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Magnetic tape having controlled surface properties of the magnetic layer and method of manufacturing the same

  • US 10,026,434 B2
  • Filed: 08/19/2016
  • Issued: 07/17/2018
  • Est. Priority Date: 08/21/2015
  • Status: Active Grant
First Claim
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1. A magnetic tape,which comprises a magnetic layer comprising ferromagnetic powder and binder on a nonmagnetic support,wherein the centerline average surface roughness Ra as measured on a surface on the magnetic layer side of the magnetic tape is less than or equal to 1.8 nm,the logarithmic decrement as determined by a pendulum viscoelasticity test on the surface on the magnetic layer side of the magnetic tape is greater than or equal to 0.010 but less than or equal to 0.050, andthe logarithmic decrement is determined by the following method:

  • securing a measurement sample of the magnetic tape with the measurement surface, which is the surface on the magnetic layer side, facing upward on a substrate in a pendulum viscoelasticity tester;

    disposing a columnar cylinder edge which is 4 mm in diameter and equipped with a pendulum 13 g in weight on the measurement surface of the measurement sample such that the long axis direction of the columnar cylinder edge runs parallel to the longitudinal direction of the measurement sample;

    raising the surface temperature of the substrate on which the measurement sample has been positioned at a rate of less than or equal to 5°

    C./min up to 80°

    C.;

    inducing initial oscillation of the pendulum;

    monitoring the displacement of the pendulum while it is oscillating to obtain a displacement-time curve for a measurement interval of greater than or equal to 10 minutes; and

    obtaining the logarithmic decrement Δ

    from the following equation;

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