Patent US1955791A successfully refreshed from Google Patents.

Patent US5391522A successfully refreshed from Google Patents.

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

📄 Original PDF 🌐 Google Patents 🔄 Sync Now

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 01:19

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

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

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

Assigned Categories & Tags

No categories assigned to this patent yet.

Assign Category Tag

Select Category

Notes (Optional)