Kao Corporation

Eizi Morimoto

Kuniyasu Kawabe

Katsutoshi Aoki

Hiroyuki Kawaji

Tetsuhiro Semura

Tetuhiro Semura

Ken-ichi Suenaga

The toner for electrophotography contains a binder resin, wherein the binder resin has a condensation polymerization-type resin for forming a matrix and an addition polymerization-type resin for forming a dispersed domain. The dispersed domain with a cross-sectional diameter of not more than 2 .mu.m has an areal proportion of not less than 90%, based on the total cross-sectional area of the dispersed domain. This toner is stable, which is capable of maintaining a suitable tribo electric charge, thereby providing a high image quality in which the formed images do not undergo deterioration even under severe environmental conditions. Moreover, in a fixing method using a heat roller; fixing at a low temperature can be performed without using an offset inhibiting liquid.

Process for producing a toner for electrophotography

The method of producing a binder resin has the steps of blending in advance (a) a starting material monomer mixture for two polymerization reaction types, (b) a compound which can react with both of starting material monomers for the two polymerization reaction types, and (c) a tricarboxylic or higher polycarboxylic acid or a derivative thereof, the two polymerization reaction types having independent reaction paths to each other in one reaction vessel; and concurrently carrying out the two polymerization reactions in one reaction vessel to give the binder resin. According to the present invention, the binder resin which has an excellent environmental stability in the tribo electric charge and the image quality, and also has good pulverizability and transparency can be produced. Moreover, in a fixing method using a heat roller, fixing at a low temperature can be performed without using an offset inhibiting liquid. By using such a binder resin, a toner for electrophotography and a developer having excellent performance can be obtained.

Method for producing binder resin and toner for electrophotography using

A developer composition for electrophotography comprising a binding resin and a colorant, said binding resin comprising a specified nonlinear first polyester and a specified linear second polyester, the weight ratio of the first polyester to the second polyester being (80:20) to (20:80), is disclosed. The developer composition of the present invention is excellent in hot offset resistance, low temperature fixation, smoothness and transparency of fixed face, and blocking resistance.

Developer composition for electrophotography

A developer composition for electrophotography comprising a binding resin and a colorant, said binding resin comprising a first linear polyester having a softening point, Tsp, in the range of from 105.degree. C. to 170.degree. C. exclusive, and a second linear polyester having a softening point, Tsp, in the range of from 80.degree. C. to 105.degree. C. exclusive and lower than that of the first linear polyester by at least 10.degree. C., the weight ratio of the first linear polyester to the second linear polyester being (80:20) to (20:80) is disclosed. The developer composition of the present invention is excellent in the hot offset resistance, low temperature fixation, smoothness of fixed face, blocking resistance and transparency.

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Wakayama, Japan

Eizi Morimoto