Roses are Red, UltraViolets are Green

UV-cure digital print technology is being positioned as a greener printing solution because it generates no harmful VOCs. This is a significant advantage, but UV-cure printing alone cannot entirely support a claim that a shop is “printing green.” Issues involving substrates and ozone mitigation are parts of the puzzle that must also be addressed in order to complete and legitimize green claims about UV-cure printing.

A complete carbon footprint includes all “cradle-to-grave” activities — from how materials are extracted from the ground, to what happens with discarded prints and outdated equipment. Ultimately, most of the control over the degree ofgreen-ness associated with the use of a UV-curing flatbed lies with the user and the choices made regarding substrates and other fabrication and production practices.

The lack of appreciable levels of VOCs is a major “green” talking point in favor of using UV inks.
Solvent-based inks are great because they will adhere to uncoated media, will hold up to the elements and are relatively inexpensive. But the VOCs that solvent inks release are not good to breathe. Safe operation requires appropriate ventilation, a measure which is good for reducing exposure to workers, but all too often the ventilated VOCs are then released into the atmosphere and thus contribute to air pollution. Better to combine ventilation with some type of air filtration unit to capture the harmful particulates before they get into the atmosphere.

In terms of raw materials — such as the monomers, oligomers, photoinitiators and pigments that make up UV-curable inks — UV-curable inks seem to have a similar carbon footprint as the materials used to produce their solvent- and aqueous-based cousins. There is a potential that UV-curable inks could be made from raw materials derived from renewable sources in the future that would compare to the corn-based bio solvent inks that manufacturers like Inkware (EFI-VUTEk) and Mutoh already have on the market.
Compared to solvent inks, UV-curable inks are reported to require smaller volumes for the same amount of coverage and there is also little if any wasted ink compared to solvent systems, which generate a lot of waste during printer cleaning cycles.

Still, with regard to ink, the absence of VOCs is the greenest advantage of UV, and it might be the most important one.

Bron Wolf is the Quality Assurance Manager for Indianapolis-based Pratt Corporation, one of the first digital printing companies certified in the SGP (Sustainable Green Printing) partnership. Pratt Corporation has two UV-curing Inca Turbo flatbeds and an Inca Spyder flatbed in-house. Wolf says the company emphasizes the reduction of VOC emissions, as well as the disposal and recyclables involved in the liquid and solid waste stream when assessing the impact of UV-cure inks and communicating those environmental impacts to clients.

Minneapolis-based large-format print provider Pictura Graphics, the first printer to become certified in the SGP program, utilizes a number of UV-curing printers from Durst including the Rho 160 and 351 models, as well as Durst’s 600 Pictor and 800 Presto UV-curing models. “I stress the eco-friendliness of digital printing in general, both in terms of low-VOC and the inks utilized,” says company president Paul Lilienthal.

The ability to print directly onto a variety of rigid substrates has long been a big talking point that favors UV-cure flatbeds. More directly, there is less human energy expended because direct printing eliminates the process of mounting and also eliminates the need to dispose of the release liner from adhesive-backed vinyl.

This feature can be leveraged to point out an even smaller carbon footprint if substrates are made from recycled content or renewable resources or are biodegradable. Pictura’s “ecoImages” line of eco-friendly materials, for example, was developed specifically to meet a growing demand for greener print output.

Ann Brown, co-owner of New Vista Image, Golden, Colo., says that the HP-Scitex VeeJet flatbed UV printer the company acquired in 2004 is very often used to print onto various types of wood, wood veneers, glass and other recycled and bio-degradable substrates. “There are challenges,” says Brown, “especially with wood products related to thickness, warpage, color rendering, durability and availability. But overall it’s an advantage and an important selling point with architects and others who are seeking materials that are LEED-certified.” The Leadership in Energy and Enviromental Design (LEED) certification system was developed by the U.S. Green Building Council for the building construction industry.

Wolf acknowledges that many of Pratt’s common substrates–styrene, PVC-based products, foam boards–are not biodegradable or able to be recycled, but the company is constantly searching for new materials. “We have been doing significant testing with newly developed products in the banner market and from plastic manufacturers,” says Wolf. “We are on a path to eliminate nearly 50 percent of the PVC usage and disposal in the company in the next two years.”

The most common cure-lamp light source in UV-cure printers is in the form of mercury arc lamps. These lamps are capable of generating the levels and intensity of the UV light spectrum necessary to accomplish the cure.

The drawback to them has been two-fold. First, is that there is a tremendous amount of heat generated along with the light. Because of this heat, coolers are often needed to keep media from becoming distorted while being exposed to the curing UV rays of the lamps. This requires an additional component of the printer as well as additional power for its operation.

The second drawback is that ozone is an incidental by-product generated by mercury arc lamps. While ozone levels resulting from the use of UV cure printing have been found to be below workplace standards and generally viewed as a small price to pay for other advantages, ozone is ozone and its absence entirely would not be unwelcome.

One of the more promising solutions to both of these light problems lies in further development of LED-based UV cure lamps. UV LED lamps eliminate both the intense heat and the incidental production of ozone associated with mercury arc lamps. A third benefit is that LEDs require less power to operate and a fourth benefit is that LEDs will not need to be replaced nearly as frequently as mercury arc lamps. So why have LEDS not been incorporated on a large scale into digital UV printers?

Half the problem up to now has been in finding an LED lamp that produces UV light in the spectrum and intensity necessary to fully cure UV ink at an acceptable rate. The other half of the problem is in optimizing the ink chemistry so that the photoinitiators in the ink react to the narrower spectrum of light produced by the LEDs.

These barriers are breaking down with printers appearing on the market such as the NEO UV-LED, a hybrid printer from Russia-based Sun LLC released in 2007, and more recently Roland’s Versa UV, a dedicated roll-to-roll UV-curing printer/cutter. And Mimaki’s dedicated roll-to-roll printer, the UJV160, which was demonstrated at SGIA, is scheduled for release in early 2009.

So far, speed is holding these printers back from being adopted for high-production purposes.

Cure-lamp developers such as Summit UV, Phoseon Technology and Integration Technology are poised to release a new generation of LED-based cure lamps specifically made for digital UV-cure inkjet printing. These lamps hold more promise for full cure with little or no loss of speed. Summit’s early forays into the arena involved bolting their lamps into a ColorSpan UV-cure printer and firing up the machine using ColorSpan’s off-the-shelf OEM inks. Summit was able to achieve decent results, but when the ink formulas were optimized to the specific 365-nanometer wavelength of Summit’s Black Diamond lamps, the company reports that a dependable full cure was achieved with no loss of speed. At the recent SGIA show, Summit released its own flatbed UV-curing inkjet printer equipped with its Black Diamond lamps.

Indeed, the carbon footprint issue looms large in current discussions among the general population. Specifically defining what to measure and how to measure it in a way that is meaningful to potential print clients is still being developed within the SGP program. But the simple fact that a company is taking sincere steps toward reducing its carbon footprint will often be all it takes to gain the trust of important clients. The fact that you are on the path toward true sustainability, are making a verifiable good-faith effort, speaks volumes.

UV-cure digital printing has the potential to become an important part of the green movement, but it involves verifiable proof that discriminating and savvy clients will demand. “The inquiries and overall awareness surrounding environmentally friendly services and solutions has been steadily increasing over the past six to twelve months,” notes Pictura’s Lilienthal. “There are a number of companies that specify UV digital printing in their bid and quote requests versus traditional print methods. Where I see the greatest demand is for eco-friendly or ‘green’ materials.”