WO2015141240A1

WO2015141240A1 - Aqueous coating agent, film, film production method, laminate, and solar cell module

Info

Publication number: WO2015141240A1
Application number: PCT/JP2015/050287
Authority: WO
Inventors: 威史濱; 秀樹兼岩
Original assignee: 富士フイルム株式会社
Priority date: 2014-03-17
Filing date: 2015-01-07
Publication date: 2015-09-24
Also published as: TW201536864A; CN105765015A; JP2015174972A; JP6099587B2; CN105765015B

Abstract

Provided are: an aqueous coating agent capable of forming a film having good transparency and antifouling properties; a film; a film production method; a laminate; and a solar cell module. The aqueous coating agent includes water, a siloxane oligomer indicated by general formula (1), hollow silica particles, silica particles having a smaller average primary particle diameter than the average primary particle diameter of the hollow silica particles, and a surfactant. The surfactant content is at least 0.01% by mass relative to the total solid matter content in the aqueous coating agent. In general formula (1), R¹-R⁴ each independently indicate a C1-6 monovalent organic group and n indicates an integer from 2 to 20.

Description

Aqueous coating agent, film, film production method, laminate, and solar cell module

The present invention relates to an aqueous coating agent, a film obtained from the aqueous coating agent, a method for producing the film, a laminate including the film, and a solar cell module.

The aqueous coating agent containing a siloxane compound uses a solvent containing water, and the film formed using the aqueous coating agent is used for various applications because of its low surface energy and excellent transparency. .
Specific examples of the above applications include optical lenses, optical filters, flattening films for thin film transistors (TFTs) for various displays, antireflection films, anticondensation films, antifouling films, surface protective films, and the like.

When a film formed using an aqueous coating agent is used outdoors as an antireflection film, antifouling film, or surface protective film, the formed film has not only transparency but also antifouling properties. Desired.
Japanese Patent Application Laid-Open No. 2012-214772 discloses, as a coating agent capable of forming a film having excellent transparency, a siloxane-based resin containing fine silica particles, polyethylene glycol, and preferably a (meth) acrylic surfactant. A siloxane-based resin composition containing the above has been proposed.

2. Description of the Related Art In recent years, solar cell modules, which are power generation methods with a small environmental load during power generation, have attracted attention. A solar cell module generally includes a solar cell in which a solar cell element is sealed with a surface protective material, a sealing material agent, and a back surface side base material in order from a light receiving surface side (front surface side) on which sunlight is incident. ing.
Generally as a surface protection material with which the light-receiving surface side of a solar cell module is equipped, a glass base material, a weather resistant resin film, etc. are used.
The surface protective material provided on the surface on which the sunlight is incident is required to have high light transmittance since it affects the power generation efficiency of the solar cell module. Furthermore, in solar cell modules that are usually installed outdoors, the surface protective material is less likely to adhere to pollutants because the light transmittance decreases when contaminants such as dust and soot in the atmosphere adhere to it. That is, antifouling properties are required.

As a hydrophilization treatment agent used for the purpose of forming a hydrophilic film that suppresses adhesion of contaminants, for example, Japanese Patent Application Laid-Open No. 2006-52352 discloses a siloxane compound, a metal compound, a nonionic surfactant, an acidic colloidal An aqueous hydrophilizing agent containing silica and a hydrophilic organic solvent has been proposed. Japanese Patent Application Laid-Open No. 2006-52352 describes that the antifouling property of the surface of the article is improved by providing a hydrophilic film on the surface of the article with the hydrophilizing agent.

The siloxane-based resin composition described in Japanese Patent Application Laid-Open No. 2012-214772 has been proposed to solve the problem of improving coating properties and coating stability, which are problems specific to siloxane-based resins. A film formed using the siloxane-based resin composition is excellent in transparency, but the antifouling property of the formed film is not considered.
Further, the hydrophilic film formed on the surface of the article using the hydrophilizing agent described in JP-A-2006-52352 can easily remove contaminants adhering to the surface of the hydrophilic film by washing with water. However, the adhesion preventing property of the contaminant to the surface of the hydrophilic film was not taken into consideration, and it did not have the antifouling property capable of suppressing a decrease in light transmittance due to the adhesion of the contaminant.

Accordingly, an object of the present invention is to provide an aqueous coating agent that is excellent in light transmittance and can suppress the adhesion of contaminants, a film obtained by the aqueous coating agent and excellent in transparency and antifouling property, and a method for producing the film. It is to provide.
Another object of the present invention is to provide a laminate having a film excellent in transparency and antifouling property, and a solar cell module including the laminate.

The present inventors have found that the above problems can be solved by an aqueous coating agent containing a siloxane oligomer having a specific structure, hollow silica particles, silica particles having a particle diameter smaller than that of the hollow silica particles, and the like.
That is, the present invention is as described below.

[1] Water, a siloxane oligomer represented by the general formula (1), hollow silica particles, silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles, and a surfactant. An aqueous coating agent containing a surfactant in an amount of 0.01% by mass or more based on the total solid content of the aqueous coating agent.

In general formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represents a monovalent organic group having 1 to 6 carbon atoms. n represents an integer of 2 to 20.
[2] The aqueous coating agent according to [1], which contains a catalyst that promotes condensation of the siloxane oligomer.
[3] The aqueous coating agent according to [1] or [2], wherein the average primary particle diameter of the hollow silica particles is 75 nm or less.
[4] The content of the hollow silica particles is 3% by mass with respect to the total mass of the hollow silica particles contained in the aqueous coating agent and the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles. The aqueous coating agent according to any one of [1] to [3], which is 90% by mass or more.
[5] The aqueous coating agent according to any one of [1] to [4], wherein the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles have an average primary particle size of 50 nm or less. .
[6] The aqueous coating agent according to any one of [1] to [5], wherein n in the general formula (1) is 3 to 12.
[7] The aqueous coating agent according to any one of [1] to [6], comprising an antistatic agent.
[8] The content of the siloxane oligomer represented by the general formula (1) is 3% by mass or more and 70% by mass or less with respect to the total solid content in the aqueous coating agent. The aqueous coating agent as described in any one.
[9] The aqueous solution according to any one of [1] to [8], wherein the content of the hollow silica particles is from 1% by mass to 60% by mass with respect to the total solid content in the aqueous coating agent. Coating agent.
[10] The content of silica particles having an average primary particle size smaller than the average primary particle size of the empty silica particles is 5% by mass or more and 95% by mass or less based on the total solid content in the aqueous coating agent. [1] The aqueous coating agent according to any one of [9].
[11] The total content of the hollow silica particles and the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles is 30% by mass or less based on the total solid content in the aqueous coating agent. The aqueous coating agent according to any one of [1] to [10].
[12] At least one siloxane compound selected from the siloxane oligomer represented by the general formula (1) and the condensate of the siloxane oligomer represented by the general formula (1), hollow silica particles, and hollow silica particles A film containing silica particles having an average primary particle size smaller than the average primary particle size and a surfactant and having a thickness of 50 nm to 350 nm.

In general formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represents a monovalent organic group having 1 to 6 carbon atoms. n represents an integer of 2 to 20.
[13] A method for producing a film having a dry film thickness of 50 nm to 350 nm, comprising applying the aqueous coating agent according to any one of [1] to [11] on a substrate and drying.
[14] A laminate having a film according to [12] or a film obtained by the production method according to [13] on a glass substrate.
[15] A solar cell module having the laminate according to [14].

According to the present invention, it is possible to provide an aqueous coating agent having excellent light transmittance and antifouling property, a film obtained by the aqueous coating agent and excellent in transparency and antifouling property, and a method for producing the film. it can.
ADVANTAGE OF THE INVENTION According to this invention, the laminated body which has a film | membrane excellent in transparency and antifouling property, and the solar cell module provided with the laminated body can be provided.

Hereinafter, the present invention will be described in detail.
The following description may be made based on representative embodiments and specific examples of the present invention, but the present invention is not limited to such embodiments.
In the present specification, a numerical range indicated by using “to” indicates a range including numerical values described before and after “to” as a minimum value and a maximum value.
Further, in the present specification, the amount of each component in the composition means the total amount of the plurality of substances unless there is a specific notice when there are a plurality of substances corresponding to the same component in the composition.

<Water-based coating agent>
The aqueous coating agent of the present invention comprises water, a siloxane oligomer represented by the general formula (1) (hereinafter sometimes referred to as “specific siloxane compound”), hollow silica particles, and average primary particles of hollow silica particles. An aqueous coating agent comprising silica particles having an average primary particle size smaller than the diameter and a surfactant, wherein the surfactant content is 0.01% by mass or more based on the total solid mass of the aqueous coating agent It is.
Hereinafter, each component contained in the aqueous coating agent will be described.
[Siloxane oligomer represented by general formula (1) (specific siloxane compound)]
The aqueous coating agent of the present invention contains a siloxane oligomer represented by the general formula (1).

