By Melissa Donovan
Print service providers (PSPs) enter new markets and offer new applications in direct response to the ability of UV inks to print on multiple substrates—significantly impacting the direction of the graphic arts.
Since its introduction in the early 2000s, the chemical composition of UV ink continues to transform by addressing the need for increased adhesion, flexibility, and curing. LED-based UV inks, which enable printing on even thinner substrates because less heat is used to dry or cure the print, further propel changes.
Human- and machine-based influences effect this ink segment. Scientists must remain aware of customer demand for versatile ink sets while engineering consumables that match the newest printhead configurations. With the influx of options, the cost of UV ink has decreased in recent years, allowing more PSPs to work within this critical segment.
Rate of Adoption
UV ink’s rate of adoption is increasing. The 2015 SGIA Specialty Graphics Industry Survey Benchmarking Report Graphics & Sign Community, held between January and February 2015, reports that UV-curable flatbed purchases are expected to increase. 7.3 percent of shops surveyed plan on buying a UV flatbed in 2015, which is up over 2014’s buying plan of 4.1 percent.
According to internal statics from EFI, UV inkjet overall continues to grow, with a 19 percent year-over-year increase in EFI UV inkjet ink volumes between Q2 2014 and Q2 2015. “The 2015 FESPA Print Census produced by FESPA and Infotrends indicated that UV is the most popular planned purchase decision. 27 percent of respondents in that census survey said their next printer purchase would be a UV inkjet printer and that was the number one response,” cites Mark Goodearl, senior product manager, inkjet solutions, EFI.
“UV technology enjoys a high rate of adoption because of the possibilities this technology enables such as printing on almost any substrate. This is more so in the graphic arts. In the last few years, the overwhelming majority of PSPs purchased UV and UV LED printers, sometimes solely and sometimes in addition to solvent or water-based printers,” shares Guy Evron, marketing manager, Bordeaux Digital PrintInk.
Growth won’t slow anytime soon, with the conversion to UV not even on many PSPs’ radars. “There are companies adhering printed media to rigid substrates who should be printing to them directly. Even jobs are still produced through screenprinting due to volume and/or costs that will eventually be digitally printed,” observes Larry Salomon, VP, wide format, Agfa Graphics.
Manufacturers continue to make improvements to critical elements of UV ink’s composition, such as adhesion, flexibility, and curing. Peter Saunders, business director – digital, Sun Chemical Corporation, walks through the initial chemical construction process many scientists embarked on in the early days of UV inkjet. It was all about getting the ink and printhead to work together reliably so integrators could build hardware around the printhead.
“As systems developed and media capability widened, the inks had to perform across even wider material types, cure fast, respond to pinning, run in faster systems, reliably print with smaller droplets, work in high-frequency printheads and different printhead materials, and be compatible with new media types,” he continues.
In the past ten years, the choice of raw materials used in an ink’s chemicals expanded. “This gives UV chemists the ability to choose from a wider range of monomers, oligomers, and photoinitiators in the development of ink. Monomers and oligomers are chosen based on whether the substrate being printed is rigid or flexible. Different ink sets are developed for plastics, coated papers, glass, wood, coated metals, packaging, and wallcoverings,” shares Heather Rockow, UV business development manager, Collins Inkjet.
Richard Dunklee, global market segment manager – UV inkjet inks, Nazdar, believes this variety of raw materials is a differentiator. “It allows us to formulate inks with specific properties, such as low migration, extreme adhesion to a certain class of substrates, or extreme flexibility.” This is a benefit and a challenge, he cautions. “For general purpose UV inks, we must look very closely at each newly available ingredient to make sure that its benefits don’t negatively impact another important property of the ink.”
Some advancements were noticed in the past two years, admits Craig T. Reid, VP/GM – digital division, INX International Ink Co. “Adhesion to anything and everything—while remaining flexible to not crack or chip and being cured multiple ways—are leading the list of requirements.”
In regards to flexibility, “it used to be the domain of solvent inks, but new formulations of UV inks are enabling greater pliancy,” explains Ken VanHorn, director, marketing and business development, Mimaki USA, Inc.
UV inks are generally hard and cure almost instantly. “The taller the droplet is, the harder it is, and the less likely it is the ink will be flexible. In the past if you wanted to do a car wrap with UV ink, it was nearly impossible,” says Adam Larson, global portfolio manager – premium films, 3M Commercial Solutions.
Part of the change in chemical composition is the introduction of UV LED. “We feel the industry is trending more towards LED for power usage and heat output. More substrates can be used and distortion of the material is less of a concern,” shares Chuck McGettrick, sales manager digital inks, Marabu North America.
VanHorn refers to UV LED technology as “cold” curing, enabling a PSP to print and cure thinner plastics and papers. “UV LED lamps only heat when curing, don’t require lengthy startup cycles, and draw much less power than conventional lamps,” he continues.
Curable and LED
UV is divided into two categories, UV LED and UV-curable. Their chemical compositions and functionality differ, in addition to how they react in the curing process—which is dictated by the type of lamp used.
In basic terms, both variations of UV ink feature photoinitiators that respond to different wavelengths, UV LED to a smaller range and UV-curable to a larger range—which is why UV LED ink uses less heat then UV-curable ink in the drying process.
