Glass for use as substrate for information recording medium, substrate for information recording medium and information recording medium, and their production methods

摘要

According to one aspect of the present invention, provided is glass for use in substrate for information recording medium, which comprises, denoted as molar percentages, a total of 70 to 85 percent of SiO2 and Al2O3, where SiO2 content is equal to or greater than 50 percent and Al2O3 content is equal to or greater than 3 percent; a total of equal to or greater than 10 percent of Li2O, Na2O and K2O; a total of 1 to 6 percent of CaO and MgO, where CaO content is greater than MgO content; a total of greater than 0 percent but equal to or lower than 4 percent of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3 Y2O3 and TiO2; with the molar ratio of the total content of Li2O, Na2O and K2O to the total content of SiO2, Al2O3, ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 ((Li2O+Na2O+K2O)/(SiO2+Al2O3+ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) being equal to or less than 0.28. Further provided are the substrate for information recording medium, information recording medium and their manufacturing methods according to the present invention.

主权项

1. Glass for use in substrate for information recording medium, which comprises SiO2; Al2O3; one or more alkali metal oxides selected from the group consisting of Li2O, Na2O and K2O; one or more alkaline earth metal oxides selected from the group consisting of MgO, CaO, SrO and BaO; and one or more oxides selected from the group consisting of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2;
wherein SiO2 content is equal to or greater than 50 molar percent, and the total content of SiO2 and Al2O3 is equal to or greater than 70 molar percent; both Li2O and Na2O are contained; Li2O content is within a range of 4.3 molar percent to 15 molar percent; Na2O content is within a range of 5 molar percent to 15 molar percent; the total content of the alkali metal oxides and the alkaline earth metal oxides is equal to or greater than 10 molar percent; the molar ratio of the total content of ZrO2, HfO2, Nb2O5, Ta2O5, La2O3, Y2O3 and TiO2 to the total content of the alkali metal oxides and the alkaline earth metal oxides ((ZrO2+HfO2+Nb2O5 +Ta2O5+La2O3+Y2O3+TiO2)/(Li2O+Na2O+K2O+MgO+CaO+SrO+BaO)) is equal to or greater than 0.035; MgO content is less than 3 molar percent, CaO content is equal to or less than 4 molar percent, and the molar ratio of MgO content to CaO content (MgO/CaO) ranges from 0.227 to 0.727; and the molar ratio of ZrO2 content to the total content of ZrO2, HfO2, Nb2O5,Ta2O5, La2O3, Y2O3 and TiO2 (ZrO2/(ZrO2+HfO2+Nb2O5+Ta2O5+La2O3+Y2O3+TiO2)) ranges from 0.5 to 1.