Photopolymerization process and composition employing a charge transfer complex and cationic photoinitiator

A photopolymerization process comprising the steps of:

• a) providing a radiation curable coating composition comprising a charge transfer complex and effective amount of cationic photoinitiator, the charge transfer complex comprising at least one electron withdrawing reactant component and at least one electron donating reactant component free radically reactive therewith, the electron withdrawing reactant component comprising an unsaturated nitrogen containing compound and the electron donating reactant component comprising an unsaturated compound having at least one vinyl ether group, the electron donating reactant component at least one of separate from or structurally incorporated within the at least one electron withdrawing reactant component;
• b) applying the radiation curable coating composition to a substrate to be coating;
• and
• c) subjecting the applied radiation curable coating composition to ultraviolet light for a period of time sufficient to polymerize the charge transfer complex.

A radiation curable coating composition comprising:

• a) an unsaturated nitrogen containing polyester component having at least one group attached thereto selected from the group consisting of maleate, fumarate, itaconate, citraconate and mesaconate;
• b) a non-polymerized, co-curable vinyl ether component at least one of separate from said unsaturated polyester component or structurally incorporated in said unsaturated polyester component and free radically reactive therewith;
• c) a cationic photoinitiator;
• and
• d) a free radical photoinitiator.