Refining UV Ink

The hardware, inks, and media used by UV-curable printing have generally followed the same path taken by aqueous and solvent printing in terms of print production and markets served. The main advantage that inkjet has traditionally offered is its minimal cost set-up and the ability for each and every print to be different in size, color, and quality-options not available on commercial color presses and not affordable for screen printing. But, to many, inkjet has always played second fiddle to commercial or screen printing because of its relative lack of speed.

Now, thanks to UV, more speed has been added to the inkjet side of things, considerably changing the print equation. In fact, UV-curable printing is growing in almost every way possible-in a variety of printers, inks, and compatible media (both rigid and rollfed, and even textiles). And UV printers are getting faster, printing at higher resolutions, offering more substrate options, and becoming more automated-all factors that are pushing that growth. These changes are also opening up new markets that have never previously used, or considered, inkjet technologies.

A growing UV population
If you attended one of the recent industry trade shows such as ISA or SGIA, you saw that more and more UV-curable printers are being introduced. About a dozen new printers made their debut at ISA in the spring, and another dozen came to the fore at the fall SGIA event. So within the space of 12 months, some two dozen UV printers are now in the marketplace that were not there previously. That’s a hefty jump.

Beyond those numbers, here’s what three leading market consultants have to report:

* “We’re projecting very strong growth in the worldwide UVcurable inkjet printer market, with new hardware shipments growing at 30% annually,” says Tim Greene, director of wide-format at InfoTrends/CAP Ventures. Specific market drivers include printers with more options, improved image quality, environmental friendliness, and ease of printing onto rigid.

InfoTrends forecasts shipments of UV-cure machines to experience double-digit growth through 2010, and predicts that by 2010 ink revenues will surpass hardware revenues as the largest revenue stream in the UV market. “New capabilities can expand the range of applications that UV-curable inkjet printers produce and bring a faster ROI for the companies that invest in them,” says Greene.

* Lyra Research predicts a 38% growth for the UV-cure market by 2007, with an increase in the worldwide sales of printers from $310 million in 2005 to $427 million in 2007. “Manufacturers… have made improvements in areas such as printer speed, hardware reliability, and ink durability, opening the door for a slew of new applications using this technology,” says Grey Held, director of Lyra’s wide-format printing advisory service.

* And, in our September 2006 article, “Putting the Market Under a Microscope,” Patti Williams of I.T. Strategies noted that she expects “high growth coming for UV printers-primarily flatbed, but also the new hybrid flatbed/roll printers. In terms of manufacturer revenues, the UV segment is experiencing the highest growth-not the highest revenues, but the highest growth.”

Printheads advance
One of the keys to growth in UV-curable printing has been the innovations and changes in its supporting technologies. In the case of UV printing, that means the printheads, inks, and curing lamps. These all work together, of course: The printheads dictate the ink drop sizes and ink-deposit speed; the ink is integral to the

type of printhead and lamp; and, in large part, the lamps deter- mine the speed of the printer. So innovation in any or all of these areas can dramatically impact UV-curable printing.

When it comes to printheads, improved print quality and reliability are significant, but so is speed-and end users typically demand all three. “The goal of virtually all the new heads coming out is to achieve better image quality-or maintain current quality-at higher production speeds,” says Ron Waters, president and CEO of Durst Image Technology.

Cost also becomes a factor; printhead prices, for initial as well as replacement heads, are high. “Today, it’s too costly to put in the thousands of jets required for both high productivity and high reliability,” says Mike Wozny, EFI Vutek product manager. Decreased head prices will make printers cost less and maintenance less expensive for owners.

Better quality typically means smaller ink droplets-as well as more control over how and when drops of ink are deposited. Beyond laying down smaller and smaller ink drops, another way to accomplish this goal is via grayscale printheads. Grayscale heads generally feature three to eight drop sizes for smoother image transitions, cleaner edges, reduced granularity, and output with quality that approaches, if not matches, photo imaging. New heads that employ grayscale technology include the Toshiba Tec, which features eight levels of grayscale with drops from 6 to 42 picoliters, and the Xaar OmniDot 760/GS8 head, which offers up to six levels with drops from 3 to 40 pl.

However grayscale heads are expensive, adding further to the cost of the printer. “If grayscale technology stabilizes and becomes less costly, it’ll impact the market. Others have tried but have had limited to no success,” says Wozny.

