Magnetic recording medium, manufacturing method of e-type iron oxide particles, and manufacturing method of magnetic recording medium

Patent metadata

Field	Value
Publication number	US-2020279582-A1
Application number	US-202016802017-A
Country	US
Kind code	A1
Filing date	Feb 26, 2020
Priority date	Feb 28, 2019
Publication date	Sep 3, 2020
Grant date	—

Abstract

An object of the present invention is to provide a magnetic recording medium, which contains ε-type iron oxide particles and has excellent SNR, a manufacturing method of ε-type iron oxide particles, and a manufacturing method of a magnetic recording medium.
The object is achieved by a magnetic recording medium containing ε-type iron oxide particles, in which a coefficient of variation of an aspect ratio of the ε-type iron oxide particles is equal to or smaller than 18%, and a squareness ratio of the magnetic recording medium measured in a longitudinal direction of the magnetic recording medium is higher than 0.3 and equal to or lower than 0.5. The object is also achieved by the application of the magnetic recording medium.

First claim

What is claimed is:

1 . A magnetic recording medium comprising:
ε-type iron oxide particles, wherein a coefficient of variation of an aspect ratio of the ε-type iron oxide particles is equal to or smaller than 18%, and a squareness ratio of the magnetic recording medium measured in a longitudinal direction of the magnetic recording medium is higher than 0.3 and equal to or lower than 0.5.

2 . The magnetic recording medium according to claim 1 ,
wherein the aspect ratio of the ε-type iron oxide particles is within a range of 1.00 to 1.35.

3 . The magnetic recording medium according to claim 1 ,
wherein an average equivalent circular diameter of the ε-type iron oxide particles is within a range of 8.0 nm to 15.0 nm.

4 . The magnetic recording medium according to claim 2 ,
wherein an average equivalent circular diameter of the ε-type iron oxide particles is within a range of 8.0 nm to 15.0 nm.

5 . A manufacturing method of ε-type iron oxide particles, comprising:
a step A of mixing together water, a compound containing trivalent iron ions, and at least one kind of metal compound containing metallic element other than iron so as to prepare a mixed solution containing iron ions;
a step B of adding an alkali agent to the mixed solution obtained by the step A while stirring the mixed solution and stirring the mixed solution while keeping the mixed solution at a temperature equal to or higher than 0° C. and equal to or lower than 25° C.;
a step C of heating the mixed solution obtained by the step B and stirring the mixed solution while keeping the mixed solution at a liquid temperature higher than 30° C. and equal to or lower than 90° C.; and
a step D of extracting powder from the mixed solution obtained by the step C and performing a heat treatment on the obtained powder so as to obtain heat-treated powder,
wherein a coefficient of variation of an aspect ratio of the ε-type iron oxide particles is equal to or smaller than 18%.

6 . The manufacturing method of ε-type iron oxide particles according to claim 5 ,
wherein a temperature of the heat treatment in the step D is within a range equal to or higher than 800° C. and equal to or lower than 1,400° C.

7 . A manufacturing method of a magnetic recording medium, comprising:
a step E of preparing a composition for forming a magnetic layer containing the ε-type iron oxide particles obtained by the manufacturing method according to claim 5 and organic solvents; a step F of applying the composition for forming a magnetic layer to a non-magnetic support so as to form a layer of the composition for forming a magnetic layer; a step G of performing a magnetic field alignment treatment on the formed layer of the composition for forming a magnetic layer; and a step H of drying the layer of the composition for forming a magnetic layer having undergone the magnetic field alignment treatment so as to form a magnetic layer, wherein a content rate of an organic solvent having a boiling point equal to or higher than 150° C. in all the organic solvents used for preparing the composition for forming a magnetic layer by the step E is 5% by mass to 40% by mass.

8 . The manufacturing method of a magnetic recording medium according to claim 7 ,
wherein in the manufacturing method according to claim 5 , a temperature of the heat treatment in the step D is within a range equal to or higher than 800° C. and equal to or lower than 1,400° C.

Assignees

• Fujifilm Corp

Inventors

• Fujimoto Takashi

Classifications

• G11B5/70642 Primary

  iron oxides · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title

• C01P2006/42

  Magnetic properties · CPC title

• C01P2004/64

  Nanometer sized, i.e. from 1-100 nanometer · CPC title

• C01G51/40

  Complex oxides containing cobalt and at least one other metal element · CPC title