Architectural material using metal oxide exhibiting photocatalytic activity

Abstract: A metal-oxide layer exhibiting a photocatalytic activity function is formed on the surface of an inorganic architectural material, such as external wall material, roofing material, internal wall material, flooring material, and ceiling material, including glass, tile, concrete, stone, metal, and the like, so as to provide the property of deodorizing a space coming in contact with the architectural material, and antimold, antisoiling properties, and ultraviolet-ray absorbency of the surface of the architectural material, as well as the long-term maintenance of these properties. Preferably, the metal-oxide layer is formed by fixing a metal-oxide thin film on the surface of the architectural material. Alternatively, the metal-oxide layer is formed as an architectural material in which the surface thereof and its vicinity are mainly formed of a metal mixture including a metal oxide, such as titanium oxide, and palladium for improving photocatalytic activity, or a metal mixture including a metal constituting the metal oxide, such as titanium, and a composite of a second metal, while its inner portion is substantially formed of a metal mixture including titanium or a composite of titanium and palladium, the surface and its vicinity as well as the inner portion being formed continuously. As a method of manufacturing the latter architectural material, a metal mixture, i.e., an alloy, of titanium and a metal for improving photocatalytic activity, such as palladium, is fabricated, and after the alloy is processed into a desired shape, the processed alloy is subjected to oxidation treatment.

Description: BACKGROUND OF THE INVENTION Field of the Invention: The present invention relates to an architectural material, and more particularly to an architectural material excelling in deodorizing, antimold, and antisoiling properties, and further to an architectural material excelling in peel resistance and durability, as well as a simple method for manufacturing an architectural material excelling in the deodorizing property and durability. Description of the Related Art: As environmental problems have come more into focus, issues of deodorizing indoor spaces, and antimold and antisoiling properties of architectural material surfaces, and the like have come to attract attention. Concerning deodorization, a method is conventionally known in which an apparatus or a piece of equipment is used for exhausting unwanted odors to the outside. As for antimold needs, the removal of molds by means of chemicals is performed by selecting an appropriate chemical according to the kind of mold. Regarding antisoiling needs, periodical cleaning by a person is only carried out. Odors, molds, and soiling are essentially attributable to microorganisms, such as bacteria, yeasts and molds, and animal and plant cells. Accordingly, the attempt to deodorize and prevent molds and fouling can, in principle, be considered as the destruction of these cells, i.e., sterilization. Generally known methods of sterilization include heating, irradiation with ultraviolet or other radioactive rays, cell destruction by means of ultrasonic waves, electric sterilization, gas sterilization, and sterilization using chemicals including antibiotics. In addition, a sterilization method using fine particles of a photo-semiconductor is also known. As part of this line of effort, basic research is being undertaken on the removal of organic and inorganic contaminants in water and air by using titanium dioxide photocatalysts. Namely, semiconductors such as titanium dioxide are known to exhibit a photocatalytic function by means of a light of a specific wavelength and possess deodorizing and antimold functions through their powerful oxidizing action. It is stated on page 211 of Vol. 13, No. 5 (1985), of the "Bohkinbohkabi (Fungus and Mold Prevention) Journal" that a fixed film consisting of fine particles of titanium dioxide is useful as a sterilizing reactor. In addition, Japanese Patent Publication No. 9850/1990 discloses a method of purifying wastes by the use of a semiconductor, such as titanium oxide, which carries a metal or a metal oxide therein. Conventionally, titanium dioxide, iron oxide, tungsten oxide, silicon oxide and the like having a semiconductor function, or such metals carrying a second metal, such as platinum, thereon for the purpose of improving the catalytic function are used as photocatalysts. To make use of the deodorizing and antimold functions, such metals are pulverized into fine particles to form a fixed film on a surface, or the fine particles are used by being dispersed in an object to be treated. The document JP-A-3 073 304 discloses a building article comprising a wooden base having a light-receiving surface and used as an architectural