MAGNETIC RECORDING MEDIUM AND METHOD OF MANUFACTURING THE SAME

• US 20130260179A1
• Filed: 03/15/2013
• Published: 10/03/2013
• Est. Priority Date: 03/30/2012
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: KASADA, Norihito, SATO, Masahide, WATANABE, Isamu
• Granted Patent: US 9,401,171 B2
• Time in Patent Office: Days
• US Class Current: 428/840.2
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles
• CPC Class Codes: G11B 5/842 Coating a support with a liquid magnetic dispersion

Abstract

An aspect of the present invention relates to a magnetic recording medium, which comprises a nonmagnetic layer containing a nonmagnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder in this order on a nonmagnetic support, wherein the nonmagnetic layer has a thickness of equal to or less than 300 nm; a composite elastic modulus as measured on a surface of the magnetic layer ranges from 6.0 to 8.0 GPa; the magnetic layer comprises an abrasive with a specific surface area by BET method ranging from 14 m²/g to 40 m²/g; and a surface abrasive occupancy on a surface of the magnetic layer ranges from 0.2% to 2%.

Claims

1. A magnetic recording medium, which comprises a nonmagnetic layer containing a nonmagnetic powder and a binder and a magnetic layer containing a ferromagnetic powder and a binder in this order on a nonmagnetic support, wherein

the nonmagnetic layer has a thickness of equal to or less than 300 nm;

a composite elastic modulus as measured on a surface of the magnetic layer ranges from 6.0 to 8.0 GPa;

the magnetic layer comprises an abrasive with a specific surface area by BET method ranging from 14 m²/g to 40 m²/g; and

a surface abrasive occupancy on a surface of the magnetic layer ranges from 0.2% to 2%.

2. The magnetic recording medium according to claim 1, wherein the abrasive is alumina.

3. The magnetic recording medium according to claim 2, wherein the magnetic layer further comprises an aromatic hydrocarbon compound having a phenolic hydroxyl group.

4. The magnetic recording medium according to claim 3, wherein the aromatic hydrocarbon compound having a phenolic hydroxyl group is a compound denoted by general formula (1):

5. The magnetic recording medium according to claim 3, wherein the aromatic hydrocarbon compound having a phenolic hydroxyl group is selected from the group consisting of 2,3-dihydroxylnaphthalene and derivatives thereof.

6. The magnetic recording medium according to claim 1, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive.

7. The magnetic recording medium according to claim 1, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive, and the nonmagnetic particle is a silica colloidal particle.

8. The magnetic recording medium according to claim 2, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive, and the nonmagnetic particle is a silica colloidal particle.

9. The magnetic recording medium according to claim 3, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive, and the nonmagnetic particle is a silica colloidal particle.

10. The magnetic recording medium according to claim 4, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive, and the nonmagnetic particle is a silica colloidal particle.

11. The magnetic recording medium according to claim 5, wherein the magnetic layer further comprises a nonmagnetic particle other than the abrasive, and the nonmagnetic particle is a silica colloidal particle.

12. A method of manufacturing a magnetic recording medium, which comprises:

preparing a coating material for forming a magnetic layer via a step of mixing an abrasive liquid with a magnetic liquid comprising a ferromagnetic powder, solvent, and a binder, wherein the abrasive liquid comprises an abrasive and a solvent, but essentially does not comprise a ferromagnetic powder; and

forming a magnetic layer by coating the coating material for forming a magnetic layer that has been prepared on a nonmagnetic layer containing a nonmagnetic powder and a binder to provide the magnetic recording medium according to claim 1.

13. The method of manufacturing a magnetic recording medium according to claim 12, wherein the abrasive is alumina.

14. The method of manufacturing a magnetic recording medium according to claim 12, wherein the abrasive liquid further comprises an aromatic hydrocarbon compound having a phenolic hydroxyl group, in addition to the abrasive and the solvent.

15. The method of manufacturing a magnetic recording medium according to claim 14, wherein the aromatic hydrocarbon compound having a phenolic hydroxyl group is a compound denoted by general formula (1):

16. The method of manufacturing a magnetic recording medium according to claim 14, wherein the aromatic hydrocarbon compound having a phenolic hydroxyl group is selected from the group consisting of 2,3-dihydroxylnaphthalene and derivatives thereof.

17. The method of manufacturing a magnetic recording medium according to claim 14, wherein the abrasive liquid comprises the aromatic hydrocarbon compound having a phenolic hydroxyl group in an amount ranging from 2 to 20 weight parts per 100 weight parts of the abrasive.

18. The method of manufacturing a magnetic recording medium according to claim 12, wherein the abrasive liquid further comprises a binder.

19. The method of manufacturing a magnetic recording medium according to claim 12, wherein the preparation of a coating material for forming a magnetic layer further comprises mixing a nonmagnetic liquid with the abrasive liquid and the magnetic liquid, and the nonmagnetic liquid comprises a nonmagnetic particle other than the abrasive and a solvent.

20. The method of manufacturing a magnetic recording medium according to claim 19, wherein the nonmagnetic particle is a silica colloidal particle.