JP2001323188A - Coating material for forming transparent photocatalytic dispersion film and metallic plate coated with transparent photocatlytic dispersion film - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a coating material capable of improving the stability of the coating material in which particles of a photocatalyst are suspended and suited in forming a transparent photocatalytic dispersion film, and a coated steel plate which retains excellent hydrophilicity over a long period of time. SOLUTION: The coating material is composed of a boehmite sol, crystalline photocatalyst particles or a precursor which comes to crystalline photocatalyst particles after heat treatment, and a mixed solvent of water and an organic solvent with a mass ratio of the crystalline photocatalyst particles after heat treatment to the boehmite and/or γ-alumina in the range of 10:90 to 60:40 and a mass ratio of the water in the mixed solvent to the organic solvent in the range of 90:10 to 40:60 after heat treatment. Based on the crystalline photocatalyst particles after heat treatment, 10-50 pts. mass silane coupling agent can be incorporated. As the silane coupling agent, an epoxy based or methacryloxy based silane coupling agent is used. As the organic solvent, one or more kinds selected from alcohols, ethers, and ketones are used and of them, at least one kind preferably has a boiling point higher than that of water.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint capable of forming a photocatalyst-dispersed coating film exhibiting excellent hydrophilicity from the beginning of film formation and having excellent storage stability, and a transparent photocatalyst-dispersed coating film formed from the paint. To a coated metal plate coated with:

[0002]

2. Description of the Related Art For fixing a photocatalyst, a method of fixing a photocatalyst by applying a coating containing the photocatalyst to a surface of a metal substrate or the like and baking and drying the same is adopted. Silica (PCT / JP96 / 00733), amorphous alumina (JP-A-9-227805), and the like. According to these methods, a coating film exhibiting excellent hydrophilicity with a contact angle to water of 10 degrees or less is obtained, and excellent hydrophilicity is maintained as long as the photocatalyst is excited by light irradiation. Further, when photocatalyst particles having a very small particle diameter are bound by a transparent binder, a transparent photocatalyst thin film having a high visible light transmittance is formed.

[0003] However, a photocatalyst-dispersed coating film using silica as a binder does not exhibit hydrophilicity at the beginning of film formation, but becomes hydrophilic only by light irradiation. In addition, Si in the silica binder
For the -O bond, the bond energy (101.5 kcal / mol) is changed to the bond energy (136 kcal) of the Al-O bond.
/ Mol), the Si—O bond is easily broken when the photocatalyst is used for a long time in an excited state. Breakage of the Si—O bond causes cracks in the coating film, whitening of the coating film, peeling of the coating film, reduction in transparency, and the like. Even when amorphous alumina is used for the binder, it does not become hydrophilic without light irradiation similarly to silica, and has a low water storage capacity as compared with silica, so that good hydrophilicity cannot be maintained for a long period of time. Further, in the case of amorphous alumina, when used for a long period of time, partial crystallization or the like occurs from the amorphous state, so that the coating film is whitened and the transparency tends to decrease.

On the other hand, the present inventors have proposed a transparent photocatalyst-dispersed coating film using boehmite and / or γ-alumina as a binder in Japanese Patent Application No. 11-246873. Since crystalline boehmite is used as a raw material, almost no organic components are contained in the coating film, and boehmite and / or γ-alumina having a hydrophilic OH group serve as a binder. A photocatalyst-dispersed coating film having a degree of hydrophilicity of less than or equal to or less than one degree, good hydrophilicity persistence, and excellent adhesion and weather resistance is formed.

[0005]

However, in a coating material in which water is used as a solvent and boehmite sol and crystalline photocatalyst particles or precursors of the photocatalyst particles are dispersed, it is easy to agglomerate or gel during storage and storage stability is poor. . Also during baking, if heated rapidly, the coating film becomes milky and the adhesion tends to decrease. Therefore, it is necessary to form a transparent photocatalyst-dispersed coating film with good coating adhesion by baking at a temperature of 200 ° C. or more for a long time of 20 minutes or more. A photocatalyst-dispersed coating film having transparency and weather resistance could not be formed.