material or building material; and at least one metal oxide layer or thin film exhibiting photocatalytic activity and selected from the group consisting of titanium dioxide, aluminium oxide and silicon oxide, said at least one metal oxide layer being formed on a surface of said base. Although various studies have been made regarding methods of imparting the deodorizing and antimold functions to architectural materials by making use of the photocatalytic function, in accordance with the above-described method, particles are troublesome to handle as materials. The known fixed films have only been used experimentally, and their strength is not sufficient. The fabrication of semiconductor materials into thin film has been industrially difficult, and has not yet been put to practical use. As described above, for deodorizing, an apparatus or piece of equipment must have a sophisticated function and made large in size, which results in high running cost and is clearly uneconomical. Moreover, since air is exhausted through an opening of a limited size, it is extremely difficult to deodorize the entire indoor space. The conventional antimold method is no more than a short-term measure, and the long-term maintenance of the antimoldproperty remains unresolved. As for the antisoiling property, if the cleaning of the outer wall surfaces of large buildings is considered, huge expenses are required for manpower needed for cleaning, and, since the long-term maintenance of the antisoiling property is not ensured, repeated cleaning operations are unavoidably carried out. Furthermore, as for the deodorization, antimolding, and antisoiling of architectural materials, the conventional sterilization methods are either impractical or difficult to put to practical use in the light of long-term maintenance, economy, technical difficulties, inexperience in techniques, and the like. SUMMARY OF THE INVENTION In view of the above-described circumstances, it is a primary object of the present invention to provide an dorizing and antimold functions imparted by using a photocatalytic function, has high efficiency in the photocatalytic function, is easy to manufacture, has high strength, excels in the peel resistance and durability, and facilitates processing into a shape suited to a purpose. A second object of the present invention is to provide a simple method of manufacturing an architectural material which is uniform and excels in durability and deodorizing and antimold effects. These objets are solved by an architectural material as defined in claim 1 and the method defined in claim 5. The architectural material in accordance with the present invention, when seen as a basic material, includes nonferrous inorganic materials such as glass, stone, stone-quality products, and sintered clay products: metallic inorganic materials such as iron and steel products. On these architectural materials, a thin film of a metal oxide needs to be formed. In the case, inorganic materials and heat-resistant organic materials are preferably used since the architectural materials are formed at a high temperature of, for instance, 400°C and because of their affinity with the metal oxides. In a case where the formation of a thin film is possible at a relatively low temperature, ordinary organic materials may be used. The architectural material in accordance with the present invention is used suitably as an external wall material, a roofing material, an internal wall material, a flooring material, a ceiling material, and so on. More specifically, the architectural material is used for exterior surface portions including the external wall (including glass windows) and roof tiles, and interior surface portions such as interior walls of a living room, a toilet room and the like, a floor, and a ceiling. As specific examples of inorganic materials used for these portions, it is possible to cite glass, tile, tiles used for roofing, concrete, stone, metal, and composite materials thereof. The metal oxide used in the present invention may be any of the semiconductors insofar as they are activated upon being irradiated with light and drive oxidation and reduction reaction. For example, it is possible to use at least one compoud selected from the group consisting of titanium dioxide, iron oxide,silver oxide, copper oxide, aluminium oxide, tungsten oxide, silicon oxide, zinc oxide, and strontium titanate. Also, metal or other metal oxides modifying this metal oxide may be used suitably for promoting the photocalytic reaction, and it is possible to use at least one compound selected from the group consisting of, for example, platinum, palladium, gold, silver, copper, nickel, rhodium, niobium, tin, cobalt, ruthenium oxide, and nickel oxide. As the amount added to modify the metal oxide, it is preferable to use such metals or metal oxides in the range of from 0.01 to 20 wt.