Photoinitiator 907 (2-Methyl-1-[4-(methylthio)phenyl]-2-morpholinopropan-1-one)

PI-907 absorbs primarily at 305 nm (UVB), which is strongly attenuated by glass, pigments, and most UV lamp envelopes. DETX (diethylthioxanthone) absorbs at 380–420 nm where many lamp systems have higher output, then transfers energy to PI-907 through triplet energy transfer, dramatically increasing the effective quantum yield. The PI-907/DETX combination (typically 2:1 ratio) is a classic formulation for offset UV inks and UV flexo coatings where efficiency matters more than migration potential.