[0006] The present invention has been devised to solve such a problem. By using a mixed solvent of water and an organic solvent as a solvent, the present invention has excellent storage stability, high hydrophilicity and high transparency, A transparent photocatalyst-dispersed coating film forming coating that can form a photocatalyst-dispersed coating film with excellent coating adhesion and weather resistance, and a coated metal plate coated with a transparent photocatalyst-dispersed coating film that maintains good hydrophilicity over a long period of time. The purpose is to provide.

[0007]

In order to achieve the object, a coating material for forming a transparent photocatalyst-dispersed coating film of the present invention comprises a boehmite sol, a crystalline photocatalyst particle, or a precursor and a water-soluble precursor. The crystalline photocatalyst particles and the boehmite sol are mixed so that the mass ratio of the crystalline photocatalyst particles to the boehmite and / or γ-alumina after the heat treatment is in the range of 10:90 to 60:40. The mass ratio of water and organic solvent of the mixed solvent is 90:
It is characterized by being adjusted in the range of 10:40:60.

[0008] The transparent photocatalyst-dispersed coating film forming coating composition may contain 10 to 50 parts by mass of a silane coupling agent with respect to the crystalline photocatalyst particles after the heat treatment. As the silane coupling agent, an epoxy-based or methacryloxy-based silane coupling agent is used. As organic solvents,
One or more selected from alcohols, ethers, and ketones are used, and at least one of them preferably has a higher boiling point than water.

Further, the coated metal plate coated with the transparent photocatalyst-dispersed coating film has a coating having a composition in which the weight ratio of the crystalline photocatalyst particles to boehmite and / or γ-alumina is 10:90 to 40:60. It is formed on the plate surface. In a coating film formed from a paint containing a silane coupling agent in the paint, crystalline photocatalyst particles: 10 to 60% by mass, silica derived from the silane coupling agent: 0.1 to 10% by mass, organic matter derived from the silane coupling agent Functional group: 5% by mass or less, with the balance being boehmite and / or γ-alumina.

[0010]

A coating composition in which boehmite sol and crystalline photocatalyst particles or a precursor of crystalline photocatalyst particles are dispersed in water has poor storage stability, and the coating film becomes milky by rapid heating during baking, resulting in reduced adhesion. The inventors have attributed these drawbacks to solvent balance. That is, the boehmite sol and the crystalline photocatalyst particles or the precursors of the crystalline photocatalyst particles, which are the solid components (solid components after the formation of the coating film) in the coating material, have good water dispersibility by themselves, but differ when mixed and dispersed. Partial dehydration-condensation and aggregation easily occur between the components, and the dispersibility in an aqueous solvent is lowered, and the storage stability is lowered.

Thus, it has been found that when a mixed solvent of water and a water-soluble organic solvent is used to disperse the boehmite sol and the crystalline photocatalyst particles or the precursor of the crystalline photocatalyst particles, the storage stability of the paint is improved. . This is considered to be because the boehmite sol, the crystalline photocatalyst particles, or the precursor of the crystalline photocatalyst particles were partially solvated in an organic solvent, thereby enabling stable dispersion in the paint. The effect of the blending of the organic solvent on the storage stability becomes significant at a solvent composition ratio of 10% by mass or more. However, a solvent containing an excess amount of an organic solvent exceeding 60% by mass completely solvates the solid components in the coating material and increases the hydrophobicity, so that it tends to agglomerate or gel.

A mixed solvent of water and an organic solvent is effective in preventing the coating film from being milky during firing. It is considered that the reason why the mixed solvent is effective in suppressing the opacification is that a plurality of solvents having different boiling points volatilize at the respective boiling points. Above all, when an organic solvent having a boiling point higher than that of water is blended as at least one component, even when rapidly heated to a higher temperature, the coating film does not cause opacification or decrease in adhesion, and is more suitable for high-temperature and short-time firing. It will be advantageous. On the other hand, when water alone is used as the solvent, the solvent volatilizes at a stretch at the boiling point of water of 100 ° C., and the coating film becomes brittle and porous, so that opacification proceeds.

