Glittering promise

Inkjet breakthrough for proofing, labels and small packaging

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Today’s inkjet printers are brilliant pieces of technology. We all know about desktop and wide format inkjets for photo and poster printing. In the past decade big high-volume industrial-strength wide format printers have steadily encroached into the short-run large format print markets previously dominated by screen process and offset. The past year has seen the introduction of narrow-web format inkjets with UV inks, intended to handle the label and packaging work that’s currently mainly printed by flexography.
What inkjets aren’t very good at are special decorative colours, that are handled with ease by screen, flexo and offset processes. Metallics? Fluorescents? Pearlescents? Forget it. Until now. The past year has seen the start of a move into this area. It looks as if the dream of a metallic ink that can be printed digitally is approaching commercial reality.

At drupa, Eckart Metallic Powders, a leader in metallic offset inks, will demonstrate printing a silver metallic ink on a standard wide format inkjet. This can then be overprinted with normal inks to form gold or other metallic colours.

Eckart company originally worked closely with MetalFX when it was developing its commercially successful process for achieving coloured metallic effects with litho inks overprinting a silver metallic. The MetalFX colour software will be used to create the colour channels for the Eckart inkjet demonstration at the show says Colin Appleyard, head of digital at Eckart’s German headquarters.

The model chosen is a Mimaki JV3-160S solvent ink wide format inkjet, which Eckart has been using in its factory tests. However, virtually any similar printer could be used, Mr Appleyard says.

We’re reproduced a test sheet from the Mimaki here. We can’t show the metallic effect, but it’s certainly eye-catching on the high gloss original. The plain silver is a very smooth, almost mirror finish. The overprint colours are slightly grainy, but this is the normal effect of the Mimaki printer, which isn’t designed for close-up viewing. Our sample didn’t have much rub resistance and the colours over the silver were easily abraded, so lamination might be needed. However, the ink is still at an early stage and being rapidly improved, says Mr Appleyard. A UV-cured ink is the real target for Eckart and would presumably be a lot tougher. The company has developed a UV-cured inkjet metallic but it’s not ready for public demonstration, he says.

By demonstrating live production at drupa, the company is hoping to drum up interest from the printer and print head manufacturers. “Convincing print head manufacturers to develop for this ink has been a slow process. Now we have a system working that we can show to them at drupa,” says Mr Appleyard. “Actually, it’s not so important for wide format, but for the new one-pass printers for labels and small packaging it’s going to be really necessary. A lot of brands already use metallics in their designs and they aren’t going to change them just so they can be printed digitally.”

For the past 18 months, he has been working with print head developer Xaar, whose new 1001 Hybrid Side-Shooter head has been designed to jet large particle inks without clogging. The 1001 head is already being used on the EFI Jetrion 4000 and Nilpeter Caslon narrow-web UV-cured digital label printers, and will appear on other, so far unannounced models at drupa.

Eckart was hoping to demonstrate its metallic ink with a 1001 head at drupa, but decided it’s not ready yet. However, the company has ordered a printer from JF Machines of Kettering in England, to use as a test-bed. This is a reel-to-reel chassis for narrow-width label webs that can be fitted with a variety of inkjet heads, as well as in-line conventional print units for coating and the like. JF Machines will show an example on the Xaar stand at drupa, fitted with a 1001 head, but not printing the metallic ink.

Any metallic ink contains small flakes of reflective metal, which have to be a certain size in order to produce the distinctive reflective effect – too small and the particles would just look grey or black. Mr Appleyard says that the inkjet fluid being developed contains the smallest particles the company has ever used. They are about 2 microns diameter, about 100x larger than conventional inkjet pigment particles, although the flakes are very thin, in the 50-70 nanometre range.

The issue with a metallic ink is that large particles pose a danger of clogging the heads. Most drop-on-demand heads incorporate very fine filters to stop anything too large from getting to the ultra-fine nozzles. There’s also an issue of the metallic particles being relatively heavy, so ideally an agitation system is needed to stop them falling out of suspension. This is easy to arrange for high volume printers that have ink tanks, but less so for the plug-in sealed cartridges that are commonly used for the likes of Mimaki, Mutoh and Roland entry- to mid-range printers.

When inkjet makers were developing systems to handle white inks, they faced similar problems, though the titanium particles in white ink are a bit smaller and lighter than the aluminium particles used by Eckart’s metallic. White ink wide format printers are now fairly common. However, the Mimaki JV3 printer that will demonstrate the metallic at drupa is not a white ink model, says Mr Eckard. “It uses Epson print heads, which usually use the smallest particles of all. ”If it will work with those, it should work with anyone’s printers, he says. “We’ve talked to Epson in the UK and they’ve arranged for us to see the Epson Japan engineers when we’re at drupa.”

All being well, Eckart should soon be the first ink maker to deliver metallic for variable data to suit a wide range of inkjets. A shining future seems assured.