Magnetic recording medium, magnetic signal reproduction device and method of manufacturing magnetic recording medium

Patent metadata

Field	Value
Publication number	US-10957352-B2
Application number	US-201916259319-A
Country	US
Kind code	B2
Filing date	Jan 28, 2019
Priority date	Sep 30, 2015
Publication date	Mar 23, 2021
Grant date	Mar 23, 2021

Abstract

The magnetic recording medium has a magnetic layer containing multiple nonmagnetic particles having a ratio, major axis length/minor axis length, of less than or equal to 1.5, the multiple nonmagnetic particles are present in the magnetic layer in a state where, when the depth to which each of the multiple nonmagnetic particles is embedded in the magnetic layer in observation of a sectional image picked up by SEM is denoted as b and the thickness of the magnetic layer as t, the average value of the ratio of b/t is less than or equal to 0.9, and the number of protrusions 5 nm or greater in height is 800 or greater and the number of protrusions 20 nm or greater in height is 20 or less as measured by AFM per an area 40 μm×40 μm on the magnetic layer side surface of the magnetic recording medium.

First claim

What is claimed is:

1. A magnetic signal reproduction device,
which comprises a magnetic recording medium and a magnetic reproduction head, and which reproduces with the magnetic reproduction head a magnetic signal that has been recorded at a linear recording density of greater than or equal to 200 kfci on the magnetic recording medium;
wherein the magnetic recording medium comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support;
wherein the magnetic layer comprises multiple nonmagnetic particles having a ratio of a major axis length to a minor axis length, major axis length/minor axis length, of less than or equal to 1.5;
the multiple nonmagnetic particles are present in the magnetic layer in a state where, when a depth to which each of the multiple nonmagnetic particles is embedded in the magnetic layer in observation of a sectional image picked up by a scanning electron microscope is denoted as b and a thickness of the magnetic layer is denoted as t, an average value of a ratio of b/t is less than or equal to 0.9; and
a number of protrusions greater than or equal to 5 nm in height is greater than or equal to 800 and a number of protrusions greater than or equal to 20 nm in height is less than or equal to 20 as measured by an atomic force microscope per an area 40 μm×40 μm on a magnetic layer side surface of the magnetic recording medium,
wherein a ratio φ/t of an average major axis length φ of the multiple nonmagnetic particles having a ratio of a major axis length to a minor axis length, major axis length/minor axis length, of less than or equal to 1.5 that are contained in the magnetic layer to the thickness of the magnetic layer is less than or equal to 1.0.

2. The magnetic signal reproduction device according to claim 1 ,
wherein the average major axis length φ of the multiple nonmagnetic particles having a ratio of a major axis length to a minor axis length, major axis length/minor axis length, of less than or equal to 1.5 that are contained in the magnetic layer ranges from 10 nm to 100 nm.

3. The magnetic signal reproduction device according to claim 1 ,
wherein the thickness of the magnetic layer t is less than or equal to 100 nm.

4. The magnetic signal reproduction device according to claim 1 ,
wherein the multiple nonmagnetic particles having a ratio of a major axis length to a minor axis length, major axis length/minor axis length, of less than or equal to 1.5 that are contained in the magnetic layer are inorganic oxide particles.

5. The magnetic signal reproduction device according to claim 4 ,
wherein the inorganic oxide particles are silicon oxide particles.

6. The magnetic signal reproduction device according to claim 5 ,
wherein the silicon oxide particles are silica colloidal particles.

7. The magnetic signal reproduction device according to claim 1 ,
wherein the number of protrusions greater than or equal to 5 nm in height as measured by an atomic force microscope per an area of 40 μm×40 μm on the magnetic layer side surface of the magnetic recording medium is greater than or equal to 800 but less than or equal to 500,000.

8. The magnetic signal reproduction device according to claim 1 ,
wherein the number of protrusions greater than or equal to 5 nm in height as measured by an atomic force microscope per an area of 40 μm×40 μm on the magnetic layer side surface of the magnetic recording medium is greater than or equal to 4,000.

9. The magnetic signal reproduction device according to claim 1 ,
wherein the number of protrusions greater than or equal to 20 nm in height as measured by an atomic force microscope per an area of 40 μm×40 μm on the magnetic layer side surface of the magnetic recording medium is less than or equal to 10.

10. The magnetic signal reproduction device according to claim 1 ,
which comprises a nonmagnetic layer comprising nonmagnetic powder and binder between the nonmagnetic support and the magnetic layer.

Assignees

• Fujifilm Corp

Inventors

• Mori Masahiko

Classifications

• G11B5/735

  characterised by the back layer {(magnetic recording media substrates G11B5/739)} · CPC title

• G11B5/7085

  non-magnetic abrasive particles · CPC title

• G11B5/70

  on a base layer · CPC title

• G11B5/68

  comprising one or more layers of magnetisable material homogeneously mixed with a bonding agent · CPC title

• G11B5/708 Primary

  characterised by addition of non-magnetic particles to the layer · CPC title