A photocatalyst-dispersed coating film composed of crystalline photocatalyst particles and boehmite and / or γ-alumina has excellent weather resistance and exhibits excellent hydrophilicity from the beginning even without irradiation with ultraviolet rays. However, usually, long-time firing is required to obtain sufficient coating film adhesion and weather resistance. In this regard, in the present invention, a crosslinking / curing reaction is performed by adding a silane coupling agent as necessary under conditions that suppress a decrease in hydrophilicity and weather resistance due to introduction of an organic component into a coating film. And the formation of a transparent photocatalyst-dispersed coating film having the required strength in a short time firing.

[0014]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a mixed solvent of water and an organic solvent, crystalline photocatalyst particles or heat treatment are performed so that the mass ratio of crystalline photocatalyst particles after heat treatment to boehmite and / or γ-alumina is 10:90 to 60:40. A boehmite sol in which a precursor that later becomes crystalline photocatalyst particles is dispersed is blended. Boehmite and / or γ-alumina having a hydrophilic OH group show excellent hydrophilicity from the beginning of film formation and produce a coating film having good hydrophilicity persistence. Boehmite and / or γ-alumina crystals having an Al—O bond having a large binding energy are formed of Al
Since it has a strong resistance to breaking of the -O bond and, unlike amorphous alumina, it is already in a crystalline state, no crystallization reaction occurs. Therefore, the occurrence of cracks in the coating film and the whitening of the coating film are suppressed.

The crystalline photocatalyst particles themselves exhibit excellent hydrophilicity when excited by light irradiation, and decompose organic stains on the surface of the coating film, so that the deterioration of hydrophilicity over time due to the adhesion of stains is suppressed. , Maintain excellent hydrophilicity over a long period of time. Examples of the crystalline photocatalyst particles include titanium oxide, zinc oxide, strontium titanate, tungsten oxide, tin oxide, and zirconium oxide. Titanium oxide having high chemical stability and photocatalytic activity is preferable. The crystalline photocatalyst particles exhibit a remarkable photocatalytic action when excited by light irradiation at a blending amount of 10 parts by mass or more, and recover the hydrophilicity reduced by organic contamination in a short time. However, when an excessive amount of the crystalline photocatalyst particles exceeding 60 parts by mass is blended, the hydrophilicity tends to be reduced in a short time in a dark place without light irradiation.

As a raw material of the crystalline photocatalyst particles, a precursor which becomes crystalline photocatalyst particles after heat treatment can be used. Examples of such a precursor include metal hydroxides obtained by hydrolyzing various metal alkoxides and metal salts. For example, when using titanium oxide as crystalline photocatalyst particles, titanium tetraisopropoxide, titanium hydroxide, or the like is added to the boehmite sol. Titanium tetraisopropoxide and titanium hydroxide become anatase-type crystals exhibiting excellent photocatalytic activity when a paint applied to the surface of a metal plate is heat-treated at 400 to 600 ° C.

When a silane coupling agent is added to the coating, the crosslinking / curing reaction of the coating film is accelerated, and the firing time is shortened. However, the addition of the silane coupling agent means that an organic component is introduced into the coating film, the hydrophilicity is not exhibited at the time of film formation, and the organic component in the coating film is decomposed by a photocatalytic reaction and has a weather resistance. May decrease. Therefore, when the silane coupling agent is added and baking is performed for a short time, the addition amount is set so as to be 10 to 50 parts by mass with respect to the crystalline photocatalyst particles after the heat treatment. When the silane coupling agent is added in an amount of 10 parts by mass or more, the effect of accelerating the crosslinking / curing reaction to photocatalyst particles having a small particle size and a large specific surface area and to boehmite and / or γ-alumina becomes remarkable, and the A coating film having sufficient adhesion and weather resistance is formed by baking for a short time. However, when an excess amount of the silane coupling agent exceeding 50 parts by mass is added, the organic component contained in the formed coating film increases, the initial hydrophilicity decreases, and the number of Si—O bonds increases. The weather resistance also decreases.

