark)" manufactured by Nissan Chemical Industries, Ltd. and "Snowtex-O (registered trademark)" manufactured by Nissan Chemical Industries, Ltd. Examples thereof include "Snowtex-OL (registered trademark)" and "Snowtex-OYL (registered trademark)" manufactured by the same company.

<Polymer particles (B)>
The polymer constituting the polymer particles (B) is not limited to the following, but for example, a polyurethane-based polymer, a polyester-based polymer, a poly (meth) acrylate-based polymer, a poly (meth) acrylate-silicone-based copolymer, and the like. Alcohol adducts of polyvinyl acetate-based, polybutadiene-based, polyvinyl chloride-based, chlorinated polypropylene-based, polyethylene-based, polystyrene-based, polystyrene- (meth) acrylate-based copolymer, rosin-based derivative, and styrene-maleic anhydride copolymer Examples thereof include polymers composed of.

From the viewpoint of the strength of the coating film of the present embodiment, the polymer particles (B) are a hydrolyzable silicon compound (b1) and a vinyl compound having a secondary and / or tertiary amide group (hereinafter, simply "vinyl compound"). , Also referred to as "vinyl compound (b2)") is preferably obtained by polymerizing.
Further, the polymer particles (B) are a hydrolyzable silicon compound (b1) in the presence of water and an emulsifier, and a vinyl compound containing a vinyl compound (b2) having a secondary and / or tertiary amide group. It is more preferable that it is obtained by polymerization.

The polymer particles (B) are a copolymer obtained by polymerizing the hydrolyzable silicon compound (b1) and the vinyl compound (b2), and the hydrolyzable silicon compound (b1) and the vinyl compound (b2), respectively. It may be either a mixture of polymerized homopolymers or a composite, or a combination thereof.

The hydrolyzable silicon compound (b1) constituting the polymer particles (B) is not limited to the following, and is, for example, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, and tetraisopropoxy. Tetraalkoxysilanes such as silane, tetra-n-butoxysilane; methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyl Trimethoxysilane, isopropyltriethoxysilane, n-butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane , Vinyl trimethoxysilane, vinyl triethoxysilane, allyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxy. Silane, 3,3,3-trifluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxy Silane, 2-hydroxyethyltriethoxysilane, 2-hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-Mercaptopropyltriethoxysilane, 3-Isocyanatopropyltrimethoxysilane, 3-Isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3) , 4-Epylcyclohexyl) ethyltrimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acrylicoxypropyltrimethoxysilane, 3- (meth) acrylicoxypropyltriethoxysilane, 3- (Meta) acryloyloxypropyltri n-propoxysilane, 3- (meth) acryloyloxypropyltriisopropo Trialkoxysilanes such as xysilane, 3-ureidopropyltrimethoxysilane, 3-ureidopropyltriethoxysilane; dimethyldimethoxysilane, dimethyldiethoxysilane, diethyldimethoxysilane, diethyldiethoxysilane, di-n-propyldimethoxysilane, Di-n-propyldiethoxysilane, diisopropyldimethoxysilane, diisopropyldiethoxysilane, di-n-butyldimethoxysilane, di-n-butyldiethoxysilane, di-n-pentyldimethoxysilane, di-n-pentyldiethoxy Silane, di-n-hexyldimethoxysilane, di-n-hexyldiethoxysilane, di-n-heptyldimethoxysilane, di-n-heptyldiethoxysilane, di-n-octyldimethoxysilane, di-n-octyldi Dialkoxysilanes such as ethoxysilane, di-n-cyclohexyldimethoxysilane, di-n-cyclohexyldiethoxysilane, diphenyldimethoxysilane, diphenyldiethoxysilane, 3- (meth) acryloyloxypropylmethyldimethoxysilane; trimethylmethoxysilane , Monoalkoxysilanes such as trimethylethoxysilane.

As the hydrolyzable silicon compound (b1) described above, only one type may be used alone, or two or more types may be mixed and used.

Among the hydrolyzable silicon compounds (b1) contained in the polymer particles (B), the hydrolyzable silicon compound (b3) containing four or more hydrolyzable functional groups; hereinafter, simply "tetraalkoxysilanes". The mass ratio of the hydrolyzed condensate of () is preferably 20% or more and 50% or less, and more preferably 25% or more and 40% or less with respect to the solid content of the entire polymer particles (B).
Further, it is more preferable that the hydrolyzed condensate of the tetraalkoxysilanes is present in the outermost layer of the polymer particles (B). The presence of the hydrolyzed condensate in the outermost layer makes the polymer particles (B) stronger.
By using the polymer particles (B), deformation of the particle shape when sintered at a temperature of 500 ° C. or higher tends to be suppressed, and the height difference of the unevenness on the surface of the coating film and the number of irregularities are shown. It becomes possible to control within a desired range of the embodiment.

Further, among the hydrolyzable silicon compounds (b1), when used in combination with phenyltrimethoxysilane, phenyltriethoxysilane, diphenyldimethoxysilane, etc., which are silicon alkoxides having a phenyl group, polymerization in the presence of water and an emulsifier It is preferable because it has excellent stability.

