Oblon, Spivak, McClelland, Maier & Neustadt, P.C.
Electrophotographic toner
Disclosed is an electrophotographic toner using a polyester resin as a binder and a highly dispersed pigment colorant. The toner gives a high quality image excellent in transparency and chroma (brightness, gloss) and exhibits excellent powder fluidity, anti-offset property, charge stability and transferability.The toner is obtained by dispersing an oil dispersion, containing an isocyanate group-containing polyester prepolymer dissolved in an organic solvent, a pigment colorant dispersed therein and a releasing agent dissolved or dispersed therein, in an aqueous medium in the presence of inorganic fine particles and/or polymer fine particles, reacting the prepolymer in the dispersion with a polyamine and/or a monoamine containing an active hydrogen-containing group to form an urea-modified polyester resin having an urea group, and by removing the liquid medium from the dispersion containing the urea-modified polyester resin, and is characterized in that the pigment colorant contained in the toner has a dispersion diameter, in terms of a number average diameter, of 0.5 &mgr;m or less and in that particles of the pigment colorant having a diameter of 0.7 &mgr;m or more account for 5% by number or 30 less.
Ricoh Company, Ltd.
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Masami Shigeru Tsunemi Hiroshi
Tomita Emoto Sugiyama Yamashita