PL-DRK is a liquid photoinitiator compound developed specifically for dark and black inks and coatings. It provides an optimum balance between surface cure and through cure to enable the best possible adhesion in these systems. Because of its optimum viscosity, it can be used in flexo, screen and paste inks without negatively affecting rheology. It is also well suited as a press side additive for the printer. PL-DRK is soluble in most monomers, oligomers and pre-polymers. It is insoluble in H₂O.