Crack Suppression of Transparent Protective Layer on Polycarbonate Formed by Fluorine Laser

Abstract

A transparent, hard silica glass (SiO₂) layer was formed on a conventional protective coat made of silicone ([SiO(CH₃)₂]_n) on a polycarbonate plate by the 157 nm fluorine (F₂) laser-induced photochemical modification of silicone into SiO₂. Long exposure of the F₂ laser to the sample produced cracks on the surface; a metallic mesh mask was set on the sample during F₂ laser irradiation to suppress the cracks successfully. As a result, the thickness of the formed SiO₂ layer could increase to approximately 1.3 µm without any crack, and the hardness of the sample also increased to approximately 2.8 GPa.