JP2012246440A - Inorganic coating composition - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inorganic coating composition capable of imparting both high light transmittance and mechanical strength to a base material having an inorganic coated film formed (manufactured) thereon by coating the inorganic coating composition to the base material and thereafter heat treating the coated base material at a low-temperature region of about 150°C.SOLUTION: The inorganic coating composition contains (a) a nonaggregated spherical silica microparticle, (b) an alkoxysilane and/or a hydrolyzate of its condensed compound, (c) a silane coupling agent, and (d) a curing catalyst, wherein (a) the silica microparticle is composed of a combination of (a1) a silica microparticle having a particle diameter of 3 nm to 7 nm and (a2) a silica microparticle having a particle diameter of 10 nm to 25 nm.

Description

  The present invention relates to an inorganic coating composition.

  Conventionally, a low-refractive-index coating film is applied on a display surface substrate such as a cathode ray tube or a liquid crystal, a solar cell panel surface substrate, and the difference in refractive index between the substrate and the coating film is used. A technique for improving the light transmittance by reducing the reflectance of the display surface, the panel surface, or the like is well known. The refractive index of the coating film can be lowered by using an inorganic low refractive index material as the composition of the coating film and providing voids in the coating film. Moreover, a reflectance can be further reduced by providing moderate unevenness | corrugation to the surface of this coating film. As the coating composition for forming the coating film, it is common to use silica particles that have a low refractive index and are inexpensive.

  For example, in Patent Document 1, an inorganic coating composition containing a silica fine particle solution having a particle size of 5 nm to 30 nm and an alkoxysilane compound or a hydrolyzate of metal alkoxysilane is coated on a substrate such as glass or film. And the method of improving light transmittance by reducing the reflectance of a base material is proposed.

  Moreover, in patent document 2, what hydrolyzed the metal alkoxide in the presence of the non-aggregated silica having an average particle diameter of 40 to 1000 nm and / or the chain aggregated silica fine particles having an average primary particle diameter of 10 to 100 nm is inorganic. Used as a coating composition. A method of forming a low-reflection coating film having low reflectance and excellent wear resistance by coating the inorganic coating composition onto glass has been proposed.

JP-A-8-122501 (published on May 17, 1996) JP 2001-278637 (released on October 10, 2001)

  By the way, in the said technical field, there exists a low processing temperature as one of the subjects at the time of forming the inorganic coating film aiming at low reflection and high light transmittance on a base material. For example, when the inorganic coating film is formed using glass as a base material and in a process continuous with the glass production process, the inorganic coating film is subjected to a high-temperature treatment at 300 ° C. to 800 ° C. in the process. There is no particular problem. However, when the glass manufacturing process and the process of forming the inorganic coating film are different (not continuous), it is necessary to perform high temperature treatment again on the cooled glass. In view of power consumption, an inorganic coating composition that can be processed at the lowest possible temperature is desirable. Moreover, when using a plastic film as a base material, since the heat-resistant temperature of a plastic film is low, it is necessary to lower the processing temperature.

  Although Patent Document 1 has a description that “the processing temperature is 100 ° C. to 500 ° C.”, the heat treatment is actually performed under a high temperature condition of 300 ° C. in the examples. In addition, there is an example in which heat treatment is performed at 120 ° C. to 150 ° C., which is a relatively low temperature region, but it is necessary to use a UV curing agent in combination.

  In the technique disclosed in Patent Document 2, a high processing temperature of 200 ° C. or higher, preferably 400 ° C. or higher, more preferably 600 ° C. or higher is required.

  When forming an inorganic coating film on a substrate, a conventional inorganic coating composition requires a treatment at a high temperature or a treatment in a low temperature region of about 150 ° C. in combination with a UV curing agent. That is, heat treatment in a low temperature region of about 150 ° C. is performed without using a UV curing agent, and both high light transmittance and mechanical strength are imparted to the substrate on which the inorganic coating film is formed. There are no possible inorganic coating compositions.

  The present invention has been made in view of the above-described conventional problems. The purpose of the present invention is to form an inorganic coating film by performing heat treatment in a low temperature region of about 150 ° C. after coating on a substrate ( It is to provide an inorganic coating composition capable of imparting both high light transmittance and mechanical strength to a manufactured substrate.

  In view of the above-mentioned problems, the present inventors diligently studied a technique for reducing the processing temperature when forming (manufacturing) an inorganic coating film on a substrate. The present inventors pay attention to silica fine particles that are raw materials of inorganic coating compositions used for forming (manufacturing) an inorganic coating film, and have a small particle diameter of 3 to 7 nm that has not been used alone in this technical field. Even when the inorganic coating composition is heat-treated at a low temperature of about 150 ° C., it is possible to use a combination of silica fine particles and silica fine particles having a relatively large particle size of 10 to 25 nm. The inventors have uniquely found that a substrate with an inorganic coating film having both performances of mechanical strength can be formed (manufactured), and have completed the present invention.

  That is, the inorganic coating composition of the present invention comprises (a) non-agglomerated spherical silica fine particles, (b) a hydrolyzate of alkoxysilane and / or a condensed compound thereof, (c) a silane coupling agent, A curing catalyst, wherein the (a) silica fine particles comprise a combination of (a1) silica fine particles having a particle size of 3 nm to 7 nm, and (a2) silica fine particles having a particle size of 10 nm to 25 nm. Yes.

  In a preferred embodiment of the present invention, the two kinds of silica fine particles (a1) and (a2) in the inorganic coating are in a ratio of 65:35 to 97: 3 in terms of solid content weight.

