Ink-Releasing Mechanism of Waterless Offset Printing Plate

This study investigates the two possible mechanisms of ink refusal by the non-image area of waterless offset printing, i.e. the formation of a weak fluid boundary layer on top of the non-image area and the softening of the non-image area after contacting with ink. FTIR-ATR, Micro-Indentation, AFM and a Deltack Printability Tester were used to analyze the plate surface before and after the plate-ink contact. This study shows that the dominant ink refusal mechanism is the softening of the non-image area caused by the diffusion of certain components in ink diluents into the polymeric layer of this area. The formation of a weak fluid boundary layer is also likely to contribute to ink refusal and may play a synergistic role.