In general formula (1), R ¹ , R ² , R ³ , and R ⁴ each independently represents a monovalent organic group having 1 to 6 carbon atoms. n represents an integer of 2 to 20.

The organic group having 1 to 6 carbon atoms in R ¹ , R ² , R ³ , and R ⁴ may be linear, branched, or cyclic. Examples of the monovalent organic group include an alkyl group and an alkenyl group, and an alkyl group is preferable.
Examples of the alkyl group when R ¹ , R ² , R ³ , and R ⁴ represent an alkyl group include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a tert-butyl group, an n- A pentyl group, an n-hexyl group, a cyclohexyl group and the like can be mentioned.
In the specific siloxane compound, when the organic group of R ¹ to R ⁴ , preferably the alkyl group has 1 to 6 carbon atoms, the siloxane oligomer has good hydrolyzability. From the viewpoint of better hydrolyzability, R ¹ to R ⁴ are more preferably each independently an alkyl group having 1 to 4 carbon atoms, and preferably an alkyl group having 1 or 2 carbon atoms. Is more preferable.

In the general formula (1), n is an integer of 2 to 20. By setting n to the above range, the viscosity of the aqueous coating agent containing the specific siloxane compound can be set to an appropriate range. Further, the reactivity of the siloxane oligomer can be controlled within a preferable range. n is in the range of 2 to 20, preferably 3 to 12, and more preferably 5 to 10.
In addition, when n exceeds 20, since the viscosity of an aqueous coating agent becomes higher, there exists a possibility that handling property and uniform coating property may fall. On the other hand, a siloxane compound having n of 1 tends to make it difficult to control the reactivity of alkoxysilane, and there is a concern that the surface hydrophilicity of the film obtained after coating is lowered.
Examples of specific siloxane compounds that can be used in the present invention are described by R ¹ to R ⁴ and n in the general formula (1), but the present invention is not limited to these exemplified compounds.

The specific siloxane compound is at least partially hydrolyzed by coexisting with water. The hydrolyzate of the specific siloxane compound is a compound in which at least a part of the alkoxy group bonded to the silicon atom of the specific siloxane compound is substituted with a hydroxyl group by the reaction of the siloxane oligomer and water. It is presumed that the film obtained by the aqueous coating agent has good surface hydrophilicity due to a certain hydroxy group.
In the hydrolysis reaction, it is not always necessary to react all alkoxy groups of the specific siloxane compound, but from the viewpoint that the hydrophilicity of the film obtained by applying and drying the aqueous coating agent becomes better, more It is preferable that the alkoxy group is hydrolyzed.
The amount of water required for the hydrolysis is a molar amount equal to the alkoxy group of the specific siloxane compound, but it is preferable that a large excess of water is present from the viewpoint of allowing the hydrolysis reaction to proceed efficiently.

Although the hydrolysis reaction of the specific siloxane compound proceeds even at room temperature (25 ° C.), in order to promote the reaction, after preparing the mixture by bringing the specific siloxane compound and water into contact with each other, the obtained mixture is subjected to 30 ° C. to 50 ° C. You may heat to the extent. A longer reaction time for the hydrolysis reaction is preferred because the reaction proceeds more. For this reason, from the viewpoint of sufficiently allowing the hydrolysis reaction to proceed, it is also preferable to carry out the reaction for 1 hour to 36 hours in a heated state. In addition, it is possible to obtain a hydrolyzate of a specific siloxane compound necessary for hydrophilicity even in about half a day by allowing the catalyst for promoting the hydrolysis reaction of the specific siloxane compound described below to coexist in the mixture. .
The hydrolysis reaction is a reversible reaction. Therefore, when water is removed from the mixture, the hydrolyzate of siloxane oligomer starts and proceeds with a condensation reaction between hydroxyl groups. Accordingly, when a hydrolyzate of the specific siloxane compound is obtained by hydrolysis reaction in a mixture containing the specific siloxane compound and preferably a large excess of water, the mixture (solution) is not isolated without isolating the hydrolyzate. It is preferable to use it as it is for the preparation of the aqueous coating agent.

The aqueous coating agent of the present invention may contain only one kind of specific siloxane compound or two or more kinds.
The content of the specific siloxane compound is preferably 3% to 70% by weight, more preferably 5% to 60% by weight, and more preferably 10% to 70% by weight with respect to the total solid content of the aqueous coating agent. More preferably, it is 50 mass%.
By making content of a specific siloxane compound into the said range, transparency is favorable and the film | membrane excellent in antifouling property can be formed.

[Hollow silica particles]
The aqueous coating agent of the present invention contains hollow silica particles.
The membrane formed by applying an aqueous coating agent and drying by containing silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles and hollow silica particles described later is a hydrophilic membrane. It becomes. That is, the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles or the hollow silica particles have a characteristic of further improving the hydrophilicity of the formed film by the function of the hydroxyl group on the surface.

The hollow silica particles that can be used in the aqueous coating agent of the present invention can be used without particular limitation as long as they are hollow silica particles in which cavities are formed inside the outer shell.
Examples of the hollow silica particles that can be used in the present invention include hollow particles described in JP2013-237593A, International Publication WO2007 / 060884, and the like.
Among these, particles having an average primary particle diameter measured by a dynamic light scattering method in the range of 5 nm to 200 nm are preferable from the viewpoint of good transparency of a film formed using an aqueous coating agent. The average primary particle diameter is more preferably in the range of 10 nm to 130 nm, the average primary particle diameter is more preferably in the range of 10 nm to 75 nm, and most preferably in the range of 20 nm to 60 nm.

The primary particle diameter of the hollow silica particles can be obtained from the photograph obtained by observing the dispersed particles with a transmission electron microscope. From the image of the photograph, the projected area of the particle is obtained, and the equivalent circle diameter is obtained therefrom, which is taken as the average particle size (average primary particle size). As the average primary particle diameter in the present specification, a value calculated by measuring a projected area of 300 or more particles and obtaining an equivalent circle diameter is used.

For example, in the case of hollow silica particles having an average primary particle diameter of 50 nm and a porosity of 30% to 35%, the particle refractive index is approximately 1.30. This is 0.14 lower than 1.44 which is the refractive index of silica particles having no voids in general particles. For this reason, although various attempts have been made to improve the transparency of the membrane using hollow silica particles, the present inventors have an average primary particle size smaller than the average primary particle size of hollow silica particles described later. It has been surprisingly found that the transparency of the film is further improved by using the silica particles and the hollow silica particles in combination.

The hollow silica particles used in the present invention are also available as commercial products. For example, Julia Catalysis Chemicals Co., Ltd., Surria 1110 (trade name; average primary particle diameter 50 nm), Suriria 4110 (trade name; average primary particles). Diameter 60 nm), manufactured by Nippon Steel & Mining Co., Ltd., Silinax (trade name; average primary particle diameter 80 nm to 130 nm), and the like.

The aqueous coating agent of the present invention contains at least two types of silica particles: hollow silica particles and silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles described in detail below.
The content of the hollow silica particles in the aqueous coating agent of the present invention is preferably 1% by mass to 60% by mass, and preferably 3% by mass to 50% by mass with respect to the total solid mass of the aqueous coating agent. Is more preferably 10% by mass to 40% by mass.

[Silica particles having an average primary particle size smaller than the average primary particle size of hollow silica particles]
The aqueous coating agent of the present invention has the hollow silica particles described above and silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles. Hereinafter, silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles may be referred to as “small particle size silica particles”.
The small particle size silica particles that can be used in the present invention are not particularly limited as long as the average primary particle size is smaller than the average primary particle size of the hollow silica particles described above.
The small particle size silica particles may be hollow particles having voids inside, porous particles, or particles having no voids inside.
From the viewpoint of further improving the transparency of the formed film, the average primary particle size of the small particle size silica particles needs to be smaller than the average primary particle size of the hollow silica particles.
As the small particle size silica particles that can be used in the present invention, silica particles generally known as colloidal silica, porous silica particles, hollow silica particles, and the like having a smaller average primary particle size than the hollow silica particles used in combination are appropriately used. It can be selected and used.

