Many of us consider LEDs to be relatively recent innovations but, in truth, they've been around since 1907 although their practical application only started to evolve some 50 years ago. Today they have become increasingly topical as they make inroads into UV-curing options for industrial and display printers.

Until now UV-curable wide-format printers have largely relied upon mercury arc lamps to dry their output. These have migrated from the screen-printing and flexo sectors, significant in bringing this technology to the digital arena, but their downside is that these lamps generate high heat during the curing process. This is contained within the printing machine and also affects the material being used.

Because of the intensity generated by broad spectrum UV lamps, there has been criticism with some print jobs' output, particularly onto fine and delicate substrates. Combined with tricky adhesion and the possibility of the ink crazing, cracking or flaking off, mercury arc lamps haven't been a universal cure-all.

EFI's VUTEk GS3250LX features LED curing in a production platform

Thus, the advantages perceived in using LEDs are now becoming reality with engines coming to market that incorporate this technology. Unlike their traditional counterparts, these lamps don't have a finite life of around 1,000 hours with a light that degenerates during use. Although LED lamps are initially more expensive, this is compensated by their consistent output and extremely long life, and their functionality means they can be turned on and off without a warm-up time and with no need for shutters.

LED curing lamps generate light within a narrow range of the UV spectrum so there aren't the same problems inherent with heat, hence the term 'cool cure'. This has significance to display producers who want to work with traditionally tricky and sensitive materials without fear of buckling or surface damage to the media.

These lamps, because of their fabrication and operational criteria, also have a reputation for being more reliable than their mercury arc counterparts and are easier to integrate into a system design and build. On the environmental front, energy consumption is reduced and there are no ozone emissions.

Nonetheless, there are compromises when incorporating LED curing lamps into an UV-curable printer, such as their lower energy and narrower UV spectrum. Today's refined ink formulations account for the idiosyncrasies encountered with the lower optical power density and more limited irradiance in LED technology. But these inks need to be able to provide consistency for the end user, with adhesion and stability being key, along with colour accuracy, flexibility and low odour. What this means is that, for chemists, these products need to be able to cure at a lower energy level without compromise, and to achieve this at respectable speeds.

In the wide-format sector, probably the first platform to be trumpeted with LED curing technology was the Russian Sun Company's Neo which originally came out of the Chinese Infiniti conglomerate. Sun has continued with this type of curing in later machines and has, of course, been joined by well-known names in the wide-format sector.

One of the early successes subsequently came in Roland DG's VersaUV print-and-cut machine which, once it found its feet and developed its full potential, has now proved to be a valuable addition to the packaging and short-run label markets. Thanks to its LED curing capabilities, this engine can happily print direct to fussy end materials, emulating proofs and prototypes onto the final media.

Mimaki, too, has pursued the LED route with one its best-known machines being the novel UJF-3042 desktop unit, which wouldn't have been so easy to develop had it incorporated traditional curing principles. This move to more compact UV-curable systems has also been taken up by Roland with its LEF-12, another compact solution.

Now we're witnessing LED curing making more of an impact on the wide-format arena, with Mimaki already having incorporated this technology into its UJV-160 models and with its flat-bed JFX-1615plus and JFX-1631plus. But perhaps the greatest acknowledgement of the relevance of this technology to the production sector thus far is with EFI's VUTEk GS3250LX, a 3.2m combination platform which was introduced to the market last year.

This technology's growth in industry is endorsed by the recently formed LED Curing Association whose founder members, Integration Technology Ltd, Lumen Dynamics and Phoseon, are all familiar names within the graphics industry as well as other arenas. These companies acknowledge the fact that greater insight is needed into the potential viability for making the transition to LED lamps, and we can expect to see more print engines to accommodate them in years to come.