Magnetic recording medium

Patent metadata

Field	Value
Publication number	US-11056143-B2
Application number	US-201916703435-A
Country	US
Kind code	B2
Filing date	Dec 4, 2019
Priority date	Apr 26, 2019
Publication date	Jul 6, 2021
Grant date	Jul 6, 2021

Abstract

A magnetic recording medium is provided and includes a magnetic layer, a non-magnetic layer, a base layer and a back layer, wherein an average thickness t T of the magnetic recording medium is t T ≤5.3 μm, a dimensional change amount Δw in a width direction with respect to a change in tension in a longitudinal direction is 700 ppm/N≤Δw, a thickness of the non-magnetic layer is 2.0 μm or less, a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more, and the magnetic layer includes a magnetic powder.

First claim

The invention claimed is:

1. A magnetic recording medium comprising:
a magnetic layer,
a non-magnetic layer,
a base layer, and
a back layer,
wherein
an average thickness t T of the magnetic recording medium is t T ≤5.3 μm,
a dimensional change amount Δw in a width direction with respect to a change in tension in a longitudinal direction is 700 ppm/N≤Δw,
a thickness of the non-magnetic layer is 2.0 μm or less,
a squareness ratio measured in a vertical direction of the magnetic recording medium is 65% or more,
a width deformation coefficient b during long-term storage in a case where a long-term storage width change amount Y is defined as Y=blog(t) is −0.06≤b≤0.06, and
the magnetic layer includes a magnetic powder,
wherein the width coefficient b is evaluated at 32° C. and relative humidity 55%.

2. The magnetic recording medium according to claim 1 , wherein the dimensional change amount Δw is 710 ppm/N≤Δw.

3. The magnetic recording medium according to claim 1 , wherein the dimensional change amount Δw is 730 ppm/N≤Δw.

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

5. The magnetic recording medium according to claim 1 , wherein a thermal expansion coefficient α of the magnetic recording medium is 5.5 ppm/° C.≤α≤9 ppm/° C.

6. The magnetic recording medium according to claim 1 , wherein a thermal expansion coefficient α of the magnetic recording medium is 5.9 ppm/° C.≤α≤9 ppm/° C.

7. The magnetic recording medium according to claim 1 , wherein a humidity expansion coefficient β of the magnetic recording medium is β≤5.5 ppm/% RH.

8. The magnetic recording medium according to claim 1 , wherein a humidity expansion coefficient β of the magnetic recording medium is β≤5.2 ppm/% RH.

9. The magnetic recording medium according to claim 1 , wherein a humidity expansion coefficient β of the magnetic recording medium is β≤5.0 ppm/% RH.

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

11. The magnetic recording medium according to claim 1 , wherein a Poisson's ratio ρ of the magnetic recording medium is 0.29≤ρ.

12. The magnetic recording medium according to claim 1 , wherein a Poisson's ratio ρ of the magnetic recording medium is 0.3≤ρ.

13. The magnetic recording medium according to claim 1 , wherein an elastic limit value amp of the magnetic recording medium 0.7 N≤σ MD .

14. The magnetic recording medium according to claim 1 , wherein an elastic limit value amp of the magnetic recording medium 0.75 N≤σ MD .

15. The magnetic recording medium according to claim 1 , wherein an elastic limit value amp of the magnetic recording medium 0.8 N≤σ MD .

16. The magnetic recording medium according to claim 1 , wherein the average thickness t T of the magnetic recording medium is t T ≤5.2 μm.

17. The magnetic recording medium according to claim 1 , wherein the average thickness t T of the magnetic recording medium is t T ≤5.0 μm.

18. The magnetic recording medium according to claim 1 , wherein the average thickness t T of the magnetic recording medium is t T ≤4.6 μm.

19. The magnetic recording medium according to claim 1 , wherein the thickness of the non-magnetic layer is 1.4 μm or less.

20. The magnetic recording medium according to claim 1 , wherein the thickness of the non-magnetic layer is 0.6 μm or more.

21. The magnetic recording medium according to claim 1 , wherein the thickness of the non-magnetic layer is 0.8 μm or more.

22. The magnetic recording medium according to claim 1 , wherein the magnetic powder includes c iron oxide magnetic powder, barium ferrite magnetic powder, cobalt ferrite magnetic powder, or strontium ferrite magnetic powder.

23. The magnetic recording medium according to claim 1 , wherein
the dimensional change amount Δw is determined by substituting D(0.2 N) and D(1.0 N) for a following equation wherein D(0.2 N) and D(1.0 N) represent widths of a ½ inch-wide magnetic recording medium which is cut into a length of 250 mm when 0.2 N and 1.0 N are loaded in the longitudinal direction of the ½ inch-wide magnetic recording medium, respectively:

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
]

Assignees

• Sony Corp

Inventors

• Yamaga Minoru
• Sekiguchi Noboru
• Sato Tooru
• Aizawa Takashi

Classifications

• G11B5/851

  Coating a support with a magnetic layer by sputtering · CPC title

• G11B5/78 Primary

  Tape carriers · CPC title

• G11B5/584

  for track following on tapes · CPC title

• G11B5/7379

  Seed layer, e.g. at least one non-magnetic layer is specifically adapted as a seed or seeding layer · CPC title

• G11B5/7266

  comprising a lubricant over the inorganic carbon coating · CPC title