Patent ID: 6949485

Claim:
A glass substrate for a data storage medium, which consists essentially of: in terms of weight percent SiO 2 40 to 59%, Al 2 O 3 5 to 20%, B 2 O 3 0 to 8%, MgO 0 to 10%, CaO 0 to 12%, SrO 10.6 to 20%, BaO 0 to 2%, ZnO 0 to 4%, Li 2 O 0 to 2%, Na 2 O 0 to 10%, K 2 O 0 to 8%, TiO 2 2 to 10%, and ZrO 2 0 to 5%, wherein MgO+CaO+SrO+BaO is at least 15%; Al 2 O 3 +TiO 2 is at least 13%; TiO 2 +ZrO 2 is at least 2.3%; and which has an average linear expansion coefficient of at least 70×10 −7 /° C. within the range of 50 to 350° C., wherein the glass has a glass transition temperature of at least 600° C., and wherein the number of attachments having sizes ranging from 1 μm to less than 10 μm present on the surface of the glass substrate held in a steam atmosphere at 120° C. under 2 atm for 20 hours, is not more than 5×10 4 /cm 2 .