The silane coupling agent has both an OH group by hydrolysis and a polymerizable organic functional group. The type of the polymerizable organic functional group is not particularly limited as long as it does not exert an adverse effect such as agglomeration or gelling at the time of preparing the coating material, but in order to improve the coating film adhesion, a 3-glycidoxypropyl group or the like is used. Methacryloxy groups such as an epoxy group and a 3-methacryloxypropyl group are preferred. Specifically, 3-
Examples include glycidoxypropyltrimethoxysilane, 3-glycidoxypropylmethyldimethoxysilane, 3-methacryloxypropyltrimethoxysilane, and 3-methacryloxypropylmethyldimethoxysilane.

The coating material for forming a transparent photocatalyst-dispersed coating film according to the present invention is specifically prepared as follows. Boehmite having a primary particle diameter of 20 nm or less is dispersed in a solvent such as water or water / alcohol to form a boehmite sol, and a suspension is prepared by dispersing crystalline photocatalyst particles having a primary particle diameter of 10 nm or less in the boehmite sol. Furthermore, in the case of a paint that can be used even after baking for a short time, a silane coupling agent that promotes crosslinking and effect reaction of the coating film is added to the suspension. The silane coupling agent may be added in advance to a solvent such as water or water / alcohol, or may be added to the boehmite sol before adding the crystalline photocatalyst particles.

As the original coating plate, various types of plated steel plates, stainless steel plates, aluminum plates and the like are used. The coating original plate is subjected to a pretreatment such as degreasing, phosphate treatment, and chromate treatment as necessary to improve the adhesion of the coating film. Prior to the formation of the transparent photocatalyst-dispersed coating film, a clear coating film may be formed as a first layer on the surface of the metal plate. Since the clear coating film has OH groups on its surface, it is chemically bonded to the transparent photocatalyst-dispersed coating film provided thereon to improve the adhesion of the transparent photocatalyst-dispersed coating film. Further, as a clear coating film, a transparent oxide coating film having a low refractive index is preferably provided with a film thickness of 1 μm or more in order to suppress the occurrence of interference colors. The transparent oxide coating film is formed, for example, by applying an oxide such as alumina, silica, zeolite or the like or a sol-like paint using a precursor which becomes an oxide after heat treatment as a raw material to a metal plate and subjecting to heat treatment. At this time, the OH groups contained in the sol of the paint component undergo a dehydration-condensation reaction with the OH groups on the pretreated metal plate surface to form a clear coating film firmly bonded to the metal plate surface.

When a coating film is formed using a coating material for forming a transparent photocatalyst-dispersed coating film containing no silane coupling agent, the coating material is applied and then heat-treated at 200 to 600 ° C. for 20 minutes or more. By this heat treatment, a crosslinking / curing reaction of the coating film proceeds, and a coating film having a necessary strength is formed. However, 600
At a heat treatment temperature exceeding ℃, the morphology of alumina changes and the number of OH groups on the surface decreases, so that the hydrophilicity of the coating film tends to decrease. A coating with the required strength can be formed by heat treatment within 5 minutes with a paint containing a silane coupling agent, but the heat treatment temperature and time should be set so that the organic functional groups that easily remain in the coating are reduced. is necessary.

The coating composition adjusted to a predetermined composition is obtained by baking: 10-60% by mass of crystalline photocatalyst particles; 0.1-10% by mass of silica derived from a silane coupling agent; organic functional groups derived from a silane coupling agent. : 5% by mass or less, the remainder being a coating film having a composition of boehmite and / or γ-alumina.
Since the amount of the organic functional group derived from the silane coupling agent is regulated to 5% by mass or less, good initial hydrophilicity is exhibited, and a coating film having excellent weather resistance is formed. Further, since the silica derived from the silane coupling agent is adjusted to the range of 0.1 to 10% by mass, the added silane coupling agent is sufficiently used for the crosslinking / curing reaction of the coating film and the Si—O A decrease in weather resistance due to an increase in bonding is also suppressed.

