| 摘要 |
PROBLEM TO BE SOLVED: To provide a method for manufacturing a glass blank for magnetic disk by a horizontal direct press method, capable of suppressing variation of flatness required for a main surface while obtaining the flatness, and a method for manufacturing a glass substrate for magnetic disk.SOLUTION: A method for manufacturing a glass blank for magnetic disk includes the press step of molding a glass blank by sandwiching a lump of molten glass with the press molding surfaces 52A and 62A of a pair of dies 50 and 60. In the press step, temperatures of the press molding surfaces 52A and 62A of the pair of dies 50 and 60 when sandwiching the lump of the melting glass by the press forming surfaces of the pair of the dies are equal to or more than the glass transition point of the molten glass and less than the yield point thereof, and press molding is performed using the dies 50 and 60 having 0.4 μm or more of the surface roughnesses Ra of the press molding surfaces 52A and 62A. |
