Glossing Over Differences

Substrate and equipment concerns plot printers on either the aqueous or UV route to high-gloss printing.

by Jessica Millward, Associate Editor

UV-CURABLE FORMULATIONS are the big hitters of the coatings and adhesives market—offering remarkable gloss and great abrasion-, heat-, and chemical-resistance. Slightly less high-performance, yet in some cases more predictable, aqueous adhesives and coatings serve as reliable all-rounders. Suppliers say choosing between them depends on the nature of the job, and the equipment, at hand.

Luster low-down

Coatings manufacturers are largely unanimous when it comes to the virtues and challenges of aqueous and UV-curable formulations. Craig Adhesives & Coatings President Pat Foust, whose company manufactures both aqueous and UV-curable adhesives and coatings, attests to the benefits of a UV coating: "Basically, UV coatings give higher gloss and better protection than aqueous coatings."

In a presentation given at the GATF Tech Alert 2001 Conference in January of this year, Don Duncan, director of research for Wikoff Color Corp., reaffirmed the high gloss benefit of UV coatings, and named a few others. He notes, "UV and EB inks and coatings dry instantaneously when exposed to the curing unit on press…[and] tend to have fewer blocking problems than water-based coatings."

Dave Lenarduzzi, Canadian Sales Manager at KROMA Inc. (member of the SICPA Group), cites the superior resistance properties of UV coatings, the complete lack of VOCs, and their improved adhesion on various non-porous substrates as major selling points.

Meanwhile, aqueous coatings demonstrate similar characteristics, only to a slightly lesser degree. They are usually available in three levels of gloss; they provide a sound level of protection for inks; and they contain no alcohol and few VOCs.

The line of demarcation in choosing a coating comes down to equipment, economics, or substrate. Foust has witnessed the expansion of UV-curable products within the narrow-web market, as he says, "because it's easier to put UV lamps on these presses than large dryers for aqueous products."

Lenarduzzi agrees, estimating UV coatings dominate labels with about 80 percent of that market. However, as he points out, aqueous coatings, which are used primarily in food packaging applications requiring low taint and odor, make the better choice for certain porous substrates, where UV coatings do not always produce the desired end-result.

UV coatings' price tags are higher, but Foust maintains for a more accurate view of costs, all factors, including reduced waste and increased productivity, must be taken into account. As he states, "We've seen applications where a $4.00/lb. UV coating offers better value at a lower cost per piece than an aqueous coating at $.90/lb."

Additionally, the base price for UV materials becomes more attractive as raw material expenses come down. As Duncan explains, photoinitiators, the most expensive component of most UV inks and some coatings, were originally patented and sold at high prices. "Now," he continues, "patents are expiring and many smaller companies…are offering these photoinitiators at markedly lower prices."

UV adhesives are similarly very strong in several areas. As J. Michael Rivera, VP/sales, Beacon Adhesives says, "Compared to water-based or hot-melt adhesives, UV-curable adhesives are faster-drying, easier to print and clean up, and consume less energy." Foust adds UV adhesives also allow the press to operate at peak speeds.

Northwest Coatings Corp. Technical Director Stephen Lapin sees problems with using water-base adhesives on a typical narrow-web press. The current generation of UV PSAs addresses these issues: difficulty in drying >1.0 mil film thickness; troubles in maintaining consistency with variable humidity conditions; and problems in adhesive clean-up.

On-shelf appearances

Challenging UV's claim as high-gloss champion, NCL Graphic Specialties, a coupon and label printer based in Waukesha, WI, has developed an ultra-high gloss aqueous coating. NCL High Gloss® was created for label users to rival the brilliance provided by UV coatings while keeping costs at traditionally lower aqueous levels.

Water-based adhesives are also making more appearances. Foust remarks on the use of an aqueous adhesive for piggyback labels and coupons, which, along with a companion release coating, allows consumers to remove and reaffix secondary labels on containers and packages. This construction, Foust believes, is also well-suited to attaching promotional messages, such as coupons, games, and contests.

UV-curable coating technology is only getting more popular; different formulations and applications seem to crop up daily. Duncan cites such popular end-use products for UV coatings as pet food bags, liquor boxes, and golf ball boxes. Foust comments scratch-off tickets have enjoyed a surge in popularity thanks to UV-curable coatings.

The hot prospect of cold foil printing has drawn much attention to UV adhesives' potential. Proponents assert the process provides high-impact print effects, like metallics or holographics, without the large equipment investment of hot foil stamping. Lapin also points to specialty constructions commonly based on UV adhesives, such as wrap-around labels, coupon labels, and security and tamper-resistant structures.