  In a preferred embodiment of the present invention, the (d) curing catalyst in the inorganic coating is an amphoteric metal chelate metal compound or a tertiary amine compound.

  In a preferred embodiment of the present invention, the (d) curing catalyst in the inorganic coating is an aluminum metal chelate compound.

  In another embodiment of the present invention, the method includes a coating step of coating the substrate with the inorganic coating composition, and a heating step of heating the substrate coated with the inorganic coating composition in the coating step. This is a method for producing an inorganic coating film.

  In another embodiment of the present invention, it comprises (a) non-agglomerated spherical silica fine particles, (b) a hydrolyzate of alkoxysilane and / or a condensed compound thereof, and (c) a silane coupling agent, The (a) silica fine particles are an inorganic coating film comprising a combination of (a1) silica fine particles having a particle diameter of 3 nm to 7 nm and (a2) silica fine particles having a particle diameter of 10 nm to 25 nm.

  The inorganic coating composition of the present invention has an effect that both high light transmittance and mechanical strength can be imparted to the substrate by treatment in a low temperature region of about 150 ° C.

  One embodiment of the present invention will be described in detail below, but the scope of the present invention is not limited to these explanations, and modifications other than the following exemplifications are made as appropriate without departing from the spirit of the present invention. Can be implemented.

  In the present specification, “A to B” indicating a range indicates “A or more and B or less”.

  The inorganic coating composition of the present invention, the inorganic coating film, and the production method thereof will be described below.

1. Inorganic coating composition <(a) Non-agglomerated spherical silica fine particles>
In the inorganic coating composition of the present invention, the silica fine particle of component (a) is a main component of the coating film of the present invention, and increases the mechanical strength of the coating film and produces a coating film having a low refractive index. And it is a component for improving the light transmittance of a base material using the refractive index difference with a base material.

  Here, in the present specification, “non-aggregated” means that silica fine particles having a chain structure are not included.

  Further, in this specification, “spherical” does not mean only a strict spherical state but also includes an elliptical shape.

  The silica fine particles (a) are composed of (a1) silica fine particles having a particle size of 3 nm to 7 nm, and (a2) silica fine particles having a particle size of 10 nm to 25 nm.

  Since the silica fine particles of (a1) have a small particle size, the contact area between the silica fine particles and the contact area with the base material are increased, contributing to the improvement of the strength of the coating film and the adhesion to the base material. . The purpose of the present invention is to impart mechanical strength to the coating film by heat treatment in a low temperature region, but if the heat treatment temperature is low, strength improvement due to sintering cannot be expected, so the silica of (a1) above Fine particles are essential.

  However, as described in Patent Document 1, although there is no difference in the porosity of the coating film in the case of the silica fine particles having a small particle diameter compared to the silica fine particles having a large particle diameter, the coating film has a small particle diameter. Unevenness on the surface is hardly formed, and sufficient light transmittance cannot be improved. Even in the present invention, the silica fine particles (a1) alone could not maintain a sufficient light transmittance.

  In addition to the silica fine particles of (a1) above, the light transmittance can be improved while maintaining the mechanical strength by adding the silica fine particles of (a2) having a particle diameter larger than that of the silica fine particles of (a1). I understood that. Initially, when the silica particles of (a1) and (a2) with different particle diameters are combined, the filling rate is improved compared to the case of (a1) silica particles alone, and the refractive index of the coating film is improved by reducing the voids. With this, the light transmittance was expected to decrease. However, it has been found that by combining the two, contrary to expectation, the effect described above, that is, the effect of improving the light transmittance can be obtained. Although the exact mechanism has not been elucidated, it is thought as follows. On the surface of the coating film in which the silica fine particles of (a1) and (a2) are combined, it is considered that (a2) the head of the particles comes out. The reflection angle of a part of the light reflected on the surface of the large particles is greater than 90 ° with respect to the incident light. At this time, since the reflected light is reflected to the coating film side, as a result, the amount of light incident on the coating film is only the silica fine particles of (a1) or the film of only silica fine particles of (a2). Compared to more.

  The particle diameter of the silica fine particles (a1) is 3 nm to 7 nm, and more preferably 4 nm to 6 nm. If it is smaller than 3 nm, the production is difficult, and the handling of the silica fine particles themselves is difficult. On the other hand, if it is larger than 7 nm, the light transmittance is lowered as described above.

  The particle diameter of the silica fine particles (a2) is 10 nm to 25 nm, more preferably 10 nm to 20 nm. When it is smaller than 10 nm, there is no difference in effect from the case of using the silica fine particle (a1) alone. On the other hand, when it is larger than 25 nm, light scattering occurs in the coating film, and haze is generated, whereby the light transmittance is lowered.

  The method for measuring the particle diameter of the silica fine particles can be determined, for example, using an electron microscope (TEM). In addition, when a solution of two types of silica fine particles is measured with a particle size measuring device using the principle of dynamic light scattering, two independent sharp peaks of the particle sizes of the silica fine particles (a1) and (a2) above are obtained. I can confirm.

  The silica fine particles of the above (a1) and (a2) are preferably in a ratio of ((a1) :( a2) =) 65:35 to 97: 3, more preferably a ratio of 70:30 to 95: 5 in terms of solid content weight. preferable. When (a1) is more than 97% of the above ratio, the light transmittance is lowered. On the other hand, when (a2) is more than 35% of the above ratio, the hardness of the coating film decreases.

