초록 ▼

Enclosed are crystallized glasses suitable for a substrate for an information recording medium such as a magnetic disc, optical disc, or optomagnetic disc, a substrate for information recording medium using such a crystallized glass substrate, and an information recording medium using such a substra

Enclosed are crystallized glasses suitable for a substrate for an information recording medium such as a magnetic disc, optical disc, or optomagnetic disc, a substrate for information recording medium using such a crystallized glass substrate, and an information recording medium using such a substrate for information recording medium. The crystallized glasses are capable of providing a glass substrate having a high Young's modulus, as well as excellent mechanical strength, surface flatness, and heat resistance and having an excellent surface smoothness upon polishing. Glass substrate having an excellent surface smoothness using such a crystallized glass are also disclosed.

대표청구항 ▼

1. A crystallized glass substrate for information recording medium comprising SiO2of 35 to 65 mol %, Al2O3of 5 to 20 mol %, MgO of 10 to 40 mol %, and TiO2of 5 to 15 mol %, wherein a mole ratio (Al2O3/MgO) is less than 0.5, the substrate comprising a primary crystal phase consisting essentially of a

1. A crystallized glass substrate for information recording medium comprising SiO2of 35 to 65 mol %, Al2O3of 5 to 20 mol %, MgO of 10 to 40 mol %, and TiO2of 5 to 15 mol %, wherein a mole ratio (Al2O3/MgO) is less than 0.5, the substrate comprising a primary crystal phase consisting essentially of a quartz solid solution and an enstatite, wherein the composition of the quartz solid solution is selected from the group consisting of 2MgO.2Al2O3.5SiO2,MgO.Al2O3.3SiO2,MgO.Al2O3.4SiO2and mixtures thereof. 2. The substrate according to claim 1, which further comprises 0 to 10 mol % of Y2O3. 3. The substrate according to claim 1, wherein surface mean roughness Ra of the substrate is 20 angstroms or less. 4. The substrate according to claim 1, wherein the information recording medium is a magnetic disc. 5. An information recording medium comprising the substrate of claim 1 and a recording layer formed on the substrate. 6. The information recording medium according to claim 5, wherein the recording layer is a magnetic recording layer. 7. The substrate of claim 1, which further comprises 0 to 10 mol % of at least on alkali metal oxide selected from the group consisting of Na2O and K2O. 8. The substrate of claim 1, which contains a secondary crystal phase comprising Mg--Al-titanate. 9. A crystallized glass substrate for information recording medium comprising SiO2of 35 to 65 mol %, Al2O3of 5 to 20 mol %, MgO of 10 to 40 mol %, TiO2of 5 to 15 mol %, ZnO of 0 to 10 mol % and Li2O of 0 to 10 mol %, wherein a mole ratio (Al2O3/MgO) is less than 0.5, the substrate comprising a primary crystal phase consisting essentially of a quartz solid solution and an enstatite, wherein the composition of the quartz solid solution is selected from the group consisting of 2MgO·2Al2O3·5SiO2,MgO·Al2O3·3SiO2,MgO·Al2O3·4SiO2and mixtures thereof.