The small particle diameter silica particles that can be used in the present invention preferably have a small average primary particle diameter in order to suppress light scattering in consideration of light transmittance, and more preferably have a particle diameter that does not cause Rayleigh scattering. The Rayleigh scattering intensity is affected by the refractive index and size of the particles with respect to the medium, and is proportional to the sixth power of the particle diameter when spherical particles are assumed. For this reason, the average primary particle diameter of the small particle diameter silica particles is preferably smaller than the average primary particle diameter of the hollow silica particles used in combination and 100 nm or less, and general-purpose optics that require transparency. For use, it is more preferably 50 nm or less. When more severe transparency is required, it is more preferably 30 nm or less.
In consideration of the fact that the silica particles tend to aggregate as the average primary particle size decreases, the average primary particle size of the small particle size silica particles is preferably in the range of 5 nm to 100 nm, and preferably in the range of 10 nm to 50 nm. A range is more preferable.
The average primary particle diameter of the silica particles can be measured by the same method as for the hollow silica particles.

When hollow silica particles and silica particles having a small particle diameter are used in combination, air is taken into the film in the process of applying and drying the aqueous coating agent on the substrate, and as a result, fine voids are formed in the film. I guess. Therefore, it is considered that the refractive index of the film becomes lower and the light transmittance becomes better than when the hollow silica particles are used alone due to the formed voids. Further, since the voids in the film are minute, it is considered that there is almost no influence on the antifouling property of the coating film.

The shape of the small particle size silica particles that can be used in the present invention is not particularly limited and may be any of spherical, plate-like, needle-like, necklace-like, etc., but from the viewpoint of improving transparency, Those having a small aspect ratio such as an elliptical shape are preferred.
Silica particles that can be used in the present invention are also available as commercial products. For example, Snowtex O-33 (trade name: average primary particle size: 10 nm to 20 nm, manufactured by Nissan Chemical Industries), which is colloidal silica, Snowtex OYL (average primary particle size: 50 nm-80 nm, manufactured by Nissan Chemical Industries) and the like.
The aqueous coating agent of the present invention may contain only one kind of small particle size silica particles, or two or more kinds, and when containing two or more kinds, the average primary particle diameter, shape, etc. Different ones may be used in combination.

The content of the small particle diameter silica particles in the aqueous coating agent of the present invention is preferably 5% by mass to 95% by mass with respect to the total solid mass of the aqueous coating agent, and is 10% by mass to 90% by mass. More preferably, it is more preferably 20% by mass to 80% by mass.
When the content of the small particle size silica particles is in the above range, the aqueous coating agent of the present invention is excellent in transparency and antifouling property, and can form a hydrophilic film.

(Content of silica particles)
The content (content ratio) of the hollow silica particles with respect to the total silica particle content, which is the total amount of the hollow silica particles and the small particle size silica particles contained in the aqueous coating agent, is preferably 3% by mass to 90% by mass. The content is more preferably 5% by mass to 80% by mass, and further preferably 10% by mass to 60% by mass.
Further, the total silica particle content in the aqueous coating agent is preferably 5% by mass to 90% by mass, and more preferably 10% by mass to 80% by mass with respect to the total solid content mass of the aqueous coating agent. More preferably, the content is 20% by mass to 70% by mass.
The total silica particle content is preferably 30% by mass or less, more preferably 20% by mass or less, and further preferably 10% by mass or less, based on the total mass of the aqueous coating agent. preferable. When the content of the total silica particles with respect to the total mass of the aqueous coating agent is within the above range, the dispersibility of the silica particles in the aqueous coating agent becomes better, and the aggregation of silica particles, particularly silica particles having a small particle diameter, is effective. To be suppressed.

〔water〕
The aqueous coating agent of the present invention contains water.
By using water as the solvent for the aqueous coating agent, compared to a coating agent that uses a large amount of a volatile organic solvent, the load on the environment is greatly reduced, and the hydrolyzed product obtained by hydrolysis of a specific siloxane compound. It is possible to suppress a decrease in hydrophilicity of the formed film resulting from an undesirable condensation reaction during storage of the decomposition product and an undesirable condensation reaction.
The solvent in the aqueous coating agent of the present invention contains water, but may further contain a hydrophilic organic solvent having excellent affinity with water.
The content of water in the solvent used for the aqueous coating agent is preferably 30% by mass or more, and more preferably 40% by mass or more based on the total amount of the solvent.
Examples of other components that can be contained in the solvent include hydrophilic compounds such as hydrophilic organic solvents and glycol solvents.
When the solvent contains a hydrophilic organic solvent, the surface tension of the aqueous coating agent is lower, more uniform application is possible, and the ratio of the low-boiling organic solvent is increased, so that the coating liquid can be easily dried. And so on.
The hydrophilic organic solvent that can be used in the present invention is not particularly limited, and examples thereof include methanol, ethanol, isopropanol, butanol, acetone, ethylene glycol, and ethyl cellosolve. Alcohol is preferable from the viewpoint of availability and reduction of environmental burden, and ethanol, isopropanol, and the like are more preferable.

The solid content with respect to the total mass of the aqueous coating agent of the present invention is preferably in the range of 0.1% by mass to 30% by mass, more preferably 0.2% by mass to 20% by mass, More preferably, it is 0.5 to 10% by mass. In order to adjust the solid content of the aqueous coating agent to the preferred range described above, the content of the solvent, particularly water, may be adjusted.

Since the hollow silica particles and the small particle diameter silica particles contained in the aqueous coating agent of the present invention have a small average primary particle diameter, it is important to suppress aggregation and maintain a dispersed state. It is important that the dispersed state be maintained not only in the aqueous coating agent but also during film formation including coating, drying and curing, and after film formation.
In the present invention, since water is contained as a solvent, there is an advantage that the dispersed state of each contained particle can be favorably maintained by repulsion of charges derived from dissociation of hydroxyl groups on the surface of silica particles.

[Surfactant]
The aqueous coating agent of the present invention contains a surfactant in an amount of 0.01% by mass or more based on the total solid mass of the aqueous coating agent.
By containing the surfactant, the coating property of the aqueous coating agent is improved, and the surface tension of the aqueous coating agent is suppressed to a lower level, thereby improving the uniform coating property and the coating surface property.
Examples of the surfactant that can be used in the present invention include nonionic surfactants, anionic surfactants that are ionic surfactants, cationic surfactants, and amphoteric surfactants. Can be suitably used.
If the ionic surfactant is used in excess, the amount of the electrolyte in the aqueous coating agent increases, and the hollow silica particles and the small particle size silica particles contained in the aqueous coating agent tend to aggregate. In consideration, it is preferable to use a nonionic surfactant as the surfactant because the degree of freedom of the content of the surfactant is increased.

Examples of nonionic surfactants include polyalkylene glycol monoalkyl ether, polyalkylene glycol monoalkyl ester, polyalkylene glycol monoalkyl ester / monoalkyl ether, and the like. More specifically, polyethylene glycol monolauryl ether, polyethylene glycol monostearyl ether, polyethylene glycol monocetyl ether, polyethylene glycol monolauryl ester, polyethylene glycol monostearyl ester and the like can be mentioned.

On the other hand, since the aqueous coating agent contains an ionic surfactant, the ionic surfactant is segregated in the vicinity of the outermost surface of the film formed by applying the aqueous coating agent and drying it. It is preferable in that charging of the film surface can be prevented and hydrophilicity can be improved.
As described above, when the ionic surfactant is excessively contained, the silica particles are easily aggregated. Generally, there are few examples in which the ionic surfactant and the silica particles are used in combination. However, according to the study by the present inventors, when an ionic surfactant is added to the aqueous coating agent, the ionic surfactant is formed with the aqueous coating agent by using it in a content less than the amount causing aggregation of the silica particles. It has been found that the antifouling properties of the membrane can be enhanced.
That is, as the surfactant, any of nonionic and ionic surfactants can be preferably used. When the aqueous coating agent of the present invention contains 0.01% by mass or more of the surfactant, the antifouling property and surface hydrophilicity of the film formed from the aqueous coating agent are excellent.

Examples of ionic surfactants include anionic surfactants such as alkyl sulfates, alkylbenzene sulfonates and alkyl phosphates, cationic surfactants such as alkyltrimethylammonium salts and dialkyldimethylammonium salts, alkylcarboxyl Examples include amphoteric surfactants such as betaine.

The content of the surfactant in the aqueous coating agent of the present invention is 0.01% by mass or more, preferably 0.02% by mass or more, and preferably 0.03% by mass with respect to the total mass of the aqueous coating agent. % Or more is more preferable.
By setting the content of the surfactant in the above range, the wettability can be improved, and the coating property of the aqueous coating agent becomes good.
The upper limit of the content of the surfactant is not particularly limited, but depending on the type of the surfactant, there is a concern that it may segregate on the surface after application of the aqueous coating agent to reduce the strength of the film. Therefore, considering the content of other components, the surfactant content is preferably 10% by mass or less, more preferably 8% by mass or less, based on the total solid mass of the aqueous coating agent. More preferably, it is 5 mass% or less.
In addition, when an ionic surfactant is used as the surfactant, the content of the ionic surfactant is increased from the viewpoint of enhancing the antifouling property and suppressing the aggregation of silica particles due to the influence of the surfactant. Is preferably 5.0% by mass or less, more preferably 3.0% by mass or less, and still more preferably 1.0% by mass or less, based on the total mass of the aqueous coating agent.

