Developer compositions having layer of a pigment on the surface thereof
AssigneeMinnesota Mining and Manufacturing Company
InventorStanley B. Collins
Life of this patent
Estimating the term…
Abstract
A developer composition capable of developing electrostatic images on dielectric surfaces is disclosed. The composition has an electrical conductivity of at least 10.sup.-6 ohm.sup.-1 centimeter.sup.-1 and utilizes a small dimension powdered material as a coating on the essentially smooth surface of individual spheroids of a toner. The composition reduces background coloration on finished copies and eliminates the need to bias the magnetic development roll.
Claims16
A dry composition capable of being attracted to electrostatic image areas on a dielectric surface, said composition having a static electrical conductivity of at least 10.sup.-6 ohm.sup.-1 centimeter.sup.-1 wherein said composition comprises a plurality of discrete spheroids each having an essentially smooth surface and each comprising a thermoplastic organic resin with a magnetically responsive material distributed therein, and from about 1 to 12 .mu.g per square centimeter of surface area of said spheroids of a coating of a first pigment on said smooth surface wherein said first pigment comprises particles each having an arithmetic mean particle size of at least 0.02 micron, a dibutyl phthalate absorption value of at least 150 cubic centimeters per 100 grams of said pigment, and a static electrical conductivity of at least 10.sup.-8 ohm.sup.-1 centimeter.sup.-1.
A dry composition capable of being attracted to electrostatic image areas on a dielectric surface, said composition having a static electrical conductivity of at least 10.sup.-6 ohm.sup.-1 centimeter.sup.-1 wherein said composition comprises a plurality of discrete spheroids each having an essentially smooth surface and each comprising a thermoplastic organic resin with a first magnetically responsive material and a magnetically non-responsive pigment having a static electrical conductivity of at least 10.sup.-4 ohm.sup.-1 centimeter.sup.-1 distributed therein, and from about 15 to 70 .mu.g per square centimeter of surface area of said spheroids of a coating of a second magnetically responsive material having a needle-like structure, a static electrical conductivity of at least 10.sup.-7 ohm.sup.-1 cm.sup.-1, and an arithmetic mean maximum dimension of at least 0.2 micron on said smooth surface.
Dependencies are inferred from the claim text.