[0023]

Example 1 Film forming example 1 (Example of the present invention) A bright annealed material of SUS304 stainless steel having a thickness of 0.8 mm was used for a coating original plate, alkali-degreased, washed with water and dried. The paint was prepared by dispersing boehmite in a mixed solvent of water and butyl cellosolve (water: butyl cellosolve = 70: 30) to form a boehmite sol, and further having a particle size of 7 n.
m of anatase-type titanium oxide particles. Apply paint to stainless steel plate, 300 ℃
A transparent photocatalyst-dispersed coating film was formed by heating and baking for 30 minutes.

Film Forming Example 2 (Example of the Present Invention) An epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane) was added to the paint of Film Forming Example 1 at a ratio of 30 parts by mass to titanium oxide. Paint was used. This paint is applied to a stainless steel plate, and 300 ° C x 5
A transparent photocatalyst-dispersed coating film was formed by heating and baking for minutes. Film forming example 3 (Example of the present invention) Instead of anatase-type titanium oxide, a titanium oxide precursor obtained by dissolving titanium tetraisopropoxide in isopropanol and adding diisopropanolamine was used. Then, a coating material was prepared in the same manner as in Film Forming Example 2, and was heated at 450 ° C.
A transparent photocatalyst-dispersed coating film was formed by heating and baking for 5 minutes.

Film Forming Example 4 (Comparative Example) The mass ratio of water to butyl cellosolve was 95: 5 and 30:
A coating film was formed in the same manner as in Film-forming example 1 except that the mixed solvent set at 70 was used. Film-forming Example 5 (Comparative Example) A coating film was formed in the same manner as in Film-forming Example 2 except that a coating material to which an epoxy-based silane coupling agent was added in a ratio of 5 parts by mass and 70 parts by mass to titanium oxide was used. Was formed. Film forming example 6 (comparative example) Amino-based silane coupling agent (N- (2-aminoethyl)
A coating film was formed in the same manner as in Film Forming Example 2, except that a coating material to which 3-aminopropyltrimethoxysilane was added was used.

The storage stability of the paint prepared in each film forming example and the physical properties of the coated steel sheet were examined by the following methods. Storage stability of paint The prepared paint was stored for one month in an atmosphere at normal temperature, and then the dispersion state of the paint was observed, and the presence or absence of aggregation or gelation and the change in viscosity were investigated. Initial hydrophilicity of the coated steel sheet Water droplets are dropped on the coating film immediately after film formation and before irradiation with ultraviolet light.
Among the angles between the tangent drawn to the water droplet at the three-phase contact point of the water droplet and the air and the coating film surface, the angle on the side containing the water droplet is measured as the contact angle with respect to water, and the initial hydrophilicity is determined by the measured value. evaluated.

Persistence of hydrophilicity Using a mercury lamp having an ultraviolet intensity of 17 mW / cm ² at a wavelength of 365 nm, one test piece cut from each coated steel sheet was used.
After irradiating for hours, the coating film was hydrophilized, and then the test specimen was stored in a dark place without light irradiation. After one day, the contact angle with water was measured. Those that did not change from the initial hydrophilicity were evaluated as having good durability, and those that showed a value lower than the initial hydrophilicity were evaluated as x, indicating that the hydrophilicity was maintained. evaluated.

Adhesion of Coating Film [0028] A 1 mm-width × 10 × 10 square with a cutter was placed on the coating surface of a test piece cut out from each coated steel plate, and the coating film was subjected to a peeling test using an adhesive tape. Investigate the peeling condition of
When no peeling of the coating film was detected, it was evaluated as ○, and when the peeling of the coating film was evaluated as ×, the coating film adhesion was evaluated. After the gauze was pressed strongly against the coating surface of each test piece and reciprocated 10 times,
The coating surface was observed. The abrasion resistance was evaluated as "O" when no change was observed in the coating film, and as "X" when the coating film was peeled off due to opacification or powdering.

