Magnetic recording medium having controlled dimensional variation

Patent metadata

Field	Value
Publication number	US-11315594-B2
Application number	US-202017032725-A
Country	US
Kind code	B2
Filing date	Sep 25, 2020
Priority date	Mar 29, 2019
Publication date	Apr 26, 2022
Grant date	Apr 26, 2022

Abstract

A magnetic recording medium is provided and includes a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in this order, in which an average thickness tT of the magnetic recording medium is 3.5 μm≤tT≤5.3 μm, a dimensional variation Δw in a width direction of the magnetic recording medium to tension change in a longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤2000 ppm/N, and an average thickness tn of the non-magnetic layer is tn≤1.0 μm.

First claim

The invention is claimed as follows:

1. A magnetic recording medium comprising:
a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in order,
in which an average thickness t T of the magnetic recording medium is 4.0 μm≤t T ≤5.5 μm,
the magnetic layer includes a plurality of servo bands along a longitudinal direction of the magnetic recording medium,
the magnetic layer includes a magnetic powder and a first binder,
the non-magnetic layer includes a non-magnetic powder and a second binder,
the base layer includes a polyester,
a dimensional variation Δw in a width direction of the magnetic recording medium to tension change in the longitudinal direction of the magnetic recording medium is 700 ppm/N≤Δw≤2000 ppm/N,
an average thickness t n of the non-magnetic layer is 0.03≤t n ≤1.0 μm, 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 of the magnetic recording medium and under a measurement environment including a temperature of 25° C. and a relative humidity of 50% and a width of the sample of the magnetic recording medium is ½ inch prior to being subject to a load under the measurement environment including the temperature of 25° C. and the relative humidity of 50%.

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

3. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 750 ppm/N≤Δw≤2000 ppm/N.

4. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 800 ppm/N≤Δw≤2000 ppm/N.

5. The magnetic recording medium according to claim 1 , wherein the layer structure includes a layer on the non-magnetic layer, wherein the layer is between the non-magnetic layer and the magnetic layer, and wherein a surface roughness R ab of the back layer is 3.0 nm≤R ab ≤7.5 nm.

6. The magnetic recording medium according to claim 1 , wherein the layer structure includes a layer on the non-magnetic layer, wherein the layer is between the non-magnetic layer and the magnetic layer, and wherein a coefficient of friction μ between a surface of the magnetic recording medium on a side of the magnetic layer and a surface on a side of the back layer is 0.20≤μ≤ 0 . 80 .

7. The magnetic recording medium according to claim 1 , wherein a thermal expansion coefficient α is 6 ppm/° C.≤α≤9 ppm/° C., and a humidity expansion coefficient β is β≤5.5 ppm/% RH.

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

9. 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.

10. The magnetic recording medium according to claim 9 , wherein the elastic limit value a MD does not depend on a velocity V in measurement of elastic limit.

11. The magnetic recording medium according to claim 1 , wherein the magnetic layer is vertically oriented.

12. The magnetic recording medium according to claim 1 , wherein the dimensional variation Δw is 700 ppm/N≤Δw≤800 ppm/N.

13. The magnetic recording medium according to claim 1 , wherein the average thickness tn of the non-magnetic layer is tn≤0.7 μm.

14. The magnetic recording medium according to claim 1 , wherein the average thickness t T is t T <5.3 μm.

Assignees

• Sony Corp

Inventors

• Terakawa Masaru
• Yamaga Minoru

Classifications

• G11B5/7379

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

• G11B5/62 Primary

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

• G11B5/7358 Primary

  specially adapted for achieving a specific property, e.g. average roughness [Ra] · 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

• G11B5/59688

  Servo signal format patterns or signal processing thereof, e.g. dual, tri, quad, burst signal patterns · CPC title