| 摘要 |
A glass substrate used as a substrate of an information recording medium such as a magnetic disk, magneto-optical disk, DVD, or MD, and a glass composition used to make such a glass substrate, contains the following glass ingredients: 40 to 70% by weight of SiO2; 1 to 20% by weight of Al2O3; 0 to 10% by weight, zero inclusive, of B2O3; SiO2+Al2O3+B2O3 accounting for 60 to 90% by weight; a total of 3.0 to 15% by weight of R2O compounds, where R=Li, Na, and K; a total of 2.0 to 15% by weight of R′O compounds, where R=Mg, and Zn; and a total of 1.0 to 20% by weight of MOx (TiO2+ZrO2+LnxOy), where LnxOy represents at least one compound selected from the group consisting of lanthanoid metal oxides, Y2O3, Nb2O5, and Ta2O5. Here, the following condition is fulfilled: 0.070<(total content of R′O compounds)/(SiO2+Al2O3+B2O3)<0.200.
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