초록 ▼

Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and a light weight and having high fracture toughness, the glass substrate having a fragility index value, measured in water, of 12 μm-1/2 or less or having a fragility index value, measured

Disclosed are a glass substrate for an information recording medium, having excellent scratch resistance and a light weight and having high fracture toughness, the glass substrate having a fragility index value, measured in water, of 12 μm-1/2 or less or having a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μm-1/2 or less, or the glass substrate comprising, by mol %, 40 to 75% of SiO2, 2 to 45% of B2O3 and/or Al2O3 and 0 to 40% of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K), wherein the total content of SiO 2, B2O3, Al2O3 and R'2O is at least 90 mol %, and a magnetic information recording medium comprising a magnetic recording layer formed on the glass substrate.

대표청구항 ▼

The invention claimed is: 1. A magnetic information recording medium, comprising a magnetic recording layer formed on a glass substrate made of a non-crystallized glass containing SiO2, B2O3 and Al2O3 as essential components, comprising, by mol %, 40 to 75% of SiO2, 1 to 25% of B2O3, 1 to 20% Al2O3

The invention claimed is: 1. A magnetic information recording medium, comprising a magnetic recording layer formed on a glass substrate made of a non-crystallized glass containing SiO2, B2O3 and Al2O3 as essential components, comprising, by mol %, 40 to 75% of SiO2, 1 to 25% of B2O3, 1 to 20% Al2O3 and 5 to 15% of Li2O, 2 to 45% of a total of B2O3 and Al2O3 and 0 to 40% of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K, wherein the total content of SiO 2, B2O3, Al2O3 and R'2O is at least 90 mol %, the glass having a specific modulus of 30횞106 N쨌m/kg or higher and the glass substrate having no chemical strengthened layer. 2. The magnetic information recording medium of claim 1, wherein the glass substrate has a fragility index value, measured in water, of 12 μm1/2 or less. 3. The magnetic information recording medium of claim 1, wherein the glass substrate has a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μm-1/2 or less. 4. The magnetic information recording medium of claim 1, wherein the glass substrate has a fragility index value, measured in water, of 12 μm-1/2 or less and a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μ m-1/2 or less. 5. The magnetic information recording medium of claim 1, wherein the glass substrate has a B2O3 content of 1 to 25 mol %. 6. The magnetic information recording medium of claim 1, wherein the glass substrate has a B2O3 content of 2 to 20 mol %. 7. A non-crystallized glass substrate for an information recording medium, comprising, by mol %, greater than 65%, as a total, of SiO2 and at least one of B2O3 and Al2 O3, the content of B2O3 being 1 to 25%, 1 to 20% of Al2O3 and 5 to 15% of Li2O, 0 to 20% of RO in which R is at least one member selected from the group consisting of Mg, Ca, Zn, Sr and Ba, 28% or less of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K, 0 to 10% of TiO2 and 0 to 10% of ZrO2, the total content of said components being at least 95 mol %, the glass substrate having a specific modulus of 30횞106 N쨌m/kg or higher and having a fragility index value, measured in water, of 12 μm-1/2 or less. 8. A non-crystallized glass substrate for an information recording medium, comprising, by mol %, greater than 65%, as a total, of SiO2 and at least one of B2O3 and Al2 O3, the content of B2O3 being 1 to 25%, 1 to 20% of Al2O3 and 5 to 15% of Li2O, 0 to 20% of RO in which R is at least one member selected from the group consisting of Mg, Ca, Zn, Sr and Ba, 28% or less of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K, 0 to 10% of TiO2 and 0 to 10% of ZrO2, the total content of said components being at least 95 mol %, the glass substrate having a specific modulus of 30횞106 N쨌m/kg or higher and having a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μm-1/2 or less. 9. A non-crystallized glass substrate for an information recording medium, comprising, by mol %, greater than 65%, as a total, of SiO2 and at least one of B2O3 and Al2 O3, the content of B2O3 being 1 to 25%, 1 to 20% of Al2O3 and 5 to 15% of Li2O, 0 to 20% of RO in which R is at least one member selected from the group consisting of Mg, Ca, Zn, Sr and Ba, 28% or less of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K, 0 to 10% of TiO2 and 0 to 10% of ZrO2, the total content of said components being at least 95 mol %, and having a fragility index value, measured in water, of 12 or less the glass substrate having a specific modulus of 30횞106 N쨌m/kg or higher and having a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μM-1/2 or less. 10. A non-crystallized glass substrate for an information recording medium, comprising, by mol %, 40 to 75% of SiO2, 2 to 45% of B2O3 and/or Al2O3, the content of B2O3 being 1 to 25%, 1 to 20% of Al2O3 and 5 to 15% of Li2O, and 40% or less of R'2O in which R' is at least one member selected from the group consisting of Li, Na and K, wherein the total content of SiO2, B2O 3, Al2O3 and R'2O is at least 90 mol % and wherein the glass substrate having a specific modulus of 30횞106 N쨌m/kg or higher and having a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μm-1/2 or less. 11. The glass substrate for an information recording medium as recited in claim 10, having a fragility index value, measured in water, of 12 μm-1/2 or less. 12. The glass substrate for an information recording medium as recited in claim 10, having a fragility index value, measured in an atmosphere having a dew point of-5째 C. or lower, of 7 μm-1/2 or less. 13. The glass substrate for an information recording medium as recited in any one of claims 7 to 9, wherein the content of B2 O3 is 2 to 20%. 14. The glass substrate for an information recording medium as recited in any one of claims 7 to 10, having a Young's modulus of at least 70 GPa. 15. The glass substrate for an information recording medium as recited in any one of claims 7 to 10, having a modulus of rigidity of at least 20 GPa. 16. The glass substrate for an information recording medium as recited in any one of claims 7 to 10, which is made of a glass having a region wherein the glass has a viscosity of at least 1 Pa쨌s, in a range of temperatures equivalent to, and higher than, a liquidus temperature of the glass. 17. The glass substrate for an information recording medium as recited in any one of claims 7 to 10, which is made of a glass having a thermal expansion coefficient of 60횞10-7/째 C. or greater at a temperature of from 100째 C. to 300째 C. 18. The glass substrate for an information recording medium as recited in any one of claims 7 to 10, which is devoid of a chemically strengthened layer. 19. A magnetic information recording medium comprising a glass substrate as recited in any one of claims 7 to 10, and a magnetic recording layer formed on the glass substrate.