JP2024003020A - Covering material and inactivation method for germ or virus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a covering material that can increase the amount of light reaching a photocatalyst and can efficiently develop photocatalysis.

SOLUTION: A covering material 1 includes: a base material 2, the surface of which is at least partially composed of a covering layer 21 having a reflectance of light of 85% or more at a wavelength of 555 nm; and a photocatalyst layer 3 located on the covering layer 21.

SELECTED DRAWING: Figure 1

COPYRIGHT: (C)2024,JPO&INPIT

Description

The present disclosure generally relates to a coating material and a method of inactivating bacteria or viruses, and specifically relates to a coating material including a photocatalyst layer and a method of inactivating bacteria or viruses using the coating material.

The photocatalyst has photocatalytic effects such as hydrophilicity, antifouling effect, and inactivation of bacteria or viruses. Among these photocatalytic effects, the inactivation effect of bacteria or viruses is attracting attention. Furthermore, a coating film containing a photocatalyst is provided on a colored base material to impart photocatalytic action to the base material. For example, the photocatalytic colored coated article of Patent Document 1 includes a base material, a colored coating film, and a photocatalytic coating film.

Japanese Patent Application Publication No. 2001-149855

Since the photocatalytic effect is expressed by the photoexcitation effect generated by irradiating the photocatalyst with light, the photocatalytic effect can be efficiently expressed by increasing the amount of light that reaches the photocatalyst. Therefore, by increasing the amount of light that reaches the photocatalyst, the photocatalyst can easily inactivate bacteria or viruses.

An object of the present disclosure is to provide a coating material that can increase the amount of light that reaches a photocatalyst and efficiently exhibit photocatalytic action, and a method for inactivating bacteria or viruses using this coating material. It's about doing.

The coating material of the present disclosure includes a base material in which at least a portion of the surface is constituted by a coating layer having a reflectance of 85% or more for light at a wavelength of 555 nm, and a photocatalyst layer located on the coating layer. include.

In the method for inactivating bacteria or viruses of the present disclosure, the photocatalyst layer of the coating material is irradiated with light to activate the photocatalyst and inactivate the bacteria or viruses.

According to the coating material of the present disclosure, light can efficiently reach the photocatalyst and the photocatalytic action can be efficiently exhibited, and if the coating material of the present disclosure is used, bacteria or viruses cannot be inactivated. can.

FIG. 1 is a schematic cross-sectional view showing a covering material according to a first embodiment. FIG. 2 is a schematic explanatory diagram showing the case where the coating material shown in FIG. 1 is irradiated with light. FIG. 3 is a schematic cross-sectional view showing a covering material according to a second embodiment. FIG. 4 is a schematic explanatory diagram showing a case where the covering material shown in FIG. 3 is irradiated with light. FIG. 5 is a graph showing the percentage of color difference ΔE versus elapsed time.

1. Overview A coating material 1 according to an embodiment of the present disclosure includes a base material 2 and a photocatalyst layer 3, as shown in FIG. At least a portion of the surface of the base material 2 is composed of a coating layer 21 having a reflectance of 85% or more for light having a wavelength of 555 nm. Photocatalyst layer 3 is located on coating layer 21 .

In the coating material 1 of this embodiment, since the coating layer 21 has a reflectance of 85% or more for light with a wavelength of 555 nm, the coating layer 21 easily reflects light. Since the photocatalyst 30 included in the photocatalyst layer 3 exhibits photocatalytic action by visible light, not only the light that directly hits the photocatalyst layer 3 but also the light that has passed through the photocatalyst layer 3 and is reflected by the coating layer 21 is activated by the photocatalyst. It is possible to reach 30. Therefore, light can efficiently reach the photocatalyst 30, and the photocatalytic action can be efficiently exerted.

In the following explanation, "reflectance" refers to the gloss of the reference surface by measuring the reflectance of light according to the 60 degree specular gloss measurement method described in JIS K 5600-4-7 (1999). It is defined as a percentage when the degree is 100. The upper limit of specular gloss is 100%.

2. Details of covering material 2-1. First embodiment 2-1-1. Structure of Covering Material Hereinafter, details of the structure of the covering material 1 according to the first embodiment will be described. The coating material 1 according to the first embodiment includes a base material 2 and a photocatalyst layer 3, and further includes an intermediate protective layer 4 provided between the base material 2 and the photocatalyst layer 3. For this reason, in the coating material 1, the intermediate protective layer 4 and the photocatalyst layer 3 are laminated in this order on the base material 2.

(1) Base material At least a portion of the surface of the base material 2 is comprised of the coating layer 21. That is, the entire surface of the base material 2 may be composed of the coating layer 21, or a part of the surface of the base material 2 may be composed of the coating layer 21. In this embodiment, the entire surface of the base material 2 is comprised of the coating layer 21. The base material 2 includes a base material 20 , a coating layer 21 , and an undercoat layer 23 provided between the base material 20 and the coating layer 21 .

(i) Base material The material of the base material 20 is not particularly limited. The base material 20 may be made of one or more materials selected from the group consisting of metals, ceramic materials such as ceramic materials, hydraulic materials such as cement, resin molding materials such as plastics, and carbon materials. When the base material 20 is a metal plate, examples of the metal plate include a steel plate, a stainless steel plate, an aluminum plate, a zinc plate, a copper plate, and an alloy plate thereof.

The base material 20 of this embodiment is a plated steel plate 22. That is, the base material 2 includes a plated steel plate 22 and a coating layer 21 provided on the plated steel plate 22.

Examples of the galvanized steel sheet 22 include hot-dip galvanized steel sheet, electrogalvanized steel sheet, alloyed hot-dip galvanized steel sheet, aluminized steel sheet, aluminum-zinc alloy plated steel sheet, zinc-aluminum-magnesium alloy plated steel sheet, and zinc-aluminum-magnesium alloy plated steel sheet. -Includes various types of plated steel sheets such as silicon alloy plated steel sheets, zinc-magnesium alloy plated steel sheets, tin plated steel sheets, lead plated steel sheets, and chrome plated steel sheets.

The surface of the plated steel plate 22 may be chemically treated. Examples of chemical conversion treatments include coating chromate treatment, electrolytic chromate treatment, zinc phosphate treatment, and non-chromate treatment that does not contain hexavalent chromium, which has been developed in recent years.

(ii) Undercoat layer 23
The undercoat layer 23 is provided on the base material 20. The undercoat layer 23 covers the base material 20. Therefore, the undercoat layer 23 is in direct contact with the base material 20. In this embodiment, since the base material 20 is the plated steel plate 22, the undercoat layer 23 is in direct contact with the plated steel plate 22. The undercoat layer 23 may be a single layer or may be composed of multiple layers. Further, the present invention is not limited to the case where the base material 20 and the undercoat layer 23 are in direct contact with each other; for example, an appropriate layer may be interposed between the base material 20 and the undercoat layer 23. The undercoat layer 23 can be formed from an undercoat paint.

The thickness of the undercoat layer 23 is preferably 5 μm or more and 30 μm or less. When the thickness of the undercoat layer 23 is 5 μm or more, the workability of the undercoat layer 23, the adhesion to the base material 20, and the reflectivity of the coating layer 21 can be improved. By setting the film thickness of the undercoat layer 23 to 30 μm or less, it is possible to suppress the occurrence of wrinkles (small bubble-like bulges and holes) during application of the undercoat paint. The thickness of the undercoat layer 23 is more preferably 10 μm or more and 25 μm or less, particularly preferably 12 μm or more and 22 μm or less. If the undercoat cannot be applied at once due to the occurrence of wrinkles, etc., it may be applied in two or more times.

The base coat can contain, for example, a polyester resin, a curing agent, and a white pigment. The undercoat may contain pigment components such as extender pigments, coloring pigments, and chromate-based or chromate-free rust-preventing pigments, curing catalysts, pigment dispersants, surface conditioners, matting agents, organic solvents, etc., as necessary. Known materials may be contained within a range that does not impair the reflectance of light at 555 nm of 85% or more.

The number average molecular weight of the polyester resin contained in the undercoat is preferably 2,000 or more and 30,000 or less, more preferably 3,000 or more and 25,000 or less, from the viewpoint of coating film finish, coating hardness, and processability. It is more preferably 19,000 or more and 26,000 or less, even more preferably 20,000 or more and 23,000 or less. Note that the number average molecular weight in this specification is a value obtained by converting the number average molecular weight measured using gel permeation chromatography (GPC) based on the molecular weight of standard polystyrene. Specifically, "HLC8120GPC" (trade name, manufactured by Tosoh Corporation) was used as a gel permeation chromatograph, and "TSKgel G-4000HXL", "TSKgel G-3000HXL", "TSKgel G-2500HXL" and "TSKgel G-2500HXL" were used as columns. The measurement can be performed using four units of "TSKgel G-2000HXL" (trade name, all manufactured by Tosoh Corporation) under the conditions of a mobile phase of tetrahydrofuran, a measurement temperature of 40° C., a flow rate of 1 mL/min, and a detector RI.

It is preferable that the polyester resin contained in the undercoating paint has a hydroxyl group. The hydroxyl value of the polyester resin is preferably in the range of 10 to 200 mgKOH/g, particularly 60 to 185 mgKOH/g, from the viewpoint of adhesion of the resulting coating film. The acid value of the polyester resin is desirably 30 mgKOH/g or less, preferably within the range of 1 to 20 mgKOH/g, from the viewpoint of finishing properties.

The polyester resin contained in the undercoat can usually be produced by an esterification reaction or transesterification reaction with a polybasic acid component and a polyhydric alcohol component. As the polybasic acid component, for example, an alicyclic polybasic acid component, an aliphatic polybasic acid component, an aromatic polybasic acid component, etc. can be used.

The alicyclic polybasic acid component is generally a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two or more carboxyl groups in one molecule, and acid anhydrides of the compounds. and an esterified product of the compound. Examples of the alicyclic polybasic acid component include 1,2-cyclohexanedicarboxylic acid, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, 4-cyclohexene-1,2-dicarboxylic acid, and 3-cyclohexanedicarboxylic acid. Alicyclic polycarboxylic acids such as methyl-1,2-cyclohexanedicarboxylic acid, 4-methyl-1,2-cyclohexanedicarboxylic acid, 1,2,4-cyclohexanetricarboxylic acid, and 1,3,5-cyclohexanetricarboxylic acid ; anhydrides of these alicyclic polycarboxylic acids; lower alkyl esters of these alicyclic polycarboxylic acids, and the like. The alicyclic polybasic acid component can be used alone or in combination of two or more.

Examples of the alicyclic polybasic acid component include 1,2-cyclohexanedicarboxylic acid, 1,2-cyclohexanedicarboxylic anhydride, 1,3-cyclohexanedicarboxylic acid, 1,4-cyclohexanedicarboxylic acid, and 4-cyclohexene- 1,2-dicarboxylic acid and 4-cyclohexene-1,2-dicarboxylic anhydride can be preferably used. Among the above, 1,2-cyclohexanedicarboxylic acid and 1,2-cyclohexanedicarboxylic anhydride can be particularly preferably used from the viewpoint of hydrolysis resistance.

The aliphatic polybasic acid component is generally an aliphatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aliphatic compound, and an esterified product of the aliphatic compound, such as amber. acids, aliphatic polyvalent carboxylic acids such as glutaric acid, adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, octadecanedioic acid, citric acid; Anhydrides of polyhydric carboxylic acids; lower alkyl esters of these aliphatic polycarboxylic acids, and the like. The aliphatic polybasic acid components can be used alone or in combination of two or more.

