Agfa-Gevaert Ag

Agfa Gevaert Nv

Basf Magnetics Gmbh

Agfa-Gevaert Aktiengesellshcaft

Hans-Heinrich Credner

Karl-Wilhelm Schranz

Ernst Meier

Marcel J Monbaliu

Raphael K Van Poucke

Wolfgang Lassig

Attila Vass

Wolf-Dieter Schroeer

Karlfried Wedemeyer

Wolfgang Himmelmann

Alfons Klein

Fritz Nittel

George F Van Veelen

Johannes Gerum

Willibald Pelz

Siegfried Schleger

Horst Schulz

Marc Godfried Mannens

Gaston Jacob Benoy

Rigobert Otto

Werner Wimbersky

Albrecht Koller

Hildegard Fischer

Fritz Benker

Walter Schulte

Roger Henri Vrydaghs

In the preparation of dispersions of magnetic pigments, it was found that excellent dispersion stability is achieved when compounds which are selected from the group consisting of quaternary ammonium compounds, guanidines, piperidines, alkylated or ethoxylated amines, diamines, polyamines or mixtures thereof, ethanolic KOH solutions, metal alkoxylates, Grignard compounds and certain metal hydrides are used as codispersants. The compounds are added in an amount of 0.15-4% by weight, based on the magnetic pigment.

Magnetic coating dispersion

In the preparation of dispersions of magnetic pigments in organic solvents, dispersants which have a sterically stabilizing effect are used. Milling results in division of the pigment aggregates, which combine again as a result of attractive forces to give secondary agglomerates in the event of poor stabilization. These flocculating materials must be removed from the dispersion by expensive filtration. If an increase in the fineness or pigment batch fluctuations lead to an increase in the secondary agglomerates, filter breakthroughs may occur, resulting in a dramatic reduction in the yield of magnetic recording medium. It was found that excellent dispersion stability is achieved when the magnetic pigments are first precoated with a long-chain dispersant. Subsequently, the use of charge-generating, low molecular weight codispersants, a charge build-up on the pigment is specifically induced by means of bases or acids. The electrostatic repulsion which additionally becomes effective leads to an increase in the dispersion stability. The charges on the pigment are monitored by means of ESA measurements (electrokinetic sound amplitude). These ESA measurements make it possible to establish the order of addition of the dispersants and the optimum amount of codispersant.

Magnetic recording medium having a magnetic layer prepared from magnetic

It has been found that a magnetic tape which may be used in particular for video recording and which has excellent abrasive and cleaning properties for all those parts of the cassette or rather the recording and play-back unit which come into contact with the magnetic layer can be obtained by addition of a non-magnetic powder having a Mohs' hardness of at least 9 and a primary particle size of 0.3 to 2 .mu.m to the magnetic pigment, which has a BET surface of at least 26 m.sup.2 /g, in the magnetic dispersion, the magnetic layer of the magnetic tape having an Ra value of less than 0.02 .mu.m. The best results were obtained with cubic Al.sub.2 O.sub.3 particles added in a quantity of 1.1 to 4.4% by weight, based on the magnetic pigment.

Magnetic tape containing abrasives

An improved process for the production of a magnetic recording material including a non-magnetic layer support and, cast thereon, a magnetic dispersion including a mixture of at least two different batches of finely divided magnetic pigments finely dispersed in a polymeric binder is characterized in that the magnetic pigment batches are separately finely dispersed in a polymeric binder and/or a dispersion aid and/or a solvent until the necessary degree of dispersion is reached, after which they are combined, optionally provided with further additives and applied to the layer support, the degree of dispersion of the magnetic dispersions preferably being continuously determined by a colorimetric arrangement.

Process for the production of a magnetic recording material

Sulfilimine compounds of formula I ##STR1## wherein X is the integrating residue of a photographically active compound H.sub.2 N--A--X and

Photographic recording material for diffusion processes and new

Sulfilimine compounds of formula I ##STR1## in which R.sup.3 is the residue of a diffusible photographically active compound can be split reductively to release the residue together with a group --SO.sub.2 --NH.sub.2. When R.sup.3 represents the radical of a dye or dye precursor the sulfilimines are useful as color providing compounds in dye diffusion transfer processes.

Photographic recording material for diffusion processes and useful

The condensation of an .alpha.-halogen carbonyl compound with carbamic acid esters in the presence of a basic condensing agent and an aprotic solvent enables the production of oxazolinone-2-compounds in a high degree of purity, and in high yields in one step by using simple and readily available starting compounds.

Process for the production of oxazolinone-2-compounds

An improvement in the prevention color-fog and staining in color-photographic materials is obtained by the inclusion of acylamino substituted hydroquinones derivatives. The compounds can easily be synthesized do not crystalize from their dispersions and are not oxidized to colored by-products during development.

Color photographic materials containing an antistain agent

Undesired color fog obtained on color development of a color photographic material with a primary aromatic amino color developing agent may be reduced when the development is carried out in the presence of an antifogging agent (antistaining agent) of the formula ##STR1## in which R.sup.1 is an acyl group and R.sup.2 and R.sub.3 are (same or different) hydrogen, alkyl, halogen, sulfo or carboxyl. The antistaining agent is preferable incorporated in non-diffusible form in one or more of the layers of the photographic material.

Color photographic materials containing anti-fogging agents

Color photographic material containing a fast-acting hardener, which acts by activating carboxyl groups, wherein said material contains a 2-pyrazolin-5-one coupler precursor corresponding to one of the following general formulae I or II: ##STR1## wherein EACH OF R.sup.1, R and Y are substituents of the type used in 2-pyrazolin-5-one color couplers, and

Photographic silver halide color material containing fast-acting

3-Anilino-5-pyrazolyl alkylcarbonates and arylcarbonates are described for use in silver halide color photography as color coupler precursor compounds containing no active methylene group so that they do not take part in undesirable side-reactions before color development.

Photographic material containing 3-anilino-5-pyrazolylalkylcarbonate or

2-Acyl-3-pyrazolin-5-one couplers are provided for use in color photography which upon color development form 2-pyrazolin-5-one couplers capable of coupling with the oxidation products of the color developing agent.

Photographic material containing 2-acyl-2-pyrazolin-5-on-couplers

This invention relates to a color photographic material with at least one silver halide emulsion layer having improved stability against crystallization and which contains in dispersed form a open chain keto methylene coupler a naphtholic or pyrazolone color coupler substituted with a 2-cyclo-pentyl-4-t-butyl-phenoxy group in a non-coupling position.

Growing community of inventors

Hohenschaeftlarn, Germany

Hans-Heinrich Credner