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

A magnetic tape,

• which comprises a magnetic layer comprising ferromagnetic powder and binder on a surface on one side of a nonmagnetic support and comprises a backcoat layer comprising nonmagnetic powder and binder on a surface on the other side of the nonmagnetic support, wherein:
• the backcoat layer is less than or equal to 0.30 μm in thickness;
• and
• the logarithmic decrement as determined by a pendulum viscoelasticity test on a surface on the backcoat layer side of the magnetic tape is greater than or equal to 0.010 but less than or equal to 0.060, and
• the 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 backcoat 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:
• Δ
• =
• ln
• ⁡
• (
• A
• 1
• A
• 2
• )
• +
• ln
• ⁡
• (
• A
• 2
• A
• 3
• )
• +
• …
• ⁢
• ⁢
• ln
• ⁡
• (
• A
• n
• A
• n
• +
• 1
• )
• n
• wherein the interval from one minimum displacement to the next minimum displacement is adopted as one wave period;
• the number of waves contained in the displacement-time curve during one measurement interval is denoted by n, the difference between the minimum displacement and the maximum displacement of the nth wave is denoted by An, and the logarithmic decrement is calculated using the difference between the next minimum displacement and maximum displacement of the nth wave (An+1 in the above equation).