[Other ingredients]
The aqueous coating agent of the present invention can contain other components depending on the purpose as long as the effects of the present invention are not impaired in addition to the essential components described above.
(Antistatic agent)
The aqueous coating agent of the present invention may contain an antistatic agent.
The antistatic agent is used for the purpose of suppressing the adhesion of contaminants by imparting antistatic properties to the film formed of the aqueous coating agent.
There are no particular restrictions on the antistatic agent for imparting antistatic properties.
Antistatic agents used in the present invention include ionic surfactants, metal oxide particles, metal nanoparticles, conductive polymers, ionic liquids that are different from the surfactants described above, which are essential components of the present invention. At least one selected from the above can be used. Two or more antistatic agents may be used in combination. As the antistatic agent, the ionic surfactant described above may be used. When the ionic surfactant is used, a surfactant different from the surfactant which is an essential component of the present invention is used. I will do it.
Metal oxide particles need to be added in a relatively large amount in order to provide antistatic properties. However, since they are inorganic particles, the inclusion of metal oxide particles prevents the film formed by the aqueous coating agent. Dirty can be further increased.

Although there is no restriction | limiting in particular in a metal oxide particle, A tin oxide particle, an antimony dope tin oxide particle, a tin dope indium oxide particle, a zinc oxide particle etc. are mentioned.
The metal oxide particles have a large refractive index, and if the particle size is large, there is concern about a decrease in light transmittance due to scattering of transmitted light. Therefore, the average primary particle size of the metal oxide particles is preferably 100 nm or less, and 50 nm. Or less, more preferably 30 nm or less.
The shape of the metal oxide particles is not particularly limited, and may be spherical, plate-shaped, or needle-shaped.
The average primary particle diameter of the metal oxide fine particles can be obtained in the same manner as the hollow silica particles described above.
In addition, when the shape of the metal oxide particles is not spherical, it may be obtained using other methods, for example, a dynamic light scattering method.

One kind of antistatic agent may be contained in the aqueous coating agent, or two or more kinds thereof may be contained. When two or more types of metal oxide particles are contained, two or more types having different average primary particle diameters, shapes, and materials may be used.
In the aqueous coating agent of the present invention, the content of the antistatic agent is preferably 40% by mass or less, more preferably 30% by mass or less, and more preferably 20% by mass with respect to the total solid mass of the aqueous coating agent. More preferably, it is% or less.
By making content of an antistatic agent into the said range, antistatic property can be effectively provided to the formed film | membrane, without reducing the film forming property of an aqueous coating agent.
The content when metal oxide particles are used as the antistatic agent is preferably 30% by mass or less, more preferably 20% by mass or less, based on the total mass of the aqueous coating agent. More preferably, it is at most mass%.
By making the content of the metal oxide particles in the above range, the dispersibility of the metal oxide particles in the aqueous coating agent becomes good, the occurrence of aggregation is suppressed, and the necessary antistatic property is formed by the aqueous coating agent. It can be applied to the membrane.

(catalyst)
The aqueous coating agent of the present invention preferably contains a catalyst that promotes condensation of the siloxane oligomer.
When the aqueous coating agent contains a catalyst, a film having higher durability can be formed. In the present invention, at least part of the hydroxyl groups of the hydrolyzate of the siloxane oligomer are condensed with each other to form a condensate as the water content in the film is reduced by drying after application of the aqueous coating agent. Thus, a stable film is formed. When the aqueous coating agent contains a catalyst that promotes the condensation of the siloxane oligomer during the formation of the film, the film can be formed more rapidly.

Although the catalyst which accelerates | stimulates the condensation of the siloxane oligomer which can be used for this invention is not specifically limited, An acid catalyst, an alkali catalyst, an organometallic catalyst, etc. are mentioned.
Examples of the acid catalyst include nitric acid, hydrochloric acid, sulfuric acid, acetic acid, chloroacetic acid, formic acid, oxalic acid, toluenesulfonic acid and the like.
Examples of the alkali catalyst include sodium hydroxide, potassium hydroxide, tetramethylammonium hydroxide and the like.
Examples of organometallic catalysts include aluminum bis (ethyl acetoacetate) mono (acetylacetonate), aluminum tris (acetylacetonate), aluminum chelate compounds such as aluminum ethylacetoacetate diisopropylate, zirconium tetrakis (acetylacetonate) Zirconium chelate compounds such as zirconium bis (butoxy) bis (acetylacetonate), titanium chelate compounds such as titanium tetrakis (acetylacetonate), titanium bis (butoxy) bis (acetylacetonate), and dibutyltin diacetate, dibutyltin dilaurate, And organotin compounds such as dibutyltin dioctiate.
The type of the catalyst is not particularly limited, but an organometallic catalyst is preferable, and among them, an aluminum chelate compound and a zirconium chelate compound are more preferable.

The content of the catalyst for promoting the condensation of the siloxane oligomer is preferably 0.1% by mass to 20% by mass, and preferably 0.2% by mass to 15% by mass with respect to the total solid mass of the aqueous coating agent. More preferably, it is more preferably 0.3% by mass to 10% by mass.
By setting the content of the catalyst in the above range, a film having good transparency can be formed more quickly.

In addition, the catalyst which accelerates | stimulates the condensation of a siloxane oligomer is useful also for acceleration | stimulation of the hydrolysis reaction of the siloxane oligomer mentioned above.
The hydrolysis reaction and condensation reaction of the silicon-bonded alkoxy group of the siloxane oligomer are in an equilibrium relationship, and if the water content in the aqueous coating agent is large, the water content is low in the direction of hydrolysis. Proceed in the direction of condensation. Since the catalyst that promotes the condensation reaction of the alkoxy group has an effect of promoting the reaction in both directions, the hydrolysis reaction can be promoted in a state where the water content in the aqueous coating agent is large. The presence of the catalyst allows the hydrolysis of the siloxane oligomer to proceed more reliably under milder conditions.
At this time, the catalyst used for the hydrolysis reaction of the siloxane oligomer is not removed from the aqueous coating agent, but is contained as it is to be a component of the aqueous coating agent. Along with the decrease, the catalyst acts as a catalyst for condensation of the siloxane oligomer, so that an efficient film can be formed.

(Other additives)
The aqueous coating agent of the present invention may have additives such as preservatives as appropriate in addition to the above.
As described above, the aqueous coating agent of the present invention forms a film by condensing and curing the specific siloxane compound by reducing the amount of water, which is a solvent, as described above. Therefore, formation of a cured film does not require light irradiation or high-temperature heat treatment required for a polymerization reaction, a crosslinking reaction, or the like. Moreover, it is not necessary to contain the photoinitiator required for a polymerization reaction, a crosslinking reaction, etc., a thermal polymerization initiator, etc.
For this reason, the aqueous coating agent of the present invention that does not contain a photopolymerization initiator, a thermal polymerization initiator, or the like that affects storage stability has good storage stability.
According to the aqueous coating agent of the present invention, a film having excellent transparency and excellent antifouling property can be formed by a simple method.

It can be said that the water-based coating agent of the present invention is characterized by the fact that most of the solid content contained in the water-based coating agent is silicon and oxygen and the carbon content is low. By reducing the carbon content, for example, when a film formed by applying an aqueous coating agent and drying it is used in a harsh environment such as the surface of a solar cell module, the film is affected by light and heat. Can be kept to a minimum.
In the aqueous coating agent of the present invention, the proportion of carbon in the total solid mass is preferably 3% by mass or less, more preferably 2.5% by mass or less, and preferably 2% by mass or less. Further preferred.

In the aqueous coating agent of the present invention, it is preferable that the organic compound containing carbon is of low molecular weight. Specifically, the content of the organic compound having a molecular weight of 1100 or more in the total solid mass of the aqueous coating agent is preferably 0.2% by mass or less, more preferably 0.1% by mass, More preferably, it is not contained except for mass%, ie, inevitable impurities. By setting the content of the organic compound having a molecular weight of 1100 or more in the above range, the compatibility of the solid content in the aqueous coating agent becomes better, and the film formability when the aqueous coating agent is applied and dried is further improved. sell.