As the aliphatic polybasic acid component, it is preferable to use a dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms. Examples of the dicarboxylic acid having an alkylene chain having 4 to 18 carbon atoms include adipic acid, pimelic acid, suberic acid, azelaic acid, sebacic acid, undecanedioic acid, dodecanedioic acid, brassylic acid, and octadecanedioic acid. Among them, adipic acid can be preferably used.

The aromatic polybasic acid component generally includes an aromatic compound having two or more carboxyl groups in one molecule, an acid anhydride of the aromatic compound, and a lower alkyl ester of the aromatic compound, For example, aromatic polycarboxylic acids such as phthalic acid, isophthalic acid, terephthalic acid, naphthalene dicarboxylic acid, 4,4'-biphenyldicarboxylic acid, trimellitic acid, and pyromellitic acid; anhydrides of these aromatic polycarboxylic acids ; Examples include lower alkyl esters of these aromatic polycarboxylic acids. The aromatic polybasic acid components can be used alone or in combination of two or more.

As the polyhydric alcohol component, a polyhydric alcohol having two or more hydroxyl groups in one molecule can be suitably used. Examples of the polyhydric alcohol component (a2) include alicyclic diols, aliphatic diols, aromatic diols, and trivalent or higher polyhydric alcohols.

The above alicyclic diol is generally a compound having one or more alicyclic structures (mainly 4- to 6-membered rings) and two hydroxyl groups in one molecule. Examples of the alicyclic diol include dihydric alcohols such as 1,4-cyclohexanedimethanol, tricyclodecane dimethanol, hydrogenated bisphenol A, and hydrogenated bisphenol F; Examples include polylactone diols to which a lactone compound has been added, and these can be used alone or in combination of two or more.

The aliphatic diol is generally an aliphatic compound having two hydroxyl groups in one molecule. Examples of the aliphatic diol include ethylene glycol, propylene glycol, diethylene glycol, trimethylene glycol, tetraethylene glycol, triethylene glycol, dipropylene glycol, 1,4-butanediol, 1,3-butanediol, 2,3 -Butanediol, 1,2-butanediol, 3-methyl-1,2-butanediol, 2-butyl-2-ethyl-1,3-propanediol, 1,2-pentanediol, 1,5-pentanediol , 1,4-pentanediol, 2,4-pentanediol, 2,3-dimethyltrimethylene glycol, tetramethylene glycol, 3-methyl-1,5-pentanediol, 2,2,4-trimethyl-1,3 -Pentanediol, 1,6-hexanediol, 1,5-hexanediol, 1,4-hexanediol, 2,5-hexanediol, 1,9-nonanediol, 1,10-decanediol, 1,12- Examples include dodecane diol, neopentyl glycol; polyether diol compounds such as polyethylene glycol, polypropylene glycol, and polybutylene glycol, and these can be used alone or in combination of two or more.

The above-mentioned aromatic diol is generally an aromatic compound having two hydroxyl groups in one molecule. Examples of the aromatic diol include ester diol compounds such as bis(hydroxyethyl) terephthalate; alkylene oxide adducts of bisphenol A, and these may be used alone or in combination of two or more.

Examples of trivalent or higher polyhydric alcohols include glycerin, trimethylolethane, trimethylolpropane, diglycerin, triglycerin, 1,2,6-hexanetriol, pentaerythritol, dipentaerythritol, sorbitol, mannitol, and the like. Trivalent or higher alcohols; polylactone polyol compounds obtained by adding lactone compounds such as ε-caprolactone to these trivalent or higher alcohols; tris(2-hydroxyethyl)isocyanurate, tris(2-hydroxypropyl)isocyanurate, Examples include tris(hydroxyalkyl)isocyanurates such as tris(2-hydroxybutyl)isocyanurate. Among these, trimethylolpropane is particularly preferred.

The method for producing the polyester resin is not particularly limited, but for example, an acid component containing the above polybasic acid component as an essential component and a polyhydric alcohol component are reacted at 150 to 250° C. for 5 to 10 hours in a nitrogen stream. , esterification reaction or transesterification reaction. In this esterification reaction or transesterification reaction, the acid component and alcohol component may be added at once or may be added in several portions. Alternatively, after first synthesizing a carboxyl group-containing polyester resin, a portion of the carboxyl groups in the carboxyl group-containing polyester resin may be esterified using the alcohol component. Furthermore, after first synthesizing a polyester resin, it may be half-esterified by reacting with an acid anhydride.

During the above esterification or transesterification reaction, a catalyst may be used to promote the reaction. As the catalyst, known catalysts such as dibutyltin oxide, antimony trioxide, zinc acetate, manganese acetate, cobalt acetate, calcium acetate, lead acetate, tetrabutyl titanate, tetraisopropyl titanate, etc. can be used.

Further, the polyester resin can be modified with a fatty acid, an oil or fat, a monoepoxy compound, a monoalcohol compound, a polyisocyanate compound, etc. during the preparation of the resin, or after the esterification reaction or the transesterification reaction.

Examples of the fatty acids mentioned above include coconut oil fatty acids, cottonseed oil fatty acids, hempseed oil fatty acids, rice bran oil fatty acids, fish oil fatty acids, tall oil fatty acids, soybean oil fatty acids, linseed oil fatty acids, tung oil fatty acids, rapeseed oil fatty acids, castor oil fatty acids, and dehydrated castor oil fatty acids. Fatty acids such as oil fatty acids and safflower oil fatty acids; examples include lauric acid, myristic acid, palmitic acid, stearic acid, oleic acid, linoleic acid, and linolenic acid.

Examples of oils and fats include coconut oil, cottonseed oil, hempseed oil, rice bran oil, fish oil, tall oil, soybean oil, linseed oil, tung oil, rapeseed oil, castor oil, dehydrated castor oil, and safflower oil.

Examples of the polyisocyanate compounds used for the above modification include aliphatic diisocyanate compounds such as lysine diisocyanate, hexamethylene diisocyanate, and trimethylhexane diisocyanate; hydrogenated xylylene diisocyanate, isophorone diisocyanate, methylcyclohexane-2,4-diisocyanate, and methylcyclohexane. Alicyclic diisocyanate compounds such as -2,6-diisocyanate, 4,4'-methylenebis(cyclohexylisocyanate), and 1,3-(isocyanatomethyl)cyclohexane; aromatic compounds such as tolylene diisocyanate, xylylene diisocyanate, diphenylmethane diisocyanate, etc. Diisocyanate compounds; organic polyisocyanates themselves such as trivalent or higher valent polyisocyanates such as lysine triisocyanate, or adducts of each of these organic polyisocyanates with polyhydric alcohols, low molecular weight polyester resins, water, etc., or each of the above. Examples include cyclized polymers of organic diisocyanates (eg, isocyanurate), biuret-type adducts, and the like. These can be used alone or in combination of two or more.

The ratio of the polyester resin to the total amount of resin contained in the undercoat is more preferably 85% by mass or more and 100% by mass or less, particularly preferably 90% by mass or more and 100% by mass or less.

The curing agent contained in the undercoat can be used without any particular restriction as long as it can be cured by reacting with the hydroxyl groups of the polyester resin by heating. For example, melamine resin, benzoguanamine resin, urea resin, and polyester resin can be used. Examples include isocyanate compounds.

The above-mentioned melamine resin includes a monohydric alcohol having 1 to 8 carbon atoms, such as methyl alcohol, ethyl alcohol, n-propyl alcohol, i-propyl alcohol, n-butyl alcohol. , i-butyl alcohol, 2-ethylbutanol, 2-ethylhexanol, etc., and partially or fully etherified melamine resins.

Commercially available melamine resins include Cymel 202, Cymel 232, Cymel 235, Cymel 238, Cymel 254, Cymel 266, Cymel 267, Cymel 272, Cymel 285, Cymel 301, Cymel 303, Cymel 325, Cymel 327, and Cymel 350. , Cymel 370, Cymel 701, Cymel 703, Cymel 1141 (manufactured by Daicel Allnex), Yuban 20SE60 (manufactured by Mitsui Chemicals, Inc.), and the like.

Examples of benzoguanamine resin include methylolated benzoguanamine resin obtained by reaction of benzoguanamine and aldehyde. Examples of the aldehyde include formaldehyde, paraformaldehyde, acetaldehyde, and benzaldehyde. Furthermore, the above-mentioned benzoguanamine resins also include those obtained by etherifying this methylolated benzoguanamine resin with one or more alcohols. Examples of the alcohol used for etherification include monohydric alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, isobutyl alcohol, 2-ethylbutanol, and 2-ethylhexanol. . Among these, preferred is a benzoguanamine resin obtained by etherifying at least a portion of the methylol groups of a methylolated benzoguanamine resin with a monohydric alcohol having 1 to 4 carbon atoms.

Specific examples of the benzoguanamine resins include Mycoat 102, Mycoat 105, Mycoat 106 (all manufactured by Mitsui Chemicals), Nikalac SB-201, Nikalac SB-203, Nikalac SB-301, Nikalac SB Methyl etherified benzoguanamine resins such as -303 and Nikalac SB-401 (both manufactured by Sanwa Chemical Co., Ltd.); mixed etherified benzoguanamine resins of methyl ether and ethyl ether such as Cymel 1123 (manufactured by Daicel Ornex); Mixed ethers of methyl ether and butyl ether such as Mycoat 136 (manufactured by Mitsui Chemicals), Nikalak SB-255, Nikalak SB-355, Nikalak BX-37, Nikalak BX-4000 (all manufactured by Sanwa Chemical) Examples include butyl etherified benzoguanamine resins such as Mycoat 1128 (manufactured by Mitsui Chemicals).

Urea resins are obtained by a condensation reaction of urea and formaldehyde, and can be dissolved or dispersed in a solvent or water.

Examples of polyisocyanate compounds include compounds having two or more isocyanate groups in one molecule, such as aromatic diisocyanates such as tolylene diisocyanate, diphenylmethane diisocyanate, xylylene diisocyanate, and naphthalene diisocyanate; tetramethylene diisocyanate, hexamethylene diisocyanate, and dimer. Aliphatic diisocyanates such as acid diisocyanate and lysine diisocyanate; alicyclic diisocyanates such as methylene bis(cyclohexyl isocyanate), isophorone diisocyanate, methylcyclohexane diisocyanate, cyclohexane diisocyanate and cyclopentane diisocyanate; biuret type adducts of the polyisocyanates, isocyanuric ring type Adducts: Free isocyanate group-containing prepolymers made by reacting these polyisocyanates with low-molecular weight or high-molecular weight polyol compounds (for example, acrylic polyols, polyester polyols, polyether polyols, etc.) with an excess of isocyanate groups. Can be done.

Furthermore, as the polyisocyanate compound, the free isocyanate group of the above polyisocyanate compound can be combined with a phenol compound, an oxime compound, an active methylene compound, a lactam compound, an alcohol compound, a mercaptan compound, an acid amide compound, an imide compound, an amine compound, and an imidazole compound. Blocked polyisocyanate compounds blocked with blocking agents such as urea-based compounds, urea-based compounds, carbamic acid-based compounds, and imine-based compounds can also be used.

Further, a curing catalyst may be added as necessary to accelerate curing of the undercoat resin binder. Examples of the curing catalyst when the curing agent is an amino resin include strong acids, neutralized products of strong acids, etc. Typical examples include p-toluenesulfonic acid, dodecylbenzenesulfonic acid, dinonylnaphthalenesulfonic acid, and dinonylnaphthalenesulfonic acid. Examples include sulfonic acid compounds which are strong acids such as nonylnaphthalenedisulfonic acid, and amine neutralized products of these sulfonic acid compounds.

