Developer for electrophotography and process for preparation thereof
AssigneeMita Industrial Co., Ltd.
InventorsToshihiro Kouchi, Tatsuo Aizawa
Life of this patent
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Abstract
A particulate composite developer for electrophotography is disclosed, which has a novel dispersion structure comprising a continuous phase consisting of a homogeneous mixture of a resin and a pigment and a dispersed phase consisting of spherical particles of a soft parting or fixing material having an emulsion grade size and being dispersed in the continuous phase. This particulate developer has in combination improved adaptability to the developing operation, excellent transferring and cleaning properties, good ability to form a sharp image free of fog and good fixing property not causing an offset phenomenon.
Claims12
A process for the preparation of developers for electrophotography, which comprises (a) preparing an emulsion of a soft parting or fixing material insoluble in cold toluene but soluble in hot toluene and having a penetration of 1 to 50 as measured at 25.degree. C. by dissolving said soft parting or fixing material in toluene at a temperature higher than 65.degree. C. and cooling the resulting solution to precipitate said soft parting or fixing material in the form of emulsion particles having a substantially spherical shape and a particle size not larger than 10.mu., (b) mixing said emulsion with a hard resin soluble in cold toluene and at least one pigment selected from the group consisting of coloring pigments, extender pigments, magnetic pigments and electrically conductive pigments to form a composition for spraying which comprises the emulsion particles and pigment dispersed in the hard resin solution, said parting or fixing material and said hard resin being present at a weight ratio of 95:5 to 55:45, and then (c) spraying said composition into a drying atmosphere to form developer particles having a dispersion structure of a continuous phase of a homogeneous mixture of the hard resin and at least one pigment and a plurality of dispersed phases of the substantially spherical particles of the soft parting or fixing material.
A process for the preparation of developers for electrophotography, which comprises (a) preparing a hot dispersion-solution by (i) dissolving a soft parting or fixing material insoluble in cold toluene but soluble in hot toluene and having a penetration of 1 to 50 as measured at 25.degree. C. and a hard resin soluble in cold toluene in toluene-containing solvent at a temperature higher than 65.degree. C. and by (ii) dispersing at least one pigment selected from the group consisting of coloring pigments, extender pigments, magnetic pigments and electrically conductive pigments in the resulting solution, said parting or fixing material and said hard resin being present at a weight ratio of 95:5 to 55:45, (b) cooling the resulting hot dispersion-solution to precipitate said soft parting or fixing material in the form of emulsion particles having a substantially spherical shape and a particle size not larger than 10.mu., and to form a composition for spraying which comprises the emulsion particles and pigment dispersed in the hard resin solution, and then (c) spraying said composition into a drying atmosphere to form developer particles having a dispersion structure of a continuous phase of the hard resin and at least one pigment and a plurality of dispersed phases of the substantially spherical particles of the soft parting or fixing material.
Dependencies are inferred from the claim text.