The biggest criticism about new generation UV printing concerns the cost of the ink. Printers used to commodity pricing for their inks, though prepared to pay a little more for the high pigment inks needed for ISO 12647-2, are baulking at the cost of the new style inks, whether for Komori’s H-UV and Heidelberg’s LE-UV system or the increasing number of LED UV systems. One printer who had considered an H-UV Komori says simply “We print a lot of long runs.”
It is a criticism that Jim Buchanan takes on the chin. He is Flint Ink's global UV product director for sheetfed inks, putting him right at the heart of the LED UV evolution. “Too many people are focused on cost, of the ink and of the LED arrays needed.
And there will always be an element of people that just see the inks as more expensive,” he says. “But you have to look beyond the immediate costs and understand the applied costs to get the full picture.”
He points to large online printers in Germany which are now using LED UV systems in order to achieve quality and service targets. These are companies using large volumes of ink, so for them the calculation pays off.
This is because there are advantages to new generation UV that mitigate the initial costs. Some are well known: there is no need for an aqueous coating and possibly no requirement for a fifth printing unit; on absorbent stocks less ink is required because UV ink is cured on the surface before it penetrates into the paper fibres; the energy required for drying the job and therefore its cost, is slashed.
Less obvious savings include storage space for work in progress that is drying slowly, no spray powder to buy or clean up; reduced use of blanket wash and faster cleaning of the press at the end of a week. It is too soon to say whether machines without spray powder will need fewer call outs, though logic suggests this might be the case.
And Buchanan says there is plenty to suggest that printers want to see beyond the immediate cost, even if ultimately they cannot manage to do so. “It’s fair to say that people who have been sitting on the sidelines are now taking the plunge,” he says. “UK printers have been slow to take up the new technologies, but everyone I am talking to about investment in a new machine has LED UV as one of the options.”
Flint supplies the handful of companies that have LED UV machines in operation in the UK currently. These cover the range of AMS, Panasonic and Baldwin systems. It also anticipates being able to supply any future systems, from IST for example.
Flint will be at IST’s UV Days 2015 in June where the company will be running a press using its own LED UV to cure four-colour printing and standard UV lamps to cure a range of finishing effects over the four-day event.
Flint is not a newcomer to LED UV. It has been producing these inks for narrow web flexo presses, including food safe, low migration versions for some time. Now it is to concentrate development and production at Trelleborg in Sweden as a centre of expertise for the technology. Its scientists will be working on existing and new materials to create the ecosystem around LED UV to take it into new applications.
For example, the company is working with a corrugated board printer to add a UV cured varnish on top of four-colour water based inks. It is also working on web offset applications where UV curing takes the place of the oven to dry the inks. In commercial sheetfed, printers using new generation UV are able to print on plastics and other non absorbent substrates.
There is plenty of scope first in the commercial print arena where Flint finds itself competing with Japanese manufacturers. Of these Toyo has the muscle through its ownership of Arets to produce in Europe. Sun Chemical, Flint’s great worldwide rival, has UV cured inks, but is not active in the UK at least. Which is fine by Flint.
The second accusation laid at LED cured inks concerns some of the pigments used and their sensitivity to the UV wavelengths the LEDs generate. For this reason H-UV has been seen as the safer technology. However, this is out of date information, says Buchanan. “LED UV is 100% viable now,” he says. “The system will go in and it will do the job. There are no limitations on inks and varnishes now.”
At the outset, LED UV-cured varnishes were associated with yellowing, but work with different chemicals, with bleaching and brightening agents are removing the problem. Likewise, he says, there are no limitations to the colours that can be printed and cured.
The only proviso to this are metallic and fluorescent inks “which are problematic in conventional UV versions. It’s not a problem inherent to LED UV,” he says. Nevertheless Flint continues to push its suppliers for new materials to extend the scope of LED UV.
This is especially true for packaging inks where there is a focus on bringing out a low migration LED UV cured ink. It is not impossible as Flint has created a flexo ink for label printing that is low migration and LED UV cured. The sharing of ideas in Trelleborg will come up with an answer using molecules that are too large to pass through the board or into unwrapped foodstuffs.
“We have been testing low migration inks for a year, both internally and with the regulatory bodies, so I’m confident we will have a low migration answer.
“This is not necessary on many types of packaging where the hybrid approach using LED for interdeck curing and conventional lamps for end of press curing is gaining pace. The first unit can print white for example, and once cured provides a base for over printing with the process or special colours ahead of a standard UV system in the delivery,” says Buchanan.
In packaging, Buchanan reckons there are strong advantages to running with LED UV. First the technology is inherently stable so there will never be concerns about the amount of energy reaching the ink or coating.
Mercury lamps lose power over time and will tend to be replaced whether necessary or not because the printer has to be able to guarantee a full cure.
The diode by contrast is a binary technology, either on or not, so always delivers the same amount of energy. The cold operation of LED expands the range of substrates a carton printer can print with confidence and this can also be beneficial in boards where heat, while not enough to cause distortion, may create internal reactions. “We believe that there will be some really big benefits in food packaging from using LED UV,” he explains.
A retrofit market to equip presses with LEDs already exists, led by AMS, and will expand, bringing a way to adapt older presses for today’s market conditions.
The small size of the LED arrays simplifies the engineering required and the power that the diodes now generate means they do not have to be positioned as close to the surface of the substrate. There is no ducting needed to remove heat or ozone because none is generated.
However, there is a steep learning curve, even for printers with previous experience of UV inks. Rollers need a harder surface, fount chemistry may need changing and printers will need to look out for misting, Buchanan warns.
“These inks will mist slightly more than conventional inks at speed because of the nature of the ink,” he says. “But it’s not always there. I have seen an eight-colour perfecting KBA Rapida 106 running with zero misting or ink fly and a similar press where there was a slight issue. One was running with IPA, one not. But from a performance point of view there was no detrimental effect.”
In all cases it is a collaborative effort between ink supplier, press manufacturer, lamp provider and printer to reach the solution.
Huber offers H-UV alternative
If Flint is the alternative provider to the Japanese ink companies for LED UV, Huber Group holds that position for H-UV.
The process was developed between Komori Baldwin and Toyo, but recognising that Toyo is not well established in Europe, Komori has endorsed Huber's inks to provide an extra supplier, even if printers are sticking with the recommended set ups in the initial phase of operation.
Instead of LEDs, H-UV uses a single doped mercury lamp and ink that is tuned to cure at the UV wavelengths generated.
New generation UV technology has become almost universal in Japan with H-UV leading the way in Europe. In France it is used extensively on high value packaging for the cosmetics sector.
Food packaging will follow. Huber is working hard on a low migration ink that fits the H-UV system. The advantages to carton printers of being able to replace banks of UV lamps with single-lamp systems are immediate.
Flint supplies the handful of companies that have LED UV machines in operation in the UK currently.