Toner for developing electrostatic images, process for preparing toner for developing electrostatic images, developer for developing electrostatic images and images forming method

A developer for developing electrostatic images, comprising a carrier and a toner for developing electrostatic images, said toner comprising a colorant, a binder resin, and a reactive polymer which cross-links when heated to a temperature that is higher than 100° C., and the toner having a shape factor SF1 of 110 to 140 represented by:

• SF1 =ML2/(4A/Σ×100)
• wherein, ML represents a maximum length (μm) of the toner, and A represents a projected area (μm2) of the toner;
• wherein the toner has a layered-structure containing at least a shell layer provided so as to cover the surface thereof, and a core layer provided on an inner side of the shell layer;
• and
• the binder resin is contained in the core layer and the shell layer, and a glass transition temperature of a binder resin contained in the core layer is lower than a glass transition temperature of a binder resin contained in the shell layer.