Title: Magnetic recording elements and process of preparation

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Abstract: Magnetic recording elements which combine low modulation noise with excellent high frequency output and their process of preparation are disclosed. Such elements comprise a support having a surface with a peak-to-peak roughness up to about 0.5 micron, which surface is coated with a magnetic recording medium having a thickness in the range of 4 to about 20 microns. The magnetic recording medium comprises about 8 to 30 percent, by volume, of discrete, non-solid, nonmagnetizable voids that are substantially homogeneously dispersed therein. The magnetic recording medium also contains aligned and oriented acicular magnetizable particles dispersed in a magnetic recording layer which forms an outer surface of the magnetic recording element and has a surface smoothness, determined as percent contact area, of at least 86 percent, the ratio of the thickness of the magnetic recording medium to the peak-to-peak roughness of the support in the elements disclosed is at least 10. The process disclosed for preparing the above magnetic recording elements comprises the steps of: (a) forming a dispersion of acicular magnetizable particles in a solution of binder in solvent, (b) coating a support having a peak-to-peak roughness up to about 0.5 micron with a magnetic medium comprising a layer of the dispersion as the outermost layer with respect to the support, (c) applying a magnetic field to the medium while it still contains solvent to align the magnetic particles, (d) removing substantially all solvent within the medium while forming at least 10 percent, by volume, of substantially homogeneously dispersed, discrete, gaseous, non-magnetizable voids, and (e) compacting the medium to reduce the volume of the voids by at least 15 percent to a final volume of about 8 to 30 percent and to obtain a ratio of the medium thickness to the peak-to-peak roughness of at least 10 and often from 10 to 300 while imparting a surface smoothness, determined as percent contact area, of at least 86 percent to the outermost magnetic recording layer.


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