Patent ID: 8613206
Filing Date: 2013-12-24
Classification: C03C,G11B

Abstract:
1. A method for manufacturing a glass substrate for a magnetic disk, comprising: a chemical strengthening step of bringing a glass substrate into contact with a heated chemical strengthening salt melted liquid and chemically strengthening a surface layer of said glass substrate at a desired temperature, and a cooling step of cooling said glass substrate having undergone said chemical strengthening step, wherein in said cooling step, the temperature of said glass substrate is lowered to a room temperature, without crystallizing said chemical strengthening salt in said chemical strengthening salt melted liquid adhered to a surface of said glass substrate, wherein the glass substrate is an aluminosilicate glass substrate, wherein after said cooling step, a maximum value of waves in the surface of the glass substrate is kept to a maximum value of 5 nm or below when measuring waves having a frequency corresponding to a wavelength of 4 μm to 1 mm within a rectangle region having side lengths of 800 μm and 980 μm, wherein said cooling step comprises a first cooling treatment in which said glass substrate is brought into contact with a first treatment liquid, and a second cooling treatment or second and latter cooling treatments in which said glass substrate is brought into contact (sequentially) with at least one treatment liquid including a second treatment liquid or of second and latter treatment liquids after said first cooling treatment; wherein said first treatment liquid used in said first cooling treatment is regulated to a temperature which is below a temperature of said chemical strengthening salt melted liquid in said chemical strengthening step and which is above a solidification temperature of said chemical strengthening salt; and wherein said second or latter treatment liquid used in said second or latter cooling treatment is regulated to a temperature which is below a temperature of the precedent-stage treatment liquid used in the cooling treatment carried out precedent to the cooling treatment in consideration.