Emtec Magnetics Gmbh

Basf Magnetics Gmbh

Peter Nagel

Hans-Dieter Zettler

Axel Sch&uuml;nemann

Werner Lenz

Volker Richter

Hans-Gunter Wagner

Michel Munch

Norbert Gilbert

Ingo Blaul

Process for the preparation of a magnetic dispersion for magnetic recording media and magnetic recording media produced therewith

A process for the preparation of high-quality magnetic dispersions having an Hc>120 kA/m, a residual induction Mr/Mm &gE;0.9 and an orientation ratio of about 2.7 achieves, with a self-purging single-shaft blade-type kneading apparatus, very advantageous magnetic values of the magnetic coatings and excellent tape characteristics if at least a) the radial shear gradient in the gap between blade circumference and housing wall is from about 150 to about 1600, in particular from about 500 to about 1400, 1/sec, and b) the circumferential velocity of the kneading blade is from about 20 to about 80, in particular from about 35 to about 60, cm/sec.

A knife coater for the application of one or more magnetizable dispersions located one on top of the other to a moving flexible substrate by means of a plurality of coater slots which are arranged essentially horizontally and parallel to one another in a multipart block and are fed from reservoirs is described, the outlet orifices of the coater slots being essentially opposite the summit of a concave support surface for the substrate, the substrate transporting the applied layers, the outlet surfaces of the coater block which are opposite the support surface being adapted to the radius of the roll and the inflow gap being larger than the outflow gap.

Apparatus for the production of a magnetic recording medium

An extrusion coater for the production of a magnetic recording medium having at least one coater slot is described, the lower lip arranged in a direction opposite to the running direction of the substrate and displaced forward relative to the upper lip containing, in its interior, a permanent magnet which is oriented approximately parallel to the upper edge of the lower lip and whose field lines are roughly perpendicular to the coating direction of the magnetic dispersion flowing through the coater slot. By means of this arrangement, it is possible substantially to reduce the layer thickness while achieving a satisfactory coating and also considerably to reduce the edge bead.

Extrusion coater for the production of a magnetic recording medium

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Willstatt, Germany

Peter Nagel