Process for preparing positive electrostatic liquid developers with acidified charge directors

Abstract

A process for preparing an improved positive-working electrostatic liquid developer comprising (A) dispersing at an elevated temperature in a vessel a thermoplastic resin and a nonpolar liquid having a Kauri-butanol value of less than 30, while maintaining the temperature in the vessel at a temperature sufficient to plasticize and liquify the resin and below that at which the nonpolar liquid degrades and the resin decomposes, (B) cooling the dispersion, either (1) without stirring to form a gel or solid mass, followed by shredding the gel or solid mass and grinding by means of particulate media; (2) with stirring to form a viscous mixture and grinding by means of particulate media; or (3) while grinding by means of particulate media to prevent the formation of a gel or solid mass; (C) separating the dispersion of toner particles having an average particle size of less than 30 .mu.m from the particulate media, and (D) adding to the dispersion subsequent to Step (A) a nonpolar liquid soluble ionic or zwitterionic charge director compound mixed with an acid having a pKa of <4.2 and a solubility of at least 0.5% based on the weight of charge director compound in the mixture of nonpolar liquid and charge director compound. Optionally a colorant and an adjuvant may be added. The electrostatic liquid developer prepared using the process of the invention is useful in copying, making proofs, including digital color proofs; lithographic printing plates, and resists.

Dependencies are inferred from the claim text.