Photocatalytically active component and method for manufacturing the same

Abstract

To provide a method for producing a member having photocatalytic activity in which fine particles having photocatalytic activity can be fixed on a substrate in a better condition than conventional methods, and excellent photocatalytic activity can be imparted.SOLUTION: A method for producing a member having photocatalytic activity includes: an oxidation treatment step of performing an oxidation treatment to a surface of a substrate formed of titanium, a titanium alloy, a titanium compound or metal containing a titanium compound to form titanium oxide coating on the substrate; and a carrying treatment step of bringing mixture liquid containing solvent, fine particles having photocatalytic activity, and a degradable titanium compound into contact with the titanium oxide coating under a condition that the degradable titanium is degraded, and making the titanium oxide coating carry the fine particles via a decomposed product derived from the degradable titanium compound.SELECTED DRAWING: None

Description

Technical Field

[0001] The present invention relates to a member having photocatalytic activity and a method for manufacturing the same.

Background Art

[0002] Photocatalysts are known to exhibit a strong oxidative decomposition function when irradiated with light of a predetermined wavelength, and to oxidize and decompose substances adhering to the surface of a member having a surface layer containing a photocatalyst. Utilizing such a photocatalytic function, studies have been conducted on deodorization, sterilization, antibacterial action, decomposition of environmental pollutants contained in water, air, etc., and making the surface hydrophilic to prevent the adhesion of dirt, water droplets, etc.

[0003] Conventionally, various methods have been proposed for imparting such a photocatalytic function to the surface of a substrate to manufacture a member having photocatalytic activity. Among these, for example, in Patent Document 1, when manufacturing a photocatalytic material in which a titanium oxide layer is coated on the surface of a substrate, as a method for making the titanium oxide present in the surface layer portion having a thickness of 10 nm from the surface of the titanium oxide layer into a highly photocatalytic anatase-type crystal, a method has been proposed in which a titanium substrate is used, an anodic oxidation treatment is performed on the surface of the substrate, and then an organic titanium is applied to the surface and fired to generate titanium oxide. This method is said to eliminate the respective drawbacks of the conventional methods of fixing titanium oxide powder to a substrate with a Si-based binder, the conventional method of performing only anodic oxidation treatment on a titanium substrate, and the conventional method of performing only the treatment of applying an organic titanium to a titanium substrate and firing to generate titanium oxide, and to be able to firmly form a titanium oxide layer having high photocatalytic activity on the substrate.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] However, the inventors have found that even when employing the method described in Patent Document 1, there is room for improvement in terms of enhancing photocatalytic activity.

[0006] Therefore, the object of the present invention is to provide a method for producing a photocatalytically active member that can impart better photocatalytic activity to a substrate than conventional methods, and to provide a member having better photocatalytic activity than conventional methods. [Means for solving the problem]

[0007] The inventors diligently conducted research to solve the aforementioned problems. As a result, they found that by using a mixed solution containing a solvent, photocatalytically active fine particles, and a degradable titanium compound, and contacting this with a substrate on which a titanium oxide film has been formed by oxidation treatment under conditions in which the degradable titanium compound decomposes, a component with good photocatalytic activity can be obtained, thus completing the present invention. The gist of the present invention is as follows.

[0008] (1) An oxidation treatment step in which an oxidation treatment is performed on the surface of a substrate made of titanium, a titanium alloy, a titanium compound, or a metal containing a titanium compound to form a titanium oxide film on the substrate, A method for producing a photocatalytically active member, comprising a supporting step of contacting a titanium oxide film with a mixed solution containing a solvent, photocatalytically active fine particles, and a degradable titanium compound, under conditions in which the degradable titanium compound decomposes, thereby supporting the fine particles on the titanium oxide film via decomposition products derived from the degradable titanium compound. (2) A method for producing a photocatalytically active member as described in item (1) above, further comprising a baking step of heating the solvent to a point above the boiling point after the supporting step. (3) A method for producing a photocatalytically active member according to paragraph (1) or (2) above, wherein the decomposable titanium compound is at least one selected from titanium halides and titanium alkoxides. (4) A method for producing a photocatalytically active member according to any one of the preceding paragraphs (1) to (3), wherein in the loading process, the titanium oxide film is heated to a temperature between the boiling point of the solvent and 800°C. (5) A method for manufacturing a photocatalytically active member according to any one of the preceding paragraphs (1) to (4), wherein the surface of the substrate is formed of titanium and the titanium is subjected to an oxidation treatment. (6) A method for producing a photocatalytically active component according to any one of the preceding paragraphs (1) to (5), wherein the photocatalytically active fine particles are titanium dioxide fine particles.

