Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-9530444-B2
Application number	US-201414209065-A
Country	US
Kind code	B2
Filing date	Mar 13, 2014
Priority date	Mar 15, 2013
Publication date	Dec 27, 2016
Grant date	Dec 27, 2016

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 Al 2 O 3 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.

First claim

What is claimed is:

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 Al 2 O 3 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 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 the total surface area of the region, and
the specific surface area of the abrasive by the BET method ranges from 14 m 2 /g to 40 m 2 /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:

wherein, in formula (1), two from among X 1 to X 8 denote hydroxyl groups and each of the others from among X 1 to X 8 independently denotes a hydrogen atom or a substituent.

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 Al 2 O 3 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.

Assignees

• Fujifilm Corp

Inventors

• Kasada Norihito

Classifications

• G11B5/70678

  Ferrites · CPC title

• G11B5/7085 Primary

  non-magnetic abrasive particles · CPC title

• G11B5/7013 Primary

  characterised by the dispersing agent · CPC title