초록 ▼

There is provided a glass substrate which has the properties required in the use as a substrate for an information recording medium of the next generation such as a perpendicular magnetic recording system, and can be applied as a substrate for an information recording medium of the next generation p

There is provided a glass substrate which has the properties required in the use as a substrate for an information recording medium of the next generation such as a perpendicular magnetic recording system, and can be applied as a substrate for an information recording medium of the next generation particularly on the premise of using the glass substrate in a dynamic environment. More particularly, there is provided a glass substrate for an information recording medium which has sufficiently high surface hardness, has a good balance between specific gravity and mechanical strength, and has high strength to withstand high speed rotation or drop impact, and which can be produced with a high productivity adequate for a direct press method, without the occurrence of bubbles in the glass blank or reboil upon pressing even if arsenic components or antimony components are not substantially used. A glass substrate for an information recording medium, includes, as expressed in terms of percent by mass on the oxide basis: 52 to 67% of SiO2, 3 to 15% of Al2O3, and 0.2 to 8% of P2O5, the glass substrate having a Young's modulus of 85 GPa or greater, a specific gravity of 2.60 or less, and a ratio of Young's modulus to specific gravity (Young's modulus/specific gravity) of 33.0 or greater.

대표청구항 ▼

1. A glass substrate for an information recording medium, comprising, as expressed in terms of percent by mass on an oxide basis: 52 to 67% of SiO2,3 to 14% of Al2O3,0.2 to 8% of P2O5,1.5 to 20% of MgO,0 to 10% of CaO,0 to 10% of ZnO,0 to 13% of ZrO2,0 to 16% of TiO2,0 to 1% of CeO2,0 to 1% of SnO2,

1. A glass substrate for an information recording medium, comprising, as expressed in terms of percent by mass on an oxide basis: 52 to 67% of SiO2,3 to 14% of Al2O3,0.2 to 8% of P2O5,1.5 to 20% of MgO,0 to 10% of CaO,0 to 10% of ZnO,0 to 13% of ZrO2,0 to 16% of TiO2,0 to 1% of CeO2,0 to 1% of SnO2,0 to 6% of B2O3,4 to 10% of Na2O, and0 to 7% of K2O,wherein a total amount of MgO, CaO, ZnO, ZrO2 and TiO2 in the glass substrate is 5 to 20% by mass on the oxide basis, and the total amount of CeO2 and/or SnO2 is 0.05 to 1% by mass on the oxide basis, and the total amount B2O3, Na2O, and/or K2O is 4 to 11%) by mass on the oxide basis,the glass substrate having a Young's modulus of 85 GPa or greater,a specific gravity of 2.60 or less, anda ratio of Young's modulus to specific gravity (Young's modulus/specific gravity) of 33.0 GPa or greater. 2. The glass substrate for an information recording medium according to claim 1, further comprising, as expressed in terms of percent by mass on the oxide basis: 2.9 to 8% Li2O. 3. The glass substrate for an information recording medium according to claim 1, wherein the glass substrate does not contain As2O3 component and Sb2O3 component on the oxide basis, and Cl−, NO−, SO2 − and F− components. 4. The glass substrate for an information recording medium according to claim 1, wherein the glass substrate does not contain BaO component or SrO component on the oxide basis. 5. The glass substrate for an information recording medium according to claim 1, wherein, when a content ratio of Li2O component on the oxide basis in a region inside the glass substrate for the information recording medium which extends from an end surface to a depth of 5 μm toward the center is designated as an α%, and the content ratio of the Li2O component n the oxide basis in the region in the glass substrate for the information recording medium which extends from beyond a depth of 5 μm from an end surface toward the center, within the region inside the glass substrate which extends from a depth of 5 μm from one main surface to a depth of 5 μm from an other main surface along the thickness direction, is designated as a β%, the ratio of α/β is 1 or less. 6. The glass substrate for an information recording medium according to claim 1, wherein the surface roughness Ra (arithmetic mean roughness) is 2 A or less. 7. An information recording medium making use of the glass substrate for an information recording medium according to claim 1.