Glass for magnetic recording medium substrate or for glass spacer to be used in magnetic recording/reproducing device, magnetic recording medium substrate, magnetic recording medium, and magnetic recording/reproducing apparatus

Patent metadata

Field	Value
Publication number	US-12473225-B2
Application number	US-202418655216-A
Country	US
Kind code	B2
Filing date	May 3, 2024
Priority date	Dec 13, 2019
Publication date	Nov 18, 2025
Grant date	Nov 18, 2025

Abstract

Provided is a glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus, in which a mole ratio of the total content of Al 2 O 3 and MgO relative to the total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less, the total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less, the total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less, the Na 2 O content is 0 mol %, and an average linear expansion coefficient of the glass at 100° C. to 300° C. is 68×10 −7 /° C. or less.

First claim

What is claimed is:

1 . A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus,
wherein the glass comprises the following mole ratios: a mole ratio of a total content of Al 2 O 3 and MgO relative to a total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less, a total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less, a total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less, an Na 2 O content is 0 mol %, and an average linear expansion coefficient of the glass at 100° C. to 300° C. is 57×10 −7 /° C. or less.

2 . The glass according to claim 1 ,
wherein a total content of TiO 2 and ZrO 2 (TiO 2 +ZrO 2 ) is 0.5 mol % or more.

3 . A magnetic recording medium substrate comprised of the glass according to claim 2 .

4 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 3 ; and a magnetic recording layer.

5 . A magnetic recording/reproducing apparatus comprising:
the magnetic recording medium according to claim 4 ; and a magnetic head.

6 . A magnetic recording medium substrate comprised of the glass according to claim 1 .

7 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 6 ; and a magnetic recording layer.

8 . A magnetic recording/reproducing apparatus comprising:
the magnetic recording medium according to claim 7 ; and a magnetic head.

9 . A glass for a magnetic recording medium substrate or for a glass spacer for a magnetic recording/reproducing apparatus,
wherein the glass comprises the following mole ratios: a mole ratio of a total content of Al 2 O 3 and MgO relative to a total content of SiO 2 and CaO [(Al 2 O 3 +MgO)/(SiO 2 +CaO)] is in a range of 0.417 or more and 0.6 or less, a total content of SiO 2 and Al 2 O 3 (SiO 2 +Al 2 O 3 ) is in a range of 64 mol % or more and 85 mol % or less, a total content of SiO 2 , Al 2 O 3 , MgO, and CaO (SiO 2 +Al 2 O 3 +MgO+CaO) is in a range of 87 mol % or more and 98 mol % or less, a ZrO 2 content is 0 mol %, and an average linear expansion coefficient of the glass at 100° C. to 300° C. is 57×10 −7 /° C. or less.

10 . The glass according to claim 9 ,
wherein an Na 2 O content is 0 mol %.

11 . A magnetic recording medium substrate comprised of the glass according to claim 10 .

12 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 11 ; and a magnetic recording layer.

13 . A magnetic recording/reproducing apparatus comprising:
the magnetic recording medium according to claim 12 ; and a magnetic head.

14 . A magnetic recording medium substrate comprised of the glass according to claim 9 .

15 . A magnetic recording medium comprising:
the magnetic recording medium substrate according to claim 14 ; and a magnetic recording layer.

16 . A magnetic recording/reproducing apparatus comprising:
the magnetic recording medium according to claim 15 ; and a magnetic head.

Assignees

• Hoya Corp

Inventors

• Sato Koichi
• Hashimoto Kazuaki

Classifications

• G11B5/72

  Protective coatings, e.g. anti-static {or antifriction} · CPC title

• G11B5/235

  Selection of material for gap filler {(G11B5/232 takes precedence)} · CPC title

• C03C3/087

  containing calcium oxide, e.g. common sheet or container glass · CPC title

• B24B41/053

  for grinding or polishing glass {(B24B41/0475 takes precedence)} · CPC title

• C03C3/095 Primary

  containing rare earths · CPC title