Patent ID: 8480454

Claim:
A method for manufacturing a glass substrate for a magnetic disk, the manufacturing method comprising: a polishing step for polishing a disk-shaped glass plate made of a multi-component glass material containing silicon oxide to form a polished smooth surface; a pre-grinding washing step for washing the polished smooth surface of the glass plate with an acid solution followed by an alkaline solution to form an altered surface layer having an controlled thickness on an inner portion of the glass plate, an ingredient ratio of silicon oxide in the altered surface layer being different from that in the inner portion; a grinding step for using abrasion grains to grind the altered surface layer formed in the pre-grinding washing step such that the altered layer having a thickness less than the controlled thickness remains on the inner portion; subsequent to the grinding step, a post-grinding washing step for washing the glass plate with a neutral or alkaline washing liquid to remove a remaining portion of the altered surface layer.