“In a standard UV ink there are multiple initiators. LED ink usually uses just one initiator. The different initiators affect the curing of the ink at different wavelengths and therefore at different levels of the ink and substrate,” continues McGettrick.
“The fundamental difference is the incorporation of photosensitive materials that maximize the ink’s response to the chosen wavelength of the monochromatic LED light. The polymerization—or cure—is started by materials that respond to the differing wavelength in LED systems,” explains Saunders.
Jay Roberts, product manager, UV printers, Roland DGA Corporation, compares UV-curable and UV LED inks in regards to functionality. “UV-curable inks tend to be more aggressive, bonding to a slightly greater surface area. Substrates printed on UV-curable inks also have a tendency to bubble, buckle, yellow, and wave. UV LED inks can have a less aggressive bond to substrates without a more aggressive chemical bonding agent.”
The manner which UV and UV LED react during the curing process is based on the photoinitiators found in the ink. “Photoinitiators are chosen based on whether the curing device is a mercury arc lamp—traditional UV—or an LED curing unit,” explains Rockow.
According to Dunklee, inks designed for mercury arc curing typically have a blend of photoinitiators that respond to many different wavelengths simultaneously, and some contain an initiator that reacts to the specific wavelength being output by an LED lamp. However, the cure may not be as efficient or complete if the ink has been exposed to a multi-chromatic UV bulb.
“This situation can lead to two problems. If the ink doesn’t contain a photoinitiator that can react to the LED wavelength, it will not cure. If the ink does contain a photoinitiator that can react, the question becomes one of having enough initiator in the formula to fully cure the ink,” he adds.
Influences on a Wide Scale
UV ink is influenced by a number of factors. Customer demand and new applications propel advancements in this field. Additionally, enhancements to hardware require improved ink compositions.
“The increasing demand for more innovative solutions, including hardware, printheads, and accessories, influences the development of digital UV inks. Competition within this market constantly drives product development,” shares Roberts.
Rockow says Collins’ customers—the users of the inks, are driving the achievements. “When they use an ink that won’t adhere to a new substrate, cracks instead of bending, or doesn’t cure well with their printer, we develop one.”
“It is the market opportunities for using UV-curable ink that influence innovation and creativity in formulating new technology,” agrees Reid.
Eyal Duzy, marketing segment manager, HP Scitex worldwide, Hewlett-Packard (HP), points to new applications like corrugated displays and boxes. “Stacking high stacks of printed media, folding with no cracking, creasing with no scratching or smearing, and cutting with no chipping calls for great durability and high flexibility from the ink set.”
Matching the ink to the hardware is still top priority. “The requirements of the printhead remain one of the primary considerations in developing inks. If the physical properties aren’t matched—nothing works. The fine detail comes later but viscosity is still the first thing. The internal flow paths in the printhead affect formulation choice as the pulse input is transmitted through the architecture and the ink fluid,” explains Saunders.
The printheads’ ability to jet smaller dots also plays a role. “As the technology advances and the sizes of the droplets fall to two to five picoliter, the ink must be developed to work in these newer printheads. Every year the speed at which these printers print increases and as such you must have an ink that can keep up with the demand of these new high-speed printhead technologies,” says McGettrick.
Reid agrees, citing specifics such as smaller drop size, higher frequency, addressable resolution, and single pass compared to multi-pass applications. “The chemistry must keep up with hardware speeds, so jetting reliability is much more important in these new single-pass LED cure systems,” he continues.
In addition to the printheads, other design elements of a printer—such as build quality, how vibration is minimized, static reduction, and step accuracy—are critical to image quality and long-term performance, points out VanHorn.
On a larger scale, forces outside of the graphic arts effect UV ink’s development. End customers demand “greener” output and while UV is designed in many respects to combat this, there is still room for improvement. “There are global regulations that effect UV ink enhancements, making them safer for customers to handle and for those who come in contact with the final printed graphics,” says Goodearl.
The Cost of UV
With compositional and usage modifications, it is no surprise that the cost of UV ink continues to change as well. The price of UV ink is decreasing for two reasons—cost of materials and competition, which creates product volume.
McGettrick explains that the raw materials used in the development of UV ink are generally more affordable. Although, he points out that in some cases—such as metallic or special colors—those raw materials may be more expensive, which translates to higher specialized ink costs.
UV technology is becoming widespread and in recent years there have been a number of alternative options available to PSPs in the form of third-party inks. “The introduction of quality non-OEM inks influences the prices of wide format ink for every technology including UV,” cites Evron.
Additional ink types are an influence on cost. “As other technologies continue to improve, it does drive down the price of UV ink. The customer is aware of the roll-to-roll cost of latex versus UV,” shares Larson.
This price decrease will continue, foresees Salomon. “Cost per square foot has come down and probably will continue as the display graphics industry mainstreams into the general printing world, which has been more of a commodity for a while. This industry has moved from being a niche or specialty to a manufacturing business.”
UV ink will play an important role in the direction of the graphic arts. Changes in the ink’s chemical composition mean a wider variety of substrates can be printed to without damaging a print. This expansion of printable materials presents PSPs with new opportunities.
Dec2015, Digital Output