MAGNETIC RECORDING MEDIUM AND COATING COMPOSITION FOR MAGNETIC RECORDING MEDIUM

• US 20140374645A1
• Filed: 06/23/2014
• Published: 12/25/2014
• Est. Priority Date: 06/24/2013
• Status: Abandoned Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: KIKUCHI, Wataru, AOSHIMA, Toshihide, KANEKO, Yuushi, KATAYAMA, Kazutoshi, MEGURO, Katsuhiko
• Application Number:
  US14/311,894
• Publication Number:
  US 20140374645A1
• Time in Patent Office: Days
• US Class Current: 252/62.54
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent

Abstract

An aspect of the present invention relates to a magnetic recording medium comprising a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein an average particle size of the ferromagnetic powder is equal to or less than 50 nm, the magnetic layer further comprises a compound, and the compound comprises at least one polyalkyleneimine chain and at least one polyester chain, with a proportion in the compound accounted for by the polyalkyleneimine chain being less than 5.0 weight percent and a number average molecular weight of the polyalkyleneimine chain ranging from 300 to 3,000.

Claims

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

an average particle size of the ferromagnetic powder is equal to or less than 50 nm;

the magnetic layer further comprises a compound; and

the compound comprises at least one polyalkyleneimine chain and at least one polyester chain, with a proportion in the compound accounted for by the polyalkyleneimine chain being less than 5.0 weight percent and a number average molecular weight of the polyalkyleneimine chain ranging from 300 to 3,000.

2. The magnetic recording medium according to claim 1, wherein the polyester chain comprises at least one polyester chain selected from the group consisting of a polyester chain denoted by formula 1 and a polyester chain denoted by formula 2:

3. The magnetic recording medium according to claim 2, wherein the polyester chain comprises at least one polyester chain selected from the group consisting of:

the polyester chain denoted by formula 1, wherein X¹ denotes a monovalent substituent selected from the group consisting of an alkyl group, haloalkyl group, alkoxy group, polyalkyleneoxyalkyl group, and aryl group; and

the polyester chain denoted by formula 2, wherein X² denotes a monovalent substituent selected from the group consisting of an alkyl group, haloalkyl group, alkoxy group, and aryl group.

4. The magnetic recording medium according to claim 1, wherein the compound is a reaction product of polyalkyleneimine having a number average molecular weight ranging from 300 to 3,000 and polyester having a number average molecular weight ranging from 200 to 100,000.

5. The magnetic recording medium according to claim 4, wherein the polyalkyleneimine is a polymer of identical or different alkyleneimines having 2 to 4 carbon atoms.

6. The magnetic recording medium according to claim 1, wherein the magnetic layer comprises 0.5 weight part to 50 weight parts of the compound per 100 weight parts of the ferromagnetic powder.

7. The magnetic recording medium according to claim 1, wherein the ferromagnetic powder is hexagonal ferrite powder having an average plate diameter ranging from 10 nm to 50 nm.

8. The magnetic recording medium according to claim 1, wherein the ferromagnetic powder is ferromagnetic metal powder having an average major axis length ranging from 10 nm to 50 nm.

9. A coating composition, which is a coating composition for a magnetic recording medium and comprises:

ferromagnetic powder having an average particle size of equal to or less than 50 nm;

a compound comprising at least one polyalkyleneimine chain and at least one polyester chain, with a proportion in the compound accounted for by the polyalkyleneimine chain being less than 5.0 weight percent and a number average molecular weight of the polyalkyleneimine chain ranging from 300 to 3,000; and

a solvent.

10. The coating composition according to claim 9, wherein the polyester chain comprises at least one polyester chain selected from the group consisting of a polyester chain denoted by formula 1 and a polyester chain denoted by formula 2:

11. The coating composition according to claim 10, wherein the polyester chain comprises at least one polyester chain selected from the group consisting of:

the polyester chain denoted by formula 1, wherein X¹ denotes a monovalent substituent selected from the group consisting of an alkyl group, haloalkyl group, alkoxy group, polyalkyleneoxyalkyl group, and aryl group; and

the polyester chain denoted by formula 2, wherein X² denotes a monovalent substituent selected from the group consisting of an alkyl group, haloalkyl group, alkoxy group, and aryl group.

12. The coating composition according to claim 9, wherein the compound is a reaction product of polyalkyleneimine having a number average molecular weight ranging from 300 to 3,000 and polyester having a number average molecular weight ranging from 200 to 100,000.

13. The coating composition according to claim 12, wherein the polyalkyleneimine is a polymer of identical or different alkyleneimines having 2 to 4 carbon atoms.

14. The coating composition according to claim 9, which comprises 0.5 weight part to 50 weight parts of the compound per 100 weight parts of the ferromagnetic powder.

15. The coating composition according to claim 9, which further comprises binder.

16. The coating composition according to claim 9, which further comprises a curing agent.

17. The coating composition according to claim 9, wherein the solvent is a ketone solvent.

18. The coating composition according to claim 9, wherein the ferromagnetic powder is hexagonal ferrite powder having an average plate diameter ranging from 10 nm to 50 nm.

19. The coating composition according to claim 9, wherein the ferromagnetic powder is ferromagnetic metal powder having an average major axis length ranging from 10 nm to 50 nm.