The vinyl compound (b2) having a secondary amide group and / or a tertiary amide group is not limited to the following, but is, for example, N-methylacrylamide, N-methylmethacrylamide, N-ethylacrylamide, N. , N-dimethylacrylamide, N, N-dimethylmethacrylamide, N, N-diethylacrylamide, N-ethylmethacrylamide, N-methyl-N-ethylacrylamide, N-methyl-N-ethylmethacrylamide, N-isopropylacrylamide , N-n-propylacrylamide, N-isopropylmethacrylamide, Nn-propylmethacrylamide, N-methyl-Nn-propylacrylamide, N-methyl-N-isopropylacrylamide, N-acryloylpyrrolidin, N-methacrylamide Pyrrolidine, N-acrylloylpiperidin, N-methacryloylpiperidin, N-acrylloylhexahydroazepine, N-acryloylmorpholin, N-methacryloylmorpholin, N-vinylpyrrolidone, N-vinylcaprolactam, N, N'-methylenebisacrylamide, N, Examples thereof include N'-methylenebismethacrylamide, N-vinylacetamide, diacetoneacrylamide, diacetone metaacrylamide, N-methylolacrylamide, and N-methylolmethacrylamide.
The amide group of the vinyl compound (b2) is a secondary amide group and / or a tertiary amide group, but if it is a vinyl compound having a tertiary amide group, the silica particles in the obtained polymer particles (B) It is preferable because the hydrogen bond between the compound and the compound tends to be strengthened.
Among the vinyl compounds (b2) having a tertiary amide, N, N-diethylacrylamide has excellent polymerization stability in the presence of water and an emulsifier, and hydroxyl groups and silica particles of the polymerization product of the hydrolyzable silicon compound. It is more preferable because it tends to be possible to form a strong hydrogen bond with the hydroxyl group of.

Even if the polymerization product of the hydrolyzable silicon compound (b1) and the polymerization product of the vinyl compound (b2) having a secondary amide group and / or a tertiary amide group are compounded by hydrogen bonds and chemical bonds, Good.
It is preferable that the hydrolyzable silicon compound (b1) and the vinyl compound (b2) having a secondary amide group and / or a tertiary amide group are compounded by various bonds such as hydrogen bonds and chemical bonds. , The form and state of the bond are not limited in any way. Further, the above-mentioned compounding may be performed only in a part of the polymer particles (B).

Other vinyl compounds include, but are not limited to, (meth) acrylic acid ester, aromatic vinyl compound, vinyl cyanide compound; carboxyl group-containing vinyl compound, hydroxyl group-containing vinyl compound, and epoxy group. Examples thereof include compounds containing functional groups such as vinyl compounds and carbonyl group-containing vinyl compounds.
When a carboxyl group-containing vinyl compound and / or a hydroxyl group-containing vinyl compound is used, it becomes easy to control the hydrogen bonding force between the metal oxide particles (A) and other vinyl compounds, and the polymer particles (B) This is preferable because it tends to improve the water dispersion stability.

An emulsifier may be used in the synthesis of the polymer particles (B).
The emulsifier includes, but is not limited to, alkylbenzene sulfonic acid, alkyl sulfonic acid, alkyl sulfosuccinic acid, polyoxyethylene alkyl sulfate, polyoxyethylene alkyl aryl sulfate, polyoxyethylene distyrylphenyl ether sulfonic acid, and the like. Acid emulsifiers; alkali metal (Li, Na, K, etc.) salts of acidic emulsifiers, ammonium salts of acidic emulsifiers, anionic surfactants such as fatty acid soaps; alkyltrimethylammonium bromide, alkylpyridinium bromide, imidazolinium laurate, etc. Tertiary ammonium salt, pyridinium salt, imidazolinium salt type cationic surfactant; polyoxyethylene alkylaryl ether, polyoxyethylene sorbitan fatty acid ester, polyoxyethylene oxypropylene block copolymer, polyoxyethylene distyrylphenyl ether Examples thereof include nonionic surfactants such as, and reactive emulsifiers having a radically polymerizable double bond.
Among these emulsifiers, the reactive emulsifier having a radically polymerizable double bond has further improved water dispersion stability of the polymer particles (B), as well as water resistance, chemical resistance, and optical properties. It is preferable because it tends to be able to form a coating film having excellent strength and the like.

The reactive emulsifier having a radically polymerizable double bond is not limited to the following, for example, a vinyl compound having a sulfonic acid group or a sulfonate group, a vinyl compound having a sulfate ester group, an alkali metal salt or an ammonium salt thereof. A vinyl compound having a nonionic group such as polyoxyethylene; a vinyl compound having a quaternary ammonium salt can be mentioned.
The salt of the vinyl compound having a sulfonic acid group or a sulfonate group is not limited to the following, and is, for example, a group having a radically polymerizable double bond and being an ammonium salt, a sodium salt or a potassium salt of the sulfonic acid group. Alkyl group having 1 to 20 carbon atoms, alkyl ether group having 2 to 4 carbon atoms, polyalkyl ether group having 2 to 4 carbon atoms, aryl group having 6 or 10 carbon atoms and succinic acid group partially substituted with Compounds having a substituent selected from the group consisting of; Examples thereof include vinyl sulfonate compounds having a vinyl group to which a group which is an ammonium salt, a sodium salt or a potassium salt of a sulfonic acid group is bonded.

The compound having a succinic acid group partially substituted with a group which is an ammonium salt, a sodium salt or a potassium salt of a sulfonic acid group as a reactive emulsifier is not limited to the following, but for example, allyl. Examples include sulfosuccinate. Examples of commercially available products include Eleminor JS-2 (trade name) (manufactured by Sanyo Chemical Industries, Ltd.), Latemul S-120, S-180A or S-180 (trade name) (manufactured by Kao Corporation). ..
As a reactive emulsifier, an alkyl ether group having 2 to 4 carbon atoms or a polyalkyl ether group having 2 to 4 carbon atoms, which is partially substituted with a group which is an ammonium salt, a sodium salt or a potassium salt of a sulfonic acid group. The compound to have is not limited to the following, but for example, Aqualon HS-10 or KH-1025 (trade name) (manufactured by Daiichi Kogyo Seiyaku Co., Ltd.), Adecaria Soap SE-1025N or SR-1025 (trade name). (Manufactured by Asahi Denka Kogyo Co., Ltd.).

