Inkjet Process for Flexible Touchscreens

Printed touchscreen with new nanoparticle inks (Source: INM)

Printed touchscreen with new nanoparticle inks (Source: INM)

Mobile phones and smart phones still haven‘t been adapted to the carrying habits of their users. That much is clear to anyone who has tried sitting down with a mobile phone in the back pocket: the displays of the innu­merable phones and pods are rigid and do not yield to the anatomical forms adopted by the people carrying them. By now it is no longer any secret that the big players in the industry are working on flexible displays. How to produce suitable coatings for those cost-effi­ciently will be demonstrated by INM – Leibniz-Institute for New Materials at this year’s Hannover Messe.

These new inks are suitable for an one-step printing process. Thus transparent lines and patterns are obtained by inkjet printing or alter­natively by direct gravure printing, which are electri­cally conductive even after bending. Thus, a one-step-printing process for cost-efficient TCO structures is enabled.

Conductive coatings with TCOs are usually applied by means of high vacuum tech­niques such as sputtering. For patterning of the TCO coatings additional cost-intensive process steps are necessary, for example photo­lithography and etching. “We use the TCOs to produce nano­particles with special properties,” explains Peter William de Oliveira, Head of the Optical Materials Program Division. “The TCO ink is then created by adding a solvent and a special binder to these TCO particles. The binder performs several tasks here: it not only makes the TCO nano­particles adhere well on the substrate; it also increases the flexi­bility of the TCO coating: in this way, the conduc­tivity is maintained even when the films are bent”.

The ink can be applied to the film directly by inkjet or gravure printing. After curing under UV light at low tempera­tures the coating is completed. The transparent, electroni­cally conductive inks allow conductor tracks to be produced unproblema­tically even on a large scale by means of classic reel-to-reel processes. Initial trials at INM have been promising. The researchers all agree that the use of structured rollers will in the future allow large, structured conductive surfaces to be printed with a high throughput at low cost. (Source: INM)

Link: INM – Leibniz Institute for New Materials, Saarbrücken, Germany

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