Study on Wear Resistance and Surface Modification of Silicone Hard Coats by Vacuum Ultraviolet Light Irradiation

The practical application of plastic glazing, intended for replacing inorganic glass with polycarbonate, is being explored for weight reduction of automobile bodies. Using vacuum ultraviolet （VUV） light irradiation from an excimer lamp, Nojiri and others developed a technique for forming a SiO2-based modified layer on the surface of a silicone hard coat over polycarbonate. This study assessed the relation between wear resistance and surface composition of two commercially available silicone hard coats, samples A and B, before and after VUV irradiation. According to the Taber abrasion test for compliance with ASTM D1044 standards, the wear resistance of sample A improved with VUV irradiation, meeting the criteria for a front window, whereas sample B deteriorated. Fourier transform infrared spectra peaks related to Si-O stretching vibrations were decomposed into inorganic glass and organic silicone components, revealing that the inorganic glass ratios in sample A were approximately 40% - 47%, whereas those of sample B exceeded 49%. Correlation was confirmed between the wear resistance and the inorganic glass ratio, which is expected to be approximately 41% - 48% after VUV irradiation to satisfy wear resistance criteria for a front window.