MAGNETIC TAPE AND METHOD OF MANUFACTURING THE SAME

• US 20170186456A1
• Filed: 12/22/2016
• Published: 06/29/2017
• Est. Priority Date: 12/25/2015
• Status: Active Application

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: TADA, Toshio, KASADA, Norihito, OYANAGI, Masahito
• Granted Patent: US 10,573,341 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/708 characterised by addition of non-magnetic particles to the layer
• CPC Class Codes: G11B 5/712 characterised by the surface treatment or coating of magnetic particles
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/78 Tape carriers
• CPC Class Codes: G11B 5/845 in a magnetic field

Abstract

The magnetic tape has a nonmagnetic layer containing nonmagnetic powder and binder on a nonmagnetic support and a magnetic layer containing ferromagnetic powder and binder on the nonmagnetic layer, wherein a fatty acid ester is contained in at least the magnetic layer, the ferromagnetic powder is ferromagnetic hexagonal ferrite powder, 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 ΔSFD in a longitudinal direction of the magnetic tape as calculated with Equation 1: ΔSFD=SFD_{25° C.}−SFD_{−190° C.}, ranges from 0.50 to 1.60.

Claims

1. A magnetic tape,

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

a fatty acid ester is contained in at least the magnetic layer;

the ferromagnetic powder is ferromagnetic hexagonal ferrite powder;

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 a 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

Δ

SFD in a longitudinal direction of the magnetic tape as calculated with Equation 1 ranges from 0.50 to 1.60;

Equation 1

Δ

SFD=SFD_25°

C.−

SFD<sub>−

190°

C.</sub>

wherein, in Equation 1, SFD<sub>25°

C.</sub> denotes a switching field distribution SFD as measured in the longitudinal direction of the magnetic tape in an environment with a temperature of 25°

C., and SFD<sub>−

190°

C.</sub> denotes a switching field distribution SFD as measured in the longitudinal direction of the magnetic tape in an environment with a temperature of −

190°

C.

2. The magnetic tape according to claim 1,

wherein the D_x(107)/D_TEM of the ferromagnetic hexagonal ferrite powder falls within a range of 1.1 to 1.5.

3. The magnetic tape according to claim 1,

wherein the crystallite volume as determined by X-ray diffraction of the ferromagnetic hexagonal ferrite powder falls within a range of 1,000 nm³ to 1,500 nm³.

4. The magnetic tape according to claim 2,

wherein the crystallite volume as determined by X-ray diffraction of the ferromagnetic hexagonal ferrite powder falls within a range of 1,000 nm³ to 1,500 nm³.

5. The magnetic tape according to claim 1,

wherein the Δ

SFD falls within a range of 0.50 to 1.00.

6. The magnetic tape according to claim 2,

wherein. the Δ

SFD falls within a range of 0.50 to 1.00.

7. The magnetic tape according to claim 3,

wherein the Δ

SFD falls within a range of 0.50 to 1.00.

8. The magnetic tape according to claim 4,

wherein the Δ

SFD falls within a range of 0.50 to 1.00.

9. A method of manufacturing a magnetic tape,

wherein the magnetic tape is a magnetic tape which comprises a nonmagnetic layer comprising nonmagnetic powder and binder on a nonmagnetic support and a magnetic layer comprising ferromagnetic powder and binder on the nonmagnetic layer, wherein

a fatty acid ester is contained in at least the magnetic layer;

the ferromagnetic powder is ferromagnetic hexagonal ferrite powder;

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 a 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

Δ

SFD in a longitudinal direction of the magnetic tape as calculated with Equation 1 ranges from 0.50 to 1.60;

Equation 1

Δ

SFD=SFD<sub>25°

C.</sub>−

SFD<sub>190°

C.</sub>

wherein, in Equation 1, SFD<sub>25°

C.</sub> denotes a switching field distribution SFD as measured in the longitudinal direction of the magnetic tape in an environment with a temperature of 25°

C., and SFD<sub>−

190°

C.</sub> denotes a switching field distribution SFD as measured in the longitudinal direction of the magnetic tape in an environment with a temperature of −

190°

C.; and

wherein 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 layer that has been formed on a nonmagnetic support,

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.

10. The method of manufacturing a magnetic tape according to claim 9,

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 the quantity of ferromagnetic hexagonal ferrite powder based on weight.

11. The method of manufacturing a magnetic tape according to claim 9,

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.

12. The method of manufacturing a magnetic tape according to claim 9,

wherein the bead diameter of the second dispersion beads falls within a range of 80 nm to 1,000 nm.

13. The method of manufacturing a magnetic tape according to claim 9,

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

14. The method of manufacturing a magnetic tape according to claim 9,

wherein the second dispersion beads are diamond beads.

15. The method of manufacturing a magnetic tape according to claim 9,

wherein the first stage obtains a liquid dispersion by dispersion processing solvent, binder, and ferromagnetic hexagonal ferrite powder having a Δ

SFD_powder as calculated by Equation 2 that falls within a range of 0.05 to 1.90;

Equation 2

Δ

SFD_powder=SFD<sub>powder100°

C.</sub>−

SFD<sub>powder25°

C.</sub>

in the presence of first dispersion beads, wherein, in Equation 2, SFD<sub>powder100°

C.</sub> denotes a switching field distribution SFD of the ferromagnetic hexagonal ferrite powder as measured in an environment with a temperature of 100°

C., and SFD<sub>powder25°

C.</sub> denotes a switching field distribution SFD of the, ferromagnetic hexagonal ferrite powder as measured in an environment with a temperature of 25°

C.

16. The method of manufacturing a magnetic tape according to claim 9,

wherein the D_x(107)/D_TEM of the ferromagnetic hexagonal ferrite powder contained in the magnetic layer of the magnetic tape falls within a range of 1/1 to 1.5.

17. The method of manufacturing a magnetic tape according to claim 9,

wherein the crystallite volume as determined by X-ray diffraction of the ferromagnetic hexagonal ferrite powder contained in the magnetic layer of the magnetic tape falls within a range of 1,000 nm³ to 1,500 nm³.