[0009] (7) A photocatalytically active component obtained by the manufacturing method described in any one of the preceding paragraphs (1) to (6). (8) A base material formed of titanium, a titanium alloy, a titanium compound, or a metal containing a titanium compound, A titanium oxide coating formed on the surface layer of the substrate, A photocatalytically active member comprising: a titanium oxide coating with photocatalytically active fine particles supported on it via decomposition products of a degradable titanium compound. (9) A member having photocatalytic activity as described in item (7) or (8) above, wherein the contact angle with water on the surface is less than 80°. [Effects of the Invention]

[0010] According to the present invention, it is possible to provide a method for producing a photocatalytically active member that can impart better photocatalytic activity to a substrate than conventional methods. Furthermore, according to the present invention, it is possible to provide a member having better photocatalytic activity than conventional methods. [Brief explanation of the drawing]

[0011] [Figure 1] This figure shows electron microscope images of the surface of the photocatalytically active member from Example 1. [Figure 2] (a) This is an enlarged view showing an electron microscope image of the surface of the photocatalytically active member of Example 1. (b) This is an enlarged view of the image within the rectangular frame in Figure 2(a). [Figure 3]It is a figure showing an electron microscope image of a cross-section of a substrate on which a titanium oxide film of Comparative Example 1 is formed. [Figure 4] It is a figure showing an electron microscope image of the surface of a substrate on which a titanium oxide film of Comparative Example 1 is formed. [Figure 5] It is a figure showing the measurement result of X-ray diffraction of a cross-section of a substrate on which a titanium oxide film of Comparative Example 1 is formed. [Figure 6] It is a figure showing the measurement result of X-ray diffraction of a cross-section of the member of Example 1. [Figure 7] It is a figure showing the change over time of the concentration of acetaldehyde in an acrylic case in an aldehyde odor test conducted using the test pieces of Example 1 and Comparative Examples 1 and 2.

Mode for Carrying Out the Invention

[0012] The manufacturing method of a member having photocatalytic activity according to an embodiment of the present invention (hereinafter, may be referred to as a "photocatalytic member") includes the following steps. An oxidation treatment step of performing an oxidation treatment on the surface of a substrate formed of titanium, a titanium alloy, a titanium compound, or a metal containing a titanium compound to form a titanium oxide film on the substrate. A support treatment step of bringing a mixed liquid containing a solvent, fine particles having photocatalytic activity (hereinafter, may be referred to as "photocatalytic fine particles"), and a decomposable titanium compound into contact with the titanium oxide film under conditions where the decomposable titanium compound decomposes, and supporting the fine particles on the titanium oxide film through a decomposition product derived from the decomposable titanium compound.

[0013] It is believed that by including such a process, an oxidation treatment is performed on a substrate formed of a metal or compound containing titanium atoms to form a titanium oxide film, and then a predetermined mixed solution is applied to this titanium oxide film under predetermined conditions to securely support photocatalytic fine particles to the titanium oxide film via decomposition products derived from the decomposable titanium compound while maintaining their activity. In this process, the decomposable titanium compound is decomposed as a result of the predetermined treatment, and it is believed that, for example, the photocatalytic particles and the titanium oxide film are supported via decomposition products derived from the decomposable titanium compound. Examples of decomposition products derived from the decomposable titanium compound generated in this process include titanium oxide.

[0014] As the substrate to be subjected to the acid treatment process, those formed of titanium, titanium alloy, titanium compound, or a metal containing a titanium compound are used. That is, the substrate is made of pure titanium, titanium alloy, titanium compound, or a metal containing a titanium compound. As pure titanium or titanium alloy, for example, various ones defined by JIS, ASTM, etc. can be used. As pure titanium, for example, commercially available ones such as industrial pure titanium of JIS grades 1 to 4 can be mentioned. As titanium alloy, for example, corrosion-resistant alloys, α alloys, Near α alloys, α-β alloys, Near β alloys, β alloys, etc. can be used. As corrosion-resistant alloys, for example, JIS grades 11 to 23, etc., as α alloys, for example, JIS grade 50, etc., as α-β alloys, for example, JIS grades 60, 60E, 61, 61F, etc., as β alloys, for example, JIS grade 80, etc. can be mentioned. Also, as metal elements other than Ti constituting the titanium alloy, for example, Al, V, Pd, Ru, Cr, Ta, Ni, Mo, Sn, Si, Fe, Zr, Nb, etc. can be mentioned. Applicable titanium alloys include, for example, Ti-Al-based, Ti-Al-Sn-based, Ti-Al-V-based alloys, etc. As titanium compounds, for example, titanium nitride, titanium carbide, titanium oxide, etc. can be mentioned. As metals containing a titanium compound, for example, metals containing titanium compounds such as titanium nitride, titanium carbide, titanium oxide, etc. can be mentioned. When the substrate is a metal containing a titanium compound, examples include those in which the titanium compound exists in a dispersed state in the metal serving as the base material, and those in which the titanium compound is unevenly distributed on the surface layer of the substrate when it is used as the substrate. Also, the metal serving as the base material can be appropriately selected according to the acid treatment.