% with respect to the metal oxide in the present invention. As the method of preparing the aforementioned metal oxide, the metal oxide may be prepared by high-temperature sintering of a metal, electrolytic oxidation, a chemical deposition process, a vacuum deposition process, a coating process, a coprecipitation process, an evaporation oxidation process such as a metallic halogenation process, neutralization and hydrolysis of an inorganic metal salt, hydrolysis of a metal alkoxide, and a sol-gel process. Alternatively, a commercially available product may be used. As the method of modifying the aforementioned metal or other metal oxide, it is possible to use a conventionally used method, such as a impregnation method, a precipitation method, an ion-exchange method, an optoelectrodeposition method, a kneading method. Light energy based on irradiation, which is used in the present invention, includes a wavelength region corresponding to the excitation of photocatalysis. Specifically, it is preferable to use light energy which includes an ultraviolet wavelength below 400 nm, which contributes to the photocatalytic reaction. As the light energy source, it is possible to cite a natural light source from the sun, as well as an artificial light source such as light from a mercury lamp, light from a fluorescent lamp, light from a filament lamp like a halogen lamp, light from a short-arc xenon lamp, and a laser beam. In addition, as an auxiliary light source for the rays of the sun, an artificial light source may be used concurrently. As the method of irradiation, it is possible to use a method in which the light is directly radiated onto the metal-oxide thin film formed on the architectural material, or, in the case of a transparent architectural material such as glass, it is possible to use a method in which the light is radiated onto the thin film therethrough, or sunlight and artificial light are used jointly to irradiate the thin film from various angles. In the present invention, if the light is radiated onto the material on which a metal-oxide thin film exhibiting photocatalytic activity is formed, odors, molds, and substances constituting causes of soiling (hereafter referred to as unwanted substances), which adhere to or are in contact with the surface of the architectural material where the thin film is formed, can be decomposed and removed at normal temperature photochemically through the photocatalysis of the thin film. Accordingly, unlike conventional techniques, physical labor, large-scale equipment and facilities, and maintenance are practically unrequired. At the same time, since such inexhaustible energy as sunlight can be used as the light energy, unwanted substances can be decomposed and removed very economically and simply. As compared with conventional catalysts, such as oxidation catalysts, the metal oxide used as the photocatalyst in the present invention undergoes a small decline in activity due to heat deterioration and poisoning elements, so that the functions of decomposing and removing the unwanted substances, i.e., the deodorizing property, the antimold property, and the antisoiling property are maintained over long periods of time. The architectural material in accordance with the present invention is structured such that the surface region of the architectural material includes an outer portion and an inner portion. The outer portion is formed of a metal mixture including a metal oxide which exhibits a photocatalytic function, such as titanium dioxide, and a second metal for improving the photocatalytic function, and the inner portion is formed of a metal mixture including a metal of the same kind as that which constitutes that metal oxide, such as titanium, and the second metal for improving the photocatalytic function, the outer portion as well as the inner portion being formed continuously. As such, a uniform photocatalytic phase is formed on the surface, and the architectural material demonstrates an excellent deodorizing and antimold effect by virtue of the efficient photocatalytic reaction. In addition, since the photocatalytic phase is formed rigidly and continuously, the catalyst phase does not peel off, and processing is facilitated. In addition, in the method of manufacturing an architectural material in accordance with the present invention, the architectural material is manufactured by forming and processing a metal mixture (an alloy) which includes a metal of the same kind as the metal constituting the aforementioned metal oxide, such as titanium, and a second metal for improving the photocatalytic function, and then subjecting the metal mixture to oxidation treatment. Accordingly, a uniform architectural material of an arbitrary shape which excels in deodorizing and antimold effects can be obtained by a simple method. Other objects, features