Magnetic recording medium having a dimensional variation

Patent metadata

Field	Value
Publication number	US-10839846-B2
Application number	US-201916455132-A
Country	US
Kind code	B2
Filing date	Jun 27, 2019
Priority date	Mar 29, 2019
Publication date	Nov 17, 2020
Grant date	Nov 17, 2020

Abstract

In a magnetic recording medium, an average thickness tT is tT≤5.5 μm, a dimensional variation Δw in a width direction to tension change in a longitudinal direction is 650 ppm/N≤Δw, and a rate of shrinkage in the longitudinal direction is 0.08% or less.

First claim

The invention claimed is:

1. A magnetic recording medium comprising:
an average thickness t T is t T ≤5.5 μm,
a dimensional variation Δw in a width direction to tension change in a longitudinal direction is 650 ppm/N≤Δw,
a rate of shrinkage in the longitudinal direction is 0.08% or less, and
wherein the dimensional variation Δw is determined according to:

Δ
⁢

⁢

w
⁡

[

ppm
⁢

/

⁢
N

]

=

D
⁡

(

0.2
⁢
N

)

⁡

[
mm
]

-

D
⁡

(

1.0
⁢
N

)

⁡

[
mm
]

D
⁡

(

0.2
⁢
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.

2. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 700 ppm/N≤Δw.

3. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 750 ppm/N≤Δw.

4. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 800 ppm/N≤Δw.

5. The magnetic recording medium according to claim 1 , wherein the rate of shrinkage in the longitudinal direction is 0.07% or less.

6. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium comprises a back layer, and
a surface roughness R ab of the back layer is 3.0 nm≤R ab ≤7.5 nm.

7. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium comprises a magnetic layer and a back layer, and
a coefficient of friction μ between a surface on a side of the magnetic layer and a surface on a side of the back layer is 0.20≤μ≤0.80.

8. The magnetic recording medium according to claim 1 , wherein a 1% elongation load in the longitudinal direction is 0.60N or less, and wherein the 1% elongation load is determined by pulling a sample of the magnetic recording medium at 10 mm/min under a 0.5% elongation load and a 1.5% elongation load.

9. The magnetic recording medium according to claim 1 ,
wherein a thermal expansion coefficient α is 5.5 ppm/° C.≤α≤9 ppm/° C., and
a humidity expansion coefficient β is β≤5.5 ppm/% RH.

10. The magnetic recording medium according to claim 1 , wherein a Poisson's ratio ρ is 0.25≤ρ.

11. The magnetic recording medium according to claim 1 , wherein an elastic limit value σ MD in the longitudinal direction is 0.7 N≤σ MD , and wherein the elastic limit value 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.

12. The magnetic recording medium according to claim 11 , wherein the elastic limit value amp does not depend on a velocity V in measurement of elastic limit.

13. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium comprises a magnetic layer, and
the magnetic layer is vertically oriented.

14. The magnetic recording medium according to claim 1 , wherein the magnetic recording medium comprises a back layer, and an average thickness t b of the back layer is t b ≤0.6 μm.

15. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium comprises a magnetic layer, and
the magnetic layer is a sputtering layer.

16. The magnetic recording medium according to claim 15 , wherein an average thickness t m of the magnetic layer is 9 nm≤t m ≤90 nm.

17. The magnetic recording medium according to claim 1 ,
wherein the magnetic recording medium comprises a magnetic layer, and
the magnetic layer includes a magnetic powder.

18. The magnetic recording medium according to claim 17 , wherein the average thickness t m of the magnetic layer is 35 nm≤t m ≤120 nm.

19. The magnetic recording medium according to claim 17 , wherein the magnetic powder includes an ε-iron oxide magnetic powder, a barium ferrite magnetic powder, a cobalt ferrite magnetic powder, or a strontium ferrite magnetic powder.

20. The magnetic recording me

Assignees

• Sony Corp

Inventors

• Yamaga Minoru
• Sekiguchi Noboru

Classifications

• G11B5/735

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

• G11B5/70642

  iron oxides · CPC title

• G11B5/62 Primary

  Record carriers characterised by the selection of the material · CPC title

• G11B5/7023

  containing polyesters, polyethers, silicones, polyvinyl resins, polyacrylresins or epoxy resins (G11B5/7022 takes precedence) · CPC title

• G11B5/70678

  Ferrites · CPC title