Patent ID: 7803472

Claim:
A substrate glass for data storage medium, comprising as represented by mass %: from 47 to 60% of SiO 2 ; from 8 to 20% of Al 2 O 3 ; from 0 to 8% of MgO; from 2.0 to 6% of CaO; from 1 to 18% of SrO; from 0 to 13% of BaO; from 2.8 to 6% of TiO 2 : from 1 to 5% of ZrO 2 ; from 2 to 8% of Na 2 O and from 1 to 15% of K 2 O; wherein a glass transition temperature of the substrate glass is at least 680° C., and a mol % of SiO 2 is at least 59 mol %.