and advantages of the present invention will become more apparent from the following detailed description of the invention when read in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a cross-sectional view of a model showing a composite phase in the architectural material obtained from a titanium-palladium alloy; Fig. 2 is a diagram of the state of a titanium-palladium binary system; Fig. 3 is a schematic diagram of an anodic oxidation treatment apparatus; Fig. 4 is a diagram of the state of a titanium-silver binary system of a metal mixture; Fig. 5 is a schematic diagram of a testing apparatus for evaluating the deodorizing property; Fig. 6 is a graph showing a change in the residual concentration of acetaldehyde; and Fig. 7 is a schematic diagram of a testing method for evaluating peel resistance. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Hereafter, a more detailed description of the present invention will be given by citing embodiment, but the present invention is not limited to these embodiment and various modifications are possible within the scope of the present invention as claimed. The architectural material in accordance with the present invention is structured as follows: The surface region of the architectural material includes an outer portion and inner portion. The outer portion is substantially formed of a metal mixture including a metal oxide which exhibits photocatalytic activity and a second metal for improving the photocatalytic activity of that metal oxide, and the inner portion is substantially formed of a metal mixture including a metal of the same kind as that which constitutes that metal oxide and the second metal for improving the photocatalytic activity of that metal oxide. The outer portion as well as the inner portion are formed continuously. The metal oxide which is used in this embodiment and exhibits the photocatalytic function is not particularly limited. However, it is possible to cite those substances that are disclosed in Japanese Patent Publication No. 9850/1990. As specific examples, it is possible to cite titanium dioxide, iron oxide, silver oxide, copper oxide, tungsten oxide, aluminum oxide, zinc oxide, silicon dioxide, strontium titanate, and other similar compounds. It is preferable to use among them titanium dioxide, iron oxide, tungsten oxide, zinc oxide, and strontium titanate. In particular, titanium dioxide excels in deodorizing and antimold effects, is easy to obtain and process, and is therefore the most preferable. As the metal constituting the metal oxide exhibiting the photocatalytic activity, it is possible to cite titanium, iron, silver, copper, aluminum, tungsten, zinc, strontium, and the like. In addition, the second metal for improving the photocatalytic activity of the metal oxide, i.e., the metal or other metal oxide which modifies the metal oxide, is a compound which coexists with the metal oxide and is capable of forming a site for reduction reaction in the photocatalytic reaction. For instance, it is possible to use at least one compound selected from platinum, palladium, gold, silver, copper, nickel, rhodium, niobium, tin, cobalt, ruthenium oxide, and nickel oxide. As for the amount of the second metal to be mixed in, it is preferable to use the second metal in the range of from 0.01 to 20 wt.% with respect to the metal oxide in the present invention. In addition, the architectural material in accordance with this embodiment of the present invention is preferably structured such that the outer portion is substantially formed of a metal mixture which is expressed by the following general formula (I): [TiO 2 ] x [TiM y ] 1-x or [TiO 2 ] x M 1-x (where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni, and Co; x is such that 0.3 ≤ x< 1; and y is an integer peculiar to the metal M combining with Ti and is any one of 1, 2, and 3), and its inner portion is a metal mixture which is expressed by the following general formula (II): [Ti] x [TiM y ] 1-x or [Ti] x M 1-x (where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni, and Co; x is such that 0.3 ≤x < 1; and y is an integer peculiar to the metal M combining with Ti and is any one of 1, 2, and 3). In the case of this preferable form, the closer to the surface the portion is, the greater its content of titanium dioxide [TiO 2 ], and the greater the proportion of titanium [Ti]. x represents a molar ratio, shows a ratio between titanium dioxide or titanium in the metal mixture and the metal [M] for improving the catalytic function, and is preferably 0.7 to 0.9 or thereabouts. In this embodiment, titanium dioxide, which is most suitable as a substance exhibiting the photocatalytic function, is used. The metal M for improving the photocatalytic function of titanium dioxide is a metal which is suitably used among metals which coexist with titanium dioxide and