  Examples of (a1) silica fine particles having a particle diameter of 3 nm to 7 nm include trade names “Snowtex OXS”, “Snowtex XS”, and “Snowtex S” manufactured by Nissan Chemical Industries, Ltd. Examples of (a2) silica fine particles having a particle diameter of 10 nm to 25 nm include, for example, trade names “Snowtex 20”, “Snowtex 30”, “Snowtex 40”, and “Snowtex O” manufactured by Nissan Chemical Industries, Ltd. , “Snowtex N”, “Snowtex C” and the like. These are all aqueous dispersions. Moreover, what substituted the water of the water dispersion by the organic solvent is marketed as the organosilica sol series. Of these, those substituted with a hydrophilic organic solvent such as methanol, ethanol, isopropyl alcohol, propylene glycol, monomethyl ether, methyl isobutyl ketone, propylene glycol, monomethyl ether acetate are preferably used.

  The silica fine particles may be acidic, basic, or neutral, but acidic or neutral silica fine particles are preferable. In the case of basic silica fine particles, the condensation of silanol groups is likely to occur when mixed with the hydrolyzate of (b) alkoxysilane and / or its condensation compound, which will be described later. Compared with acidic or neutral ones. This is because the storage stability is poor.

  The silica fine particle of component (a) is preferably 0.2 to 15% by mass, more preferably 0.3 to 10% by mass, and particularly preferably 0.5 to 5%, based on the entire inorganic coating composition of the present invention. Mass% is included. When the component (a) is more than 15% by mass, there is a problem that the storage stability of the coating liquid is deteriorated. On the other hand, when it is less than 0.2% by mass, there is a problem that it becomes difficult to coat a film having a preferable range described later.

  As a method for calculating the solid content weight of the silica fine particles, for example, quantification with an infrared spectrophotometer (IR) is possible.

<(B) Hydrolyzate of alkoxysilane and / or condensed compound thereof>
The inorganic coating composition of the present invention includes “a hydrolyzate of an alkoxysilane and / or a condensed compound thereof”, that is, “a hydrolyzate of an alkoxysilane, a condensed compound of alkoxysilane, or an alkoxysilane and the hydrolyzate”. Containing "

  In the inorganic coating composition of the present invention, the hydrolyzate of (b) alkoxysilane and / or its condensation compound (condensate) is a precursor that forms a metal oxide and a component having a coating film forming function. .

The alkoxysilane used in the component (b) can be schematically represented by the following structure.
Si (OR ₁ ) nR ₂ m (Formula (1))
(In formula (1), R ₁ represents an alkyl group, R ₂ represents an alkyl group or an aralkyl group, n represents 3 or 4, and m represents 1 or 0.)
In formula (1), each R ₁ is independently a substituted or unsubstituted linear or branched alkyl group, preferably a substituted or unsubstituted linear or branched group having 1 to 4 carbon atoms. It is an alkyl group, More preferably, it is a C1-C4 unsubstituted linear or branched alkyl group, More preferably, it is an unsubstituted C1-C2 alkyl group. When R ₁ is the above preferred alkyl group, the hydrolyzability is improved, so that a hydrolyzate can be obtained efficiently.

Specific examples of R ₁ include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group are preferable, a methyl group and an ethyl group are more preferable, and a methyl group is more preferable.

In the formula (1), each R ₂ is independently a substituted or unsubstituted linear or branched alkyl group or an aralkyl group, preferably a substituted or unsubstituted linear group having 1 to 4 carbon atoms. Or it is a branched alkyl group, More preferably, it is a C1-C4 unsubstituted linear or branched alkyl group, More preferably, it is an unsubstituted C1-C2 alkyl group. When R ₂ is the preferred alkyl group, the ratio of the functional group in the volume of the alkoxysilane increases, so that sufficient coating film hardness can be imparted.

Specific examples of R ₂ include a methyl group, an ethyl group, a propyl group, an isopropyl group, an n-butyl group, a sec-butyl group, and a tert-butyl group. Of these, a methyl group, an ethyl group, a propyl group, an isopropyl group, and an n-butyl group are preferable, a methyl group and an ethyl group are more preferable, and a methyl group is more preferable.

  The alkoxysilane condensation compound used in the component (b) is obtained by condensing at least one of the above alkoxysilanes. The average degree of condensation is preferably 1-20. If it exceeds 20, the absolute amount of the functional group decreases and the curing point decreases, so that sufficient hardness cannot be secured. The average degree of condensation is more preferably 1-10. In addition, this average condensation degree can be calculated | required using the molecular weight obtained from the gel permeation chromatography in the hydrolyzate of the condensation compound of alkoxysilane.

  Specific examples of the alkoxysilane and / or its condensed compound include tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane, tetrahexyloxysilane, methyltrimethoxysilane, methyltriethoxysilane, ethyltrimethoxysilane, ethyltriethoxy. Silanes and their condensates are preferred, and tetramethoxysilane, its condensates, and methyltrimethoxysilane are more preferred. In the present invention, only one kind of alkoxysilane and its condensate may be used, or two or more kinds may be used in combination.