Says Ziki Kuly, marketing manager, HP Inkjet Industrial Division America: “Grayscale solutions, while providing the potential for higher resolution and more detail, may negatively affect the throughput of the systems or require higher cost for the same performance. We do not see a major adoption of grayscale in the near-future.”

Instead, HP has pursued its new Scitex X2 printhead, which features a plug-and-play credit card-size head that offers resolutions up to 800 dpi. HP reports that the printhead is highly durable and has a drop volume of 50 pl, allowing for the high ink flows necessary for high-speed, high-production printing. Built on technology perfected in the semi-conductor industry, the X2’s Micro Electro Mechanical Systems (MEMS) enable high-tolerance manufacturing for uniformity and performance. In addition, all of the head’s parts that come into contact with the inks are made of silicon, glass, and epoxy-making it highly resistant to corrosion. The X2 heads will premier in machines in early 2007, in the yet-to-be-released HP Scitex XL2200 (according to HP, it will be twice as fast as the XL1500) and the FB6500.

Expanding the ink gamut
Since UV inks involve a perfect match with heads and lamps, they require a complicated formulation. Most UV-cure inks are still only offered by machine OEMs, although a few third-party UV-curable inks are now available from companies such as Sun Chemical, Hilord, and Triangle Digital.

Many UV-curable printers offer the basic inkset: CMYK. Some have expanded the set to include light cyan and light magenta, while others are moving past simple inksets and are widening their machine’s color gamut with the addition of orange, green, blue, or violet. Raster Printers’ 4000 series Premium UV-curable inks for its Daytona and RP-720UV, for instance, adds orange and blue to its CMYKcm inkset. Gandinnovations’ Jeti 5024 UVRTR and several Eastech Octra machines offer orange and green, while the Gerber Solara UV2 offers green and violet.

The most frequent addition to inksets, however, is white. Now common in UV-curable machines, white offers the option of printing as a flood behind, a flood after printing, or as a spot color.

White ink is “important for growth in that it satisfies more customer needs by making more ‘looks’ and applications possible,” says Durst’s Waters. “The ability to produce white detail, for example, on virtually any display material utilizing a relatively uncomplicated UV process is a significant benefit.”

Other UV printers-such as those from Durst, Luscher, and Eastech-are offering the availability of spot colors. UV-curable color matching, however, has to be exact and is costly for ink manufacturers to produce for a single customer. Roger Walkley, Inca Digital Printers product manager for flatbed printers, says: “The difficulty is that the number of available pigments is smallish, and most current sets are designed for a 4-color process.”

Varnish is another burgeoning ink/coating offered for many UV-curable machines. This capability, along with the expanding color gamuts and addition of spot colors and white, are helping UV-enabled print providers rival offset and screen printing.

“More market understanding and application knowledge for these new inksets will be important for their success,” says Tony Fulco, marketing development supervisor, 3M Graphics Market Center. “Ultimately, new solutions would likely open up even more possibilities of moving from traditional printing techniques (screen printing) to digital printing.”

Until now, UV-cure inks couldn’t compete with solvent inksets in flexibility. “Flexibility of ink after processing is difficult because the polymerisation [the reaction of the inks to the light to create the solid ink state] creates a rigid surface which lacks stretch in, for example, vacuum forming,” says Inca’s Walkley.

Recently, however, Durst and 3M collaborated to introduce 3M’s flexible UV-curable Piezo Inkjet Ink Series 2700UV inks, which are paired with the Durst Rho 160R-a 62-in. roll-to-rollUV-curable printer designed to primarily print vehicle graphics using 3M inks and media. The printed product is conformable around complex curves, as well as rivets and corrugation. In addition, 3M also has brought its Series 2200 flexible UV inks to market for the EFI Vutek printers. Aellora Digital is looking to its Hybrid UV-curable semi-solid inks as the way to make its UV-curable print engines stand out. In its system, the inks are jetted hot, and immediately become highly viscous (thick) upon contact with the substrate-the drops will not move or lose resolution, says the company.

This allows the inks to be printed onto porous or non-porous materials without immediate curing. “With our inks, we use the

physics of the inks-the inks’ high viscosity state-to restrict dripping and dot spread,” says Mike Stoudt, president of Aellora

Digital.

Meanwhile, other ink developments are likely on the horizon, including: Inks that respond faster to UV light at lower temperatures that would allow for printing onto a broader range of substrates. Metallic inkjet inks would mean highmargin projects for printers. Specific inksets for specific media such as glass and ceramic would also expand the range of applications for UV-curable print providers. And the ability to jet conductive materials would increase the potential applications and markets for UV-curable printing.