[0015] The form of the substrate is not particularly limited and can be appropriately determined according to the use of the photocatalytic active member, etc.

[0016] The oxidation treatment is not particularly limited as long as it can form a titanium oxide film on the surface of the substrate, and can be appropriately selected depending on the material of the substrate. Examples of such oxidation treatments include an anodizing treatment in which a substrate made of titanium, titanium alloy, titanium compound, or a metal containing a titanium compound on its surface is anodic oxidized to form a titanium oxide film on the substrate surface, and a treatment in which the base metal is dissolved by oxidation treatment in a substrate made of a metal containing titanium oxide, and the remaining titanium oxide forms a titanium oxide film on the substrate surface. Among such oxidation treatments, anodizing treatment is preferred from the viewpoint of forming a porous titanium oxide film with a desired thickness.

[0017] The conditions for anodizing can be determined according to standard methods, taking into consideration the material of the substrate, the crystalline phase of the titanium oxide film to be formed, the film thickness, etc. It is preferable to perform degreasing and, if an oxide film is formed on the substrate surface, remove it as a pretreatment before anodizing. Examples of degreasing treatments include contact with an alkaline solution, such as an aqueous sodium hydroxide solution, adjusted to a predetermined temperature, for a predetermined time. The conditions for degreasing can be determined according to standard methods. There are no particular limitations on the treatment for removing the oxide film from the substrate surface; examples include chemical polishing, mechanical treatment such as shot blasting, and / or physical polishing followed by acid cleaning. From the viewpoint of ease of treatment, chemical polishing is preferred. Chemical polishing can be performed, for example, by immersing the substrate in an acidic solution at a predetermined temperature for a predetermined time. The conditions for chemical polishing can be appropriately determined according to the material of the substrate, etc. Furthermore, after anodizing, it is preferable to wash with water, perform dematting, and then wash with pure water and dry.

[0018] Furthermore, a process in which the base metal is dissolved by oxidation treatment on a substrate made of a metal containing titanium oxide, and a titanium oxide film is formed on the substrate surface using the remaining titanium oxide, can be performed in the same manner as the anodic oxidation treatment described above.

[0019] The thickness of the titanium oxide film formed on the surface of the substrate after oxidation treatment is preferably 0.3 to 10 μm, and more preferably 0.3 to 5 μm, from the viewpoint of fixing decomposition products derived from degradable titanium compounds to the titanium oxide film. The size of the porous pores is not particularly limited and can be, for example, 50 to 800 nm.

[0020] When anodizing is performed as an oxidation treatment, X-ray diffraction analysis confirms that the formed titanium oxide film tends to contain a large amount of rutile-type crystal structure. Furthermore, screening the crystal phase with a laser Raman microscope confirms that the rutile-type is more abundant in the outer part of the titanium oxide film, while the anatase-type is more abundant closer to the substrate. In other words, titanium oxide films subjected only to anodizing tend to have low photocatalytic activity because they have fewer anatase-type crystals, which have high photocatalytic activity, and a large amount of rutile-type crystals, which have low photocatalytic activity, are distributed on the outer side where light is incident. Therefore, by performing the following loading treatment process and applying a mixture containing photocatalytic nanoparticles and a degradable titanium compound to the titanium oxide film, the photocatalytic nanoparticles are loaded onto the titanium oxide film via decomposition products derived from the degradable titanium compound, making it possible to provide a photocatalytic component with good photocatalytic activity.

[0021] The mixed solution used in the support process contains a solvent, photocatalytic fine particles, and a degradable titanium compound.

