Minolta Company, Ltd.

Hiroshi Yuki

Hideki Nagata

Kazuhiko Ishimaru

Hideki Kawai

Toshiharu Mori

Akira Sugimoto

A polished glass disk medium substrate suitable for use as a substrate for a hard disk, a hard disk containing the substrate and methods for making the substrate. The substrate containing glass forming raw materials may be formed so as to have a Young's modulus of 110 or higher.

Glass composition for crystallized glass

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 35 to 60 wt % of SiO , from 10 to 30 wt % of Al O , from 10 to 30 wt % of MgO and from 0.1 to 1.8 wt % of P O .

Glass-ceramic composition for recording disk substrate

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 51 to 57.5 wt % of SiO , from 10 to 30 wt % of Al O , from 10 to 30 wt % of MgO, and from 0.1 to 6.8 wt % of TiO .

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 48 to 54.8 wt % of SiO , from 10 to 30 wt % of Al O , from 10 to 30 wt % of MgO, and from 2.4 to 10 wt % of Li O.

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 35 to 50 wt % of SiO , from 10 to 30 wt % of Al O , from 10 to 30 wt % of MgO, and from 2.6 to 8 wt % of Li O.

A glass ceramics composition for recording disk substrate consists essentially, expressed in terms of weight percent on the oxide basis, of from 65 to 80 wt % of SiO , from 3 to 15 wt % of Al O , from 3 to 15 wt % of Li O, from 0.2 to 5 wt % of P O , and from 0.1 to 15 wt % of ZrO , wherein a value of ZrO /P O is within a range from 1.1 to 8.5, expressed in terms of weight percent on the oxide basis.

A glass ceramics composition for recording disk substrate contains, essentially, expressed in terms of weight percent on the oxide basis, from 54.5 to 59.5 wt % of SiO , from 10 to 30 wt % of Al O , from 10 to 30 wt % of MgO, and from 3 to 12 wt % of Li O.

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Shiga-ken, Japan

Hiroshi Yuki