DEVELOPING AGENT AND PROCESS FOR PRODUCING THE SAME

摘要

A process for producing a developing agent, characterized in that a binder resin component is dissolved in a supercritical fluid or subcritical fluid and mixed with a colorant component and that the solubility of binder resin component in the supercritical fluid or subcritical fluid is lowered so as to effect precipitation in particulate form of the binder resin component while the colorant component is dispersed inside the binder resin component. In particular, a process for producing a developing agent for static charge development, characterized in that at re-initiation of developing agent producing operation after reduction of the pressure in reaction vessel from A (MPa) to B(MPa) (provided that A>B>critical pressure) ensuing a developing agent production, at least the developing agent materials and the supercritical fluid or subcritical fluid are injected under high pressure into the reaction vessel. In this process for producing a developing agent, high dispersion of the colorant to primary particle level in the developing agent can be accomplished, and there can be obtained a developing agent of narrow particle diameter distribution provided in uniform particulate form. Further, in this process, continuous production without the need to open or close the reaction vessel can be effected, thereby realizing high production efficiency.