(EP861805-A1)      A production process for a titanium oxide thin film comprises immersing a substrate in an aqueous solution containing at least one fluorotitanium complex compound and seed crystals for making a titanium oxide thin film, in the presence of a fluoride ion scavenger, to form a titanium oxide thin film on the substrate surface.    Pref. the fluorotitanium compound is 0.01 - 0.04) M; the scavenger is 10-4 - 3000 wt.% w.r.t. fluoride ions in solution; all or part of the fluorotitanium compound is obtained by reaction of Ti oxide with HF; the fluorotitanium compound is at least one from H2TiF6, (NH4)2TiF6, Na2TiF6, K2TiF6, Rb2TiF6 and Cs2TiF6; and the scavenger is a boron compound, Al chloride, NaOH or aqueous ammonia.    USE -   For photodecomposition catalysts (claimed), such as for organic compound or nitrogen oxide compound photodecomposition reactions; solar cells; optical lens coatings; household purification equipment; and industrial waste water processing.    ADVANTAGE -   A highly homogenous thin film having fastness, excellent corrosion resistance, high refractive index and photocatalytic activity is formed using simple equipment. Since there is no thermal processing, a wide range of substrates can be used.    (JP10507827-X)      A production process for a titanium oxide thin film comprises immersing a substrate in an aqueous solution containing at least one fluorotitanium complex compound and seed crystals for making a titanium oxide thin film, in the presence of a fluoride ion scavenger, to form a titanium oxide thin film on the substrate surface.    Pref. the fluorotitanium compound is 0.01 - 0.04) M; the scavenger is 10-4 - 3000 wt.% w.r.t. fluoride ions in solution; all or part of the fluorotitanium compound is obtained by reaction of Ti oxide with HF; the fluorotitanium compound is at least one from H2TiF6, (NH4)2TiF6, Na2TiF6, K2TiF6, Rb2TiF6 and Cs2TiF6; and the scavenger is a boron compound, Al chloride, NaOH or aqueous ammonia.    USE -   For photodecomposition catalysts (claimed), such as for organic compound or nitrogen oxide compound photodecomposition reactions; solar cells; optical lens coatings; household purification equipment; and industrial waste water processing.    ADVANTAGE -   A highly homogenous thin film having fastness, excellent corrosion resistance, high refractive index and photocatalytic activity is formed using simple equipment. Since there is no thermal processing, a wide range of substrates can be used.    (US6066359-A)      A production process for a titanium oxide thin film comprises immersing a substrate in an aqueous solution containing at least one fluorotitanium complex compound and seed crystals for making a titanium oxide thin film, in the presence of a fluoride ion scavenger, to form a titanium oxide thin film on the substrate surface.    Pref. the fluorotitanium compound is 0.01 - 0.04) M; the scavenger is 10-4 - 3000 wt.% w.r.t. fluoride ions in solution; all or part of the fluorotitanium compound is obtained by reaction of Ti oxide with HF; the fluorotitanium compound is at least one from H2TiF6, (NH4)2TiF6, Na2TiF6, K2TiF6, Rb2TiF6 and Cs2TiF6; and the scavenger is a boron compound, Al chloride, NaOH or aqueous ammonia.    USE -   For photodecomposition catalysts (claimed), such as for organic compound or nitrogen oxide compound photodecomposition reactions; solar cells; optical lens coatings; household purification equipment; and industrial waste water processing.    ADVANTAGE -   A highly homogenous thin film having fastness, excellent corrosion resistance, high refractive index and photocatalytic activity is formed using simple equipment. Since there is no thermal processing, a wide range of substrates can be used.