JP2002320917A - Production method for photocatalytic coating film and photocatalytic material - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide such a production method to manufacture a photocatalytic coating film on the surface of a base material by a wet method that possesses a good hardness, an abrasion resistance and a favorable photocatalytic activity at the same time, in addition, to provide a photocatalytic member having the sintered coating film. SOLUTION: This invention relates to a method to produce a photocatalytic coating film on the surface of a base material by applying a composition for forming a photocatalytic film comprising a crystalline titanium oxide surface- modified by using one or more kinds of substances belonging to carboxylic acids, a silicon-based binder and a solvent to the base material and sintering at 300-800 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a film using a composition capable of forming a titanium oxide-containing coating film used as a photocatalyst, and a method for producing the film using glass, metal, cement, gypsum board, The present invention relates to a member provided on a surface of a stone, a ceramic, a resin, or the like.

[0002]

2. Description of the Related Art Photocatalytic members have functions such as antifogging, self-cleaning by rainfall, and decomposition of harmful substances. Therefore, research and development are being actively conducted as environmentally friendly functional coating materials for coatings. In the production of such a photocatalytic member, a method of forming a photocatalytic functional coating film on a base material has been mainly used in order not to impair the inherent characteristics of the member.

As a method for forming the photocatalytic coating film, there are a dry method and a wet method, but it has excellent hardness and abrasion resistance enough to withstand a wide range of use conditions while maintaining sufficient photocatalytic activity. In order to form a photocatalytic film,
There are problems with each method. A dry method typified by a sputtering method, a CVD method, a plasma method, or the like has a problem that the cost is high and a film cannot be formed depending on the material and shape of the base material.

On the other hand, in a wet method such as a sol-gel method which is low in cost and can be applied to many substrates, a method using a titanium oxide sol to which various dispersants are added, a method using a titanium oxide precursor, a method using a titanium oxide sol, Various coating film forming compositions have been proposed so far, such as a method using a mixture of a binder (hereinafter, a binder component), and all of them have excellent hardness, abrasion resistance and good photocatalytic activity. It cannot be said that a combined photocatalytic coating film is formed.

[0005] Specifically, JP-A-2000-119 discloses a method utilizing a titanium oxide sol to which various additives are added.
According to No. 019, acidic titanium oxide sol, Ti in solution
^A pH of 5 to 10 consisting of a complexing agent added to prevent titanium oxide particles from binding to each other by aggregation of titanium oxide with ⁴⁺ ions and preventing aggregation of titanium oxide, and an alkali component added to adjust pH. There is a titanium oxide sol having the following formula. The coating film baked at 80 ° C. has the ability to decompose fatty acids due to photocatalytic activity, but its hardness is weak and is about 2H or less in pencil hardness.

According to JP-A-2000-290533, which is a method utilizing an organic precursor of titanium oxide,
There is a titanyl oxalate coating solution having a pH of 3.8 to 5 consisting of titanyl oxalate and ammonia added for pH adjustment, but a coating film baked at 600 ° C. has a photocatalytic activity with a pencil hardness of 9H or more. Although it is a coating film, its photocatalytic activity is weak and the decomposition rate of NO gas is about 60%.

Further, in a method in which a mixture of titanium oxide sol and a binder component is used as a main component, Japanese Patent Laid-Open No.
According to 000-273355, there is a photocatalytic paint in which β-diketone, a Ti-based or Al-based coupling agent, and a Ti alkoxide binder are combined with fine particle titanium oxide synthesized by a gas phase method. Has the ability to decompose acetaldehyde by photocatalytic activity,
The pencil hardness is weak, about 3H. Also, Japanese Unexamined Patent Application Publication No.
According to JP-A-323190 and JP-A-11-323257, β-diketone, Ti-based or Al
There is a photocatalyst paint in which a system coupling agent and an alkoxysilane oligomer binder are combined, but a coating film baked at 150 ° C. has a power of decomposing acetaldehyde due to photocatalytic activity, but its pencil hardness is weak and is about 3H to 6H. According to Japanese Patent Application Laid-Open No. 11-323191, there is a photocatalytic paint in which β-diketone, a Ti-based or Al-based coupling agent, and a fluorine-based surfactant-containing ethylsilicate hydrolyzate binder are combined with fine-particle titanium oxide. The film baked at ℃ has the power to decompose acetaldehyde by photocatalytic activity, but its pencil hardness is weak and 3
H to about 6H.

[0008]

According to the present invention, there is provided a method for producing a photocatalytic coating film having excellent hardness, abrasion resistance and good photocatalytic activity on a substrate surface by a wet method, and a method for producing the same. Provided is a photocatalytic member having a coated and fired coating.

[0009]

According to the present invention, in order to solve the above problems, at least one of (A) carboxylic acids belonging to
A photocatalytic coating film-forming composition comprising (B) crystalline titanium oxide, (C) a silicon-based binder, and (D) a solvent, which has been surface-modified using at least one kind of substance, is coated on the surface of the substrate. The present invention provides a production method for forming a photocatalytic coating film on the surface of a base material by applying and baking at a temperature of 300 to 800 ° C. In the following, unless otherwise specified, (B)
The crystalline titanium oxide is referred to as titanium oxide, and (A) the crystalline titanium oxide whose surface is modified with carboxylic acids is referred to as surface-modified titanium oxide.

In the present invention, the photocatalytic coating film-forming composition is formed on a substrate and fired at 300 to 800 ° C., thereby having both a very high surface hardness of 9H or more and a good photocatalytic activity. A photocatalytic coating can be formed. The reason that the coating film formed from the composition of the present invention achieves both the surface hardness of pencil hardness of 9H or more and the good photocatalytic activity is due to the fact that titanium oxide and the base material in the sintering region at room temperature to 300 ° C and 300 to 800 ° C. It is considered that there is an interaction between a silicon-based binder that functions to firmly bind titanium oxides to each other and a carboxylic acid substance used for surface modification of titanium oxide. In the firing range from room temperature to 300 ° C., a coating film having few defects such as internal defects and shape damage is realized due to the organic structure of the carboxylic acid, and residual hydroxyl groups (—OH) of the carboxylic acid adsorbed on the titanium oxide surface are converted to silicon. It is considered that by acting on the reaction terminal of the system binder, titanium oxide is incorporated into the network crosslinking of the binder, and a highly densified and crosslinked coating film is realized.
In addition, when the coating film in which such defects are less densified and highly densified and highly crosslinked is further baked at such a high temperature that the carboxylic acid adsorbed on the titanium oxide surface is thermally decomposed, at 300 to 800 ° C. It is considered that the reactivity of the reactive functional groups of the binder component and the surface of the titanium oxide where the carboxylic acid was thermally decomposed and disappeared increases, and a strong bond is formed at the interface between the titanium oxide and the binder. Further, it is conceivable that high-temperature treatment of titanium oxide at 300 to 800 ° C. further promotes higher crystallization of titanium oxide while maintaining a crystal form having high photocatalytic activity, and further enhances photocatalytic activity. In addition, the amount of carboxylic acid that inhibits photocatalytic activity while being a surface treatment component of titanium oxide on the surface of titanium oxide and inside the coating film is reduced by eliminating heat components at a high temperature treatment of 300 to 800 ° C. It is conceivable that the photocatalytic activity is further improved due to the increased frequency of contact with. Therefore, it is considered that a photocatalytic coating film having extremely high surface hardness, abrasion resistance and excellent photocatalytic activity was realized.