The test piece was subjected to a sunshine weather test at 63 ° C.
The state of the coating film after lapse of 000 hours was observed. The samples which maintained the initial transparency without any abnormality detected in the coating film were evaluated as ○, and those in which cracks and whitening were observed were evaluated as ×, and the weather resistance was evaluated.

As can be seen from the examination results in Table 1, the paints of Test Nos. 1 to 12 according to the present invention all had excellent storage stability. Further, as shown in Table 2, each of the coated steel sheets obtained by using each paint exhibits excellent initial hydrophilicity with a contact angle with water of 10 degrees or less, persistence of hydrophilicity, and adhesion of coating film. Also, the weather resistance was good.

On the other hand, in Test No. 13, in which the mass ratio of water to butyl cellosolve in the solvent was 95: 5, agglomeration occurred during the preparation of the paint. Test number 14 with a mass ratio of 30:70
In this case, the viscosity increased at the time of preparation of the paint, and the gel was formed one month later. In Test No. 15 in which the addition amount of the epoxy-based silane coupling agent was 5 parts by mass of titanium oxide, the coating film adhesion was poor. In Test No. 16 in which the addition amount was 70 parts by mass, no hydrophilicity was exhibited without ultraviolet irradiation, and the weather resistance was poor. In Test No. 17 using an amino-based silane coupling agent, gelation occurred at the time of coating preparation. As is clear from this comparison, by using a mixed solvent in which the weight ratio of water: organic solvent was maintained in the range of 10:90 to 60:40, a coating having excellent storage stability was obtained. It can be seen that the coated steel sheet obtained by using the composition is also excellent in hydrophilicity, coating film adhesion, weather resistance and the like.

[0032]

[0033]

[0034]

Example 2 Film forming method 1 (Example of the present invention) A bright annealed material of SUS304 stainless steel having a thickness of 0.8 mm was used as a coating original plate, subjected to alkaline degreasing, washed with water, and dried. The paint was prepared by dispersing boehmite in a mixed solvent of water and butyl cellosolve (water: butyl cellosolve = 70: 30) to form a boehmite sol, and further having a particle size of 7 n.
m of the anatase-type titanium oxide particles were dispersed and adjusted by adding 30 parts by mass of an epoxy silane coupling agent (3-glycidoxypropyltrimethoxysilane) to titanium oxide. The coating material was applied to a stainless steel plate, and heated and baked at 300 ° C. for 5 minutes to form a transparent photocatalyst-dispersed coating film.

Film forming method 2 (Example of the present invention) A silica coating was applied to the same stainless steel plate as in Film forming example 1 and heated at 220 ° C for 5 minutes to form a clear coating film (first film).
After forming the layer, a transparent photocatalyst-dispersed coating film was formed under the same conditions. Film forming example 3 (Example of the present invention) Instead of anatase type titanium oxide particles, a titanium oxide precursor obtained by dissolving titanium tetraisopropoxide in isopropanol and adding diisopropanolamine was used. Then, a coating material prepared under the same conditions as in Film Forming Example 1 was applied to a stainless steel plate, and baked at 450 ° C. for 5 minutes to form a transparent photocatalyst-dispersed coating film.

Film Forming Example 4 (Comparative Example) A coating film was formed in the same manner as in Film Forming Example 1 except that no silane coupling agent was added. Film-forming Example 5 (Comparative Example) A coating film was formed in the same manner as in Film-forming Example 1 except that it was baked at 180 ° C. Film-forming Example 6 (Comparative Example) Instead of the boehmite sol of Film-forming Example 1, a silica sol in which tetraethoxysilane was dissolved in ethanol or an alumina sol in which aluminum isopropoxide was dissolved in ethanol was used, and oxidized with silica or amorphous alumina. A transparent photocatalyst-dispersed coating film made of titanium was formed.