are capable of forming sites for reduction reaction in the photocatalytic reaction. These metals are generally called precious metals, and elements in Groups VIII and Ib can be typically cited. Here, the metal M is selected from the group consisting of platinum, gold, palladium, silver, copper, nickel, and cobalt which are highly effective. Among them, platinum, gold, palladium, and silver are preferable in view of deodorizing and antimold effects. Palladium is particularly preferable in view of ease of processing and the price. In this embodiment, the word "substantially" is meant to include the presence of impurities or mixtures to such an extent that it does not impair the advantages of the present invention. In the outer portion, titanium dioxide and the metal M selected from the group of metals, when combined, exhibit a structure similar to that of an alloy. In other words, the phase consisting of only titanium dioxide and the metal M, or the phase consisting of only titanium dioxide and a composite phase consisting of titanium dioxide and the metal M, exhibit a mixed structure (metal mixture) in which these metals are finely and uniformly dispersed. The closer to the inner portion of this metal mixture, the more titanium dioxide in the metal mixture is replaced by metal titanium, changing continuously to the metal mixture (alloy) consisting of metal titanium and the metal M. Fig. 1 is a cross-sectional view of a model showing the state of phase of a metal mixture of the architectural material in accordance with the present invention in which M is palladium Pd. An outer surface of the architectural material includes an outer layer or portion formed of TiO 2 phase 50 and a TiPd 2 phase 54 dispersed on the surface and the vicinity. The TiO 2 phase exhibits the photocatalytic function, while the TiPd 2 phase promotes that function. The concentration of TiO 2 phase 50 decreases with increasing depth from the surface, and eventually ends. An inner layer or portion includes a Ti phase 52, which is unrelated to the photocatalytic function, which is present at certain depths from the outer surface. The concentration of Ti phase 52 increases with increasing depth from the surface and, at a certain depth, and the structure becomes one in which the Ti phase 52 and the TiPd 2 phase 54 are only present. The changes in concentrations of TiO 2 phase 50 and Ti phase 52 are gradual with changing depths from the outer surface. As described above, since the titanium dioxide/metal phase exhibiting the photocatalytic function and the titanium/metal phase serving as a carrier constitute an identical architectural material structure, the photocatalytic phase is prevented from peeling off, so that the architectural material is provided with the strength and peel resistance necessary for withstanding practical use. Next, a description will be given of a method of manufacturing an architectural material. As the manufacturing method, first, a metal mixture, i.e., an alloy, which contains the metal constituting the metal oxide exhibiting the photocatalytic activity and the second metal for improving the photocatalytic activity of the metal oxide, is manufactured. After the alloy is processed into a desired shape, the processed alloy is subjected to oxidation treatment. The metals which are used are the same as those of the above-described architectural material. As the metal mixture, a metal mixture, i.e., alloy, which is expressed by the following general formula (II) is preferably used: [Ti] x [TiM y ] 1-x or [Ti] x M 1-x (where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni, and Co; x is such that 0.3 ≤ x < 1; and y is an integer peculiar to the metal M combining with Ti and is any one of 1, 2, and 3). The alloy expressed by general formula (II) above exhibits at room temperature a mixed structure in which the α phase consisting of metal titanium and the metal M" are finely and uniformly dispersed, or a mixed structure in which "the α phase consisting of metal titanium and the composite phase consisting of metal titanium and the metal M" are finely and uniformly dispersed. x represents a molar ratio of titanium dioxide with respect to the metal M, while y represents a molar ratio of the metal M with respect to metal titanium in the composite phase consisting of metal titanium and the metal M. The metal mixture (alloy) of such a mixed structure is manufactured, and after it is processed into a desired shape for use such as a sheet or a foil, the metal mixture is subjected to oxidation treatment. Before oxidation treatment is conducted, pretreatment such as heat treatment may be carried out. The metal mixture is subjected to forming, and surface cleaning is then carried out before oxidation treatment is provided. In view of the uniformity of treatment and the strength of the photocatalytic phase, it is