Abstract: A radiation-curable ink composition contains (A) aminoacrylate at 1 mass % to 10 mass %, inclusive, (B) phenoxyethyl acrylate at 20 mass % to 50 mass %, inclusive, and (C) tetraethylene glycol diacrylate at 1 mass % to 20 mass %, inclusive, in its reaction component, as well as (E) bis(2,4,6-trimethylbenzoyl)-phenylphosphine oxide at 3 parts by mass to 8 parts by mass, inclusive, (F) 2,4,6-trimethylbenzoyl-diphenyl-phosphine oxide at 3 parts by mass to 5 parts by mass, inclusive, in 100 parts by mass of the reaction component, and (G) diethylthioxanthone at 1 part by mass to 3 parts by mass, inclusive, in 100 parts by mass of the reaction component.

Abstract: A radiation-curable ink composition includes an acrylate monomer of which homopolymer has a glass transition temperature of not higher than 0° C. in an amount of 20% by mass or more and 65% by mass or less based on the total amount of reaction components; a monofunctional acrylate having an alicyclic structure; and a multifunctional acrylate having an alicyclic structure.

Abstract: A photocurable ink composition includes (A) a polymerizable compound, (B) an acylphosphine oxide-based photopolymerization initiator, and (C) at least one compound selected from a hindered amine-based compound with a mass-average molecular weight of 2000 to 4000 and a hydroxyphenyltriazine-based compound of formula (1): (wherein R1, R2, and R3 each independently represent an organic group). The proportion of the component (C) is in the range of 0.2% by mass to 2.0% by mass.

Abstract: Provided are a radiation-curable ink composition including phenoxyethyl acrylate (A) in an amount of from 20 to 55 mass % of the total reaction components, a multifunctional acrylate (B) in an amount of from 20 to 50 mass % of the total reaction components, and a black pigment (F1); and a radiation-curable ink composition including phenoxyethyl acrylate (A) in an amount of from 20 to 55 mass % of the total reaction components, a multifunctional acrylate (B) in an amount of from 10 to 50 mass % of the total reaction components, and a yellow pigment (F2).