What next for UV?

A flourishing technology indeed - and one that is far from exhausted. Richard Barham, vice-president for inkjet at Agfa Graphics says there are still many improvements to come. This too, is the opinion of HP Scitex CTO Eviatar Halevi who says: “We have not seen the limits of this technology, there is room to grow.”

“Mercury-belt technology has been good,” says Emmanuel Swolfs, international field marketing manager for EFI Vutek, “but we can improve on it.” Heather Kendall, marketing director at Inca Digital, adds: “There will be modification and innovation and we will continue to evolve our products.” So can we expect UV technology for wide-format digital print go from here?

The future is cool
For some the future is orange but for the UV wide-format industry the future is definitely cool - cool curing that is, courtesy of an LED (light emitting diode) light source rather than the mercury arc lamps more frequently used in digital wide-format printers to cure the UV inks.

In actuality, the future is already upon us. Over the last four years or so, a smattering of LED-enabled UV digital wide-format printers have appeared on the market. Inca Digital was the first with its Spyder 150, and has been joined with the likes of Mimaki, where currently four out of five of its UV print engines now use LED; Roland with its VersaUV LEJ-640, Agfa with the Anapurna 2500LED; EFI with the GS3250LX and Fujifilm with the Acuity LED 1600 amongst others.

Within the next five years it seems that LED will supplant existing metal lamp technology. Dr John Kuta, VP, corporate development at Ontario-based Lumen Dynamics Group, which develops high-intensity ultraviolet illumination and LED curing products for the digital print industry, says: “There are a number of macro forces at play that are all pushing large-portions of the wide-format digital print industry towards UV such as environmental considerations around VOC emissions, application diversity and print shop profitability.”

Advantages of LED
LED brings a number of advantages to wide-format digital print production. As Barham at Agfa points out, LED is the lowest energy consumer out of all the digital wide-format technologies, considerably less than solvent, and less again than the energy-hungry aqueous-based machines.

Duncan Jeffries at Hybrid Services, Mimaki’s exclusive distributor in UK and Ireland, points out that for the Mimaki printers, they can be plugged into an ordinary socket - reducing significant amounts of energy consumption.
But reduction in running costs goes beyond the mains. “LED bulbs last much longer than arc lamp bulbs, having a life span which,” says Kuta, “is greater than five times longer, leading to a lower cost of ownership for LED enabled technology.”

LEDs are either on or off, they do not require warm up or cool down times, neither do they need shutters. LEDs are lighter in weight and unlike arc lamps do not require high voltage ignition to get them started and keep them running. The upshot of all this means simpler printer architecture, simplified electronics, the need for less shielding, and fewer moving parts which all in all means lower costs and maintenance. Oh and yes, it gets a big tick for its environmental credentials.

One of the benefits of LED is that generated light is concentrated in a narrow range of the UV spectrum – since it does not generate visible and infrared light, it products a much cooler cure.

Temperature sensitive materials
UV has always had problems with temperature sensitive materials due the high temperatures required by traditional mercury arc UV lamps to cure the ink. This is about to change.

“It’s the great hope,” says Hybrid’s Jeffries. Temperature sensitive materials such as shrink-wrap films, the more popular graphics boards and lighter weight PVCs (which will bring down costs and be better for the environment) for example are no longer an issue for UV digital printers.

The ability to handle thin and super-thin films will open up a number of new specialist market areas for digital printers, such as food packaging and proofing.

High speeds, full cure
In these early days of LED UV there has been concern – especially with high production printers – over how to ensure you get a full ink cure. New high-powered LEDs have been developed over the past three years but with these, a liquid cooling strategy had to be implemented which created added complexity for printer architecture. Just this past year, new high-powered air cooled LED systems have become available, offering all the benefits of the technology without many of the headaches of water cooling.

UV LED inks are demanding fluids. Not only do they need to have a wide-colour gamut, be stable, weather resistant, scratch resistant and flexible as well as strong adhesion, they need to be surface and bulk cured and odour-free.

Ink suppliers have been rising to the challenge. “Over the past three years there have been remarkable enhancements in ink chemistry responding to LED printers,” says Kuta, adding: ”We work with many ink vendors and have sampled all the major suppliers. Working together we have reduced the amount of energy required for a full cure by up to four times. With the high power LED now available, these inks can cure at the speeds achieved by commercial printers today”.

Swolfs of EFI says that its new Vutek LED production printer, the GS3250LX launched earlier this year, hasn’t compromised on speed or quality. The system boasts productivity rates of up to 223m2/hr (2,400 sq.ft/hr) and 55 1.2m x 2.4m (4’ x 8’ ft ) sheets per hour.

EFI’s trick in maintaining the high speeds indicative of its GS range, says Swolfs, is down to a unique way it uses the LED light source – eliminating oxygen between the printheads and substrate by blowing nitrogen to clear it.

Printheads and inks
Naturally, printhead technology will continue to improve, becoming more productive with faster jetting speeds, and more nozzles, with the price per nozzle becoming cheaper. Ink drop sizes will become smaller and we’ll see native resolutions rise.

UV ink technology has continued to improve to meet the challenges of wide-format print output from the word go and continues to do so. Four years ago or so, UV inks would have been unsuitable for fleet graphics and car wrapping applications. Today, this is no longer the case. So ink chemistry will continue to develop with incremental improvements in flexibility and adhesion.

Derek Joys, business display graphics programme manager at Océ, says he expects to see spot colours, varnishes and prime colours as a matter of course.

Historically, UV inks for digital wide-format have been somewhat generic, able to cope with a wide range of applications. Inca’s Kendall, says that as wide-format businesses mature, a need for tailored, more specialised UV inks for those running dedicated machines might well arise. She expects to see this requirement to arise from non-graphical applications such as door printing, specialist sports equipment printing such as skis and the fashion industry, the type of work historically carried out by traditional screenprinters.

Not a machine, a whole print factory
With decent margins becoming more difficult to come by, the trend towards wide-format UV printers becoming fully functioning centres of heightened efficiency will start to gain momentum.

Time is money and building MIS systems around your printer is going to make sure you can optimise your profitability. Workflow - how jobs can be planned into the production schedule, what impact rush jobs may or may not have on your planned workload for that shift - will become very attractive. Things like handling, says Kendall, will become even more significant; how materials are loaded on and off the printer will become part and parcel of a fully automatic way of working which starts from a quote all the way to delivery of a final product.