preferable to conduct anodic oxidation treatment in an electrocatalytic solution. If oxidation treatment is provided, the surface of the α phase consisting of metal titanium" is oxidized, thereby making it possible to form the titanium dioxide phase. Thus, it is readily possible to obtain a rigid photocatalytic phase in which the phase consisting of titanium dioxide, which plays the role of oxidation decomposition reaction in the photocatalytic reaction, and the phase consisting of the metal M or the composite phase, consisting of the metal M and titanium, which plays the role of promoting the photocatalytic reaction as a catalyst for reduction reaction, are finely and uniformly dispersed in the alloy surface. Example 1 of manufacture The manufacture of an architectural material consisting of a titanium-palladium binary system Fig. 2 is a diagram of the state of a titanium-palladium binary system of a metal mixture. This is a case where M is Pd in general formula (II). Metal mixtures (hereafter referred to as alloys) A, B and C were fabricated by being melted with compositions of x = 0.9, 0.8, and 0.7, respectively. Ingots of the alloys A, B and C were hot rolled into sheets of 110 mm in width and 2 mm in thickness at 900°C, and were acid pickled in an aqueous solution of 5 wt.% fluorine to remove oxide film from their surfaces. Then, they were cut into sizes of a 100 mm square and 1.6 mm in thickness. Fig. 3 is a schematic diagram of an anodic oxidation treatment apparatus. The alloy was connected to an anode 56, while metal aluminum was connected to a cathode 58. An aqueous solution 62 of 1 wt.% phosphoric acid was filled in a cell 60. While observing a voltmeter 64 and an ammeter 66 and adjusting the voltage, electric power was supplied from a dc power supply device 68 so as to effect anodic oxidation treatment. That is, the obtained metal tile was attached to the anode 56 of the anodic oxidation treatment apparatus, and anodic oxidation treatment was carried out in the aqueous solution of 1 wt.% phosphoric acid at a voltage of 10 to 250 V, thereby oxidizing the titanium phase (α phase) in each alloy and forming on its surface a titanium dioxide phase having a thickness of dozens of angstroms to several microns. Thus, metal tiles having the deodorizing and antimold functions were obtained. Example 2 of manufacture The manufacture of an architectural material consisting of a titanium-silver binary system Fig. 4 shows a diagram of the state of a titanium-silver binary system of a metal mixture. This is a case where M is Ag in general formula (II). Alloys D and E were fabricated by being melted with compositions of x = 0.9 and 0.7, respectively. Ingots of the alloys D and E were treated in the same manner as in example 1 of manufacture, and metal tiles having the deodorizing and antimold functions were obtained. Example 5 of evaluation of deodorizing property Evaluation of the deodorizing property of metal tiles Fig. 5 shows a schematic diagram of a testing apparatus for evaluating the deodorizing property. A sample 72 was placed in the bottom of an experiment tank 70 made of quartz glass. An aldehyde gas was supplied to the experiment tank 70 from a standard-gas generating device 74 via a gas supply port 76. A pressure gage 78 and an agitator 80 were placed in the apparatus. The state of the interior was observed by means of a gas sensor 52, a hygrothermograph 84, and an ultraviolet-ray intensity meter 86. The metal tile samples obtained in examples 1 and 2 of manufacture were placed, with the treated surfaces facing upward, in the bottom of the experiment tank made of quartz glass in the testing apparatus for evaluating the deodorizing property. 5 ppm of aldehyde was introduced into the evaluating apparatus through the gas supply port 76, and the light was radiated from the BL lamp (black lamp) (not shown) from above the evaluating apparatus. The change over time of the aldehyde concentration at that time was measured by gas chromatography, and the degree of a decline in the aldehyde residual rate was used as an index of the deodorizing performance. As a comparative sample, an evaluation was similarly made in which a titanium dioxide-palladium thin film obtained by applying an aqueous solution of a titanium dioxide sol thereon was formed on a metal tile. Fig. 6 is a graph showing a change in the residual concentration of acetaldehyde. In Fig. 6, a represents a curve which shows the residual concentration of acetaldehyde in the metal tile obtained from the alloy A; and b, c, d, and e represent curves which show the residual concentrations of acetaldehyde in the metal tiles obtained from the alloys B, C, D, and E, respectively. f represents a curve which shows the residual concentration of acetatdehyde in the metal tile obtained from the comparative sample. Example 1 of evaluation of peel