초록 ▼

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

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.

대표청구항 ▼

What is claimed is: 1. A glass composition comprising the following glass ingredients: 60.2 to 70% by weight of SiO2; 1 to 20% by weight of Al2O3; B2O3, wherein the B2O3 is present in an amount up to 10%; SiO2+Al2O3+B2O3 accounting for 61.2 to 90% by weight; a total of 3.0 to 15% by weight of R2O c

What is claimed is: 1. A glass composition comprising the following glass ingredients: 60.2 to 70% by weight of SiO2; 1 to 20% by weight of Al2O3; B2O3, wherein the B2O3 is present in an amount up to 10%; SiO2+Al2O3+B2O3 accounting for 61.2 to 90% by weight; a total of 3.0 to 15% by weight of R2O compounds, where R=Li, Na, and K, wherein the following condition is fulfilled: 0.1% ≦Na2O<6%; 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 LnxOyrepresents at least one compound selected from the group consisting of lanthanoid metal oxides, Y2O3, Nb2O5, and Ta2O5, wherein the glass composition does not include CaO and the following condition is fulfilled: 0.070<(total content of R′O compounds)/(SiO2+Al2O3+B2O3)<0.200. 2. A glass composition as claimed in claim 1, wherein the following condition is further fulfilled: 0.10<Al2O3/(SiO2+Al2O3+B2O3)<0.35. 3. A glass composition as claimed in claim 1, wherein the following condition is further fulfilled: Al2O3/B2O3>2.0. 4. A glass composition as claimed in claim 1, wherein the following condition is further fulfilled: 0.50<(total content of R′O compounds)/MOx<5.00. 5. A glass substrate for an information recording medium, the glass substrate comprising the following glass ingredients: 60.2 to 70% by weight of SiO2; 1 to 20% by weight of Al2O3; B2O3, wherein the B2O3 is present in an amount up to 10%; SiO2+Al2O3+B2O3 accounting for 61.2 to 90% by weight; a total of 3.0 to 15% by weight of R2O compounds, where R=Li, Na, and K, wherein the following condition is fulfilled: 0.1%≦Na2O<6% 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, wherein the glass substrate does not include CaO and the following condition is fulfilled: 0.070<(total content of R′O compounds)/(SiO2+Al2O3+B2O3)<0.200. 6. A glass substrate as claimed in claim 5, wherein the glass substrate has: a specific elastic modulus E/ρ of 33 or higher; a Vickers hardness Hv in a range of from 550 to 675; alkali elution A of 200 ppb or lower per 2.5-inch disk; Si elution S of 500 ppb or lower per 2.5-inch disk; a fracture toughness Kc of 0.85 MPa/m1/2 or greater; and a glass transition temperature Tg of 550° C. or lower. 7. A glass substrate as claimed in claim 6, wherein the following conditions are fulfilled: Tg/Hv>0.85; Tg×Kc>500, Tg×Kc/Hv>0.80. 8. An information recording medium having an information recording layer formed on a glass substrate as claimed in claim 5. 9. A glass composition as claimed in claim 1, wherein the glass composition comprises 0.5% to 10% by weight of B2O3. 10. A glass substrate as claimed in claim 5, wherein the glass substrate comprises 0.5% to 10% by weight of B2O3. 11. A glass composition as claimed in claim 1, wherein the glass composition comprises 0.1% to 3.9% by weight of Na2O. 12. A glass substrate as claimed in claim 5, wherein the glass substrate comprises 0.1% to 3.9% by weight of Na2O. 13. A glass composition as claimed in claim 1, wherein the following conditions are further fulfilled: 0.080<(total content of R′O compounds)/(SiO2+Al2O3+B2O3)<0.180; 0.15<Al2O3/(SiO2+Al2O330 B2O3)<0.25. 14. A glass substrate as claimed in claim 5, wherein the following conditions are further fulfilled: 0.080<(total content of R′O compounds)/(SiO2+Al2O3+B2O3)<0.180; 0.15<Al2O3/(SiO2+Al2O3+B2O3)<0.25.