Basf Magnetics Gmbh

Emtec Magnetics Gmbh

Basf Aktiengesellschaft

Imation Corporation

Ronald J Veitch

Helmut Jakusch

Ekkehard Schwab

Peter Heilmann

Manfred Ohlinger

Albert Kohl

Harald Jachow

Rudi Lehnert

Werner Lenz

Norbert Schneider

Helmut Auweter

Ria Kress

Volker Koch

Johannes Sandrock

August Lehner

Michael Bobrich

Norbert Mueller

Hans J Richter

Andreas Ilmer

Reinhard Koerner

Emil Pfannebecker

Erich Hoffmann

Gerhard Soehring

Bernd Hoppner

Werner H&uuml;bner

Gunther Bettinger

Stefan M&uuml;ller

Hartmut Heene

Stefan Müller

Reinhard K Orner

Bernd H Oppner

Multilayer magnetic recording medium which is suitable for high recording densities and the recording of digital data, has very good electromagnetic recording properties and good surface smoothness and can absorb a large amount of lubricant in the lower layer and has at least one upper magnetic recording layer less than 0.5 &#x3bc;m thick and at least one lower layer which contains a magnetically soft pigment.

Magnetic recording medium

Multilayer magnetic recording medium is suitable for high recording densities and the recording of digital data, has very good electromagnetic recording properties in the entire recording wavelength range and good mechanical properties and possesses a flat frequency response and which has at least one upper magnetic recording layer less than 0.5 &mgr;m thick and at least one lower layer which contains a magnetically soft pigment.

Described are tape-type magnetic recording media (I) including a non-magnetic substrate (III), at least one film applied to the substrate and, in at least one of these films, an inorganic acicular pigment (II) suitable for use as a supporting pigment, the ratio of the mean length to the mean diameter of the pigment (II) being at least 3 and the mean modulus of elasticity of the films being not less than 15 GPa in the longitudinal direction of the tape-type recording medium (I).

Magnetic recording media

Temperature indicator for refrigerated products or the like

A longitudinally oriented magnetic recording medium is described which has advantageous properties for digital recording, ie. a very small pulse width and high output level, and wherein the quotient l.sub.r /(d.multidot.L) (l.sub.r =residual polarization in mT, d=layer thickness in .mu.m, L=mean particle length in nm) is greater than 18 and the pulse width stated as PW.sub.50 is smaller than 500 nm.

Magnetic recording apparatus with magnetic recording medium having high

A finely divided acicular CrO.sub.2 modified with iron, tellurium and/or antimony and having a high coercive force possesses improved heat stability of the residual induction and a relatively narrow distribution of the particle size and of the coercive force. This CrO.sub.2 pigment is obtained by a method in which the iron compound used for the modification is iron oxalate, which is employed in an amount of 1-10% by weight, based on the theoretical CrO.sub.2 yield.

Finely divided acicular magnetic modified chromium dioxide

An apparatus for checking deep-frozen food, which irreversibly indicates if an additional storage temperature has been exceeded, is described. A flat plastic bag having transparent walls, into which eutectic mixture having a liquid/solid phase transition in the range from 0.degree. to -50.degree. C. has been introduced, together with a magnetic dispersion consisting of finely divided magnetic pigments, has a heat-conducting connection to the material to be frozen. A magnetic stripe which contains a magnetically recorded pattern and which remains connected to the bag until the indicating apparatus together with the material to be frozen has been cooled below the limiting temperature is stuck to the bag. The magnetic stripe is then removed. If the permissible limiting temperature is exceeded, the optically or magnetically readable structure produced by the magnetic stripe in the indicator bag is eliminated, permitting easy checking of the deep-frozen food. The present invention permits many potential variations by combination of a plurality of applied magnetic stripes.

Temperature indicator for deep-frozen products

Acicular cobalt-containing magnetic iron oxides having a high coercive force and a core/shell structure and hence low temperature dependence of the coercive force are prepared by a process in which, in a first stage, surface activation is effected by means of iron(II) and cobalt ions under alkaline conditions on the iron oxide core under an inert gas atmosphere and thereafter, in a second stage, an epitactic coating of cobalt ferrite is applied, which coating is formed oxidatively from iron (II) and cobalt (II) hydroxide, likewise under alkaline reaction conditions. The total amount of cobalt ions used for doping remains unchanged compared with the known doped iron oxides or is even smaller. In the second process stage, the achievable coercive force can be controlled by the proportion of air in the gas mixture during the formation of the epitactic coating.

Preparation of acicular cobalt-containing magnetic iron oxide

A magnetic recording medium comprising a nonmagnetic substrate and at least one magnetic layer applied thereon and containing an acicular chromium dioxide uniformly distributed in a polymeric binder and additives and having a coercive force of at least 60 kA/m, a mean particle length of the chromium dioxide of less than 300 nm, whose factor HD according to the formula ##EQU1## where KT is the coercive force of the magnetic layer in [kA/m], measured in an external field of 380 kA/m, L is the mean particle length and .DELTA.L is the range of the particle size distribution, determined from the numerical distribution of the particle length, both measured in [nm], is greater than 1.85, and a process for the preparation of this chromium dioxide.

Process for preparing modified chromium dioxide

Acicular, cobalt-modified iron oxides consisting of a core of an iron oxide of the formula FeO.sub.x where x is from 1.33 to 1.5 and a ferrite shell which contains a total amount of from 0.4 to 12% by weight of cobalt ions and not more than 5% by weight of iron(II) ions, the percentages being based on the total amount of the material, which iron oxides have improved aging resistance, particularly with regard to the coercive forces, and a process for their preparation.

Acicular cobalt-modified iron oxides and their preparation

A process for the production of magnetic recording media having stochastic orientation of the magnetic anisotropic particles in the magnetic layer with the aid of a magnetic drum rotating above the still fluid dispersion layer and containing radially arranged permanent magnets of alternating polarity, and a corresponding apparatus for carrying out the process.

Stochastic orientation of magnetic recording media

Growing community of inventors

Maxdorf, Germany

Ronald J Veitch