US5391522A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Glass-ceramic for magnetic disks and method for manufacturing the same
Assignee: Ohara Inc
•
Filing: 1994-05-25
•
Granted: 1995-02-21
•
Expires: 2014-05-25
Abstract
Abstract A glass-ceramic for a magnetic disk substrate in which the grain size can be controlled and the surface roughness after polishing is within the range from 15 Å to 50 Å is provided by heat treating a base glass including in weight percent: ______________________________________ SiO 2 65-83% Li 2 O 8-13% K 2 O 0-7% Mgo + ZnO + PbO 0.5-5.5% in which MgO 0.5-5.5% ZnO 0-5% PbO 0-5% P 2 O 5 1-4% Al 2 O 3 0-7% As 2 O 3 + Sb 2 O 3 0-2% ______________________________________ The glass-ceramic contains lithium disilicate (Li 2 O. 2SiO 2 ) and alpha-quartz (SiO 2 ) as the main crystal phases.
Inventors
- 👤 Naoyuki Goto
- 👤 Katsuhiko Yamaguchi
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-09 00:30
CPC Classifications
C; C03; C03C; C03C10/00; C03C10/0009; C03C23/00; C03C23/007; G; G11; G11B; G11B5/00; G11B5/62; G11B5/73; G11B5/739; G11B5/73911; G11B5/73921; G11B5/84; G11B5/8404
Claims Analysis
Total Claims: 16
Claim 1
Independent Claim
78 words
A glass-ceramic for magnetic disks formed by subjecting to heat treatment a base glass which consists essentially of in weight percent: ______________________________________
SiO.sub.2 65-83%
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%
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%
______________________________________ said glass-ceramic containing lithium disilicate (Li 2 O. 2SiO 2 ) and alpha-quartz (SiO 2 ) as the main crystal phases.
Claim 2
Dependent Claim
78 words
A glass-ceramic for magnetic disks formed by subjecting to heat treatment a base glass which consists essentially of in weight percent: ______________________________________
SiO.sub.2 65-83%
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%
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%
______________________________________ said glass-ceramic containing lithium disilicate (Li 2 O. 2SiO 2 ) and alpha-quartz (SiO 2 ) as the main crystal phases.
Claim 3
Dependent Claim
21 words
A glass-ceramic as defined in claim 1 wherein a grown crystal grain (secondary grain) of alpha-quartz has a globular grain structure.
Claim 4
Dependent Claim
44 words
A glass-ceramic as defined in claim 2 wherein the size of the crystal grain is controlled to the range from 0.3 μm to 3 μm by heat treatment and surface roughness (Ra) of the ground surface is in the range from 15Å to 50Å.
Claim 5
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the Li 2 O is 9%.
Claim 6
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the Li 2 O is 10%.
Claim 7
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the Li 2 O is 11%.
Claim 8
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the Li 2 O is 8%.
Claim 9
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the Li 2 O is 10.5%.
Claim 10
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 1 wherein the K 2 O is 0%.
Claim 11
Dependent Claim
51 words
A glass ceramic as defined in claim 1 wherein the glass ceramic is of the formula: ______________________________________
SiO.sub.2 73.0%
Li.sub.2 O 8%
K.sub.2 O 4%
MgO + ZnO + PbO 4.5%
in which MgO 4.0%
ZnO 0.5%
PbO 0%
P.sub.2 O.sub.5 4%
Al.sub.2 O.sub.3 5%
As.sub.2 O.sub.3 0.5%
SrO 1.0%.
______________________________________
Claim 12
Dependent Claim
49 words
A glass ceramic as defined in claim 1 wherein the glass ceramic is of the formula: ______________________________________
SiO.sub.2 76.0%
Li.sub.2 O 10.5%
K.sub.2 O 4%
MgO + ZnO + PbO 3%
in which MgO 2.5%
ZnO 0.5%
PbO 0%
P.sub.2 O.sub.5 2%
Al.sub.2 O.sub.3 4%
As.sub.2 O.sub.3 0.5%.
______________________________________
Claim 13
Dependent Claim
49 words
A glass ceramic as defined in claim 1 wherein the glass ceramic is of the formula: ______________________________________
SiO.sub.2 76.5%
Li.sub.2 O 10.5%
K.sub.2 O 4%
MgO + ZnO + PbO 3%
in which MgO 1.0%
ZnO 2.0%
PbO 0%
P.sub.2 O.sub.5 2%
Al.sub.2 O.sub.3 3.5%
As.sub.2 O.sub.3 0.5%.
______________________________________
Claim 14
Dependent Claim
102 words
A glass-ceramic for magnetic disks formed by subjecting to heat treatment a base glass which consists essentially of in weight percent of: ______________________________________
SiO.sub.2 65-83%
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%
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%
______________________________________ said glass-ceramic containing lithium disilicate (Li 2 O. 2SIO 2 ) and alpha-quartz (SiO 2 ) as the main crystal phases said glass ceramic having been subjected to a lapping and polishing process which produces a surface roughness from 15 Å to 50 Å.
Claim 15
Dependent Claim
102 words
A glass-ceramic for magnetic disks formed by subjecting to heat treatment a base glass which consists essentially of in weight percent of: ______________________________________
SiO.sub.2 65-83%
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%
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%
______________________________________ said glass-ceramic containing lithium disilicate (Li 2 O. 2SIO 2 ) and alpha-quartz (SiO 2 ) as the main crystal phases said glass ceramic having been subjected to a lapping and polishing process which produces a surface roughness from 15 Å to 50 Å.
Claim 16
Dependent Claim
17 words
A glass-ceramic for magnetic disks as defined in claim 13 wherein the PbO is 1 to 4%.
References Cited (Backward Citations)
US2971853A
Cited
US3231456A
Cited
US3220815A
Cited
US3238085A
Cited
US3804608A
Cited
US3977857A
Cited
US4414282A
Cited
US4515634A
Cited
US4480044A
Cited
US4672152A
Cited
US5219799A
Cited
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1998-02-20 | 1998-08-22 | 1999-02-21 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 2002-02-20 | 2002-08-22 | 2003-02-21 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2006-02-20 | 2006-08-22 | 2007-02-21 | $7700.00 | Window Closed / Lapsed |