In a preferred embodiment of the present invention, the material (B) is crystalline titanium oxide particles, and the average particle size is 1 to 100 nm. The average particle size of the titanium oxide is determined in consideration of the balance between the photocatalytic activity of the coating film and the mechanical strength. Titanium oxide is in the form of fine powder, and its particle diameter is high because of its high photocatalytic activity and its high filling and improved hardness and abrasion resistance during coating film formation.
A fine thing of about 00 nm is preferable. With such a size, the scattering effect on visible light is reduced and the transparency is increased. In addition, for members such as ceramics and glass that require particularly high hardness and abrasion resistance, the particle size is preferably 30 nm or less in consideration of the balance with photocatalytic activity. To achieve higher hardness and higher wear resistance,
It is preferable to set it to 0 nm or less.

[0012] In a preferred embodiment of the present invention, the crystalline titanium oxide (B) is used in an amount of 1 to 1000 parts by weight per 1 part by weight of the carboxylic acid (A) for modifying the surface of the crystalline titanium oxide. Part. The proportion of titanium oxide and carboxylic acid is the dispersion in the composition of the present invention,
It is determined in consideration of the balance between the properties of the liquid such as viscosity, the hardness of the coating film, and the mechanical strength such as abrasion resistance. The ratio is preferably 1 to 1000 parts by weight of titanium oxide in terms of titanium dioxide with respect to 1 part by weight of carboxylic acid. If the amount of the carboxylic acid is too small, the effect of improving hardness and abrasion resistance tends to be small when a mixed solution of the surface-modified titanium oxide and the silicon-based binder is used as a coating film. If the amount is too large, the surface-modified titanium oxide alone, the production and preparation of the surface-modified titanium oxide and the silicon-based binder, a thickening effect is likely to occur in the mixed solution, and when a coating is formed, the appearance of the coating surface is poor and the hardness is low. In addition, problems such as a decrease in wear resistance are likely to occur.

In a preferred embodiment of the present invention, the silicon-based binder (C) is added in an amount of 10 to 400 in terms of silicon dioxide with respect to 100 parts by weight of the crystalline titanium oxide in terms of titanium dioxide. It should be contained by weight. Since the weight ratio of titanium oxide and the silicon-based binder affects the surface structure and internal structure of the coating film, it is determined in consideration of the balance between photocatalytic activity and mechanical strength such as coating film hardness and abrasion resistance. The ratio is 10 to 10 parts by weight of a silicon-based binder in terms of silicon dioxide with respect to 100 parts by weight of titanium oxide in terms of titanium dioxide.
It is preferred to contain 400 parts by weight. When the proportion of the silicon-based binder exceeds 400 parts by weight in terms of silicon dioxide, the photocatalytic function is reduced because the silicon-based binder covers titanium oxide. When the proportion of the silicon-based binder is 10 parts by weight or less in terms of silicon dioxide, The adhesive strength with the material and titanium oxide is weakened, and both are poor in practicality.

[0014] In a preferred aspect of the present invention, the total solid content concentration of (B) the crystalline titanium oxide in terms of titanium dioxide and (C) the silicon-based binder in terms of silicon dioxide is 20% by weight or less. I do. The total solid content concentration is the sum of values obtained by converting titanium oxide contained in the entire composition into titanium dioxide and converting a silicon-based binder into silicon dioxide. It is determined in consideration of the balance of the characteristics and the like.
As for the total solid content concentration, it is preferable to make the total solid content concentration in terms of titanium dioxide of titanium oxide and silicon dioxide of the silicon-based binder not more than 20% by weight. When the total solid concentration is 20% by weight or less, it may be set to meet various specifications (film thickness, film forming method, etc.)
If the content is more than 20% by weight, the dispersibility of the solid in the composition becomes poor, the stability of the composition is remarkably reduced, and gelation is liable to occur. On the other hand, a high concentration is not preferred because the film-forming properties and the adhesion between the film-formed body of the composition and the substrate are significantly reduced.

In a preferred embodiment of the present invention, the composition having the above-mentioned characteristics has (F) a pH of 2 to 5. The pH of the composition of the present invention is determined in consideration of the stability of the liquid at the time of producing the silicon-based binder and the surface-modified titanium oxide which are the film-forming elements, and preparing the mixture thereof. If the pH is 2 or less, or the pH is 5 or more, the silicon-based binder becomes unstable.

According to the present invention, there is provided a photocatalytic member provided with a photocatalytic coating by a method in which the above-mentioned photocatalytic coating forming composition is applied to the surface of a substrate and cured by heating at 300 to 800 ° C. According to the present invention, the composition of the present invention is formed on a substrate by 3
A photocatalytic member having a coating film formed on a substrate by heating and curing at 00 to 800 ° C. can be provided. As a substrate on which the composition of the present invention is applied, 300 to 800 ° C.
Any heat treatment condition may be used as long as problems such as discoloration, fading, deformation, and change in physical properties do not easily occur. Members having various shapes such as glass, metal, cement, wallpaper, gypsum board, stone, ceramics, or resin,
Composite moldings are conceivable. When applying to these substrates, pretreatment may be performed as necessary according to the composition and the substrate.

In a preferred embodiment of the present invention, the heat-treated and cured coating is a photocatalytic member provided with a photocatalytic coating having a surface hardness of 9H or more. According to the present invention, a coating film obtained by forming a film of the composition of the present invention on a substrate and heat-treated has a surface hardness of 9H or more in pencil hardness, and thus can be applied to members requiring surface hardness. Examples of the substrate to which the composition of the present invention is applied include members having various shapes such as glass, metal, cement, wallpaper, gypsum board, stone, ceramics, and resin, and composite molded articles. When applying to these substrates, pretreatment may be performed as necessary according to the composition and the substrate.

In a preferred embodiment of the present invention, the substrate on which the photocatalytic coating film is formed is a photocatalytic member made of ceramic or glass. According to the present invention, when the composition of the present invention is formed into a film on a substrate and heat-treated, the composition has a pencil hardness of 9H.
Since the member has a photocatalytic coating film having the above surface hardness, it can be applied to members and applications that require photocatalytic activity and surface hardness. When applying to these substrates,
Pretreatment may be performed as necessary according to the composition and the base material.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in order.

