Coatings can provide the visual appeal, lasting durability, protection, and rub-resistant finish that customers have come to expect from the printed medium – especially for end uses such as direct mail and frequent handling. Print firms are constantly trying to control coating costs and, ideally, bring outsourced services such as ultraviolet (UV) coating in house to increase profit margins.
Attendees at GRAPH EXPO last September saw one coating innovation, as Scodix unveiled the 1200 UV, a press that applies clear polymer on selective areas with variable densities and gloss levels. Employing 99 glossing units, the device creates the highest gloss available for printed materials: up to 70 microns in polymer height – which is 10 times higher than spot varnish. Gloss density can be set to variable capabilities, from 1 percent to 100 percent, allowing for easy single- or dual-sided printing. (Printed substrates are run under a UV bulb for instantaneous curing.) “Turning printing into an experience is the only way to survive theses days,” president Dror Danai said at the firm’s first-ever press conference.
Tom O’Brien and Lindsay Gray, co-owners of commercial printer Acculink, Greenville, NC, are believers. The pair bought a Scodix 1200 UV press at the show. “There just isn’t any other piece of equipment that can do what it does,” O’Brien told the official Show Daily publication. Not only is Acculink offering the special-effects printing to its own customers, but the QP Top 100 printer also plans to outsource the unique service to other printing companies.
Digital press OEMs with perhaps more familiar names chime in on the coating topic, too. HP offers its own near-line unit, called the Indigo UV coater, to protect its liquid ElectroInk output. For offline, near-line, and inline coating, Xerox contends that wetting performance is key for its toner-based prints. It recommends storing iGen 3/4 printed output for at least 30 minutes before offline coating but added that running fluids that are “qualified/developed for inline use with Xerox digital presses can eliminate this duration,” in its Finishing Hints and Tips Guide. “Most commercially available fluids are not optimized for proper wetting. They may also interact with the fuser agent on the sheets, causing coating integrity or appearance defects.”
Xerox noted that if the finished piece is subjected to cycles of high (≥ 140°F/284°F) to low temperatures, the coating may crack. Paper type does affect performance, of course, with coated, glossy stocks at weights above 140 gsm typically providing the best results. (iGen3 output sheets of basis weight 115 to 120 gsm have been UV coated.) Also, to minimize cracking, book cover applications require creasing at the folds after coating. “Uncoated stocks tend to absorb the coating material and thus not cure completely,” the manual advised. Plus, the plate or roller used to apply the coating may warp lighter weight stocks.
Caution aside, independent manufacturers play in the coating game, too. “The demand for UV coating has intensified in the past decade, especially in the digital environment,” said Tom Hayes, president of Kompac Technologies. Its Kwik Finish series offers 20-, 26-, and 32-inch sizes. Now distributed by xpedx, these are a convenient way to apply spot UV, aqueous, primer, and specialty coatings to a variety of substrates, from thin onion skin to plastics, says the manufacturer. With a smaller, 18-inch sheet size, the X7000 Series Smart Coater from Al’s Co. UV (Chino, CA) is another indie example. The offline system is compatible with Canon, HP, Kodak, Konica Minolta, Ricoh, and Xerox digital devices as well as sheetfed-offset machines from Heidelberg and Ryobi and Presstek direct-imaging (DI) presses. Late last year, TEC Lighting also launched the XB18 UV coater, an 18-inch coater engineered to interface inline with a digital press. Double-sided coatings can be varied, allowing, for example, a satin coating on one side of the sheet and gloss on the reverse side.