The magic lamps
By design, UV-cure inks can’t bind to the substrate without

a matched light source. Hence, virtually all UV-curable printers come equipped with a UV-curing lamp or lamps. Typically mounted right next to the printheads, the ink is cured just moments after being deposited by the heads. If a printer only offers one lamp, that means it only prints in one direction (unidirectional printing), such as the Inca Spyder. Printers with two lamps can print bidirectionally, and include the Raster Printer RP-720-UV and the Agfa Anapurna.

In a UV-curing system, the lamps may be the bottleneck in the printing process, dramatically impacting the speed of the machine. The performance of UV-curing lamps must evolve to keep up with the rate at which the print can be put down.

Typical lamps used for UV-curable inks are mercury lamps- either mercury vapor or mercury halide lamps (mercury vapor with metal halogens). The spectrum of light produced by the lamp is matched specifically with the wavelength needed to cure an ink. In terms of safety, there is a need to protect eyes and skin from the UV-curable light. In addition, the weight of the lamps can weigh down a print carriage.

“LED UV lamps may be the next big innovation,” says 3M’s Fulco. “LED UV lamps will offer more advantages than the current UV lamp technologies, but inks will need to be formulated specifically for this technology. It’s not clear [however] that LEDs are capable of delivering enough intensity/dose to cure current pigmented UV ink systems,” he says.

Luscher JetPrint, however, is offering just such a UV-LED lamp-curing system: Developed in conjunction with Phoseon >(www.phoseon.com), a manufacturer of high-intensity light sources, the LED-based lamps reduce the heat generated and lower energy requirements, as well as operating costs. In addition, the LEDs offer a longer lifespan versus halogen UV lamps and decrease warm-up time to nothing; as a result, the system is ready to print as soon as it is turned on.

“Ultimately, UV-curing lamps may drive changes in UV hardware and ink,” says Fulco. “Regulatory compliance could be a driving force that drives change.”

Aellora also has come up with a lamp-related solution: The lamps for its new SureFire TKMP1000 print engine are located independent of the print process. “The reasons for curing off-line are based on productivity-some materials do not cure as fast as others, therefore if your overall productivity suffers because you are printing fast and curing slow, off-line curing can increase productivity,” says Aellora Digital’s Stoudt. In addition, the UV-curing process being independent from the print process also provides other key advantages-it minimizes UV light scatter that prematurely cures inks; minimizes warping of thin sheet materials due to UV-curing; and eliminates tire tracking or banding produced from bidirectional printing, reports Aellora.

Opening new markets
Print providers rely on their day-to-day banner, P-O-P, and display >graphics to pay the bills. But shops are always looking to expand their services to other markets-and new customers. UV-curable printing offers the flexibility to print onto both rolled and rigid substrates, allowing the print provider to discover new markets to conquer. Some of those new markets include: vehicle graphics, textile manufacturers, and more. One of the hottest print markets is vehicle graphics, which was out of reach for print providers who invested in UV-curable printing. Now, however, UV-based shops can offer the traditional advantages of direct-to-rigid printing, as well as the ability to print onto flexible materials for complex vehicle wraps.

The aforementioned Durst Rho 160R, in conjunction with 3M flexible inks, offers companies the best of UV with the vehiclegraphics capability that solvent had claimed for its own.

Several manufacturers offer direct-textile printers, but L&P is the only one (so far) to aim a product-its direct-textile Virtu DirectUV printer-specifically at textile manufacturers. The company is stressing the printer’s high-production roll-to-roll web printing (utilizing large 200- to 400-lb rolls for increased productivity and efficiency) and piece-by-piece strikeoffs (allowing manufacturers to print single pieces for testing, proofing, profiling, or sampling). Capable of 100% bleed, the DirectUV can not only print onto textiles, including those for apparel and home furnishings, but also onto tile, carpet, wood, plastics, and more.

Printing packaging and corrugated substrates is another huge market that most inkjets have yet to break into. While most UV-curable flatbed printers can print onto a variety of rigid media, corrugated cardboard typically used in packaging workflows is another animal altogether. Generally, only machines with powerful vacuum systems can accommodate printing onto typically warped corrugated products without the fear of costly head strikes. Automated loading/unloading options help boost production speed-and the bottom line. Here’s a sampling of UV-curable printers that are taking aim at the packaging market:

* Gandinnovations Jeti 3150UV is a flatbed featuring easy loading/unloading, a strong vacuum, and reporting speeds up to 861 sq ft/hr for printing on corrugated materials.

