Effect of the addition of TiO2 to SiO2 films with concave-convex surface derived by the sol-gel method on film hardness and application to water-repellent glasses for automotive windows

Silica-titania films with a concave-convex surface were prepared from a mixture of polymerized tetraethoxysilane (TEOS) sol containing tetraisopropoxytitanate and polymerized methyltriethoxysilane (MTES) sol in a molar ratio MTES/TEOS of 6, Film hardness was dependent on the composition of the coating sol, heat treatment temperature and time. The film obtained by introduction of 4 mol% TiO2 to SiO2 and by heat treatment at 620 degrees C for 10 min was hard to be usable in engineering practice. New-type water-repellent glasses were produced by using these SiO2-TiO2 films as an under layer combined with fluoroalkylsilane; the glasses showed an abrasion resistance for practical application as automotive windows.