Oh Say Can UV?
UV technology gives in-plant print shops an opportunity to offer something different in the form of high-quality coatings, special effects, processing of unusual printing stocks and rapid delivery of express orders. UV coatings, for example, have a number of specific advantages, among them: high gloss levels, excellent protective qualities and a pleasant tactile experience. Sheets are dry and ready for finishing as soon as they arrive in the delivery, with no powdering required.
While conventional offset inks dry or cure through their binding agents oxidizing and being absorbed into the printing stock, in UV printing, specially formulated inks are exposed to ultra-violet (UV) radiation, which causes them to harden instantly on top of the substrate. UV coating produces high levels of gloss or dull coating, vivid color and vibrant detail with superior rub resistance and no post-cure dryback—even on soft, uncoated sheets.
On UV-equipped Heidelberg presses, the delivery typically accommodates a three-lamp UV end-of-press dryer, a cold-air cassette, one DryStar combination IR/hot air dryer and one hot air dryer for optimum flow of the coating and maximum gloss. UV dryer cassettes are placed between the printing units to cure the UV ink before the UV coating is applied.
Even without coating, UV inks cure instantly, greatly simplifying printing on nonabsorbent materials such as plastic films or metalized papers. Products can be finished more rapidly, enabling higher throughput and turnaround, even on two-sided jobs. In-line UV printing is notable for the superior results it achieves on difficult substrates, from uncoated paper and board to foil and especially plastic, including synthetic papers, static cling vinyl and lenticular. UV inks also perform exceptionally well on recycled substrates.
Finally, unlike conventional offset inks, energy-curable UV inks are solvent-free and dry via exposure to high-energy electrical power, a process that generates no byproducts and is free of emissions.