The vinyl compound having a nonionic group as a reactive emulsifier is not limited to the following, but is, for example, α- [1-[(allyloxy) methyl] -2- (nonylphenoxy) ethyl] -ω-hydroxy. Polyoxyethylene (trade name: Adecaria Soap NE-20, NE-30, NE-40, etc., manufactured by Asahi Denka Kogyo Co., Ltd.), Polyoxyethylene alkylpropenylphenyl ether (trade name: Aqualon RN-10, RN- 20, RN-30, RN-50, etc., manufactured by Daiichi Pharmaceutical Co., Ltd.).

The blending amount of the emulsifier described above is preferably 10 parts by mass or less, more preferably 0.001 parts by mass or more and 5 parts by mass or less, based on the total amount (100 parts by mass) of the polymer particles (B). ..

The polymer particles (B) are preferably synthesized by polymerizing the hydrolyzable silicon compound (b1), the vinyl compound (b2), and other vinyl compounds in the presence of a polymerization catalyst.

The polymerization catalyst of the hydrolyzable silicon compound can be appropriately selected depending on the components used for polymerization and the like, and is not limited to the following, but for example, hydrogen halides such as hydrochloric acid and sulfonic acid, acetic acid and trichloroacetic acid. , Trifluoroacetic acid, carboxylic acids such as lactic acid; sulfonic acids such as sulfuric acid and p-toluenesulfonic acid; alkylbenzenesulfonic acid, alkylsulfonic acid, alkylsulfosuccinic acid, polyoxyethylenealkylsulfate, polyoxyethylenealkylarylsulfate, polyoxy Acidic emulsifiers such as ethylene distyrylphenyl ether sulfonic acid; acidic or weakly acidic inorganic salts, acidic compounds such as phthalic acid, phosphoric acid and sulfuric acid; sodium hydroxide, potassium hydroxide, sodium methylate, sodium acetate, Tetramethylammonium chloride, tetramethylammonium hydroxide, tributylamine, diazabicycloundecene, ethylenediamine, diethylenetriamine, ethanolamines, γ-aminopropyltrimethoxysilane, γ- (2-aminoethyl) -aminopropyltrimethoxysilane Basic compounds such as; examples of tin compounds such as dibutyltin octylate, dibutyltin dilaurate.
Among these, acidic emulsifiers are preferable, and alkylbenzene sulfonic acid having 5 to 30 carbon atoms is more preferable, from the viewpoint of having an action as an emulsifier as well as a polymerization catalyst.

As the polymerization catalyst of the vinyl compound (b2) and other vinyl compounds, a radical polymerization catalyst that undergoes radical decomposition by heat or a reducing substance to cause addition polymerization of the vinyl compound is preferable.
Examples of such a polymerization catalyst include, but are not limited to, water-soluble or oil-soluble persulfates, peroxides, and azobis compounds.
More specifically, potassium persulfate, sodium persulfate, ammonium persulfate, hydrogen peroxide, t-butyl hydroperoxide, t-butyl peroxybenzoate, 2,2-azobisisobutyronitrile, 2,2- Examples thereof include azobis (2-diaminopropane) hydrogen peroxide and 2,2-azobis (2,4-dimethylvaleronitrile).
When it is desired to accelerate the polymerization rate or to polymerize at a low temperature of 70 ° C. or lower, it is preferable to use a reducing agent such as sodium bisulfite, ferrous chloride, ascorbate, or longalite in combination with a radical polymerization catalyst.

The amount of the polymerization catalyst compounded is preferably 0.001 part by mass or more and 5 parts by mass or less with respect to the total amount of the total vinyl compound used for the polymerization of the polymer particles (B).

The polymerization of the hydrolyzable silicon compound (b1) and the vinyl compound (b2) and other vinyl compounds can be carried out separately, but by carrying out the polymerization at the same time, hydrogen bonds or the like are formed between the two. It is preferable because micro organic and inorganic composites tend to be achieved.

As a method for emulsion polymerization of the polymer particles (B), a hydrolyzable silicon compound (b2), a vinyl compound (b2), and if necessary, other vinyl compounds are collectively used as they are or in an emulsified state. After being divided or continuously added dropwise into the reaction vessel, in the presence of the above-mentioned polymerization catalyst, preferably under a pressure from atmospheric pressure to 10 MPa if necessary, and under conditions of a reaction temperature of about 30 ° C. or higher and 150 ° C. or lower. There is a method of polymerizing with.
The pressure and reaction temperature may be changed as appropriate.

In emulsion polymerization, in order to grow or control the number average particle size of the polymer particles (B), the emulsion particles may be present in the aqueous phase in advance and polymerized by a seed polymerization method. As a result, polymer particles (B) having a more uniform number average particle diameter tend to be obtained. The seed (nucleus) substance can be appropriately selected according to the reaction conditions and the like.

The pH in the system in the polymerization reaction is preferably 1.0 or more and 10.0 or less, and more preferably 1.0 or more and 6.0 or less. In order to control the pH in such a range, it may be adjusted by using a pH buffer such as disodium phosphate, borax, sodium hydrogen carbonate, and ammonia.

As a method for obtaining the polymer particles (B), a hydrolyzable silicon compound and a vinyl compound are polymerized in the presence of water necessary for the polymerization, an emulsifier, and if necessary, a predetermined solvent, and then the polymerization product is produced. A method of adding water until it becomes an emulsion may also be adopted.

The polymer particles (B) preferably include a core layer and a shell layer.
The shell layer indicates the outermost layer, and the layer other than the shell layer is the core layer.

Further, the polymer particles (B) include a core layer and a shell layer, and include a component derived from a hydrolyzable silicon compound and a component derived from a vinyl compound having a secondary amide group and / or a tertiary amide group. It is preferable to include it.

