Method for manufacturing a crystalized glass magnetic disk substrate

Claim 1

A method for manufacturing a magnetic disk substrate comprising the steps of: melting a base glass consisting essentially in weight percent of: ______________________________________ Li.sub.2 O 8-13% K.sub.2 O 0-7% MgO + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5.5% PbO 0-5.5% P.sub.2 O.sub.5 1-4% Al.sub.2 O.sub.3 0-7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% ______________________________________ forming the molten glass into a desired shape; heating the formed glass to produce a crystal nucleus under a temperature within a range from 450° C. to 540° C.; heating the glass at a temperature within a range from 700° C. to 840° C. to further crystallize the glass; and polishing the surface of the glass to a surface roughness within a range of 15 Å to 50 Å to produce a magnetic disk substrate having crystal phases which consist of lithium disilicate Li 2 O.2Si 2 O) and alpha quartz (SiO 2 ), said crystal phase of alpha-quartz being formed of grown crystal grains each having a globular grain structure made of aggregated particles and said crystal grains of alpha-quartz being randomly scattered in the finer particles of lithium disilicate, and said magnetic disk substrate having a polished surface having a surface roughness within a range of 15 Å to 50 Å.

Claim 2

A method for manufacturing a magnetic disk substrate comprising the steps of: melting a base glass consisting essentially in weight percent of: ______________________________________ Li.sub.2 O 8-13% K.sub.2 O 0-7% MgO + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5.5% PbO 0-5.5% P.sub.2 O.sub.5 1-4% Al.sub.2 O.sub.3 0-7% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% ______________________________________ forming the molten glass into a desired shape; heating the formed glass to produce a crystal nucleus under a temperature within a range from 450° C. to 540° C.; heating the glass at a temperature within a range from 700° C. to 840° C. to further crystallize the glass; and polishing the surface of the glass to a surface roughness within a range of 15 Å to 50 Å to produce a magnetic disk substrate having crystal phases which consist of lithium disilicate Li 2 O.2Si 2 O) and alpha quartz (SiO 2 ), said crystal phase of alpha-quartz being formed of grown crystal grains each having a globular grain structure made of aggregated particles and said crystal grains of alpha-quartz being randomly scattered in the finer particles of lithium disilicate, and said magnetic disk substrate having a polished surface having a surface roughness within a range of 15 Å to 50 Å.

Claim 3

A method for manufacturing a magnetic disk substrate comprising the steps of: melting a base glass consisting essentially in weight percent of: ______________________________________ SiO.sub.2 70-82% Li.sub.2 O 8-12% K.sub.2 O 1-6% MgO + ZnO + PbO 1.5-5.0% in which MgO 1-5% ZnO 0.2-5% P.sub.2 O.sub.5 1-3% Al.sub.2 O.sub.3 1-6% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% ______________________________________ forming the molten glass into a desired shape; heating the formed glass to produce a crystal nucleus under a temperature within a range from 450° C. to 540° C.; heating the glass at a temperature within a range from 700° C. to 840° C. to further crystallize the glass; and polishing the surface of the glass to to produce a magnetic disk substrate having crystal phases which consist of lithium disilicate Li 2 O.2Si 2 O) and alpha quartz (SiO 2 ), said crystal phase of alpha-quartz being formed of grown crystal grains each having a globular grain structure made of aggregated particles and said crystal grains of alpha-quartz being randomly scattered in the finer particles of lithium disilicate, and said magnetic disk substrate having a polished surface having a surface roughness within a range of 15 Å to 50 Å.

Claim 4

A method for manufacturing a magnetic disk substrate comprising the steps of: melting a base glass consisting essentially in weight percent of: ______________________________________ SiO.sub.2 70-82% Li.sub.2 O 8-12% K.sub.2 O 1-6% MgO + ZnO + PbO 1.5-5.0% in which MgO 1-5% ZnO 0.2-5% P.sub.2 O.sub.5 1-3% Al.sub.2 O.sub.3 1-6% As.sub.2 O.sub.3 + Sb.sub.2 O.sub.3 0-2% ______________________________________ forming the molten glass into a desired shape; heating the formed glass to produce a crystal nucleus under a temperature within a range from 450° C. to 540° C.; heating the glass at a temperature within a range from 700° C. to 840° C. to further crystallize the glass; and polishing the surface of the glass to to produce a magnetic disk substrate having crystal phases which consist of lithium disilicate Li 2 O.2Si 2 O) and alpha quartz (SiO 2 ), said crystal phase of alpha-quartz being formed of grown crystal grains each having a globular grain structure made of aggregated particles and said crystal grains of alpha-quartz being randomly scattered in the finer particles of lithium disilicate, and said magnetic disk substrate having a polished surface having a surface roughness within a range of 15 Å to 50 Å.