Magnetic recording medium having a dimensional variation
In a magnetic recording medium, 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, and a rate of shrinkage in the longitudinal direction is 0.08% or less.
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 medium according to claim 1 , wherein a squareness ratio in a vertical direction is 65% or more.
21. The magnetic recording medium according to claim 20 , wherein the rate of shrinkage in the longitudinal direction is 0.07% or less.
22. The magnetic recording medium according to claim 20 ,
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.
23. The magnetic recording medium according to claim 20 ,
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.
24. The magnetic recording medium according to claim 20 , wherein a 1% elongation load in the longitudinal direction is 0.60 N 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.
25. The magnetic recording medium according to claim 20 ,
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.
26. The magnetic recording medium according to claim 20 , wherein a Poisson's ratio ρ is 0.25≤ρ.
27. The magnetic recording medium according to claim 20 , 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.
28. The magnetic recording medium according to claim 27 , wherein the elastic limit value σ MD does not depend on a velocity V in measurement of elastic limit.