Design of New 3-Ketocoumarins for UV LED Curing
Marika Moronea, IGM Resins
Abstract: Light emitting diodes (LED) are becoming a valid alternative to Hg lamps in most radiation curable applications. Matching photoinitiator absorbance with the operational wavelength of the LED source is crucial. In this paper, we will described how it is possible to modify the physical-chemical properties of the 3-ketocoumarins and how such modifications influence the reactivity. Starting from this screening, we will able to design new 3-ketocoumarines with good solubility, high reactivity and low yellowing for clear and pigmented coatings. These new molecules were always compared to thioxanthones and acylphosphine oxides, which are the only two classes of photoinitiators that show good performances at 395 nm  (the most powerful operation wavelength for LED).