Quinacridone pigments

This chapter surveys the structural and synthetic chemistry and the industrial applications of quinacridones, a small but extremely important group of high-performance carbonyl (or polycyclic) organic pigments. They are based on one of the most important new chromophoric systems developed specifically for pigment applications after the introduction of the phthalocyanines, and currently occupy a prominent position in the red to violet shade areas. A historical perspective on the discovery and commercial development of the quinacridones is presented initially. There then follows an illustrated discussion of the structural chemistry of the pigments, encompassing both molecular and crystal structures. Throughout the chapter, specific features of their molecular structures and the nature of the intermolecular association within the crystals are related to their influence on the color and technical performance in application, in which they exhibit some of the highest standards of heat stability, solvent resistance, and fastness to light and weather encountered in organic pigments. Finally, a survey of the principal current applications of the specific individual commercial quinacridone pigments is presented.