When the curing agent is a blocked polyisocyanate compound, curing catalysts that promote dissociation of the blocking agent of the blocked polyisocyanate compound that is the curing agent, such as tin octylate, dibutyltin di(2-ethyl Examples include organometallic catalysts such as dioctyltin di(2-ethylhexanoate), dibutyltin dilaurate, dibutyltin oxide, dioctyltin oxide, and lead 2-ethylhexanoate.

As mentioned above, the base coating preferably contains a white pigment. In this case, the reflectance of the coating layer 21 can be improved. The undercoat preferably contains titanium oxide as a white pigment, and more preferably contains rutile-type titanium oxide. Since rutile titanium oxide has a high refractive index, it is possible to further improve the reflectance of the coating layer 21. In the undercoat, the solid volume concentration of the rutile titanium oxide is preferably 20% or more and 35% or less, more preferably 20% or more and 30% or less, particularly preferably 22% or more and 28% or less. The average particle size of the rutile titanium oxide contained in the undercoat is preferably 200 nm or more and 400 nm or less, more preferably 250 nm or more and 350 nm or less. The average particle size of the rutile-type titanium oxide was determined by observing the undercoat layer 23 with an electron microscope magnified 10,000 times, and excluding 20% of the particles with the smallest particle size and 5% of the largest particles. This is the arithmetic average value of the particle sizes of the remaining rutile-type titanium oxide.

There are no particular restrictions on the manufacturing method, the presence or absence of surface treatment, or the type of titanium oxide, but titanium oxide that has as high a hiding power as possible and a high degree of whiteness is preferred. Among these, rutile-type titanium oxide is manufactured by the chlorine method and It is preferable that the surface be treated with , alumina, silica, titania, or the like. Such titanium oxide is particularly preferred because it has high hiding power and whiteness.

Commercially available titanium oxide products include, for example, Ti-Pure R706, Ti-Pure R960, Ti-Pure R902+ (manufactured by DuPont, trade name, titanium oxide pigment produced by the chlorine method), Typeque CR-50, and Tipeque CR-. 60, Taipeke CR-95 (manufactured by Ishihara Sangyo Co., Ltd., trade name, titanium oxide pigment produced by the chlorine method), CR-826 (manufactured by Tronox, trade name, titanium oxide pigment produced by the chlorine method), and the like.

Note that the undercoat paint may contain a solvent, a leveling agent, a pigment dispersant, an anti-bleeding agent, etc. in order to improve painting workability.

Curtain coating, roll coating, dipping coating, spray coating, etc. can be employed as the coating method for the undercoat paint. When pre-coating an undercoat by coil coating, it is preferable to adopt a curtain coating method or a roll coating method from the viewpoint of economy. When applying the roll coating method, the top feed or bottom feed method using three rolls is recommended in order to achieve the best uniformity of the coated surface, but for practical purposes, the bottom feed method using the usual two rolls ( So-called natural reverse painting, natural painting) may also be used.

The curing conditions (baking conditions) of the undercoat are usually about 15 seconds to 30 minutes at a material maximum temperature (PMT) of 120 to 260°C. In the field of pre-coating, in which coating is performed by coil coating, etc., the coating is usually carried out at a maximum temperature of 160 to 260° C. for 15 to 90 seconds.

(2) Coating layer The coating layer 21 is provided on the undercoat layer 23 and covers the undercoat layer 23. Therefore, the coating layer 21 covers the base material 20 and constitutes the surface of the base material 2. Covering layer 21 contains a binder and a white pigment. Although the coating layer 21 of this embodiment is in direct contact with the undercoat layer 23, the present invention is not limited to this, and an appropriate layer may be interposed between the undercoat layer 23 and the coating layer 21.

The coating layer 21 has a high reflectance of light. Specifically, the coating layer 21 has a reflectance of 85% or more for light having a wavelength of 555 nm. This configuration can be achieved, for example, by the coating layer 21 containing a high concentration of white pigment relative to the binder. In the coating layer 21, when the concentration of the white pigment to the binder is high, reflection is likely to occur not only at the white pigment-binder interface but also at the white pigment-air interface and the binder-air interface. Therefore, the light reflectance of the coating layer 21 can be increased. Further, it is preferable that the coating layer 21 has a reflectance of 92.5% or more for light with a wavelength of 450 nm or more and 750 nm or less, and a reflectance of 95% or more for light with a wavelength of 555 nm. In this case, the coating layer 21 can efficiently reflect light. Further, when the covering material 1 is used as a reflector, high illuminance can be obtained.

The coating layer 21 of this embodiment will be explained in more detail.

In the coating layer 21, the concentration of the white pigment is preferably 150 parts by volume or more, more preferably 200 parts by volume or more, even more preferably 500 parts by volume or more, and even more preferably 800 parts by volume or more, based on 100 parts by volume of the binder. In this case, the reflectance of the coating layer 21 can be improved without increasing the thickness of the coating layer 21. Preferably, the concentration of white pigment is less than 1500 parts by volume per 100 parts by volume of binder. In this case, the coating layer 21 can be prevented from becoming brittle, and the strength of the coating layer 21 can be ensured.

The volume porosity of the coating layer 21 is preferably 5 vol% or more, more preferably 9 vol% or more, and even more preferably 20 vol% or more. Further, the porosity in the cross section is preferably 2% or more, more preferably 5% or more, and even more preferably 10% or more. In this case, the reflectance of the coating layer 21 can be improved without increasing the thickness of the coating layer 21. The coating layer 21 preferably has a volumetric porosity of less than 35 vol%. Further, the porosity in the cross section is preferably less than 35%. In this case, the coating layer 21 can be prevented from becoming brittle, and the strength of the coating layer 21 can be ensured.

The concentration (parts by volume) of the binder and white pigment and the porosity in volume in the coating layer 21 can be measured by the following method. First, a part of the coating layer 21 is scraped off to check the components of the binder and white pigment. The method of confirming the components is not particularly limited. For example, the components of the binder can be confirmed by methods such as FT-IR and NMR. For example, the components of the white pigment can be confirmed by methods such as XRD and FT-IR. Next, a sample having a constant area a and a constant thickness b is scraped off from the coating layer 21. The apparent volume c of this sample is a×b. Next, the mass d of the sample is measured using a weighing machine capable of measuring to three or more valid digits. The entire sample is then heated until the binder decomposes. Next, the mass e of the sample after heating is measured. The mass e corresponds to the mass of the white pigment, and the mass f of the binder can be calculated by subtracting the mass e from the mass d. Based on the specific gravity of these binder components, the mass f of the binder, the specific gravity of the white pigment component, and the mass e of the white pigment, it is possible to calculate the volume g of the binder and the volume h of the white pigment that occupied the volume c. can. Furthermore, from these values, the concentration (parts by volume) of the binder and white pigment and the porosity in volume can be determined.

The porosity in the cross section of the covering layer 21 can be measured by the following method. First, a sample scraped from the covering layer 21 is embedded in resin and polished to form a smooth cross section that is perpendicular to the surface of the covering layer 21. This cross section is magnified 10,000 times and photographed using a scanning microscope. By comparing the area of the white pigment and the area of the voids in the obtained image, the porosity of the cross section can be determined.

The thickness of the coating layer 21 is preferably 5 μm or more and less than 100 μm. When the thickness of the coating layer 21 is less than 100 μm, it is possible to suppress the coating layer 21 from becoming brittle. The thickness of the coating layer 21 is preferably 20 μm or more and 50 μm or less, more preferably 25 μm or more and 35 μm or less, from the viewpoint of finished appearance. In this case, the light reflectance of the coating layer 21 can be improved, and the coating layer 21 can be prevented from becoming brittle, and the strength of the coating layer 21 can be ensured. Note that the covering layer 21 is not limited to being composed of a single layer, but may be composed of a plurality of layers.

The binder contained in the coating layer 21 may be a thermoplastic resin or a thermosetting resin. The binder may be a thermally melted solid resin, a resin dissolved in an organic solvent, or a pulverized solid resin. The binder may be water-soluble or a water-dispersed emulsion type. The binder may be an ultraviolet curable resin or an electron beam curable resin. The binder may also contain a crosslinking agent. The binder can include, for example, one or more selected from the group consisting of polyester resin, urethane resin, acrylic resin, epoxy resin, melamine resin, vinyl chloride resin, fluororesin, and silicone resin.

The white pigment contained in the coating layer 21 preferably contains rutile-type titanium oxide. That is, it is preferable that the coating layer 21 contains rutile-type titanium oxide. Since rutile titanium oxide has a high refractive index, it easily reflects light at the white pigment-binder interface. Therefore, by including the rutile titanium oxide as a white pigment in the coating layer 21, the light reflectance of the coating layer 21 can be improved. The rutile-type titanium oxide may be surface-treated with Al, Si, Zr, an organic substance, or the like. The coating layer 21 may contain commercially available rutile-type titanium oxide as a white pigment. Examples of commercially available rutile-type titanium oxides include the "Taipeke TM" series manufactured by Ishihara Sangyo Co., Ltd. and the "Titanics" series manufactured by Teika Corporation. The coating layer 21 may contain a white pigment other than rutile titanium oxide.

The average particle size of the white pigment contained in the coating layer 21 is preferably 200 nm or more and 400 nm or less. In this case, the surface area of the white pigment can be increased, the reflectance of the coating layer 21 can be improved, and the transmittance of light on the long wavelength side can be prevented from increasing.

The coating layer 21 can be formed from a coating material containing the above-mentioned binder and white pigment. Specifically, the coating layer 21 is obtained by baking and drying the coating film of the coating paint. Examples of the coating method include roller curtain coating, curtain flow coating, air spray coating, die coater coating, dip coating, inkjet coating, and the like.

(3) Intermediate protective layer The intermediate protective layer 4 is provided between the base material 2 and the photocatalyst layer 3, and more specifically, between the coating layer 21 and the photocatalyst layer 3. Therefore, the intermediate protective layer 4 covers the covering layer 21 and is in direct contact with the covering layer 21.

The main component of the intermediate protective layer 4 is preferably silicon oxide or siloxane polymer.

The silicon oxide includes at least one selected from the group consisting of silicon monoxide, silicon dioxide, and compounds in which the ratio of silicon to oxygen is not stoichiometric (for example, SiO _1.5 and SiO _1.8 ). Silicon oxide may be crystalline, amorphous, or quasi-crystalline. Preferably, silicon oxide includes amorphous silica. In this case, the flexibility of the intermediate protective layer 4 can be improved more than when silicon oxide is crystalline silica.

Siloxane polymers include tetraalkoxysilanes having alkoxy groups having 1 to 4 carbon atoms, alkoxysilanes having alkyl groups having 1 to 12 carbon atoms, alkoxysilanes having aryl groups, and alkyl groups having 1 to 12 carbon atoms. Dehydration obtained by a hydrolysis reaction and subsequent condensation reaction of at least one alkoxysilane selected from the group consisting of alkoxysilanes having both aryl groups and an alkoxysilane having an epoxy group or an alkoxysilane having an amino group. It is preferable to include a condensate. The alkoxysilane condensate is preferably one produced by hydrolyzing the alkoxysilane used as a raw material to once produce a hydrolyzate and then condensing it in a dry baking (heat treatment) step. When the main component of the intermediate protective layer 4 is silicon oxide or a siloxane polymer, it is preferable to suppress deterioration of the intermediate protective layer 4 due to the photocatalytic action of the photocatalyst 30 contained in the photocatalyst layer 3. In particular, since the main component of the intermediate protective layer 4 is an inorganic-organic composite polymer in which amorphous silica or a polysiloxane-based inorganic polymer containing silicon as the main component is blended with a large number of alkyl groups and aryl groups, the intermediate protective layer 4 The weather resistance, processability, and stability against photocatalysts of No. 4 can be improved.