In the polymer particles (B), components usually added to paints and molding resins, for example, thickeners, leveling agents, tinxing agents, defoamers, etc., are added to the polymer particles (B) depending on their use and usage. Freeze stabilizers, matting agents, cross-linking reaction catalysts, pigments, curing catalysts, cross-linking agents, fillers, anti-skinning agents, dispersants, wetting agents, light stabilizers, antioxidants, UV absorbers, rheology control agents, Contains defoamers, film-forming aids, rust preventives, dyes, plastics, lubricants, reducing agents, preservatives, anticorrosive agents, deodorants, anti-yellowing agents, antistatic agents or antistatic agents can do.

<Hydrolyzable silicon compound (C)>
The coating composition of the present embodiment further contains the hydrolyzable silicon compound (C) in distinction from the hydrolyzable silicon compound used for the polymerization of the polymer particles (B). For example, the hydrolyzable silicon compound remaining after the coating composition of the present embodiment is subjected to ultrafiltration to remove the polymer particles (B) can be referred to as a component (C), and the other can be referred to as a component (b1). It can be said.
A bond is formed by a condensation reaction and / or a hydrogen bond between the silanol group of the hydrolyzable silicon compound (C) and the hydroxyl group existing on the surface of the metal oxide particles (A) and / or the polymer particles (B). To do.
Therefore, the surface of the polymer particles (B) is covered with a condensate of the hydrolyzable silicon compound (C), and the pores formed by sintering the organic component of the polymer particles (B) in the above-mentioned sintering step. Can be suppressed from being crushed. Therefore, a high porosity and appropriate surface irregularities can be maintained.
As a result, the coating film of the present embodiment obtained from the above coating composition tends to have a higher mechanical strength.

The hydrolyzable silicon compound (C) is not limited to the following, but for example, tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetraisopropoxysilane, tetra-n-butoxysilane and the like. Tetraalkoxysilanes; methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxysilane, n-propyltrimethoxysilane, n-propyltriethoxysilane, isopropyltrimethoxysilane, isopropyltriethoxysilane, n-Butyltrimethoxysilane, n-butyltriethoxysilane, n-pentyltrimethoxysilane, n-hexyltrimethoxysilane, n-heptyltrimethoxysilane, n-octyltrimethoxysilane, vinyltrimethoxysilane, vinyltriethoxy. Silane, allyltrimethoxysilane, cyclohexyltrimethoxysilane, cyclohexyltriethoxysilane, phenyltrimethoxysilane, phenyltriethoxysilane, 3-chloropropyltrimethoxysilane, 3-chloropropyltriethoxysilane, 3,3,3-tri Fluoropropyltrimethoxysilane, 3,3,3-trifluoropropyltriethoxysilane, 3-aminopropyltrimethoxysilane, 3-aminopropyltriethoxysilane, 2-hydroxyethyltrimethoxysilane, 2-hydroxyethyltriethoxysilane , 2-Hydroxypropyltrimethoxysilane, 2-hydroxypropyltriethoxysilane, 3-hydroxypropyltrimethoxysilane, 3-hydroxypropyltriethoxysilane, 3-mercaptopropyltrimethoxysilane, 3-mercaptopropyltriethoxysilane, 3 -Isocyanatopropyltrimethoxysilane, 3-Isocyanatopropyltriethoxysilane, 3-glycidoxypropyltrimethoxysilane, 3-glycidoxypropyltriethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxy Silane, 2- (3,4-epoxycyclohexyl) ethyltriethoxysilane, 3- (meth) acrylicoxypropyltrimethoxysilane, 3- (meth) atacryloxypropyltriethoxysilane, 3- (meth) acryloyloxypropyl Tri-n-propoxysilane, 3- (meth) acryloyloxypropyltriisopropoxysilane, 3-ureidop Examples thereof include trialkoxysilanes such as lopiltrimethoxysilane and 3-ureidopropyltriethoxysilane.

The method for producing the coating composition is not limited to the following, but for example, a metal oxide (A), a polymer particle (B), and a hydrolyzable silicon compound (C) are added to water at room temperature. It can be produced by stirring for 3 hours, hydrolyzing (C) the hydrolyzable silicon compound, and then adding an alcohol and an additive.
It is preferable not to add alcohol first because the hydrolysis of the hydrolyzable silicon compound (C) can be accelerated and a smooth coating film can be easily formed. In addition, it is preferable to add alcohol later because the stability of the coating liquid is improved.
The alcohol is not limited to the following, and examples thereof include methanol, ethanol, propanol, isopropanol, butanol and the like.

Further, it is preferable to add an additive for improving the film forming property to the coating composition. Among the additives, it is particularly preferable to add an aprotic solvent. By adding an aprotic solvent, the repellency of the liquid during film formation is suppressed, and the coating film tends to be smooth. Examples of the aprotic solvent include, but are not limited to, acetone, acetonitrile, tetrahydrofuran, dimethyl sulfoxide, N, N-dimethylformamide and the like.

[Use]
Since the coating film of the present embodiment is excellent in dust adhesion prevention property, tape adhesion prevention property, water washability, and durability, it is used outdoors for a long period of time such as solar cells, mirrors for solar thermal power generation, building materials, and automobiles. It is suitable as an antifouling film for the base material. Further, it is particularly suitable as a coating film for a cover glass for a solar cell because it can impart functions excellent in antireflection characteristics and transparency. That is, the coating film of the present embodiment is preferably formed on the surface of the cover glass for a solar cell.

Hereinafter, the present embodiment will be described in more detail with reference to specific examples and comparative examples, but the present embodiment is not limited to the following examples and comparative examples.
Various physical properties and evaluations in the synthetic examples, examples and comparative examples described later were measured and evaluated by the following methods.

