METHOD FOR CHEMICALLY STRENGTHENED GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM

摘要

PROBLEM TO BE SOLVED: To provide a method for chemically strengthening a glass substrate for an information recording medium by which the strength of the glass substrate after chemical strengthening treatment is maintained even when the chemical strengthening of the glass substrate is repeated and a glass substrate having stable quality is obtained. SOLUTION: The glass substrate 11 is immersed into a chemical strengthening processing liquid 14 in the state where a plurality of glass substrates are located in a line. When Li<+> and Na<+> existing in the vicinity of the surface of the glass substrate 11 are contained in the processing liquid 14, Li<+> and Na<+> is ionically exchanged for monovalent metal ions having larger ionic radius than that of Li<+> or Na<+> , thereby the glass substrate 11 is chemically strengthened. The amount of the processing liquid 14 between glass substrates 11 opposite to each other is preferably within a range of 1.4 to 71 g/cm<2> with respect to the surface area of the glass substrate 11. When a Li<+> concentration in the processing liquid 14 reaches a range of 0.07 to 0.09 wt.% preferably, the processing liquid 14 is replaced by a new processing liquid 14.