Magnetic recording medium and cartridge

Patent metadata

Field	Value
Publication number	US-12243569-B2
Application number	US-202318215392-A
Country	US
Kind code	B2
Filing date	Jun 28, 2023
Priority date	Jan 21, 2020
Publication date	Mar 4, 2025
Grant date	Mar 4, 2025

Abstract

A magnetic recording medium is a magnetic recording medium having a tape shape and includes a substrate, an underlayer provided on the substrate, and a magnetic layer provided on the underlayer. The magnetic layer has a surface having an uneven shape, a height range ΔH obtained from statistical information of a height of the uneven shape is in a range of 4.00 nm≤ΔH≤10.00 nm, and a gradient range ΔA obtained from statistical information of a gradient of the uneven shape is in a range of 2.50 degrees≤ΔA.

First claim

The invention claimed is:

1. A magnetic recording medium comprising:
a substrate;
an underlayer disposed on the substrate; and
a magnetic layer disposed on the underlayer,
wherein the magnetic layer has a surface having an uneven shape,
wherein a height range ΔH obtained from a statistical information of a height of the uneven shape is in a range of 4.00 nm≤ΔH≤10.00 nm,
wherein a gradient range ΔA obtained from a statistical information of a gradient of the uneven shape is in a range of 2.50 degrees≤ΔA,
wherein an average thickness of the magnetic recording medium is 5.3 μm or less, and
wherein the substrate includes a polyester.

2. The magnetic recording medium according to claim 1 , wherein the gradient range ΔA is in a range of 2.50 degrees≤ΔA≤5.00 degrees.

3. The magnetic recording medium according to claim 1 , wherein the height range ΔH is in a range of 4.00 nm≤ΔH≤8.50 nm.

4. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium includes a lubricant, and
wherein an amount S of oozing of the lubricant per unit area of 12.5 μm×9.3 μm on the surface of the magnetic layer in vacuum is in a range of 3.0 μm 2 ≤S≤6.5 μm 2 .

5. The magnetic recording medium according to claim 4 , wherein the lubricant includes one or both of a fatty acid and a fatty acid ester.

6. The magnetic recording medium according to claim 1 , wherein a friction coefficient ratio (μB/μA) between a dynamic friction coefficient μB obtained after full-scale recording/full-scale reproduction is performed twice and a dynamic friction coefficient μA before the full-scale recording/full-scale reproduction is performed is less than 2.0.

7. The magnetic recording medium according to claim 1 , wherein a squareness ratio of the magnetic layer in a vertical direction of the magnetic recording medium is 65% or more.

8. The magnetic recording medium according to claim 1 , wherein an average thickness of the magnetic layer is 80 nm or less.

9. The magnetic recording medium according to claim 1 , wherein an average thickness of the substrate is 4.4 μm or less.

10. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes a magnetic powder that includes a hexagonal ferrite, and
an average particle volume of the magnetic powder is 1600 nm 3 or less.

11. The magnetic recording medium according to claim 10 , wherein the average particle volume of the magnetic powder is 1300 nm 3 or less.

12. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes a magnetic powder, and
the magnetic powder contains hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite.

13. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer is configured to be able to form a plurality of data tracks, and
a width of the data track is 2000 nm or less.

14. The magnetic recording medium according to claim 1 , wherein a coercive force Hc of the magnetic layer in a longitudinal direction is 1000 Oe or more.

15. The magnetic recording medium according to claim 1 , wherein a Young's modulus in a longitudinal direction of the magnetic recording medium is 7.5 Gpa or less.

16. The magnetic recording medium according to claim 1 , wherein the magnetic layer includes a magnetic powder, and wherein an average aspect ratio of the magnetic powder ranges from 1.0 to 3.0.

17. The magnetic recording medium according to claim 1 , wherein a ratio Hc2/Hcl of a coercive force Hcl of the magnetic layer in a vertical direction to a coercive force Hc2 of the magnetic layer in a longitudinal direction is Hc2/Hcl≤0.8.

18. The magnetic recording medium according to claim 1 , wherein the magnetic recording medium includes a back layer disposed on the substrate, and wherein a surface roughness of the back layer R b ≤6.0 nm.

19. The magnetic recording medium according to claim 1 , wherein a squareness ratio of the magnetic layer in a longitudinal direction of the magnetic recording medium is 35% or less.

20. A cartridge comprising the magnetic recording medium according to claim 1 .

Assignees

• Sony Group Corp

Inventors

• Sekiguchi Noboru
• Kamoshita Yuuko
• Yamaga Minoru

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• G11B5/78

  Tape carriers · CPC title

• G11B5/5928

  Longitudinal tracks · CPC title

• G11B5/71 Primary

  characterised by the lubricant · CPC title