Patent ID: 7939187

Claim:
An article comprising a substrate and an apatite film having photocatalytic activity applied thereon, which is produced by a method comprising: preparing a liquid mixture comprising a Ca-containing compound and a P-containing compound; subjecting the liquid mixture to reaction to prepare an apatite-precursor composition; applying the apatite-precursor composition to the substrate; and drying the applied apatite-precursor composition, in which an of the apatite film is represented by Ax(BO y )zX 8 ·n(H 2 O), where A includes Ca and may also include at least one of Ti, Sr, Ba, Pb, Na, K, Y, Ce, Co, Ni, Cu, Al, La, Cr, Fe and Mg; B includes P and may also include at least one of S, V, Si and As; X includes at least one element selected from the group consisting of F, Cl, OH and O; y is a value determined by a valency of B; x, z and s are values determined by the valencies of A, (BO y ) and X, respectively; n is in a range of 0-20, and all or a part of A, (BO y ) and X may be replaced with other ions, so long as the apatite film is formed, the apatite film shows light transmittance of at least 85% and a light reflectance of no more than 15% at wavelengths of 400-700 nm, when determined on a light-transmitting material consisting of the film and the substrate, and the apatite film has an angle of contact with water within the range of 30-60°, and a change in the angle of contact with water induced by light irradiation at 3 mW/cm 2 for 700hours is within 5°; and in which the apatite film has an adsorbing capacity evidenced by a generation of more than 200 ppmv/hr of carbon dioxide from a surface area of 1 m 2 in an acetaldehyde decomposition test wherein carbon dioxide is produced with decomposition of acetaldehyde, and the acetaldehyde decomposition test is carried out by placing a sample of the apatite film in a closed vessel, introducing a saturated vapor of acetaldehyde, irradiating the sample with ultraviolet light, and quantitatively analyzing a gas in the vessel to determine a concentration of the residual acetaldehyde and produced carbon dioxide.