Patent ID: 7273668

Claim:
A glass substrate for magnetic recording media, having a circular outer shape in a plan view and comprising a glass composition, wherein the glass composition comprises, in terms of mass %: 59 to 68% of SiO 2 ; 9.5 to 15% of Al 2 O 3 ; 0 to 1% of Li 2 O; 3 to 18% of Na 2 O; 0 to 3.5% of K 2 O; 0 to 15% of MgO; 1 to 15% of CaO; 0 to 4.5% of SrO; 0 to 1% of BaO; 0 to 2% of TiO 2 ; and more than 1% but not more than 10% of ZrO 2 .