Process for preparing new crystal polymorphs of a methyl-substituted benzimidazolone-dioxazine pigment

摘要

Process for phase conversion of a methyl-substituted, benzimidazolone-fused dioxazine pigment of composition C₂₂H₁₂Cl₂N₆O₄ having the formula (1) ;or of an isomer or tautomer thereof, which comprises treating the pigment of formula (1) with certain organic solvents.;In the course of this phase conversion, 4 novel crystal polymorphs are formed which are called phases II, IV, V and VI and are characterized by means of their X-ray powder diagrams.;The novel polymorphs are of low solubility and feature good fastness properties and violet colorations.;The novel crystal polymorphs are suitable for pigmenting coating materials, plastics, printing inks, aqueous or solvent-based pigment preparations, electrophotographic toners and developers, powder coating materials, inks, preferably inkjet inks, and color filters, and for coloring seed.