Basf Aktiengesellschaft

Job-Werner Hartmann

Manfred Ohlinger

Werner Ostertag

Fritz Hammon

Heinz Stritzinger

Hermann Roller

Joachim Hack

Herbert Motz

Walter Schneider

Matthias Marx

Eberhard Koester

Werner Balz

Gerd Wunsch

Paul Deigner

Roland Falk

Dieter Schaefer

Eduard Schoenafinger

Volker Kiener

Friedrich Domas

Peter Nagel

Manfred Steuerwald

Werner Huebner

Aribert Krug

Werner Senkpiel

Ursula Klein

Karl Mahler

Georg Huber

Friedrich Fuchs

Ute Neumann

Horst Grosselfinger

Egon Von Gross

Hans Hauser

Philipp Pister

Franz Buettner

In order to determine the homogeneity of a magnetic dispersion, part of the dispersion is conducted through a measuring cell prior to its application to a base, the size, number and type of those regions of the magnetic dispersion which interfere with the homogeneity being determined with the aid of magnetic measurements. The measuring cell contains a magnetic head, a magnetic dispersion is made to flow in a stream of constant cross section past the air gap of the magnetic head, and a magnetic field at least partially penetrating the magnetic dispersion is produced. From the characteristics of the amplified output voltage of the magnetic head the various parameters of the inhomogeneities in the magnetic dispersion can then be ascertained.

Method and device for determining the homogeneity of magnetic dispersions

A process and apparatus for the manufacture of magnetic recording media, in which, immediately before the magnetic dispersion is applied to a base, the dispersion is subjected to shear by means of a disc rotatably mounted in a housing, by introducing it at the center of rotation of the disc and forcing it through a gap formed between the face of the disc and the wall of the housing, which gap tapers toward the rim of the disc.

Process for the manufacture of magnetic recording media

A flexible multilayer magnetic recording medium exhibiting an improved signal-to-print-through ratio coupled with an improved maximum output level and diminished dc noise, comprising a non-magnetic base and, applied thereto, at least two superposed layers consisting of a binder with magnetizable particles uniformly dispersed therein, the upper magnetic layer containing a magnetic pigment giving a signal-to-print-through ratio of less than 55db and the lower magnetic layer(s) containing a magnetic pigment giving a signal-to-print-through ratio of 55 db or more.

Flexible multilayer magnetic recording medium

Flexible multi-layer magnetic recording media comprising a non-magnetic flexible base and, applied thereto, two superposed magnetizable layers which contain a homogeneous mixture of acicular magnetic chromium dioxide in an organic binder. According to the invention, the magnetizable layer adjacent to the base contains a chromium dioxide having a specific surface area, measured by the BET method, of from 15 to 25 m.sup.2 /g, while the outer magnetic layer contains a chromium dioxide having a specific surface area, measured by the BET method, of from 26 to 35 m.sup.2 /g. Such magnetic recording media are distinguished by uniformly high sensitivity over the entire audible frequency range even if close manufacturing tolerances are not maintained.

Flexible multi-layer magnetic recording media

A process and apparatus for producing magnetic discs in which the preferred direction of orientation of the anisotropic magnetic particles, contained in an organic binder system, is tangential to the circumference of the disc. Orientation is effected, prior to solidification of the magnetic layer, by the action of a magnetic field which is formed in the plane of symmetry between at least two pairs of magnetic poles, the poles of each pair being of the same polarity and opposite each other. One pair of poles flares out in cross section toward the plane of symmetry between the pairs of poles, whereas the other pair or pairs of poles of opposite polarity, when viewed in cross section, taper toward the said plane of symmetry to a point, the distance between the poles of such pair(s) being greater than that between the flared poles, and the plane of symmetry of the pairs of poles being in the plane of the disc. Using this process and apparatus, magnetic discs with a non-magnetic metallic base are obtained, in which the anisotropic magnetic particles in the layer of fluid binder applied to the base are oriented tangentially to the circumference of the disc during spin-coating.

Device for the magnetic orientation of magnetic recording media

Coated magnetic recording media, especially video tapes and computer tapes, comprising a non-magnetic base carrying a magnetic coating which consists of a dispersion, essentially containing a finely divided magnetic pigment in an organic binder and at least one lubricant. A compound of the formula ##STR1## in which n is an integer of from 1 to 3 and R is alkyl, alkoxyalkyl or aralkyl, each of 3 to 18 carbon atoms, is used as a lubricant. The products have high abrasion resistance coupled with only little transfer of material to the magnetic heads even under fluctuating climatic conditions.

Coated magnetic recording media

Magnetic recording tape especially suitable for use as video tape and computer tape, comprising a base carrying a magnetic coating which consists essentially of a dispersion of a finely divided magnetic pigment and at least one lubricant in an organic binder. The lubricant is a compound of the formula ##STR1## IN WHICH N IS AN INTEGER OF FROM 3 TO 8 AND R.sup.1 and R.sup.2 are an alkoxy or aralkoxy radical or conjointly are an alkyldioxy radical of 3 to 18 carbon atoms. A magnetic recording tape prepared with a high proportion of such a lubricant is distinguished by high abrasion resistance coupled with a minimum transfer of material to the magnetic heads even under fluctuating climatic conditions.

Magnetic recording tape

Magnetic recording media comprising a non-magnetizable flexible base and a firmly adhering magnetic coating based on a dispersion, containing a silane, of a magnetic pigment in a polymeric binder, and a process for their manufacture. The silane is an aminoalkylsilane R.sub.n Si(OR').sub.4-n, wherein n is 1, 2 or 3, R' is alkyl of 1 to 8 carbon atoms and R is aminoalkyl of the formula with one or more primary and/or secondary amino groups and from 3 to 11 carbon atoms. Magnetic recording media comprising a magnetic coating containing such a silane exhibit better abrasion resistance and better electromagnetic properties than comparable coatings.

Magnetic recording media

A process for the manufacture of improved magnetic discs by applying a thin layer of a fluid dispersion of magnetic pigments and optional non-magnetic pigments in a binder mixture to a non-magnetic rigid base and curing the magnetic layer which has been applied. The binder consists essentially of from 60 to 90 percent by weight of a solid curable polycondensate of 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin having an epoxide equivalent weight of approximately 400 to 5,000, from 5 to 25 percent by weight of a curable allyloxybenzene-formaldehyde condensate of the resol type with free or alcohol-etherified methylol groups and a molecular weight of less thah 1,000, and from 5 to 30 percent by weight of a curable melamine-formaldehyde condensate with more than two alcohol-etherified methylol groups and a molecular weight of less than 3,000, from 10 to 35 percent by weight of the above epoxy resin being replaced by a reaction product of an epoxy group-containing polycondensate of 2,2-bis-(4-hydroxyphenyl)-propane and epichlorohydrin with the N-methylolamide of a copolymerizable olefinically unsaturated carboxylic acid of 3 to 5 carbon atoms. The magnetic layers thus produced adhere firmly to the base, can be readily ground and polished and are particularly resistant to wear when the magnetic discs are in use.

Magnetic discs having a multi-component binder

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Ludwigshafen, Germany

Job-Werner Hartmann