[0022] There are no particular limitations on the solvent; either a water-soluble organic solvent or a water-insoluble organic solvent may be used. Examples of water-soluble organic solvents include alkyl alcohols such as methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropyl alcohol, n-butyl alcohol, sec-butyl alcohol, tert-butyl alcohol, isobutyl alcohol, and n-pentanol; monohydric alcohols such as 3-methoxy-3-methyl-1-butanol, 3-methoxy-1-propanol, 1-methoxy-2-propanol, and 3-methoxy-n-butanol; amides such as 1-dimethylformamide, dimethylacetamide, 3-methoxypropanamide, 3-butoxypropanamide, N,N-dimethyl-3-methoxypropanamide, N,N-dibutyl-3-methoxypropanamide, N,N-dibutyl-3-butoxypropanamide, and N,N-dimethyl-3-butoxypropanamide; ketones or keto alcohols such as acetone and diacetone alcohol; ethers such as tetrahydrofuran and dioxane; and polyethylene glycol and polypropylene glycol. Oxyethylene or oxypropylene copolymers such as ethylene glycol, propylene glycol, diethylene glycol, dipropylene glycol, 1,3-propanediol, isobutylene glycol, triethylene glycol, tripropylene glycol, tetraethylene glycol, 1,3-propanediol, 2-methyl-1,2-propanediol, 2-methyl-1,2-propanediol, 1,2-butanediol, 1,3-butanediol, 1,4-butanediol Diols such as 1,2-pentanediol, 1,2-hexanediol, 1,5-pentanediol, 1,6-hexanediol, 2-methyl-2,4-pentanediol, 3-methyl-1,3-butanediol, 3-methyl-1,5-pentanediol, and 2-methyl-2,4-pentanediol; triols such as glycerin, trimethylolethane, trimethylolpropane, and 1,2,6-hexanetriol; and tetrahydric alcohols such as mesoerythritol and pentaerythritol.Monoalkyl ethers such as ethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, diethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl, n-hexyl, 2-ethylhexyl) ether, triethylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl) ether, propylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl) ether, and dipropylene glycol monomethyl (or ethyl, isopropyl, n-butyl, isobutyl) ether; diethylene glycol dimethyl ether, diethylene glycol diethyl ether, diethylene glycol ethyl methyl ether, triethylene glycol dimethyl ether, triethylene glycol Examples include dialkyl ethers of polyhydric alcohols such as cellulose diethyl ether, tetraethylene glycol dimethyl ether, tetraethylene glycol diethyl ether, propylene glycol dimethyl ether, propylene glycol diethyl ether, dipropylene glycol dimethyl ether, and dipropylene glycol diethyl ether; alkanolamines such as monoethanolamine, diethanolamine, triethanolamine, N-methylethanolamine, N-ethylethanolamine, N-butylethanolamine, N-methyldiethanolamine, N-ethyldiethanolamine, and N-butyldiethanolamine; nitrogen-containing heterocyclic compounds such as N-methyl-2-pyrrolidone, 2-pyrrolidone, and 1,3-dimethyl-2-imidazolidinone; and cyclic compounds such as γ-butyrolactone and sulfolane. These may be used individually or in combination of two or more.

[0023] Of these water-soluble organic solvents, alkyl alcohols are preferred from the viewpoint of ease of removal of the water-soluble organic solvent by heating, and alkyl alcohols having 1 to 5 carbon atoms are preferred.

[0024] Examples of non-water-soluble organic solvents include saturated hydrocarbons such as butane, pentane, hexane, heptane, cyclopentane, cyclohexane, methylcyclohexane, dimethylcyclohexane, trimethylcyclohexane, ethylcyclohexane, diethylcyclohexane, decahydronaphthalene, bicycloheptane, tricyclodecane, hexahydroindencyclohexane, and cyclooctane; unsaturated hydrocarbons such as 1-butene, 2-butene, 1-pentene, and 2-pentene; aromatic hydrocarbons such as benzene, toluene, and xylene; nitrogen-containing hydrocarbons such as nitromethane, nitrobenzene, acetonitrile, dimethylformamide, and N-methylpyrrolidone; ethers such as diethyl ether and tetrahydrofuran; and halogen-containing hydrocarbons such as chloroform, dichloromethane, chlorobenzene, and dichlorobenzene. These may be used individually or in combination of two or more.

[0025] The material constituting the photocatalytic nanoparticles is not particularly limited, and examples include titanium dioxide, zinc oxide, tin oxide, zirconium oxide, tungsten oxide, chromium oxide, molybdenum oxide, iron oxide, nickel oxide, ruthenium oxide, cobalt oxide, copper oxide, manganese oxide, etc. These may be used individually or in combination of two or more. Of these, titanium dioxide is preferred, and anatase-type titanium dioxide is particularly preferred. Commercially available photocatalytic particles can be used.

[0026] The average particle size of the photocatalytic nanoparticles is preferably 5 to 100 nm, and more preferably 5 to 20 nm, from the viewpoint of ensuring surface area. In other words, it is preferable that they are nanoparticles. Furthermore, the specific surface area is preferably 40 m² from the viewpoint of photocatalytic activity. 2 Preferably 150m / g or more 2 More preferably 250m / g or more, 2 A value of 1 / g or higher is even more preferable. The specific surface area can be measured, for example, by the BET method.

