Patent ID: 8343709

Claim:
A processed pigment in which a pigment is covered with at least one of a specific polymer compound selected from the following (SP-1) to (SP-3): (SP-1) a polymer compound having a heterocycle on a side chain, (SP-2) a graft polymer compound having a weight average molecular weight of from 1,000 to 100000, wherein the graft polymer compound is a copolymer in which monomers including a macromonomer and a monomer having an acidic group are copolymerized, (SP-3) a polymer compound represented by the following formula (3-3), wherein in the formula (3-3), A 2 represents a monovalent organic group containing at least one site selected from an organic dye structure, a heterocyclic structure, an acidic group, a group having a basic nitrogen atom, a urea group, a urethane group, a group having a coordinating oxygen atom, a hydrocarbon group with 4 or more carbon atoms, an alkoxysilyl group, an epoxy group, an isocyanate group, and a hydroxy group, and n A 2 s may be the same or different; R F and R G each represent independently a single bond or a divalent organic linkage group, n R F s may be the same or different and m R G s may be the same or different; R E represents a (m+n)-valent organic linkage group; m represents 1 to 8; n represents 2 to 9; m+n satisfies 3 to 10; and P 2 represents a polymer skeleton and m P 2 s may be the same or different, wherein (i) the processed pigment is produced via a salt milling step of mechanically kneading a mixture containing a pigment, a water-soluble inorganic salt, a small amount of a water-soluble organic solvent which does not substantially dissolve the water-soluble inorganic salt, and the specific polymer compound, (ii) the polymer compound of (SP-1) includes a polymerization unit derived from a monomer represented by formula (1), maleimide or a maleimide derivative: wherein in the formula (1), R 1 represents a hydrogen atom, or a substituted or unsubstituted alkyl group; R 2 represents a single bond, or a divalent linkage group; Y represents —CO—, —C(═O)O—, —CONH—, —OC(═O)—, or a phenylene group; and Z represents a group having a nitrogen-containing heterocycle structure, (iii) a main chain of the graft polymer compound of (SP-2) is polystyrene, polyethylene oxide, polypropylene oxide, poly(meth)acrylic acid ester, polycaprolactone, or polyester.