  The condensate of the alkoxysilane can be prepared by hydrolytic condensation of any appropriate alkoxysilane. Commercially available products may be used as the condensate of tetramethoxysilane and the condensate of tetraethoxysilane. Examples of the commercial products include trade names “MKC silicate MS51”, “MKC silicate MS56”, “MKC silicate MS57”, and “MKC silicate MS60” (all of which are condensates of tetramethoxysilane) manufactured by Mitsubishi Chemical Corporation; Colcoat Trade names “Ethyl silicate 40” and “Ethyl silicate 48” (both are condensates of tetraethoxysilane); Examples of commercially available condensates of tetraalkoxysilanes containing different alkyl groups include, for example, trade names “MKC silicate MS56B15”, “MKC silicate MS56B30”, “MKC silicate MS58B15”, “MKC silicate MS58B15”, “ MKC silicate MS56I30 "," MKC silicate MS56F20 "; trade name" EMS-485 "manufactured by Colcoat Co .;

  When alkoxysilane and its condensate are used in combination, the alkyl groups contained may be the same or different. Specific examples of the case where the alkyl groups contained are different include the case of containing a condensate of tetramethoxysilane and the monomer tetraethoxysilane. In addition, it is preferable that the compounding quantity of the monomer tetraalkoxysilane is 100 mass parts or less with respect to 100 mass parts of condensates of tetraalkoxysilane. Tetraethoxysilane and alkyltrialkoxysilane can also be combined. Specific examples include a combination of tetramethoxysilane and methyltrimethoxysilane.

  In order to obtain the hydrolyzate of the alkoxysilane and / or its condensation compound (b), an equivalent amount or more of water is reacted with the alkoxyl group of the alkoxysilane and / or its condensation compound. Further, this reaction proceeds at room temperature, and the above component (b) (hydrolyzate) can be obtained by leaving it as a condensate of alkoxysilane in an excess amount of water in which a catalyst is present. In addition, you may heat as needed.

Since the alkoxysilane and / or its condensation compound are not sufficiently soluble in water, a hydrophilic organic solvent is usually added to make the system uniform in order to efficiently proceed with the desired hydrolysis reaction. Perform a hydrolysis reaction. Examples of such hydrophilic organic solvents include alcohols, glycols, glycol ethers or esters, and ketones. Specifically, for example, methanol, ethanol, propanol, isopropyl alcohol, R ₂ —O— (CH ₂ CH (R ₃ ) O) k—H (wherein R ₂ is an alkyl group having 1 to 4 carbon atoms). R ₃ is H or CH ₃ , and k is an integer of 1 to 3), CH ₃ —O— (CH ₂ CH (R ₄ ) O) 1 —CH ₃ (wherein R ₄ is H or CH ₃ and l is 1 or 2.), acetone, methyl ethyl ketone, diacetone alcohol, 3-methoxy-3-methyl-1-butanol and the like can be preferably used.

  The addition amount of the hydrophilic organic solvent for homogenizing the system is not particularly limited as long as it is equal to or greater than the amount capable of dissolving the alkoxysilane condensate. In this case, when high volatility is expected in the finally obtained hydrophilic treatment agent (hydrophilic coating composition), use of methanol, ethanol, isopropyl alcohol or the like is preferable. For the purpose of controlling volatility, use of butyl cellosolve, methoxypropanol or the like is preferable. Moreover, in order to obtain the hydrolyzate of alkyl trialkoxysilane and / or its condensate, you may add the hydrophobic organic solvent mixed with a hydrophilic organic solvent. As the hydrophobic organic solvent, use of toluene, xylene, methyl isobutyl ketone, n-butanol, sec-butanol, iso-butanol or the like is preferable.

  As said catalyst, what is used for a general hydrolysis reaction can be used. Since the silanol group produced by hydrolysis is likely to undergo a condensation reaction under basic conditions, it is preferable to use an acidic catalyst as the catalyst. Examples of the acidic hydrolysis catalyst include inorganic acids such as hydrochloric acid, acetic acid, nitric acid, formic acid, sulfuric acid, and phosphoric acid; formic acid, acetic acid, propionic acid, oxalic acid, paratoluenesulfonic acid, benzoic acid, phthalic acid, maleic acid Organic acids such as acids; Organotin compounds such as dibutyltin dilaurate, dibutyltin dioctiate, dibutyltin diacetate; Aluminum isopropylate, aluminum monobutoxy isopropylate, aluminum tris (acetylacetonate), aluminum bis (ethylacetoacetate) Mono (acetylacetonate), titanium tetrakis (acetylacetonate), titanium bis (butoxy) bis (acetylacetonate), titanium bis (isopropoxy) bis (acetylacetonate), zirconium tetrakis ( Cetylacetonate), zirconium bis (butoxy) bis (acetylacetonate), metal chelate compounds such as zirconium bis (isopropoxy) bis (acetylacetonate); boron compounds such as boron butoxide and boric acid; it can.

  The amount of the catalyst is not particularly limited, but it is usually preferably 0.01 to 5% by mass with respect to the silicate compound (alkoxysilane and / or condensate thereof). Normally, in a homogeneous system containing a catalyst, the target component (b) (hydrolyzate) can be obtained by leaving it at room temperature for 12 hours or more, but heating is performed to promote the hydrolysis reaction. Is also possible. Moreover, in order to perform a hydrolysis reaction reliably, you may leave it for about several days-about 10 days. In the case of using a hydrophilic organic solvent, a method in which alkoxysilane and / or a condensed compound thereof is dissolved in the hydrophilic organic solvent, and after adding a hydrolysis catalyst, an excessive amount of water is gradually added. Can take.

  The component (b) thus obtained is generally obtained in the form of a transparent aqueous solution. When a hydrolyzate is to be isolated therefrom, a condensation reaction between the components (b) Since there exists a possibility that it may advance, it is preferable to use the aqueous solution obtained by hydrolyzing as it is.