[0027] Degradable titanium compounds are compounds that contain titanium atoms and can be degraded by external action. External action refers to heating, light irradiation, and the addition of reactive compounds such as ozone. It is presumed that such external action generates decomposition products containing titanium atoms and decomposition products that do not contain titanium atoms, and that the decomposition products containing titanium atoms act to bond the titanium oxide film formed on the surface of the substrate with the photocatalytic nanoparticles, thereby fixing both together well. The decomposition products containing titanium atoms may be titanium oxide that is bonded to both the titanium oxide film and the photocatalytic nanoparticles. Furthermore, the form of this titanium oxide may be particles, particularly porous particles. In addition, the size of these particles is generally larger than that of the photocatalytic nanoparticles in average particle size, and many may be approximately 100 times or more larger than that of the photocatalytic nanoparticles. Since titanium oxide, which is a decomposition product derived from degradable titanium compounds, generally forms particles larger than those of the photocatalytic nanoparticles, it has been confirmed that when photocatalytic nanoparticles are not used, the photocatalytic activity of the final photocatalytic material is lower than when photocatalytic nanoparticles are supported.

[0028] Examples of degradable titanium compounds include hydrolyzable titanium compounds such as titanium halides, titanium alkoxides, and titanium chelate compounds, as well as peroxotitanic acid and its salts. These may be used individually or in combination of two or more. Such degradable titanium compounds can be those described in, for example, Japanese Patent Publication No. 10-305091. Specifically, these are as follows.

[0029] Examples of titanium halides include titanium tetrachloride, titanium tetrabromide, titanium tetrafluoride, and titanium tetraiodate.

[0030] Examples of titanium alkoxides include titanium tetraalkoxide represented by the general formula Ti(OR)4 (wherein R independently represents an alkyl group), hydrolysis condensates of titanium tetraalkoxide, isopropyl triisostearoyl titanate, isopropyl tri-n-dodecylbenzenesulfonyl titanate, isopropyl tris(dioctyl pyrophosphate) titanate, tetraisopropyl bis(dioctyl phosphite) titanate, tetraoctyl bis(ditridecyl phosphite) titanate, and tetra(2,2-diallyloxymethyl Examples include -1-butyl)bis(di-tridecyl)phosphite titanate, bis(dioctyl pyrophosphate)oxyacetate titanate, bis(dioctyl pyrophosphate)ethylene titanate, isopropyltrioctanoyl titanate, isopropyl dimethacryloyl isostearoyl titanate, isopropyl isostearoyl diacrylic titanate, isopropyl tri(dioctyl phosphate) titanate, isopropyl tricumylphenyl titanate, and isopropyl tri(N-aminoethyl-aminoethyl) titanate.

[0031] In the general formula Ti(OR)4 (wherein R independently represents an alkyl group), the alkyl group represented by R is preferably an alkyl group having 1 to 10 carbon atoms, and more preferably, for example, a methyl group, an ethyl group, an n-propyl group, an isopropyl group, an n-butyl group, an n-octyl group, or a 2-ethylhexyl group. Examples of such titanium tetraalkoxides include tetra-n-butoxytitanium, tetra-i-propoxytitanium, and tetrakis(2-ethylhexyloxy)titanium.

[0032] The hydrolysis condensates of titanium tetraalkoxides are branched or linear hydrolysis condensates of titanium tetraalkoxides. They are obtained when an aqueous solution containing an acid catalyst such as hydrochloric acid is added to titanium tetraalkoxide, causing hydrolysis and condensation reactions between the titanium alkoxides.

[0033] When used alone and heated, titanium chelate compounds that undergo hydrolysis and condensation polymerization are preferred. Examples include oxybisacetylacetonatotitanium, tetrakisacetylacetonatotitanium, dibutoxybisacetylacetonatotitanium, diisopropoxybisacetylacetonatotitanium, diisopropoxybisethylacetylacetonatotitanium, diisopropoxybistriethanolaminetitanium, and dihydroxybislactatotitanium.

[0034] Peroxotitanic acid is a compound represented by H4TiO5, and examples of its salts include sodium peroxotitanate and potassium peroxotitanate.

[0035] Among the biodegradable titanium compounds mentioned above, hydrolyzable titanium compounds are preferred from the viewpoint of simplifying the loading process, ease of availability, and cost, more preferably at least one selected from titanium halides and titanium alkoxides, and even more preferably at least one selected from titanium tetrachloride and titanium tetraalkoxides.

[0036] In addition to the essential components mentioned above, other components may be added to the mixture as needed. In particular, if the decomposable titanium compound is decomposed by the reactive compound, this reactive compound will be added as needed. However, from the viewpoint of efficiently fixing the photocatalytic fine particles to the titanium oxide film and ensuring better photocatalytic activity, it is preferable not to include other fine particles such as silica, binder resin, or components that are difficult to remove by heat treatment, etc.

[0037] The mixture can be obtained by mixing and stirring each component. There are no particular limitations on the concentration of each component in the mixture, but for example, when applying the mixture by spraying, in a mixture consisting of a liquid phase containing a solvent and a degradable titanium compound and a solid phase containing photocatalytic fine particles, the liquid phase may contain 90-99.5% by mass of the solvent and 0.5-10% by mass of the degradable titanium compound, and the solid phase may contain 0.5-3 g or 0.5-1 g of photocatalytic fine particles per 100 ml of the liquid phase (as a mixture).

