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AssigneeHoya Corporation
InventorsXuelu Zou, Kouji Azegami
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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.
A crystallized glass substrate for information recording medium comprising SiO2 of 35 to 65 mol %, Al2O3 of 5 to 25 mol %, MgO of 10 to 40 mol %, TiO2 of 5 to 15 mol %, and Y2O3 of 0.8 to 10 mol %.
A crystallized glass substrate for information recording medium comprising SiO2 of 35 to 65 mol %, Al2O3 of 5 to 25 mol %, MgO of 10 to 40 mol %, and TiO2 of 5 to 15 mol %, wherein a mole ratio (Al2O3/MgO) is less than 0.5.
A crystallized glass substrate for information recording medium comprising SiO2 of 35 to 65 mol %, Al2O3 of 5 to 25 mol %, MgO of 10 to 40 mol %, TiO2 of 5 to 15 mol %, and Li2O of 0.2 to 10 mol %, wherein the substrate has a primary crystal phase made of a quasi-stable quartz solid solution and an enstatite, and wherein the mean grain size of the crystal grains is 1 micron or less.
A crystallized glass for information recording disc comprising SiO2 of 42 to 65 mol %, Al2O3 of 0 to 15 mol %, MgO of 5 to 30 mol %, Y2O3 of 0.5 to 8 mol %, and Li2O greater than 10 mol % but equal to or less than 25 mol %, wherein the glass has a primary crystal phase made of a quasi-stable quartz solid solution and an enstatite.
A crystallized glass for information recording disc comprising SiO2 of 35 to 55 mol %, Al2O3 equal to or more than 0 mol % and less than 5 mol %, MgO of 25 to 45 mol %, Y2O3 of 0.5 to 8 mol %, ZrO2 of 0 to 10 mol %, and TiO2 of 0 to 12 mol %, providing that ZrO2+TiO2 is of 4.5 mol % to 18 mol %, wherein the glass has a primary crystal phase made of a quasi-stable quartz solid solution and/or an enstatite.
Dependencies are inferred from the claim text.