Magnetic recording medium and production method thereof

• US 6,207,252 B1
• Filed: 06/24/1998
• Issued: 03/27/2001
• Est. Priority Date: 06/24/1998
• Status: Expired due to Fees

• Current Assignee: Verbatim Corporation (Mitsubishi Chemical Group Corp.)
• Original Assignee: Verbatim Corporation (Mitsubishi Chemical Group Corp.)
• Inventors: Shimomura, Osamu
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US09/103,792
• Time in Patent Office: 1,007 Days
• Field of Search: 428/141, 428/323, 428/336, 428/694 BS, 428/694 BR, 428/900, 428/328, 428/329
• US Class Current: 428/141
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/733 characterised by the addition of non-magnetic particles base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739
• CPC Class Codes: G11B 5/7334 Base layer characterised by composition or structure
• CPC Class Codes: Y10S 428/90 Magnetic feature
• CPC Class Codes: Y10T 428/24355 Continuous and nonuniform or irregular surface on layer or component [e.g., roofing, etc.]
• CPC Class Codes: Y10T 428/25 Web or sheet containing structurally defined element or component and including a second component containing structurally defined particles
• CPC Class Codes: Y10T 428/256 Heavy metal or aluminum or compound thereof
• CPC Class Codes: Y10T 428/257 Iron oxide or aluminum oxide
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A magnetic recording medium is formed on a non-magnetic support and a magnetic layer containing a binder and a ferromagnetic powder and having a thickness of 0.7 μm or thinner is formed on the non-magnetic support wherein the surface roughness Ra of the surface of the medium is from 0.5 to 7 nm and the skewness R_SK of the surface of the medium is 0.1 or lower.

The magnetic recording medium preferably has a nonmagnetic underlayer containing a binder and non-magnetic particles such as carbon black, between the non-magnetic support and the magnetic layer. The magnetic recording medium has excellent electromagnetic recording characteristics and torque characteristics and is suitable for high-density recording.

Claims

1. A magnetic recording medium comprising:

a non-magnetic support including a non-magnetic layer formed thereon containing a binder and non-magnetic particles including carbon black in a ratio by weight of about 2 to 50 parts binder to 100 parts non-magnetic particles; and

a magnetic layer formed on the non-magnetic layer containing a binder and a ferromagnetic powder and having a thickness not greater than about 0.7 μ

m, wherein the surface roughness Ra of the surface of the magnetic recording medium is in the range from 0.5 to 7 nm and the skewness R_SK of the surface of the magnetic recording medium is 0.1 or lower.

2. A magnetic recording medium of claim 1, wherein R_SK is 0 or lower.

3. A magnetic recording medium of claim 1, wherein the ferromagnetic powder contains an acicular metal powder.

4. A magnetic recording medium of claim 3, wherein the specific surface area of the acicular metal powder determined by the BET method is at least 35 m²/g.

5. A magnetic recording medium of claim 3, wherein the coercive force of the acicular metal powder is at least 1,500 Oe.

6. A magnetic recording medium of claim 3, wherein saturated magnetization of the acicular metal powder is at least 140 emu/g.

7. A magnetic recording medium of claim 3, wherein the mean long axis length of the acicular metal powder is 0.20 μ

m or shorter.

8. A magnetic recording medium of claim 3, wherein the aspect ratio of the acicular metal powder is 10 or lower.

9. A magnetic recording medium of claim 1, wherein the ferromagnetic powder contains a hexagonal system ferromagnetic powder.

10. A magnetic recording medium of claim 9, wherein the coercive force of the hexagonal system ferromagnetic powder is at least 1500 Oe.

11. A magnetic recording medium of claim 9, wherein the plate diameter of the hexagonal system ferromagnetic powder is 0.2 μ

m or shorter.

12. A magnetic recording medium of claim 9, wherein the aspect ratio of the hexagonal system ferromagnetic powder is 10 or lower.

13. A magnetic recording medium of claim 1, wherein the mean primary particle size of the carbon black is in the range from 15 to 30 nm.

14. A magnetic recording medium of claim 1, wherein the specific surface area of the carbon black determined by the BET method is in the range from 100 to 300 m²/g.

15. A magnetic recording medium of claim 1, wherein the DBP oil absorption of the carbon black is in the range from 50 to 100 g/100 cc.

16. A magnetic recording medium according to claim 1 in which the thickness of the non-magnetic layer is at least approximately 1 micron.

17. A magnetic recording medium according to claim 1 including a lubricant in the non-magnetic layer.

18. A magnetic recording medium according to claim 17 in which the lubricant includes one of a fatty acid and fatty acid ester.

19. The magnetic recording medium according to claim 1 wherein the ratio is about 30 parts binder to 100 parts non-magnetic particles.

20. A magnetic recording medium according to claim 1 in which the surface roughness of the surface of the magnetic recording medium is non-abrasively established.