Compositions: ceramic – Ceramic compositions – Devitrified glass-ceramics
Patent
1997-04-02
1998-03-10
Group, Karl
Compositions: ceramic
Ceramic compositions
Devitrified glass-ceramics
501 9, 501 10, 501 63, 501 66, 501 77, 428694ST, 428694SG, C03C 1004, C03C 1002
Patent
active
057261083
ABSTRACT:
A glass-ceramic magnetic disk substrate which is prepared by forming, then heat treating, and then polishing a crystallizable glass composition comprising, expressed in terms of weight percent on the oxide basis: from 20 to 45% SiO.sub.2 ; from 25 to 45% Al.sub.2 O.sub.3 ; from 10 to 25% B.sub.2 O.sub.3 ; from 2 to 12% MgO; from 0.5 to 8% TiO.sub.2 ; from 0.5 to 5% P.sub.2 O.sub.5 ; from 0 to 2% Li.sub.2 O; from 0 to 2% Na.sub.2 O; from 0 to 3% K.sub.2 O; wherein, the total of the contents of Li.sub.2 O, Na.sub.2 O and K.sub.2 O is from 0 to 5%; and wherein the magnetic disk substrate comprises a main crystalline phase consisting of at least one member selected from the group consisting of mullite and aluminum borate crystals. The glass composition can easily be formed and the disk substrate can easily be polished, has excellent mechanical strength, surface flatness, surface smoothness, chemical durability, and heat resistance, and shows no deterioration of magnetic film characteristics by alkali migration.
REFERENCES:
patent: 4396720 (1983-08-01), Beall et al.
patent: 4519828 (1985-05-01), Beall et al.
patent: 5468694 (1995-11-01), Taguchi et al.
patent: 5476821 (1995-12-01), Beall et al.
patent: 5567217 (1996-10-01), Goto et al.
Kawai Hideki
Kuriyama Ikuo
Nakajima Sadao
Ohara Tohru
Taguchi Tomoyuki
Group Karl
Yamamura Glass Co. Ltd.
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