A polyester resin for a full color toner which comprises a) from 0.5 to 5% by mole, based on all the acid components, of a tribasic or higher carboxylic acid component and/or a trihydric or higher alcohol component, b) at least 95% by mole, based on all the acid components, of a dibasic carboxylic acid component, c) from 10 to 80% by mole, based on all the acid components, of an aromatic diol component consisting of or containing a bisphenol A derivative having ethylene oxide added thereto, and d) from 20 to 110% by mole, based on all the acid components, of an aliphatic diol component; and has a softening temperature of 95 to 115.degree. C., a glass transition temperature of 50 to 70.degree. C., an acid value of 6 to 20 mgKOH/g, a melt viscosity at 118.degree. C. of 1000 to 52,000 poises, a ratio of weight average molecular weight (Mw) to number average molecular weight (Mn) of 1.5 to 5 in the molecular weight distribution determined by gel permeation chromatography, a peak TOP molecular weight of 20,000 or less and a gel fraction of 0.5% by weight or less.
The present invention relates to polyester resin for toner used for developing an electrostatic latent image such as a statically charged image in the electrostatic printing process and discloses polyester resin for toner comprising aromatic dicarboxylic acid, trivalent or higher carboxylic acid, aliphatic diol, bisphenol A derivative aromatic diol, and trihydric or higher alcohol, characterized in that the amount of the aromatic diol of bisphenol A derivative having the mole number of ethylene oxide and/or propylene oxide of 2mole is equal to or more than 85weight % in the entire aromatic diol of bisphenol A derivative, and the amount of the aromatic diol of bisphenol A derivative having the mole number of ethylene oxide or propylene oxide of 1mole is less than 0.2weight % in the entire aromatic diol of bisphenol A derivative.
A process for preparing ground resin particles is provided by modifying a jet mill with opposed fluidized bed. By using a jet mill having a plurality of jet nozzles disposed at predetermined positions in a barrel of a grinding chamber toward the injection point of the grinding chamber and a bottom wall having a flat surface in part or in whole, parallel to the jet nozzles, or having a conical projection immediately below the injection point, resin particles to be ground are jetted with or without water, thereby being ground to obtain ground resin particles of an intended particle size.
A two-component developer is formed as a mixture of a negatively chargeable toner and a resin-coated carrier. The toner comprises at least a binder resin, a colorant and an organic metal compound. The organic metal compound is an organic zirconium compound having a coordination or/and a bonding of zirconium and an aromatic compound as a ligand or/and an acid source selected from the group consisting of aromatic diols, aromatic hydroxycarboxylic acids, aromatic monocarboxylic acids, and aromatic polycarboxylic acids. The toner further includes an external additive comprising hydrophobized inorganic fine powder having an average primary particle size of 0.001-0.2 .mu.m. The resin-coated carrier has a 50%-particle size of 20-70 .mu.m.
A toner for electrophotography comprising a resin binder comprising a polyester resin, as a main component, obtained by polycondensing an alcohol component with a carboxylic acid component, wherein the alcohol component comprises an alkylene oxide adduct of bisphenol A represented by the formula (I): ##STR1## wherein R is an alkylene group having 2 or 3 carbon atoms; x and y are positive numbers showing an average molar number of an added oxyalkylene group, wherein a sum of x and y is from 1.5 to 10, in an amount of 60% by mol or more of the alcohol component, and wherein the carboxylic acid component comprises a tricarboxylic acid compound, wherein a number-average molecular weight of the polyester resin is 1,000 to 8,000; and a coloring agent, wherein an alkylene oxide adduct of bisphenol A of which addition molar number is 3 or more is not present in the polyester resin, or remains in an amount of less than 1.0% by weight.