(Method for preparing aqueous coating agent)
The aqueous coating agent of the present invention comprises a specific siloxane compound, a solvent containing water, a surfactant of 0.01% by mass or more based on the total solid mass of the aqueous coating agent, hollow silica particles, and small particle size silica. Prepared by mixing particles.
It is preferable that the specific siloxane compound is first mixed with a solvent containing water to form a hydrolyzate of the specific siloxane compound to prepare a hydrolyzate solution of the specific siloxane compound. At this time, a catalyst for promoting the condensation of the specific siloxane compound can be added.
A surfactant, hollow silica particles, and small particle size silica particles are further added to the obtained hydrolyzate solution of the specific siloxane compound. At this time, an antistatic agent used in combination can be further added as desired.
At this stage, a catalyst for promoting condensation of the siloxane oligomer can be added. Moreover, you may add in part or all of surfactant and the antistatic agent used together together when it obtains the hydrolyzate of a specific siloxane compound.

The conditions for preparing the aqueous coating agent are not particularly limited. However, depending on the type and physical properties of the hollow silica particles and the small particle size silica particles used, there is a concern that they may aggregate depending on the pH and the concentration of coexisting components. Therefore, it is preferable that the hollow silica particles and the small particle size silica particles are added in the latter half, preferably last, in the previous step of the preparation of the aqueous coating agent. When hollow silica particles and small silica particles are contained, if necessary, a dispersion in which silica particles are dispersed in an aqueous solvent in advance, or a commercially available silica particle dispersion, the pH of the dispersion and the aqueous coating are used. It is preferable to adjust the pH of the solvent of the silica particle dispersion and the aqueous coating agent to the same or close values by making the pH of the solvent in the agent both acidic or basic.

By using the aqueous coating agent of the present invention, a film having good transparency is formed. Since the aqueous coating agent of the present invention contains a specific siloxane compound, hollow silica particles, small silica particles, and a surfactant, the formed film has good surface hydrophilicity, and the film surface is antifouling. It is also one of the features of the aqueous coating agent of the present invention that it is excellent in water.
For this reason, the aqueous coating agent of this invention is suitable for formation of the film | membrane which protects the surface of the apparatus used outdoors, such as a solar cell module. The formed film is excellent in antifouling property, and adhesion of contaminants is suppressed outdoors. Further, since the membrane has good hydrophilicity, a slight contamination adhered can be easily washed away by rainwater or the like when it rains.
Therefore, the water-based coating agent of the present invention is useful for forming surface materials for various substrates, surface materials for optical devices, particularly surface protection materials for solar cell modules.

<Membrane>
The film of the present invention contains at least one siloxane compound selected from a specific siloxane compound and a condensate of the specific siloxane compound, hollow silica particles, small particle diameter silica particles, and a surfactant. Is a film having a thickness of 30 nm to 500 nm.
(Film formation)
The film of the present invention is formed by the aqueous coating agent of the present invention described above.
The film of the present invention can be formed by applying and drying the aqueous coating agent of the present invention. There is no restriction | limiting in particular in the base material which apply | coats an aqueous coating agent, As a base material, all various base materials, such as glass, resin, a metal, and ceramics, can be used conveniently.
When glass is used as the substrate, condensation of hydroxyl groups on silicon occurs even with hydroxyl groups on the glass surface, thereby forming a film having excellent adhesion to the substrate.
The film of the present invention preferably has a film thickness in the range of 50 nm to 350 nm from the viewpoint of transparency. What is necessary is just to form the film | membrane according to the objective in the range of said film thickness.

(Base material)
The method for applying the aqueous coating agent of the present invention to the substrate is not particularly limited, and any of known application methods such as spray coating, brush coating, roller coating, bar coating, dip coating and the like can be applied. .
Drying after applying the aqueous coating agent may be performed at room temperature (25 ° C.) or by heating to 40 ° C. to 120 ° C. When heating is performed, the drying time can be about 1 to 30 minutes.

(Physical properties of membrane)
The film of the present invention has good transparency, and the surface is hydrophilic due to the components contained in the film. Further, by containing an antistatic agent, the film also exhibits antistatic properties. For this reason, the film | membrane of this invention can suppress adhesion of a contaminant and is excellent in antifouling property. Furthermore, even if contaminants adhere to the film surface, the contaminants are easily removed by washing with water.
Preferred physical properties of the film of the present invention are listed below.

The film of the present invention preferably has sufficient light transmittance. The integrating sphere transmittance (average of λ = 300 nm to 1200 nm) of the film of the present invention is preferably 90% or more, and more preferably 93% or more.
The integral sphere transmittance of the membrane was determined by measuring the integral sphere transmittance of a glass substrate provided with a film formed of a glass substrate not formed with a film and an aqueous coating agent, using a barium sulfate white plate as a reference. . The light transmittance improvement with respect to the glass substrate was calculated by subtracting the transmittance of the glass substrate from the transmittance of the glass on which the aqueous coating agent was formed.
The integrating sphere transmittance can be measured by using a transmission spectrophotometer with an integrating sphere. Specifically, for example, a device in which an integrating sphere attachment device (ISR-2200, Shimadzu Corp.) is connected to an ultraviolet visible infrared spectrophotometer (UV-3600, Shimadzu Corp.) UV-3600, Shimadzu Corporation) and a multi-purpose large sample chamber (MPC-3100, Shimadzu Corporation) connected to the apparatus. In the present invention, values measured using UV-3100PC (Shimadzu Corporation) using light having a wavelength of 300 nm to 1400 nm are employed. It is determined that the greater the transmittance improvement obtained by measurement, the better the transparency (low reflectivity).

The light transmittance improvement (λ = 400 nm to 1400 nm) of the film of the present invention is preferably 1% or more, and more preferably 1.5% or more. 1.8% or more is particularly preferable.
The transmittance can be measured by, for example, a self-recording spectrophotometer (UV2400-PC, manufactured by Shimadzu Corporation).

The surface resistance of the film is 1 × 10 ¹² Ω / sq. Or less, preferably 1 × 10 ¹¹ Ω / sq. More preferably, it is 1 × 10 ¹⁰ Ω / sq. More preferably, it is as follows. By setting the surface resistance of the film in the above range, sufficient antifouling property can be imparted to the film.
The surface resistance value of the film can be measured using Hiresta MCP-HT450 manufactured by Mitsubishi Chemical Analytech.

The water contact angle of the membrane is preferably 40 ° or less, more preferably 30 ° or less, further preferably 25 ° or less, and particularly preferably 15 ° or less.
As for the water contact angle, the contact angle with respect to pure water was measured five times, and the average value was defined as the contact angle value.
By setting the water contact angle of the membrane within the above range, sufficient hydrophilicity can be imparted to the membrane.

<Laminate>
The laminated body of this invention is equipped with the film | membrane formed with the aqueous coating agent of this invention on a glass base material.
Since the film | membrane of this invention contains 1 or more types chosen from the specific siloxane compound and the hydrolyzate of a specific siloxane compound as stated above, it is excellent in the adhesiveness to a glass base material.
For this reason, since the laminate having the film of the present invention formed on the glass substrate with the aqueous coating agent of the present invention becomes a film excellent in transparency and antifouling property, the surface protection member of the solar cell module, It can be suitably used for antifouling materials for building materials such as optical devices, window glass and guide mirrors.

The laminate of the present invention is a laminate comprising a film having excellent transparency and adhesion to the glass substrate on the surface of the glass substrate. The film of the present invention is excellent in transparency and antifouling properties. Therefore, the laminate of the present invention having the film of the present invention is suitable as a protective member and a surface material having high transparency and requiring adhesion prevention against dirt, and in particular, a severe environment outdoors. It is useful as a protective member on the light-receiving surface side of a solar cell module that is disposed for a long period of time and requires transparency and durability for a long period of time.

<Solar cell module>
The solar cell module of the present invention includes a laminate including the above-described film of the present invention. The solar cell module of the present invention is typified by the laminate and the polyester film of the present invention, which are provided with a solar cell element that converts the light energy of sunlight into electric energy and is provided on the side where sunlight enters. It arrange | positions between the solar cell backsheets. The laminate and the polyester film can be sealed with a sealing agent typified by a resin such as an ethylene-vinyl acetate copolymer.

About members other than a laminated body and a back sheet, such as a solar battery element and a solar battery cell, for example, described in detail in “Solar power generation system constituent material” (supervised by Eiichi Sugimoto, Industrial Research Committee, Inc., issued in 2008). Has been. The solar cell module of the present invention includes a module provided with the laminate of the present invention on the side where sunlight enters.

