Magnetic memory storage devices

Claim 2

In a magnetic memory storage device consisting essentially of a head pad and a rigid information disk, said disk consisting essentially of a rigid substrate having a coating of magnetic media on the surface thereof facing said magnetic head, the improvement which comprises using a disk having a modulus of rupture ranging from about 15,000-40,000 psi and having a textured surface roughness of about R a =1.5-5 nm, in which said substrate consists essentially of a glass-ceramic wherein the predominant crystal phase present has a microstructure selected from the group consisting of a sheet silicate and a chain silicate.

Claim 3

A magnetic memory storage device according to claim 1 wherein the crystal phase which has a sheet silicate microstructure present in said glass-ceramic substrate is selected from the group consisting of predominantly fluorophlogopite solid solution and predominantly tetrasilicic fluormica.

Claim 4

A magnetic memory storage device according to claim 2 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of fluorophlogopite solid solution has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 25-60 Cs.sub.2 O 0-20 B.sub.2 O.sub.3 5-15 Na.sub.2 O + K.sub.2 O + Rb.sub.2 O + Cs.sub.2 O 2-20 Al.sub.2 O.sub.3 5-25 MgO 4-25 B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 15-35 Li.sub.2 O 0-7 Na.sub.2 O 0-15 MgO + Li.sub.2 O 6-25 K.sub.2 O 0-15 F 4-20 Rb.sub.2 O 0-15 ______________________________________

Claim 5

A magnetic memory storage device according to claim 3 wherein said glass-ceramic substrate consists essentially of about ______________________________________ SiO.sub.2 47.0 K.sub.2 O 9.5 B.sub.2 O.sub.3 8.5 F 6.3 Al.sub.2 O.sub.3 16.7 O = F 2.5 MgO 14.5 ______________________________________

Claim 6

A magnetic memory storage device according to claim 2 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of tetrasilicic fluormica has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 45-70% SiO 2 , 8-20% MgO, 8-15% MgF 2 , 5-25% R 2 O, wherein R 2 O consists of 0-20% K 2 O, 0-20% Rb 2 O, and 0-20% Cs 2 O, 0-20% RO, wherein RO consists of 0-20% SrO, 0-20% BaO, and 0-20% CdO, and 5-35% R 2 O+RO.

Claim 7

A magnetic memory storage device according to claim 1 wherein the crystal phase having a chain silicate microstructure present in said glass-ceramic substrate is selected from the group consisting of predominantly canasite, predominantly potassium fluorrichterite, and predominantly potassium fluorrichterite, but also containing a substantial amount of cristobalite.

Claim 8

A magnetic memory storage device according to claim 6 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of canasite has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 50-70 MgO 0-2 CaO 15-25 ZnO 0-2 Na.sub.2 O 6-10 SnO.sub.2 0-2 K.sub.2 O 6-12 Sb.sub.2 O.sub.3 0-1 Al.sub.2 O.sub.3 1-4 F 4-9 ______________________________________

Claim 9

A magnetic memory storage device according to claim 7 wherein said glass-ceramic substrate has a composition consisting essentially of ______________________________________ SiO.sub.2 55-60 K.sub.2 O 8-9.5 CaO 20-23 Al.sub.2 O.sub.3 1.5-2.5 Na.sub.2 O 7.5-9 F 5-7.5 ______________________________________

Claim 10

A magnetic memory storage device according to claim 6 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of potassium fluorrichterite has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 58-70 K.sub.2 O 3.8-7 Al.sub.2 O.sub.3 0.5-3 Li.sub.2 O 0.5-2 MgO 13-17.5 BaO 0-2.5 CaO 3-7 P.sub.2 O.sub.5 0-2.5 Na.sub.2 O 1.5-4 F 3-5.5 ______________________________________

Claim 11

A magnetic memory storage device according to claim 9 wherein said glass-ceramic substrate has a composition consisting essentially of ______________________________________ SiO.sub.2 62-67 K.sub.2 O 3.8-6 Al.sub.2 O.sub.3 1-3 Li.sub.2 O 0.5-1.5 MgO 13.5-16.5 BaO 0-2 CaO 4-7 P.sub.2 O.sub.5 0-2 Na.sub.2 O 1.5-3.5 F 3.3-5 ______________________________________

Claim 12

A magnetic memory storage device according to claim 6 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of potassium fluorrichterite, but also contains a substantial amount of cristobalite, has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 65-69 K.sub.2 O 4.2-6 Al.sub.2 O.sub.3 0.75-3 Li.sub.2 O 0.5-2 MgO 13.5-16.5 BaO 0- 2 CaO 3-4.8 P.sub.2 O.sub.5 0- 2 Na.sub.2 O 1.5-3.3 F 3.3-5 ______________________________________

Claim 13

A rigid information disk for use in a magnetic memory storage device consisting essentially of a substrate with a coating of magnetic media on a surface thereof, in which said substrate consists essentially of a glass-ceramic wherein the predominant crystal phase present has a microstructure selected from the group consisting of a sheet silicate and a chain silicate.

