Abstract: Pigment compositions for oil-based lithographic printing ink systems are provided which comprise as colourant besides an organic pigment an organic dyestuff soluble in an organic solvent (solvent dye). The printing inks prepared from these pigment compositions show outstanding improvements in colour strength combined with improvements in both gloss and transparency of the prints obtained.

Abstract: An organic solvent-based printing ink composition which comprises a cationic dyestuff of the indole class, an organic solvent, an organic acid which preferably is a resin acid, soluble in the organic solvent, and optionally an organic pigment. The cationic dyestuff is formed (in situ) from its carbinol precursor. The compositions show for example high color strength and excellent rheological properties and can be used in publication or packaging gravure flexographic, lithographic or letterpress printing processes.