Examples of the alkyl group having 1 to 12 carbon atoms include methyl group, ethyl group, propyl group, butyl group, hexyl group, 2-ethylhexyl group, and dodecyl group; examples of the aryl group include phenyl group, tolyl group, and xylyl group. group, naphthyl group, etc. Among these alkyl groups, methyl and phenyl groups are preferred. That is, the alkoxysilane having an alkyl group having 1 to 12 carbon atoms preferably includes an alkoxysilane having a methyl group, an alkoxysilane having a phenyl group, an alkoxysilane having a methyl group and a phenyl group, and an alkoxysilane having a phenyl group. It is particularly preferable to include an alkoxysilane. The siloxane polymer preferably contains two or more types of alkoxysilanes having different organic groups, or alkoxysilanes containing two or more different types of organic groups.

When the intermediate protective layer 4 contains the above-mentioned inorganic-organic composite polymer, the inorganic-organic composite polymer has methyl groups and/or It is preferable that phenyl groups are bonded, more preferably in a ratio of 0.05 to 1.2. In this case, moderate flexibility can be imparted to the intermediate protective layer 4, and the photocatalytic activity of the photocatalytic layer 3 provided on the intermediate protective layer 4 can be improved.

Intermediate protective layer 4 may contain a photocatalyst. In this case, the proportion of the photocatalyst in the intermediate protective layer 4 is preferably smaller than the proportion of the photocatalyst in the photocatalyst layer 3. The mass ratio of the photocatalyst to the entire intermediate protective layer 4 is preferably 0.05% or more and 20% or less, more preferably 0.1% or more and 15% or less. In this case, even if the intermediate protective layer 4 is exposed due to deterioration of the photocatalytic layer 3 or the like, the photocatalyst contained in the intermediate protective layer 4 can exhibit a photocatalytic effect. Further, deterioration of the resin contained in the coating layer 21 due to the photocatalytic action of the photocatalyst contained in the intermediate protective layer 4 can be suppressed.

The thickness of the intermediate protective layer 4 is preferably 0.1 μm or more and 3 μm or less, more preferably 0.1 μm or more and 2.5 μm or less, and even more preferably 0.3 μm or more and 2 μm or less.

The intermediate protective layer 4 can be formed by forming a coating film from a protective layer coating material containing the above-mentioned silicon oxide or siloxane polymer and, if necessary, a photocatalyst, and then heating and curing this coating film. The coating method for the protective layer can be applied by, for example, a dip coating method, a spray coating method, a bar coating method, a roll coating method, or a spin coating method. The heating conditions for the coating film of the paint for the protective layer are such that the heat treatment is preferably performed in a temperature range of 150° C. or higher and about 400° C. for about 1 hour to several seconds.

(4) Photocatalyst layer The photocatalyst layer 3 is located on the coating layer 21, and more specifically on the intermediate protective layer 4.

It is preferable that the photocatalyst layer 3 contains at least one of silicon oxide and a siloxane polymer.

Preferably, silicon oxide includes, for example, amorphous silica.

The siloxane polymer preferably contains a resin made of a dehydrated condensate obtained by hydrolysis and condensation reaction of a tetraalkoxysilane having an alkoxy group having 1 to 4 carbon atoms or an alkoxysilane having an epoxy group, for example.

Examples of tetraalkoxysilanes having an alkoxy group having 1 to 4 carbon atoms include tetramethoxysilane, tetraethoxysilane, tetra-n-propoxysilane, tetra-i-propoxysilane, tetra-n-butoxysilane, and tetra- Examples include i-butoxysilane, tetra-sec-butoxysilane, and tetra-tert-butoxysilane.

Examples of alkoxysilanes having epoxy groups include γ-glycidoxypropyltrimethoxysilane, γ-glycidoxypropyltriethoxysilane, γ-glycidoxypropyltripropoxysilane, γ-glycidoxypropyltributoxysilane. , 3,4-epoxycyclohexylmethyltrimethoxysilane, 3,4-epoxycyclohexylmethyltriethoxysilane, β-(3,4-epoxycyclohexyl)ethyltrimethoxysilane, and β-(3,4-epoxycyclohexyl)ethyl Includes triethoxysilane, etc. Among alkoxysilanes having an epoxy group, γ-glycidoxypropyltriethoxysilane is particularly easy to handle.

The above-mentioned resin made of an alkoxysilane and a condensate of alkoxysilane is a resin having high stability against photocatalysts, which is mainly composed of an inorganic component, siloxane, and a small amount of epoxy group is blended therein. Among these, alkoxysilanes having an epoxy group are preferred because they have the effect of lowering the baking temperature of the film. Generally, when forming a polysiloxane film using only silicon alkoxide as a starting material, heat treatment at 400 to 500°C for several hours is required to efficiently carry out the series of steps from dehydration condensation to curing. . When forming the photocatalyst layer 3, by introducing an epoxy group, it is possible to reduce the treatment temperature to about 150 to 200°C and shorten the heat treatment time, and it is possible to achieve heat treatment conditions that allow coil coating.

It is preferable that the photocatalyst layer 3 contains an inorganic polymer consisting only of tetraalkoxysilane and a condensate of these alkoxysilanes. Tetraalkoxysilane generates siloxane bonds containing hydroxyl groups through hydrolysis and dehydration condensation, and can be reduced to only siloxane bonds by further aging and heat treatment, and the photocatalyst layer 3 deteriorates due to the photocatalytic action of the photocatalyst 30. can be restrained from doing so.

The ratio of epoxy groups contained in the photocatalyst layer 3 is preferably 0 to 0.25, more preferably 0 to 0.22, per 1 Si--O bond. In this case, the photocatalyst resistance of the photocatalyst layer 3 can be improved.

Photocatalyst layer 3 includes photocatalyst 30. The photocatalyst 30 is a substance that exhibits photocatalytic action when irradiated with light. A specific example of the photocatalyst 30 is titanium oxide. As titanium oxide, there are rutile-type titanium oxide, anatase-type titanium oxide, and brookite-type titanium oxide. It is preferable that the photocatalyst 30 contains anatase-type titanium oxide. That is, the photocatalyst layer 3 preferably contains anatase titanium oxide. This is because the photocatalytic activity of anatase-type titanium oxide is higher than that of other titanium oxides. In particular, the photocatalyst 30 is preferably a substance that exhibits photocatalytic action when exposed to visible light. That is, the photocatalyst 30 is preferably a visible light-excited photocatalyst. In this case, the photocatalytic effect of the photocatalyst 30 can be expressed by visible light, and for example, the photocatalytic effect of the photocatalyst 30 can be expressed by light from a fluorescent lamp, an LED, or the like. Examples of visible light-excited photocatalysts include those in which anatase-type titanium oxide is doped with anions such as nitrogen and sulfur, and those in which anatase-type titanium oxide is supported with Pt particles.

When doping a titanium oxide crystal with nitrogen, depending on the state of nitrogen, (i) some of the oxygen sites in the titanium oxide crystal are replaced with nitrogen atoms and have a Ti-O-N structure, (ii) oxidized One or more types of titanium crystals in which nitrogen atoms exist between the lattices and (iii) nitrogen atoms in the grain boundaries of polycrystalline aggregates of titanium oxide crystals can be obtained. In particular, the photocatalyst (i) has a stabilized crystal structure due to the Ti-O-N structure, so it can exhibit photocatalytic activity under both visible light and ultraviolet rays, and can maintain photocatalytic activity over a long period of time. can be expressed.

The photocatalyst 30 may be in the form of a powder, an aqueous sol or colloid dispersed in water, or an organic solvent sol or colloid dispersed in a polar solvent such as alcohol or a nonpolar solvent such as toluene. When the photocatalyst 30 is an organic solvent-based sol or colloid, the photocatalyst paint may be diluted with water or an organic solvent depending on its dispersibility. Moreover, in order to improve the dispersibility of the photocatalyst 30, the photocatalyst 30 may be surface-treated.

When the photocatalyst 30 contains anatase-type titanium oxide doped with nitrogen, it can be produced, for example, by the following methods (I) to (IV).
(I) A method of heat treating titanium oxide or hydrous titanium oxide in an atmosphere containing at least one gas selected from the group consisting of ammonia gas, nitrogen gas, and a mixed gas of nitrogen gas and hydrogen gas.
(II) A method of heat treating a titanium alkoxide solution in an atmosphere containing at least one gas selected from the group consisting of ammonia gas, nitrogen gas, and a mixed gas of nitrogen gas and hydrogen gas.
(III) In the emulsion combustion method, ions or molecules containing nitrogen elements other than nitrate ions, such as ammonia and hydrazine, are present in the titanium salt aqueous solution or suspension, which is the aqueous phase in the emulsion, and are contained in the emulsion. The amount of oxygen in the reactor is less than that required for the combustion components, including oil and surfactants, to be completely combusted and for the metal ions or metal compounds contained in the aqueous solution to form the most stable oxides in the atmosphere. A method of spraying and burning an emulsion in an atmosphere introduced into a chamber.
(IV) In the emulsion combustion method, the titanium salt aqueous solution or suspension, which is the aqueous phase in the emulsion, does not contain ions or molecules containing nitrogen atoms other than nitrate ions, such as ammonia or hydrazine, and contains nitrogen other than nitrogen gas. A method of spray combustion of an emulsion in an atmosphere containing a gas such as ammonia and in which the amount of oxygen introduced into the reactor is less than the required amount of oxygen.
(V) A method of heat-treating or plasma-treating a titanium nitride crystal or a titanium nitride oxide crystal in an oxidizing atmosphere containing oxygen, ozone, water molecules, or a compound containing a hydroxyl group.
(VI) A method of heating a mixture of titanium oxide and a nitrogen compound that is adsorbed to titanium oxide at room temperature.

The primary particle diameter of the photocatalyst 30 is preferably 0.5 μm or less, more preferably 0.1 μm or less, and particularly preferably 0.05 μm or less. The lower limit of the primary particle diameter of the photocatalyst 30 is not particularly limited, but is, for example, 5 nm or more. The smaller the primary particle diameter of the photocatalyst 30, the more the photocatalytic effect can be improved. Moreover, the smaller the primary particle diameter of the photocatalyst 30, the more difficult it becomes to disperse, and the more aggregates of particles of the photocatalyst 30 are formed. Resin is often absent in the interstices of this aggregate. In the photocatalyst layer 3, by forming a region where no resin exists, photocatalytic effects such as antifouling effects and inactivation of bacteria or viruses can be effectively performed.

When the photocatalyst 30 is fine particles, it is difficult to disperse the photocatalyst 30 in the photocatalyst layer 3, and the particles of the photocatalyst 30 may form aggregates. Usually, the resin component constituting the photocatalyst layer 3 is often not present in the gaps between the aggregates, which may have the advantage that bacteria or viruses can easily reach the photocatalyst 30. Further, in the photocatalyst layer 3, it is desirable that the photocatalyst 30 is uniformly dispersed, but it is not necessarily necessary that the photocatalyst 30 be uniformly dispersed. When the photocatalyst 30 is not uniformly dispersed, when the particles of the photocatalyst 30 form aggregates, when the concentration of the photocatalyst 30 is different between the outermost surface and the inside, the concentration of the photocatalyst substance is gradually increased. Even in these states, it can be suitably used.