[0038] In the loading process, the aforementioned mixture is brought into contact with the titanium oxide film under conditions in which the decomposable titanium compound decomposes. "Under conditions in which the decomposable titanium compound decomposes" means conditions such as heating at a predetermined temperature for a predetermined time, irradiating with light of a predetermined wavelength for a predetermined time, or reacting with a reactive compound such as ozone at a predetermined temperature for a predetermined time, depending on the type of decomposable titanium compound, and "decompose" means that other compounds are generated from the decomposable titanium compound. There are no particular limitations on the method of contact between the mixture and the titanium oxide film, and examples include coating and immersion. Examples of coating methods include spray coating (coating by spraying), bar coating, and spin coating.

[0039] When the decomposable titanium compound is, for example, a hydrolyzable titanium compound that can be decomposed by heating, it is preferable that the titanium oxide film be heated to a temperature between the boiling point of the solvent and 800°C when the mixed solution is brought into contact with the titanium oxide film. However, this boiling point is above the temperature at which the hydrolyzable titanium compound decomposes. This allows the solvent to evaporate immediately when the mixed solution is brought into contact with the titanium oxide film. In addition, the hydrolyzable titanium compound decomposes, allowing for better formation of titanium oxide particles derived from the hydrolyzable titanium compound. Furthermore, it is preferable to bring the two into contact by spraying the mixed solution onto the titanium oxide film using a sprayer or the like. This allows for more uniform application of the mixed solution to the entire titanium oxide film. It is then presumed that the components in the mixed solution that come into contact with the titanium oxide film react immediately, forming particles of titanium oxide derived from the hydrolyzable titanium compound throughout the titanium oxide film, and that these titanium oxide particles are well bonded to the titanium oxide film and photocatalytic fine particles. Furthermore, these titanium dioxide particles are porous, and it is presumed that photocatalytic microparticles are supported on the surface and within the pores of the particles in a more uniform distribution. On the other hand, if the decomposable titanium compound does not decompose upon heating, and if light irradiation or the addition of reactive compounds such as ozone is performed while the two are in contact or after contact, there are no particular limitations on how the two are brought into contact.

[0040] Photocatalytic fine particles can be supported on a titanium oxide film via decomposition products derived from a degradable titanium compound. After the supporting process is complete, a sintering process can be performed in which the film is heated to a temperature above the boiling point of the solvent. When heating is performed in the supporting process, it is preferable to heat to a temperature higher than the temperature at which the supporting process was performed. This ensures that the solvent is reliably removed. As a result, the photocatalytic activity can be further improved. Furthermore, from the viewpoint of more reliably removing organic compounds resulting from the decomposition of the degradable titanium compound, heating may be performed to an even higher temperature than its boiling point, for example, to a temperature of about four times or more the boiling point. The heating time in the sintering process can be appropriately determined depending on the type of substrate, the components of the mixed liquid, etc.

[0041] For example, as described above, the photocatalytic component obtained through at least the oxidation treatment step and the support treatment step has photocatalytic nanoparticles that are well supported on a pre-formed porous titanium oxide film via decomposition products derived from a degradable titanium compound. Furthermore, these supported photocatalytic nanoparticles maintain their activity. Therefore, the photocatalytic component has good photocatalytic activity. The amount of photocatalytic nanoparticles supported can be appropriately set according to the photocatalytic activity, material, etc.

[0042] Furthermore, as described above, the photocatalytic material obtained through at least the oxidation treatment and support treatment processes possesses both good photocatalytic activity and excellent hydrophilicity. For example, the contact angle between the surface of the photocatalytic material and water can be less than 80°, and can be less than 10°, which is considered superhydrophilic. Moreover, it can be less than 5°, or even 0°. It should be noted that, for example, superhydrophilicity can be achieved by the titanium oxide film formed on the surface of the substrate as a result of anodic oxidation, but the photocatalytic activity is currently very low. The contact angle can be measured in accordance with JIS R3257 (static droplet method (θ / 2 method)).

[0043] The aforementioned photocatalytic material possesses both excellent photocatalytic activity and extremely high hydrophilicity, making it suitable for applications such as sound barriers on highways, road mirrors, various reflectors, streetlights, the bodies of vehicles such as automobiles and trains, or airplanes and ships, building materials such as exterior wall materials and roofing materials, road signs, and roadside billboards, for purposes such as providing antifouling and snow-repellent properties. [Examples]

[0044] The embodiments of the present invention will be described in detail below based on examples.

