Im nahen Infrarot durchlaessige schwarze Azo-Pigmente

摘要

Near-infrared transmitting black azo pigments are represented by the following formula (1) and have a crystalline form selected from the group consisting of a thin, long crystalline form and a leaf-shaped crystalline form. wherein R represents at least one group selected from the group consisting of lower alkyl groups having 1 to 3 carbon atoms and lower alkoxy groups having 1 to 3 carbon atoms, n stands for an integer of from 1 to 5, and, when n is other than 1, Rs may be the same or different. These near-infrared transmitting black azo pigments can be produced by treating the corresponding black azo pigments of the formula (1) with an alkali in an alcohol. Near-infrared transmitting black azo pigments compositions each comprises one or more of the near-infrared transmitting black azo pigments and a near-infrared transmitting material as a vehicle.