MAGNETIC TAPE

• US 20180240493A1
• Filed: 02/20/2018
• Published: 08/23/2018
• Est. Priority Date: 02/20/2017
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: TADA, Toshio, KASADA, Norihito
• Granted Patent: US 10,431,250 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70615 containing Fe metal or alloys G11B5/70621 takes precedence
• CPC Class Codes: G11B 5/712 characterised by the surface treatment or coating of magnetic particles

Abstract

The magnetic tape includes a non-magnetic support; and a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support, in which a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm, a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and ΔSFD in a longitudinal direction of the magnetic tape calculated by Expression 1: ΔSFD=SFD_{25° C.}−SFD_{−190° C.} is equal to or greater than 0.35. In Expression 1, the SFD_{25° C.} is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25° C., and the SFD_{−190° C.} is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −190° C.

Claims

1. A magnetic tape comprising:

a non-magnetic support; and

a magnetic layer including ferromagnetic powder and a binding agent on the non-magnetic support,

wherein a center line average surface roughness Ra measured regarding a surface of the magnetic layer is equal to or smaller than 1.8 nm,

a logarithmic decrement acquired by a pendulum viscoelasticity test performed regarding the surface of the magnetic layer is equal to or smaller than 0.050, and

Δ

SFD in a longitudinal direction of the magnetic tape calculated by Expression 1 is equal to or greater than 0.35,

Δ

SFD=SFD<sub>25°

C.</sub>−

SFD<sub>−

190°

C.</sub> 

 

Expression 1

in Expression 1, the SFD<sub>25°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of 25°

C., and the SFD<sub>−

190°

C.</sub> is a switching field distribution SFD measured in a longitudinal direction of the magnetic tape at a temperature of −

190°

C.

2. The magnetic tape according to claim 1,

wherein the logarithmic decrement is 0.010 to 0.050.

3. The magnetic tape according to claim 1,

wherein the center line average surface roughness Ra is 1.2 nm to 1.8 nm.

4. The magnetic tape according to claim 2,

wherein the center line average surface roughness Ra is 1.2 nm to 1.8 nm.

5. The magnetic tape according to claim 1,

wherein the Δ

SFD is 0.35 to 1.50.

6. The magnetic tape according to claim 2,

wherein the Δ

SFD is 0.35 to 1.50.

7. The magnetic tape according to claim 3,

wherein the Δ

SFD is 0.35 to 1.50.

8. The magnetic tape according to claim 4,

wherein the Δ

SFD is 0.35 to 1.50.

9. The magnetic tape according to claim 1, further comprising:

a non-magnetic layer including non-magnetic powder and a binding agent between the non-magnetic support and the magnetic layer.

10. The magnetic tape according to claim 1, further comprising:

a back coating layer including non-magnetic powder and a binding agent on a surface side of the non-magnetic support opposite to a surface side provided with the magnetic layer.