  The (a) silica fine particles and the (b) hydrolyzate of alkoxysilane and / or condensate thereof contained in the inorganic coating composition of the present invention are in the weight ratio of solids ((a) :( b) =) 85:15 to 65:35 is preferable, 85:15 to 70:30 is more preferable, and 85:15 to 75:25 is particularly preferable. (A) When there are more silica fine particles than 85% of the said ratio, a reactive point will decrease and it will be hard to express hardness. On the other hand, when (b) the hydrolyzate of alkoxysilane and / or its condensate is more than 35% of the above ratio, the voids in the coating film are filled and the refractive index of the coating film increases, so that sufficient light transmission The rate cannot be secured.

<(C) Silane coupling agent>
In the inorganic coating composition of the present invention, the silane coupling agent of component (c) has both a reactive functional group of the alkoxyl group and a reactive functional group other than the alkoxyl group, and is added to the coating composition. By this, it is a component which produces the function of the strength improvement by hardening inside a coating film, and the adhesive improvement with a base material. In particular, the coating film obtained from the coating composition of the present invention may be used for applications that are exposed to the outdoors for a long period of time, such as an article to be coated on the surface of a solar cell substrate. The coupling agent is an essential component for long-term durability.

  The above (c) silane coupling agent is not particularly limited. For example, vinyltris sold by Shin-Etsu Chemical Co., Ltd., Momentive Performance Materials, Toray Dow Corning, Evonik Degussa Japan, Chisso, etc. Methoxysilane, vinyltriethoxysilane, γ-aminopropyltrimethoxysilane, γ-aminopropylethoxysilane, N- [2- (vinylbenzylamino) ethyl] -3-aminopropyltrimethoxysilane, γ-methacryloxypropylmethyl Dimethoxysilane, γ-methacryloxypropyltrimethoxysilane, γ-methacryloxypropylmethyldiethoxysilane, γ-methacryloxypropyltriethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropylmethyl Rudiethoxysilane, γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropylmethyldimethoxysilane, 2- (3,4-epoxycyclohexyl) ethyltrimethoxysilane, N-β (aminoethyl) γ-aminopropyl Trimethoxysilane, N-β- (aminoethyl) -γ-aminopropyltriethoxysilane, N-β- (aminoethyl) -γ-aminopropylmethyldimethoxysilane, N-phenyl-γ-aminopropyltrimethoxysilane, γ-mercaptopropyltrimethoxysilane and the like can be mentioned. Among them, it is more preferable to use a silane coupling agent having a glycidyl group because it has a particularly excellent effect in improving adhesion.

  The (c) silane coupling agent contained in the inorganic coating composition of the present invention is a solid with respect to a total of (a) silica fine particles and (b) a hydrolyzate of alkoxysilane and / or a condensed compound thereof. The weight ratio of (min of (a and b)): (c) =) is preferably 100: 1 to 100: 20, more preferably 100: 3 to 100: 15, and particularly preferably 100: 3 to 100: 10 preferable. When the silane coupling agent is more than 20% of the above ratio, the hardness is lowered, the refractive index of the coating film is lowered, and sufficient light transmittance cannot be ensured. On the other hand, if the amount of the silane coupling agent is less than 1% of the above ratio, the adhesion to glass is lowered, and there is a possibility that the adhesion is lowered particularly in a long-term durability test.

<(D) Curing catalyst>
In the inorganic coating composition of the present invention, the curing catalyst of the component (d) is contained in the coating composition of the present invention, so that the curing reaction of the components (a), (b) and (c) is performed in a relatively low temperature region. However, it is a component having a function for promoting.

  The curing catalyst used in the present invention is not particularly limited, and examples thereof include metal catalysts that chelate or ion bond with silanol groups, basic catalysts such as amines, and acidic catalysts such as nitric acid. Among these, a metal catalyst that forms a chelate bond or an ionic bond with a silanol group, or a basic catalyst is preferable. This is because a three-dimensional cross-linking reaction is preferable to ensure a high coating strength, but in the case of an acidic catalyst, a curing reaction tends to occur two-dimensionally, so that a sufficient coating strength cannot be ensured.

  Examples of the metal that the metal catalyst has include aluminum, titanium, and zirconium. Specific metal catalyst components include aluminum isopropylate, aluminum monobutoxy isopropylate, aluminum tris (acetylacetonate), aluminum bis (ethylacetoacetate) mono (acetylacetonate), titanium tetrakis (acetylacetonate), titanium Bis (butoxy) bis (acetylacetonate), titanium bis (isopropoxy) bis (acetylacetonate), zirconium tetrakis (acetylacetonate), zirconium bis (butoxy) bis (acetylacetonate), zirconium bis (isopropoxy) Examples thereof include metal alkoxides such as bis (acetylacetonate), metal chelate compounds, and the like. Among these, metal chelate compounds are preferable from the viewpoint of reaction rate, and moreover, a catalyst containing an amphoteric metal chelate metal compound (aluminum (aluminum) metal chelate compound) is more preferable in view of availability. These metal catalysts may be used alone or in combination of two or more.

  The metal catalyst not only contributes to the improvement of the mechanical strength of the coating film, but also contributes to the maintenance of the light transmittance curve before and after the durability test of the coating film described later. Specifically, when using the inorganic coating film of the present invention for a solar cell, as described later, the inorganic coating film is set to a specific film thickness according to the wavelength spectrum of sunlight, the sensitivity band of the wavelength of the solar cell, etc. Then, the light transmittance is adjusted to maximize. However, in the absence of the metal catalyst, when the durability test is performed, the power generation efficiency of the solar cell decreases due to the movement of the top peak of the light transmittance of the inorganic coating film. On the other hand, by adding the above metal catalyst to the inorganic coating composition, it becomes possible to maintain the light transmittance of the coating film before and after the durability test, thereby increasing the power generation efficiency as initially designed. The period can be maintained.

