Advances of Near Infrared Sensitized Radical and Cationic Photopolymerization: from Graphic Industry to Traditional Coatings

Abstract

This contribution summarizes recent progress in the field of near-infrared (NIR) initiated photopolymerization. The photoinitiator system consists of a cyanine as sensitizer (Sens) and an iodonium salt with distinct structural pattern of both the cation and anion as radical initiator. Both, photonic and thermal events are discussed as the main source for formation of initiating species. Electron transfer between the excited state of Sens (Sens*) and the iodonium salt can be seen as the main source for formation of initiating species such as radicals and protons/electrophiles. Furthermore, the ion mobility as probed by the electric conductivity possesses a major function to tune the reactivity of the photopolymer system. The reactivity of these systems was studied in different applications such as Computer to Plate (CtP), LED curing, photonic baking, and curing of powder coatings with NIR lasers exhibiting line shape focus.