Examples of the substrate of the laminate provided on the side on which sunlight is incident include a glass substrate, a transparent resin such as an acrylic resin, and the like. In the solar cell module of the present invention, the surface of the glass substrate. In addition, a laminate including the film of the present invention that is excellent in antifouling property in addition to transparency is used.

The solar cell element used in the solar cell module of the present invention is not particularly limited, and silicon-based materials such as single crystal silicon, polycrystalline silicon, and amorphous silicon, copper-indium-gallium-selenium, copper-indium-selenium, Various known solar cell elements such as III-V and II-VI compound semiconductor systems such as cadmium-tellurium and gallium-arsenic can be applied.
The solar cell module of the present invention includes a laminate having the film of the present invention on the glass substrate, which is excellent in transparency, antifouling property and hydrophilicity. Reduced light transmission due to scratches and contamination, and the attached contaminants can be easily removed with rain or other water. Is maintained.

The features of the present invention will be described more specifically with reference to examples and comparative examples. The materials, amounts used, ratios, processing details, processing procedures, and the like shown in the following examples can be changed as appropriate without departing from the spirit of the present invention. Therefore, the scope of the present invention should not be construed as being limited by the specific examples shown below.
Hereinafter, unless otherwise specified, “%” representing concentration means “mass%”.

[Example 1]
-Preparation of silicate oligomer liquid A1-
Specific siloxane compound: silicate MS-51 (Mitsubishi Chemical Corporation) 1.54 parts by mass, ethanol 40.74 parts by mass, pure water 51.94 parts by mass, nonionic surfactant, polyoxyethylene lauryl ether: Emma A silicate oligomer solution A1 was prepared by mixing 5.78 parts by mass of Rex 715 (manufactured by Nippon Emulsion Co., Ltd., diluted with 0.5% pure water) and stirring at room temperature (25 ° C.) for 24 hours or more.
Silicate MS-51 is a siloxane oligomer represented by the general formula (1), and is a specific siloxane compound 1 in which R is all methyl groups and n has an average of 5.

-Preparation of aqueous coating agent B1-
41.28 parts by mass of the resulting silicate oligomer liquid A1, 29.31 parts by mass of pure water, 17.11 parts by mass of ethanol, 2.16 parts by mass of Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) , Small particle size silica particles: Snowtex O-33 (trade name: manufactured by Nissan Chemical Industries, average primary particle size: 10-20 nm) 1.53 parts by mass, hollow silica particles: thruria 1110 (trade name, JGC Catalysts & Chemicals) Aqueous coating agent B1 was produced by mixing 3.01 parts by mass of the company, average primary particle size 50 nm).
A coating amount of the obtained aqueous coating agent B1 on the surface of a glass substrate (non-alkali glass OA-10: trade name, thickness: 1.0 mm, manufactured by Nippon Electric Glass Co., Ltd.) using a wire bar to a dry film thickness of 150 nm Was applied to form a coating film. The coating film was dried at room temperature (25 ° C.) for 30 minutes to produce a laminate having a film with a thickness of 150 nm on a glass substrate.

[Example 2]
-Preparation of silicate oligomer liquid A2-
Silicate MS-51 (manufactured by Mitsubishi Chemical Corporation) 1.54 parts by mass, ethanol 40.74 parts by mass, and pure water 51.94 parts by mass were mixed and stirred for 24 hours or longer to prepare silicate oligomer liquid A2.
-Preparation of aqueous coating agent B2-
Silicate oligomer liquid A2 41.28 parts by mass, pure water 31.66 parts by mass, ethanol 18.24 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 1.84 parts by mass, Snowtex Aqueous coating agent B2 was prepared by mixing 1.58 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 3.12 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
Using the obtained aqueous coating agent B2, a laminate was produced in the same manner as in Example 1.

Example 3
In Example 1, an aqueous coating agent B3 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation.
-Preparation of aqueous coating agent B3-
Silicate oligomer liquid A2 41.28 parts by mass, pure water 31.66 parts by mass, ethanol 18.24 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 0.18 parts by mass, Snowtex Aqueous coating agent B3 was prepared by mixing 1.56 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 3.09 parts by mass of Thruria 1110 (manufactured by JGC Catalysts and Chemicals).
Using the obtained aqueous coating agent B3, a laminate was produced in the same manner as in Example 1.

Example 4
A silicate oligomer liquid A3 and an aqueous coating agent B4 were obtained in the same manner except that the surfactant EMALEX 715 used in Example 1 was changed to EMALEX 720 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution). .
Using the obtained aqueous coating agent B4, a laminate was produced in the same manner as in Example 1.

Example 5
A silicate oligomer solution A4 and an aqueous coating agent B5 were prepared in the same manner except that the surfactant EMALEX 715 used in Example 1 was changed to EMALEX 712 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution). .
Using the obtained aqueous coating agent B5, a laminate was produced in the same manner as in Example 1.

Example 6
A silicate oligomer solution A5 was prepared in the same manner as in Example 1 except that the silicate MS-51 used for the preparation of the silicate oligomer solution A1 was changed to silicate MS-56 (manufactured by Mitsubishi Chemical Corporation), and the resulting silicate oligomer was obtained. An aqueous coating agent B6 was produced in the same manner as in Example 1 except that the liquid A5 was used.
Using the obtained aqueous coating agent B6, a laminate was prepared in the same manner as in Example 1.
Silicate MS-56 is a siloxane oligomer represented by the general formula (1), and is a specific siloxane compound 2 in which R is all methyl groups and n has an average of 10.

Example 7
-Preparation of silicate oligomer liquid A6-
Specific siloxane compound: 3.85 parts by mass of ethyl silicate 40 (manufactured by Colcoat), 40.74 parts by mass of ethanol, 51.94 parts by mass of pure water, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., diluted with 0.5% pure water) The silicate oligomer liquid A6 was produced by mixing 5.78 parts by mass and stirring for 24 hours or more.
-Preparation of aqueous coating agent B7-
Silicate oligomer liquid A6 41.28 parts by mass, pure water 29.31 parts by mass, ethanol 15.35 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.11 parts by mass, Snowtex Aqueous coating agent B7 was prepared by mixing 1.49 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 2.94 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B7.
The ethyl silicate 40 is a siloxane oligomer represented by the general formula (1), and is a specific siloxane compound 3 in which all R are ethyl groups and the average of n is 5.

Example 8
-Preparation of silicate oligomer liquid A7-
Silicate MS-51 (Mitsubishi Chemical Corporation) 1.54 parts by mass, ethanol 40.74 parts by mass,
4. 51.94 parts by mass of pure water, catalyst: aluminum chelate D (manufactured by Kawaken Fine Chemical Co., 1% ethanol dilution) 0.47 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 78 mass parts was mixed and the silicate oligomer liquid A7 was produced by stirring at room temperature (25 degreeC) for 12 hours or more.
-Preparation of aqueous coating agent B8-
41.28 parts by mass of the resulting silicate oligomer liquid A7, 29.31 parts by mass of pure water, 17.11 parts by mass of ethanol, 1.74 parts by mass of aluminum chelate D, Emalex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% Pure water dilution) 2.28 parts by mass, Snowtex O-33 (manufactured by Nissan Chemical Industries, Ltd.) 1.56 parts by mass, Sululia 1110 (manufactured by JGC Catalysts & Chemicals) 3.08 parts by mass Agent B8 was produced.
Using the obtained aqueous coating agent B8, a laminate was prepared in the same manner as in Example 1.

Example 9
Aqueous coating agent B9 was prepared in the same manner as in Example 1, except that the hollow silica particles used in Example 1: Through rear 1110 were changed to Through rear 4110 (manufactured by JGC Catalysts & Chemicals, average primary particle size 60 nm).
Using the obtained aqueous coating agent B9, a laminate was produced in the same manner as in Example 1.

Example 10
Aqueous coating agent B10 was produced in the same manner as in Example 1 except that the hollow silica particles used in Example 1: Thruria 1110 was changed to Sirinax (manufactured by Nippon Steel Mining Co., Ltd.).
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B10.

Example 11
Aqueous coating agent as in Example 1, except that the small particle size silica particle Snowtex O-33 used in Example 1 was changed to Snowtex OYL (manufactured by Nissan Chemical Industries, Ltd., average primary particle size 50 to 80 nm). B11 was produced.
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B11.

Example 12
An aqueous coating agent B12 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B12-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 28.06 parts by mass, ethanol 17.11 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex Aqueous coating agent B12 was prepared by mixing 1.86 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 2.47 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
Using the obtained aqueous coating agent B12, a laminate was prepared in the same manner as in Example 1.

