Chapter 5:Photoinitiators for Blue to Red LED Exposures

Several novel photoinitiators applicable to various photopolymerisation reactions (e.g. free-radical photopolymerisation and cationic photopolymerisation) under visible light delivered from light-emitting diodes (LEDs) have been developed in the last 5 years. Based on the specific chemical structures of these photoinitiators, reactive species such as free radicals or cations can be generated through their exposure to blue, green, yellow, or red LEDs and induce photopolymerisation reactions. Specifically, naphthalimide derivatives or metal-based complexes (e.g. ruthenium-, iridium-, copper-, iron-, and zinc-based complexes) have emerged as efficient blue-light-sensitive photoinitiators, while some compounds with large π-conjugated structures demonstrate excellent photoinitiating ability of polymerisation under green to red LEDs. This chapter summarizes the recently emerging LED-sensitive photoinitiators, which demonstrate great potential for application in the fabrication of polymer-based materials under mild conditions.