The carboxylic acids (A) include maleic acid, malonic acid, fumaric acid, oxalic acid, succinic acid, and other carboxylic acids having two or more carbonyl groups in one molecule, or malic acid, glycolic acid, and the like. , Lactic acid, tartaric acid,
Preferably, the chemical substance is selected from hydroxycarboxylic acids such as citric acid and gluconic acid. The chemical substance has two or more hydroxyl groups in one molecular structure. If two or more hydroxyl groups do not exist, the residual hydroxyl groups of the carboxylic acid modified on the surface of the titanium oxide are reduced and the action with the silicon-based binder is reduced, so that the coating film is highly densified,
It is considered that cross-linking is hardly achieved. Further, if the number of hydroxyl groups is too large, it is considered that problems such as production and adjustment of the surface-modified titanium oxide alone, the surface-modified titanium oxide and the silicon-based binder, and aggregation and thickening of the mixture are caused.

The crystalline titanium oxide (B) of the above composition is irradiated with light having an energy of a specific value (about 3.2 eV) or more, so that excited electrons and holes generated by the ejection of electrons are generated. Is a crystalline titanium oxide having a photocatalytic action showing an oxidative decomposition action of organic substances and a hydrophilic action by adsorption of water molecules. The crystalline titanium dioxide particles include anatase type, brookite type and rutile type, and particularly preferably anatase type and brookite type. Further, they may be mixed. Other titanium oxides include amorphous titanium oxide, which crystallizes rapidly when heated at high temperature, and has a photocatalytic action, or a titanium oxide precursor such as hydroxy titanate or organic titanate. Reacts with the elemental components (Na element when the base material is soda lime glass; Fe element when the stainless steel sheet is used) to form crystalline titanium dioxide, and reduces the photocatalytic activity of the coating film. It will be easier.

In the production of the surface-modified titanium oxide, a sol in which crystalline or amorphous titanium oxide particles are dispersed in a dispersion medium is used, or a titanium oxide such as titanium alkoxide, titanyl sulfate or titanium tetrachloride is dispersed in a dispersion solvent. A method of forming a sol by mixing a precursor and performing a treatment such as neutralization, hydrolysis, deacidification treatment, or dealkalization treatment is suitably used. For example, when using titanyl sulfate as a starting material, the sol that has been hydrolyzed and filtered and washed at a temperature higher than room temperature is redispersed in a solvent, or an anion generated during hydrolysis is treated with an ion exchange resin. A method of adding an acid such as a carboxylic acid and, if necessary, an inorganic acid, and a method of further performing a hydrothermal treatment to improve the crystallinity are preferably used.
When titanium tetrachloride is used as a starting material, chlorine ions generated after hydrolysis at a temperature higher than room temperature or during hydrolysis are subjected to a dechlorination treatment such as electrodialysis, an ion exchange resin, and electrolysis to obtain chlorine. Ion concentration, p
A method of controlling H and adding a carboxylic acid, if necessary, an acid such as an inorganic acid, the hydrolysis using a carboxylic acid,
A method of controlling the chloride ion concentration and pH by dechlorination is suitably used. Further, a method of adding a carboxylic acid to the titanium oxide sol is also suitably used.

The (C) silicon-based binder of the composition functions to firmly bond the titanium oxide to the base material and the titanium oxide during the curing of the coating film, and to semipermanently exhibit the photocatalytic activity of the titanium oxide. . Further, it is a binder having a pH value that can be stably mixed with the surface-modified titanium oxide. The binder of the present invention, titanium oxide and a substrate,
In addition, it is preferably an uncured siloxane polymer that has a role of firmly bonding titanium oxides to each other and has a role of semipermanently exhibiting the photocatalytic activity of the titanium oxide, and is formulated to have a pH value that can be stably formulated with the surface-modified titanium oxide sol. .
The uncured siloxane polymer has a general formula R1 (n1) SiX (4-n1) (1) wherein n1 is an integer of 0 or 1. R1 has 1 to 18 carbon atoms.
Is a monovalent organic group in which one carbon atom is bonded to a silicon atom. X is chlorine, bromine, or an alkoxy group having 1 to 4 carbon atoms. A mixture of a hydrolyzable trifunctional silicon compound and a hydrolyzable tetrafunctional silicon compound represented by
It is preferable that the functional silicon compound is hydrolyzed and polycondensed under acidic conditions. More preferably, it is an uncured siloxane polymer obtained by hydrolyzing and polycondensing a hydrolyzable tetrafunctional silicon compound. Also preferably, a general formula Si (n2) O (n2-1) OR2 (2n2 + 2) (2) (where n2 is an integer of 2 to 6. R2 is an alkoxy group having 1 to 4 carbon atoms. An uncured siloxane polymer obtained by subjecting a polycondensation product of a hydrolyzable tetrafunctional silicon compound represented by the following formula to hydrolysis and polycondensation under acidic conditions. Further, the general formula: M (n3) O. (n4) SiO2 (3) (wherein, M is an element belonging to alkali metals. N3 is a numerical value determined by the valence of M. n4 is a numerical value of 1 to 8. M is Fr, Cs, Rb, K, Na, L
neutralizing a silicon compound containing an element belonging to at least one or more alkali metals such as i, an alkali metal silicate solution (hereinafter, referred to as an alkali silicate),
It may be an acidic uncured siloxane polymer obtained by performing a suitably used method such as alkali elimination by electrodialysis, ion exchange resin, or electrolysis. Further, a product obtained by adding silica fine particles to the uncured siloxane polymer, or a product obtained by reacting a silicon compound represented by the general formula (1), the general formula (2), or the general formula (3) with silica fine particles is used. It may be used.

In the silicon compound represented by the general formula (1), examples of the hydrolyzable trifunctional silicon compound include methyltrichlorosilane, methyltribromosilane, methyltrimethoxysilane, methyltriethoxysilane, and methyltriisopropoxysilane. , Methyltri-t-butoxysilane, ethyltrichlorosilane, ethyltribromosilane, ethyltrimethoxysilane, ethyltriethoxysilane, ethyltriisopropoxysilane, vinyltrichlorosilane, vinyltribromosilane, vinyltrimethoxysilane, vinyltriethoxysilane Examples thereof include silane, trichlorohydrosilane, tribromohydrosilane, trimethoxyhydrosilane, and triethoxyhydrosilane. Examples of the hydrolyzable tetrafunctional silicon compound include tetrachlorosilane, tetrabromosilane, tetramethoxysilane, tetraethoxysilane, tetrabutoxysilane,
There is dimethoxydiethoxysilane. Preferred are tetramethoxysilane and tetraethoxysilane, which are easily available and easy to obtain a high hardness when dried. In addition, the general formula (2)
Examples of the silicon compound represented by are methyl silicate 51, which is an average trimer condensation product of tetramethoxysilane, and an average pentamer condensation product of tetraethoxysilane, which are easily available and easily obtain a high hardness body when dried. Ethyl silicate 40 is preferred. Examples of the silicon compound represented by the general formula (3) include an aqueous solution of sodium silicate No. 1, an aqueous solution of sodium silicate No. 3, an aqueous solution of sodium silicate No. 4, an aqueous solution of sodium silicate No. 1, an aqueous solution of potassium silicate 1K, B potassium silicate aqueous solution, various lithium silicate aqueous solutions and the like. Other examples of the alkali silicate include ammonium silicate in which an alkali metal is reduced as much as possible and stabilized with organic amines (short-chain amines such as formaldehyde, ethylamine, and ethanolamine).

