But not anymore. Whereas for the past decade or so, large-format inkjet printing companies have had to choose between solvent and UV for their roll-fed vinyl labels and outdoor banners and signage, this year has seen the introduction of hybrid inks from both Mimaki and Colorific. These claim to combine the best of both worlds.
The problem with solvent inks has of course always been the hazardous VOCs involved. The print remains unpleasantly smelly for weeks after printing, so cannot be used for indoor applications. And working with these inks requires good ventilation systems to be installed to stop your operators from keeling over.
On the plus side, solvent inks are very flexible in both the sense of being bendy and versatile. Solvent colours are also bright and the print is durable enough to survive for up to five years outdoors.
Unfortunately, past attempts to minimise the hazardous nature of these inks have compromised brightness and durability. In the early 2000s, manufacturers introduced light solvent inks (also called eco-solvents), with little or no hazardous VOCs and no smell and suitable for indoor and outdoor applications. But they didn’t suit all for the aforementioned reasons.
Meanwhile, UV inks have never been associated with unwanted fumes and so are fine for indoor use. And, with prints instantly cured and so not requiring an outgassing period, these can be finished and delivered immediately.
The downside is that this formula, based on a photopolymer fluid that responds to ultraviolet light by instantly solidifying, though sticking to virtually anything and so suitable for a wide range of applications and highly durable, is pretty inflexible. Likely to encounter cracking issues, printers can’t as a result use UV inks for flags or vehicle wraps with very tight curves or deeply indented panel lines, for example.
The dream solution is, then, to take advantage of the biggest benefits of each type while mitigating some of the drawbacks, producing an ink with no nasty fumes but still bright, durable and flexible.
As the name suggests, SUV (solvent-UV)inks are a mixture primarily of UV curing polymers carrying the pigments, with a small amount of solvent that in effect dilutes the polymer and also helps to key it to media’s plastic surface. Heaters in the printer bed evaporate the solvent component after printing, locking the ink in place long enough for it to reach the UV lamps for the final hard cure.
Standard UV inks are quite viscous, with a tendency to cure with a raised or ridged surface. The solvent-UV mix lowers the viscosity to give a much thinner, smoother ink film, says Shaun Holdom, business development manager at Colorific. “It’s a very glossy print, unlike a normal UV print that can be flat and dull,” he reports.
Detail differences
Neither Mimaki nor Colorific will confirm where their inks are made, citing confidentiality agreements. Mike Horstern, general manager of marketing at Mimaki EMEA, says his company’s formulation is different in detail from Colorific’s and is tuned to its own printers. “It has been a joint venture with the ink manufacturer. I can’t say more at present.”
The two inks’ similar characteristics indicate that they’re likely to be from the same source however. Another ink dealer has said that the manufacturer is Fujifilm Speciality Ink Systems in Broadstairs (the former Sericol), but none of the parties has been willing to confirm or deny this.
What certainly differs from one vendor to the other is their approach to rolling these SUV inks out. Mimaki is offering its SUV ink in its new JV400SUV family of 1,371mm- or 1,620mm-wide printers, introduced this summer. This has eight ink channels for double-CMYK and a running speed of 6.6-18.1m2 per hour depending on quality settings.
Regarding running costs for the new model (priced at £17,995 for the 1.3m and £19,995 for the 1.6m), John De La Roche, sales director of Mimaki’s UK distributor Hybrid Services, says: “We’re still doing tests, but if you asked me to quote now I’d say that the running costs are similar to a typical JV33 light solvent printer. But it’s the time you save too. You don’t need to de-gas, you can finish and ship it right away. It’s complete off the machine.”
Mimaki customers now, then, have the choice of opting for this SUV model or the JV400SUV’s sister model, the JV400LX, which uses Mimaki’s latex ink. This shipped earlier this year with eight ink channels for CMYK, orange, green and two white channels, and Ricoh greyscale heads. The price is the same as for the JV400SUV.
So how to choose? “They’re for very different purposes,” says Horsten. “You’d use SUV for outdoor use – it’s very bright, very weather resistant – it’s got extra orange and green inks for 95% of Pantone colours, and we’re seeing it used for proofing, interior design, wall coverings and in Russia for frescoes.”
De La Roche says: “If a customer is looking for a very eco-friendly printer or maybe specialising in indoor graphics and vehicle wrapping, then latex may be the way to go. But once they see SUV inks a lot of customers are blown away and say that’s the one they want. It’s a smooth flat image, very high quality, it looks like it’s been laminated and it’s very tough. The colours are stunningly vibrant.”
While Mimaki has so far limited SUV’s use to just one printer, Colorific offers solvent-UV aftermarket conversions with its own add-on Lightbar curing lamps. This is available for a wide range of existing inkjets that use OEM Epson heads, starting with the Roland DG models but now covering Mimaki, Mutoh and Uniform models. Even quite old models can be converted to its hybrid UV-Light ink, available in CMYK, light cyan and light magenta. The Lightbar comes in 54in or 64in widths and has a vertical slot that the media roll is fed through, with a shielded UV lamp tube.
Affordable upgrade
“Our approach is that it’s an upgrade to an existing unit, given the financial climate,” says Holdom. “It gives customers an upgrade to achieve something that previously they couldn’t do without buying a new machine. Most machines will have been paid for, so for a small outlay they can get into a new technology and reduce their production costs.
“We’ve pitched the whole price in the bracket between £2,000 and £3,000 so it can be a credit card purchase, that doesn’t require too much thinking, or the sign-off from a board of directors. It can be simply classed as an ink upgrade or an ink sale and it should return savings quite quickly in a number of months.”
The standard £2,500 Lightbar is for Roland printers and the Mimaki JV33, where it bolts onto the front legs of the printer and takes on-off signals from the vacuum circuit. For printers that may not be able to take the bolt-on Lightbar, Colorific has now developed a ‘roll-up’ unit with a stand, for other types of printer. It costs £3,000, but is identical in use.
The printer’s RIP software is modified slightly so that after printing it feeds the roll an extra 500mm to pass through the Lightbar, then reels it back to be guillotined or contour cut.
Colorific’s UV ink cartridges cost £79 for 440ml, which is around the same as the manufacturer’s original eco-solvent cartridges, according to Holdom. “With UV a lot more of the ink is actually printed, whereas with a solvent ink a lot of it is evaporated away,” he points out. “So the cost per square metre is between 30% and 40% less for the hybrid UV ink for a given area and you get the added UV benefits of print being immediately ready to finish and deliver.”
Holdom says the outdoor durability of the UV-Light pigments is three to five years, the same as normal solvents.“Where you do benefit with UV is the abrasion resistance, scratch resistance, which is dramatically enhanced compared with eco-solvent. This reduces the requirement for lamination for the majority of applications.”
It seems, then, that both manufacturers have achieved the holy grail for large-format printers: an ink that is both VOC-free but also bright, durable and flexible enough for flag and particularly challenging vehicle wrap use. As such it doesn’t seem likely that Mimaki and Colorific will be alone in this market for too long. John Harper Smith, marketing manager for packaging applications at Fujifilm Europe, has, for example, confirmed that Fuji is working on a different water-UV hybrid ink for its own forthcoming Jet Press F digital carton press.
For now of course printers will have to choose, depending on whether a new install or rather an upgrade option will suit better, between the Mimaki and Colorific offerings. And both seem set to prove mum and her ‘you can’t have everything’ maxim, wrong.