resistance Evaluation of peel resistance of metal tiles Fig. 7 shows a schematic diagram of a testing method for evaluating peel resistance. As shown in Fig. 7, 10 mm-long scars were inscribed at 2-mm intervals in a central portion of the surface of each sample by using a cutter knife, thereby forming 5 x 5 squares. Then, an adhesive tape was attached to a surface portion covering the squares. After rubbing sufficiently from over the tape, the tape was peeled off, and by microscopically observing the cut portions of the sample, the number of squares in which the titanium dioxide film remained without being peeled off was counted and set as a parameter of peel strength. As a comparative sample, an evaluation was similarly made of a titanium dioxide film of 1 µm in thickness formed on a 5-cm-square glass plate by means of spin coating. In all the metal tiles obtained by subjecting the items of the present invention, i.e., the alloys A, B, C, D and E, to oxidation treatment, the titanium dioxide film was not peeled off, the number of squares remaining intact being 25. In the comparative sample, the film was peeled off in all the squares, and the result was 0. Thus, the metal tiles obtained in accordance with the present invention exhibit peel resistance. It is known that titanium dioxide produces various colors depending on the film thickness thereof. Since the thickness of the titanium dioxide film is substantially proportional to the anodic oxidation voltage, it is possible to obtain metallic architectural materials which produce various colors by controlling the oxidation voltage. In addition, since the surface phase and the inner phase are formed continuously, excellent surface strength is exhibited irrespective of the thickness of the titanium dioxide film. Hence, it is possible to arbitrarily obtain architectural materials which produce colors suited to purposes by the adjustment of the oxidation voltage, so that these architectural materials are preferable in terms of design as well. Since the architectural material of the present invention uses a titanium alloy as its base material, the architectural material excels in workability, and a desired shape can be obtained easily. Since anodic oxidation permits fine and uniform surface oxidation treatment, an architectural material of a complicated shape can be provided with a uniform and excellent photocatalytic capability. The architectural material of the present invention may be used as it is by processing the metal into an arbitrary shape as described above, or a thin sheet with a thin film formed thereon may be formed of alloys in advance and subjected to oxidation treatment, and a thin-film material thus prepared and displaying the deodorizing and antimold functions may be joined to a base material so as to be used. As a method of using the architectural material of the present invention, the architectural material may be used as it is as a metal tile or an interior trim material, or the thin sheet/thin film architectural material having a combined structure in accordance with the present invention may be prepared and used by being joined to ceramics, mortar, glass, iron plates, aluminum plates, and the like which are existing architectural materials. Thus, in accordance with the method in which the architectural material of the present invention is used by being joined to existing materials, the reduction in the amount of alloys used becomes possible, and it is possible to provide architectural materials displaying excellent deodorizing and antimold functions at low cost. The architectural material in accordance with the present invention offers outstanding advantages in the property of deodorizing an indoor space which comes in contact with the architectural material and in the antimold property, antisoiling property, and ultraviolet-ray absorbency of the surface of the architectural material, and in the long-term maintenance of these properties and economic efficiency, without impairing features of design. The architectural material in accordance with the present invention has high uniformity of material, excels in deodorizing and antimold functions, is easy to manufacture, has high strength. The material also excels in durability, and facilitates processing into a shape suited to a purpose. Furthermore, in accordance with the manufacturing method in accordance with the present invention, it is possible to readily obtain an architectural material of a desired shape, which is uniform and has superior deodorizing and antimold effects. The features disclosed in the foregoing description, in the claims and/or in the accompanying drawings may, both separately and in any combination thereof, be material for realising the invention in diverse forms thereof. However, the scope of the invention is determined by the appended claims only.

