MAGNETIC RECORDING MEDIUM

• US 20120183811A1
• Filed: 01/17/2012
• Published: 07/19/2012
• Est. Priority Date: 01/17/2011
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: HATTORI, Yasushi, SUZUKI, Ryota, KASADA, Norihito
• Application Number:
  US13/352,004
• Publication Number:
  US 20120183811A1
• Time in Patent Office: Days
• US Class Current: 428/836
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles
• CPC Class Codes: G11B 5/712 characterised by the surface treatment or coating of magnetic particles

Abstract

An aspect of the present invention relates to a magnetic recording medium comprising a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support, wherein the ferromagnetic powder is comprised of magnetic particles comprising a hard magnetic particle and a soft magnetic material deposited on a surface of the hard magnetic particle in a state where the soft magnetic material is exchange-coupled with the hard magnetic particle.

Claims

1. A magnetic recording medium comprising a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support, wherein

the ferromagnetic powder is comprised of magnetic particles comprising a hard magnetic particle and a soft magnetic material deposited on a surface of the hard magnetic particle in a state where the soft magnetic material is exchange-coupled with the hard magnetic particle.

2. The magnetic recording medium according to claim 1, wherein the magnetic particle has a coercive force in a range of equal to or higher than 80 kA/m but less than 240 kA/m.

3. The magnetic recording medium according to claim 1, wherein the magnetic particle has a saturation magnetization ranging from 4.0×

10<sup>−

2</sup> to 2.2 A·

m²/g.

4. The magnetic recording medium according to claim 1, wherein a carbon component is present over the hard magnetic particle on which the soft magnetic material is deposited.

5. The magnetic recording medium according to claim 1, wherein a carbon component is present in an outermost layer of the magnetic particle.

6. The magnetic recording medium according to claim 1, wherein the magnetic particle is a magnetic particle in which no peak derived from a carbon component is detected by X-ray diffraction analysis.

7. The magnetic recording medium according to claim 1, wherein the magnetic layer further comprises a component which lowers a coefficient of friction.

8. The magnetic recording medium according to claim 7, wherein

the component which lowers a coefficient of friction is a nonmagnetic inorganic particle, and

the magnetic layer further comprises an aromatic compound containing an aromatic ring in which a substituent selected from the group consisting of a hydroxyl group and a carboxyl group is directly substituted onto the aromatic ring.

9. The magnetic recording medium according to claim 7, wherein the magnetic layer comprises no carbon black.

10. The magnetic recording medium according to claim 8, wherein the magnetic layer further comprises a granular substance other than a carbon black, and the granular substance is different from the nonmagnetic inorganic particle.

11. The magnetic recording medium according to claim 8, wherein the nonmagnetic inorganic particle is an inorganic oxide colloidal particle.

12. The magnetic recording medium according to claim 11, wherein the inorganic oxide colloidal particle is a silica colloidal particle.

13. The magnetic recording medium according to claim 8, wherein the aromatic compound comprises one aromatic ring per molecule.

14. The magnetic recording medium according to claim 8, wherein the aromatic ring contained in the aromatic compound is a naphthalene ring or a biphenyl ring.

15. The magnetic recording medium according to claim 8, wherein the number of the substituent which is substituted onto the aromatic ring contained in the aromatic compound is one or two.

16. The magnetic recording medium according to claim 8, wherein the aromatic compound is dihydroxynaphthalene.

17. The magnetic recording medium according to claim 1, wherein the magnetic powder has an oxide layer over the hard magnetic particle on which the soft magnetic material is deposited.

18. The magnetic recording medium according to claim 1, wherein the hard magnetic particle is hexagonal ferrite.

19. The magnetic recording medium according to claim 1, wherein the soft magnetic material comprises a transition metal and a compound of a transition metal and oxygen.

20. The magnetic recording medium according to claim 19, wherein the compound comprises no alkaline earth metal.

21. The magnetic recording medium according to claim 19, wherein the transition metal contained in the compound is cobalt.

22. The magnetic recording medium according to claim 21, wherein the compound is CoHO₂.