TECHNICAL FIELD

The present technology relates to a magnetic recording medium.

BACKGROUND ART

In recent years, in magnetic tapes (magnetic recording media) used for computer data storage, the track width and the distance between adjacent tracks are greatly reduced for improving data recording density. Thus reduction of the track width and the distance between tracks further decreases the maximum acceptable variation as dimensional variation of the tape itself caused by environmental factors such as temperature and humidity change.

Some technologies for reducing dimensional variations have been proposed. For example, in the magnetic tape medium disclosed in JP 2005-332510A, X×Y is 6×105or more and Y/Z is 6.0 or less when X is 850 kg/mm2or more or less than 850 kg/mm2, in which X is the Young's modulus of a non-magnetic support in the width direction, Y is the Young's modulus of the back layer, and Z is the Young's modulus of the layer including a magnetic layer in the width direction.

SUMMARY

It is desirable to provide a magnetic recording medium which suppresses dimensional change in the width direction by adjusting the tension applied to the tape in the longitudinal direction.

A magnetic recording medium according to an embodiment of the present technology includes a layer structure including a magnetic layer, a non-magnetic layer, and a base layer in this order, in which an average thickness tTis tT≤5.5 μm, dimensional variation Δw in a width direction to tension change in a longitudinal direction is 660 ppm/N≤Δw, and an average thickness tnof the non-magnetic layer is tn≤1.0 μm.

In the magnetic recording medium, a squareness ratio in a vertical direction may be 65% or more.

The non-magnetic layer includes Fe-based non-magnetic particles, and a particle volume of the Fe-based non-magnetic particles may be 4.0×10−5m3or less.

An average thickness tTmay be tT≤5.3 μm.

The average thickness tTmay be tT≤5.2 μm.

The average thickness tTmay be tT≤5.0 μm.

The average thickness tnof the non-magnetic layer may be tn≤0.9 μm.

The average thickness tnof the non-magnetic layer may be tn≤0.7 μm.

The dimensional variation Δw may be 700 ppm/N≤Δw.

The dimensional variation Δw may be 750 ppm/N≤Δw.

The dimensional variation Δw may be 800 ppm/N≤Δw.

The layer structure has a back layer on an opposite side of the non-magnetic layer of the base layer, and a surface roughness Rabof the back layer may be 3.0 nm≤Rab≤7.5 nm.

The layer structure has a back layer on an opposite side of the non-magnetic layer of the base layer, and 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 may be 0.20≤μ≤0.80.

A thermal expansion coefficient α of the magnetic recording medium may be 6 ppm/° C.≤α≤8 ppm/° C., and a humidity expansion coefficient β of the magnetic recording medium may be β≤5 ppm/% RH.

A Poisson's ratio ρ of the magnetic recording medium may be 0.3≤ρ. An elastic limit value σMDof the magnetic recording medium in the longitudinal direction may be 0.8 N≤σMD.

The elastic limit value σMDmay not depend on a velocity V in the measurement of elastic limit.

The magnetic layer may be vertically oriented.

The layer structure has a back layer on an opposite side to the non-magnetic layer side of the base layer, and an average thickness tbof the back layer may be tb≤0.6 μm.

According to another embodiment of the present technology, the magnetic layer may be a sputtering layer.

In a case where the magnetic layer is a sputtering layer, an average thickness tmof the magnetic layer may be 9 nm≤tm≤90 nm.

According to further embodiment of the present technology, the magnetic layer may include a magnetic powder.

If the magnetic layer includes a magnetic powder, the average thickness tmof the magnetic layer may be 35 nm≤tm≤90 nm. The magnetic powder may include an ε-iron oxide magnetic powder, a barium ferrite magnetic powder, a cobalt ferrite magnetic powder, or a strontium ferrite magnetic powder.

The squareness ratio of the magnetic recording medium in the vertical direction may be 65% or more, and the layer structure has a back layer on an opposite side of the non-magnetic layer of the base layer, and the surface roughness Rabof the back layer may be 3.0 nm≤Rab≤7.5 nm.

In the magnetic recording medium, the squareness ratio in the vertical direction may be 65% or more, and the layer structure has a back layer on an opposite side of the non-magnetic layer of the base layer, and the coefficient of friction μ of a surface of the magnetic recording medium on a side of the magnetic layer and a surface on a side of the back layer may be 0.20≤μ≤0.80.

In the magnetic recording medium, the squareness ratio in the vertical direction may be 65% or more, the thermal expansion coefficient α may be 6 ppm/° C.≤α≤9 ppm/° C., and the humidity expansion coefficient β may be β≤5.5 ppm/% RH.

In the magnetic recording medium, the squareness ratio in the vertical direction may be 65% or more, and the Poisson's ratio ρ may be 0.25≤ρ.

In the magnetic recording medium, the squareness ratio in the vertical direction may be 65% or more, and the elastic limit value σMDin the longitudinal direction may be 0.7 N≤σMD. The elastic limit value σMDmay not depend on the velocity V in the measurement of elastic limit.