(1) Measurement of the number of irregularities on the surface of the coating film For the test plates manufactured in Examples and Comparative Examples described later, the irregularities on the surface of the coating film were measured with an atomic force microscope (AFM) in a field of view of 2 μm × 2 μm. I went there.
As the AFM, a Dimension Icon manufactured by Bruker was used.
The observation mode was the tapping mode.
As the cantilever, a rectangular cantilever made of Si having a length of 125 μm was used.
The cantilever is commercially available as AR-10T from Nano World, and the spring constant is about 40 N / m.
The cantilever used was new and free from contamination and wear at the tip of the probe.
From the obtained surface image, 10 line profiles having a length of 2 μm were extracted in parallel at intervals of 0.2 μm, and the number of irregularities having a height difference of 10 to 100 nm was counted and averaged.

(2) Measurement of Pore Ratio and Film Thickness For the test plates manufactured in Examples and Comparative Examples described later, a reflection spectroscopic film thickness meter (Otsuka Denshi model: FE-3000) was used for each wavelength of 230 to 800 nm. The reflectance was measured.
Next, the intensity of the reflected light interfering with the glass substrate and the coating film at each wavelength of 230 to 800 nm on the coating film side is measured, and the measured values are fitted by the least squares method to obtain the refractive index of the coating film. And the film thickness (nm) were determined.
Further, the refractive index of air was set to 1, the refractive index of silica was set to 1.46, and the porosity was calculated from the following formula.
(Vacancy rate) = (1.46- (refractive index of coating film)) /0.46 × 100

(3) Measurement of Number Average Particle Diameter The number average particle diameter of the polymer particles in the coating composition was evaluated using a dynamic light scattering type particle size distribution measuring device UPA-UZ152 (manufactured by Nikkiso Co., Ltd.).

(4) Measurement of Total Light Transmittance With respect to the test plates manufactured in Examples and Comparative Examples described later, the total light transmittance of 380 to 1100 nm was measured using a spectromissometer ST-100 manufactured by AOPTEK.
If the total light transmittance is 1.5% or more higher than the total light transmittance of the test plate (glass) without the coating film, it is judged that the test plate (glass) has antireflection performance.

(5) Measurement of water contact angle With respect to the test plates manufactured in Examples and Comparative Examples described later, drops of deionized water (1.0 μL) were placed on the surface of the coating film, left at 20 ° C. for 10 seconds, and then in Japan. The initial contact angle was measured using a CA-X150 type contact angle meter manufactured by Kyowa Interface Science. It was evaluated that the smaller the contact angle of water with respect to the coating film, the higher the hydrophilicity of the coating film surface.

(6) Evaluation of Tape Adhesion Prevention Nitto Denko Paper Adhesive Tape (No. 7290) was attached to the surface of the coating film of the test plates manufactured in Examples and Comparative Examples described later, and heated in an oven at 150 ° C. for 15 minutes. After that, it was cooled to room temperature, the attached tape was peeled off, and the appearance was visually evaluated. The evaluation criteria are as follows.
◎: No tape marks left ○: Tape marks remain, but can be removed by wiping with alcohol △: Tape marks remain thin after wiping with alcohol ×: Thick tape marks remain after wiping with alcohol

(7) Evaluation of Dust Adhesion With respect to the test plates manufactured in Examples and Comparative Examples described later, carbon black (Class12 manufactured by Nippon Powder Industry Co., Ltd.) was sprinkled on the surface of the coating film, the test plate was erected vertically, and the carbon black fell off. After repeating the operation of tapping the test plate until it disappears and sprinkling carbon black on the surface of the coating film a total of 5 times, the total light transmittance is measured in the same manner as in (4) above, and the total light transmittance before and after the test is compared. The antifouling property was evaluated by doing so.
If the change (ΔT) in the total light transmittance after the test was within -2%, it was judged to have good dust-proof and dust-proof adhesion.

(8) Evaluation of water detergency For the test plate subjected to the above evaluation of dust adhesion (7), the surface of the coating film was washed with running water of 35 mL / min for 1 minute, and then the total light transmittance was measured. The water washability was evaluated by the recovery rate of the total light transmittance with respect to the total light transmittance (before the dust adhesion test was carried out).
When the recovery rate of the total light transmittance after the test was 80% or more, it was judged to have good water washability.

[Synthesis example]
Hereinafter, synthetic examples of the polymer particles (B) used in Examples and Comparative Examples described later will be described.

(Synthesis Example 1) Synthesis of Polymer Particles (B-1) Aqueous Dispersion 1600 g of ion-exchanged water and 7 g of dodecylbenzenesulfonic acid were charged into a reactor having a reflux condenser, a dropping tank, a thermometer and a stirrer. Then, the mixture was heated to 80 ° C. with stirring to obtain a mixed solution (1).
The temperature in the reaction vessel of the mixed solution (2) obtained by mixing 130 g of dimethyldimethoxysilane and 100 g of phenyltrimethoxysilane as raw materials for the core layer with the obtained mixed solution (1) was maintained at 80 ° C. In this state, the mixture was added dropwise over about 2 hours to obtain a mixed solution (3).
Then, the mixture (3) was stirred for about 1 hour while the temperature in the reaction vessel was 80 ° C.
Next, 130 g of butyl acrylate, 200 g of tetraethoxysilane, 100 g of phenyltrimethoxysilane, and 10 g of 3-methacryloxypropyltrimethoxysilane were mixed with the obtained mixed solution (3) as raw materials for the shell layer. Mixture (4), diethylacrylamide 140 g, acrylic acid 3 g, reactive emulsifier (trade name "Adecaria Soap SR-1025", manufactured by Asahi Denka Co., Ltd., solid content 25% by mass aqueous solution) 13 g, ammonium persulfate. The mixture (5) obtained by mixing 40 g of a 2 mass% aqueous solution and 1900 g of ion-exchanged water is simultaneously added dropwise over about 2 hours while maintaining the temperature in the reaction vessel at 80 ° C. to form a mixture (6). ) Was obtained.
Further, as heat curing, the mixture (6) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, 400 g of tetraethoxysilane was added dropwise to the mixture (6) over about 30 minutes while keeping the temperature in the reaction vessel at 80 ° C. to obtain a mixture (7).
Further, as heat curing, the mixture (7) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, the mixture (7) is cooled to room temperature, filtered through a 100-mesh wire mesh, adjusted in concentration with purified water, and an aqueous dispersion (solid content 10) of polymer particles (B-1) having a number average particle diameter of 90 nm. Mass%) was obtained.

