On the Post-cure Case (UV Inks)

WHY is ink film thickness such an issue?

The performance of UV inks is impacted, in numerous respects, by the ink film thickness of the ink laid down or amount of ink laid down. Balmer says while gloss can be enhanced by greater ink film thickness, proper depth cure is not so easy with a heavy film weight. The negative impact of a thick ink film is especially noticeable in darker colors, where the pigment absorbs UV light, competing with the photoinitiators, and resulting in under-cure. He concludes, "This in turn may lead to adhesion and rub resistance issues. Furthermore, if a UV lacquer is subsequently applied on top of such a film, this may result in scratch-off of the lacquer."