Highly versatile, solid photoinitiator that has good solubility in UV monomers. It provides low yellowing and good surface cure when used at 0.5-5 wt% in UV curable formulations. 184 shows similar reactivity to 1173 and both are widely used in high quality coatings and varnishes. 184 can be combined with other photoinitiators in thick films to overcome oxygen inhibition.