  The basic catalyst is not particularly limited as long as it dissolves in the coating composition, and examples thereof include inorganic hydroxides such as sodium hydroxide, potassium hydroxide, calcium hydroxide, magnesium hydroxide; ammonia, monomethylamine, Amines such as dimethylamine, trimethylamine, monoethylamine, diethylamine, triethylamine, n-propylamine, isopropylamine, diisopropylamine and n-butylamine; ethanolamines such as monoethanolamine, diethanolamine and triethanolamine; N, N- Amino alcohols such as dimethylethanolamine, N, N-diethylethanolamine, N-methylethanolamine, N-methyldiethanolamine; amino such as pyridine, polyvinylamine, polyallylamine Other organic compounds having: 1,4-diazabicyclo [5.4.0] undecene-7 (DBU), 1,8-diazabicyclo [2.2.2] octane (DABCO), 1,5-diazabicyclo [ 4.3.0] nonene-5 (DBN), strong base tertiary amine compounds and the like. Of these, tertiary amine compounds are preferable, and DBU, DBN, and DABCO are more preferable. These basic catalysts may be used alone or in combination of two or more.

  The metal catalyst of the component (d) contained in the inorganic coating composition is a total of (b) a hydrolyzate of alkoxysilane and / or its condensate and (c) a silane coupling agent. The weight ratio of solids ((total of b and c) :( d) =) is 100: 1 to 100: 15, preferably 100: 1 to 100: 10. When the basic catalyst of the component (d) is used, the basic catalyst of the component (d) includes (b) a hydrolyzate of alkoxysilane and / or a condensed compound thereof, and (c) a silane coupling agent. Is a weight ratio of solids ((total of b and c) :( d) =) 100: 0.01 to 100: 5, preferably 100: 0.01 to 100 : 3. When both catalysts have a blending amount smaller than the above ratio, curing does not proceed sufficiently and the strength of the coating film is not sufficient. On the other hand, when the blending amount is larger than the above ratio, the mechanical strength is decreased and the light transmittance is decreased.

<Other components Solvent>
Water or a hydrophilic organic solvent may be added to the inorganic coating composition of the present invention. The hydrophilic organic solvent is not particularly limited, and those used in the hydrolysis reaction of alkoxysilane and / or its condensed compound can be used as they are. Water or a hydrophilic organic solvent can be blended in consideration of the desired film thickness, material of the object to be coated, surface condition, temperature and humidity at the time of coating, etc., and only one kind may be used. Two or more kinds may be used in combination.

<Other ingredients and additives>
In the inorganic coating composition of the present invention, an ultraviolet absorber, a surface conditioner, a storage stabilizer, etc. are appropriately used unless the light transmittance is inhibited depending on the state of coating, the purpose of the obtained inorganic coating film, etc. , Can be added.

<Method for producing inorganic coating composition>
As a manufacturing method of the inorganic coating composition of this invention, it is good also as a 1 liquid coating composition by mixing all the components containing (a), (b), (c) and (d) component at least. Also, from the viewpoint of storage stability of the coating composition, at least the components (a), (b), (c) and (d) are divided into two parts and mixed before coating as a two-part coating composition. May be combined. In the case of a two-part coating composition, the combination is not particularly limited, but (a) silica fine particles, (b) a hydrolyzate of alkoxysilane and / or its condensed compound, and (c) a composition of a silane coupling agent And a combination of two compositions of (d) the composition of the curing catalyst, a combination of the composition of (b) with the composition of (a), (c) and (d) above. Components other than the components (a), (b), (c) and (d) may be mixed in any composition. When an organoaluminum catalyst is included, the organoaluminum catalyst has low solubility in water, so if the organoaluminum catalyst and water are directly mixed, a hydrolysis reaction may occur locally and aggregates may be generated. is there. Therefore, in such a case, it is preferable to previously dissolve the organoaluminum compound in a hydrophilic organic solvent and then mix the resulting solution with another component (for example, water).

2. The manufacturing method of an inorganic coating film The manufacturing method of the inorganic coating film of this invention heats the base material with which the said inorganic coating composition was coated by the coating process which coats the said inorganic coating composition on a base material, and the said coating process. A heating step. In the method for producing an inorganic coating film of the present invention, the substrate is not particularly limited, but for example, the following can be used. Moreover, in the manufacturing method of the inorganic coating film of this invention, although the method of coating and a heating is not specifically limited, For example, the following conditions and methods can be used.

<Base material>
The substrate on which the inorganic coating composition of the present invention is coated mainly targets glass, plastic and the like. For example, substrates used for displays such as soda lime glass, alkali borosilicate glass, alkali-free glass, quartz glass, polycarbonate, and resin glass such as polyethylene terephthalate, lenses, windows, liquid crystal display substrates, substrates for photoelectric conversion devices, etc. Materials can be used.

<Coating method in coating process>
The method for coating the substrate with the inorganic coating composition of the present invention is not particularly limited. For example, methods such as spin coater, air spray, roll coater, dip coating, screen printing, gravure printing, and flow coating are used. It is done. Among them, it is preferable to use a spin coater in order to coat the thin film uniformly.

<Heat treatment in heating process>
The coating film coated with the inorganic coating composition of the present invention ensures the three-dimensional strength of the coating film and the adhesion to the substrate by a curing reaction by heating. The heating conditions are preferably a heating temperature of 120 ° C. to 170 ° C. and a heating time of 10 minutes to 120 minutes. When the temperature is lower than the above temperature (120 ° C.) or shorter than the above time (10 minutes), the curing does not proceed sufficiently and the mechanical strength may not be sufficiently secured. On the other hand, when the temperature is higher than the above temperature (170 ° C.) or longer than the above time (120 minutes), it may be contrary to the efficiency of production which is one of the objects of the present invention.

