Patent ID: 7256222

Claim:
A radiation-curable ink composition comprising a monomer having a polymerizable group selected from the group consisting of an acryloyl group, a methacryloyl group, an allyl group, and a vinyl group, an oil-soluble dye, and from 0.005 to 1% by weight of a storage stabilizer, wherein the oil-soluble dye is dissolved in the ink, wherein the oil-soluble dye has an oxidation potential that is higher than 1.0 V against SCE, and wherein the oil-soluble dye is at least one member selected from dyes represented by the following general formula (I–1): wherein D-N= represents an atomic group necessary such that the compound represented by the general formula (I–1) absorbs light in a visible region and/or in a near infrared region, and D represents a five-membered heterocyclic group represented by the following general formulae (a), (b), (c), (d) or (f); wherein R 5 and R 6 each independently represents a hydrogen atom, an alkyl group, an aryl group or a heterocyclic group; R 1 , R 2 , R 4 , R 7 to R 13 , and R 18 to R 20 each independently represents a hydrogen atom or a substituent group; and R 1 and R 2 , R 1 and R 5 , and R 5 , and R 6 may optionally form a ring by combining with each other; and dyes represented by the following general formula (A-I): wherein X 1 , X 2 , X 3 , and X 4 each independently represents a group selected from —SO-Z, —SO 2 -Z, —SO 2 NR 1 R 2 , —CONR 1 R 2 , —CO 2 R 1 , and a sulfo group; Z represents a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group; R 1 and R 2 each independently represents a hydrogen atom, a substituted or unsubstituted alkyl group, a substituted or unsubstituted cycloalkyl group, a substituted or unsubstituted alkenyl group, a substituted or unsubstituted aralkyl group, a substituted or unsubstituted aryl group, or a substituted or unsubstituted heterocyclic group, provided that R 1 and R 2 do not represent a hydrogen atom at the same time; M represents a hydrogen atom, a metal element, a metal oxide, a metal hydroxide, or a metal halide; Y 1 , Y 2 , Y 3 , and Y 4 each independently represents a hydrogen atom or a monovalent substituent; and a 1 to a 4 and b 1 to b 4 represent the numbers of X 1 to X 4 and Y 1 to Y 4 , respectively and each independently represents an integer of from 0 to 4, provided that the total sum of a 1 to a 4 is 2 or more and 16 or less.