Industrial processing of TiO2 thin films from soluble precursor powders

Soluble, amorphous powders were prepared as precursors for the sol-gel processing of TiO2 films. Layers of up to 800 nm and 2.0 mum were prepared on borosilicate glass and Ni-alloy by multiple coating, respectively A refractive index of 2.3 was achieved. The interdependency of parameters such as solvent composition, withdrawal rate, thermal treatment with film quality, thickness and optical properties was investigated. The conditions were optimized for large-area coatings on an industrial scale. The overall process is highly advantageous for industrial production of optical interference filters due to the long-time stability of precursor powders and sots, high optical quality of the resulting films, excellent substrate adhesion and good compatibility with other sol-gel films.