Until there is an agreed standard or uniform way to dry water based inkjet inks, Adphos is the hottest name in town. It is the chosen supplier to Kodak, has its technology on Screen’s TruepressJet and on HP’s largest inkjet presses like the HP1195S for corrugated packaging. Where industrial level performance is required, Adphos is there at the top of the list.
The technology it has pioneered is Near InfraRed, where the lamp units produce energy at a wavelength that is tuned to excite water molecules and release these from the ink, effectively evaporating them. Crucially there is almost no heating of the material being printed, useful for printing on paper substrates and absolutely vital for packaging on thin films when any excess heat will exceed what is known as its thermal barrier and will result in distortion. Moreover NIR is far more controllable and tunable to different substrates, applications and ink levels. In drying it is a digital alternative to techniques like impinged hot air, a lengthy hot air dryer or heated drum, or any of the other approaches that inkjet press suppliers currently use.
These choices each, says Adphos chief executive Kai Bär, reflect the background of the companies producing the presses. So Canon and Ricoh are companies that have their roots in CRDs and laser printing where top speeds are 30m/minute. Consequently, switching to inkjet brings an immediate increase in productivity even if press speeds seem limited compared to some. The initial goal was to replace laser with a faster cheaper technology, not necessarily hugely better in terms of print quality.
Today, at its highest resolution, Canon’s ProStream 3080 still runs at 80m/min; this becomes 133m/min for the ProStream 3133.
Those with a stronger commercial print background, Kodak and HP for example, tend to run faster. Screen, with similar origins to Ricoh in terms of press design, can reach 150m/min, more in keeping with its commercial print heritage. HP and Kodak are both at this speed with full resolution from their presses though with reduced resolution, the Prosper Ultra 520 can run faster and the Prosper 7000 Turbo faster still. At these speeds, getting rid of litres of water per minute landing on the paper, becomes very, very important.
The choices made at the outset of new press projects may no longer be appropriate, particularly as the cost of energy has risen sharply. It has also led to some adjustments from developers, says Bar.
HP’s new press, the Advantage 2200, is designed for the widest possible litho to inkjet market. It uses HP’s Brilliant Ink for high impact colour. However, this has a reduced level of humectant and so requires a pre coating on the paper to run well. HP has explained that the drying configuration, using impinged hot air and varying lengths of dryer, reduces the energy input required compared to its previous machines. A user picks the set up to suit his application and if that changes, so too can the press up to high coverage on coated papers, the highest challenge of all. Adphos wonders if even the full drying will be up to the task.
“We will be watching to see how the system is progressing in the future,” says Bär. “We are already getting inquiries about achieving performance on certain applications and substrates where the user is struggling to get the specified performance.”
Adphos has experience of HP’s more challenging applications having its technology on the 2.8 metre wide T1100 family of machines and the T700i for corrugated and now also carton printing.
James Burbidge, Adphos’s man in the UK, points out that touch dry may not be completely dry in terms of finishing processes and so may not offer the durability in the ink that’s required. The drying solution needs to dry through the ink, not leave a layer of wet ink beneath a touch dry surface skin.
This can be the case when binders in the ink are used to create a linked lattice to trap the pigment and prevent absorption into the paper. These need more energy to trigger the linking effect, but can print on papers without a primer. Ricoh dropped the need for priming with the Pro VC70000, but with the upgraded Pro VC70000e applies a priming layer again.
Likewise Burbidge is unsure whether reducing the amount of water in an ink will work. Some have reduced the percentage of water by increasing the percentage of a glycol based humectant, which has a higher evaporation point than water and so needs more energy to remove and which can also have a deadening effect on the ink’s appearance.
“There are restrictions in the ink because of the need for low viscosity for the print technology, thermal especially. This may change; Xaar is introducing a high viscosity head which can carry double the weight of solid pigment and half the amount of water. The question is will this be useful for commercial printing where water is needed to help form the image?” The reaction between ink and substrate is important. “Each technology has its advantages,” says Bär. “We can’t say which is superior. It will depend on the applications being printed.”
What he can say is that the Adphos technology is relatively agnostic in terms of print technology. It can be tuned to the inkjet technology, the ink and the application in use. Settings can be adjusted according to the ink levels and job, or can be matched to suit conditions.
If energy costs remain high, as most predict they will, there is sure to be increasing interest in what Adphos can achieve. According to Bar this can be half the energy consumption while enabling twice the throughput on a press. Where performance matters, Adphos is firmly in place, with those corrugated machines for example.
In the highly competitive commercial market where press cost can decide what the printer decides on, the debate rages on. Burbidge says: “The market is becoming more aware and there is more knowledge out there among printers. There’s movement in what is considered to give the best performance and as an industry we will get there through trial and error.”
In short time will tell. In the meantime, anyone delving into inkjet printing needs to understand the drying technologies being used.
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