Agfa-gevaert Ag

Vacuumschmelze Gmbh

Joachim Greiner

Burkhard Nippe

Albrecht Mager

Eberhard Gartner

This invention relates to a process for the production of a magnetic recording material having at least one layer of magnetic oxidic and/or metallic needle shaped pigments with dimensional anisotropy and/or some other type of magnetic anisotropy, e.g. crystalline, dielectric or magnetic field induced anisotropy, which process may be used to produce a layer having perpendicular anisotropy or a layer which passes from an initial perpendicular anisotropy to an isotropic distribution of the preferential magnetic axes of the pigments. According to the present process, the magnetic dispersion, after having been applied to the layer support, is subjected to an external magnetic field while still in the state of a liquid suspension, with the result that the pigments move with the preferential axis thereof into the perpendicular axis of the layer, and the pigments are subsequently fixed by drying.

Process for the production of a magnetic recording material with

This invention relates to a magneto-optical storage and playback process for travelling information carriers, by recording on a magnetizable information carrier (1) in the form of a tape, disc or roller while the carrier is in motion, said information carrier having information areas which are larger than 0.2 .mu.m and smaller than 20 .mu.m in one direction of the information plane, the process being carried out by the production of a geometrical structure (4) by the action of the magnetic fields of the recorded information on particles whose greatest length is less than 0.1 .mu.m, preferably 0.02 .mu.m, and by optical scanning of these structures in which light of wavelength 0.38 to 0.8 .mu.m is diffracted on the surface of the moving information carrier (1) and diffraction images are produced which serve for the interpretation of the information.

Magneto-optical storage process

A two-part arrangement of permanent magnets with low retentivity conducting elements for the flow of magnetic force is used in order to orientate magnetically anisotropic pigments in a suspension in the direction of tape travel during the production of a magnetic tape by means of magnetic fields. The first part of the arrangement acts on the suspension with an inhomogeneous strong magnetic field of about 5000 A/cm which is narrowly restricted physically, without anticipating the orientation in the direction of tape travel. Orientation in the direction of tape travel takes place in the second part of the arrangement which has a physically extended but weaker field.

Magnetic orientation system

A flexible and resilient, magnetic shielding element fabricated out of a soft magnetic alloy is provided. This shielding element not only provides magnetic shielding, but also may be used to provide a biasing force. Thus, for example, when a magnetic head is inserted into a tape cassette, a shielding element, as provided by this invention and positioned adjacent to the magnetic head opening of the cassette and on the other side of the magnetic tape from the tape head, both shields the tape head and biases the tape against the head to afford intimate contact with the tape head. Alloys which manifest a static coercive field intensity of less than 200 mA/cm, a relative static permeability, (measured as the continuous or d.c. field permeability at 4 mA/cm), of at least 2000, a Vickers hardness of at least 180, and an elastic limit of at least 500 N/mm.sup.2 are appropriate. Crystalline as well as amorphous, soft magnetic alloys are suitable.

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Ebenhausen, Germany

Joachim Greiner