JITF — Sitech shows self-drying ink
The Taiwanese ink manufacturer Sitech has been showing off its Self Curing Aqueous Pigment, or SCAP, ink at this year’s Japan Inkjet Technology Forum (JITF).
The main promise of this ink is that it can eliminate the need for costly drying systems, which can cut the price of a press as well as its running costs. And of course, eliminating the drying should also make for more compact print devices, which is always welcome.
The SCAP ink works with absorbent materials such as paper and textiles, including cotton, nylon and polyester. In terms of paper, Jason Wu, CEO of Sitech, says that it’s more likely to be used where customers want to also print coated papers, which are less absorbent and so more challenging to dry with other types of ink than uncoated papers. It will work with some absorbent plastics, such as TPE which is used for some yoga mats, but is not suitable for plastic-based media such as flexible films.
The drying process is in two stages, as Wu explains: “The droplets of ink are very small and the surface area is large so during the jetting, some of the mist from the water will be evaporated before it lands on the paper and the rest of the water will be absorbed into the paper or fabric. Once the water has gone, that triggers a chemical reaction.”
This chemical reaction cures the ink, binding the pigments to the substrate. It relies on the interaction between nucleophilic and electrophilic elements, where the nucleophiles donate their excess electrons to the electropholes to form a bond, binding the pigment to the media.
The ink contains one of these elements, with the other being present in the paper or fabric – Wu won’t say which way around they are other than to note: “We have been selling chemicals to paper makers for the last 40 years so we know how these materials work.”
Wu says: “The first reaction is very quick. It’s cured within milliseconds.” However the curing speed depends on how fast the water can be absorbed into the substrate, since the absorption triggers the chemical reaction. There’s no need for not air or for UV lamps and the ink does not contain any polymers.
The SCAP ink is available now in a range of colours including CMYK, light cyan and light magenta, orange, green and violet as well as white though Wu says that it’s up to the printer manufacturers to determine the exact inkset. The white ink requires recirculation in the printhead because of the sedimentation issue – where the heavier titanium dioxide white particles sink to the bottom of the tank – which is a common problem for most white inks.
One other issue is that it has a very low viscosity – lower than many printheads expect as standard. Wu says that it will work well with Epson heads as well as Kyocera and Ricoh. It will work with both piezo and thermal printheads.
The other drawback is that the raw materials are expensive, meaning that it’s not the cheapest ink available. But of course the cost depends on the volume of ink used versus the savings on not using energy for drying.
I will cover more stories from this year’s JITF over the next few days. In the meantime you can find further details on the SCAP ink from sitech-ink.com.
(First published on www.nessancleary.co.uk. Republished with permission)
