Ink jet inks containing nanoparticles of organic pigments

Abstract

A process for making ink jet inks, comprising the steps of: (A) providing an organic pigment dispersion containing a pigment, a carrier for the pigment and a dispersant; (B) mixing the pigment dispersion with rigid milling media having an average particle size less than 100 .mu.m; (C) introducing the mixture of step (B) into a high speed mill; (D) milling the mixture from step (C) until a pigment particle size distribution is obtained wherein 90% by weight of the pigment particles have a size less than 100 nanometers (nm); (E) separating the milling media from the mixture milled in step (D); and (F) diluting the mixture from step (E) to obtain an ink jet ink having a pigment concentration suitable for ink jet printers.

Dependencies are inferred from the claim text.