PURPOSE: To obtain the developer which is excellent in fixability and is balanced in fixing and offsetting by using a polyester resin satisfying specific conditions as a binder in developer particles.
CONSTITUTION: The polyester resin as the binder in the developer particles satisfies the following conditions (A) to (C): (A) AV is required to be within the range of 20 to 35 (KOHmg/g) and AV/OHV=1.0 to 1.5 when the acid value of the resin is designated as AV and the hydroxyl value as OHV, (B) the tetrahydrofurane-insoluble component is required to be ≤10%; further, (C) the ratio of the weight average mol. wt. Mw and number average mol. wt. Mn in the mol. wt. distribution of the tetrahydrofurane-soluble component is ≥10 Mw/Mn, and the above-mentioned distribution has a peak in the region of 3000 to 8000 number average mol. wt. and has a peak or shoulder in the region of 100000 to 600000 number average mol. wt.; in addition, the high-polymer side peak exists at 5 to 15%. The developer which is excellent in fixability and is balanced in the fixing and offsetting is obtd. in this way.
NISHI KOJI
SAKAGUCHI KAZUHIKO
NODA KENJI
