Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-2025336418-A1
Application number	US-202218574562-A
Country	US
Kind code	A1
Filing date	Feb 22, 2022
Priority date	Jul 21, 2021
Publication date	Oct 30, 2025
Grant date	—

Abstract

A main object is to provide a magnetic recording medium having a high recording density to be capable of preventing an increase in frictional force even in a case where many times of traveling is performed. Furthermore, in addition to the prevention of an increase in frictional force, a further object of the present technology is maintenance of the polishing force at the time of many times of traveling.
The present technology provides a magnetic recording medium including a magnetic layer containing a magnetic powder, the magnetic layer containing first particles having conductivity and second particles having a Mohs hardness of 7 or more, the first particles and the second particles forming protrusions on a surface on a side of the magnetic layer, the second particles forming protrusions having an average height (H 2 ) of 7 nm or less on the surface on the side of the magnetic layer, the magnetic recording medium containing a fatty acid, the magnetic recording medium having an extraction rate of the fatty acid of 45% or more, the extraction rate defined by a formula described below.
Extraction rate of fatty acid (%)=[amount of fatty acid extracted in 5 minutes (mg/m 2 )/total amount of fatty acid extracted (mg/m 2 )]×100

First claim

1 . A magnetic recording medium comprising a magnetic layer containing a magnetic powder,
the magnetic layer containing first particles having conductivity and second particles having a Mohs hardness of 7 or more, the first particles and the second particles forming protrusions on a surface on a side of the magnetic layer, the second particles forming protrusions having an average height (H 2 ) of 7 nm or less on the surface on the side of the magnetic layer, the magnetic recording medium containing a fatty acid, the magnetic recording medium having an extraction rate of the fatty acid of 45% or more, the extraction rate defined by a formula described below:

extraction
⁢

rate
⁢

of
⁢

fatty
⁢

acid
⁢

(
%
)

=

[

amount
⁢

of
⁢

fatty
⁢

acid
⁢

extracted
⁢

in
⁢

5
⁢

minutes
⁢

(

mg

/m
2

)

/

total
⁢

amount
⁢

of
⁢

fatty
⁢

acid
⁢

extracted
⁢

(

mg

/m
2

)

]

×
100.

2 . The magnetic recording medium according to claim 1 , wherein an amount of the fatty acid extracted in 5 minutes (mg/m 2 ) is 3.0 mg/m 2 or more.

3 . The magnetic recording medium according to claim 1 , wherein a total amount of the fatty acid extracted (mg/m 2 ) is 5.0 mg/m 2 or more.

4 . The magnetic recording medium according to claim 1 , wherein the fatty acid includes stearic acid.

5 . The magnetic recording medium according to claim 1 , further containing a fatty acid ester, and having an extraction rate of the fatty acid ester of 60% or more, the extraction rate defined by a formula described below:

extraction
⁢

rate
⁢

of
⁢

fatty
⁢

acid
⁢

ester
⁢

(
%
)

=

[

amount
⁢

of
⁢

fatty
⁢

acid
⁢

ester
⁢

extracted
⁢

in
⁢

5
⁢

minutes
⁢

(

mg

/m
2

)

/

total
⁢

amount
⁢

of
⁢

fatty
⁢

acid
⁢

ester
⁢

extracted
⁢

(

mg

/m
2

)

]

×
100.

6 . The magnetic recording medium according to claim 5 , wherein an amount of the fatty acid ester extracted in 5 minutes (mg/m 2 ) is 10.0 mg/m 2 or more.

7 . The magnetic recording medium according to claim 5 , wherein a total amount of the fatty acid ester extracted (mg/m 2 ) is 12.0 mg/m 2 or more.

8 . The magnetic recording medium according to claim 5 , wherein the fatty acid ester includes butyl stearate.

9 . The magnetic recording medium according to claim 1 , wherein the magnetic layer has an average thickness of 0.08 μm or less.

10 . The magnetic recording medium according to claim 1 , further comprising a non-magnetic layer.

11 . The magnetic recording medium according to claim 10 , wherein the non-magnetic layer has an average thickness of 1.2 μm or less.

12 . The magnetic recording medium according to claim 1 , having an average thickness (average total thickness) of 5.7 μm or less.

13 . The magnetic recording medium according to claim 1 , wherein the magnetic powder has a surface covered with a covering agent.

14 . The magnetic recording medium according to claim 13 , wherein the covering agent includes an organic acid.

15 . The magnetic recordin

Assignees

• Sony Group Corp

Inventors

• Enomoto Taikei
• Yamaga Minoru
• Sasaki Futoshi

Classifications

• G11B5/725 Primary

  containing a lubricant {, e.g. organic compounds (inorganic carbon protective coating G11B5/727)} · CPC title

• G11B5/41

  Cleaning of heads {(of record carriers G11B23/50)} · CPC title

• G11B5/71

  characterised by the lubricant · CPC title

• G11B5/78 Primary

  Tape carriers · CPC title

• G11B5/73

  Base layers {, i.e. all non-magnetic layers lying under a lowermost magnetic recording layer, e.g. including any non-magnetic layer in between a first magnetic recording layer and either an underlying substrate or a soft magnetic underlayer} · CPC title