Patent ID: 6821697
Filing Date: 2004-11-23
Classification: G03G

Abstract:
A toner for electrostatic image development, comprising at least a binder resin and a colorant, said binder resin being made of a polyester resin, wherein the flow beginning temperature Tfb of the toner, as measured by a constant load extrusion capillary rheometer with a load of 30 kg/cm2, is 90Â° C. or higher and 120Â° C. or lower, the T1/2 temperature exceeds 120Â° C. and is 160Â° C. or lower, and the flow ending temperature Tend is 130Â° C. or higher and 170Â° C. or lower, and wherein said toner has a spherical or generally spherical shape having an average roundness (the average value of roundness is defined by (the perimeter of a circle having the same area as that of a projected area of the particles)/(the perimeter of a projected image of the particles)) of 0.97 or more, wherein said binder resin is a mixture of:(A) a straight-chained polyester resin in which the T1/2 temperature, as measured by the constant load extrusion capillary rheometer, is 80Â° C. or higher and 120Â° C. or lower, and the glass transition temperature Tg is 40Â° C. or higher and 75Â° C. or lower, and (B) a crosslinked polyester resin in which the T1/2 temperature, as measured by the constant load extrusion capillary rheometer, exceeds 120Â° C. and is 210Â° C. or lower, and the glass transition temperature Tg is 40Â° C. or higher and 75Â° C. or lower, and wherein a weight ratio of said resin (A) to said resin (B), (A)/(B), is within a range of 20/80-80/20, and wherein said toner satisfies the relationship: 20Â° C.&lE;T1/2(B)âˆ’T1/2(A)&lE;120Â° C. wherein T1/2(A) and T1/2(B) respectively represent the T1/2 temperature of said resin (A) and said resin (B).