Patent ID: 8357459

Claim:
A glass for use in a substrate for an information recording medium, which comprises SiO 2 ; Al 2 O 3 ; one or more alkali metal oxides selected from the group consisting of Li 2 O, Na 2 O and K 2 O; 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 ZrO 2 , HfO 2 , Nb 2 O 5 , Ta 2 O 5 , La 2 O 3 , Y 2 O 3 and TiO 2 ; wherein SiO 2 content is equal to or greater than 50 molar percent, and a total content of SiO 2 and Al 2 O 3 is equal to or greater than 70 molar percent; wherein a total content of said alkali metal oxides and said alkaline earth meal oxides is equal to or greater than 8 molar percent; wherein a molar ratio of the total content of said oxides to the total content of said alkali metal oxides and said alkaline earth metal oxides ((ZrO 2 +HfO 2 +Nb 2 O 5 +Ta 2 O 5 +La 2 O 3 +Y 2 O 3 +TiO 2 )/(Li 2 O+Na 2 O+K 2 O+MgO+CaO+SrO+BaO)) is equal to or greater than 0.035, wherein a total content of said oxides (ZrO 2 +HfO 2 +Nb 2 O 5 +Ta 2 O 5 +La 2 O 3 +Y 2 O 3 +TiO 2 ) is 0.3-1.5 molar percent; wherein a total content of MgO and CaO is 1-6 molar percent; and wherein a content of ZrO 2 is 0.3-1.5 molar percent.