Patent ID: 7648572

Claim:
A non-aqueous pigment dispersion comprising: a quinacridone pigment, a polymeric dispersant, and a dispersion synergist in a dispersion medium; wherein the dispersion synergist is a diketopyrrolo-pyrrole derivative containing at least one acidic group or a salt thereof; the dispersion synergist is a diketopyrrolo-pyrrole derivative according to Formula (I): wherein R 1 , R 2 , and R 3 are inderendently selected from the group consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a tert.-butyl group, a phenyl group, a cyano group, and an acidic group; R 4 and R 6 are independently selected from the group consisting of hydrogen and a halogen atom; R 5 is independently selected from the grourp consisting of hydrogen, a halogen atom, a methyl group, an ethyl group, a tert.-butyl group, and a cyano group; and one of R 7 and R 8 is a group including at least one acidic group while the other one of R 7 and R 8 represents hydrogen.