Glass composition and glass substrate
AssigneeMinolta Co., Ltd.
InventorsHideki Kawai, Toshiharu Mori
Life of this patent
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Abstract
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 15% by weight, zero inclusive, of B2O3; SiO2+Al2O3+B2O3 accounting for 65 to 90% by weight; a total of 7 to 20% by weight of R2O compounds, where R=Li, Na, and K; and a total of 0 to 12% by weight, zero inclusive, of R′O compounds, where R′=Mg, Ca, Sr, Ba, and Zn. Moreover, the following conditions are fulfilled: B2O3=0% by weight, or Al2O3/B2O3≧1.0; and (SiO2+Al2O3+B2O3)/(the total of R2O compounds+the total of R2O compounds)≧3.
Claims14
A glass composition comprising the following glass ingredients:
- 45 to 75% by weight of SiO2;
- 10.1 to 14.6% by weight of Al2O3;
- 1.2 to 5.7% by weight of B2O3;
- SiO2+Al2O3+B2O3 accounting for 65 to 90% by weight;
- a total of 7 to 12.8% by weight of R2O compounds, where R=Li, Na, and K;
- and
- a total of 0% by weight of R′O compounds, where R′=Mg, Ca, Sr, Ba, and Zn;
- and
- a total of 0 to 7.1% 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,
- wherein the following conditions are fulfilled:
- Al2O3/B2O3≧1.0;
- and
- 7.78≧(SiO2+Al2O3+B2O3)/(the total of R2O compounds ≧3.
A glass substrate formed of a glass composition comprising the following glass ingredients:
- 45 to 75% by weight of SiO2;
- 10.1 to 14.6% by weight of Al2O3;
- 1.2 to 5.7% by weight of B2O3;
- SiO2+Al2O3+B2O3 accounting for 72 to 90% by weight;
- a total of 7 to 12.8% by weight of R2O compounds, where R=Li, Na, and K;
- a total of 0% by weight of R′O compounds, where R′=Mg, Ca, Sr, Ba, and Zn;
- and
- a total of 0% to 7.1% 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,
- wherein the following conditions are fulfilled:
- Al2O3/B2O3≧1.0;
- and
- 7.78≧(SiO2+Al2O3+B2O3)/(the total of R2O compounds≧3.
Dependencies are inferred from the claim text.