Magnetic tape and method of manufacturing the same, and magnetic recording device

• US 8,681,451 B2
• Filed: 03/22/2012
• Issued: 03/25/2014
• Est. Priority Date: 03/25/2011
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Harasawa, Takeshi, Mori, Masahiko
• Primary Examiner(s): Cao, Allen T
• Application Number:
  US13/427,635
• Publication Number:
  US 20120243120A1
• Time in Patent Office: 733 Days
• Field of Search: 360/90, 360/92.1, 360/70, 360/75, 360/71
• US Class Current: 360/90
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent
• CPC Class Codes: G11B 5/70678 Ferrites

Abstract

An aspect of the present invention relates to a magnetic tape comprising a magnetic layer containing a ferromagnetic powder and a binder on a nonmagnetic support, wherein

• • the ferromagnetic powder is a hexagonal ferrite powder,
  • squareness in a vertical direction without demagnetizing field correction of the magnetic layer ranges from 0.6 to 1.0, and
  • the magnetic layer further comprises a compound in which a substituent selected from the group consisting of a carboxyl group and a hydroxyl group is directly substituted into a ring structure comprising a double bond and having a ClogP falling within a range of 2.3 to 5.5.

Claims

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

the ferromagnetic powder is a hexagonal ferrite powder,

squareness in a vertical direction without demagnetizing field correction of the magnetic layer ranges from 0.6 to 1.0,

the magnetic layer further comprises a compound in which a substituent selected from the group consisting of a carboxyl group and a hydroxyl group is directly substituted into a ring structure comprising a double bond and having a ClogP falling within a range of 2.3 to 5.5, and has a negative value of a magnetic interaction, Δ

M, calculated by equation (1) below;

Δ

M=(Id(H)+2Ir(H)−

Ir(∞

))/Ir(∞

) 

 

(1)

wherein in equation (1), Id(H) denotes residual magnetization measured with DC demagnetization, Ir(H) denotes residual magnetization measured with AC demagnetization, and Ir(∞

) denotes residual magnetization measured at an applied magnetic field of 796 kA/m (10 kOe).

2. The magnetic tape according to claim 1, which is a longitudinal recording magnetic tape.

3. The magnetic tape according to claim 1, wherein the magnetic layer has the Δ

M of equal to or less than −

0.05.

4. The magnetic tape according to claim 1, wherein the ring structure is selected from the group consisting of a naphthalene ring, a biphenyl ring, an anthracene ring, and a pyrene ring.

5. The magnetic tape according to claim 1, wherein the compound is selected from the group consisting of dihydroxynaphthalene, biphenylcarboxylic acid, anthraquinonecarboxylic acid, pyrenecarboxylic acid, and hydroxynaphthalene.

6. The magnetic tape according to claim 1, wherein the average plate diameter of the hexagonal ferrite powder ranges from 10 nm to 30 nm.

7. The magnetic tape according to claim 1, wherein the magnetic layer comprises the compound in a quantity of 1 to 20 mass parts per 100 mass parts of the hexagonal ferrite powder.

8. A method of manufacturing a magnetic tape, wherein the magnetic tape is the magnetic tape according to claim 1, and the method comprises:

preparing a coating liquid by dispersing a magnetic liquid containing a hexagonal ferrite powder, a binder, and a compound in which a substituent selected from the group consisting of a carboxyl group and a hydroxyl group is directly substituted into a ring structure comprising a double bond and having a ClogP falling within a range of 2.3 to 5.5,

forming a magnetic layer by coating the coating liquid that has been prepared on a nonmagnetic support, and

adjusting squareness in a vertical direction without demagnetizing field correction of the magnetic layer to within a range of 0.6 to 1.0 by implementing vertical orientation processing.

9. The method of manufacturing a magnetic tape according to claim 8, which further comprises preparing the magnetic liquid by preparing a mixture of a hexagonal ferrite powder and a binder and adding the compound to the mixture.

10. A magnetic recording device, which comprises the magnetic tape according to claim 1 and a longitudinal recording magnetic head.