Photoinitiators are additives which use energy from ultraviolet or visible light to induce polymerisation, or to cure, as the case of in coatings and inks; that is, they are used to dry a coating through the application of light rather than heat. An ink or coating containing a photoinitiator can dry in less than a second under a UV light.

UV curing results in several benefits to the customer. In the first place, these coatings and inks are virtually solvent-free; they emit no volatile materials when they dry. UV curing uses less energy than conventional curing, and the resulting coatings have high gloss and scratch resistance.