Magnetic recording medium having controlled dimensional characteristics

Patent metadata

Field	Value
Publication number	US-11508407-B2
Application number	US-201816474437-A
Country	US
Kind code	B2
Filing date	Nov 26, 2018
Priority date	Mar 30, 2018
Publication date	Nov 22, 2022
Grant date	Nov 22, 2022

Abstract

A magnetic recording medium is a magnetic recording medium having a tape-like shape and includes a base substrate and a magnetic layer provided on the base substrate. A plurality of data tracks can be formed in the magnetic layer, a width of a data track is 2900 nm or less, and in a case of defining, as wmax and wmin, a maximum value and a minimum value respectively out of average values of a width of the magnetic recording medium measured under four kinds of environment in which temperature and relative humidity are set to (10° C., 10%), (10° C., 80%), (29° C., 80%), and (45° C., 10%), wmax and wmin satisfy a relation of (wmax−wmin)/wmin≤400 [ppm].

First claim

The invention claimed is:

1. A magnetic recording medium having a tape-like shape, comprising:
a base substrate; and
a magnetic layer provided on the base substrate,
wherein a plurality of data tracks can be formed in the magnetic layer,
a width of the data track is 2900 nm or less, and
in a case of defining, as w max and w min , a maximum value and a minimum value respectively out of average values of a width of the magnetic recording medium measured under four kinds of environment in which temperature and relative humidity are set to (10° C., 10%), (10° C., 80%), (29° C., 80%), and (45° C., 10%), w max and w min satisfy Relational Expression (1) below:
( w max −w min )/ w min ≤400 [ppm]  (1).

2. The magnetic recording medium according to claim 1 , wherein a squareness ratio in a vertical direction is 65% or more.

3. The magnetic recording medium according to claim 1 , wherein a squareness ratio in a longitudinal direction is 35% or less.

4. The magnetic recording medium according to claim 1 , wherein the magnetic layer can record data in a manner such that a ratio W/L between a minimum value L of a magnetization inversion interval and a width W of the data track satisfies a relation of W/L≤60.

5. The magnetic recording medium according to claim 1 , wherein the magnetic layer can record data in a manner such that a ratio W/L between a minimum value L of a magnetization inversion interval and a width W of the data track satisfies a relation of W/L≤30.

6. The magnetic recording medium according to claim 1 , wherein the magnetic layer can record data in a manner such that a minimum value of the magnetization inversion interval L is 48 nm or less.

7. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes a plurality of servo bands, and
a proportion of total area of the servo bands to area of a surface of the magnetic layer is 4.0% or less.

8. The magnetic recording medium according to claim 7 , wherein number of servo bands is five or more.

9. The magnetic recording medium according to claim 7 , wherein the number of servo bands is 5+4n (where n is a positive integer) or more.

10. The magnetic recording medium according to claim 7 , wherein a width of the servo band is 95 μm or less.

11. The magnetic recording medium according to claim 1 , wherein an average thickness of the magnetic recording medium is 5.6 μm or less.

12. The magnetic recording medium according to claim 1 , wherein an average thickness of the base substrate is 4.2 μm or less.

13. The magnetic recording medium according to claim 1 , wherein an average thickness of the magnetic layer is 90 nm or less.

14. The magnetic recording medium according to claim 1 , wherein a dimensional change amount Δw in a width direction with respect to a tension change in the longitudinal direction satisfies 700 [ppm/N]≤Δw, and
wherein Δw is determined according to:

Δ
⁢

w
[

ppm
/
N

]

=

D
⁡
(

0.2

N

)

[
mm
]

-

D
⁡
(

1.

N

)

[
mm
]

D
⁡
(

2.

N

)

[
mm
]

×

1
,
000
,
000

(

1
.

0
[
N
]

)

-

(

0.2
[
N
]

)

where D(0.2N) and D(1.0N) represent widths of a sample of the magnetic recording medium subject to loads of 0.2N and 1.0N, respectively, in the longitudinal direction.

15. The magnetic recording medium according to claim 1 , wherein a thermal expansion coefficient α satisfies 6 [ppm/° C.]≤α≤8 [ppm/° C.], and a humidity expansion coefficient β satisfies β≤5 [ppm/% RH].

16. The magnetic recording medium according to claim 1 , wherein a Poisson's ratio ρ satisfies 0.3≤ρ.

17. The magnetic recording medium according to claim 1 , wherein an elastic limit value σ MD in the longitudinal direction satisfies 0.8 [N]≤σ MD , and wherein σ MD is determined by pulling a sample of the magnetic recording medium at 0.5 mm/min to obtain a distance versus load relationship.

18. The magnetic recording medium according to claim 1 ,
wherein the magnetic layer includes magnetic powder, and
the magnetic powder includes hexagonal ferrite, ε-iron oxide, or Co-containing spinel ferrite.

19. The magnetic recording medium according to claim 18 , wherein an average aspect ratio of the magnetic powder is 1.0 or more and 3.0 or less.

20. The magnetic recording medium according to claim 18 ,
wherein the hexagonal ferrite includes at least one kind out of Ba or Sr, and
the ε-iron oxide includes at least one kind out of Al or Ga.

21. The magnetic recording medium according to claim 1 , wherein a Young modulus ratio (E TD /E MD ) between a Young modulus E TD in the width direction and a Young modulus E MD in the longitudinal direction is 1.5 or more and 2.0 or less.

22. The magnetic recording medium according to claim 1 ,
wherein the magnetic powder includes hexagonal ferrite, and
an average particle volume of the magnetic powder is 1000 nm 3 or more and 1800 nm 3 or less.

23. A magnetic recording medium having a tape-like shape, comprising:
a base substrate; and
a magnet

Assignees

• Sony Corp

Inventors

• Sekiguchi Noboru
• Yamaga Minoru

Classifications

• G11B5/70678 Primary

  Ferrites · CPC title

• G11B5/78

  Tape carriers · CPC title

• G11B5/733

  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

• G11B5/73

  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

• G11B5/5928

  Longitudinal tracks · CPC title