(Synthesis Example 2) Synthesis of Polymer Particles (B-2) Aqueous Dispersion 1600 g of ion-exchanged water and 7 g of dodecylbenzenesulfonic acid were charged into a reactor having a reflux condenser, a dropping tank, a thermometer and a stirrer. Then, the mixture was heated to 80 ° C. with stirring to obtain a mixed solution (1).
The temperature in the reaction vessel of the mixed solution (2) obtained by mixing 100 g of dimethyldimethoxysilane and 50 g of phenyltrimethoxysilane as raw materials for the core layer with the obtained mixed solution (1) was maintained at 80 ° C. In this state, the mixture was added dropwise over about 2 hours to obtain a mixed solution (3).
Then, the mixture (3) was stirred for about 1 hour while the temperature in the reaction vessel was 80 ° C.
Next, 100 g of butyl acrylate, 200 g of tetraethoxysilane, 80 g of phenyltrimethoxysilane, and 10 g of 3-methacryloxypropyltrimethoxysilane were mixed with the obtained mixed solution (3) as raw materials for the shell layer. Mixture (4), diethylacrylamide 110 g, acrylic acid 3 g, reactive emulsifier (trade name "Adecaria Soap SR-1025", manufactured by Asahi Denka Co., Ltd., solid content 25% by mass aqueous solution) 13 g, ammonium persulfate. The mixture (5) obtained by mixing 40 g of a 2 mass% aqueous solution and 1900 g of ion-exchanged water is simultaneously added dropwise over about 2 hours while maintaining the temperature in the reaction vessel at 80 ° C. to form a mixture (6). ) Was obtained.
Further, as heat curing, the mixture (6) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, 400 g of tetraethoxysilane was added dropwise to the mixture (6) over about 30 minutes while keeping the temperature in the reaction vessel at 80 ° C. to obtain a mixture (7).
Further, as heat curing, the mixture (7) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, the mixture (7) is cooled to room temperature, filtered through a 100-mesh wire mesh, adjusted in concentration with purified water, and an aqueous dispersion (solid content 10) of polymer particles (B-2) having a number average particle diameter of 35 nm. Mass%) was obtained.

(Synthesis Example 3) Synthesis of Polymer Particles (B-3) Aqueous Dispersion 1600 g of ion-exchanged water and 22 g of dodecylbenzenesulfonic acid were charged into a reactor having a reflux condenser, a dropping tank, a thermometer and a stirrer. Then, the mixture was heated to 80 ° C. with stirring to obtain a mixed solution (1).
The temperature in the reaction vessel of the mixed solution (2) obtained by mixing 185 g of dimethyldimethoxysilane and 151 g of phenyltrimethoxysilane as raw materials for the core layer with the obtained mixed solution (1) was maintained at 80 ° C. In this state, the mixture was added dropwise over about 2 hours to obtain a mixed solution (3).
Then, the mixture (3) was stirred for about 1 hour while the temperature in the reaction vessel was 80 ° C. Next, 150 g of butyl acrylate, 30 g of tetraethoxysilane, 145 g of phenyltrimethoxysilane, and 1.3 g of 3-methacryloxypropyltrimethoxysilane were mixed with the obtained mixed solution (3) as raw materials for the shell layer. The obtained mixture (4), diethylacrylamide 165 g, acrylic acid 3 g, reactive emulsifier (trade name "Adecaria Soap SR-1025", manufactured by Asahi Denka Co., Ltd., solid content 25% by mass aqueous solution) 13 g, excess. A mixture (5) obtained by mixing 40 g of a 2 mass% aqueous solution of ammonium sulfate and 1900 g of ion-exchanged water is simultaneously added dropwise over about 2 hours while keeping the temperature in the reaction vessel at 80 ° C. to obtain a mixture. (6) was obtained.
Further, as heat curing, the mixture (6) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, the mixture (6) is cooled to room temperature, filtered through a 100-mesh wire mesh, and the concentration is adjusted by water production to adjust the concentration to an aqueous dispersion (solid content 10) of polymer particles (B-3) having a number average particle diameter of 30 nm. Mass%) was obtained.

