Preparation and characterization of organic layers for UV protection of polycarbonate

In many applications, polycarbonate surfaces need to be coated as a protection against abrasion and decomposition caused by weathering. In particular, UV radiation during exposure to sunlight degrades polycarbonate, which causes delamination of the protective layer. To avoid coating delamination, the layer itself needs an absorption edge near 400 nm. One option is to use UV-absorbing organic molecules. The aim of the present study was to develop UV-protective layer stacks containing suitable organic molecules deposited in a vacuum process, with a focus on the stability of UV-absorbing organic layers during UV irradiation and their optical properties. The commercial UV absorber Tinuvin™ 360 and the organic compound N,N′-di(naphth-1-yl)-N,N′-diphenyl-benzidine were used. Thin layers of the organic materials were evaporated thermally. The optical properties and UV stability were investigated using UV-VIS and infrared spectroscopy.