Patent · US Expired

Magnetic recording medium

US4323621A · kind A · utility

18Cited by

14References

5Claims

0Family size

Assignee

Agfa-Gevaert NV · BE

Inventors

Heinrich Kober · Starnberg, DE
Burkhard Nippe · Munich, DE
Bernhard Seidel · Murnau am Staffelsee, DE

Key dates

Filing date	Jan 12, 1979
Grant date	Apr 6, 1982
Priority date	—
Expiry date	Jan 12, 1999

Classification

Technology area (CPC Y)Emerging Cross-Sectional Technologies
CPC primaryY10T428/257
WIPO fieldAudio-visual technology
WIPO sectorElectrical engineering

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.

Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.