Agfa-gevaert Ag

Basf Magnetics Gmbh

Agfa-gevaert Aktiengesellshcaft

Johannes Gerum

Walter Meckel

Burkhard Nippe

Heinrich Kober

Horst Schulz

Hans-Heinrich Credner

Robert Kohler

Jurgen Sauter

Werner Wimbersky

A magnetic recording medium consisting of a flexible layer support and a magnetic layer consisting predominantly of magnetic particles finely divided in a binder and nonmagnetic additives applied to the layer support is obtained with improved orientation of the magnetic pigments by adding a dispersion stabilizing component to the magnetic dispersion at a uniform rate over the whole period of dispersion. Highly purified lecithin or a mixed ester of a polyethoxy phosphate ester or ethylene diaminodistearate, a polyurethane resin containing sulphonate groups or a vinyl chloride/vinyl alcohol copolymer is preferred as stabilizing additive.

Method of preparing a magnetic recording medium

An improved process for the production of a magnetic recording material including a non-magnetic layer support and, cast thereon, a magnetic dispersion including a mixture of at least two different batches of finely divided magnetic pigments finely dispersed in a polymeric binder is characterized in that the magnetic pigment batches are separately finely dispersed in a polymeric binder and/or a dispersion aid and/or a solvent until the necessary degree of dispersion is reached, after which they are combined, optionally provided with further additives and applied to the layer support, the degree of dispersion of the magnetic dispersions preferably being continuously determined by a colorimetric arrangement.

Process for the production of a magnetic recording material

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

What is claimed is a magnetic storage medium in which the polyurethane binder system forms a three-dimensional network independently of reactive low molecular weight substances present on the magnetic pigment or in the dispersion and the production of such a storage medium. The binder in the colored magnetic layer consists of a reaction product of polyisocyanates having an average functionality of from 2.1 to 4 (A) with predominantly difunctional aromatic amino-terminated polyurethanes having an average molecular weight of at least 10,000 (B) and optionally one or more hydroxyl group-containing polyesters having an OH number of from 100 to 450 (C), and/or predominantly difunctional aromatic polyamines having a molecular weight of from 100 to 400 (D) the ratio of isocyanate groups present in (A) to the isocyanate reactive groups present in (B), (C) and (D) being from 0.3:1 to 20:1, preferably from 0.8:1 to 20:1. With this binder system, it has been possible to achieve direct linkage of the polymeric binder chains and to suppress side reactions. This has enabled a soft polyurethane agent to be used, with the result of smooth dispersion of the magnetic lacquer and hence increase in the signal/noise ratio of the magnetic recording medium. The subsequent cross-linking which takes place according to the present invention enables the mechanical properties of the recording medium to be adjusted to the exact result required after the magnetic lacquer has been applied to a support.

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.

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Unterpfaffenhofen, Germany

Johannes Gerum