Photocatalytic method for making a surface hydrophilic, and composite material having a photocatalytic hydrophilic surface

摘要

A process of making the surface of a substrate hydrophilic by photocatalysis. A substrate is covered with a photocatalytic titania coating (10) which carries on its surface a solid acid increasing the hydrogen bond component (.gamma.sh) of the surface energy at the solid-liquid boundary. On photoexcitation of the photocatalyst, the hydrogen bond component (.gamma.sh) is increased by photocatalysis to thereby accelerate the physical adsorption of atmospheric water molecules on the hydrogen atoms of terminal OH groups (12) bonded to titanium atoms present on the surface and bridging OH groups (14) through hydrogen bonds (16). As a result of the adsorption, a highdensity physically adsorbed water layer (18) is formed on the surface of the photocatalytic coating (10) to thereby facilitate making the surface hydrophilic. This process is effective in the protection of articles from fogging or staining and the (self)cleaning of articles.