Agfa Gevaert Nv

Pierre R De Roo

Yvan K Gilliams

Serge M Tavernier

Walter F De Winter

Robert F Janssens

Jan Gilleir

Jan J Priem

Jozef L Mampaey

Francine Van Gijsel

A method is described for preparing a concentrated dispersion of a photographically useful compound ready-for-use in coating solutions of hydrophilic colloid layers of a silver halide photographic material, wherein said compound has at least one ionisable acid site on its molecule, the said method comprising the steps of deprotonising and solubilising the said compound in alkaline medium; microprecipitating the said compound and milling the microprecipitated compound obtained, coating the said dispersion of a photographically useful compound in non-light-sensitive and/or light-sensitive hydrophilic layers of a silver halide photographic material, wherein milling proceeds during and/or after the microprecipitating step.

Method of preparing dispersions of photographically useful compounds

Magnetic carrier particles that can be positively charged triboelectrically and are suited for serving in magnetic brush toner-carrier development wherein said carrier particles comprise finely divided magnetically attractable powder dispersed in a resin binder which for at least 75% by weight consists of the acid-base reaction product of at least one acidic binder resin having an acid number in the range of 5 to 50 mg KOH/g, and at least one basic binder resin having free amin groups in an amount equivalent with 2 to 50 mg KOH/g and being present in an amount of at least 10% by weight with respect to such acidic resin.

Triboelectrically chargeable magnetic carrier particles having magnetic

Electrophoretic process and apparatus for developing an electrostatic charge pattern carried by a dielectric surface by progressively moving that surface through a development station and simultaneously progressively advancing a layer of liquid toner (11) comprised of toner particles dispersed in a carrier liquid, through that station in proximity to said charge-carrying surface, (3), and imposing an electric field bias to cause or promote selective image-wise movement of toner particles through said liquid at said development station and deposition thereof on said charge-carrying surface in a pattern representing said electrostatic charge pattern, wherein said layer of liquid toner contains toner particles in a concentration of from 2 to 25% by weight, and including the step of applying a film of a substantially toner-free non-polar liquid which is miscible with the carrier liquid of said liquid toner and which has a specific conductivity lower than 0.2 nS/m over said liquid toner layer (11) in such manner and at such a rate that each increment of such toner layer arrives at the development station, substantially free from turbulence and covered by the film of substantially toner-free liquid, the thickness of the film being such that at the development station it just makes contact with the chargecarrying surface.

Electrophoretic development of electrostatic charge images

A particulate composition of matter for magnetic brush development of electrostatic charge patterns, adapted upon mixing with magnetic carrier particles to acquire a net positive charge, which contains colorant material and thermoplastic resin binder, the colorant material comprising a salt formed from a nigrosine base and at least one carboxylic acid containing one or two carboxylic acid groups and having from 2 to 26 carbon atoms, wherein the nigrosine salt is dispersed as particles in the thermoplastic resin binder which contains a polyester derived from fumaric acid or a mixture of at least 95 mol % fumaric acid and the balance isophthalic acid and a polyol blend of propoxylated bisphenol. The charge pattern is developed by contacting the same under the influence of an applied magnetic field with a mixture of magnetic carrier particles and the particulate composition.

Electrostatic toner comprising thermoplastic resin binder for nigrosine

A toner composition of electrostatically attractable fusible powder particles suitable for fixing with simultaneous heat and pressure, having a melt viscosity at 140.degree. C. in the range of 10.sup.5 to 10.sup.6 mPa.s, an average particle size in the range of 1 to 50 .mu.m, and comprising a coloring substance and more than 80% of their volume of a mixture of: a combination of fumaric-bisphenolic and fumaric, propoxylated bisphenolic polyester resins, a sterically-hindered phenol release agent, and a melt-viscosity controlling pigment e.g. barium sulphate.

Fusible electrostatically attractable toner

Electrostatic developer composition and method for developing therewith an electrostatic charge pattern of positive charge wherein the composition is free of carrier particles and consists of powder particles containing at least 80% by weight of a mixture of at least 30% by weight of: a polyester derived from fumaric acid or a mixture of at least 95 mol % fumaric acid and isophthalic acid and a polyol blend of propoxylated bisphenol characterized by the formula: ##STR1## wherein m and n are integers and added together average from 2 to 7, and at least one of (1) a copolymer of ethylene, maleic acid and/or maleic anhydride wherein from 50 to 70 mol % of ethylene repeating units are present, and (2) a wax of the group consisting of castor wax and montan wax.

Toner composition for electrostatic image development

Composition of matter for electrostatic image development and a method for developing therewith an electrostatic charge pattern of positive charge, wherein the composition consists of powder particles containing at least 80% by weight of a mixture of at least 30% by weight of:

Composition of matter and method for electrostatic image development

Carrier beads for use in an electrostatographic developer mixture comprise a glass core or iron-containing metal core enveloped with a coating of a copolymer of N-vinylcarbazole, trialkoxyvinylsilane and/or triacetoxyvinylsilane and optionally one or both of the monomers of the group consisting of C.sub.1 -C.sub.4 alkyl (meth)acrylate and styrene.

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Schoten, Belgium

Pierre R De Roo