PURPOSE: To maintain excellent picture quality for a long time by using a specified polyester resin, magnetic powder, charge controlling agent, and coloring agent and adding a specified amt. of magnetic powder to the toner base material.
CONSTITUTION: The toner base material consists of a polyester resin satisfying Mw/Mn≥20, wherein Mw and Mn is the weight average mol.wt. and number average mol.wt. of the resin, respectively, 0.5-5wt.% magnetic powder to the toner base material, 0.05-1wt.% charge controlling agent, coloring agent, polyolefin. Further, 0.05-2wt.% magnetic powder is added to the toner base material. The polyester resin is used as the essential component of the binder resin. If Mw/Mn<20, large or small toner particles are produced because uniform dispersion of the charge controlling agent in the binder resin is not realized and the specified amt. of charge controlling agent is not incorporated. Thus, the obtd. toner can not be repeatedly used for a long time.
KUMAGAI YUGO
TAN RYOJI
HIGASHIDA OSAMU
OKADA CHIAKI
