PURPOSE: To secure the long-run property of a developer without deteriorating the productivity of the developer to a large extent by specifying the main component of the binding resin of a toner.
CONSTITUTION: A carrier is admixed with inorganic particles so as to attach the inorganic particles to the surface of the carrier and then a toner is electrostatically mixed and attached to the carrier surface. In this case, the main component of the binding resin of the toner is a polyester resin prepared by condensation copolymerization of a diol component expressed by formula I, a diol component expressed by formula II, a divalent carboxylic acid or its acid anhydride or its lower alkylester, and a polyvalent carboxylic acid having a valence of three or more or its acid anhydride or its lower alkylester, the former diol component being less than 10mol.%, the latter being 10mol.% or more and less than 25mol.%, and the polyvalent carboxylic acid being 2.5mol.% or more and less than 15mol.% of all the components. In the formulae, R is ethylene or a propylene group, (x) and (y) are each an integer of one or more, the average value of [x+y] is 2 to 7 and (n) is an integer of 2 to 6.
YOSHIMURA KANJI
MARUTA MASAYUKI