By varying the dispersion state of the photocatalyst 30 in the photocatalyst layer 3, the photocatalytic effect can be expressed over a long period of time from the initial stage, and deterioration of the resin contained in the photocatalyst layer 3 can be suppressed. For example, the photocatalyst 30 included in the photocatalyst layer 3 has a maximum particle size distribution, one of the maximum values of the particle size distribution of the photocatalyst 30 is in the range of 0.5 μm to 5 μm, and It is preferable that one of the maximum values of the particle size distribution of the photocatalyst is 0.2 μm or less. The photocatalyst 30 in the photocatalyst layer 3 preferably has high activity because it exhibits photocatalytic action, and as a result of agglomeration of fine particles of the photocatalyst 30, one of the maximum values of the particle size distribution is in the range of 0.5 μm to 5 μm. It is preferable that the The maximum value of the particle size distribution of the photocatalyst 30 in the photocatalyst layer 3 is more preferably 0.5 μm to 3 μm, and even more preferably 0.6 μm to 2 μm. Further, the maximum value of the particle size distribution of the photocatalyst in the intermediate protective layer 4 is preferably 0.15 μm or less. The maximum value of the photocatalyst contained in the photocatalyst layer 3 and the intermediate protective layer 4 preferably does not exceed 20 μm, which is twice the total film thickness, and more preferably does not exceed 10 μm. Further, in the photocatalyst layer 3, it is preferable that the maximum value of the particle size distribution of the photocatalyst 30 is less than 0.2 μm. In this case, the photocatalytic activity of the photocatalytic layer 3 is easily developed from the initial stage.

The proportion of the photocatalyst 30 contained in the photocatalyst layer 3 is preferably 50% or less, preferably 40% or less, and preferably 30% or less in mass proportion to the entire photocatalyst layer 3. In this case, deterioration of the resin contained in the photocatalyst layer 3 due to the photocatalytic action of the photocatalyst 30 can be suppressed while the photocatalytic action of the photocatalyst 30 is efficiently expressed. The lower limit of the proportion of the photocatalyst 30 contained in the photocatalyst layer 3 is not particularly limited as long as it can exhibit photocatalytic action, but for example, it is preferably 0.05% or more, more preferably 0.2% or more, and 0.5%. The above is more preferable.

The photocatalyst layer 3 may contain the photocatalyst 30 as it is, or may contain the photocatalyst 30 supported on the surface of a catalyst carrier. When the photocatalyst layer 3 includes a catalyst carrier, the area in which the photocatalyst 30 and the polymer component are in direct contact can be reduced, so that deterioration of the polymer component by the photocatalyst 30 can be suppressed. Further, depending on the polymer component, it may be difficult to disperse the photocatalyst 30, but by using a suitable single catalyst, the photocatalyst 30 can be easily dispersed. The photocatalyst layer 3 preferably contains an inorganic oxide that is stable to the photocatalyst 30 as a catalyst carrier, and is selected from the group consisting of silicon oxide, aluminum oxide, magnesium oxide, zirconium oxide, iron oxide, and calcium oxide. It is preferable to include one or more of the following.

The photocatalyst layer 3 is substantially composed of silicon oxide or a siloxane polymer and a photocatalyst 30. Therefore, if the content of the photocatalyst 30 is about 10%, the remainder can be silicon oxide or siloxane polymer. However, in order to improve the design, corrosion resistance, abrasion resistance, catalytic function, etc. of the photocatalytic layer 3, the photocatalytic layer 3 contains coloring pigments, extender pigments, catalysts other than photocatalysts, rust preventive pigments, metal powders, high frequency loss agents, etc. , aggregate, etc. may be included. The photocatalyst layer 3 may contain, for example, oxides such as SiO ₂ , TiO ₂ , Al ₂ O ₃ , composite oxides containing two or more types of metal elements, metal powders such as Zn powder, Al powder, etc. Can be done. Moreover, the photocatalyst layer 3 can contain a non-chromic acid-based rust preventive pigment such as calcium molybdate, calcium phosphomolybdate, and aluminum phosphomolybdate. Further, the photocatalyst layer 3 can contain Zn--Ni ferrite as a high-frequency loss agent. Moreover, the photocatalyst layer 3 can contain potassium titanate fibers as an aggregate. The amount of these components in the photocatalyst 30 is not particularly limited, but is preferably, for example, 30% or less, more preferably 20% or less, and particularly preferably 15% or less.

The photocatalyst layer 3 contains Si as a main element, but also contains one or more elements selected from the group consisting of B, Al, Ge, Ti, Y, Zr, Nb, and Ta as an element other than Si. Good too. In particular, when Al, Ti, Nb, and Ta are added to the system using an acid as a catalyst, the solidification of the film can be completed at a low temperature or in a short time. When these metal-containing alkoxides are added using an acid as a catalyst, the ring-opening rate of the epoxy increases and the film can be cured at low temperatures and in a short time. The photocatalyst layer 3 preferably contains a Ti alkoxide such as Ti-ethoxide and Ti-isopropoxide. Furthermore, in the case of a system in which Zr is added, the alkali resistance of the film is significantly improved, so it is particularly suitable for use in applications where alkali resistance is required.

The thickness of the photocatalyst layer 3 is preferably 0.1 μm or more and 3 μm or less, more preferably 0.1 μm or more and 2.5 μm or less, even more preferably 0.3 μm or more and 2 μm or less, and particularly preferably 1 μm or more and 3 μm or less. In this case, the photocatalytic action of the photocatalyst 30 contained in the photocatalyst layer 3 can be particularly exhibited.

The total thickness of the photocatalyst layer 3 and the intermediate protective layer 4 is preferably 5 μm or less. In this case, the workability of the covering material 1 and the adhesion of the processed portion can be improved. The total thickness of the photocatalyst layer 3 and the intermediate protective layer 4 is more preferably 4 μm or less, particularly preferably 3 μm or less. In this case, the processability of the photocatalyst layer 3 and the intermediate protective layer 4 can be improved. The lower limit of the total thickness of the photocatalyst layer 3 and intermediate protective layer 4 is not particularly limited, but is preferably 0.1 μm or more, more preferably 0.3 μm or more.

The photocatalyst layer 3 can be formed, for example, by forming a coating film from a photocatalyst paint containing the above-mentioned silicon oxide or siloxane polymer and the photocatalyst 30, and then heating and curing this coating film. The photocatalyst layer 3 may be formed on the intermediate protective layer 4 after forming the intermediate protective layer 4, and after forming a coating film of a protective layer paint on the coating layer 21, a photocatalytic paint is applied on this coating film. It may be formed simultaneously with the intermediate protective layer 4 by forming a coating film and heating and curing the two coating films. As a method for applying the photocatalytic paint, for example, a dip coating method, a spray coating method, a bar coating method, a roll coating method, or a spin coating method can be adopted. The coating film of the photocatalytic paint is preferably heated in a temperature range from 150° C. to about 400° C. for about 1 hour to several seconds.

2-1-2. Photocatalytic action The photocatalytic action expressed by the coating material 1 according to the first embodiment will be described with reference to FIG. 2.

FIG. 2 is a diagram for explaining the photocatalytic action when the photocatalytic layer 3 of the coating material 1 shown in FIG. 1 is irradiated with light. According to FIG. 2, the light reaching the photocatalyst 30 causes a photocatalytic effect. Further, a part of the light irradiated onto the photocatalyst layer 3 passes through the photocatalyst layer 3. The light that has passed through the photocatalyst layer 3 passes through the intermediate protective layer 4 and reaches the coating layer 21 . Since the coating layer 21 of this embodiment has a reflectance of 85% or more for light with a wavelength of 555 nm, the light that reaches the coating layer 21 is efficiently reflected by the coating layer 21. The light reflected by the coating layer 21 passes through the intermediate protective layer 4 and reaches the photocatalyst layer 3 again. The light reflected by the coating layer 21 and reaching the photocatalyst layer 3 also exhibits a photocatalytic effect. That is, in the coating material 1 of the present embodiment, not only the light directly irradiated onto the photocatalyst layer 3 but also the light that has passed through the photocatalyst layer 3 and reflected by the coating layer 21 can reach the photocatalyst 30. Therefore, light can be efficiently made to reach the photocatalyst 30, and the photocatalytic action of the photocatalyst 30 can be efficiently expressed. As a result, a high photocatalytic effect can be exhibited from the initial stage when the photocatalytic layer 3 is irradiated with light, and this photocatalytic effect can be maintained for a long period of time.

Furthermore, since the photocatalyst 30 of the present embodiment is a visible light-excited photocatalyst, it can exhibit photocatalytic action not only with ultraviolet light with a wavelength of 380 nm or less but also with visible light with a wavelength of 400 nm or more. Therefore, in the coating material 1 of this embodiment, the photocatalytic effect can be expressed not only by sunlight containing a large amount of ultraviolet rays, but also by light from a fluorescent lamp, a xenon lamp, an LED, or the like. In particular, the coating layer 21 has a high reflectance for light with a wavelength of 555 nm, and since 555 nm is approximately the middle of the wavelengths in the visible light range (380-750 nm), it can efficiently reflect light in the entire visible light range. Since the photocatalyst 30 of this embodiment is a visible light-excited photocatalyst, the wavelength range of light that is easily reflected by the coating layer 21 and the wavelength range in which the photocatalyst 30 can exhibit photocatalytic action overlap. Therefore, the photocatalytic action of the photocatalyst 30 can be expressed by the visible light that directly reaches the photocatalyst 30 and the visible light that is reflected by the coating layer 21, and the photocatalytic effect is high from the initial stage when the photocatalyst layer 3 is irradiated with visible light. The photocatalytic effect can be expressed and the photocatalytic effect can be maintained for a long period of time.

The photocatalytic action exhibited by the coating material 1 of this embodiment includes a hydrophilic action, an antifouling action, an action to inactivate bacteria or viruses, and the like. In particular, in this embodiment, it is easy to express the inactivation effect of bacteria or viruses, and the inactivation effect of bacteria or viruses can be expressed even at an early stage compared to a coating material in which a photocatalyst layer is provided on the surface of a general color steel plate. and the inactivation effect can be maintained for a long period of time. This can be achieved by the coating layer 21 having a reflectance of 85% or more for light with a wavelength of 555 nm, and is more easily achieved by the photocatalyst 30 being a visible light-excited photocatalyst. Furthermore, the photocatalytic action exhibited by the coating material 1 also includes antifouling, hydrophilic functions, decomposition of organic matter, and the like.

2-2. Second embodiment 2-2-1. Composition of Covering Material The covering material 1 according to the second embodiment differs from the covering material 1 according to the first embodiment in that it includes a covering layer 210 instead of the covering layer 21, and the other points are the covering material 1 according to the first embodiment. It has the same configuration as material 1. For this reason, in the coating material 1 of this embodiment, as shown in FIG. 3, the intermediate protective layer 4 and the photocatalyst layer 3 are laminated in this order on the base material 2. The base material 2 also includes a base material 20, a coating layer 210, and an undercoat layer 23 provided between the base material 20 and the coating layer 210. For this reason, in the coating material 1 of this embodiment, the photocatalyst layer 3 is provided on the coating layer 210.

Like the coating layer 21, the coating layer 210 of this embodiment has a reflectance of 85% or more for light with a wavelength of 555 nm, and it is particularly preferable that the diffuse reflectance of light with a wavelength of 555 nm is 85% or more. In this case, the light that has passed through the photocatalyst layer and reached the coating layer 210 can be diffused and reflected over a wide area of the photocatalyst layer 3. Thereby, a particularly high photocatalytic effect can be exhibited from the initial stage when the photocatalytic layer 3 is irradiated with light.

