Xeikon has applied for patents for a new approach to UV curing inks, DuraCure, which it has developed for its Panther series of UV inkjet label presses.
Essentially, Xeikon has used a combination of LED and mercury vapour curing. The presses lay down white ink first, which is then pinned with an LED array, followed by the CMYK inks, and a second LED pinning after the black ink. Pinning is a fairly common technique in inkjet presses, especially in the label sector, where a short burst of UV light is used to deliver a partial cure, usually to stop the inks from bleeding. And, of course, it makes sense to pin the white ink so that the other colours can be printed on top.
After the second pin, the substrate passes under the main cure, which is a combination of first LED UV at 395nm followed by a lower amount of Fe doped Hg UV light. Dr. Lode Deprez, Xeikon’s vice president of Digital Technology, explains: “This gives a better performance in curing, with lower temperature increase of substrate and less colour sensitivity and good uniform gloss.”
This is certainly an interesting approach to the problem of curing. Most vendors are moving to LED UV curing where there a number of advantages, namely that LEDs use less power and last longer so that there’s no need to replace the arrays regularly or to cope with the fading power as the lamps wear down. And there’s also European regulations outlawing the use of mercury that are forcing printer vendors to develop LED curing solutions.
But there also some disadvantages of LED curing, which work on a narrow wavelength. We want to cure both the surface of the ink drops and the body of that drop but most LEDs tend to be good at one or the other. This isn’t a problem with conventional lamps, which blast UV light through the ink but create a lot of heat in doing so, which in turn affects some substrates, particularly thinner films.
So with DuraCure, Xeikon is using an LED array to reduce the amount of heat that the mercury lamps produce, and presumably also to extend the life of those mercury lamps. At the same time, the mercury lamps are ensuring that the ink is fully cured. This does not affect the speed of the presses, which is still 50mpm.
Jeroen Van Bauwel, Director Product Management at Xeikon, explains: “Good curing performance is an important factor when looking to invest in UV inkjet printing technology. The quality and durability of DuraCure expands the capabilities of this printing technology and makes it a very attractive opportunity. The new DuraCure technology can achieve optimal curing for a variety of applications, it combines with our PantherCure UV inks and substrates to achieve the highest quality results and provide added value business opportunities for our customers.”
This system is being fitted as standard to all new Panther presses, but can also be retrofitted to existing machines.