Optimized UV protecting coatings by combination of organic and inorganic UV absorbers

The ultraviolet (UV) protection of organic and biological materials against photodestruction is of high practical interest. Since protective coatings containing individual organic or inorganic UV absorbers contain absorption bands in different wavelengths regions below 400 nm, a combination of both types of absorbers can improve the UV protection functionality. Nowadays, the recent sol-gel technique enables the preparation of coatings from inorganic UV absorbers like TiO2 combined with embedded organic UV absorbers. The absorption behavior of these hybrid coatings on glass was investigated as function of layer thickness and concentration for two different organic UV absorbers (based on benztriazol and phenylacrylate). The optimization of the coating composition is supported by model calculations of the transmission spectra and allows the preparation of coatings with nearly perfect light absorption at λ < 400 nm.