The (C) silicon-based binder of the present invention comprises:
The hydrolyzable tetrafunctional silicon compound represented by the general formula (1) or the polycondensate of the hydrolyzable tetrafunctional silicon compound represented by the general formula (2) is not hydrolyzed and polycondensed under acidic conditions. More preferably, it is a cured siloxane polymer.

In the hydrolysis of the hydrolyzable silicon compound, either an acid or an alkali can be used as a catalyst. However, considering the stability of the hydrolyzed binder component, the surface-treated titanium oxide sol, and the mixture thereof, contact with water occurs. Then, (F) it is desirable to show acidity with a pH of 2 to 5. Particularly preferred are acidic hydrogen halides, carboxylic acids, sulfonic acids, acidic or weakly acidic inorganic salts, and solid acids such as ion exchange resins. Preferable examples include hydrogen fluoride, hydrochloric acid, nitric acid, sulfuric acid; organic acids represented by acetic acid and maleic acid; methylsulfonic acid; and cation exchange resins having a sulfonic acid group or a carboxylic acid group on the surface. . The amount of the hydrolysis catalyst is preferably in the range of 0.001 to 5 mol per 1 mol of the hydrolyzable group on the silicon atom. If the pH is 2 or less, or the pH is 5 or more, the hydrolyzed binder component becomes unstable and gels easily.

The amount of water used for the hydrolysis is determined by considering the curability of the coating film, the mechanical strength and appearance of the obtained coating film, and the stability of the solution such as mixing with a surface-treated titanium oxide sol. 0.001 to 1 mol of the above hydrolyzable group
It is preferably in the range of 500 moles, preferably 0.05 to 100 moles. For the hydrolysis reaction, polar solvents such as alcohols, ketones and esters, or toluene,
It is preferable to use a non-polar solvent such as hexane as the solvent. These solvents may be used for the solvent (D) of the present invention. When halogenosilane is used as a raw material, it is necessary to sufficiently wash with water after hydrolysis to remove halogen components.

The molecular weight of the siloxane compound composed of the uncured siloxane polymer formed by partially hydrolyzing and polycondensing the hydrolyzable silicon compound monomer in this way affects the properties of the coating film. If the molecular weight is too small, defects and shape damage are likely to occur during drying and curing, and it is considered that the coating film hardness and abrasion resistance are reduced. A film having a higher molecular weight can form a film having good transparency, gloss and smoothness. The siloxane compound has a number average molecular weight of 80 determined by GPC (gel filtration chromatography) using polystyrene as a standard substance.
Those having a molecular weight of up to 20,000 are preferred.

The surface-modified titanium oxide and the silicon-based binder can be appropriately mixed. For example, a predetermined amount of an acidic aqueous dispersion of the surface-modified titanium oxide under acidic conditions is 10 to 5 times.
While maintaining the liquid temperature at 0 ° C., the weighed silicon-based binder is added dropwise thereto over a certain period of time. After dropping,
The reaction is carried out with stirring for 5 hours to prepare a composition liquid. The silicon-based binder is preferably an uncured siloxane polymer obtained by previously subjecting the hydrolyzable silicon compound to hydrolysis and polycondensation under pH adjustment, and then mixing this with a surface-modified titanium oxide sol with stirring. Can be obtained. Further, a method in which a hydrolyzable silicon compound and a hydrolysis catalyst are simultaneously added to a surface-modified titanium oxide sol, and a method in which hydrolysis is promoted by utilizing an acid component present in a surface-modified titanium oxide dispersion are suitably used. . In the case of using an alkali silicate, a method in which the pH is adjusted in advance by the above-described method and the mixture is prepared is preferably used.

The solvent (D) of the composition is a substance capable of uniformly dispersing the surface-modified titanium oxide and the silicon-based binder, which are film-forming elements. For example, water or lower alcohols such as methanol, ethanol, isopropyl alcohol, n-propanol, n-butanol and isobutanol, or ketones such as methyl ethyl ketone (MEK) and methyl isobutyl ketone (M
IBK). Preferably, it is water or the lower alcohols. Also, the diluent for diluting the composition,
Water and organic solvents can be used. Alcohols, ketones, esters and ethers are suitable as organic solvents.

The pH of the composition (F) is preferably in the range of 2 to 5. The pH range is advantageous for improving the stability when the components of the film-forming element are produced and prepared. If the pH is 2 or less, or the pH is 5 or more, the silicone-based binder becomes unstable and gels easily.

In the present invention, a coating composition comprising (B) crystalline titanium oxide and (C) a silicon-based binder, the surface of which has been previously modified with at least one or more substances belonging to (A) carboxylic acids, is prepared in the range of 300 to 300. By heat-treating and hardening at 800 ° C., a photocatalytic coating film having excellent hardness, abrasion resistance and good photocatalytic activity was realized. The mechanism by which the photocatalytic coating film obtained by the method for forming a photocatalytic coating film of the present invention has excellent hardness, abrasion resistance and high photocatalytic activity is not necessarily clear. However, the effect of realizing high hardness and high abrasion resistance is the weak point in the wet method in which the conventional inorganic strong acid-dispersed titanium oxide sol and the binder were mixed during drying and high-temperature sintering. It is considered that the effect of strengthening the weakness and, in addition, the effect of reducing internal defects and shape damage during drying of the photocatalytic coating film forming composition can be expected from the chemical structure of the carboxylic acid. In addition, titanium oxide alone, or mixed with a binder component, in the production,
It is also thought that there is an effect as a dispersant that reduces aggregation and precipitation of titanium oxide. The effect of realizing high photocatalytic activity is considered to be a thermal change effect of titanium oxide and carboxylic acid by high-temperature treatment. Regarding titanium oxide, it is considered that crystalline titanium oxide having a crystal form having high photocatalytic activity has an effect of high crystallization while maintaining the form by high-temperature treatment. In addition, it is considered that carboxylic acid, which is a surface treatment component of titanium oxide, has an effect of reducing and eliminating carboxylic acid which inhibits photocatalytic activity by high-temperature treatment.

The effect of strengthening the weakness of the bonding interface between the titanium oxide and the binder is as follows. In the baking range from room temperature to 300 ° C., the residual hydroxyl groups of the carboxylic acid coated on the surface of the titanium oxide particles when the coating film is dried and hardened. (-OH) acts on the reactive functional group of the silicon-based binder, so that titanium oxide can be positively incorporated as a part of the network crosslinking of the binder via the carboxylic acid. Therefore, it is considered that a high degree of densification and cross-linking were achieved even in a coating film processed by low-temperature drying.

It is also considered that in the firing range from room temperature to 300 ° C., the above-mentioned action simultaneously reduces internal defects and shape damage. As the action, the presence of the carboxylic acid having an organic structure imparts flexibility to the composition, and is reasonably effective during drying and curing, and has a small number of defects as a type of molding aid that forms a coating film. Action is possible. Therefore, it is considered that a highly densified coating film having fewer defects was realized.

