New developments of photoinitiators are the base for the further extension of the radiation curing technology. Three different approaches are presented: The optimized combination of a bisacylphosphine oxide photoinitiator with a suitable stabilizer package allows the UV curing of clear coatings with an excellent performance in outdoor use. The design of new oxime ester derivatives allowed the introduction of a new tailor‐made photoinitiator for color filter resists applications that considerably improves the color quality of the color filter. A novel photoinitiator class capable of releasing strong amine bases opens new opportunities for expanding radiation curing into resins types that crosslink by base‐catalyzed processes.

The addition rate constants of five differently substituted benzoyl radicals to butyl acrylate were determined by continuous-wave time-resolved EPR (TR-EPR at X-band (9 GHz) and at W-band (95 GHz)) spectroscopy. Remarkably, the reactivity of the benzoyl radicals, is divided into two domains: One is established at low (<1.25 M) concentrations of butyl acrylate with rate constants in the range of 10 6 mol -1 s -1 . At alkene concentrations above ca. 1.25 M, the addition reaction slows down by ∼1 order of magnitude. This decrease of the reactivity coincides with a dramatic increase of the macroscopic viscosity in the reaction medium.

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