The cations and radicals produced in aminothiazonaphthalic anhydride derivatives (ATNAs) combined with an iodonium salt, N-vinylcarbazole, amine, or chloro triazine initiate the ring-opening cationic polymerization of epoxides and the free radical polymerization of acrylates under LEDs at 405 or 455 nm. The photoinitiating ability of these novel photoinitiating systems is higher than that of the well-known camphor-quinone-based systems. An example of the high reactivity of the new proposed photoinitiator is also provided in resins for 3D-printing using a LED projector@405 nm. The chemical mechanisms are investigated by steady-state photolysis, cyclic voltammetry, fluorescence, laser flash photolysis, and electron spin resonance spin-trapping techniques. (C) 2015 Wiley Periodicals, Inc.