Then, the coating film having a high density and high cross-linking with few defects is further heated to a high temperature of 300 to 8
When calcined at 00 ° C., the carboxylic acid adsorbed on the titanium oxide surface is thermally decomposed and disappears, the reactivity of the titanium oxide surface and the reactive functional group of the binder component is increased, and the titanium oxide and the binder are strongly bonded at the interface. It is believed that a perfect bond is formed. Therefore, it is considered that a highly densified and crosslinked coating film having fewer defects was realized.

The function as the dispersant is to reduce unevenness in film formation at the time of forming a film, poor mechanical strength and poor appearance due to aggregation and precipitation of titanium oxide. Conceivable.

Further, as the effect of improving the photocatalytic activity by the high-temperature treatment, a heat change effect of titanium oxide and carboxylic acid can be considered. 300-80 for titanium oxide
It is conceivable that the high temperature treatment at 0 ° C. causes crystalline titanium oxide to have a function of promoting high crystallization while maintaining a crystal form having high photocatalytic activity. In addition, a carboxylic acid that inhibits photocatalytic activity while being a surface treatment component of titanium oxide,
Although present on the surface of titanium oxide and inside the coating film, it is considered that the high-temperature treatment has the effect of reducing or eliminating the remaining amount.

It is considered that a coating film having not only extremely high surface hardness and abrasion resistance but also excellent photocatalytic activity can be realized by the above effects. A photocatalytic coating composed of titanium oxide and a silicon-based binder without surface modification, for which these effects cannot be expected, cannot achieve both excellent hardness, abrasion resistance and good photocatalytic activity.

In the present invention, it is more preferable that the present invention has the various features described above. Further, various additives may be appropriately added as desired. Specific examples include curing catalysts, various surfactants, thickeners, dispersants, foaming agents, silane or titanium coupling agents, and dyes.

In the present invention, a method suitable for the shape and size of the substrate to be coated is appropriately used as the coating method. For example, there are a brush coating, a spray method, a bar coater method, an applicator method, a spin coating method, a dipping method, a curtain wall method and the like. In general, it is preferable to set the total solid content of the composition to be lower as the film deposition method has a larger amount of adhesion to the substrate, but it may be appropriately changed depending on the specification of the film.

In the present invention, the heat treatment conditions necessary to apply and cure the composition to a substrate to realize a coating film having not only extremely high surface hardness and abrasion resistance but also good photocatalytic activity are as follows. , (E) 300 ° C to 800 ° C. Preferably 350-700 ° C, more preferably 400-600 ° C
It is. When a coating film that has achieved high densification and high cross-linking achieved in a low temperature region is heated at a high temperature of 300 ° C or more, the carboxylic acid adsorbed on the titanium oxide surface is thermally decomposed and disappears, and the titanium oxide surface and a binder are removed. It is considered that the reactivity of the reactive functional group of the component increases, and a strong bond is formed at the interface between the titanium oxide and the binder. In addition, on the surface of the titanium oxide, inside the coating film, the residual amount of the carboxylic acid that inhibits the photocatalytic activity is reduced by thermal decomposition and disappearance while being a surface treatment component of the titanium oxide. Since the contact frequency increases, the photocatalytic activity may be further improved. Also, titanium oxide is treated at a high temperature of 300 ° C. or more,
It is conceivable that titanium oxide is more highly crystallized while maintaining a crystal form having high photocatalytic activity, and the photocatalytic activity is further enhanced. These effects become more pronounced at higher firing temperatures. However, in the case of calcination at 800 ° C. or higher, the crystal structure of titanium oxide changes from an anatase type having a high photocatalytic activity to a rutile type having a low photocatalytic activity, which causes a reduction in photocatalytic activity.

In the film formation of the present invention, the film hardness, abrasion resistance,
In order to express photocatalytic activity and appearance in a well-balanced manner,
An important factor is not only the weight ratio of the oxide values of titanium dioxide and silicon dioxide but also the thickness of the coating film.
In the composition of the present invention, the film thickness is preferably from 10 to 1000 nm. In a specification in which transparency is also important, 10 to 300 nm is a preferable film thickness.

The present invention has a surface hardness of 9H or more in pencil hardness and abrasion resistance, which is superior to a coating agent of titanium oxide and a silicon-based binder which has been encountered with a conventional acid or alkali formed under the same high-temperature firing conditions. A photocatalytic coating can be formed. In addition, it is possible to form a high hardness photocatalytic coating film having a pencil hardness of 9H or more, which has better photocatalytic activity than a conventional titanium oxide precursor coating agent. And, since the curing of the coating film can be accelerated under lighter baking conditions or the curing time of the coating film can be shortened, items of concern for the heat treatment, for example, the properties of the base material itself are impaired, costs, etc. Can be reduced. In addition, it becomes possible to form a photocatalytic coating film having excellent hardness, abrasion resistance and good photocatalytic activity even on a member such as a building where heat treatment cannot be sufficiently performed. Therefore, the use is expanded to members which could not be applied because of insufficient surface hardness and insufficient wear resistance.

When a thin film is formed on the member surface by the above method,
The surface of the member becomes decomposable in response to photoexcitation of titanium oxide, which is an optical semiconductor. Here, in order for the substrate surface to be highly hydrophilized by optical excitation of the optical semiconductor,
The illuminance of the excitation light may be 0.001 mW / cm2 or more, preferably 0.01 mW / cm2 or more, and 0.1 mW / cm2 or more.
More preferably, it is W / cm2 or more. Light sources include sunlight, indoor lighting, fluorescent lamps, mercury lamps, incandescent lamps, xenon lamps, high-pressure sodium lamps, metal halide lamps,
BLB lamps, germicidal lamps and the like can be suitably used. However, in the case of a thin film having a thickness of 100 nm or less, even the thin film has a good absorbency of about 250 to 350 nm (preferably 30 nm).
It is preferable that a large amount of short-wavelength light (about 0 to 350 nm) is contained.

As the substrate on which the composition of the present invention is applied,
Discoloration and fading under heat treatment conditions of 300 to 800 ° C.
Any material may be used as long as defects such as deformation and change in physical properties hardly occur. For example, members having various shapes, such as glass, metal, cement, wallpaper, gypsum board, stone, ceramics, and resin, and composite molded articles are conceivable.
In particular, glass and ceramics that can withstand high-temperature processing are preferable. When applying to these substrates, it is necessary to perform a pretreatment suitable for the substrate as well as the composition.

