Patent ID: 8084091

Claim:
A non-aqueous pigment dispersion comprising: a quinacridone pigment, a polymeric dispersant, and a dispersion synergist in a non-aqueous dispersion medium; wherein the dispersion synergist is a quinacridone derivative substituted on one of the two nitrogen atoms of the quinacridone basic chromophore structure by a group including at least one carboxyl group or a salt thereof; the at least one carboxyl group or a salt thereof is attached directly to the quinacridone basic chromophore structure or through a linking group containing 1 to 20 carbon atoms; and if the at least one carboxyl group or a salt thereof is attached to the quinacridone basic chromophore structure through the linking group, the linking group is a straight chain of 1 or more carbon atoms, wherein some of the carbon atoms may be substituted by a heteroatom selected from the group consisting of an oxygen atom, a nitrogen atom, a phosphorous atom, a selenium atom, and a tellurium atom.