| 摘要 |
PROBLEM TO BE SOLVED: To obtain a high strength glass substrate without requiring chemical strengthening by coating the end face of a glass substrate from which flaws, which influence on mechanical strength is removed by etching treatment, with a protective film comprising a silica layer of cured material of a coating composition containing polysilazane and having a specific hardness. SOLUTION: A glass raw plate having a composition corresponding to uses is cut into a prescribed size and the end face is subjected to beveling and fish processing with grinding stone, etc. and as necessary, main surface is polished to improve the flatness. The end face of the glass substrate is subjected to etching treatment with fluorosulfuric acid, etc., so as to remove >=15μm deep injury which exist on the end face controlling flexural strength as much as possible. A protective film having a hardness of >=5 H scratch value of pencil is applied onto the end face of the substrate subjected to etching treatment. A silica layer which is the cured product of a coating composition containing polysilazane is preferable as the protective film. The protective film is formed by applying the coating composition to the end face and heat-curing the composition. The protective film attached to main surface is preferably polished and removed.
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