MAGNETIC RECORDING MEDIUM

• US 20180182422A1
• Filed: 12/27/2017
• Published: 06/28/2018
• Est. Priority Date: 12/28/2016
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Maxell Holdings, Ltd.
• Inventors: KAWAKAMI, Shinji, HIROI, Toshio, FUJITA, Masao
• Granted Patent: US 10,614,847 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70615 containing Fe metal or alloys G11B5/70621 takes precedence
• CPC Class Codes: G11B 5/70642 iron oxides
• CPC Class Codes: G11B 5/714 characterised by the dimension of the magnetic particles

Abstract

In a magnetic recording medium according to the present invention, if a straight line W having a length of 500 nm and a width of 15 nm is displayed parallel to a width direction of the magnetic layer and a straight line L having a length of 500 nm and a width of 15 nm is displayed parallel to a longitudinal direction of the magnetic layer, the number of magnetic particles that intersect the straight line W is N1, and the number of magnetic particles that intersect the straight line L is N2, then, a relationship of N1/0.5>60 and N2/0.5>60 is established where N1/0.5 is the number of magnetic particles per micrometer obtained by dividing N1 by 0.5 μm and N2/0.5 is the number of magnetic particles per micrometer obtained by dividing N2 by 0.5 μm.

Claims

1. A magnetic recording medium comprising:

a nonmagnetic support body; and

a magnetic layer containing magnetic particles,

wherein 0.0013 μ

T·

m<

Mr·

t<

0.0032 μ

T·

m is satisfied where Mr is a residual magnetic flux density in a thickness direction of the magnetic layer and t is an average thickness of the magnetic layer,

a squareness ratio in the thickness direction of the magnetic layer is 0.65 or more,

if a straight line W having a length of 500 nm and a width of 15 nm is displayed parallel to a width direction of the magnetic layer and a straight line L having a length of 500 nm and a width of 15 nm is displayed parallel to a longitudinal direction of the magnetic layer, on an image obtained by observing a surface of the magnetic layer using a scanning electron microscope at 10 k-fold magnification,

the straight line W does not intersect a particle having a particle diameter of 50 nm or more and a gap having a maximum width of 50 nm or more on the image, and on the image, the number of magnetic particles that intersect the straight line W is N1, and

the straight line L does not intersect a particle having a particle diameter of 50 nm or more and a gap having a maximum width of 50 nm or more on the image, and on the image, the number of magnetic particles that intersect the straight line L is N2,

then, a relationship of N1/0.5>

60 and N2/0.5>

60 is established where N1/0.5 is the number of magnetic particles per micrometer obtained by dividing N1 by 0.5 μ

m and N2/0.5 is the number of magnetic particles per micrometer obtained by dividing N2 by 0.5 μ

m.

2. The magnetic recording medium according to claim 1,

wherein if a length of magnetization in the width direction of the magnetic layer is set to 1 μ

m or less, the length being a length of magnetization of a signal recorded in the magnetic layer, reproduction is performed by a TMR head.

3. The magnetic recording medium according to claim 1,

wherein the magnetic particles are made of ε

-iron oxide.

4. The magnetic recording medium according to claim 3,

wherein an average particle diameter of the magnetic particles made of the ε

-iron oxide is 15 nm or less.

5. The magnetic recording medium according to claim 1,

wherein a magnetic coercive force in the thickness direction of the magnetic layer is 3000 oersteds [Oe] or more.

6. The magnetic recording medium according to claim 1,

wherein when spacing on a surface of the magnetic layer is measured using a TSA (tape spacing analyzer) after the surface of the magnetic layer is cleaned using n-hexane, a value of the spacing is 5 nm or more and 12 nm or less.

7. The magnetic recording medium according to claim 1,

wherein a thickness of the magnetic layer is 30 nm or more and 200 nm or less.