Investigation of vacuum deposited hybrid coatings of protic organic UV absorbers embedded in a silica matrix used for the UV protection of Polycarbonate glazing

A study of vacuum-deposited organic–inorganic hybrid coatings for UV protection of polycarbonate is presented. UV-absorbing compounds, which are commonly used for polycarbonate, were embedded in a silica matrix by thermal co-evaporation under high vacuum. In addition to the optical properties of the coatings, the influence of the silica network on the organic UV absorber and the stability of the intramolecular hydrogen bond (IMHB) are discussed. A model is presented to show the interaction between the organic compound and the silica matrix. It could be shown with UV irradiation experiments that the hydroxyphenyltriazine compound exhibits higher UV stability in the hybrid coating than the hydroxybenzotriazoles.