Tdk Corporation

Naoto Yajima

Takayoshi Kuwajima

Akihiko Seki

Hiroyuki Yamada

Kenichi Kitamura

The present invention provides a magnetic recording medium comprising a magnetic layer with excellent surface smoothness, which comprises a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m that is ideal for short wavelength recording, and displays superior electromagnetic conversion characteristics. The magnetic recording medium comprises a magnetic layer containing at least a ferromagnetic powder and a binder resin on one surface of a non-magnetic support, wherein the thickness of the magnetic layer is within a range from 0.03 to 0.30 &#x3bc;m, and the number of concavities with a depth of 30 nm or greater in the surface of the magnetic layer is 5 per 1 cmof surface area or less. Preferably, the value of the average depth Rv6 of the surface of the magnetic layer, as measured by a contact type surface roughness meter, is 12 nm or less.

Magnetic recording medium

The present invention provides a magnetic recording medium comprising a thin film magnetic layer of thickness in a range from 0.03 to 0.30 &#x3bc;m, and having excellent surface smoothness and superior electromagnetic conversion characteristics. The magnetic recording medium comprises a lower non-magnetic layer containing at least a non-magnetic powder and a binder resin on one surface of a non-magnetic support, an upper magnetic layer containing at least a ferromagnetic powder and a binder resin on the lower non-magnetic layer, and a back coat layer on the other surface of the non-magnetic support, wherein the thickness of the upper magnetic layer is within the range from 0.03 to 0.30 &#x3bc;m, the AFM surface roughness Ra of the upper magnetic layer is 6 nm or less, and the number of concavities with a depth of 30 nm or greater in the surface of the upper magnetic layer is 5 per 1 cmof surface area or less.

A magnetic recording medium is prepared by coating a dispersion of non-magnetic powder and ferromagnetic powder in a binder and a dispersion of ferromagnetic powder in a binder to a non-magnetic substrate by a wet-on-wet coating technique to form subordinate and magnetic layers on the substrate, and subjecting the layers to magnetic field orientation. The subordinate layer has a Br of 80 to 400 gauss, and the magnetic layer has a thickness of 0.1 to 0.4 &#x3bc;m. The medium has surface smoothness and good electromagnetic characteristics and lends itself to recording and reproducing signals having a minimum wavelength of 0.2 to 0.7 &#x3bc;m.

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Tokyo, Japan

Naoto Yajima