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Rapid and entire curing of thin films is still a challenge in modern coating industry. Since numerous new applications are developed regularly, formulations have to be adapted to give optimum performance. Selection of type of resin influences macroscopic characteristics of the cured formulation. Mechanical and physical properties such as hardness, toughness or oxygen permeability can be varied in a wide range. Photoinitiators (P1) represent the key component in such formulations. By careful selection a remarkable influence on the curing performance e.g. polymerization rate, double bond conversion, but also final properties such as gel content or color is possible. Most radical generating photoinitiators used are based on the benzoyl chromophore and can be classified into cleavable Type I or hydrogen abstracting Type II 4 The carbonyl group of the chromophore is responsible for light absorption, electronic excitation and cleavage process. The role of the benzoaromatic moiety can be found in adjusting the wavelength of absorption to a suitable range of the UV-spectrum. Furthermore, the aromatic ring is essentially responsible for the stabilization, quenching reaction and addition rates to double bonds of the generated radical. Tuning of various established systems was carried out by extension of the conjugated 6 which leads to an absorption which is shifted to the visible range
of the spectrum. Also the introduction of hetero-substituents e.g. OR, SR or 2 at the aromatic
moiety drastically changed the photophysical and —chemical
