Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: In a process for the production of magnetic recording media by applying a layer of a dispersion of a magnetic pigment in a polyurethane-containing binder and a solvent to non-magnetic supports, small amounts of ethylenically unsaturated polymerizable carboxylic acids or their anhydrides with or without copolymerizable monomers are added and polymerized during dispersion of the magnetic pigment. Recording media produced by this process exhibit excellent output level, coefficient of friction and electrical resistance values and have particularly good operational durability.

Abstract: 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.

Abstract: A magnetic recording medium in the form of a card having a non-magnetic support with a magnetic coating on one side of the support and a backcoating on the opposite side of the support, which backcoating exhibits improved scratch resistance and adherence to the support and improved frictional characteristics and consists essentially of 20 to 50% by weight of a binder mixture containing 10 to 60% by weight of an elastomeric polyurethane and, incorporated in the binder mixture, a non-magnetic pulverulent mixture of 10 to 40% by weight of conductive carbon powder and 60 to 90% by weight of platelet-shaped and spherical particles.

Abstract: The invention relates to magnetic discs in which first a non-magnetic intermediate layer and then the magnetic coating are applied by conventional methods to an aluminum disc. The intermediate layer applied to the non-magnetic metallic carrier disc is a hard non-magnetic coating which can be polished and which consists of a dispersion of a pulverulent mixture of finely divided inorganic non-magnetic pigments having a Mohs' hardness of at least 7 in a binder which can be cured and which provides firm cohesion of the pigment particles and good adhesion thereof to the non-magnetic base disc, the pigment mixture containing at least 3 percent by weight of corundum powder having a particle size of from about 1 to 20.mu.u. Magnetic discs with very thin magnetic coatings which possess good magnetic and mechanical properties and whose thickness varies only minimally are thus produced in a simple manner.

Abstract: 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.