The substrate to which the present invention can be applied includes antifogging,
When a drip-proof effect is expected, it is a transparent member, and glass, plastic, or the like can be suitably used for the material. Speaking of applicable base materials, mirrors such as rearview mirrors for vehicles, mirrors for bathrooms, mirrors for toilets, dental mirrors, road mirrors; spectacle lenses, optical lenses, illumination lenses, semiconductor lenses Lenses such as copier lenses, rear view camera lenses for vehicles; prisms; windows of buildings and towers; automobiles, railway vehicles, aircraft, ships, submersibles, snowmobiles, lowway gondola, amusement parks Gondolas, vehicle windows such as spaceships; cars, motorbikes, railcars, aircraft, ships, submersibles, snowmobiles, snowmobiles, lowway gondola, amusement park gondola, space Windshields for vehicles such as ships; protective goggles, sports goggles, protective mask shields, sports mask seals
Helmet shield, glass of frozen food display case, glass of warm food display case such as Chinese steamed bun; cover of measuring instrument, cover of camera lens for rear view confirmation for vehicle, laser Converging lenses for dental treatment devices, laser covers such as inter-vehicle distance sensors, covers for light detection sensors, covers for infrared sensors, filters for cameras, and for attaching to the surface of the article. Films, sheets, seals, patches and the like can be mentioned.

When a surface cleaning effect is expected as a substrate to which the present invention can be applied, the material may be, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, Fabrics, combinations thereof, and laminates thereof can be suitably used. Speaking of applicable base materials, building materials, building exteriors, building interiors, window frames, windowpanes, structural members, vehicle exteriors and coatings, machinery and articles exteriors, dustproof covers and coatings, traffic signs, Various display devices,
Advertising towers, noise barriers for roads, noise barriers for railways, bridges, exterior and coating of garages, tunnel interiors and coatings, insulators, solar battery covers, solar water heater collector covers, vinyl houses, vehicle lighting Light covers, housing equipment, toilets, bathtubs, washbasins, lighting fixtures, lighting covers, kitchen utensils, dishes, dishwashers, dish dryers, sinks, cooking ranges, kitchen hoods
And a film, a sheet, a seal, an emblem, and the like for sticking to the surface of the article.

When a substrate to which the present invention is applicable is expected to have a drying promoting effect, the material may be, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, Fabrics, combinations thereof, and laminates thereof can be suitably used. When the applicable substrate is used, it includes films, sheets, seals, patches, and the like to be adhered to automobile bodies, windows, pavements, and the surface of the above-mentioned articles.

The substrate to which the present invention can be applied includes deodorization,
When a sterilizing effect is expected, for example, metal, ceramic, glass, plastic, wood, stone, cement, concrete, fiber, cloth, a combination thereof, or a laminate thereof can be suitably used. . Speaking of applicable base materials, tiles, wallpaper, flooring and other interior building materials, exterior building materials, household goods in general, appliances and clothing used in nursing homes and hospitals, and films that adhere to the surface, See
And seals and patches.

[0050]

The present invention will be described more specifically with reference to the following examples. The embodiments of the present invention are not limited to these.

Example 1 29.75 g of ethanol, 3.75 g of ethyl silicate 40 (ethyl silicate pentamer, manufactured by Colcoat Co., Ltd.) 5.8 of a 2% by weight nitric acid aqueous solution
0 g was placed in a container with a lid and hydrolyzed for 5 hours while stirring in a 30 ° C. water bath to obtain a silicon-based binder.

Titanium oxide sol M-6 containing 1-1.5% by weight of malic acid and 6% by weight of a solid content of titanium oxide alone and having an average particle diameter of 6 nm (manufactured by Taki Chemical Co., Ltd.) 17.5
g, 11.25 g of the above-mentioned silicon-based binder, and 21.25 g of distilled water as a diluting solvent were added and stirred to obtain a thixotropic photocatalytic titanium oxide coating film forming composition. This composition had a weight ratio of 71:29, in which titanium oxide was converted to titanium dioxide and silicon-based binder was converted to silicon dioxide, the total solid concentration in the entire composition was 3% by weight, and the pH was 2. 54.

This composition was subjected to a rotation condition of 500 rpm × 2.
The sample was quickly spin-coated on a glass substrate at 1000 rpm × 20 seconds for 0 second, and held at 300 ° C. for 1 hour to cure to obtain a sample. The thickness of the photocatalytic coating film formed on the sample substrate was 70 to 80 nm as observed by an SEM electron microscope (manufactured by Shimadzu Corporation). This sample was designated as Example 1.

Example 2 A sample formed by the same method as in Example 1 except that the firing temperature was changed to 500 ° C. was used as Example 2. This film thickness was 70 to 80 nm.

[Comparative Example 1] As a representative of a coating agent for a titanium oxide precursor, TK using an organic titanium compound as a coating agent was used.
C305 (manufactured by Teica Corporation) was used. In the film formation, TKC containing surfactant A1225 (manufactured by Teica Co., Ltd.) was added.
Using 305, the solid content concentration was adjusted so as to have the same thickness as much as possible, and a coating film was formed using the same film forming method and firing conditions as in Example 2. In addition, the film thickness of the obtained coating film was 80 to 100 nm, and this sample was used as Comparative Example 1.

[Comparative Example 2] Among coating agents obtained by mixing an acidic hydrolyzate of an ethyl silicate condensate with an inorganic strong acid peptized titanium oxide sol, ST is a typical example of a coating agent having a high surface hardness.
-K03 (manufactured by Ishihara Sangyo Co., Ltd.) was used. In film formation,
Except that ethanol was used as the diluting solvent, the solid content concentration was adjusted so as to have the same thickness as much as possible, and a coating film was formed using the same film forming method and firing conditions as in Example 2. In addition, the film thickness of the obtained coating film is 100 to 130 nm,
This sample was designated as Comparative Example 2.

First, properties of the coating films obtained in Examples 1 and 2 and Comparative Examples 1 and 2 with respect to the initial appearance, surface hardness and wear resistance were examined.

(Initial Appearance) In the evaluation of the initial appearance, visual observation and measurement of the haze ratio were performed. In the visual observation, the appearance of colorless and transparent was “no problem”, and the appearance of defects such as discoloration and film breakage was evaluated in two stages as “bad”. Also, the haze meter haze-G
uard PLUS (manufactured by BYK-Gardner) was used.

The appearances of Examples 1 and 2 were less affected by the firing temperature, the haze value was 0.2, and there was no particular problem in visual appearance, and the appearance was high in transparency. The appearance was almost the same even when compared with the comparative example.

(Surface Hardness) In the evaluation of surface hardness, JIS
The pencil hardness was measured using K5400. Note that a pencil scratch coating film hardness tester model P (manufactured by Toyo Seiki Seisaku-sho, Ltd.) was used for the measurement.

In the evaluation of the pencil hardness, Comparative Example 1 was 9H and Comparative Example 2 was 6H, whereas Example 2 under the same heat treatment conditions as the Comparative Example had a clearly superior pencil hardness of 9H or more. It was confirmed. Also, 200 times more than the comparative example.
It was also confirmed that the pencil hardness was 9H or more also in Example 1, which was fired under the heat treatment condition of 300 ° C., which is lower than 300 ° C.
It was confirmed that the coating film of the present invention had clearly excellent pencil hardness.

