UV coating initiator were triggered after ultraviolet radiation light initiator , produce free radicals or ions, these free radicals or ion get cross-link reaction with pre polymers or double bonds of unsaturated monomers , form a monomer gene, resulting in polymerization, cross-linking and grafting reactions, so that make the resin (UV coating, printing ink, adhesive, etc.) in seconds (range) from the liquid into solid. This process is called "UV light curing".  Since then, a complete photocuring process is completed.