Patent ID: 8309292

Claim:
A polyester resin for electrostatic image developing toner, comprising two or more polyester blocks, wherein the polyester resin satisfies the following conditions (A) to (C): (A) an ester concentration of the polyester resin is about 0.01 or more and less than about 0.1; (B) a weight average molecular weight of the polyester resin is about 24,000 or more; and (C) a difference in solubility parameter values (SP values) of at least two kinds of the two or more polyester blocks is about 0.1 to about 0.7, and the ester concentration is computed from monomers constituting the block polyester by the following equation (1) M=K/A (1), wherein M represents ester concentration, K represents a number of ester bonds in the polyester resin, and A represents a number of atoms constituting the polymer chain of the polyester resin.