Electrophotographic toner and process for the preparation thereof

摘要

Disclosed are an electrophotographic toner which is a spherical particle comprising a binder resin having encapsulated therein a colorant and has a volume average particle size of from 3 to 12 mu m, the binder resin being a non-crosslinked styrene-acrylic resin having an acid value of from 30 to 120, containing from 5 to 60% by weight of the components having a molecular weight in terms of polystyrene by gel permeation chromatography of 200,000 or more and having a ratio (Mw/Mn) of the weight-average molecular weight Mw to the number-average molecular weight Mn of from 4 to 30; and a process for preparing an electrophotographic toner comprising spherical particles having a volume average grain size of from 3 to 12 mu m, the process comprising mixing a mixture comprising the above-described resin, a colorant, a wax and an organic solvent as essential components with an aqueous medium in the presence of a neutralizer in an amount sufficiently large to render the resin self-emulsifiable to effect phase inversion emulsification, thereby producing particles each comprising a binder resin having encapsulated therein a colorant and a wax in the liquid medium, and separating and drying the particles. The toner obtained by the present invention is improved in the thermal fixing characteristics and the environmental stability of charging, exhibits a wide fixing temperature width at the heated roll fixing and has excellent triboelectricity.