To UV or Not to UV. . .

UV inks are commonly used in package-printing applications. So much so that Don Duncan, director of R&D, Wikoff Color Corp., thinks it’s about time to rephrase how we reference ink categories.

In referring to water-based and solvent-based inks, he says, “I use the phrase ‘so-called conventional’ because UV inks are now so common that they are no longer ‘unconventional.’ We need a new word for the mixture of oil-based, water-based, or solvent-based inks that UV is replacing. How about ‘old-technology.’”

The term “old technology” might not fly (Duncan admits that it’s “a little over-the-top”), but the point is well made. UV inks are firmly established and are having significant positive impacts on print quality and consistency.

UV inks are being used in a wide range of product categories. Mike Buystedt, director of new market development, XSYS Print Solutions, lists a diverse collage: wine labels, HBA, non-direct food labels and food packaging, food cartons, and pouches, to name a few.

Bob Waddington, general manager for UVitec Printing Ink, believes that UV inks are a good fit for markets such as these, “because they print sharper, enable the printer to utilize higher press speeds, and enable the printer to finish converting immediately after printing.”

In looking at the use of UV inks, Duncan addresses the higher acquisition cost of UV inks. “Since UV inks are more expensive than so-called ‘conventional’ inks, the application must require some performance property from the UV ink in order to pay the cost. This will normally be the immediate drying that one gets from UV inks, their sharper printing, their higher chemical/moisture resistance, broad adhesion properties, or their ability to UV coat in-line.”

The higher acquisition cost of UV is one of the factors that dictates what types of products will consider using UV inks. Kurt Hudson, general manager, UV products for Water Ink Technologies, says there are two general rules for the likelihood of using UV inks. As the cost of the substrate goes up or the cost of the product itself goes up, UV inks are more likely to be found in the packaging. The reason is not just the higher cost of the inks, but products such as these can support, and more likely require, the higher print quality that UV inks can offer.

“UV inks can provide inherent durability, along with consistency in character definition and graphics,” says Hudson. “You can print cleaner in very, very fine copy, and product number one looks just like product number 1,000.”

UV: Flexo, offset, screen

UV inks are being used with all of the major printing processes—flexo, offset, screen, gravure, and letterpress. The reason is that, “a lot of the quality improvements [from UV] cut across all the printing technologies,” says John Kalkowski, marketing manager for Sun Chemical. “This includes UV’s ability to provide an improved dot structure with less dot gain, along with its superior chemical, water, and light [fading] resistance.”

Flexo inks have benefitted the most from UV technology, primarily because flexo had the most to gain from improvements in dot gain. “Dot gain is more pronounced with flexo inks because flexo inks have lower viscosity than any other ink system,” says Waddington. “So the problem is not as pronounced with other ink systems in relationship to flexo.”

Hudson reiterates that good color consistency and good print quality consistency are characteristics of all energy-cured products. Within the different printing technologies, however, there are some differences.

“UV screen was one of the first to grasp UV and it is now a dominant high-quality ink system,” he says. “One of its primary benefits is that it will not evaporate in the screen.” Although the use of UV screen will continue to grow, he says it is slowing down.

Buystedt believes that UV screen and UV offset are experiencing some of the most significant quality improvements as of late. “Silicone-free UV screen ink technology has made screen printing more compatible with UV flexo technology, which opens many more doors in combination printing,” he notes.

With UV offset, Duncan sees a distinct difference based on the substrate being used. “When UV litho is printed on plastic substrates, as much of it is, highly structured inks that will give very sharp printing are common. However, when UV litho is printed on plain board or paper, especially with a high recycled fiber content and a lower-strength surface, some creative ink formulation must occur to retain high print quality, while eliminating picking and piling issues from the board.”

Hudson also points out some of the qualities that UV offset brings to the table. “If you need precise dot structure, or beautiful vignette, then UV offset is the answer. However, run-to-run color consistency can be difficult—you need to dial in every color, every time.”

Recent quality improvements in UV offset inks noted by Buystedt could address some of these concerns. “As it relates to UV offset inks, the newer ink technologies have a wider operating window, which allows UV offset printers to print using very high screens without having issues relative to water-balance,” he states. “New UV offset inks are also being used for UV letterpress applications, which allows printers to satisfy both print-technology needs only having the inventory of one ink technology.”

Although UV has had a positive impact on letterpress, this technology as a whole has been relatively flat for many years. Hudson attributes this to the significant quality strides made in flexographic printing. Letterpress does have its strengths, such as the ability to provide strong colors. There is also an installed base that reaps the benefits offered by UV technology. Kalkowski says that Sun Chemical has one customer that prints 10 million folding cartons per day using UV letterpress—not too shabby.

UV will continue to increase its stake in package printing and Buystedt believes this will be in all markets. “Currently, less that 30 percent of the packaging market is UV, but as the market continues to convert to UV, we expect double-digit annual growth for some time.”

The advantages that UV inks offer put it in a position to benefit from industry trends. According to Hudson, the continued increase in regional and seasonal product offerings by consumer product companies is “driving the industry toward narrow and mid web, which is the domain of UV inks. We are seeing an exponential growth in SKUs.” n