(Synthesis Example 4) Synthesis of Polymer Particles (B-4) Aqueous Dispersion 1600 g of ion-exchanged water and 4 g of dodecylbenzenesulfonic acid were charged into a reactor having a reflux condenser, a dropping tank, a thermometer and a stirrer. Then, the mixture was heated to 80 ° C. with stirring to obtain a mixed solution (1).
The temperature in the reaction vessel of the mixed solution (2) obtained by mixing 185 g of dimethyldimethoxysilane and 72 g of phenyltrimethoxysilane as raw materials for the core layer with the obtained mixed solution (1) was maintained at 80 ° C. In this state, the mixture was added dropwise over about 2 hours to obtain a mixed solution (3).
Then, the mixture (3) was stirred for about 1 hour while the temperature in the reaction vessel was 80 ° C. Next, 150 g of butyl acrylate, 30 g of tetraethoxysilane, 92 g of phenyltrimethoxysilane, and 1.3 g of 3-methacryloxypropyltrimethoxysilane were mixed with the obtained mixed solution (3) as raw materials for the shell layer. The obtained mixture (4), diethylacrylamide 165 g, acrylic acid 3 g, reactive emulsifier (trade name "Adecaria Soap SR-1025", manufactured by Asahi Denka Co., Ltd., solid content 25% by mass aqueous solution) 13 g, excess. A mixture (5) obtained by mixing 40 g of a 2 mass% aqueous solution of ammonium sulfate and 1900 g of ion-exchanged water is simultaneously added dropwise over about 2 hours while keeping the temperature in the reaction vessel at 80 ° C. to obtain a mixture. (6) was obtained.
Further, as heat curing, the mixture (6) was stirred for about 2 hours while the temperature in the reaction vessel was 80 ° C. Then, the mixture (6) is cooled to room temperature, filtered through a 100-mesh wire mesh, adjusted in concentration with purified water, and an aqueous dispersion (solid content 10) of polymer particles (B-4) having a number average particle diameter of 140 nm. Mass%) was obtained.

[Example 1]
As the polymer particles (B), an aqueous dispersion of the polymer emulsion particles (B-1) synthesized in the above (Synthesis Example 1) was used.
As a raw material for the spherical silica fine particles (A), water-dispersed colloidal silica having an average particle diameter of 5 nm (trade name “Snowtex OXS”, manufactured by Nissan Chemical Industry Co., Ltd., solid content 10% by mass) was used.
Tetraethoxysilane (manufactured by Shin-Etsu Chemical Co., Ltd.) was used as the hydrolyzable silicon compound (C).
Silica fine particles (A), polymer particles (B), and hydrolyzable silicon compound (C) are added to water so as to have a solid content mass ratio after drying as shown in Table 1, and the mixture is stirred at room temperature for 3 hours and hydrolyzed. The sex silicon compound (C) was hydrolyzed. Then, ethanol was added so that the ethanol concentration of the coating liquid was 50%, and dimethyl sulfoxide of 3% by mass with respect to the total mass of the coating material was further added and stirred to obtain a coating composition having a solid content of 3% by mass. ..

The above coating composition is applied to the smooth surface side of the base material (10 cm × 10 cm white plate embossed glass: Asahi Glass Solite total light transmittance 91.7%) using a spin coater at a rotation speed of 1000 rpm for 10 seconds, and then 100. It was dried at ° C. for 1 minute to obtain a test plate having a coating film (F-1). Further, a test plate having a coating film (F-1) was sintered in an electric furnace at 700 ° C. for 3 minutes, and then rapidly cooled to obtain a test plate (G-1) having a coating film having an average film thickness of 100 nm.

At this time, the composition ratio in the coating film (F-1) (similar to the mass ratio of each component calculated in terms of solid content of the coating composition) is (A) / (B) / (C') = 15/100. It became / 60.
In addition, (A) is the mass ratio of the silica fine particles (A) obtained after the drying, (B) is the mass ratio of the polymer particles (B) obtained after the drying, and (C') is , The mass ratio of the hydrolyzable condensate (C') of the hydrolyzable silicon compound (C) obtained after the drying.
The evaluation results of the obtained test plate (G-1) are shown in Table 1.

[Example 2]
As the polymer particles (B), an aqueous dispersion of the polymer particles (B-2) synthesized in the above (Synthesis Example 2) is used, and an aqueous dispersion colloidal having an average particle diameter of 65 nm is used as a raw material for the spherical silica fine particles (A). Using silica (trade name "Snowtex OYL", manufactured by Nissan Chemical Industries, Ltd., solid content 20% by mass), the composition ratio in the coating film is as shown in Table 1, and other conditions are [Example 1]. A test plate (G-2) was obtained in the same manner as above.
The evaluation results of the obtained test plate (G-2) are shown in Table 1.

[Example 3]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-3) was obtained in the same manner as in [Example 1] under other conditions.
The evaluation results of the obtained test plate (G-3) are shown in Table 1.

[Example 4]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-4) was obtained in the same manner as in [Example 2] under other conditions.
The evaluation results of the obtained test plate (G-4) are shown in Table 1.

[Example 5]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-5) was obtained in the same manner as in [Example 2] under other conditions.
The evaluation results of the obtained test plate (G-5) are shown in Table 1.

[Example 6]
The composition ratio in the coating film was as shown in Table 1, the sintering temperature was 500 ° C., and the other conditions were the same as in [Example 2] to obtain a test plate (G-6).
The evaluation results of the obtained test plate (G-6) are shown in Table 1.

[Example 7]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-7) was obtained in the same manner as in [Example 2] under other conditions.
The evaluation results of the obtained test plate (G-7) are shown in Table 1.

[Example 8]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-8) was obtained in the same manner as in [Example 1] under other conditions.
The evaluation results of the obtained test plate (G-8) are shown in Table 1.

[Example 9]
As the polymer particles (B), an aqueous dispersion of the polymer particles (B-2) synthesized in the above (Synthesis Example 2) is used, and an aqueous dispersion colloidal having an average particle diameter of 5 nm is used as a raw material for the spherical silica fine particles (A). Silica (trade name "Snowtex OXS", manufactured by Nissan Chemical Industry Co., Ltd., solid content 10% by mass) was used, and the composition ratio in the coating film was as shown in Table 1, and other conditions were [Example 1]. A test plate (G-9) was obtained in the same manner as above.
The evaluation results of the obtained test plate (G-9) are shown in Table 1.

