[19a-PA4-1~13] 3.7 Laser processing

[19a-PA4-5] Crack suppression of silica glass film formed by F₂ laser induced photochemical surface modification of hard silicone coating film on polycarbonate

〇Hidetoshi Nojiri¹, Masayuki Okoshi² (1.RENIAS, 2.National defense academy)

Keywords:silicone, F2 laser, photochemical modification

Light-weighing of Zero emission vehicle is now strongly required for reducing electricity consumption. Transparent polycarbonate with hard silicone coating film has been used as a low density material of automotive windows. But more hardened surface with scratch resistant has been desired. Previously, we have found that the surface of silicone protective film coated on a polycarbonate resin could be photo-chemically modified into carbon-free silica (SiO₂) by irradiation of a 157 nm F₂ laser. Moreover, crack resistance was improved using mesh mask in the F₂ laser irradiation. In this study, crack suppression method for the thermal durability was considered. In experimentation, photo-chemically modified SiO₂ samples were prepared by F₂ laser irradiation to the surface of hard silicone film coated onto a polycarbonate substrate. Then, F₂ laser was irradiated using mesh mask with one of several type apertures. Next, thermal test at 100 or 120℃ for 3 h was executed on samples to investigate crack resistance in detail. Then many cracks were observed on the boundary between irradiation and non-irradiation area. It was thought that crack was easily occurred by elongation of silicone at the high temperature because of strong tensile stress generated at the boundary surface. We tried to rubbing the modified surface in each orthogonal direction by steel wool to reduce the stress at the modified surface. Then no crack was obtained at all after thermal test at 120℃ 3h.