Claim 14

A rigid information disk for use in a magnetic memory storage device consisting essentially of a substrate with a coating of magnetic media on a surface thereof, in which said substrate consists essentially of a glass-ceramic wherein the predominant crystal phase present has a microstructure selected from the group consisting of a sheet silicate and a chain silicate.

Claim 15

A rigid information disk according to claim 12 wherein the crystal phase having a sheet silicate microstructure present in said glass-ceramic substrate is selected from the group consisting of predominantly fluorophlogopite solid solution and predominantly tetrasilicic fluormica.

Claim 16

A rigid information disk according to claim 13 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of fluorophlogopite solid solution has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 25-60 Cs.sub.2 O 0-20 B.sub.2 O.sub.3 5-15 Na.sub.2 O + K.sub.2 O + Rb.sub.2 O + Cs.sub.2 O 2-20 Al.sub.2 O.sub.3 5-25 MgO 4-25 B.sub.2 O.sub.3 + Al.sub.2 O.sub.3 15-35 Li.sub.2 O 0-7 Na.sub.2 O 0-15 MgO + Li.sub.2 O 6-25 K.sub.2 O 0-15 F 4-20 Rb.sub.2 O 0-15 ______________________________________

Claim 17

A rigid information disk according to claim 14 wherein said glass-ceramic substrate consists essentially of about ______________________________________ SiO.sub.2 47.0 K.sub.2 O 9.5 B.sub.2 O.sub.3 8.5 F 6.3 Al.sub.2 O.sub.3 16.7 O = F 2.5 MgO 14.5 ______________________________________

Claim 18

A rigid information disk according to claim 13 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of tetrasilicic fluormica has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of 45-70% SiO 2 , 8-20% MgO, 8-15% MgF 2 , 5-25% R 2 O, wherein R 2 O consists of 0-20% K 2 O, 0-20% Rb 2 O, and 0-20% Cs 2 O, 0-20% RO, wherein RO consists of 0-20% SrO, 0-20% BaO, and 0-20% CdO, and 5-35% R 2 O+RO.

Claim 19

A rigid information disk according to claim 12 wherein the crystal phase having a chain silicate microstructure present in said glass-ceramic substrate is selected from the group consisting of predominantly canasite, predominantly potassium fluorrichterite, and predominantly potassium fluorrichterite, but also containing a substantial amount of cristobalite.

Claim 20

A rigid information disk according to claim 17 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of canasite has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 50-70 MgO 0-2 CaO 15-25 ZnO 0-2 Na.sub.2 O 6-10 SnO.sub.2 0-2 K.sub.2 O 6-12 Sb.sub.2 O.sub.3 0-1 Al.sub.2 O.sub.3 1-4 F 4-9 ______________________________________

Claim 21

A rigid information disk according to claim 18 wherein said glass-ceramic substrate has a composition consisting essentially of ______________________________________ SiO.sub.2 55-60 K.sub.2 O 8-9.5 CaO 20-23 Al.sub.2 O.sub.3 1.5-2.5 Na.sub.2 O 7.5-9 F 5-7.5 ______________________________________

Claim 22

A rigid information disk according to claim 17 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of potassium fluorrichterite has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 58-70 K.sub.2 O 3.8-7 Al.sub.2 O.sub.3 0.5-3 Li.sub.2 O 0.5-2 MgO 13-17.5 BaO 0-2.5 CaO 3-7 P.sub.2 O.sub.5 0-2.5 Na.sub.2 O 1.5-4 F 3-5.5 ______________________________________

Claim 23

A rigid information disk according to claim 20 wherein said glass-ceramic substrate in which the crystal phase consists predominantly of potassium fluorrichterite, but also contains a substantial amount of cristobalite, has a composition consisting essentially, expressed in terms of weight percent on the oxide basis, of ______________________________________ SiO.sub.2 65-69 K.sub.2 O 4.2-6 Al.sub.2 O.sub.3 0.75-3 Li.sub.2 O 0.5-2 MgO 13.5-16.5 BaO 0-2 CaO 3-4.8 P.sub.2 O.sub.5 0-2 Na.sub.2 O 1.5-3.3 F 3.3-5 ______________________________________