Magnetic recording medium and method of manufacturing the same

• US 9,721,607 B2
• Filed: 06/29/2016
• Issued: 08/01/2017
• Est. Priority Date: 06/30/2015
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Sugishima, Akinori, Yamashita, Tatsuya, Oyanagi, Masahito, Tada, Toshio, Kasada, Norihito
• Primary Examiner(s): BERNATZ, KEVIN M
• Application Number:
  US15/197,046
• Publication Number:
  US 20170004856A1
• Time in Patent Office: 398 Days
• Field of Search: None
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/842 Coating a support with a liquid magnetic dispersion

Abstract

The magnetic recording medium has a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, and the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,400 nm³, and a ratio of the crystallite size D_x(107) obtained from a diffraction peak of a (107) plane to a particle size in a direction of an easy axis of magnetization D_TEM as determined by observation with a transmission electron microscope, D_x(107)/D_TEM, is greater than or equal to 1.1.

Claims

1. A magnetic recording medium,

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

wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, and

the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,400 nm³, and a ratio of the crystallite size D_x(107) obtained from a diffraction peak of a (107) plane to a particle size in a direction of an easy axis of magnetization D_TEM as determined by observation with a transmission electron microscope, D_x(107)/D_TEM, is greater than or equal to 1.1.

2. The magnetic recording medium according to claim 1,

wherein the ferromagnetic hexagonal ferrite powder has the D_x(107)/D_TEM of greater than or equal to 1.1 but less than or equal to 1.5.

3. The magnetic recording medium according to claim 1,

wherein the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,000 nm³.

4. The magnetic recording medium according to claim 2,

wherein the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,000 nm³.

5. The magnetic recording medium according to claim 1,

wherein the ferromagnetic hexagonal ferrite powder has an average particle size ranging from 8 nm to 50 nm.

6. The magnetic recording medium according to claim 1,

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

7. A method of manufacturing a magnetic recording medium,

wherein the magnetic recording medium is a magnetic recording medium comprising a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support,

wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, and

the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,400 nm³, and a ratio of the crystallite size D_x(107) obtained from a diffraction peak of a (107) plane to a particle size in a direction of an easy axis of magnetization D_TEM as determined by observation with a transmission electron microscope, D_x(107)/D_TEM, is greater than or equal to 1.1, and

the method comprises:

forming a magnetic layer through preparation of a magnetic layer-forming composition and coating of the magnetic layer-forming composition that has been prepared on a nonmagnetic support, either directly, or indirectly over at least one other layer,

wherein the preparation of the magnetic layer-forming composition comprises;

a first stage of dispersing ferromagnetic hexagonal ferrite powder, binder, and solvent in the presence of first dispersion beads to obtain a dispersion, and

a second stage of dispersing the dispersion obtained in the first stage in the presence of second dispersion beads of smaller bead diameter and lower density than the first dispersion beads.

8. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the second stage is conducted in the presence of a quantity of second dispersion beads that is greater than or equal to 10-fold a quantity of ferromagnetic hexagonal ferrite powder based on weight.

9. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the bead diameter of the second dispersion beads is less than or equal to 1/100 the bead diameter of the first dispersion beads.

10. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the bead diameter of the second dispersion beads ranges from 80 nm to 1,000 nm.

11. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the density of the second dispersion beads is less than or equal to 3.7 g/cm³.

12. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the second dispersion beads are diamond beads.

13. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the ferromagnetic hexagonal ferrite powder has the D_x(107)/D_TEM of greater than or equal to 1.1 but less than or equal to 1.5.

14. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,000 nm³.

15. The method of manufacturing a magnetic recording medium according to claim 13,

wherein the ferromagnetic hexagonal ferrite powder has a crystallite volume as determined by X-ray diffraction analysis ranges from 1,000 nm³ to 2,000 nm³.

16. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the ferromagnetic hexagonal ferrite powder has an average particle size ranging from 8 nm to 50 nm.

17. The method of manufacturing a magnetic recording medium according to claim 7,

wherein the magnetic recording medium comprises a nonmagnetic layer comprising nonmagnetic powder and binder between the nonmagnetic support and the magnetic layer.