Magnetic recording medium with controlled surface characteristics

• US 10,580,447 B2
• Filed: 05/12/2016
• Issued: 03/03/2020
• Est. Priority Date: 05/18/2015
• Status: Active Grant

• Current Assignee: Sony Corporation (Sony Group Corp.)
• Original Assignee: Sony Corporation (Sony Group Corp.)
• Inventors: Sekiguchi, Noboru, Ozaki, Tomoe, Endo, Tetsuo, Aizawa, Takashi, Tachibana, Junichi, Terui, Hikaru, Sai, Teruo
• Primary Examiner(s): Bernatz, Kevin M
• Application Number:
  US15/573,374
• Publication Number:
  US 20180137887A1
• Time in Patent Office: 1,391 Days
• Field of Search: None
• CPC Class Codes: G11B 5/658 containing oxygen, e.g. molecular oxygen or magnetic oxide
• CPC Class Codes: G11B 5/667 including a soft magnetic layer
• CPC Class Codes: G11B 5/674 having differing macroscopic or microscopic structures, e.g. differing crystalline lattices, varying atomic structures or differing roughnesses
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/736 Non-magnetic layer under a soft magnetic layer, e.g. between a substrate and a soft magnetic underlayer [SUL] or a keeper layer magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7368 Non-polymeric layer under the lowermost magnetic recording layer base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7369 Two or more non-magnetic underlayers, e.g. seed layers or barrier layers
• CPC Class Codes: G11B 5/73925 Composite or coated non-esterified substrates
• CPC Class Codes: G11B 5/73935 characterised by roughness or surface features, e.g. by added particles

Abstract

A magnetic recording medium has a recording surface having an average surface roughness SRa of 3.0 nm or less, the number of projections having a height of 7.5 nm or more included in a unit region (where the unit region is a square region with each side having a length of 30 μm) of the recording surface is 256 or more, and the number of projections having a height of 15 nm or more included in the unit region of the recording surface is 0 or more and 104 or less.

Claims

1. A magnetic recording medium comprising:

a base substance having flexibility;

a crystal control layer provided on the base substance; and

a magnetic layer provided on the crystal control layer, wherein

the magnetic recording medium has a recording surface having an average surface roughness SRa of 3.0 nm or less,

the number of projections having a height of 7.5 nm or more included in a unit region of the recording surface is 256 or more and 3000 or less, the unit region is a square region with each side having a length of 30 μ

m, and

the number of projections having a height of 15 nm or more included in the unit region of the recording surface is 0 or more and 104 or less.

2. The magnetic recording medium according to claim 1, wherein

the base substance has an uneven surface on the recording surface side, and

the uneven surface of the base substance has an uneven shape substantially similar to the recording surface.

3. The magnetic recording medium according to claim 2, wherein the recording surface substantially conforms to the uneven surface of the base substance.

4. The magnetic recording medium according to claim 1, comprising:

an uneven layer provided between the base substance and the crystal control layer and having an uneven surface on the crystal control layer side, wherein

the uneven layer contains particulates.

5. The magnetic recording medium according to claim 4, wherein the uneven surface of the uneven layer is composed of the particulates.

6. The magnetic recording medium according to claim 4, wherein the uneven surface of the uneven layer has an uneven shape substantially similar to the recording surface.

7. The magnetic recording medium according to claim 6, wherein the recording surface substantially conforms to the uneven surface of the uneven layer.

8. The magnetic recording medium according to claim 1, wherein the crystal control layer and the magnetic layer are sputtering films.

9. The magnetic recording medium according to claim 1, wherein the crystal control layer includes

a foundation layer, and

a seed layer provided between the foundation layer and the base substance.

10. The magnetic recording medium according to claim 9, wherein the seed layer has an amorphous state.

11. The magnetic recording medium according to claim 9, wherein the seed layer contains Ti and Cr.

12. The magnetic recording medium according to claim 9, wherein the foundation layer contains Ru.

13. The magnetic recording medium according to claim 9, wherein the seed layer contains Cr, Ni, and Fe.

14. The magnetic recording medium according to claim 9, wherein

the crystal control layer further includes an intermediate layer provided between the seed layer and the foundation layer,

the seed layer contains Cr, Ni, and Fe, and

the intermediate layer contains Co and O.

15. The magnetic recording medium according to claim 1, further comprising:

a soft magnetic layer provided between the base substance and the crystal control layer.

16. The magnetic recording medium according to claim 15, wherein

the soft magnetic layer includes a first soft magnetic layer, an intermediate layer, and a second soft magnetic layer, and

the intermediate layer is provided between the first soft magnetic layer and the second soft magnetic layer.

17. The magnetic recording medium according to claim 15, further comprising:

a seed layer provided between the base substance and the soft magnetic layer.

18. The magnetic recording medium according to claim 1, wherein the magnetic layer has a granular structure obtained by separating particles containing Co, Pt, and Cr by an oxide.

19. The magnetic recording medium according to claim 18, wherein the magnetic layer has an average composition shown in the following expression:

(Co_xPt_yCr_100-x-y)_100-z—

(SiO₂)_z

(where x, y, and z are values in the range of 69≤

x≤

72, 12≤

y≤

16, and 9≤

z≤

12, respectively).

20. The magnetic recording medium according to claim 1, wherein the number of projections having a height of 7.5 nm or more included in the unit region of the recording surface is from 2500 to 3000.

21. The magnetic recording medium according to claim 1, wherein the number of projections having a height of 15 nm or more included in the unit region of the recording surface is from 0 to 10.