[0045] (Example 1) A pure titanium substrate was degreased by immersing it in a 70 g / l sodium hydroxide aqueous solution at 60°C for 1 minute, then rinsed with water and neutralized with a 75 g / l nitric acid aqueous solution. Subsequently, it was chemically polished by immersing it in a mixed solution of phosphoric acid and nitric acid (phosphoric acid concentration 95% by mass, nitric acid concentration 5% by mass), heated to 90°C, for 1 minute to remove the oxide film on the substrate surface (pretreatment step). Then, an anodizing treatment was performed using a mixed solution of sulfuric acid and oxalic acid (sulfuric acid concentration 100 g / l, oxalic acid concentration 10 g / l) as the electrolyte (oxidation treatment step). The conditions for the anodizing treatment were: electrolyte temperature 10°C, duty cycle ratio 25:10, constant current electrolysis, positive current 1 dm 2 The substrate was treated with a current of 42A per inch and a negative current of 25A for 5 minutes. Afterwards, the substrate was washed with water, desmatted, washed with pure water, and dried. Scanning electron microscopy (SEM) imaging and X-ray diffraction confirmed that a titanium oxide film (thickness 4-5 μm) with pores of approximately 100-400 nm in size was formed on the surface of the anodized substrate.

[0046] To ethyl alcohol (ethanol), tetra-n-butoxytitanium (titanium tetrabutoxide) is added to a concentration of 1% by mass. To 100 ml of this solution, titanium dioxide fine particles (manufactured by Ishihara Sangyo Co., Ltd., ST-01, specific surface area 300 m²) are added. 2 0.5 g of titanium dioxide (average particle size 7 nm) was added and stirred to prepare a mixture of titanium dioxide fine particles (hereinafter referred to as the "mixture").

[0047] After heating the substrate on which the titanium oxide film was formed as described above to 380°C, the mixture was sprayed onto the surface of the substrate while maintaining that temperature. The amount of the mixture sprayed was approximately 1 cm from the surface of the substrate. 2 Each sample contained 1.6 ml (8 mg of titanium dioxide fine particles) (the above is the loading process).

[0048] After the loading process, the material was heated at 500°C for 3 hours. During this process, any organic components that may remain on the titanium oxide film were removed (this completes the baking process). The material was then cooled to obtain a component with photocatalytic activity. The obtained component was subjected to the evaluation described later. The amount of titanium oxide supported on the substrate was 2 mg / cm³. 2 That was the case.

[0049] (Example 2) A photocatalytically active component was obtained in the same manner as in Example 1, except that the concentration of titanium tetrabutoxide was set to 2.5% by mass.

[0050] (Example 3) A photocatalytically active component was obtained in the same manner as in Example 1, except that the amount of titanium dioxide fine particles added was 1 g.

[0051] (Comparative Example 1) An anodizing treatment was performed in the same manner as in Example 1, and only the oxidation treatment step was carried out to obtain a substrate on which a titanium oxide film was formed.

[0052] (Comparative Example 2) A photocatalytically active component was obtained in the same manner as in Example 1, except that a mixture containing titanium dioxide fine particles was used.

[0053] (evaluation) <Scanning Electron Microscope (SEM) Observation> The surfaces of the members obtained in Example 1, and the surfaces and cross-sections of the base materials obtained in Comparative Example 1 were observed by SEM. The imaging of the surface of Example 1 is shown in Figs. 1, 2(a), and 2(b), and the imaging of Comparative Example 1 is shown in Figs. 3 and 4. Note that the base material after the anodic oxidation treatment in Example 1 had the same imaging as that in Comparative Example 1. Figs. 1, 2(a), and 2(b) were taken with a JCM-7000 manufactured by JEOL Ltd., and Figs. 3 and 4 were taken with a SU-8000 manufactured by Hitachi High-Technologies Corporation.

[0054] <X-ray Diffraction Measurement> Using the member having photocatalytic activity obtained in Example 1 and the base material on which the titanium oxide film was formed in Comparative Example 1, the X-ray diffraction of the surface was measured. A MiniFlex-II manufactured by Rigaku Corporation was used for the measurement. The measurement results of Comparative Example 1 and Example 1 are shown in Figs. 5 and 6, respectively.

[0055] <Aldehyde Odor Test> The members of Examples 1 to 3, the base material on which the titanium oxide film was formed in Comparative Example 1, and the member of Comparative Example 2 were used as test pieces (50 mm × 50 mm), and the decomposition ability of acetaldehyde was measured. Each test piece and acetaldehyde at a concentration of 500 ppm were enclosed in a sealable acrylic case with a vertical size of 75 mm × horizontal size of 75 mm × height of 90 mm. The test pieces were irradiated with ultraviolet rays using three ultraviolet LEDs (wavelength 375 nm, 2.2 W) manufactured by Nichia Chemical Industries, Ltd., and the concentration of acetaldehyde was measured with an odor measuring device (Photoacoustic Multi-Gas Monitor 1512-5 manufactured by Luma Sence Technologies (INNOVA), measurement limit 0.5 ppm). The measurement results of Example 1, Comparative Examples 1 and 2 are shown in Fig. 7. The results of Examples 2 and 3 were equivalent to those of Example 1.

