Patent ID: 8806895
Filing Date: 2014-08-19
Classification: C03B,C03C

Abstract:
1. A manufacturing method of a sheet glass material for a magnetic disk including a pair of principal surfaces, the method comprising: performing a cutting process to cut molten glass to cause a lump of molten glass to drop; and performing a pressing process to form a sheet glass material by performing press forming on the lump of molten glass such that the lump of molten glass extends along flat inner surfaces of a pair of dies disposed along both sides of the dropping path by sandwiching the dropping lump of molten glass between the inner surfaces of the pair of dies at the substantially the same timing, the pair of dies facing each other and being set to substantially the same temperature, the molten glass being cut during the cutting process such that the lump of molten glass is shorter in a parallel direction to the inner surfaces than the sheet glass material is after being formed, and the molten glass being cut during the cutting process such that the lump of molten glass drops down while revolving around its dropping axis, and the cutting process is such that a revolving speed of the lump of molten glass is controlled.