| 摘要 |
PROBLEM TO BE SOLVED: To make a glass disk sufficiently withstand even to its daily use by ensuring its strength to an impact. SOLUTION: This glass disk 1 is a glass disk 1 having a center hole in a doughnut disk shape, and an inner peripheral surface 1b of the disk and an outer peripheral surface 1a of the disk are mirror-finished. By such a constitution, no crack will not be developed from its inner and outer peripheral edges even if the disk is subjected to some impact, thus the strength to the impact is substantially improved. |