Note that "diffuse reflectance" refers to the diffuse reflectance of light with a wavelength of 555 nm, which does not include specular reflection, by an integrating sphere. This diffuse reflectance is defined as a percentage when the diffuse reflectance at a wavelength of 555 nm measured using a diffuse reflectance measuring device using an integrating sphere is set to 100 for the reference white plate. Examples of the diffuse reflectance measurement device include "CM-3700d" manufactured by Minolta Corporation (currently Konica Minolta Corporation) and spectrophotometer "AVAL265" manufactured by Shimadzu Corporation. Diffuse reflectance is measured in accordance with JIS Z 8722 geometric condition c, etc., using an integrating sphere (a sphere whose inner surface is coated with white paint such as barium sulfate, which reflects light almost completely diffusely). Then, the reflectance at a wavelength of 555 nm is measured as a percentage when the reference white plate (material: barium sulfate) is taken as 100 under the condition of diffused illumination and light reception in an 8° direction. For the diffuse reflectance, the SCE (specular reflection elimination) method can be used to measure light by removing specular reflection light. In the SCE method, specularly reflected light is removed and only diffusely reflected light is measured, so the evaluation of color and gloss is similar to that seen with the naked eye. The upper limit of the diffuse reflectance of the coating layer 210 is 100%.

The covering layer 210 will be explained in detail below.

In this embodiment, the structure of the first example or the structure of the second example shown below can be adopted as the coating layer 210, for example. Note that the configuration of the coating layer 210 is not limited to the configurations of the first example and second example below.

(First example)
The coating layer 210 of the first example includes a binder resin and a pigment. For this reason, the coating layer 210 is formed from a coating material containing a binder resin and a pigment.

The binder resin preferably includes a polyester resin (hereinafter also referred to as polyester resin A) having a number average molecular weight of 19,000 or more and 28,000 or less. Since the coating layer 210 of this embodiment has a high pigment concentration in the coating paint, it is necessary to ensure the ability to bind pigments together (binder ability). In this regard, by blending polyester resin A as a resin contained in the coating paint, the binder ability can be ensured and the processability of the coating layer 210 can be improved. Furthermore, when a polyester resin having a high number average molecular weight is employed, the viscosity of the coating coating material increases, so that the solid content concentration in the coating coating material tends to increase. On the other hand, the coating paint of this embodiment has a high pigment concentration and a relatively low resin concentration, so even if the number average molecular weight of the polyester resin A is within the above range, the viscosity is suitable for forming a coating film. It is easy to form a coating film from the coating paint. Therefore, a thick coating film can be formed from the coating material while suppressing the occurrence of wrinkles (small bubble-like blisters and holes). Furthermore, since the number average molecular weight of the polyester resin is 19,000 or more, excellent moldability can be imparted to the coating material 1. Further, by setting the number average molecular weight of the polyester resin to 28,000 or less, it is possible to ensure the scratch resistance of the covering layer 210 while imparting appropriate flexibility to the covering layer 210. The number average molecular weight of the polyester resin A is more preferably 19,000 or more and 26,000 or less, particularly preferably 20,000 or more and 23,000 or less. The ratio of polyester resin A to the total amount of binder resin is preferably 20% by mass or more and 100% by mass or less, more preferably 30% by mass or more and 80% by mass or less, and particularly preferably 40% by mass or more and 60% by mass or less.

It is also preferable that the binder resin contains a polyester resin (hereinafter also referred to as polyester resin B) having a number average molecular weight of 2,000 or more and 6,000 or less and a hydroxyl value of 20 or more. The coating layer 210 of this embodiment may have a structure in which resin is dispersed between pigments. In this structure, by combining polyester resin A and polyester resin B, polyester resin B can enter the gap into which polyester resin A is difficult to enter. Therefore, the polyester resin B functions as a binder between the pigments or between the pigments and the polyester resin A, and can improve the strength, processability, and adhesion of the coating layer 210.

In addition, since the number average molecular weight of the polyester resin B is 2000 or more, the strength of the coating layer 210 can be ensured, and the processability of the coating layer 210 can be improved. Further, since the number average molecular weight of the polyester resin B is 6,000 or less, the polyester resin B easily enters the gaps between the pigments, and the adhesion of the coating layer 210 can be improved. The number average molecular weight of the polyester resin B is more preferably 2,500 or more and 5,000 or less, particularly preferably 3,000 or more and 4,500 or less. Further, when the hydroxyl value of the polyester resin B is 20 or more, the number of crosslinking points increases, so that the adhesion of the coating layer 210 to the undercoat layer 23 can be improved. The hydroxyl value of the polyester resin B is more preferably 30 or more, particularly preferably 40 or more. The upper limit of the hydroxyl value of the polyester resin B is not particularly limited, but is preferably 200 or less, for example.

In the coating paint, the ratio of the mass of polyester resin B to the mass of polyester resin A (polyester resin B/polyester resin A) is preferably 0.25 or more and 4 or less. When this ratio is 0.25 or more, the adhesion of the coating layer 210 can be effectively improved. Moreover, when this ratio is 4 or less, the processability of the coating layer 210 can be effectively improved. The mass ratio of polyester resin A to polyester resin B is more preferably 0.4 or more and 2.5 or less, particularly preferably 0.65 or more and 1.5 or less.

The pigment contained in the coating paint preferably contains rutile titanium oxide. That is, it is preferable that the coating layer 210 contains rutile-type titanium oxide. Since rutile titanium oxide has a higher refractive index than other pigments, it is possible to increase the difference in refractive index between the resin and air contained in the coating layer 210 and rutile titanium oxide. By increasing this refractive index difference, the diffuse reflectance of the coating layer 210 can be increased.

The particles of rutile titanium oxide may be a single particle, or may be particles of rutile titanium oxide coated with silica, alumina, zirconia, zinc oxide, antimony oxide, an organic substance, or the like. Examples of organic substances used for coating include polyols such as pentaerythritol and trimethylolpropane, alkanolamines such as triethanolamine and organic acid salts of trimethylolamine, and silicones such as silicone resins and alkylchlorosilanes. It can be done.

The average particle size of the rutile titanium oxide is preferably 200 nm or more and 400 nm or less. In this case, the reflectance of the coating layer 210 can be improved, and the light that has passed through the photocatalyst layer 3 and reached the coating layer 210 can be easily reflected toward the photocatalyst layer 3. Further, the coating layer 210 can easily reflect light having a wavelength that easily activates the photocatalyst 30 contained in the photocatalyst layer 3 . The average particle size of the rutile titanium oxide is more preferably 250 nm or more and 350 nm or less. Note that the average particle size of the rutile-type titanium oxide is determined by observing the coating layer 210 under 10,000 times magnification using an electron microscope. This is the arithmetic average value of the particle size of the remaining rutile-type titanium oxide after removing 5% from the larger 20%.

In the coating layer 210, the solid volume concentration of rutile titanium oxide is preferably 20% or more. In this case, even if the coating layer 210 is in a close-packed state of rutile-type titanium oxide particles, the volume of the voids between the particles can be made larger than the volume of the resin. Since the refractive index of the void is lower than the refractive index of the pigment and the refractive index of the resin, light is easily reflected at the interface between the pigment and the void and the interface between the resin and the void. Therefore, by providing sufficient voids in the coating layer 210, the diffuse reflectance of the coating layer 210 can be improved. The solid volume concentration of the rutile titanium oxide is more preferably 25% or more. In this case, the diffuse reflectance of the coating layer 210 can be further improved. The solid volume concentration of the rutile titanium oxide is preferably 70% or less, more preferably 65% or less, and particularly preferably 40% or less. In this case, the strength of the coating layer 210 can be ensured, and the coating layer 210 can be prevented from becoming brittle.

The coating paint may contain a component having a larger average particle size and a lower refractive index than rutile titanium oxide (hereinafter also referred to as a low refractive index component). In this case, the voids in the coating layer 210 can be increased, and light can also be reflected at the interface with the rutile-type titanium oxide. Therefore, the diffuse reflectance of the coating layer 210 can be effectively improved. The average particle diameter of the low refractive index component is preferably 1 μm or more and 10 μm or less, more preferably 3 μm or more and 8 μm or less, and more preferably 4 μm or more and 7 μm or less. The refractive index of the low refractive index component is preferably 0.5 or more lower than the refractive index of rutile-type titanium oxide, and more preferably 1 or more lower. The low refractive index component can include, for example, one or more selected from the group consisting of silica, calcium carbonate, barium sulfate, zinc oxide, and resin powders such as acrylic, polyester, and PTFE. The solid volume concentration of the low refractive index component in the coating layer 210 is 9 to 25%, preferably 10 to 17%. In this case, workability and corrosion resistance of the coating layer 210 can be ensured while improving the diffuse reflectance of the coating layer 210.

The ratio of voids in the coating layer 210 is preferably 0.02 times or more and 1.1 times or less, more preferably 0.3 times or more and 1.0 times or less, and 0.5 times the solid volume of the coating layer 210. Particularly preferably 0.95 times or less. In this case, workability and adhesion of the coating layer 210 can be ensured while improving the diffuse reflectance of the coating layer 210. The size of the voids in the coating layer 210 is, for example, 200 nm or more and 400 nm or less, preferably 250 nm or more and 350 nm or less. In this case, the workability and corrosion resistance of the coating layer 210 can be ensured while improving the diffuse reflectance of the coating layer 210. However, since it is difficult to control the size of the voids in the coating layer 210, unless extremely large voids occur or the diffuse reflectance of the coating layer 210 is not particularly affected, the size of the voids in the coating layer 210 may vary. is not particularly limited.

The thickness of the coating layer 210 is preferably 5 μm or more and less than 100 μm. When the thickness of the coating layer 210 is less than 100 μm, it is possible to suppress the coating layer 210 from becoming brittle. From the viewpoint of finished appearance, the thickness is preferably 20 μm to 50 μm, more preferably 25 μm to 35 μm. In this case, the light reflectance of the coating layer 210 can be improved, and the coating layer 210 can be prevented from becoming brittle, and the strength of the coating layer 210 can be ensured. The thickness of the coating layer 210 is more preferably less than 50 μm. In this case, when forming the coating layer 210, it is possible to suppress the occurrence of wrinkles (small bubble-like bulges and holes). Note that the covering layer 210 is not limited to being composed of a single layer, but may be composed of a plurality of layers.

The center average roughness Ra of the interface between the coating layer 210 and the intermediate protective layer 4 is preferably 0.8 μm or more, more preferably 1.1 μm or more, and particularly preferably 1.6 μm or more. In this case, the adhesion between the coating layer 210 and the intermediate protective layer 4 can be improved, and the diffuse reflectance of the coating layer 210 can be improved. The center average roughness Ra of the interface between the coating layer 210 and the intermediate protective layer 4 is preferably 4 μm or more. In this case, the intermediate protective layer 4 and the photocatalyst layer 3 can be easily made flat, and the stain resistance of the photocatalyst layer 3 can be improved. The center average roughness Ra of the interface between the covering layer 210 and the intermediate protective layer 4 can be increased, for example, by the following method.
(a) The coating paint and the paint for forming the intermediate protective layer 4 are laminated in an undried state.
(b) The concentration of the pigment in the covering layer 210 is made higher than the concentration of the pigment in the intermediate protective layer 4.
(c) Adding a pigment with a large average particle size to the coating layer 210.
(d) Reducing the viscosity of the coating paint.
(e) To reduce the difference in surface tension between the coating paint and the paint for forming the intermediate protective layer 4.

