Glass for use in substrate for information recording medium, substrate for information recording medium and information recording medium, and their manufacturing method

A glass substrate for information recording medium,

• (1) which is comprised of glass comprising, denoted as mass percentages,
• 57 to 75 percent of SiO2;
• 5 to 20 percent of Al2O3, with the total content of SiO2 and Al2O3 being equal to or greater than 74 percent;
• a total of greater than 0 percent but equal to or less than 6 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2;
• greater than 1 percent but equal to or less than 9 percent of Li2O;
• 5 to 18 percent of Na2O, with the mass ratio, Li2O/Na2O being equal to or less than 0.5;
• 0 to 6 percent of K2O;
• 0 to 4 percent of MgO;
• greater than 0 percent but equal to or less than 5 percent of CaO, with the total content of MgO and CaO being equal to or less than 5 percent and CaO content being greater than MgO content;
• and
• a total of 0 to 3 percent of SrO and BaO, and
• (2) which has been subjected to chemical strengthening treatment, and has a hole in the center.

A glass substrate for information recording medium,

• (1) which is comprised of glass comprising, denoted as mass percentages, 57 to 75 percent of SiO2;
• 5 to 20 percent of Al2O3, with the total content of SiO2 and Al2O3 being equal to or greater than 74 percent;
• greater than 0 percent but equal to or less than 5.5 percent of ZrO2;
• greater than 1 percent but equal to or less than 9 percent of Li2O;
• 5 to 18 percent of Na2O, with the mass ratio, Li2O/Na2O being equal to or less than 0.5;
• 0 to 6 percent of K2O;
• 0 to 4 percent of MgO;
• greater than 0 percent but equal to or less than 5 percent of CaO, with the total content of MgO and CaO being equal to or less than 5 percent and CaO content being greater than MgO content;
• a total of 0 to 3 percent of SrO and BaO;
• and
• 0 to 1 percent of TiO2, and
• (2) which has been subjected to chemical strengthening treatment, and has a hole in the center.