Magnetic recording medium

• US 6,770,359 B2
• Filed: 08/29/2002
• Issued: 08/03/2004
• Est. Priority Date: 09/03/2001
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fuji Photo Film Co Limited (Fujifilm Holdings Corporation)
• Inventors: Masaki, Kouichi
• Primary Examiner(s): Resan, Stevan A.
• Application Number:
  US10/230,226
• Publication Number:
  US 20030124386A1
• Time in Patent Office: 705 Days
• Field of Search: 428/329, 428/336, 428/694.BH
• US Class Current: 428/842.8
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: Y10T 428/265 1 mil or less

Abstract

A magnetic recording medium comprising a support having provided thereon a nonmagnetic layer containing a nonmagnetic powder dispersed in a binder and a magnetic layer containing a ferromagnetic powder dispersed in a binder provided on the nonmagnetic layer, wherein the magnetic layer comprises a hexagonal ferrite powder having an average tabular diameter of from 10 to 35 nm, a coercive force (Hc) of from 135 to 400 kA/m, SFD (Switching Field Distribution) (25° C.) of from 0.40 to 0.90, and Δ SFD [SFD (100° C.)−SFD (25° C.)] of from 0.15 to 0.20.

Claims

1. A magnetic recording medium comprising a support having provided thereon a nonmagnetic layer containing a nonmagnetic powder dispersed in a binder and a magnetic layer containing a ferromagnetic powder dispersed in a binder provided on the nonmagnetic layer, wherein the magnetic layer comprises a hexagonal ferrite powder having an average tabular diameter of from 10 to 35 nm, a coercive force (Hc) of from 135 to 400 kA/m, SFD (Switching Field Distribution) (25°

C.) of from 0.40 to 0.90, and Δ

SFD [SFD (100°

C.)−

SFD (25°

C.)] of from −

0.15 to 0.20.

2. The magnetic recording medium as in claim 1, wherein the magnetic recording medium has a value of a residual magnetic flux density x a magnetic layer thickness of from 0.5 to 100 mT.μ

m.

3. The magnetic recording medium as in claim 1, wherein the magnetic layer has a squareness ratio of from 0.50 to 0.70.

4. The magnetic recording medium as in claim 2, wherein the magnetic layer thickness is from 0.01 to 0.5 μ

m.

5. The magnetic recording medium as in claim 2, wherein the residual magnetic flux density is from 70 to 200 mT.

6. The magnetic recording medium as in claim 1, wherein the magnetic recording medium has a thermal fluctuation magnetic field (Hf) of from 0 to 2.0 kA/m.

7. The magnetic recording medium as in claim 1, wherein the hexagonal ferrite powder is produced by the steps of:

forming a complex containing starting materials for elements constituting the hexagonal ferrite and a citric acid;

thermal decomposing the complex; and

subjecting the decomposed complex to a glass crystallization method.