Agglomerated pigment, process for producing the same, aqueous pigment dispersion, and water-based ink composition

摘要

An agglomerated pigment comprises (1) an organic pigment compound, (2) either a sulfonated organic pigment compound obtained by incorporating at least one sulfonic group into the organic pigment compound or a sulfonated organic pigment derivative obtained by incorporating at least one sulfonic group into a derivative of the organic pigment compound, (3) univalent inorganic counter ions bonded to sulfonic groups of component (2), and (4) bivalent or higher inorganic counter ions which are bonded to sulfonic groups of component (2) and wherein each such group has an at least univalent positive charge, the surface of the agglomerated organic pigment as a whole being positively charged. An aqueous pigment dispersion and a water-based ink composition both having excellent storage stability, an agglomerated pigment for use as a raw material for the dispersion, and a process for producing the pigment are provided.