While not as profound as that, new water-based inks cured by UV may be a building block for inkjet’s evolution and expansion into new markets.
The story so far
At Fespa 2015 last summer, water-based UV (WUV) technology was announced by inkjet equipment firm Durst and ink giant Sun Chemical’s inkjet division SunJet.
Durst showed its water-based UV ink under a broader banner of water-based inks that it brands Water Technology (WT), which also includes the inks used in its Rhotex textile printers. Its WUV ink was running in 2.5m-wide hybrid (roll-to-roll and flatbed) machine the Rho WT 250 HS capable of running at 400m2/hr.
SunJet announced Aquacure, its WUV and showed samples, although not live production. It also showed it as a proof of concept at LabelExpo. Aquacure is not Sun’s first WUV product, although it is its first in inkjet. A decade ago it launched its WetFlex and UniQure flexo inks. They are used in a couple of niche applications, but WUV never became a mainstream technology in flexo.
Neither Durst nor SunJet will confirm if WT and Aquacure are in fact one and the same technology. The specifications and the messaging used by both are very similar and it’s no secret that Durst uses Sun UV ink, so it’s highly probable that Durst is the first firm to use Aquacure.
SunJet and Durst are not the only firms looking at the technology. A WUV ink was announced by Fujifilm at Drupa 2012 as a key enabling technology for the folding carton variant of its JetPress B2 sheetfed inkjet press. It continues to develop WUV inks for packaging and graphics applications, but hasn’t revealed any concrete details about any products or the timing of their introduction.
It’s also on other vendors’ agendas, just not, as yet, at a stage where they are able to add much detail.
“We are looking at new variants of UV ink, but it’s too soon to say anything definitive,” says EFI inkjet solutions vice-president, marketing Ken Hanulec. “The general trend is to get any bad stuff out of our ink and, for packaging applications, to develop low-migration formulations. A water-based UV ink is of interest to some extent.”
The challenge is that the monomers in current UV formulations are toxic to plants and fish. As the restrictions of REACH get tighter and are applied to smaller batch-sizes of materials, there will be regulatory pressure. Current inks will be re-labelled as hazardous materials and any quantity greater than five litres will face restriction on transportation, such as the need for additional paperwork and the use of regulated couriers.
“We saw that the UV landscape was changing with the impact of REACH, and not in a good way,” says SunJet global sales and product manager Richard Hulme. “There are also limitations in what can be achieved by conventional UV-cured inks.
“Other vendors are addressing some of those limitations with developments such as solvent UV (SUV) in the wide-format market, we realised we should also be addressing those limitations.”
SunJet director of global digital technology Nigel Caiger looked at the overall picture and decided that whatever the firm did would be water-based.
Over at Fujifilm Speciality Ink Systems (FSIS) they were coming to a similar conclusion.
“A key driver for our focus on WUV is the low odour and good safety profile that our patented WUV technology provides, which will be a key advantage for both graphics and packaging,” says technical manager Carole Noutary.
WUV love
“It’s a game-changer,” says Durst UK managing director Peter Bray. “It has the look and feel of litho thanks to the very thin ink film. We’ve had a lot of interest in water-based inks both from our existing customers and new prospects. For example the companies that currently use the Scitex TJ series machines for posters.”
That thin ink film is due to the high volume of water in the formulation, which evaporates, leaving less material on the surface of the print. Typical UV ink films are 8 microns thick. With 60%-80% of the volume of the fluid evaporating WUV inks will be three microns or so thick.
“Thin film is important for packaging,” says Hulme. “Conventional print with its thin ink film is accepted. The big problem today with inkjet is that it’s got a relief that is not accepted by agencies and brand managers.”
The thin ink film is also very flexible, reducing cracking and flaking. Water as the solvent means low odour. All the firms are working on formulations with low migration, which is important for food packaging, including gaining the necessary certification and approval, such as that required by Nestlé.
Packaging will likely be the biggest market eventually, but graphics will be the first adopter because today’s scanning inkjet and UV curing systems don’t need much adaptation.
Noutary at FSIS says that the main market for its WUV is as an alternative to latex due to its lower curing energy and maintenance requirements. This would be a natural step from the firm’s introduction of SUV and the hardware required is very similar. While SunJet says Aquacure is suitable for this sector of the market, its initial focus – like Durst’s with the WT 250 HS it has already demonstrated – is at the higher end of the market. In fact, Bray suggests WUV will be part of the firm’s approach for single-pass production.
This is another pointer towards the ultimate aim of WUV: as an enabler of digital packaging, with single-pass seen as being crucial in enabling inkjet to challenge flexo in flexibles, and corrugated.
Corrugated is a space that many of the digital vendors have their sights set on including Fujifilm, Durst and EFI.
To date their offerings have been based around standard UV inks used in their wide-format for graphic sign and display. HP has made the most headway in the corrugated market. It offers two product ranges, one based on its UV flatbed machines, the other on its high-speed inkjet T-series, which uses water-based inks.
Economics is important; EFI’s Hanulec hints at the rationale of WUV for these high-volume and more price-sensitive markets: “Water as a carrier is cheap, it changes the economics of the ink significantly.”
While water may be part of the solution (not much of a pun intended) it is also a problem. As with other water-based inkjet systems getting the water out is a challenge, requiring heat. Durst’s demonstration had a heating and extraction unit “the size of the printer” at Fespa Digital. And while it promises that production machines will use an integrated dryer, any potential user should look closely at the energy costs for the dryer as part of the total cost of ownership.
SunJet has confirmed it will be showing Aquacure at Fespa, while Durst cited keeping its powder dry for the show as a reason for not contributing more to this article. The first products based on WUV are likely to be available in the second half of 2016. Unlike the billions of years it took the primordial soup to become intelligent life, this new ink is rapidly evolving and you don’t need a time machine to see it, just a plane ticket either for Fespa in March or Drupa in June.
HOW IT WORKS
SunJet Aquacure
As the name Aquacure suggests this new ink combines water as a carrier with UV-curing. A more generic description would be water-based UV (WUV), which is how Fujifilm referred to the inks for its proposed packaging variant of the JetPress.
SunJet defines any ink with water content in excess of 50% as being water-based. The other major constituents are monomers, which cross-link and harden when exposed to UV and the pigments to provide colour.
Following printing there is a two-stage curing process. The first step uses heat at 50-60°C to drive off the water, while the second step uses UV to harden the remaining film of monomers.
Evaporation of the water starts immediately causing a skin to form on the ink, which SunJet claims means the image quality is very high.
“You can think of this as thermal pinning,” says SunJet global sales and product manager Richard Hulme.
Existing technology such as the heated platens used in wide-format solvent printers are capable of providing the heat needed for evaporation. There does need to be an extraction and condensation unit to remove the water driven off.
The UV-cured component is very small. Also it doesn’t have to be cured by UV, it could be cured by an electron beam (EB) system, as was the case in the analogue predecessor WetFlex, which may be attractive for some packaging applications.
