| 摘要 |
<p><P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a glass blank with a center hole by which processing of the center hole can be easily implemented and a substrate for information recording mediums is produced with sufficient productivity. <P>SOLUTION: The method of manufacturing a glass blank with the center hole from disc-like sheet glass uses as a disc-like sheet glass, the sheet glass in a high temperature state, having a center wall thickness section at a part in which the center hole is to be prepared, a peripheral wall thinness section with wall thickness thinner than the center wall thickness section at a periphery of the center wall thickness section, and also a level difference at a boundary of the center wall thickness section and the peripheral wall thinness section. An annular crack is generated along with the above level difference by rapid cooling of the above whole sheet glass and then, the center hole is formed. <P>COPYRIGHT: (C)2004,JPO</p> |
