GLASS SUBSTRATE FOR INFORMATION RECORDING MEDIUM AND MAGNETIC DISK
A glass substrate for an information recording medium, comprising an alkali aluminosilicate glass, wherein the β—OH value is at least 0.20 mm −1 .
1 . A glass substrate for an information recording medium, comprising an alkali aluminosilicate glass, wherein the β—OH value is at least 0.20 mm −1 .
2 . The glass substrate for an information recording medium according to claim 1 , wherein the alkali aluminosilicate glass has an alkali metal oxide content of from 15 to 26 mol %.
3 . The glass substrate for an information recording medium according to claim 1 , wherein the alkali aluminosilicate glass comprises, as represented by mol % based on the following oxides, from 64 to 67% of SiO 2 , from 8 to 10% of Al 2 O 3 , from 10 to 13% of Li 2 O, from 9 to 12% of Na 2 O, from 0 to 2% of K 2 O and from 2 to 4% of ZrO 2 , provided that the total content of Li 2 O, Na 2 O and K 2 O is from 21 to 25%.
4 . The glass substrate for an information recording medium according to claim 1 , wherein the β—OH value is at least 0.30 mm −1 .
5 . A magnetic disk comprising the glass substrate for an information recording medium as defined in claim 1 , and a magnetic recording layer formed on the glass substrate.