Example 13
An aqueous coating agent B13 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B13-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 26.49 parts by mass, ethanol 17.11 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex Aqueous coating agent B13 was produced by mixing 2.29 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 1.77 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
Using the obtained aqueous coating agent B13, a laminate was produced in the same manner as in Example 1.

Example 14
An aqueous coating agent B14 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B14-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 24.73 parts by mass, ethanol 15.79 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex Aqueous coating agent B14 was produced by mixing 2.74 parts by mass of O-33 (manufactured by Nissan Chemical Industries, Ltd.) and 1.05 parts by mass of Thruria 1110 (manufactured by JGC Catalysts and Chemicals).
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B14.

Example 15
An aqueous coating agent B15 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B15-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 23.85 parts by mass, ethanol 15.79 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex Aqueous coating agent B15 was produced by mixing 3.02 parts by mass of O-33 (manufactured by Nissan Chemical Industries, Ltd.) and 0.61 parts by mass of Thululia 1110 (manufactured by JGC Catalysts and Chemicals).
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B15.

Example 16
An aqueous coating agent B16 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B16-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 22.98 parts by mass, ethanol 15.79 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex Aqueous coating agent B16 was produced by mixing 3.18 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 0.34 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
Using the obtained aqueous coating agent B16, a laminate was prepared in the same manner as in Example 1.

Example 17
An aqueous coating agent B17 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B17-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 28.06 parts by mass, ethanol 17.11 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.17 parts by mass, antistatic Agent, anionic surfactant (sulfosuccinate): Lipal 870P (manufactured by Lion Corporation, 0.2% water dilution) 1.16 parts by mass, Snowtex O-33 (manufactured by Nissan Chemical Industries) 1.53 parts by mass Part, through rear 1110 (manufactured by JGC Catalysts & Chemicals Co., Ltd.) 3.02 parts by mass, aqueous coating agent B17 was produced.
Using the obtained aqueous coating agent B17, a laminate was produced in the same manner as in Example 1.

Example 18
An aqueous coating agent B18 was produced in the same manner as in Example 1 except that the aqueous coating agent was changed to the following formulation in Example 1.
-Production of aqueous coating agent B18-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 35.96 parts by mass, ethanol 17.11 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 3.95 parts by mass, antistatic Agent (metal oxide particle dispersion): 1.24 parts by mass of Celnax CXS-204IP (manufactured by Nissan Chemical Industries), 2.13 parts by mass of Snowtex O-33 (manufactured by Nissan Chemical Industries, Ltd.), 1110 (through JGC) Aqueous coating agent B18 was produced by mixing 4.20 parts by mass of Catalyst Kasei Co., Ltd.).
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B18.

Example 19
When the aqueous coating agent B1 obtained in Example 1 was applied using a wire bar, it was applied in the same manner as in Example 1 except that the film was formed by applying with a coating amount such that the dry film thickness was 40 nm. A laminate was produced.

Example 20
When the aqueous coating agent B1 obtained in Example 1 was applied using a wire bar, it was applied in the same manner as in Example 1 except that the film was formed by applying with a coating amount such that the dry film thickness was 70 nm. A laminate was produced.

Example 21
When the aqueous coating agent B1 obtained in Example 1 was applied using a wire bar, it was applied in the same manner as in Example 1 except that the film was formed by applying with a coating amount such that the dry film thickness was 300 nm. A laminate was produced.

[Example 22]
When the aqueous coating agent B1 obtained in Example 1 was applied using a wire bar, it was applied in the same amount as that of Example 1 except that the dry film thickness was 400 nm to form a film. A laminate was produced.

Example 23
In Example 8, an aqueous coating agent B19 was produced in the same manner as in Example 8, except that the aqueous coating agent was changed to the following formulation.
-Production of aqueous coating agent B19-
Silicate oligomer liquid A7 41.28 parts by mass, pure water 28.06 parts by mass, ethanol 17.11 parts by mass, aluminum chelate D 1.75 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) ) 2.29 parts by mass, Ripar 870P 1.17 parts by mass, Snowtex O-33 (Nissan Chemical Industry Co., Ltd.) 1.57 parts by mass, Sululia 1110 (JGC Catalysts & Chemicals Co., Ltd.) 3.10 parts by mass are mixed. Thus, an aqueous coating agent B19 was produced.
Using the obtained aqueous coating agent B19, a laminate was produced in the same manner as in Example 1.

[Comparative Example 1]
-Preparation of silicate oligomer liquid A8-
2. 1.54 parts by mass of silicate MS-51 (Mitsubishi Chemical Corporation), 40.74 parts by mass of ethanol, 51.94 parts by mass of pure water, Emalex 715 (manufactured by Nippon Emulsion Co., Ltd., diluted with 0.5% pure water) Silicate oligomer liquid A8 was produced by mixing 97 parts by mass and stirring for 24 hours or more.
The obtained silicate oligomer liquid A8 was applied on the glass substrate used in Example 1 with a wire bar so as to have a dry film thickness of 150 nm, and a laminate was produced in the same manner as in Example 1.

[Comparative Example 2]
In Example 1, the aqueous coating agent was produced like Example 1 except having changed the aqueous | water-based coating agent into the following prescription.
-Production of aqueous coating agent B20-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 22.52 parts by mass, ethanol 15.26 parts by mass, EMALEX 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, through rear 1110 Aqueous coating agent B20 was produced by mixing 5.46 parts by mass (manufactured by JGC Catalysts & Chemicals).
Using the obtained aqueous coating agent B20, a laminate was produced in the same manner as in Example 1.

[Comparative Example 3]
In Example 1, the aqueous coating agent was produced like Example 1 except having changed the aqueous | water-based coating agent into the following prescription.
-Production of aqueous coating agent B21-
Silicate oligomer liquid A1 41.28 parts by mass, pure water 22.52 parts by mass, ethanol 15.26 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 2.16 parts by mass, Snowtex The aqueous coating agent B21 was produced by mixing 5.46 mass parts of OYL (Nissan Chemical Industry Co., Ltd.).
Using the obtained aqueous coating agent B21, a laminate was produced in the same manner as in Example 1.

[Comparative Example 4]
In Example 2, an aqueous coating agent was prepared in the same manner as in Example 2 except that the aqueous coating agent was changed to the following formulation.
-Production of aqueous coating agent B22-
Silicate oligomer liquid A2 41.28 parts by mass, pure water 31.66 parts by mass, ethanol 18.24 parts by mass, Emarex 715 (manufactured by Nippon Emulsion Co., Ltd., 0.5% pure water dilution) 0.02 parts by mass, Snowtex Aqueous coating agent B22 was produced by mixing 1.56 parts by mass of O-33 (manufactured by Nissan Chemical Industries) and 3.08 parts by mass of Thululia 1110 (manufactured by JGC Catalysts & Chemicals).
The solid content of the surfactant in Comparative Example 4 is 0.005% by mass with respect to the total solid mass of the aqueous coat, and is an aqueous coat outside the scope of the present invention.
A laminate was produced in the same manner as in Example 1 using the obtained aqueous coating agent B22.

Tables 2 and 3 below show the formulations and film thicknesses of the aqueous coating agents used in Examples 1 to 23 and Comparative Examples 1 to 4. In Tables 2 and 3, “Y” in the column of “water” means that water is contained.
[Evaluation]
Performance evaluation was performed on the following items for a laminate having a film formed using the produced aqueous coating agent. The evaluation results are shown in Table 4 below.

(1. Optical properties)
1-1. Transmittance Integral sphere transmission using light with a wavelength of 300 nm to 1400 nm using a device in which an integrating sphere attachment device (ISR-2200, Shimadzu Corp.) is connected to an ultraviolet visible infrared spectrophotometer (UV-3600, Shimadzu Corp.) Calculated from the rate.
The average transmittance at a wavelength of 300 nm to 1400 nm was calculated, and the improvement in transmittance relative to the glass substrate on which no film was formed was evaluated according to the following criteria. In the following criteria, it is evaluated that C or more is a transmittance having no practical problem.
A: The transmittance improvement is 1.8% or more.
B: The transmittance improvement is 1.0 or more and less than 1.8%.
C: The transmittance improvement is 0.2% or more and less than 1.0%.
D: The transmittance improvement is less than 0.2%.

