Transparent Electrodes

Generally speaking, polymers are insulators. However, there is a special class of polymers - the intrinsically conductive polymers - that have conductivity levels between those of semiconductors and metals (from 10-4 to 103 S/cm). The combination of metal and polymer properties opens up new opportunities in many applications, particularly in the electronics industry.

With PEDOT (poly(3,4-ethylenedioxythiophene)) - available under the trade name Clevios™ - Heraeus has developed the latest generation of conductive polymers which are characterized by outstanding properties:

  • High conductivity
  • High transparency
  • High stability
  • Easy processing

For high conductive coatings Clevios™ PH 1000, stabilized Clevios™ F 100T, or its ready to use formulation, Clevios™ FE-T can be used. These materials offer not only high conductivities but also exceptional levels of transparency.

A conductivity of 900-1000 S/cm can be reached by using Clevios™ PH 1000 together with a conductivity enhancement agent such as DMSO or ethylene glycol. The ready to use formulation CLEVIOS™ FE-T is water-based and contains a polymer binder, wetting agent etc. to ensure good processing, adhesion to the substrate and mechanical strength.

Coating formulations have been optimized for individual substrates, such as A-PET, PET, polycarbonate, glass for different wet film thicknesses and surface resistivities.

Coating can be achieved by standard printing processes, such as slit die, Inkjet, screen or gravure methods. Also brushing, spraying, spin-coating or roller coating can be used.

Clevios™ F DX2 / Clevios X-L is the latest addition to the family of highly conductive Clevios™ formulations. It’s a two component hard-coat formulation that provides good chemical and scratch resistance in addition to low sheet resistance and high transmissions.

One of the most exciting topics in current display development are foldable and rollable touch displays. As Clevios™ is an organic polymer material, it is intrinsically flexible and can even be stretched or 3-D thermoformed. Together with ITRI in Taiwan, Heraeus has developed the world first prototype of a flexible AMOLED with an out-cell foldable touch panel based on Clevios. Publications with more information can be found in the touch panel download section.

Transparent Electrode Applications – Touch Panels

Transparent electrodes can be used in many applications, e.g. in displays and touch panels for the pixel electrodes and transparent touch sensor electrodes or in smartwindows.

In capacitive touch panels, Clevios™ is a very cost-effective alternative to state-of-the-art ITO film. Coated films are commercially available from several Heraeus partners at various sheet resistance levels of 150 Ohm/sq, 225 Ohm/sq, 385 Ohm/sq etc.

Heraeus has developed a special patterning process technology for Clevios™ coated films. A set of process chemicals of printable resist materials (Clevios™ Set S) and etchants (or deactivation) material Clevios™ Etch are available as well as a complete process and application guide.

To complete the materials package, Heraeus also supplies a compatible low temperature silver printing paste, LTC 3413. Line / Space as fine as 100 µm / 100 µm can be deposited by screen-printing and the paste cures rapidly at 120°C within just a few minutes.

Heraeus has an application center for Clevios touch technologies located in Taiwan to support customers in their development of new flexible touch panels as well as in implementing Clevios™ touch technologies in existing production lines and infrastructures.

Downloads

Highly Conductive Coatings in Electronics

Products for patterning Clevios™ films

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