Patent ID: 6951692

Claim:
An information carrying substrate applicable to a surface of a product for authenticating the product, said substrate comprising 50 to 99.999% by weight of a film forming material, 0.001 to 5% by weight of a photo-switchable fluorescent compound uniformly dispersed in said film forming material, the photo-switchable fluorescent compound possessing strong solid state fluorescence in the presence of ultraviolet light and having the general formula: wherein R 1 and R 2 are substituted phenyl groups and n=2 to 3, and wherein the photo-switchable fluorescent compound fluoresces reversibly in the presence of light at a wavelength in the range of 390 to 700 nm and amplitude below 0.5 mJ/pulse and is rendered substantially non-fluorescent in the presence of ultraviolet light upon irradiation by light at a wavelength in the range of 390 to 700 nm and amplitude above 2 mJ/pulse.