Patent ID: 7964298

Claim:
A substrate of an information recording medium comprising: a disk, said disk being adapted to receive on a surface thereof plural layers including a recording layer and comprising a glass suitable for chemical reinforcement, wherein said glass has a composition comprising, denoted as mol %: SiO 2 50%-67% Al 2 O 3 2%-10% (where the total of SiO 2 and Al 2 O 3 is 57%-79%) CaO 3-20% BaO 1%-14% Na 2 O 1%-8% K 2 O greater than 0% to 13% (where the total of Na 2 O and K 2 O is 5%-14%) ZrO 2 1%-10% MgO 0 to 10% SrO 0%-10% (where the ratio of the content of CaO to the total of MgO, CaO, SrO, and BaO is greater than or equal to 0.5) ZnO 0%-8% (where the total of MgO, CaO, SrO, BaO, and ZnO is 4%-30%) TiO 2 0%-8% and the total content of the above-stated components is greater than or equal to 95%, and where the glass does not comprise Li 2 O.