(Second example)
The coating layer 210 of the second example is a coating layer with little gloss, and is preferably a matte coating layer. The coating layer 210 of the second example is, for example, a paint containing a resin binder containing a polyester resin and a curing agent, titanium oxide, and organic polymer fine particles with an average particle size of 4 to 9 μm (hereinafter also referred to as the paint of the second example). It can be formed from

As the polyester resin contained in the resin binder, the same component as the polyester resin contained in the undercoat layer 23 of the first embodiment can be used.

As the curing agent contained in the resin binder, the same components as the curing agent contained in the undercoat layer 23 of the first embodiment can be used, such as the above amino resin, the above blocked isocyanate compound, etc. It is preferable. Further, the paint of the second example may contain the same components as the curing catalyst contained in the undercoat layer 23 of the first embodiment in order to accelerate curing.

As the titanium oxide contained in the paint of the second example, the same component as the titanium oxide contained in the undercoat layer 23 of the first embodiment can be used. The content of titanium oxide in the paint of the second example is 100 parts by mass or more and 250 parts by mass or less, and preferably 140 parts by mass or more and 190 parts by mass or less, based on 100 parts by mass of the resin binder component. In this case, the finish, high diffuse reflectance, and adhesion of the second example coating layer 210 can be improved in a well-balanced manner.

As mentioned above, the paint of the second example contains organic polymer fine particles with an average particle size of 4 to 9 μm. Thereby, the coating layer 210 can be made to have low gloss and high diffuse reflectance. Examples of the organic polymer particles include urea resin-based organic polymer particles, which are obtained by pulverizing a resin obtained by a condensation reaction between urea and an aldehyde component, and acrylic resin-based organic polymer particles. The organic polymer fine particles may be hollow.

The average particle diameter of the organic polymer fine particles is 4 μm or more and 9 μm or more, preferably 5 μm or more and 8 μm or less. In this case, the finish quality of the coating layer 210 can be improved while improving the diffuse reflectance of the coating layer 210. Note that the average particle diameter of organic polymer fine particles is the median diameter (d50 ) is the value of

Commercially available organic polymer particles include Pergopack M3 (manufactured by Lonza Japan, trade name), GR-800 (manufactured by Negami Kogyo Co., Ltd., trade name), Techpolymer MBX-5, Techpolymer MBX-8 (Sekisui Chemical Co., Ltd.). Company-made, product name), etc.

The content of the organic polymer fine particles in the paint of the second example is preferably 10 parts by mass or more and 30 parts by mass or less, more preferably 11 parts by mass or more and 20 parts by mass or less, based on 100 parts by mass of the resin binder component.

The thickness of the coating layer 210 of the second example is preferably 20 μm or more and 35 μm or less, more preferably 25 μm or more and 33 μm or less. In this case, the hiding property of the coating layer 210 can be improved, and when applying the paint of the second example, it is easy to apply the paint evenly and uniformly.

The paint of the second example may contain a matting agent such as silica, a solvent, a leveling agent, a surface conditioner, an ultraviolet absorber, a light stabilizer, a pigment dispersant, an anti-wrinkle agent, etc., as necessary. .

Examples of the coating method for the second example of the paint include curtain coating, roll coating, dip coating, and spray coating. When pre-coating the paint of the second example by coil coating or the like, the curtain coating method and roll coating method are recommended from the viewpoint of economy. When applying the roll coating method, the top feed or bottom feed method using three rolls is recommended in order to achieve the best uniformity of the coated surface, but for practical purposes, the bottom feed method using the usual two rolls ( So-called natural reverse painting, natural painting) may also be used.

The curing conditions (baking conditions) for the second example of the paint are, for example, at a maximum temperature reached by the material of 160 to 260° C. for 15 to 90 seconds.

The surface of the base material 2 to which the coating layer 210 of the second example is applied preferably has a 60 degree specular gloss of 5 to 20%, preferably 6 to 15%. In this case, it is easy to obtain highly diffused reflected light. Further, according to the second example of the coating layer 210, it is possible to achieve a diffuse reflectance of 85% or more, preferably 88% or more at a light wavelength of 555 nm.

2-2-2. Photocatalytic action The photocatalytic action exhibited by the coating material 1 according to the second embodiment will be described with reference to FIG. 4.

Similar to the coating material 1 according to the first embodiment, the coating material 1 of this embodiment has a reflectance of 85% or more for light at a wavelength of 555 nm of the coating layer 210, so that the photocatalyst layer 3 is directly irradiated. Not only light, but also light that has passed through the photocatalyst layer 3 and was reflected by the coating layer 210 can reach the photocatalyst 30. Therefore, light can be efficiently made to reach the photocatalyst 30, and the photocatalytic action of the photocatalyst 30 can be efficiently expressed.

Furthermore, in the coating material 1 of the present embodiment, since the coating layer 210 has a diffuse reflectance of 85% or more for light with a wavelength of 555 nm, the light that has passed through the photocatalyst layer 3 and reached the coating layer 210 is transferred to the photocatalyst layer 210. can be diffused over a wide range (see Figure 4). Therefore, light can be made to reach the photocatalyst 30 particularly efficiently, and the photocatalytic action of the photocatalyst 30 can be expressed particularly efficiently. Thereby, a particularly high photocatalytic effect can be exhibited from the initial stage when the photocatalytic layer 3 is irradiated with light, and this photocatalytic effect can be maintained particularly over a long period of time.

Of course, the photocatalytic action expressed by the coating material 1 of this embodiment also includes hydrophilic action, antifouling action, bacteria or virus inactivation action, and the like. In the coating material 1 of the present embodiment, even in the initial stage of irradiating the photocatalytic layer 3 with light, the inactivation effect of bacteria or viruses can be expressed particularly efficiently, and this inactivation effect can be maintained for a long period of time. can.

3. Method for inactivating bacteria or viruses As described above, by using the covering material 1 of the first embodiment and the second embodiment, bacteria or viruses can be inactivated.

Therefore, in the method for inactivating bacteria or viruses, the photocatalyst layer 3 of the above-mentioned coating material 1 is irradiated with light to activate the photocatalyst 30 and inactivate the bacteria or viruses. More specifically, by irradiating the photocatalyst layer 3 with light from a light source such as sunlight, a fluorescent lamp, an LED lamp, etc., the photocatalyst 30 becomes excited, and active oxygen having strong oxidizing power is generated on the surface of the photocatalyst layer 3. occurs. This active oxygen decomposes bacteria, viruses, etc., thereby inactivating the bacteria or virus. Furthermore, since active oxygen can decompose organic matter, it can also exhibit antifouling effects.

Bacteria and viruses that can be inactivated by the photocatalytic action of the coating material 1 include blue mold (Penicillium pinohilum), Fusarium, Staphylococcus aureus, influenza A virus, feline cacilli virus, norovirus, Bacillus anyabhattai, Aeromicrobium sp, Marmorico sp, Includes Bacillus sp. Of course, bacteria and viruses that can be inactivated by the photocatalytic action of the coating material 1 include bacteria and viruses other than those mentioned above.

The coating material 1 exhibits the effect of inactivating bacteria or viruses from the initial stage when the photocatalyst layer 3 is irradiated with light. For example, the following indicators can be considered as indicators that the inactivation effect of bacteria or viruses is expressed from the initial stage when the photocatalyst layer 3 is irradiated with light.

As mentioned above, the action of inactivating bacteria or viruses is exerted by active oxygen generated on the surface of the photocatalyst layer 3. Since this active oxygen can decompose not only bacteria or viruses but also organic substances such as methylene blue, the decomposition ability of methylene blue can be used as an indicator of the inactivation effect of bacteria or viruses. Therefore, if the resolution of methylene blue is high at the initial stage when the photocatalytic layer 3 is irradiated with light, it can be considered that the inactivation effect of bacteria or viruses is expressed from the initial stage when the photocatalytic layer 3 is irradiated with light. .

The resolution of methylene blue can be measured, for example, by the following method. First, a dry coating film containing methylene blue at an arbitrary concentration and having an arbitrary thickness is provided on the photocatalyst layer 3. Next, the photocatalyst layer 3 is irradiated with a UV lamp at an arbitrary illumination intensity and for an arbitrary time. When methylene blue is decomposed by the photocatalytic effect, the color of the dried paint film changes, so the resolution of methylene blue can be measured based on the color difference ΔE of the dry paint film before and after UV lamp irradiation. Note that the method for measuring the color difference ΔE is not particularly limited, but it can be measured using, for example, a spectrophotometric system (product number CM-3700d) manufactured by Konica Minolta, Inc.

In the coating material 1 of the first embodiment and the second embodiment, a dry coating film of methylene blue diluted 100 times (adhesion amount 44.4 mg/m ² ) is provided on the photocatalyst layer 3, and the dry coating film is 10.0±0. When irradiated with ultraviolet rays at an irradiation intensity of 5 W/m ² for 1 hour, the percentage ratio of the color difference (ΔE) of the dry paint film after irradiation to the color difference (ΔE ₀ ) of the dry paint film before irradiation is 30% or more. It is preferable.

In particular, in the coating material 1 of the second embodiment, a dry coating film of methylene blue diluted 100 times (adhesion amount 44.4 mg/m ² ) was provided on the photocatalyst layer 3, and ultraviolet rays were applied at 10.0±0.5 W. When irradiated for 1 hour at an illumination intensity of /m ² , the percentage ratio of the color difference (ΔE) of the dry paint film after UV irradiation to the color difference (ΔE ₀ ) of the dry paint film before UV irradiation is preferably 40% or more. .

Further, in the coating material 1 of the first embodiment and the second embodiment, a dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² is provided on the photocatalyst layer 3, and a coating amount of 0.0±0.5 W/m ² is applied. When ultraviolet rays are irradiated for 11 hours at the irradiation intensity, the percentage ratio of the color difference (ΔE) of the dry paint film after irradiation to the color difference (ΔE ₀ ) of the dry paint film before irradiation increases by 6% or more per hour. is preferred.

Further, in the coating material 1 of the first embodiment and the second embodiment, a dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² is provided on the photocatalyst layer 3, and a coating amount of 0.0±0.5 W/m ² is applied. When irradiated with ultraviolet rays at the irradiation intensity for 11 hours, the percentage ratio of the color difference (ΔE) of the dry paint film after irradiation to the color difference (ΔE ₀ ) of the dry paint film before irradiation is preferably 60% or more, More preferably, it is 70% or more.

Hereinafter, the present invention will be specifically explained with reference to Examples.

(Examples 1 and 2 and Comparative Examples 1 and 2)
First, a 55% AL-Zn hot-dip plated steel plate was prepared as a base material.

Next, the undercoat paint shown in Table 1 below was applied onto the surface of the base material to form a coating film, and then heated at 220° C. for about 1 minute to form the undercoat layer 23. The coating amount of the undercoat was 12.5 μm in dry film thickness.

Next, the coating paint shown in Table 1 below was applied onto the undercoat layer 23 to form a coating film, and then heated at 220° C. for about 1 minute to form a coating layer. The coating amount of the coating paint was 27.5 μm in dry film thickness. The reflectance and diffuse reflectance of the surface of the coating layer for light at a wavelength of 555 nm were the values shown in Table 1 below. The reflectance and diffuse reflectance of the coating layer were measured using a spectrophotometer (CM-3700d) manufactured by Konica Minolta.