[0056] <Hydrophilicity: Contact Angle of Water> Using the member of Example 1, the contact angle with water was measured in accordance with JIS R3257 (the sessile drop method (θ / 2 method)). As a result, the contact angle of water on the surface of the member of Example 1 was 0°.

[0057] As shown in Figures 1-4, by performing the predetermined treatment as in Example 1, a porous titanium oxide film (reference numeral 2 in Figures 3 and 4) is formed on the surface of the substrate (reference numeral 3 in Figure 3), and titanium oxide particles derived from titanium tetrabutoxide are formed on this titanium oxide film (see Figures 1 and 2(a) in particular), and photocatalytic titanium oxide nanoparticles are supported on the surface of these particles (see Figure 2(b) in particular). As shown in Figure 1, the entire surface of the titanium oxide film is covered with titanium oxide particles derived from titanium tetrabutoxide, and the titanium oxide film cannot be seen with the naked eye. As shown in Figure 2, since a very large number of photocatalytic titanium oxide nanoparticles are supported on the surface of the titanium oxide particles derived from titanium tetrabutoxide, individual nanoparticles cannot be seen with the naked eye. As shown in Figure 5, the X-ray analysis result shown as "Sample(12-H)" is closer to the X-ray analysis result of the rutile crystal structure shown as "rutile" than to the X-ray analysis result of the anatase crystal structure shown as "anatase", indicating that the titanium oxide coating of Comparative Example 1 contains a large amount of rutile titanium oxide. On the other hand, as shown in Figure 6, the X-ray analysis result shown as "Sample Surface" is closer to the X-ray analysis result of the anatase crystal structure shown as "anatase" than to the X-ray analysis result of the rutile crystal structure shown as "rutile" (for example, the size of the 25-degree peak, etc.), indicating that when photocatalytic nanoparticles of titanium oxide are supported on a titanium oxide coating via titanium oxide particles, which are decomposition products derived from a degradable titanium compound, as in Example 1, the surface layer of the photocatalytic member contains a large amount of titanium oxide with anatase crystal structure. As shown in Figure 7, Example 1 shows a faster rate of acetaldehyde concentration reduction compared to Comparative Example 1, which only had a titanium dioxide coating, and Comparative Example 2, which had a titanium dioxide layer formed on the titanium dioxide coating using a conventional method. Furthermore, while the acetaldehyde concentration in Comparative Examples 1 and 2 did not reach zero even after 30 minutes, the acetaldehyde concentration in Example 1 was almost zero in about 5 minutes, indicating high photocatalytic activity. In addition, the component of Example 1 has a surface contact angle with water of 0°, indicating that it has a surface with excellent photocatalytic activity and superhydrophilicity. [Explanation of Symbols]

[0058] 1. Titanium oxide particles derived from titanium butoxide 2. Titanium oxide coating 3 Base material

Claims

1. An oxidation treatment step in which an oxidation treatment is performed on the surface of a substrate made of titanium, a titanium alloy, a titanium compound, or a metal containing a titanium compound to form a titanium oxide film on the substrate, A method for producing a photocatalytically active member, comprising a supporting step of contacting a titanium oxide film with a mixed solution containing a solvent selected from water-soluble organic solvents and water-insoluble organic solvents, photocatalytically active fine particles, and a degradable titanium compound, under conditions in which the degradable titanium compound decomposes, thereby supporting the fine particles on the titanium oxide film via decomposition products derived from the degradable titanium compound.

2. A method for producing a photocatalytically active member according to claim 1, further comprising a baking step of heating the solvent to a point above its boiling point after the supporting step.

3. A method for producing a photocatalytically active member according to claim 1 or 2, wherein the decomposable titanium compound is at least one selected from titanium halides and titanium alkoxides.

4. A method for producing a photocatalytically active member according to any one of claims 1 to 3, wherein in the loading process, the titanium oxide film is heated to a temperature between the boiling point of the solvent and 800°C.

5. A method for producing a photocatalytically active member according to any one of claims 1 to 4, wherein the surface of the substrate is formed of titanium, and the titanium is subjected to an oxidation treatment.

6. A method for producing a photocatalytically active member according to any one of claims 1 to 5, wherein the photocatalytically active fine particles are titanium dioxide fine particles.

7. A substrate formed of titanium, titanium alloy, titanium compound, or a metal containing a titanium compound, A titanium oxide coating formed on the surface layer of the substrate, A photocatalytically active member comprising: a titanium oxide coating with photocatalytically active fine particles supported on it via decomposition products of a degradable titanium compound.

8. A member having photocatalytic activity according to claim 7, wherein the contact angle with water on the surface is less than 80°.

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