* MacDermid ColorSpan 9840uv is an industrial-grade, high-speed, UV-curable flatbed printer with pneumatic rollers that hold warped media flat throughout the print zone.

* The L&P Virtu36 and Virtu72, the DuPont Cromaprint 22uv, the NUR Macroprinters Tempo, as well as other UV-cure flatbeds promote their ability to print onto corrugated materials.

* Durst Rhopac, a large-format UV flatbed that's designed specifically for package printers to produce print-on-demand and print low-volume projects profitably; also offers an automated feed-stacker system to increase speed and efficiency.

The ‘Holy Grail’ of single-pass
The ultimate printing experience that makes inkjet print providers drool is single-pass printing, with output measured in linear ft/min. Currently, many inkjet printers require multiple passes to lay down enough ink and hit the required resolution. Single-pass printers, however, are looking to change the lay of the land.

The Inca FastJet is one example of what is on the developmental table. First introduced at Drupa 2004, the FastJet boasted resolutions of 300 dpi and print speeds of 300 linear ft/ min-that’s a football field of print output every minute. Utilizing a stationary or fixed array of printheads, substrates pass under the printheads, ink is deposited along the entire width, and the imaged media moves on to be cured. While the 20.5-in. FastJet, aimed at corrugated business, has not been brought to market, this single-pass printing has laid down the gauntlet in terms of single-pass speed. Also at Drupa, Agfa introduced its one-pass Dotrix, aimed squarely at the industrial print market. The web-fed 4-color press is designed for short and medium-run production, sampling, customized printing, on-press proofing, and variable-data printing. The press is capable of printing 9763 sq ft/hr (linear speed of 79 ft/min) at a resolution of 300 dpi with eight levels of gray, resulting in an apparent resolution of 900 dpi. Recently, the Dotrix has gone modular, offering additional preprinting stations for coating or printing white and post-printing modules that can be added-on include varnishing, slitting, die-cutting, and finishing.

Aellora Digital’s print engines all operate as single-pass printers. Utilizing the company’s semi-solid inks, the 39 x 39-in. SureFire TKMP1000 Digital Printing System offers print speeds up to 250 sq ft/hr in 600 x 600-dpi production mode.

Durst has developed a high-speed one-pass printer that can pass muster with tile producers in terms of speed-and still survive in the harsh environment that is tile production. The Gamma 60 is the first to use the company’s new Synchronized Inline Printing System (SIPS), comprising four full-width fixed CMYK printhead modules matched with a belt transport system whose speed is “synchronized” with the overall tile production workflow. Not only does the Gamma 60 offer a top speed of 13,800 sq ft/hr, but it can also print variable decoration onto the tiles at the same time.

A bright future
What’s holding UV back? A few factors, including: hardware cost vs. solvent, cost of finished graphic vs. solvent, image quality, and gloss surface/dot gain issues, as well as a search for improvements in color gamut and resistance to scratching and abrasions. OEMs and suppliers, however, are busily working on products designed to solve these challenges. Coming attractions for UV-curable printing include:

* Third-party inks are slowly making their way to market. As indicated earlier, Triangle Digital and Sun Chemical offer UVcurable inks matched to specific printers, and Hexion recently introduced its new HexiJet FlashCure inkjet ink, marketed to OEMs. This ink requires a low dose of UV light to “pin” the ink- freeze the ink drop on the substrate; the ink is then fully cured with a lower-than-normal energy source (mercury lamp). Curing at lower energy doses means thinner materials can be used without the fear of warping; it also means that these inks can be pinned at high print speeds.

* Prices of UV-curable machines are slowly but surely coming down, although the cost of a low-end UV-cure system is still higher than a comparable solvent inkjet. The general feeling in the marketplace is that prices on these machines need to decrease to make them available to a wider group of customers.

* As with other print technologies, variable-data printing with UV-cure flatbeds is now in demand. Software must allow a job to be RIP’d once, but with the capability to incorporate personalization on-the-fly. Many users are utilizing their flatbed and rollfed UV-curable machines for smaller, nested jobs, we’re

told, and the ability to incorporate true variable data will likely become more important.

Peggy Middendorf is the managing editor of The Big Picture.