Abstract: This invention relates to a printing ink for use in ink-jet printing which is cured using ultraviolet radiation. The ink-jet ink has a viscosity of less than 100 mPas at 25° C. and comprises the following components: 20 to 70% by weight of at least one epoxy functional monomer, 2 to 70% by weight of at least one oxetane functional monomer, 0.5 to 40% by weight of at least one hydroxy-containing compound, 0 to 40% by weight of at least one allyl and/or vinyl ether monomer, at least one cationic photoinitiator, and at least one colouring agent, the ink. The ink jet ink formulation provides a balance of the properties of the ink, namely viscosity, flexibility and cure speed.