Agfa-gevaert Ag

Robert Kohler

Burkhard Nippe

Heinrich Kober

Dieter Giglberger

Karlchristian Schilffarth

Walter Meckel

Bernd Quiring

Friedrich Bestenreiner

Johannes Gerum

Jorn Muller

Freidrich Bestenreiner

Karl Hoeft

The present invention relates to a magnetic storage medium consisting of a non-magnetic layer support and, applied thereto, a binder-containing magnetic layer, the binder consisting of from 25 to 100% of a thermoplastic polyurethane substantially free from reactive terminal groups obtained by reacting a linear polyester of at least one dicarboxylic acid containing from 2 to 8 carbon atoms and/or hydroxy carboxylic acid containing from 4 to 6 carbon atoms and at least one glycol containing from 2 to 6 carbon atoms, the polyester having a molecular weight of from 1200 to 6000, at least one diisocyanate and a mixture of at least two glycols containing from 2 to 20 carbon atoms, the molar fraction of the individual components not exceeding 0.8. The polyurethane has a hardness of from 80 to 100 Shore A, a tensile strength of from 30 to 75 MPa and a breaking elongation of from 320 to 520%.

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.

Process for the production of magnetic dispersions containing binders

Magnetic recording medium using water as dispersion medium. The magnetic layer comprises as binder an aqueous dispersion of polyurethane having functional groups capable of salt formation and a magnetic pigment. The volumetric ratio of magnetic pigment to polyurethane in terms of solids content is in the range of 0.7:1 to 1.4:1.

Magnetic recording medium

An electrostatic charge is applied to a charge carrier and the latter is thereupon contacted with one side of a sheet-material copy carrier. Thereafter, an original is imaged onto the charge carrier to produce thereon a latent electrostatic image field which penetrates the copy carrier, whereupon the latent image is developed on the copy carrier by contacting the other side thereof with developer material.

Apparatus for electrophotographic copying with means for effecting image

Apparatus for developing latent electrostatic images on dielectric carrier sheets has a rotary cylinder whose periphery supports a carrier sheet with a latent image thereon, and a metallic block having a concave surface which constitutes a grounded electrode and defines with the exposed side of the carrier sheet on the cylinder a narrow gap of constant or gradually decreasing width, as considered in the direction of rotation of the cylinder. The block has alternating fluid-admitting and fluid-evacuating orifices which communicate with the gap and extend transversely of the path of movement of the carrier sheet. Each fluid-admitting orifice is nearer to the preceding than to the next-following fluid-evacuating orifice, and the width of the fluid-evacuating orifices exceeds the width of the fluid-admitting orifices. The block is located below the cylinder and the fluid-evacuating orifices communicate with a collecting tank into which spent developing fluid flows by gravity. The fluid-admitting orifices receive pressurized fresh developing fluid from a pump. Each unit volume of freshly admitted fluid dwells in the gap for the same interval of time because some of the fluid issuing from a fluid-admitting orifice flows forwardly toward the next-following fluid-evacuating orifice at a speed higher than the speed of the remainder of the fluid issuing from the same fluid-admitting orifice and flowing backwards toward the preceding fluid-evacuating orifice.

Growing community of inventors

Wessling, Germany

Robert Kohler