US 11,749,304 B2
Magnetic recording medium having controlled dimensional variation
Masaru Terakawa, Tokyo (JP); and Minoru Yamaga, Tokyo (JP)
Assigned to Sony Corporation, Tokyo (JP)
Filed by SONY CORPORATION, Tokyo (JP)
Filed on Apr. 7, 2022, as Appl. No. 17/715,365.
Application 17/715,365 is a continuation of application No. 17/032,725, filed on Sep. 25, 2020, granted, now 11,315,594.
Application 17/032,725 is a continuation of application No. 16/455,188, filed on Jun. 27, 2019, granted, now 10,839,847, issued on Nov. 17, 2020.
Claims priority of application No. 2019-067925 (JP), filed on Mar. 29, 2019.
Prior Publication US 2022/0230660 A1, Jul. 21, 2022
This patent is subject to a terminal disclaimer.
Int. Cl. G11B 5/62 (2006.01); G11B 5/733 (2006.01); G11B 5/706 (2006.01); G11B 5/735 (2006.01); G11B 5/596 (2006.01); G11B 5/68 (2006.01)
CPC G11B 5/62 (2013.01) [G11B 5/59688 (2013.01); G11B 5/68 (2013.01); G11B 5/70678 (2013.01); G11B 5/733 (2013.01); G11B 5/7358 (2019.05)] 19 Claims
OG exemplary drawing
 
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 tT of the magnetic recording medium is 4.0 μm≤tT≤5.3 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 680 ppm/N≤Δw≤2000 ppm/N,
a squareness ratio measured in the longitudinal direction of the magnetic recording medium is 35% or less,
an average thickness tn of the non-magnetic layer is 0.03≤tn≤1.0 μm, and
wherein the dimensional variation Δw is determined according to:

OG Complex Work Unit Math
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%.