(Abrasion Resistance) In the evaluation of the abrasion resistance, the appearance of the sample before and after the Taber abrasion test was visually observed, and the haze ratio was measured. Specifically, using a wear device rotary abrasion tester 5130 ABRAZER (manufactured by Toyo Seiki Seisaku-Sho, Ltd.), a wear test was performed under the conditions of a wear wheel CS-17, a load of 250 g, and 100 revolutions, and the sample appearance before and after the test was visually observed. The observation and the change in haze ratio were measured by the haze meter. In the visual observation, evaluation was made in two stages of "small scratches" and "many scratches" according to the degree of scratches. In the haze ratio, a difference between the haze ratio before and after the test was represented as a haze change ΔH, which was used as an indicator of abrasion resistance.

In the evaluation of the taper wear, the ΔH value was +1.6 in Comparative Example 1 and +2.5 in Comparative Example 2, whereas
It was confirmed that Example 2 under the same sintering conditions had +0.5 and that Example 1 under the low sintering temperature had an excellent abrasion resistance of +1.1. Also, in the visual observation, the degree of scratching of Examples 1 and 2 was smaller than Comparative Examples 1 and 2. Also, from the results of the examples,
It was confirmed that the higher the firing temperature, the lower the ΔH value and the higher the abrasion resistance. It was confirmed that the coating film of the present invention had clearly excellent wear resistance.

From the above, it was found that the coating film obtained from the composition of the present invention had excellent surface hardness and abrasion resistance. Next, properties relating to hydrophilicity and photocatalytic activity were examined. In this evaluation, a comparison was made with Sample Comparative Example 1 which was a coating film having an excellent surface hardness of 9H with a pencil hardness of 9H.

(Hydrophilicity) In the evaluation of hydrophilicity, a black light blue lamp (hereinafter referred to as BLB) was irradiated to measure a water contact angle. In this evaluation, the ultraviolet light intensity was set to about the same level as outdoors, that is, 0.5 mW / cm 2. Then, the contact angle values with water 0 hours after irradiation and 24 hours after irradiation were measured. In addition, about the apparatus, the automatic contact angle meter CA-Z (made by Kyowa Interface Science Co., Ltd.) was used.

In the evaluation of hydrophilicity, the water contact angle in Example 1 at 0 hour of BLB irradiation was 43 °, and that of Example 2 was 2 °. In 2 it fell to 1 °. Since the hydrophilicity was exhibited by BLB irradiation, it was confirmed that the coating film had hydrophilicity due to photocatalytic activity. Further, since Example 1 having a lower firing temperature is more hydrophobic than Example 2 having a higher firing temperature (having a larger water contact angle), the higher the firing temperature, the more the surface treatment component carboxylic acid, which is also a hydrophilicity inhibiting component, becomes more hydrophilic. It was predicted that the hydrophilic performance would be improved by decreasing and disappearing. Further, in Comparative Example 1 and Example 2 under the same firing conditions, the water contact angle after 24 hours of BLB irradiation was 3
° and 1 °, it was confirmed that the hydrophilic performance was the same.

(Photocatalytic Activity) In evaluating the photocatalytic activity, a silver nitrate color test was performed. A 2% by weight aqueous solution of silver nitrate was applied to the surface of the sample previously irradiated with 1 mW / cm2 ultraviolet light for 24 hours, and then irradiated with 1.2 mW / cm2 ultraviolet light for 10 minutes.
* Was measured.

In the evaluation of the photocatalytic activity, ΔE * of Example 1 was used.
Was 8.3 and Example 2 was 8.4. Since a silver nitrate color reaction was shown by BLB irradiation, it was confirmed that the coating film had photocatalytic activity. Also, ΔE * of Comparative Example 1
Of 4.2, it was confirmed that the photocatalytic activity of the examples was about twice or more superior. It was confirmed that the coating film of the present invention had clearly excellent photocatalytic activity. In addition,
The effect of the firing temperature on the photocatalytic activity was hardly affected by the firing temperature shown in the examples.

Table 1 shows the results of the evaluation. Table 1 shows that the present invention is a photocatalytic coating film having extremely excellent hardness, abrasion resistance and good photocatalytic activity.

[0070]

[Table 1]

[Analysis of Titanium Oxide Sol] In order to investigate the cause of realizing excellent coating film hardness and abrasion resistance which cannot be obtained with the conventional photocatalytic composition, malic acid was used in an amount of 1 to 1: 1.
Titanium oxide sol M-6 (manufactured by Taki Chemical Co., Ltd.) containing 5% by weight and having a solid content of titanium oxide alone of 6% by weight was analyzed.

[Analysis of Absolute Amount of Malic Acid Adsorbed on Titanium Oxide Surface] An analysis was performed to confirm that malic acid was adsorbed on the titanium oxide surface. The liquid of the titanium oxide sol used this time contains malic acid of 1 to 1.5% by weight in total, and the state is malic acid which is adsorbed and fixed on the surface of titanium oxide particles (hereinafter, adsorbed malic acid). ), And malic acid dissolved in a solvent without being adsorbed and freely moving (hereinafter referred to as free malic acid). Therefore, the sol as it was for quantification of free malic acid and the sol which had been alkali-treated for quantification of adsorbed malic acid were respectively subjected to ultrafiltration and the filtrates collected were analyzed by capillary electrophoresis.

To quantitatively evaluate the free malic acid, the titanium oxide sol was diluted 100 times with ultrapure water, and separated under such conditions that the titanium oxide was not mixed into the filtrate and the adsorbed malic acid did not come off the titanium oxide surface. Ultrafiltration filter UFV2 BQK40 with molecular weight cutoff of 50,000 (Nippon Millipore Co., Ltd.)
Ultrafiltration), no titanium oxide particles are present,
A filtrate containing only free malic acid was obtained.

To quantitatively evaluate the amount of adsorbed malic acid, a sample obtained by diluting a titanium oxide sol 10-fold with a 0.1N aqueous sodium hydroxide solution was heated in a sealed glass bottle at 60 ° C. for 4 days, and further 10-fold with ultrapure water. It was diluted and subjected to ultrafiltration under the same filtration conditions as when a filtrate of free malic acid was obtained to obtain a filtrate containing both adsorbed malic acid and free malic acid off the surface of the titanium oxide particles.

The obtained filtrate was analyzed by capillary electrophoresis. Specifically, inner diameter 50 μm × length 104
cm capillary and organic acid analysis buffer (pH 5.
6, Agilent Technologies Co., Ltd.), migration voltage 25 kV (Negative), detection wavelength (Signal 350n)
m, reference 200 nm). As a result, the sol contained 0.7% by weight of adsorbed malic acid and 0.3% of free malic acid.
As a result, it was confirmed that malic acid was adsorbed on the surface of the titanium oxide particles.