  As heating conditions, before heating at the above temperature, a preheating step of drying the solvent at 100 ° C. or less may be added, or a method of gradually increasing the heating temperature may be used. In addition, this reaction does not use ultraviolet reaction together.

<Film thickness after heat treatment>
The optimum value of the film thickness after the heat treatment of the inorganic coating film of the present invention can be determined based on the following well-known formula.

d = λ / 4 × (η ² −sin ² α) ^1/2 (Expression (2))
(In formula (2), d represents the film thickness of the inorganic coating film, λ represents the wavelength of incident light, η represents the refractive index of the inorganic coating film, and α represents the angle of incident light with respect to the substrate.)
Since the refractive index of the inorganic coating film of the present invention is about 1.4, when the radiant intensity of sunlight is high at 560 nm, when the incident light is 90 °, the thickness of the inorganic coating film of the present invention is about It can be seen that the light transmittance is maximized at 100 nm. Although this film thickness varies depending on the refractive index of the inorganic coating film, the wavelength of the target light beam, etc., in the present invention, it is preferably 70 to 130 nm.

3. Inorganic coating film The inorganic coating film of the present invention contains (a) non-agglomerated spherical silica fine particles, (b) a hydrolyzate of a condensation compound of alkoxysilane, and (c) a silane coupling agent. The inorganic coating film of the present invention may contain (d) a curing catalyst. Moreover, the inorganic coating film of this invention may contain components other than (a), (b), (c) and (d) component. (D) When the curing catalyst is an amine catalyst, it does not remain on the inorganic coating film. On the other hand, (d) when the curing catalyst is an aluminum catalyst, it remains in the inorganic coating film. The inorganic coating film of the present invention is obtained, for example, by heating an inorganic coating composition containing at least the components (a), (b), (c) and (d).

  Further, the inorganic coating film of the present invention comprises (a) a non-aggregated spherical silica fine particle, (a1) a combination of silica fine particles having a particle size of 3 nm to 7 nm, and (a2) a combination of silica fine particles having a particle size of 10 nm to 25 nm. It has become.

  The silica fine particles (a1) and (a2) contained in the inorganic coating film of the present invention are in a ratio of 65:35 to 97: 3 in terms of solid content weight.

  EXAMPLES Hereinafter, although an Example demonstrates this invention further more concretely, this invention is not limited by these Examples.

[Production Example 1 (b) Synthesis of hydrolyzate B-1 of alkoxysilane and / or its condensed compound]
Methyl silicate (average molecular weight 576, MKC methyl silicate MS-51, manufactured by Mitsubishi Chemical Corporation) 65 parts obtained by hydrolysis and condensation from tetramethoxysilane, ethanol 496 parts, aluminum monoacetyl acetate bis (ethyl acetoacetate) isopropanol (Hereinafter abbreviated as “IPA”) 2.6 parts of a solution (solid content 76%, aluminum chelate-D, manufactured by Kawaken Fine Chemical Co., Ltd.) was added and stirred to obtain a solution. To this was added 340 parts of ion exchanged water and hydrolyzed at 40 ° C. to obtain the hydrolyzate B-1.

[Production Example 2 (b) Synthesis of hydrolyzate B-2 of alkoxysilane and / or its condensed compound]
To 408 parts of methyltrimethoxysilane (manufactured by Tokyo Chemical Industry Co., Ltd.), 200 parts of methyl isobutyl ketone and 150 parts of IPA were added and dissolved. To this solution, 2.6 parts of an IPA solution (solid content 76%) of aluminum monoacetyl acetate bis (ethyl acetoacetate) was added and stirred to obtain a solution. A mixed solution of 162 parts of ion-exchanged water and 100 parts of isopropanol was added to this solution and hydrolyzed at 40 ° C., then diluted with propylene glycol monomethyl ether so that the solid content was 5%, and the hydrolyzate B-2 was obtained.

[Example 1]
39.8 parts of silica fine particles having a particle diameter of 4 to 6 nm (trade name “Snowtex OXS”, solid content adjusted to 10.6% with ion-exchanged water, manufactured by Nissan Chemical Industries), and a particle diameter of 10 to 20 nm 13.3 parts of silica fine particles (trade name “Snowtex O”, solid content adjusted to 10.6% with ion-exchanged water, manufactured by Nissan Chemical Industries, Ltd.) were mixed. This mixed solution was diluted with 136.6 parts of propylene glycol monomethyl ether. Subsequently, it is diluted with 140 parts of ethanol, and further 30 parts of the hydrolyzate B-1 and a solution of glycidylpropyltrimethoxysilane (trade name “KBM-403”, manufactured by Shin-Etsu Chemical Co., Ltd., solid content: 5.0% ) And 1.9 parts of an IPA solution (solid content 5%) of aluminum monoacetyl acetate bis (ethyl acetoacetate) were sequentially added to obtain a coating liquid (inorganic coating composition) 1.

[Other Examples and Comparative Examples]
About Examples 2-10 and Comparative Examples 1-5, each kind of silica fine particle to be used, the said hydrolyzate, a silane coupling agent, a curing catalyst, and other components (solvent, additive) and each preparation amount are shown in Table 1. Or except having changed into the value shown in Table 2, operation similar to Example 1 was performed and the coating liquid (inorganic coating composition) was obtained, respectively.