[ Reference Example 10]
As the polymer particles (B), an aqueous dispersion of the polymer particles (B-1) synthesized in the above (Synthesis Example 1) is used, and an aqueous dispersion colloidal having an average particle diameter of 65 nm is used as a raw material for the spherical silica fine particles (A). Using silica (trade name "Snowtex OYL", manufactured by Nissan Chemical Industries, Ltd., solid content 20% by mass), the composition ratio in the coating film is as shown in Table 1, and other conditions are [Example 1]. A test plate (G-10) was obtained in the same manner as above.
The evaluation results of the obtained test plate (G-10) are shown in Table 1.

[ Reference Example 11]
As the polymer particles (B), an aqueous dispersion of the polymer particles (B-3) synthesized in the above (Synthesis Example 3) was used, the composition ratio in the coating film was as shown in Table 1, and other conditions were as shown in Table 1. A test plate (G-11) was obtained in the same manner as in [Example 1].
The evaluation results of the obtained test plate (G-11) are shown in Table 1.

[Comparative Example 1]
As the polymer particles (B), an aqueous dispersion of the polymer particles (B-4) synthesized in the above (Synthesis Example 4) was used, the composition ratio in the coating film was as shown in Table 1, and other conditions were as shown in Table 1. A test plate (G-12) was obtained in the same manner as in [Example 2].
The evaluation results of the obtained test plate (G-12) are shown in Table 1.

[Comparative Example 2]
The composition ratio in the coating film was as shown in Table 1, and a test plate (G-13) was obtained in the same manner as in [Example 1] under other conditions.
The evaluation results of the obtained test plate (G-13) are shown in Table 1.

[Comparative Example 3]
The polymer particles (B) were not used, the composition ratio in the coating film was as shown in Table 1, and the test plate (G-14) was obtained in the same manner as in [Example 1] under other conditions.
The evaluation results of the obtained test plate (G-14) are shown in Table 1.

[Comparative Example 4]
Ethanol was added first to hydrolyze the hydrolyzable silicon compound (C), and a test version (G-15) was obtained in the same manner as in Reference Example 11 under other conditions.
The evaluation results of the obtained test plate (G-15) are shown in Table 1.

[Comparative Example 5]
A test version (G-16) was obtained in the same manner as in Reference Example 11 without adding dimethyl sulfoxide.
The evaluation results of the obtained test plate (G-16) are shown in Table 1.

As shown in Table 1, in Examples 1 to 9 and Reference Examples 10 and 11, the antifouling properties such as tape adhesion prevention property, dust adhesion prevention property, and water cleaning property are exhibited while having excellent antireflection performance. I found that I could do it.

On the other hand, in Comparative Examples 1, 4 and 5, the number of irregularities having a height difference of 10 to 100 nm was large, and the tape adhesion prevention property was low. In Comparative Example 2, the number of irregularities having a height difference of 10 to 100 nm was small, and the dust adhesion prevention property was low. In Comparative Example 3, the pore ratio was low and the antireflection performance was low.

Since the coating film of the present invention has excellent antireflection, dust adhesion prevention, and tape adhesion prevention properties, it prevents base materials used outdoors for a long period of time, such as solar cells, mirrors for solar thermal power generation, building materials, and automobiles. It has industrial potential as a fouling film and an antireflection film.

Claims (10)

A coating film having pores inside the film and an uneven structure on the surface of the film.
The vacancy rate is 20% or more and less than 50%.
The number of irregularities in the height difference 10nm~100nm in line of 2μm of the film surface observed by AFM measurements, Ri 1-12 Kodea,
The coating film contains metal oxide particles (A) and polymer particles (B).
The metal oxide particles (A) contain silicon oxide and contain silicon oxide.
A coating film in which the polymer particles (B) contain polymer particles having a hydrolyzable silicon compound (b1) and a vinyl monomer having a secondary and / or tertiary amide group as a monomer unit. .. The coating film according to claim 1, wherein the static contact angle with water at 25 ° C. is less than 25 ° C. The coating film according to claim 1 or 2 , which is formed on the surface of a cover glass for a solar cell. The method for producing a coating film according to any one of claims 1 to 3 .
A method for producing a coating film, which comprises a step of applying a coating composition containing metal oxide particles (A), polymer particles (B), and a hydrolyzable silicon compound (C) to a substrate. The method for producing a coating film according to claim 4 , further comprising a step of sintering the coating composition at a temperature of 500 ° C. or higher after the coating step. The coating composition for a coating film according to any one of claims 1 to 3 .
Contains metal oxide particles (A), polymer particles (B) and hydrolyzable silicon compound (C).
The number average particle diameter of the metal oxide particles (A) is 1.0 nm to 100 nm, the number average particle diameter of the polymer particles (B) is 10 nm to 100 nm, and the metal oxide particles (A). A coating composition in which the sum of the number average particle diameter of the polymer particles (B) and the number average particle diameter of the polymer particles (B) is 50 nm to 150 nm. The coating composition according to claim 6 , wherein the mass ratio (A) / (B) of the metal oxide particles (A) to the polymer particles (B) is 0.05/1 or more and 1/1 or less. .. The sixth or seven claim, wherein the mass ratio (C) / (B) of the hydrolyzable silicon compound (C) to the polymer particles (B) is 0.1/1 or more and 1/1 or less. Coating composition. The polymer particles (B) are obtained by polymerizing a hydrolyzable silicon compound (b1) and a vinyl monomer having a secondary and / or tertiary amide group in the presence of water and an emulsifier. The coating composition according to any one of claims 6 to 8 , which comprises polymer particles. The hydrolyzable silicon compound (b1) contained in the polymer particles (B) is a hydrolyzable silicon compound (b3) containing four or more hydrolyzable functional groups, and the hydrolyzable silicon compound (b1) in the polymer particles (B). The coating composition according to claim 9 , wherein the hydrolyzed condensate of the hydrolyzable silicon compound (b3) has a mass ratio of 20% or more and 50% or less.