Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: 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.

Abstract: Electrophotographic papers comprising electrically conducting paper supports and photoconductive insulating compositions in the form of organic photoconductive dispersions are described. Particles of certain polyphenyl organic photoconductors with para-linked phenyl groups, or polyarylated unsaturated organic photoconductors are dispersed in cellulose nitrate to provide useful photoconductive insulating dispersions.

Abstract: Photoconductive insulating compositions comprising organic photoconductors are described. Organic photoconductor materials such as p-terphenyl or polyvinylcarbazole are dispersed or dissolved in an electrically insulating binder and chemically sensitized with a polymer having repeating units to which are appended a monovalent chlorendate radical. When employing the aforesaid polymeric chemical sensitizer, acrylic polymers or cellulose nitrates are especially useful as insulating binders for heterogeneous compositions of the subject type. Or, by omitting conventional binders, the described polymeric chemical sensitizer can function simultaneously as chemical sensitizer and insulating binder for such photoconductive compositions. Further, the present polymeric chemical sensitizer is particularly useful with one or more additional chemical sensitizers to yield sensitized compositions with especially desirable properties.

Abstract: Co-crystalline organic photoconductor compositions comprising p-terphenyl doped with 1 to 15 percent of p-quaterphenyl useful for electrophotographic elements.

Abstract: Photoconductive insulating compositions in the form of organic photoconductive dispersions are described. Particles of organic photoconductor such as p-terphenyl are dispersed in cellulose nitrate and chemically sensitized with .pi.-deficient N-heteroaromatic compounds such as quinoxalines to provide useful heterogeneous photoconductive insulating dispersions. Such dispersions can be applied to an electrically conducting support to prepare electrophotographic elements.

Abstract: Photoconductive insulating compositions in the form of organic photoconductive dispersions are described. Particles of organic photoconductor such as p-terphenyl are dispersed in cellulose nitrate and chemically sensitized with monomeric hexachlorocyclopentenes to provide useful heterogeneous photoconductive insulating dispersions. Such dispersions can be applied to an electrically conducting support to prepare electrophotographic elements.

Abstract: The present invention relates to a hydrophobic overcoat for an electrophotographic element. The overcoat contains a polymeric composition such as a homopolymer, copolymer, or blend thereof and an .alpha.,.beta.-ethylenically unsaturated carboxylic acid or the partial alkyl ester thereof and a relatively large amount of cross-linking agent for said polymeric composition, for example, an imine-terminated cross-linking agent or a melamine-formaldehyde resin.

Abstract: A repellent composition containing an oil of low volatility having a surface energy less than 27 dynes/cm. and a solid fluorinated polymer such as a polymer of a fluoroalkyl acrylate. In accord with certain embodiments of the invention, a resinous binder and/or a particulate fluorocarbon powder may be added to the repellent composition. The repellent composition may be used to prepare an ink repellent surface for a "waterless" lithoplate or as a coating on the surface of an electrographic element from which a liquid developed electrographic image is transferred.