  In Examples 9 and 10, an IPA solution of DBU (solid content: 1.0%) was used instead of the IPA solution of aluminum monoacetyl acetate bis (ethyl acetoacetate). In Example 10, instead of propylene glycol monomethyl ether, an aqueous solution of a nonionic surfactant (trade name “Orphine EXP. 4200”, manufactured by Nissin Chemical Industry Co., Ltd., solid content: 1.0%) was used. In Comparative Example 4, silica fine particles having a particle diameter of 40 to 50 nm and having a trade name of “Snowtex OL” (solid content adjusted to 10.6% with ion-exchanged water, manufactured by Nissan Chemical Industries, Ltd.) Using.

[Coating and heat treatment]
The coating liquid 1 obtained in Example 1 and the coating liquids obtained in Examples 2 to 10 and Comparative Examples 1 to 5 were coated on a 10 cm square glass plate at 1300 rpm for 10 seconds using a spin coater, and 150 ° C. The coating film with a film thickness of 100 nm was obtained by heating and drying in a heating oven for 30 minutes.

[Results of Examples and Comparative Examples]
The resulting coating film was evaluated for light transmittance, pencil hardness, adhesion, scratch resistance, adhesion after the durability test, and scratch resistance after the durability test. The results are shown in Tables 1 and 2 above.

[Measurement conditions for each evaluation]
The measurement conditions for each evaluation performed in Examples and Comparative Examples are shown below.

[Light transmittance (transmittance)]
A spectrophotometer (trade name “MCPD-3000”, manufactured by Otsuka Electronics Co., Ltd.) was used as an instrument for measuring light transmittance. The substrate after coating with the coating solution was set, and the light transmittance at a wavelength of 560 nm was measured. In addition, since the light transmittance of the glass before an inorganic coating film is manufactured (before coating) is 92.2%, the light transmittance of the base material before coating (92.2%) from the light transmittance after coating. ) Represents the light transmittance improved by coating the coating liquid.

〔Pencil hardness〕
About the base material after coating the said coating liquid, the pencil hardness which is a coating-film hardness was measured along JIS-K5600.

[Adhesion]
About the base material after coating with the above coating solution, after cross-cutting 25 5 × 5 1 mm square grids with a cutter knife in accordance with JIS-K5600, a tape peeling test is performed and adhesion to the base material is performed. Sex was evaluated. The adhesion results are expressed as the number of grids remaining after peeling.

[Abrasion resistance (test)]
About the base material after coating the said coating liquid, the load of 500 g was applied with the No. 0000 steel wool by Nippon Steel Wool, and the said steel wool was reciprocated 10 times on the coating film. The case where no scratch was observed on the coating film was indicated as “◯”, the case where the coating film was scratched was indicated as “Δ”, and the case where the glass substrate was scratched was indicated as “X”.

[Durability test]
About the base material after coating the said coating liquid, the durability test was done using the pressure cooker tester. Specifically, after the test machine conditions were maintained at a humidity of 100% and a temperature of 121 ° C. for 48 hours, the adhesiveness and scratch resistance test were performed using the test machine after returning to room temperature and 24 hours later.

[Summary of Examples]
As shown in Table 1, the inorganic coating film produced from the inorganic coating composition of the present invention has high light transmittance and excellent mechanical strength. Moreover, since the performance is maintained also with respect to the durability test, it can be expected that the performance is maintained for a long period of time. On the other hand, as shown in Comparative Examples 1, 2, and 3, when the silica fine particles are not appropriate, it can be seen that the light transmittance or the mechanical strength is inferior to that of the present invention. Further, as shown in Comparative Examples 4 and 5, it can be seen that when the silane coupling agent or the curing catalyst is not included, the mechanical strength or the durability test is inferior.

  The inorganic coating composition of the present invention is used to produce an inorganic coating film having high light transmittance, mechanical strength, and long-term durability on a substrate such as glass or plastic. It is suitably used in fields such as photovoltaic power generation (solar cells).

  INDUSTRIAL APPLICABILITY The present invention can be used in a wide range of fields such as a hard coat for solar cells, a hard coat on a display surface such as a cathode ray tube, a liquid crystal, a glass window for vehicles, a glass window for architecture, and a show window.

Claims (6)

(A) non-aggregated spherical silica fine particles, (b) a hydrolyzate of alkoxysilane and / or its condensed compound, (c) a silane coupling agent, and (d) a curing catalyst,
The inorganic coating composition, wherein the (a) silica fine particles are a combination of (a1) silica fine particles having a particle size of 3 nm to 7 nm and (a2) silica fine particles having a particle size of 10 nm to 25 nm.   The inorganic coating composition according to claim 1, wherein the two types of silica fine particles (a1) and (a2) are in a ratio of 65:35 to 97: 3 in terms of solid content weight.   The inorganic coating composition according to claim 1 or 2, wherein the (d) curing catalyst is an amphoteric metal chelate metal compound or a tertiary amine compound.   The inorganic coating composition according to any one of claims 1 to 3, wherein the (d) curing catalyst is an aluminum metal chelate compound. A coating step of coating a substrate with the inorganic coating composition according to any one of claims 1 to 4,
A heating step of heating the substrate coated with the inorganic coating composition in the coating step. (A) non-aggregated spherical silica fine particles, (b) a hydrolyzate of alkoxysilane and / or a condensed compound thereof, and (c) a silane coupling agent,
An inorganic coating film in which (a) silica fine particles are a combination of (a1) silica fine particles having a particle diameter of 3 nm to 7 nm and (a2) silica fine particles having a particle diameter of 10 nm to 25 nm.