MAGNETIC TAPE

• US 20150380036A1
• Filed: 06/29/2015
• Published: 12/31/2015
• Est. Priority Date: 06/30/2014
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: KASADA, Norihito, TADA, Toshio, OYANAGI, Masahito
• Granted Patent: US 9,601,146 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

An aspect of the present invention relates to a magnetic tape comprising a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support, wherein ΔSFD in a longitudinal direction of the magnetic tape as calculated with Equation 1 ranges from 0.35 to 1.50:

ΔSFD=SFD_{25° C.}−SFD_{−190° C.}  Equation 1

wherein, in Equation 1, SFD_{25° C.} 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_{−190° C.} 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.

Claims

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

Δ

SFD in a longitudinal direction of the magnetic tape as calculated with Equation 1 ranges from 0.35 to 1.50;

Δ

SFD=SFD<sub>25°

C.</sub>−

SFD<sub>−

190°

C.</sub> 

 

Equation 1

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 a coercive force Hc in the longitudinal direction of the magnetic tape ranges from 96 kA/m to 279 kA/m.

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

5. The magnetic tape according to claim 1, which has a magnetic tape thickness of less than or equal to 6.0 μ

m.

6. The magnetic tape according to claim 2, which has a magnetic tape thickness of less than or equal to 6.0 μ

m.

7. The magnetic tape according to claim 3, which has a magnetic tape thickness of less than or equal to 6.0 μ

m.

8. The magnetic tape according to claim 4, which has a magnetic tape thickness of less than or equal to 6.0 μ

m.

9. The magnetic tape according to claim 1, which has a centerline average surface roughness Ra of a surface of the magnetic layer as measured with a noncontact surface profile measuring apparatus of less than or equal to 1.8 nm.

10. The magnetic tape according to claim 1, which has a centerline average surface roughness Ra of a surface of the magnetic layer as measured with an atomic force microscope of less than or equal to 2.5 nm.

11. The magnetic tape according to claim 1, wherein the magnetic layer further comprises an abrasive.

12. The magnetic tape according to claim 1, wherein the magnetic layer further comprises nonmagnetic colloidal particles.

13. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder with an average particle size ranging from 10 nm to 50 nm.

14. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic metal powder with an average particle size ranging from 10 nm to 50 nm.

15. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic powder in which a difference Δ

SFD_powder between SFD as measured in an environment with a temperature of 100°

C. and SFD as measured in an environment with a temperature of 25°

C. as calculated with Equation 2 ranges from 0.05 to 1.50;

Δ

SFD_powder=SFD<sub>powder 100°

C.</sub>−

SFD<sub>powder 25°

C.</sub> 

 

Equation 2

wherein, in Equation 2, SFD<sub>powder 100°

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

C. and SFD<sub>powder 25°

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

C.

16. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic hexagonal ferrite powder in which a difference Δ

SFD_powder between SFD as measured in an environment with a temperature of 100°

C. and SFD as measured in an environment with a temperature of 25°

C. as calculated with Equation 2 ranges from 0.05 to 1.50;

Δ

SFD_powder=SFD<sub>powder 100°

C.</sub>−

SFD<sub>powder 25°

C.</sub> 

 

Equation 2

wherein, in Equation 2, SFD<sub>powder 100°

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

C. and SFD<sub>powder 25°

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

C.

17. The magnetic tape according to claim 16, wherein the ferromagnetic hexagonal ferrite powder has an average particle size ranging from 10 nm to 50 nm.

18. The magnetic tape according to claim 1, wherein the ferromagnetic powder is ferromagnetic metal powder in which a difference Δ

SFD_powder between SFD as measured in an environment with a temperature of 100°

C. and SFD as measured in an environment with a temperature of 25°

C. as calculated with Equation 2 ranges from 0.05 to 1.50;

Δ

SFD_powder=SFD<sub>powder 100°

C.</sub>−

SFD<sub>powder 25°

C.</sub> 

 

Equation 2

wherein, in Equation 2, SFD<sub>powder 100°

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

C. and SFD<sub>powder 25°

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

C.

19. The magnetic tape according to claim 18, wherein the ferromagnetic metal powder has an average particle size ranging from 10 nm to 50 nm.