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

SUMMARY 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.