Patent · US Expired

Document identification employing exchange-anisotropic magnetic material

US4438462A · kind A · utility

3Cited by

9References

4Claims

0Family size

Assignee

BASF SE

Inventors

Eberhard Koester · Bischofswerda, DE
Joachim Hack · Ludwigshafen, DE
Manfred Steuerwald · Bischofswerda, DE

Key dates

Filing date	Dec 3, 1980
Grant date	Mar 20, 1984
Priority date	—
Expiry date	Dec 3, 2000

Classification

Technology area (CPC G)Physics
CPC primaryG07D7/12
WIPO fieldControl
WIPO sectorInstruments

Abstract

A process for authenticating recording media which are to be safeguarded against falsification and which possess a layer of exchange-anisotropic magnetic material, by determining the residual recording which is left over, because of the exchange anisotropy of the magnetic material, from a recording of a sequence of signals after exposure of the material to a specific temperature cycle and, subsequently, to a magnetic AC field which decreases to zero, and an apparatus for carrying out the said process.

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