Patent ID: 8564142

Claim:
A radiation curable ink jet ink composition comprising: a monomer equal to or more than 20% by mass and equal to or less than 50% by mass with respect to the total mass of the ink composition, which is represented by the following formula (I); and N-vinylcaprolactam equal to or more than 5% by mass and equal to or less than 15% by mass with respect to the total mass of the ink composition: CH 2 ═CR 1 —COOR 2 —O—CH═CH—R 3 (I) wherein, R 1 is a hydrogen atom or a methyl group, R 2 is a divalent organic residue having 2 to 20 carbon atoms, and R 3 is a hydrogen atom or monovalent organic residue having 1 to 11 carbon atoms.