1-2. Haze Haze measurement was performed with a haze meter NDH700 manufactured by Nippon Denshoku Industries Co., Ltd. The amount of increase in haze relative to the glass substrate not forming a film was evaluated according to the following criteria.
In the following criteria, B or higher is evaluated as a haze having no practical problem.
A: Increase in haze is less than 0.5% relative to glass substrate B: Increase in haze is not less than 0.5% and less than 2% relative to glass substrate C: Increase in haze is 2 relative to glass substrate %more than

(2. Antifouling property)
2-1. Surface Resistance Using Hiresta MCP-HT450 manufactured by Mitsubishi Chemical Analytech Co., Ltd., the surface resistance value of the film on the surface of the laminate was measured and evaluated according to the following criteria.
In the following criteria, it is evaluated that B or more is a surface resistance having no practical problem.
A: The surface resistance of the film is 1 × 10 ¹⁰ Ω / sq. It is as follows.
B: The surface resistance of the film is 1 × 10 ¹⁰ Ω / sq. Exceeding 1 × 10 ¹¹ Ω / sq. It is as follows.
C: The surface resistance of the film is 1 × 10 ¹¹ Ω / sq. Exceeding 1 × 10 ¹² Ω / sq. It is as follows.

2-2. Ocher adhesion The antifouling property of the film on the surface of the laminate was evaluated by resistance to adhesion of ocher.
The operation of sprinkling the holbein natural ocher pigment evenly over the film of the laminate and then hitting and dropping the back surface was repeated 5 times. The amount of ocher adhering to the film was visually confirmed and evaluated according to the following criteria. In the following criteria, it is evaluated that B or more is ocher adhesion having no practical problem.
A: Almost no ocher pigment is observed on the film surface, and the laminate is visually colorless and transparent.
B: Although adhesion of ocher pigment is observed, the adhesion area is 30% or less with respect to the total surface area of the film.
C: Adhesion of ocher pigment is observed, and the adhesion area exceeds 30% with respect to the total surface area of the film.
(Including cases where loess pigment is attached to the entire surface)

(3. Detergency)
3-1. Water contact angle The surface hydrophilicity of the membrane was evaluated by the water contact angle. As water, pure water was used, the contact angle with pure water was measured 5 times, and the average value was defined as the contact angle value, and evaluated according to the following criteria.
In the following criteria, B or higher is evaluated as hydrophilic with no problem in practical use.
A: The contact angle of water is 15 ° or less.
B: The contact angle of water exceeds 15 ° and is 25 ° or less.
C: Water contact angle exceeds 25 ° 3-2. Cleaning evaluation Antifouling property “2-2. Adhesion of loess” The sample (10 cm × 10 cm, which was not subjected to the work of removing the ocher by hitting the back of the laminate) with the ocher pigment used was applied to 20 ml of pure water. After flowing and drying, the amount of ocher pigment remaining on the film surface was visually observed and evaluated according to the following criteria.
In the following criteria, it is evaluated that B or higher is a cleanability having no practical problem.
A: Almost no ocher pigment is observed on the surface of the film after washing, and the laminate is colorless and transparent visually.
B: Although adhesion of ocher pigment is observed after washing, the adhesion area is 20% or less with respect to the total surface area of the film.
C: The adhesion area of the ocher pigment after washing exceeds 20% with respect to the total surface area of the film.

(4. Planar evaluation: repelling)
When forming the laminate, the aqueous coating agent to be evaluated is applied on a 10 cm × 10 cm glass substrate using a wire bar so that the coating film thickness is 150 nm, and the surface shape of the coating film after drying is applied. Were observed with an optical microscope and evaluated according to the following criteria.
In the following criteria, B or higher is evaluated as a surface having no practical problem.
A: The number of repellings in which no nucleus is seen is 1 or less in a plane having an area of 10 cm × 10 cm.
B: The number of repellings in which no nuclei are observed is more than 1 and 3 or less in a plane having an area of 10 cm × 10 cm.
C: The number of repellings in which no nuclei are observed is a number exceeding 3 in a plane having an area of 10 cm × 10 cm.
(Including cases where the film is not formed uniformly)
The above-mentioned “repellency without nuclei” means a spot-like spot where the surface of the coated film after drying is observed with an optical microscope and no foreign matter is observed at the center and no coated film is present. To do. Since the surface of the glass substrate is exposed at the spot-like portion where the coating film does not exist, a step is generated and can be easily observed with an optical microscope.

(5. Hydrolysis time)
When preparing the silicate oligomer liquid, the hydrolysis time was determined from the relationship between the stirring time and the water contact angle of the oligomer liquid coating film.
When the hydrolysis time is not sufficient, the contact angle of the oligomer liquid coating film tends to decrease with the stirring time. However, when the hydrolysis is completed, the contact angle shows a constant value regardless of the stirring time thereafter.
A: The stirring time until the contact angle of the oligomer liquid coating film is stabilized is less than 15 hours.
B: The stirring time until the contact angle of the oligomer liquid coating film is stabilized is 15 hours or more.

From the results in Table 4, the film formed on the laminate produced using the aqueous coating agent of the example was a colorless transparent uniform film. The film was excellent in transparency, hydrophilicity, and antifouling properties, and the adhered contaminants could be easily washed away with water.
The comparative example 1 which does not add a silica particle was inferior in transparency and antifouling property.
Comparative Example 2 using only hollow silica particles has poor antifouling properties, and Comparative Example 3 using only small particle size silica particles has poor transparency. For this reason, the effect of this invention was not acquired with the addition system of a single silica particle.
Moreover, in the case of the comparative example 4 with less surfactant content than the range of this invention, a uniform film | membrane was not obtained and evaluation could not be performed.

By using the aqueous coating agent of the present invention, a film having excellent transparency can be formed. Since the formed film has a property that the surface hydrophilicity is good, the antifouling property is also excellent.
For this reason, it is used suitably for the surface protection material of various members which require transparency and durability, an optical device, etc. Especially, it is useful as a surface protection material of a solar cell module.

The disclosure of Japanese Patent Application No. 2014-054190 filed on March 17, 2014 is incorporated herein by reference in its entirety.
All documents, patent applications, and technical standards mentioned in this specification are to the same extent as if each individual document, patent application, and technical standard were specifically and individually described to be incorporated by reference, Incorporated herein by reference.

Claims

Water, a siloxane oligomer represented by the general formula (1), hollow silica particles, silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles, and a surfactant,
The aqueous coating agent whose content of surfactant is 0.01 mass% or more with respect to the total solid content mass of an aqueous coating agent.

In general formula (1), R 1 , R 2 , R 3 , and R 4 each independently represents a monovalent organic group having 1 to 6 carbon atoms. n represents an integer of 2 to 20.
The aqueous coating agent according to claim 1, comprising a catalyst for promoting condensation of the siloxane oligomer.
The aqueous coating agent according to claim 1 or 2, wherein the hollow silica particles have an average primary particle diameter of 75 nm or less.
The content of the hollow silica particles is 3% by mass or more and 90% by mass with respect to the total mass of the hollow silica particles contained in the aqueous coating agent and the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles. The aqueous coating agent according to any one of claims 1 to 3, wherein the aqueous coating agent is not more than%.
The aqueous coating agent according to any one of claims 1 to 4, wherein the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles have an average primary particle size of 50 nm or less.
6. The aqueous coating agent according to claim 1, wherein n in the general formula (1) is 3 to 12.
The aqueous coating agent according to any one of claims 1 to 6, comprising an antistatic agent.
The content of the siloxane oligomer represented by the general formula (1) is 3% by mass or more and 70% by mass or less based on the total solid content in the aqueous coating agent. The aqueous coating agent according to Item.
The aqueous coating agent according to any one of claims 1 to 8, wherein the content of the hollow silica particles is 1% by mass or more and 60% by mass or less with respect to the total solid mass contained in the aqueous coating agent.
The content of silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles is 5% by mass or more and 95% by mass or less based on the total solid content mass contained in the aqueous coating agent. The aqueous coating agent according to any one of claims 9 to 9.
The total content of the hollow silica particles and the silica particles having an average primary particle size smaller than the average primary particle size of the hollow silica particles is 30% by mass or less based on the total solid content mass contained in the aqueous coating agent. The aqueous coating agent according to any one of claims 1 to 10.
At least one siloxane compound selected from the siloxane oligomer represented by the general formula (1) and the condensate of the siloxane oligomer represented by the general formula (1), hollow silica particles, and average primary particles of the hollow silica particles A film containing silica particles having an average primary particle diameter smaller than the diameter and a surfactant and having a film thickness of 50 nm to 350 nm.

In general formula (1), R 1 , R 2 , R 3 , and R 4 each independently represents a monovalent organic group having 1 to 6 carbon atoms. n represents an integer of 2 to 20.
A method for producing a film having a dry film thickness of 50 nm to 350 nm, comprising applying the aqueous coating agent according to any one of claims 1 to 11 on a substrate and drying the film.
A laminate having the film according to claim 12 or the film obtained by the production method according to claim 13 on a glass substrate.
A solar cell module comprising the laminate according to claim 14.