A
monomer for a shell or a mixture of at least two monomers for a shell was suspension polymerized in the presence of core particles and a
polymerization initiator to obtain
polymer particles, wherein said core particles are formed of a
polymer obtained by
polymerization of a
monomer for a core or a mixture of at least two monomers for a core and containing a colorant, wherein said
monomer for a shell or mixture of monomers for a shell is one which gives upon
polymerization a
polymer having a
glass transition temperature higher than that of the polymer forming the
core particle, and wherein said polymerization initiator is represented by the following formula 1: wherein X1, X2, X3 and X4 independently represent
oxygen atom,
sulfur atom, >NR (wherein R is
hydrogen atom,
alkyl group, or group); R1, R2, R3, R4, R5 and R6 independently represent
alkyl group,
aryl group, or
alkyl or
aryl group having at least one
substituent which is -OR, -OH, -NHR, or -NR2(wherein R is alkyl group or
aryl group), and n and m independently represent an integer of 1 to 10. An outer additive was applied on the
polymer particle to obtain a polymerized toner. This polymerized toner has low fixing temperature, excellent overhead
projector transparency, good shelf stability, and exhibiting a less pronounced reduction in
electric charge under conditions of
high humidity and high temperature.