INFLUENCE OF PIGMENT SIZE ON WET INK GLOSS DEVELOPMENT

The development of wet ink gloss at short times is reported for the fi rst time using actual printing inks and paper coatings. The ink gloss is recorded every 0.1 s after printing and followed for 20 s. The glos s at short times correlates well with the final gloss and the paper-in k interactivity: this result indicates that the leveling of filaments after printing is a critical step to obtain high-gloss prints. Fine pi gment sizes are found to arrest the leveling of filaments formed in th e printing nip. This arresting of leveling produces a lower gloss ink film compared to the unprinted coating surface. One theory that explai ns the results is that ink solvent or vehicle is removed from the ink layer to thicken the remaining ink film. A model is proposed to descri be the surface-tension-driven leveling of ink films while vehicle is b eing removed. The model points out the important properties of inks an d coatings which promote ink film leveling.