MAGNETIC RECORDING MEDIUM

• US 20170221513A1
• Filed: 01/31/2017
• Published: 08/03/2017
• Est. Priority Date: 02/01/2016
• Status: Active Grant

• Current Assignee: Maxell, Ltd.
• Original Assignee: Hitachi Maxell Limited (Hitachi, Ltd.)
• Inventors: HIROI, Toshio, KAWAKAMI, Shinji, TANAKA, Kenji
• Granted Patent: US 10,255,938 B2
• Time in Patent Office: Days
• CPC Class Codes: G11B 5/00813 magnetic tapes
• CPC Class Codes: G11B 5/70 on a base layer
• CPC Class Codes: G11B 5/70642 iron oxides
• CPC Class Codes: G11B 5/725 containing a lubricant , e.g. organic compounds inorganic carbon protective coating G11B5/727
• CPC Class Codes: G11B 5/78 Tape carriers

Abstract

A magnetic recording medium of the present invention includes a non-magnetic substrate, and a magnetic layer containing a magnetic powder. The magnetic powder is constituted by an ε-iron oxide powder. The magnetic layer has a squareness in a thickness direction of 0.65 or more. In a differential curve obtained by differentiating a hysteresis curve in the thickness direction of the magnetic layer, two or more peaks are present. In a case where, out of peaks in the same direction among the above-described peaks, a local maximum of a largest peak in a magnetic field range of +500 oersted [Oe] or more is taken as P1 and a local maximum of a largest peak in a magnetic field range of −500 oersted [Oe] or more and less than +500 oersted [Oe] is taken as P2, a relationship below is satisfied:

0.25≦P2/P1≦0.60.

Claims

1. A magnetic recording medium, comprising a non-magnetic substrate, and a magnetic layer containing a magnetic powder,

wherein the magnetic powder is constituted by an ε

-iron oxide powder,

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

in a hysteresis curve in the thickness direction of the magnetic layer, in a case where a point at which, after saturation magnetization in a positive direction is reached by applying a magnetic field in the positive direction to the magnetic layer, saturation magnetization in a direction (negative direction) opposite to the positive direction is reached by applying a magnetic field in the opposite direction (negative direction) is taken as a point A, and a point at which saturation magnetization in the positive direction is reached by applying a magnetic field in the positive direction further from the point A is taken as a point B, two or more peaks are present in a differential curve obtained by differentiating the hysteresis curve from the point A to the point B, and

in a case where, out of the peaks, a local maximum of a largest peak in a magnetic field range of +500 oersted [Oe] or more is taken as P1 and a local maximum of a largest peak in a magnetic field range of −

500 oersted [Oe] or more and less than +500 oersted [Oe] is taken as P2, a relationship below is satisfied;

0.25≦

P2/P1≦

0.60.

2. The magnetic recording medium according to claim 1, wherein the magnetic powder has an average particle size of 8 nm or more and 20 nm or less.

3. The magnetic recording medium according to claim 1, wherein spacing of a surface of the magnetic layer measured using a TSA (tape spacing analyzer) after the surface of the magnetic layer has been washed with n-hexane is 5 nm or more and 15 nm or less.

4. The magnetic recording medium according to claim 1, further comprising a lubricant layer containing a fluorine-based lubricant or a silicone-based lubricant, on a surface of the magnetic layer.

5. The magnetic recording medium according to claim 1, wherein the magnetic layer has a thickness of 30 nm or more and 200 nm or less.