Claims: An architectural material including a surface and its vicinity which are substantially formed of a metal mixture including a metal oxide (50), characterized in that said architectural material (16) includes an external wall material, a roof material, an internal wall material, a flooring material or a ceiling material, said metal oxide exhibits photocatalytic activity, and said metal mixture includes a second metal (54) for improving the photocatalytic activity of said metal oxide, said architectural material (16) includes an inner portion which is substantially formed of a metal mixture including a metal (52) of the same kind as that which constitutes said metal oxide and said second metal for improving the photocatalytic activity of said metal oxide, and said surface and its vicinity as well as said inner portion are formed continuously. An architectural material according to claim 1, characterized in that the concentration of the metal oxide decreases with increasing depth from the surface, and in said inner portion, the concentration of said metal of the same kind increasing with increasing depth from the surface, and wherein said surface and its vicinity is substantially formed of a metal mixture which is expressed by the following general formula (I): [TiO 2 ] x [TiM y ] 1-x or [TiO 2 ] x M 1-x (where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni and Co; x ist such that 0.3 ≤ x < 1; and y is and integer peculiar to said metal M combining with Ti and is any one of 1, 2, and 3), and said inner portion is a metal mixture which is expressed by the following general formula (II): [Ti] x [TiM y ] 1-x or [Ti] x M 1-x (where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni, and Co; x is such that 0.3 ≤ x < 1; and y is an integer peculiar to said metal M combining with Ti and is any one of 1, 2, and 3). An architectural material according to claim 2, wherein said surface and its vicinity are substantially formed of a metal mixture including titanium oxide and palladium, and said inner portion is substantially formed of a metal mixture including titanium and palladium, and said surface and its vicinity as well as said inner portion being formed continuously. An architectural material according to claim 1, wherein said metal oxide (50) is at least one compound selected from the group consisting of titanium dioxide, iron oxide, silver oxide, copper oxide, tungsten oxide, aluminum oxide, silicon oxide, zinc oxide, and strontium titanate. A method of manufacturing an architectural material, comprising the steps of: fabricating a metal mixture including a metal constituting a metal oxide (50) exhibiting photocatalytic activity and a second metal (54) for improving the photocatalytic activity of said metal oxide; processing said metal mixture into a desired shape; and subjecting said processed metal mixture to oxidation treatment. A method of manufacturing an architectural material according to claim 5, wherein said metal constituting said metal oxide exhibiting the photocatalytic activity is selected from the group consisting of titanium, iron, silver, copper, aluminum, tungsten, zinc, and strontium. A method of manufacturing an architectural material according to claim 5, wherein said second metal for improving the photocatalytic activity of said metal oxide is selected from the group consisting of platinum, gold, palladium, silver, copper, nickel, rhodium, niobium, tin, and cobalt. A method of manufacturing an architectural material according to claim 5, wherein, said metal mixture is expressed by the following general formula II): [Ti] x [TiM y ] 1-x or [Ti] x M 1-x where M represents a metal selected from the group consisting of Pt, Au, Pd, Ag, Cu, Ni, and Co; x is such that 0.3 ≤ x < 1; and y is an integer peculiar to said metal M combining with Ti and is any one of 1, 2, and 3. A method of manufacturing an architectural material according to claim 5, wherein a metal mixture including titanium and palladium is fabricated, and after said metal mixture is formed into a desired shape, said metal mixture is subjected to anodic oxidation treatment. A method of manufacturing an architectural material according to claim 5, wherein a metal mixture including titanium and palladium is fabricated, and after said metal mixture is formed into the shape of a thin film, said metal mixture is subjected to anodic oxidation treatment, and is bonded to the surface of a desired architectural material.

Inventors: FUJISHIMA AKIRA, HASEGAWA TAMOTSU, HASHIMOTO KAZUHITO, OGAWA TAKATOSHI, SAITO TOSHIO, TSUBOUCHI NOBUO, YOSHIOKA YASUHIKO, FUJISHIMA, AKIRA, HASEGAWA, TAMOTSU, HASHIMOTO, KAZUHITO, OGAWA, TAKATOSHI, SAITO, TOSHIO, TSUBOUCHI, NOBUO, YOSHIOKA, YASUHIKO, Hasegawa, Tamotsu, c/o Technical Laboratory of, Ogawa, Takatoshi, c/o Technical Laboratory of, Saito, Toshio, c/o Technical Laboratory of, Tsubouchi, Nobuo, c/o Technical Laboratory of, Yoshioka, Yasuhiko, c/o Technical Laboratory of
Applicants: TAKENAKA CORP, TAKENAKA CORPORATION
Application year: 1993
Main classification: E04C2
IPC codes: C04B41, B01D53, E04C1, C03C17, E04C2, C25D11, E04B2