Each of the obtained coated steel sheets had the composition shown in Table 3. Table 4 shows the results of evaluating the physical properties in the same manner as in Example 1. As can be seen from the survey results in Table 4, the transparent photocatalyst-dispersed coating films of Test Nos. 1 to 6 according to the present invention were:
Both show excellent initial hydrophilicity with a water contact angle of 10 or less,
The hydrophilicity persistence, coating film adhesion and light resistance were also good.

On the other hand, in Test No. 7 using a coating material to which no silane coupling agent was added, the adhesion of the coating film was poor. In Test No. 8 in which the firing temperature was low, the adhesion of the coating film was similarly poor, and the coating film after the sunshine weather test had cracks and whitening due to the large amount of organic functional groups remaining in the coating film. In Test No. 9 using silica as a binder, no hydrophilicity was exhibited without ultraviolet irradiation, and the weather resistance was poor. In Test No. 10 using amorphous alumina as a binder, no hydrophilicity was exhibited without irradiation with ultraviolet light, the hydrophilicity after storage in a dark place was reduced, and the weather resistance was poor.

As is apparent from this comparison, the use of a coating material to which an appropriate amount of a silane coupling agent has been added allows a transparent photocatalyst-dispersed coating film having sufficient hydrophilicity and coating film strength to be formed by baking for a short time. Was confirmed.

[0040]

[0041]

[0042]

As described above, the coating composition for forming a transparent photocatalyst-dispersed coating film of the present invention has improved storage stability by using a mixed solvent of water and an organic solvent.
It prevents whitening of the coating film during heat treatment. Therefore, a coated steel sheet having a transparent and transparent photocatalyst-dispersed coating film having excellent hydrophilicity maintained over a long period of time, high transparency, and excellent adhesion and weather resistance is produced.

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁷ Identification symbol FI Theme coat ゛ (Reference) B32B 9/00 B32B 9/00 A 15/04 15/04 Z (72) Inventor Kenji Sakado Ichikawa, Chiba No.7-1 Takatani Shinmachi F-term in Nisshin Steel R & D Co., Ltd. JK06 JL08A JL09 JM01A JN01 JN01A JN30A YY00A 4G069 AA03 AA08 AA09 BA01A BA04A BA04B BA18 BA22A BA22B BA48A BC16A BC16B BC50A BC50B CD10 DA03 EA07 FA03 FB23 FB30 4A0326A12 MA12 NA01 NA03 NA06 NA12 NA26 PA19 PC02

Claims (5)

[Claims] The present invention comprises a boehmite sol, crystalline photocatalyst particles, or a precursor that becomes crystalline photocatalyst particles after heat treatment, and a mixed solvent of water and an organic solvent. The mass ratio is 10:
The crystalline photocatalyst particles and the boehmite sol are blended so as to be in the range of 90 to 60:40, and the mass ratio of water and the organic solvent of the mixed solvent is adjusted to be in the range of 90:10 to 40:60. Characteristic paint for forming a transparent photocatalyst-dispersed coating film. 2. The amount of crystalline photocatalyst particles after heat treatment is 1
The coating material for forming a transparent photocatalyst-dispersed coating film according to claim 1, comprising 0 to 50 parts by mass of an epoxy-based or methacryloxy-based silane coupling agent. 3. An organic solvent comprising alcohols, ethers,
The coating for forming a transparent photocatalyst-dispersed coating film according to claim 1, wherein at least one selected from ketones has at least one boiling point higher than that of water. 4. A transparent photocatalyst, wherein a coating film having a composition in which the mass ratio of crystalline photocatalyst particles to boehmite and / or γ-alumina is 10:90 to 40:60 is formed on the surface of a metal plate. A coated metal plate on which a dispersed coating film has been formed. 5. Crystalline photocatalyst particles: 10 to 60% by mass,
Silica derived from silane coupling agent: 0.1 to 10% by mass, organic functional group derived from silane coupling agent: 5% by mass
A coated metal plate having a transparent photocatalyst-dispersed coating film, wherein a coating film having a composition of boehmite and / or γ-alumina is formed on the surface of the metal plate.