Fusible electrostatically attractable toner

Claim 1

A toner composition of electrostatically attractable powder particles fusible by the simultaneous application of heat and pressure, said particles having a melt viscosity at 140° C. in the range of 10 5 to 10 6 mPa.s and an average particle size in the range of 1 to 50 μm, said toner composition comprising a colouring substance and an amount exceeding 80% of its total volume of a mixture of: (1) a polyester resin derived from fumaric acid, or from a mixture of fumaric acid and isophthalic acid containing at least 95 mole % of fumaric acid, and a polyol blend of propoxylated bisphenol according to the formula: ##STR4## wherein Y represents an alkylidene group having from 1 to 4 C-atoms, and m and n are integers with the proviso that the average sum of m and n is from 2 to 7, said polyester resin being derived from amounts of acid and polyol such that the number of carboxyl groups to hydroxyl groups is in the ratio of 1.2:1 to 0.8:1, and having a melting point (Tm) not more than 80° C. and a glass transition temperature (Tg) between 30° and 60° C.; (2) a polyester derived from fumaric acid and bisphenol according to the formula: ##STR5## wherein Y represents an alkylidene group having from 1 to 4 C-atoms, and said polyester has a melting point (Tm) between 70° and 130° C. and a glass transition temperature (Tb) between 35° and 60° C.; (3) a sterically-hindered phenol according to the formula: ##STR6## wherein R 1 and R 2 (same or different) each represent an aliphatic group containing from 1 to 20 carbon atoms and X is a substituted alkyl, alkenyl, alkynyl or aryl group, containing as substituent a carboxylic ester, phosphonate ester, phosphate ester, sulfate ester or sulfonate ester group, and n is an integer from 1 to 4; and (4) a pigment for controlling the melt viscosity having a density (g.cm -3 ) larger than 1.8 at 20° C. and an average grain size in the range of 0.1 to 10 μm, wherein the weight ratio of (1) to (2) is in the range of 1/4 to 4/1, the sum of the contents of resins (1)+(2) is at least 57% by volume of the toner particles, the content of (3) is between 0.25 and 18% by volume of the toner particles, and the content of said pigment is between 2.5 and 42% by volume of the toner particles.