Use of aromatic compounds as phase directors and particle size reducers for quinacridone pigments

摘要

The present invention relates to a process for producing alpha, gamma-I, gamma-II and gamma-III crystal modifications of quinacridone and transparent quinacridone pigments including the solid solutions of various quinacridones, using a variety of tris-aryl-s-triazines, particularly resorcinol triazine derivatives, or aromatic- or heteraromatic-compounds having at least one hydroxyl or keto group bonded to the ring, as an additive, prior to or concurrently with the oxidation of corresponding dihydroquinacridone salts.