Patent ID: 8916487

Claim:
A glass substrate for an information recording medium, comprising the following glass components in % by weight: SiO 2 : 52 to 67%; Al 2 O 3 : 8 to 20%; B 2 O 3 : 0 to 6% (including zero); (wherein FMO=SiO 2 +Al 2 O 3 +B 2 O 3 =70 to 85%); Li 2 O: 0.5 to 4%; Na 2 O: 1 to 8%; K 2 O: 0 to 5% (including zero); (wherein R2O=Li 2 O+Na 2 O+K 2 O=5 to 15%); MgO: 2 to 9%; CaO: 0.1 to 5%; BaO: 0 to 3% (including zero); SrO: 0 to 3% (including zero); ZnO: 0 to 5% (including zero); (wherein MgO+CaO+BaO+SrO+ZnO=5 to 15%); Y 2 O 3 : 0 to 4% (including zero); La 2 O 3 : 0 to 4% (including zero); Gd 2 O 3 : 0 to 4% (including zero); CeO 2 : 0 to 4% (including zero); TiO 2 : 1 to 7%; HfO 2 : 0 to 2% (including zero); ZrO 2 : 0 to 5% (including zero); Nb 2 O 5 : 0.2 to 5%; and Ta 2 O 5 : 0 to 5% (including zero); and satisfying the following composition relation formulas (1) to (4): Li 2 O/R2O:0.05 to 0.35 (1), Li 2 O/FMO:0.005 to 0.035 (2), Li 2 O/(MgO+ZnO):less than 2 (3) and Nb 2 O 5 /SiO 2 :0.01 to 0.075 (4).