Patent ID: 7846992

Claim:
A pigment dispersion comprising: a color pigment; and a polymeric dispersant having at least one pending chromophore group covalently bound to a polymeric backbone of the polymeric dispersant through a linking group; wherein the color pigment is selected from the group consisting of monoazo pigments, disazo pigments, β-naphtol pigments, naphtol AS pigments, azo pigment lakes, benzimidazolone pigments, disazo condensation pigments, metal complex pigments, isoindolinone pigments, isoindolinine pigments, phthalocyanine pigments, quinacridone pigments, diketopyrrolo-pyrrole pigments, thioindigo pigments, anthraquinone pigments, anthrapyrimidine pigments, indanthrone pigments, flavanthrone pigments, pyranthrone pigments, anthanthrone pigments, isoviolanthrone pigments, aluminium pigment lakes, dioxazine pigments, triarylcarbonium pigments, and quinophthalone pigments; the at least one pending chromophore group has a molecular weight which is smaller than 85% of the molecular weight of the color pigment; the at least one pending chromophore group is a chromophore group occurring as a side group on the polymeric backbone and not a group in the polymeric backbone itself or occurring solely as an end group of the polymeric backbone; the linking group consists of all the atoms between the polymeric backbone and a first atom of the aromatic group by which the pending chromophore group is linked to the polymeric backbone; and the at least one pending chromophore group has a similarity coefficient SIM of at least 0.75, with the similarity coefficient defined by: SIM = t · C M + P - C wherein M represents the number of atoms in the at least one pending chromophore group; P represents the number of atoms in the color pigment; C represents the largest number of atoms in common between the at least one pending chromophore group and the color pigment as one continuous structure; and t is an integer representing the number of times that the largest number of atoms in common C fits into the organic color pigment, without using atoms of the color pigment twice.