Agfa-gevaert Ag

Heinrich Kober

Burkhard Nippe

Robert Kohler

Walter Meckel

Johannes Gerum

Karlchristian Schilffarth

Hermann Perrey

Hartmut Thiele

Bernd Quiring

Hermann Brinkmeyer

Gerhard Hubler

Leo Gruber

Werner Bottcher

Helmut Schultz

Gunter Ender

Tibor Macheiner

Bernhard Seidel

A magnetic recording carrier which has improved mechanical properties as a result of a highly active cross-linking reaction of the polymeric binder is produced by carrying out the cross-linking reaction by way of oligo- and/or polyurethanes and/or polyureas containing oxadiazine trione rings in the presence of hydroxyl groups and/or aliphatic amino groups. The oligo- and polyurethanes containing the oxadiazine trione ring are reaction products of

Process for the production of a magnetic recording medium

This invention relates to a magnetic recording carrier in which the magnetic layer and/or the backing layer contains, in addition to the usual additives, radiation hardenable dispersing agents based on ethylenically unsaturated phosphoric acid ester mixtures capable of forming bataine type stuctures and consisting of reaction products of (A) an acrylic acid ester and/or oligo acrylate containing 1 OH group per molecule, (B) a tertiary alkylamine containing 1 OH group per molecule and (C) phosphorus pentoxide, the reaction products having acid numbers below 200.

Magnetic recording carrier containing radiation hardenable dispersing

The present invention relates to a magnetic storage medium consisting of a non-magnetic layer support and, applied thereto, a binder-containing magnetic layer, the binder consisting of from 25 to 100% of a thermoplastic polyurethane substantially free from reactive terminal groups obtained by reacting a linear polyester of at least one dicarboxylic acid containing from 2 to 8 carbon atoms and/or hydroxy carboxylic acid containing from 4 to 6 carbon atoms and at least one glycol containing from 2 to 6 carbon atoms, the polyester having a molecular weight of from 1200 to 6000, at least one diisocyanate and a mixture of at least two glycols containing from 2 to 20 carbon atoms, the molar fraction of the individual components not exceeding 0.8. The polyurethane has a hardness of from 80 to 100 Shore A, a tensile strength of from 30 to 75 MPa and a breaking elongation of from 320 to 520%.

Magnetic storage medium

This invention relates to the addition of organic boron compounds, prepared by either reacting boric acid with polyhydric alcohols having a total of 5 or more neighbouring OH groups per boron atom and then with polyethylene oxide in a mol ratio of 1:40, based on 1 mol of borate which is obtained, and with a carboxylic acid having from 8 to 22 carbon atoms or reacting boric acid first with polyhydric alcohols having a total of 5 to 11 neighbouring OH groups per boron atoms, and the with a carboxylic acid having from 8 to 22 carbon atoms, said boron compound being added, in a quantity of from 3 to 12, in particular from 3 to 6 parts, by weight, based on 100 parts, by weight, of magnetic pigments, and in particular of metal powders, to the grinding operation of the magnetic pigment dispersion and then processing in a known manner. The necessary degree of dispersion is achieved after a short grinding time compared to known dispersing agents, during which time the pigment particles which are initially lying together are separated into monodisperse individual particles. The favorable effect is expressed by improved alignment values in the finished magnetic tape.

Process for the production of magnetic dispersions containing binders

Magnetic recording medium using water as dispersion medium. The magnetic layer comprises as binder an aqueous dispersion of polyurethane having functional groups capable of salt formation and a magnetic pigment. The volumetric ratio of magnetic pigment to polyurethane in terms of solids content is in the range of 0.7:1 to 1.4:1.

Magnetic recording medium

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.

The winding cores are flangeless and adapted to receive magnetic tapes. For reasons of compact packaging, it is desired to be able to stack several reels of tape securely for transport. For this reason, the winding core is designed so that the height of the winding surface is equal to or slightly greater than the width of the tapes to be wound on it. In addition, the surfaces between the internal and external circumference or on the internal circumference of the winding core have projections which project upwards or downwards from the medial plane of the core by half the total height of the core. When several cores are stacked above one another, these projections interlock so that the winding surfaces are stacked as closely together as possible.

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Hohenschaeftlarn, Germany

Heinrich Kober