Magnetic tape

• US 9,704,525 B2
• Filed: 03/17/2016
• Issued: 07/11/2017
• Est. Priority Date: 03/18/2015
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kasada, Norihito
• Primary Examiner(s): BERNATZ, KEVIN M
• Application Number:
  US15/072,550
• Publication Number:
  US 20160276076A1
• Time in Patent Office: 481 Days
• Field of Search: None
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles
• CPC Class Codes: H01F 1/113 in a bonding agent

Abstract

The magnetic tape includes a magnetic layer containing ferromagnetic hexagonal ferrite powder, abrasive, and binder on a nonmagnetic support, wherein the ferromagnetic hexagonal ferrite powder exhibits an activation volume of less than or equal to 1,800 nm³, and inclination, cos θ, of the ferromagnetic hexagonal ferrite powder relative to a surface of the magnetic layer as determined by sectional observation by a scanning electron transmission microscope is greater than or equal to 0.85 but less than or equal to 1.00.

Claims

1. A magnetic tape,

which comprises a magnetic layer comprising ferromagnetic hexagonal ferrite powder, abrasive, and binder on a nonmagnetic support,

wherein the ferromagnetic hexagonal ferrite powder exhibits an activation volume of less than or equal to 1,800 nm³,

inclination, cos θ

, of the ferromagnetic hexagonal ferrite powder relative to a surface of the magnetic layer as determined by sectional observation by a scanning electron transmission microscope is greater than or equal to 0.85 but less than or equal to 0.98, and

among all hexagonal ferrite particles included in the ferromagnetic hexagonal ferrite powder in the magnetic layer, the proportion accounted for by hexagonal ferrite particles having a length in the major axis direction of greater than or equal to 10 nm and having an aspect ratio ranging from 1.5 to 6.0 is greater than or equal to 50% but less than or equal to 95%.

2. The magnetic tape according to claim 1,

wherein the abrasive comprises alumina.

3. The magnetic tape according to claim 1,

which comprises a nonmagnetic layer comprising nonmagnetic powder and binder between the nonmagnetic support and the magnetic layer.

4. The magnetic tape according to claim 1,

wherein the inclination, cos θ

, is greater than or equal to 0.89 but less than or equal to 0.98.

5. The magnetic tape according to claim 1,

wherein the ferromagnetic hexagonal ferrite powder exhibits an activation volume of greater than or equal to 800 nm³ but less than or equal to 1,800 nm³.

6. The magnetic tape according to claim 1,

wherein a centerline average surface roughness Ra that is measured with a noncontact surface profile measuring device is greater than or equal to 0.2 nm but less than or equal to 1.8 nm on the surface of the magnetic layer.

7. The magnetic tape according to claim 1,

wherein the magnetic layer further comprises nonmagnetic colloidal particles.

8. The magnetic tape according to claim 1,

wherein the magnetic layer further comprises a polyester chain-containing compound with a weight average molecular weight of greater than or equal to 1,000 but less than or equal to 80,000.

9. The magnetic tape according to claim 8,

wherein the polyester chain-containing compound has a partial structure denoted by formula A below:

10. The magnetic tape according to claim 8,

wherein the polyester chain-containing compound comprises at least one group selected from the group consisting of a carboxyl group and a carboxyl salt.

11. The magnetic tape according to claim 9,

wherein the polyester chain-containing compound comprises at least one group selected from the group consisting of a carboxyl group and a carboxyl salt.

12. The magnetic tape according to claim 8,

wherein the polyester chain-containing compound comprises at least one polyalkyleneimine chain.

13. The magnetic tape according to claim 9,

wherein the polyester chain-containing compound comprises at least one polyalkyleneimine chain.

14. The magnetic tape according to claim 8,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.

15. The magnetic tape according to claim 9,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.

16. The magnetic tape according to claim 10,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.

17. The magnetic tape according to claim 11,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.

18. The magnetic tape according to claim 12,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.

19. The magnetic tape according to claim 13,

wherein the magnetic layer comprises 0.5 to 25.0 weight parts of the polyester chain-containing compound per 100.0 weight parts of the ferromagnetic powder.