Patent ID: 7244538

Claim:
A binder resin for a toner obtained by crosslinking a vinyl polymer (B) satisfying the following requirements (I) to (VI) with a crosslinking agent (A) having an epoxy equivalent of 1,000 to 30,000, said binder resin containing 0.1 to 50% by mass of a gel component, and having a glass transition temperature of 45 to 75° C.: (I) vinyl polymer (B) comprises vinyl polymer (H) and vinyl polymer (L); (II) vinyl polymer (L) comprises vinyl polymer (L1) which has a weight-average molecular weight in the range between 4,000 and 50,000, as measured by gel permeation chromatography (GPC) and contains 0 to 0.02 mol of a functional group selected from OH, COOH, acid anhydride and amino per kg of the resin, and vinyl polymer (L2) which has a weight-average molecular weight in the range between 4,000 and 50,000 and contains 0.05 to 0.65 mol of a functional group selected from OH, COOH, acid anhydride and amino per kg of the resin; (III) vinyl polymer (H) has a weight-average molecular weight in the range between 50,000 and 1,000,000 and contains 0.02 to 0.60 mol of a functional group selected from OH, COOH, acid anhydride and amino per kg of the resin; (IV) the mass ratio of vinyl polymer (L1)/vinyl polymer (L2) is 5/95 to 95/5; (V) the mass ratio of vinyl polymer (H)/vinyl polymer (L) is 5/95 to 40/60; and (VI) the molecular weight and/or the content of the functional group of vinyl polymer (H) is (are) different from those of vinyl polymer (L1) and of vinyl polymer (L2).