Tdk Corporation

Yoshisuke Yamakawa

Hiroshi Kawahara

Yasumichi Tokuoka

Akio Watanabe

Yoshihiro Honjo

Eizo Tsunoda

Kiyoto Fukushima

Masashi Hayama

Koji Matsuno

A magnetic recording medium records two or more signals having different frequency bands by frequency multiplex recording. The non-magnetic substrate includes a first magnetic layer and a second magnetic layer on that order, said second magnetic layer having a thickness amounting to 70% or less of the shortest recording wavelength of the signals to be recorded.

Magnetic recording media and method for making them

A lapping tape has an abrasive coat which comprises an acicular iron oxide powder having a surface area of at least 30 m.sup.2 /g as determined by the BET method and a granular inorganic powder having a Moh's hardness of more than 7 and contained in an amount of from 2.0 to 30 percent by weight on the basis of the weight of the oxide powder. The coat has a centerline mean roughness between 0.015 and 0.03 .mu.m. Preferably the acicular iron oxide is magnetic, and the inorganic powder ranges in particle diameter from 0.05 to 0.4 .mu.m.

Lapping tape

A magnetic recording medium is used with a magnetic recording system in which a baseband recording signal is recorded on a magnetic recording medium and a surface-band recording signal with the effective recording depth being smaller than that of the baseband recording signal is then recorded thereon in superimposed relation. The non-magnetic substrate includes thereon a first magnetic layer and a second magnetic layer on that order, said second magnetic layer having a thickness substantially equal to the effective recording depth of said surface-band recording signal and a coercivity higher than that of said first magnetic layer.

Magnetic recording media having two magnetic layers; the first for

A magnetic recording medium having a magnetic coating containing therein ferromagnetic metal powder provided on a base film, wherein the magnetic recording medium being characterized in that the surface roughness of the magnetic coating, i.e., the surface roughness R.sub.rms (a unit of measurement of .mu.m) with respect to a waveform having a wavelength P in a range of from 3 to 50 .mu.m out of groups of waveforms constituting the cross-sectional waveform of the surface of the magnetic coating, satisfies the following equation.

Method of making a magnetic recording medium

A magnetic recording medium having a magnetic coating containing therein ferromagnetic metal powder provided on a base film, wherein the magnetic recording medium being characterized in that the surface roughness of the magnetic coating, i.e., the surface roughness R.sub.rms (a unit of measurement of .mu.m) with respect to a waveform having a wavelength P in a range of from 3 to 50 .mu.m out of groups of waveforms constituting the cross-sectional waveform of the surface of the magentic coating, satisfies the following equation:

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Niiza, Japan

Yoshisuke Yamakawa