Magnetic recording medium, magnetic recording and reproducing apparatus, magnetic tape cartridge, and magnetic tape cartridge group

Patent metadata

Field	Value
Publication number	US-11264054-B2
Application number	US-202117155695-A
Country	US
Kind code	B2
Filing date	Jan 22, 2021
Priority date	Jan 24, 2020
Publication date	Mar 1, 2022
Grant date	Mar 1, 2022

Abstract

In the magnetic recording medium, a number distribution A of a plurality of bright regions, based on equivalent circle diameters thereof, in a binarized image of a secondary electron image obtained by imaging a surface of the magnetic layer by a scanning electron microscope at an acceleration voltage of 5 kV and a number distribution B of a plurality of dark regions, based on equivalent circle diameters thereof, in a binarized image of a secondary electron image obtained by imaging a surface of the magnetic layer by a scanning electron microscope at an acceleration voltage of 2 kV respectively satisfy a predetermined number distribution.

First claim

What is claimed is:

1. A magnetic recording medium comprising:
a non-magnetic support; and
a magnetic layer including ferromagnetic powder,
wherein a number distribution A of a plurality of bright regions, based on equivalent circle diameters thereof, in a binarized image of a secondary electron image obtained by imaging a surface of the magnetic layer by a scanning electron microscope at an acceleration voltage of 5 kV satisfies the following (1) to (3):
(1) bright regions having an equivalent circle diameter of 1 nm or more and 50 nm or less are 10,000 or more and 30,000 or less;
(2) bright regions having an equivalent circle diameter of 51 nm or more and 100 nm or less are 7,000 or more and 25,000 or less; and
(3) bright regions having an equivalent circle diameter of 101 nm or more are 1,000 or more and 3,000 or less, and

a number distribution B of a plurality of dark regions, based on equivalent circle diameters thereof, in a binarized image of a secondary electron image obtained by imaging a surface of the magnetic layer by a scanning electron microscope at an acceleration voltage of 2 kV satisfies the following (4) to (6):
(4) dark regions having an equivalent circle diameter of 1 nm or more and 50 nm or less are 1,000 or more and 25,000 or less;
(5) dark regions having an equivalent circle diameter of 51 nm or more and 100 nm or less are 200 or more and 5,000 or less; and
(6) dark regions having an equivalent circle diameter of 101 nm or more are 0 or more and 200 or less.

2. The magnetic recording medium according to claim 1 ,
wherein a total thickness of the magnetic recording medium is 5.3 μm or less.

3. The magnetic recording medium according to claim 1 , further comprising:
a non-magnetic layer including non-magnetic powder between the non-magnetic support and the magnetic layer.

4. The magnetic recording medium according to claim 1 , further comprising:
a back coating layer including non-magnetic powder on a surface side of the non-magnetic support opposite to a surface side provided with the magnetic layer.

5. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes two or more types of non-magnetic powder.

6. The magnetic recording medium according to claim 5 ,
wherein the non-magnetic powder of the magnetic layer includes alumina powder.

7. The magnetic recording medium according to claim 5 ,
wherein the non-magnetic powder of the magnetic layer includes carbon black.

8. The magnetic recording medium according to claim 1 ,
wherein the ferromagnetic powder is hexagonal barium ferrite powder.

9. The magnetic recording medium according to claim 1 ,
wherein the ferromagnetic powder is hexagonal strontium ferrite powder.

10. The magnetic recording medium according to claim 1 ,
wherein the ferromagnetic powder is ε-iron oxide powder.

11. The magnetic recording medium according to claim 1 ,
wherein a vertical squareness ratio is 0.65 or more and 1.00 or less.

12. The magnetic recording medium according to claim 1 ,
wherein a vertical coercive force is 2,500 Oe or more and 3,500 Oe or less.

13. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium is a magnetic tape.

14. A magnetic recording and reproducing apparatus comprising:
the magnetic recording medium according to claim 1 .

15. The magnetic recording and reproducing apparatus according to claim 14 , further comprising:
a magnetic head that has an inductive recording element having a first magnetic pole that generates a magnetic field and a second magnetic pole that is separated from the first magnetic pole with a write gap therebetween,
wherein the first magnetic pole has a layer made of an alloy containing Co and Fe as an outermost layer of a portion facing the second magnetic pole with the write gap therebetween, and
the second magnetic pole has a layer made of an alloy containing Co and Fe as an outermost layer of a portion facing the first magnetic pole with the write gap therebetween.

16. The magnetic recording and reproducing apparatus according to claim 14 , further comprising:
a magnetic head having an inductive recording element having a length of a write gap of 120 nm or less.

17. A magnetic tape cartridge comprising:
the magnetic recording medium according to claim 13 .

18. A magnetic tape cartridge group comprising:
a plurality of the magnetic tape cartridges according to claim 17 .

19. The magnetic tape cartridge group according to claim 18 ,
wherein, in an environment of an atmosphere temperature of 21° C. and a relative humidity of 50%, a slope α of a signal-to-noise-ratio with respect to the number of rolls, the slope α being obtained by performing a reproduction test of a total of 200 rolls of the magnetic tape cartridges using a single magnetic head, is 0.5 dB/decade or less.

Assignees

• Fujifilm Corp

Inventors

• Kasada Norihito
• Matsuyama So
• Musha Atsushi
• Kamimura Shota

Classifications

• G11B5/7085 Primary

  non-magnetic abrasive particles · CPC title

• G11B5/733 Primary

  characterised by the addition of non-magnetic particles {(base layers having a non-magnetic layer under a soft magnetic layer G11B5/736; magnetic recording media substrates G11B5/739)} · CPC title

• G11B5/7356

  comprising non-magnetic particles in the back layer, e.g. particles of TiO2, ZnO or SiO2 · CPC title

• G11B5/1875

  "Composite" pole pieces, i.e. poles composed in some parts of magnetic particles and in some other parts of magnetic metal layers · CPC title

• G11B5/714

  characterised by the dimension of the magnetic particles · CPC title