Eastman-kodak Company

William E Yoerger

Wayne Thomas Ferrar

Frank A Pettrone

John M McCabe

Dinesh Tyagi

Michael T Regan

Louis J Sorriero

William J Staudenmayer

James A Van Allan

John F Wright

Jean E Jones

William C Lewis

Robert P Darrow

Carrier particles for developers used in electrostatographic imaging processes such as electrophotography comprise core particles such as strontium ferrite having a coating that comprises a silicone resin admixed with an alkali metal salt of an organic acid. The novel carrier particles provide faster charging rates for toner, less toner throw-off and improved charge stability.

Carrier particles for electrostatographic developers

This invention provides an electrophotographic carrier comprising hard ferrite particles, said particles having a coating comprising a silicone resin and a colloidal silica.

Coated hard ferrite carrier particles

A method of modifying the triboelectric charging propensity electrostatographic developer carrier particles, comprising the steps of:

Method of depositing insoluble metal salt deposits on

Carrier particles for use in negative electrostatographic developers wherein said particles bear, based on the weight of the carrier particles, from 0.1 to 2 weight percent of deposits selected from the group consisting of (a) strontium carbonate, (b) insoluble metal hydroxides, (c) an insoluble metal hydrated oxide, and (d) mixtures thereof; provided that when the said carrier particles bear a polymeric flurocarbon coating the deposit is other than strontium carbonate.

Carrier particles bearing insoluble metal salt deposits

The invention provides a mixture of coated carrier particles suitable for use in dry electrographic developer wherein each of the types of carrier particles occupies a position in the triboelectric continuum different from the position of the other type and the level of charge to which the mixture of carrier particles charges the toner in a developer continuously increases or decreases between a high level in which said mixture comprises all of one type of carrier particles to a low level in which said mixture comprises all of the other type of carrier particles. This type of carrier provides a simple way to adjust the charge on the toner provided by the carrier, that is, more of one of the types of carrier particles in the mixture can be added to the toner to either increase or decrease the charge on the toner.

Mixture of carrier particles useful in electrographic developers

A method for modifying the triboelectric charging propensity of particles coated with fluorohydrocarbon polymer for use as carriers in electrostatographic development comprising contacting the particles with a basic solution including a reducing agent for said particles and optionally including an oxidizing agent for said particles and carriers and developers produced by that method.

Method of modifying the charging propensity of carrier particles for

Electrostatographic carrier particles with improved conductivity and stability are prepared from magnetic stainless steel particles. The particles are treated by submersion in an aqueous oxalic acid solution. The passivated stainless steel carrier particles, preferably after being first coated with a resin, may then be mixed with toner powder for electrographic dry development.

Preparation of magnetic carrier particles

Magnetic carrier core particles are provided which are coated with a Werner complex. The coating is readily accomplished by dispersing magnetic core particles in a solution of the Werner type complex. A hydroxyl group containing polymer can also be present which functions to enhance coating thickness. The Werner complexes are highly reactive, bond strongly to hydroxyl groups, and absorb readily into the core particles. Coated particles display excellent useful life capability and developer compositions containing such coated cores produce high resolution developed images.

Magnetic carrier cores coated with perfluorinated Werner complexes and

The invention provides coated carrier particles and dry electrographic developers comprising a mixture of the carrier particles and toner particles. Each of the carrier particles comprises a core particle having a polymeric overcoat comprising a blend of a fluorine-containing polymer and a modifying polymer comprising poly(p-t-butylstyrene) or a copolymer of p-t-butylstyrene and a C.sub.1 -C.sub.4 alkyl methacrylate.

Coated carrier particles and electrographic developers containing them

In the electrographic developer compositions, the performance of strontium ferrite or barium ferrite carrier particles is improved by treating the carrier particles with an aqueous acid solution. This treatment reduces the tendency toward early life dusting of strontium or barium ferrites and prevents contamination of the toner particles.

Method for improving performance of barium and strontium ferrite carrier

The invention provides coated carrier particles suitable for use in dry electrographic developers comprising a mixture of the carrier particles and toner particles. Each of the carrier particles comprises a core particle having a polymeric overcoat comprising poly(p-t-butylstyrene) or a copolymer of p-t-butylstyrene and a C.sub.1 -C.sub.4 alkyl methacrylate, wherein the polymer further comprises sulfur-containing end groups.

Coated carrier particles for electrographic developers

A toner powder composition is provided wherein the toner particles are coated with a metal alkoxide. The product powder displays improved flow characteristics. The coating is accomplished by contacting starting toner particles with a solution of metal alkoxide in a solvent wherein the toner particles are substantially completely insoluble, followed by separation and drying. The metal of the alkoxide has a valence of 3 through 5, and the alkoxy groups contain not more than 10 carbon atoms.

Bound metal alkoxide coated toner particles

The invention provides a method of modifying the triboelectric charging propensity of carrier particles coated with a fluorohydrocarbon polymer or copolymer. The method comprises dehydrofluorinating the polymer or copolymer by contacting the coated particles with a basic solution.

The invention provides a method of modifying the triboelectric charging propensity of carrier particles coated with a fluorohydrocarbon polymer. The method comprises dehydrofluorinating and oxidizing the polymer by contacting the coated particles with a basic solution and a solution of an oxidizing agent. The resulting new particles have less fluorine atoms bonded to the coated polymer and also have oxygen atoms bonded thereto.

A carrier for an electrographic developer composition is provided, comprising on its surface a polymer having at least one repeating unit to which is appended a monovalent chlorendate group containing a carboxylic acid group or a metal salt thereof. The carriers exhibit high negative triboelectric charging characteristics and therefore provide a highly positive developer composition.

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Rochester, NY, United States of America

William E Yoerger