Magnetic recording medium
AssigneeAgfa-Gevaert
InventorsHeinrich Kober, Burkhard Nippe, Bernhard Seidel
Life of this patent
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Abstract
A magnetic recording material, preferably for tape recorders which are designed for the iron oxide bias setting and for a playback equalization of 120 .mu.s, consisting of a support and at least two layers containing magnetic pigments and binders and differing in coercivity and layer thickness, the uppermost layer containing as acicular, magnetic pigment thermally stabilized magnetite containing from 0.1 to 5% by weight of Cd, Pb, Ca, Mg, Zn, Al, Cr, W, P and/or B based on Fe.sub.3 O.sub.4. The pigments have an average crystallite size of from 30 to 35 nm and a coercivity of from 28 to 36 KA/m. These double-layer tapes have a low bias level and a high dynamic range despite a playback equalization of 120 .mu.s.
Claims5
In a magnetic tape recording material for tape recorders operable with the iron oxide bias and a playback equalization of 120 .mu.s having improved stability, a support and, arranged one above the other thereon, at least two layers containing magnetic pigments and synthetic resin binders and differing in coercivity and layer thickness, characterised in that the uppermost layer contains as acicular, magnetic pigment magnetite thermally stabilized with one or more elements comprised of an effective amount of P (expressed as P.sub.2 O.sub.5) or B (expressed as B.sub.2 O.sub.3) together with a metal selected from the group consisting of Cd, Pb, Ca, Mg, Zn, Al, Cr, W, said stabilizing element or elements being present in an amount of from 0.1 to 5% by weight based on Fe.sub.3 O.sub.4, and having an average crystallite size, as determined by X-ray photography, of from 30 to 35 nm and a coercivity of from 28 to 36 KA/m, said magnetite having a bias noise level, based on the reference level, which is lower by about 3 dB in relation to the standardized low-noise standard.
Dependencies are inferred from the claim text.