Next, a coating for a protective layer shown in Table 1 below was applied onto the undercoat layer 23 to form a coating film, and then heated at 200° C. for about 1 minute to form an intermediate protective layer. The coating amount of the coating for the protective layer was 1.0 μm in dry film thickness.

Next, a photocatalyst coating shown in Table 1 below was applied onto the intermediate protective layer to form a coating film, and then heated at 220° C. for about 1 minute to form a photocatalyst layer. The amount of photocatalytic paint applied was 1.0 μm in dry film thickness. A covering material was produced through the above steps.

The details of the paints shown in Table 1 below are as follows.
・KPP-76: Primer paint (product number KPP-76) manufactured by Kansai Paint Co., Ltd. Contains a resin binder and a titanium oxide pigment.
・KP-217: White paint (product number KP-217) manufactured by Kansai Paint Co., Ltd.
・KP-217 + organic polymer fine particles: A mixture of white paint (product number KP-217) manufactured by Kansai Paint Co., Ltd. and acrylic resin beads (particle size 5 μm), adjusted so that the gloss level after application and drying is 10. painted paint.
・MX-110F: White paint (product number MX-110F) manufactured by Akzo Nobel Coating Co., Ltd.
・VCT-02BSLB: Protective paint manufactured by Toyotsu Vtex Co., Ltd. Contains a raw material component containing alkoxysilane and a substance having photocatalytic activity.
・VCTII-02BSLC: Protective paint manufactured by Toyotsu Vtex Co., Ltd. Contains a raw material component containing alkoxysilane and a substance that has photocatalytic activity in the visible light region.

(evaluation)
1. Resolution of methylene blue The coating materials of Examples 1 and 2 and Comparative Examples 1 and 2 were irradiated with sunlight for 6 hours, and the coating materials of Examples 1 and 2 and Comparative Example 1 were The photocatalyst layer was brought into an excited state. Next, methylene blue diluted 100 times with pure water was applied onto the surface of each coating material and dried to form a dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² . Next, each coating material was irradiated with ultraviolet light. The irradiation intensity of ultraviolet rays was 10.0±0.5 W/m ² . After starting the ultraviolet irradiation, the color difference of each coating material was measured at regular intervals, and the percentage of the initial color difference ΔE0 was determined. The results are shown in Table 2 and FIG. 5 below.

According to Table 2 and FIG. 5, the coating material of Comparative Example 1 has a larger percentage of color difference ΔE than the coating material of Comparative Example 2. This is thought to be because the coating material of Comparative Example 2 does not have a photocatalyst layer and is difficult to decompose methylene blue. Furthermore, the coating materials of Examples 1 and 2 have a larger percentage of color difference ΔE than the coating material of Comparative Example 1, and in particular, the percentage of ΔE from the initial stage of ultraviolet irradiation is larger. This is thought to be because the coating materials of Examples 1 and 2 have a coating layer with a high reflectance in addition to the photocatalytic layer, so that the photocatalytic effect can be efficiently exhibited from the initial stage of ultraviolet irradiation. Further, the coating material of Example 1 has a larger percentage of color difference ΔE than the coating material of Example 2 at 11 hours and 21 hours after irradiation with ultraviolet rays. This is considered to be because the coating layer of Example 1 has a higher diffuse reflectance than the coating layer of Example 2, and can exhibit the photocatalytic effect particularly efficiently.

2. Inactivation effect on bacteria, mold, and viruses The inactivation effect on bacteria, mold, and viruses was measured for the coating material of Example 1, which has particularly excellent methylene blue resolution, and Comparative Example 1, which has a lower methylene blue resolution than Example 1. did. Regarding Comparative Example 2, which does not have the ability to decompose methylene blue because it does not have a photocolor catalyst layer, the inactivation effect on some bacteria, mold, and viruses was also measured. The results are shown below.

(A) Molds and fungi Bacteria and fungi shown in Table 3 below were placed on the surfaces of the coating materials of Example 1 and Comparative Examples 1 and 2. Next, using a fluorescent lamp with an illuminance of 1000 lx, each coating material was irradiated with fluorescent lamp light for 24 hours through a UV cut filter. Then, the reduction rate was calculated from the number of viable bacteria before irradiation with light and the number of viable bacteria after irradiation. The results are shown in Table 3 below.

According to Table 3, the coating material of Comparative Example 1 has a larger reduction rate in viable bacteria count than the coating material of Comparative Example 2. This is thought to be because the coating material of Comparative Example 1 has a photocatalytic layer, and thus the number of molds or bacteria can be reduced by the photocatalytic effect. Further, the coating material of Example 1 has a larger reduction rate in the number of viable bacteria than the coating materials of Comparative Examples 1 and 2. This is because the coating material of Example 1 has a coating layer with high reflectance and diffuse reflectance in addition to the photocatalytic layer, so it can efficiently exhibit the photocatalytic effect from the initial stage of ultraviolet irradiation, and the photocatalytic effect can be maintained for a long period of time. This is thought to be because it can be maintained.

(a) Influenza A virus Influenza A virus was placed on the surface of the coating materials of Example 1 and Comparative Examples 1 and 2. Next, using a fluorescent lamp with an illuminance of 3000 lx, each coating material was irradiated with fluorescent lamp light for 8 hours through a UV cut filter. Then, the ratio of the number of live viruses 4 hours after the start of irradiation to the number of live viruses before irradiation and the ratio of the number of live viruses 8 hours after the start of irradiation were calculated. The results are shown in Table 4 below.

According to Table 4, the coating material of Comparative Example 1 has a smaller ratio of the number of live viruses than the coating material of Comparative Example 2. This is thought to be because the coating material of Comparative Example 1 has a photocatalytic layer, and the number of viruses can be reduced by the photocatalytic effect. Furthermore, the coating material of Example 1 has a smaller ratio of the number of live viruses than the coating materials of Comparative Examples 1 and 2. This is because the coating material of Example 1 has a coating layer with high reflectance and diffuse reflectance in addition to the photocatalytic layer, so the photocatalytic effect is efficiently exhibited from the initial stage of ultraviolet irradiation, and this photocatalytic effect is maintained for a long time. This is thought to be because it is maintained for a long period of time.

(C) Feline Kasiri Virus Feline Kasirivirus was placed on the surface of the coating materials of Example 1 and Comparative Examples 1 and 2. Next, using a fluorescent lamp with an illuminance of 3000 lx, each coating material was irradiated with fluorescent lamp light for 8 hours through a UV cut filter. Then, the ratio of the number of live viruses 8 hours after the start of irradiation to the number of live viruses before irradiation with light was calculated. The results are shown in Table 5 below.

According to Table 5, the coating material of Comparative Example 1 has a smaller ratio of the number of live viruses than the coating material of Comparative Example 2. This is thought to be because the coating material of Comparative Example 1 has a photocatalytic layer, and the number of viruses can be reduced by the photocatalytic effect. Furthermore, the coating material of Example 1 has a smaller ratio of the number of live viruses than the coating materials of Comparative Examples 1 and 2. This is because the coating material of Example 1 has a coating layer with high reflectance and diffuse reflectance in addition to the photocatalytic layer, so the photocatalytic effect is efficiently exhibited from the initial stage of ultraviolet irradiation, and this photocatalytic effect is maintained for a long time. This is thought to be because it is maintained for a long period of time.

(d) Bacteria collected from soil On the surface of the coating materials of Example 1 and Comparative Example 1, four types of bacteria (Bacillus anyabhattai, Aeromicrobium sp, Marmorico sp, Bacillus sp) collected from soil were placed. Next, using a fluorescent lamp with an illuminance of 1000 lx, each coating material was irradiated with fluorescent light for 16 hours through a UV cut filter. Then, the reduction rate was calculated from the number of viable bacteria before irradiation with light and the number of viable bacteria after irradiation. The results are shown in Table 6 below.

According to Table 6, in the coating material of Example 1, the rate of decrease in the number of all viable bacteria was large, and the rate of decrease in the number of viable bacteria of Aeromicrobium sp, Marmorico sp, and Bacillus sp was particularly large. This is considered to be because the coating material of Example 1 has high reflectance and diffuse reflectance, so the photocatalytic effect is efficiently exhibited from the initial stage of ultraviolet irradiation, and this photocatalytic effect is maintained for a long period of time.

1 Coating material 2 Base material 21 Coating layer 22 Plated steel plate 3 Photocatalyst layer 4 Intermediate protective layer

Claims (7)

A base material in which at least a part of the surface is constituted by a coating layer having a reflectance of 85% or more for light with a wavelength of 555 nm and a diffuse reflectance of 85% or more for light with a wavelength of 555 nm, and the coating layer a photocatalytic layer located above;
The coating layer includes a binder resin and a pigment, and the binder resin includes a polyester resin having a number average molecular weight of 19,000 or more and 28,000 or less,
The photocatalyst layer contains at least one of silicon oxide and siloxane polymer,
A dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² was provided on the photocatalyst layer, and the dried coating film was irradiated with ultraviolet rays at an irradiation intensity of 10.0±0.5 W/m ² for 11 hours. In this case, the percentage ratio of the color difference (ΔE) of the dry paint film after irradiation with the ultraviolet rays to the color difference (ΔE ₀ ) of the dry paint film before irradiation with the ultraviolet rays increases by 6% or more per hour on average. do,
Covering material. A base material in which at least a part of the surface is constituted by a coating layer having a reflectance of 85% or more for light with a wavelength of 555 nm and a diffuse reflectance of 85% or more for light with a wavelength of 555 nm, and the coating layer a photocatalytic layer located above;
The coating layer includes a binder resin and a pigment, and the binder resin includes a polyester resin having a number average molecular weight of 19,000 or more and 28,000 or less,
The photocatalyst layer contains at least one of silicon oxide and siloxane polymer,
A dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² was provided on the photocatalyst layer, and the dried coating film was irradiated with ultraviolet rays at an irradiation intensity of 10.0±0.5 W/m ² for 1 hour. In this case, the percentage ratio of the color difference (ΔE) of the dry coating film after irradiation with the ultraviolet rays for 1 hour to the color difference (ΔE ₀ ) of the dry coating film before irradiation with the ultraviolet rays is 30% or more.
Covering material. A base material in which at least a part of the surface is constituted by a coating layer having a reflectance of 85% or more for light with a wavelength of 555 nm and a diffuse reflectance of 85% or more for light with a wavelength of 555 nm, and the coating layer a photocatalytic layer located above;
The coating layer includes a binder resin and a pigment, and the binder resin includes a polyester resin having a number average molecular weight of 19,000 or more and 28,000 or less,
The photocatalyst layer contains at least one of silicon oxide and siloxane polymer,
A dry coating film of methylene blue with an adhesion amount of 44.4 mg/m ² was provided on the photocatalyst layer, and the dried coating film was irradiated with ultraviolet rays at an irradiation intensity of 10.0±0.5 W/m ² for 11 hours. In this case, the percentage ratio of the color difference (ΔE) of the dry coating film after irradiation with the ultraviolet rays for 11 hours to the color difference (ΔE ₀ ) of the dry coating film before irradiation with the ultraviolet rays is 60% or more.
Covering material. the coating layer contains rutile titanium oxide,
The coating material according to any one of claims 1 to 3. an intermediate protective layer provided between the coating layer and the photocatalyst layer;
The covering material according to any one of claims 1 to 4. The base material includes a plated steel plate and the coating layer provided on the plated steel plate,
The coating material according to any one of claims 1 to 5. By irradiating the photocatalyst layer of the coating material according to any one of claims 1 to 6 with light, the photocatalyst is activated and bacteria or viruses are inactivated.
Method for inactivating bacteria or viruses.

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