Sidley Austin LLP
Glass composition and glass substrate
A glass substrate for use as the substrate of an information recording medium such as a magnetic disk, magneto-optical disk, DVD, or MD or of an optical communication device, and a glass composition for making such a glass substrate, contains the following glass ingredients: 45 to 75% by weight of SiO2; 1 to 20% by weight of Al2O3; 0 to 8% by weight, zero inclusive, of B2O3; SiO2+Al2O3+B2O3 accounting for 60 to 90% by weight; a total of 0 to 20% by weight, zero inclusive, of R2O compounds, where R=Li, Na, and K; and a total of 0 to 15% by weight, zero inclusive, of TiO2+ZrO2+LnxOy, where LnxOy represents at least one compound selected from the group consisting of lanthanoid metal oxides, Y2O3, Nb2O5, and Ta2O5.
Minolta Co., Ltd.
C C
C03C C03C
inventional inventional
Hideki Toshiharu
Kawai Mori