Magnetic recording medium

• US 9,530,444 B2
• Filed: 03/13/2014
• Issued: 12/27/2016
• Est. Priority Date: 03/15/2013
• Status: Active Grant

• Current Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Original Assignee: Fujifilm Corporation (Fujifilm Holdings Corporation)
• Inventors: Kasada, Norihito
• Primary Examiner(s): Rickman, Holly
• Assistant Examiner(s): CHAU, LINDA N
• Application Number:
  US14/209,065
• Publication Number:
  US 20140272474A1
• Time in Patent Office: 1,020 Days
• Field of Search: None
• US Class Current: 1/1
• CPC Class Codes: G11B 5/7013 characterised by the dispersing agent
• CPC Class Codes: G11B 5/70678 Ferrites
• CPC Class Codes: G11B 5/7085 non-magnetic abrasive particles

Abstract

An aspect of the present invention relates to 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 comprising 3 to 12 weight percent of Al, based on Al₂O₃ conversion, relative to 100 weight percent of a total weight of the powder, the magnetic layer further comprises abrasive, and a maximum plan view surface area of the abrasive as determined for a 4.3 μm×6.3 μm rectangular region of the magnetic layer by a scanning electron microscope is less than 0.06 percent relative to 100 percent of a total surface area of the region.

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 comprising 3 weight percent to 12 weight percent of Al, based on Al₂O₃ conversion, relative to 100 weight percent of the total weight of the powder,

the magnetic layer further comprises abrasive and an aromatic hydrocarbon compound comprising a phenolic hydroxyl group,

the maximum plan view surface area of the abrasive as determined for a 4.3 μ

m×

6.3 μ

m rectangular region of the magnetic layer by a scanning electron microscope is less than 0.06 percent relative to 100 percent of the total surface area of the region, and

the specific surface area of the abrasive by the BET method ranges from 14 m²/g to 40 m²/g.

2. The magnetic recording medium according to claim 1, wherein the abrasive is alumina.

3. The magnetic recording medium according to claim 1, wherein the aromatic hydrocarbon compound comprising a phenolic hydroxyl group is denoted by formula (1) below:

4. The magnetic recording medium according to claim 1, wherein the aromatic hydrocarbon compound comprising a phenolic hydroxyl group is selected from the group consisting of dihydroxynaphthalene and derivatives thereof.

5. The magnetic recording medium according to claim 1, wherein Al adheres to a surface of the ferromagnetic hexagonal ferrite powder.

6. The magnetic recording medium according to claim 1, wherein the ferromagnetic hexagonal ferrite powder is ferromagnetic hexagonal ferrite powder comprising more than 8 weight percent and equal to or less than 12 weight percent of Al, based on Al₂O₃ conversion, relative to 100 weight percent of the total weight of the powder.

7. The magnetic recording medium according to claim 1, wherein the ferromagnetic hexagonal ferrite powder is ferromagnetic hexagonal ferrite powder that has been obtained by a glass crystallization method using a mixture of starting materials comprising Al.