JPS57210345A - Electrophotographic negatively-chargeable liquid developer and developing method using this developer - Google Patents

Abstract

PURPOSE:To obtain a developer capable of forming a printing plate superior in etching resistance and dispersion stability, and high in resolution, by adding a colorant, a polymer such as polyethylene, and a surfactant derived from an organic phosphate to an electrically insulating liquid. CONSTITUTION:An electrically insulating liquid, e.g., n-pentane, chlorinated paraffin, etc., contains (A) a colorant, e.g., carbon black, copper phthalocyanine, etc., (B) at least one of polyethylene, polypropylene, ethylene copolymer, and propylene copolymer, and (C) a phosphate type surfactant represented by formulaIin which R1 is H, 8-30 C alkyl, alkylphenyl, or a group of formula II, R being 8-30 C alkyl or alkylphenyl, n being 0-15; and R<2> is 8-30 C alkylphenyl or a group of formula III, R being 8-30 C alkyl or alkylphenyl, n being 0-15. Use of this developing liquid permits an image part to exhibit high resistance to an etching solvent in an etching step, not to dissolve in this, and said liquid to form a printing plate high in resolution, and good in reproducibility.