By Cassandra Balentine
Roll-to-roll (R2R) UV and UV LED printing devices are favorable for a variety of reasons. The R2R configuration is critical for print service providers (PSPs) producing long runs of flexible media work. In terms of the technology, UV engines, curing lamps, and ink sets on these machines continue to advance, enabling even more versatility.
Above: The Oce Colorado 1640 roll-to-roll printer is ideal for indoor and outdoor display graphics.
UV R2R
Many benefits are associated with UV and UV LED R2R printers; these include the ability to print continuously, immediate curing, lower power consumption, low volatile organic compound (VOC) emissions, and extensive media compatibility.
The continuous print ability offered by R2R devices is important to high production environments. R2R printing systems allow for flexible material to be printed continuously. Becky McConnell, product marketing manager, Fujifilm North America Corporation, Graphic Systems Division, suggests that from a throughput standpoint, a print provider can consider whether its operation lends itself to sheeting roll material to be printed on a flatbed or continuously printed on a R2R machine before moving to post-print and finishing.
Also aiding in productivity is immediate curing. This allows for faster production, enabling users to quickly follow market demands. For example, Volance Carlin, product marketing manager, Mimaki USA, Inc., points out that if a product is featured on a morning television program, retail stores can have their point of sale graphics in stores by that afternoon, allowing them to be more responsive to trends.
“Today, 85 percent of jobs need to be delivered within 24 hours, ten percent within 48 hours, and the remaining five percent in 72 hours. So you don’t have the time to line up a printer, discuss the details, and wait for someone else to complete the job. With a UV R2R printer, you have the ability to complete the task at hand right then and there,” says Sohil Singh, VP, Stratojet USA.
The instant curing process associated with UV allows for many jobs to print without slowing down the operator in order to cut and stack. This saves the end user additional labor costs, according to a representative from American Printing Systems LLC.
Power consumption is a consideration that affects the bottom line in terms of electricity costs, but also environmental impact.
A UV LED inkjet printer consumes less electricity than most forms of wide format printing ranging from latex, traditional UV, dye-sublimation, or solvent technologies. For example, American Printing Systems points out that cold curing temperatures, longer service of light bulbs, in addition to lower energy consumption equals a more environmentally conscious print provider.
“In our industry, PSPs are very serious about the environmental impact of the equipment they choose to bring into their businesses. They certainly want technologies in house that cost less to operate as well as have a smaller carbon footprint, like UV LED,” explains Bill Brouhle, senior application specialist, Agfa Graphics.
Further, UV’s inherent low VOC emissions are another favorable consideration. The technology doesn’t evaporate solvents or VOCs into the air—meaning a better working environment for the operators and a more environmentally sustainable solution, offers Carlin.
Media compatibility is perhaps the biggest benefit UV and more specifically, UV LED offers.
Singh points out that when you use a UV LED R2R printer, media options expand to a variety of textures, sizes, and shapes, allowing users to get creative with printing projects to fulfill a range of needs, including media for soft signage. “Every business has different demands. Some need traditional materials while others want to work with vinyl, flexible, and non-flexible materials. It’s convenient to have the option to print a large vinyl banner on flexible plastic. With a UV R2R printer, your choices are limitless, which is an edge over other technologies.”
“UV LED ink has one of the highest possible material compatibilities, which allows for use of even the most sensitive and uncoated materials,” shares Carlin.
There is also increased demand from end users for ecologically friendly materials that can’t be printed on with solvent printers, adds Jay Roberts, product manager, UV printers, Roland DGA Corporation. “In addition, UV LED R2R printers offer outstanding image quality as well as the benefits of gloss and white specialty inks, which allow users to incorporate unique textural and dimensional effects.”
LED low temperature curing has an advantage when compared to traditional latex, solvent, and even traditional UV mercury vapor technologies. “LED curing allows users to print on less expensive, heat-sensitive materials without any distortion,” says John Kaufman, senior marketing specialist, Canon Solutions America.
Brouhle agrees, noting that when talking about UV LED curing technology, it is important to understand that it operates at a cooler temperature, eliminating issues with heat-sensitive substrates.
Quality is another consideration. Brouhle says the nature of UV LED inkjet is one where the ink sits on top of the substrate, enabling the output to have more color pop as it isn’t absorbed into the porous surface of the scrim, fabric, or banner materials like other inkjet technologies available today.
Durability is another factor. “UV LED inks are exceptionally durable as well as scratch and chemical resistant. These features make UV LED inks the go-to choice for applications requiring high durability, such as long-term exterior graphics,” explains Carlin.
Popular Applications
Many applications are created with the help of wide format UV and UV LED R2R printers. These include floor graphics, window graphics, posters, indoor and outdoor banners, and point of purchase.
Roberts points out that unlike flatbed UV printers, which are typically used for short-run product customization applications, UV R2R models are most often used for longer, more sustained print runs. Common R2R UV applications range from label and membrane panel production to custom large format graphics like window graphics, wall wraps, and trade show displays. He adds that many printer/cutter models are popular for package and prototype applications. “They make it easy to create vibrant, realistic prototypes using a variety of actual press substrates, while also automatically scoring and contour cutting in one seamless workflow,” he offers.
Carlin says applications that require tiling, such as billboards and wallpaper, are popular for UV and UV LED because they benefit from better material stability and virtually no shrinkage, which can cause image offset and misalignment, as no heat is used in the ink fixation process.
In addition to traditional billboards and banners, currently some of the most popular uses for R2R are UV printable textiles for soft signage and other applications. McConnell says this opens up the R2R market to various environmental graphics like bespoke wallpapers or artwork.
