JPS6438758A - Thermosetting powdery toner for developing electrostatic charge image - Google Patents

Abstract

PURPOSE:To attain superior physical and chemical durabilities such as heat, water and chemical resistances, scratch resistance and processability by melting and mixing specified epoxy resin, a cross-linking agent, a colorant, an electric charge controller and other necessary additives, grinding the mixture and classifying the resulting powder. CONSTITUTION:Bisphenol A or bisphenol F type epoxy resin having one or more epoxy groups in one molecule, >=40 deg.C m.p., 800-4,000 number average mol.wt. and a solid state at ordinary temp., a cross-linking agent, a colorant, an electric charge controller and other necessary additives are melted and mixed, the mixture is ground and the resulting powder is classified to obtain a powdery toner. When the number average mol.wt. of the epoxy resin is <800, a formed image becomes brittle and has inferior chemical resistance and processability. When the mol.wt. is >=4,000, unsatisfactory hardness causes inferior scratch resistance. When the m.p. is <40 deg.C, it is difficult to put the powdery toner to practical use from the viewpoint of blocking. The cross-linking agent used does not practically react with the epoxy resin during the production and storage of the toner but reacts with the resin under baking conditions to cure the resin. By using the toner, an image satisfying various physical and chemical requirements is obtd.