Organic layer for UV protection of polycarbonate

Polycarbonate has to be coated for outdoor applications. The coating increases the mechanical resistance and acts as protection against UV degradation. The layer needs an absorption edge near 400 nm to avoid delamination of the coating. Common inorganic oxide layers do not fulfill this requirement adequately. An alternative is the use of UV-absorbing organic molecules. The aim of the present study was to develop UV-protective layer stacks containing suitable organic molecules. The focus is on the stability of UV-absorbing organic layers during UV irradiation and their optical characterization. Typical commercially available UV absorbers like TinuvinTM 360 and TinuvinTM 1577, but also other organic compounds with a suitable absorption edge like ?-NPD were used. Thin layers of the organic materials were evaporated thermally. Optical characterization and the investigation of UV stability were done by UV-VIS and infrared spectroscopy methods.