Although inkjet printing has made great strides in label production and many other graphic applications, flexible packaging remains a steep hill for the process to climb.
Inkjet’s limitations here are numerous, starting with the fact that aqueous inkjet inks don’t adhere well to flexible film surfaces. Using UV-curable inks offers a way around that issue, but with conventional UV curing, there can be concerns about heat, odor, and safety when it comes to packaging for food.
In terms of print quality and durability, flexography—the dominant process for flexible packaging printing—sets the bar higher than most inkjet systems have been able to clear.
At drupa 2016, Fujifilm showed a new platform that may have what it takes to surmount all of these obstacles. The device, called EUCON, is currently available only in Japan, but it has been designed to solve problems that are universal to flexible packaging production with inkjet equipment.
EUCON is short for “enhanced undercoating over nitrogen.” The name conveys its three main components: a newly developed five-color UV inkset; an equally new undercoat primer; and an oxygen-banishing process that greatly reduces odor and migration. These assets and a low-heat LED-UV curing system are housed in a rollfed press that can process flexible materials up to 54 centimeters (21.26") wide at a top printing speed of 50 meters (164 feet) per minute.
EUCON is by no means Fujifilm’s first inkjet solution for packaging and label applications. Its J Press 720S, a B2 sheeted press for commercial and folding carton work, entered the market in 2011 after its debut as a technology concept at drupa 2008. During drupa 2016, Fujifilm showcased Graphium, a hybrid flexographic and UV inkjet press for labels and packaging. The company’s inkjet technology also is a key component of Heidelberg’s Primefire 106 industrial press and of the Heidelberg-Gallus Labelfire 340, another flexo-UV inkjet hybrid.
The new press is different in that it will target pouches, bags, and possibly shrink sleeves, but not labels. It is engineered to take on three challenges that can make inkjet printing on flexible materials difficult: insuring ink adhesion; controlling laydown; and assuring food safety.
The problem-solver for adhesion is the primer fluid, which is applied as an undercoat before the ink. The primer helps to keeps the ink from bleeding, peeling, and cracking—the keys to accurate and attractive color reproduction on non-absorbing flexible films.
The specially formulated CMYKW inks then can be reverse-printed on the underside of the packaging material, cured, and covered with a layer of laminate film so that the right-reading color and artwork are visible through the clear and protective surface of the package. In this sequence, the transparent process colors go down first, followed by the opaque white.
Ensuring that the printing will be food-safe is one of the hallmarks of EUCON’s UV inks. They are formulated for low migration as well as for adhesive strength and heat resistance—properties that help the package stand up to processes like heat sealing and sterilization during converting and filling.
The nitrogen purge, which takes place between the color laydown and the LED-UV cure, goes hand-in-hand with the low-migration characteristics of the ink.
UV inks become dry and hard-surfaced when exposure to UV wavelengths causes their small molecules (monomers) to form chains of large molecules (polymers). Curing that doesn’t fully polymerize the chemistry of the ink leaves monomers that may pose an unacceptable risk of migration in food packaging.
In conventional UV, the presence of oxygen may limit the extent of the cure to less than 100%. EUCON gets rid of the O2 by flooding the inked surface with nitrogen gas as it is transported to the curing unit.
This is essentially the same technique used to remove spoilage-causing oxygen from snack food bags during filling. In a nitrogen-rich, oxygen-free environment, the cure can be 100% efficient, eliminating the migration risk. The laminate layer caps the protection by sealing the ink between itself and the surface of the packaging material (which must have appropriate barrier properties for use with food).
Until the advent of LED-UV curing, the ability to print heat-sensitive flexible substrates with UV inks was extremely limited. Because its UV-emitting LEDs generate considerably less heat than conventional ultraviolet lamps, EUCON can run a wide range of packaging films.
Fujifilm has no immediate plans to market EUCON outside Japan, where food packaging safety regulations are different from those in the U.S. But, the company sees the innovative press as the foundation of a dependable inkjet printing solution for short-run flexible packaging wherever it is being done. Fujifilm will continue to investigate EUCON’s potential for adoption in other world markets.