The hydrophilicity of the SiO2(top)/TiO2(under) double layer films prepared by vacuum evaporation was investigated. The as-deposited SiO2/TiO2 double layer films showed very good hydrophilicity (water contact angle: similar to 0 degrees). Their hydrophilicity, however, is deteriorated by the organic contamination adsorbed on the film but the hydrophilicity can be recovered by UV light irradiation. TOF-SfMS (time-of-flight secondary-ion-mass-spectrometry) measurements revealed that the amount of organic compounds adsorbed oil the films decreased with the UV light irradiation. Secondarily, the amount of both Si-OH and Ti-OH groups changed little by the UV light irradiation. Thus, it can be concluded that the hydrophilicity of the SiO2/TiO2 double layer films is due to the stable Si-OH groups and the photo-catalytic TiO2 underlayer maintains the hydrophilicity of the double layer films by decomposing organic contaminants on the film surface. This SiO2/TiO2 double layer film has been in practical use for the automobiles' exterior rear view mirrors. (c) 2005 Elsevier B.V. All rights reserved.