[Analysis of Bonding Morphology of Malic Acid Adsorbed on Titanium Oxide Surface] In order to analyze the bonding morphology of malic acid adsorbed on the surface of titanium oxide sol, DL-malic acid, surface-treated titanium oxide sol, and surface-treated titanium oxide sol were added to DL-malic acid. -Spectrum 2000 FTIR (PERKIN EL)
(MER Co., Ltd.), and fast Fourier transform infrared absorption spectrum analysis was performed. As a result, in the surface-treated titanium oxide sol, a phenomenon was observed in which the absorption peak at 1720 cm -1 due to the double bond C = O of carbon and oxygen existing in the structure of DL-malic acid was shifted. Reference S. Doeuff et a
l., `` Hydrolysis of titanium alkoxides: modifica
tion of themolecular percursor by acetic aci
d "(p. 206-216, 89, 1987, Journal
According to Non-Crystalline Solids), one of the bonding forms of acetic acid and titanium alkoxide is a monodentate (Monodentate) type, which shifts the absorption peak at 1720 cm-1 derived from C = O existing in the structure of acetic acid. Although the results suggest that malic acid and the titanium oxide sol surface have a monodentate (Mono
dentate) type.

[Thermogravimetric / differential heat (hereinafter referred to as TG / DTA) simultaneous analysis of malic acid adhering to the surface of titanium oxide]
In order to grasp the TG / DTA characteristics of the malic acid adhering to the titanium oxide sol surface during the heat treatment, a TG / DTA simultaneous measuring device TG / DTA320 (Seiko Electronics Co., Ltd.)
Was used. As a result, about 1
A TG / DTA phenomenon accompanied by a weight loss of weight% and an exothermic phenomenon was confirmed. Since this phenomenon is similar to the phenomenon observed when heat treating organic titanium compound titanium acetylacetonate to obtain titanium oxide, the result of TG / DTA analysis of malic acid surface-treated titanium oxide sol at around 300 ° C. This suggests that malic acid adsorbed on the surface of titanium oxide is thermally decomposed and burned out. On the other hand, when the surface-modified inorganic strong acid peptized titanium dioxide sol STS-01 (manufactured by Ishihara Sangyo Co., Ltd.) was heated, an endothermic reaction was observed at around 350 ° C., but malic acid was adhered. And exothermic reaction. Also, edited by Masayuki Yamane, “Technical issues of the sol-gel method and their countermeasures”
9-10, 1990, published by ICP Co., Ltd.), the temperature change state of the tetraethoxysilane hydrolyzate was analyzed by the change in IR absorption of the hydroxyl group.
He points out that a phenomenon occurs in which the hydroxyl group bonded by hydrogen disappears in the vicinity. From this, it is considered that the endothermic reaction of STS-01 is an endothermic reaction when a non-flammable substance such as water hydrogen-bonded to the surface of titanium dioxide has disappeared.

[High Temperature X Regarding Crystallinity of Titanium Oxide Sol]
X-ray diffraction analysis (hereinafter referred to as high-temperature XRD analysis)] In order to examine the crystal state of the titanium oxide sol, an X-ray diffraction analyzer MXP-18 (manufactured by Mac Science Co., Ltd.) was used to increase the temperature every 100 ° C. Was subjected to high temperature XRD analysis. As a result, it was confirmed that although the crystallinity was low at room temperature, the crystallization rapidly progressed from a heating temperature of about 350 ° C. to 450 ° C., and that the crystallinity was higher at a higher temperature. The crystal structure is anatase type up to around 750 ° C.,
It was confirmed that the film became a rutile type up to 850 ° C. 500
It is considered that the crystallization phenomenon up to ° C. is linked to the TG / DTA phenomenon described above.

[0079]

According to the present invention, it is possible to provide a production method for forming a photocatalytic coating film having excellent hardness, abrasion resistance and good photocatalytic activity on a substrate surface by a wet method. It became. In addition, it has become possible to provide a photocatalytic member having a coating film obtained by forming the film and firing it.

──────────────────────────────────────────────────続 き Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B05D 3/02 B05D 3/02 Z C04B 41/87 C04B 41/87 A C09D 5/00 C09D 5/00 Z 183/02 183/02 183/04 183/04 (72) Inventor Yumiko Katsukawa 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka Prefecture Totoki Equipment Co., Ltd. (72) Mitsuhide Shimobukie Kitakyushu, Fukuoka Prefecture 2-1-1 Nakajima, Kokurakita-ku, Tokyo F-term (reference) 4D075 BB28Z BB93Z CA02 CA13 CA34 CA37 CA39 CA45 CB06 DA04 DA06 DB01 DB12 DB13 DB14 DB18 DB20 DB21 DB31 DB63 DC01 DC05 DC08 DC11 DC15 DC18 DC24 DC30 DC38 EB02 EB43 EB47 EB51 EB56 EC02 EC07 EC53 EC54 4G069 AA03 AA08 BA02A BA02B BA02C BA04A BA04B BA13A BA14A BA14B BA17 BA21C BA22C BA29A BA48A BE08C BE32C CA01 CA11 CD10 EA09 EA11 E B15Y ED02 ED03 ED10 FA03 FB15 FB23 FB24 FB30 FC02 FC04 FC07 FC08 FC09 4J038 DL021 DL031 DL111 HA216 KA06 NA00 NA01 NA11 NA27 PA19 PB01 PB02 PB05 PB06 PB07 PB08 PB11 PC03 PC04 PC08 PC10

Claims (9)

[Claims] (1) at least one of the carboxylic acids (A)
A photocatalytic film-forming composition comprising (B) crystalline titanium oxide, (C) a silicon-based binder, and (D) a solvent, which has been surface-modified with at least one kind of substance, is coated on the surface of the substrate. (E) A production method in which a photocatalytic coating film is formed on a substrate surface by firing at a temperature of 300 to 800 ° C. 2. The method for producing a photocatalytic coating film according to claim 1, wherein the material (B) is crystalline titanium oxide particles, and has an average particle size of 1 to 100 nm. 3. The crystalline titanium oxide (B) is used in an amount of 1 to 1000 parts by weight based on 1 part by weight of the carboxylic acid for modifying the surface of the crystalline titanium oxide. The method for producing a photocatalytic coating film according to claim 1. 4. The silicon-based binder (C) is added in an amount of 10 parts by weight in terms of silicon dioxide with respect to 100 parts by weight of the titanium dioxide (B) in terms of titanium dioxide.
The composition according to claim 1, wherein the content is from 400 to 400 parts by weight.
4. The method for producing a photocatalytic coating film according to 3. 5. The method according to claim 1, wherein the total solid content concentration of the crystalline titanium oxide (B) in terms of titanium dioxide and the silicon binder (C) in terms of silicon dioxide is 20% by weight or less. The method for producing a photocatalytic coating film according to any one of claims 1 to 4. 6. The (F) pH of the coating film forming composition is from 2 to 6.
The method for producing a photocatalytic coating film according to any one of claims 1 to 5, wherein 7. A photocatalytic member provided with a photocatalytic coating by the method for producing a photocatalytic coating according to any one of claims 1 to 6. 8. The photocatalytic member according to claim 7, wherein the coating film obtained by drying and curing has a surface hardness of 9H or more in pencil hardness. 9. The photocatalytic member according to claim 7, wherein the substrate is ceramic or glass.