PROCESS FOR PRODUCING TONER FOR DEVELOPING ELECTROSTATICALLY CHARGED IMAGES

摘要

A process for producing a toner for developing electrostatically charged images which comprises suspension-polymerizing a monomer composition at least comprising a polymerizable monomer and a colorant in an aqueous dispersion medium containing a dispersant to form colored polymer particles, characterized by comprising the following two steps: (1) the first step of forming colored polymer particles as the core component by suspension-polymerizing a monomer composition for the core component comprising at least one core-forming monomer giving a polymer having a glass transition temperature of 80 DEG C or below and a colorant in an aqueous dispersion medium until the conversion of the monomer into polymer reaches 80 % or above, and (2) the second step of forming a polymer layer as the shell on the surface of each colored polymer particle as the core component by adding at least one shell-forming monomer giving a polymer having a glass transition temperature higher than that of the polymer forming the core or a shell-forming monomer composition containing such a monomer and a water-soluble radical polymerization initiator to the reaction system containing the colored polymer particles as the core component and subjecting the obtained mixture to polymerization, and thereby producing encapsulated colored polymer particles having a core-shell structure comprising 40 to 99 wt% of the core component and 1 to 60 wt% of the shell component. The toner thus produced has a low fixing temperature, a good transparency of the images formed on an OHP film, and an excellent shelf stability.