Brouhle sees decorative window wraps on clear cling or low-tac films with and without white ink as one of the hottest R2R applications today. “With them, customers can create a private, yet intriguing new specialty application for creating personal space or advertising anywhere there is glass.”
“Multi-layer prints benefit from immediate curing and allow for the creative use of layers to add eye-catching, light molding, or color changing effects,” says Carlin.
Singh suggests one upgrade that takes UV R2R printing to new industries is the ability to print backlit fabrics. The use of PVC, flex, and other plastic composed products decreased in many countries due to requirements for “greener” features. This causes print shop owners to move towards solutions for printing to fabric, like UV R2R printers.
“Many users of a R2R UV LED printer find they can now produce soft signage with brilliant color gamuts. They also find they can produce better densities for backlit signage viewing at night. Colors are not as washed out as they might be using eco-solvent,” explains Mark A. Rugen, director, product marketing and education, Mutoh America, Inc.
White Ink
White ink is important to the production of many applications, including transparent window films, metallic films, and colored vinyl.
White printing capabilities are in demand on R2R devices. “Although there are a number of substrates that aid in printing without white, there are still many applications where printing on clear or dark media requires the use of white ink. This can be substrates like colored meshes for outdoor events to clear films used for window signage or seasonal displays. For print providers who deal with these application demands, the ability to print white ink on a R2R device inline can improve productivity,” says McConnell.
White inks allows PSPs to print directly and effectively on black and other dark-colored substrates. “We are also seeing more R2R printing on leather-type products and fabrics for upholstery. The ability to add white ink on these materials creates dramatic effects and really makes the designs pop,” shares Roberts.
Larry D’Amico, director of sales, large format, Durst Image Technology US, comments that white is especially good for walls, floors, and windows. It is also popular for day/night multi-layer applications for windows using white ink.
“The ability to print desired white for under-flood or over-flood has always been a competitive advantage for UV printers. This gives much better and long-lasting results compared to other technologies. For printing back-to-back signs or printing day and night signage, white comes in handy and is needed much more these days,” adds Singh.
“White ink is installed on a significant portion of wide format machines,” offers Carlin. This is largely due to the flexibility it provides applications.
Applications requiring white ink are commonly found on windows. “In these situations, a window perforated, white media, or semi-translucent material can do the job for a lot less money. The other application for white would be packaging, and this may be suitable for prototyping, but not for any real volume,” says Kaufman.
He warns that while white ink sounds like a great opportunity, the volume is not quite there when looking at high-volume production needs of the R2R market.
Singh believes white is a feature that should only be provided to those print shops that have the use for it. “There is a chunk of people that don’t have the need for white, as most of their substrates are white. It does come at a cost of higher maintenance than CMYK and other spot colors.”
Flexibility Advancements
Traditional UV wasn’t ideal for R2R printers due to its limited range of flexibility. Both ink and lamp technology has improved to make UV more suited for R2R printing.
UV ink formulations undergo modifications to meet flexibility needs. “Flexibility has been possible for some years now as the polymerization process used in curing UV inks is better understood and controlled. This allows us to choose from a wider range of components to achieve varying levels of flexibility as well as influence other characteristics like weather ability and chemical resistance. Nowadays, we even see UV LED inks used for applications like in-mold labeling or thermoforming, where an even higher level of flex and stretch ability is required,” explains Carlin.
When manufacturers began using systems incorporating UV LED curable lamps, the flexibility of the inks increased as these systems allowed the curing to take place at a different wavelength. “While the older mercury vapor lamps were aggressive, they were also problematic because they made the inks brittle and less pliable,” shares Roberts. Advanced UV lamps are designed to maximize the flexibility of the ink, allowing for optimum results on a variety of substrates.
Print systems as a whole are also part of the overall equation. “Today, a number of UV printers in the market meet most print providers’ flexibility tests. For work or jobs where UV ink is a viable solution, other types of output may not be ideal based on the substrate or application. In order for UV inks to work in any application, there needs to be a harmony between the machine, the printheads, the ink, and the substrate, so it’s critical to work with a supplier who can ensure the integration of the printing system is optimized,” shares McConnell.
UV Advancements
In addition to ink flexibility, a variety of other advancements impact the UV and UV LED R2R printer market.
UV LED technology is scaled down in an economical way that makes it more accessible for low- to mid-level users. “Where it was previously almost exclusive to high-volume machinery, UV LED R2R printers are now available from smaller widths and up, enabling users from all backgrounds to harness its power,” offers Carlin.
“In the superwide or grand format space, the quality of the output is much greater than was previously achieved on large format roll devices. Printhead and ink advancements, along with print technology, has enabled this market to not only fulfill banner and billboard work, but other closer viewing applications,” says McConnell.
According to Singh, speed and quality were issues with UV printing technologies at the start, however enhancements in machines, lamps, and inks overcame the challenges.
The latest advancements in UV R2R include more speed and functionality. “The emphasis is always on faster printing, but the key to printing profitability is limiting your labor cost. Many R2R jobs can run unattended if your printer has the ability to handle the specific requirements to do this properly. Tracking material straight, being able to adjust for coning, and other roll imperfections is the key,” explains D’Amico.
R2R Goals
UV and UV LED R2R printers are used for a range of graphics. Advancements in print engines, ink sets, and curing lamps continue to improve, increasing the attractiveness and versatility of these devices. For any print provider planning to continuously print on flexible media, UV and UV LED R2R devices are ideal options.
Mar2019, Digital Output
