Charge control agent and toner for electrostatic image development

An image formation process of eletrophotography comprising the steps of:

• developing an electrostatic latent image on an electrostatic latent image frame by a developer including a toner, said toner comprising a resin for the toner and a charge control agent comprising aggregate particles of an azo-type iron complex salt represented by the following chemical formula [I]
• wherein R1−, R2−, R3−, and R4− are the same or different and selected from the group consisting of a hydrogen atom, an alkyl group having a straight or branched chain of 1 to 18 carbon atoms, an alkenyl group having a straight to branched chain of 2 to 18 carbon atoms, a sulfonamide group being to have substitutional groups, a mesyl group, a hydroxyl group, an alkoxyl group of 1 to 18 carbon atoms, an acetylamino group, a benzoylamino group, a halogen atom, a nitro group and an aryl group being to have substitutional groups;
• R5− is a hydrogen atom, an alkyl group having a straight or branched chain of 1 to 18 carbon atoms, a hydroxyl group or an alkoxyl group of 1 to 18 carbon atoms;
• R6− is a hydrogen atom, an alkyl group having a straight or branched chain of 1 to 18 carbon atoms, a hydroxyl, group, a carboxyl group, a halogen atom, or an alkoxyl group of 1 to 18 carbon atoms;
• and n is 0.7 to 0.99,
• that said aggregate particles have an average size of 1 to 4 microns and an average particle size of a primary particulate crystalline, that is formed by fining the aggregate particles with ultrasonic irradiation, is at most 3 microns.