Hiding the pattern

Conductive film requires patterning to produce capacitive touch sensors. This can either be accomplished by laser or by a wet process.

Pattern visibility is a challenge for all conductive materials such as ITO, AgNW, metal-mesh or CNT. The different optical properties of patterned (etched) and unpatterned (unetched) areas are difficult to conceal. Transmission-, color-, haze-, and refractive index-differences cause visibility which can only be concealed by adding steps to the manufacturing process. Even then, slight visibility often remains.

Cutting out the steps

Heraeus has developed a special technology to pattern Clevios™ coatings by a wet process. The generated patterns are invisible or hardly visible to the human eye, so there is no need for additional steps to conceal them, keeping costs lower. A masked Clevios™ film is immersed in a solution of Clevios™ Etch, which does not physically remove (etch) the layer but deactivates the conductivity while leaving the optical properties unchanged.

Masking can be done by an economic screen-, gravure-, or flex-printing process, or for finer structures by photoresist. An application guide is available.

During production, optical inspection by CCD is made possible by a special analytical detection method that can easily be implemented.

Clevios™ for Touch Panels

In Clevios™ PH 1000, Heraeus offers the world’s highest conductive PEDOT:PSS dispersion, boasting up to 1000 S/cm. It yields sheet resistance levels in coating formulations as low as 150 Ohm/sq with high transmission suitable for touch panel applications.

Clevios™ F 100T is a special stabilized PEDOT:PSS dispersion for formulations and coatings with improved stability in harsh environmental tests, e.g., 60/90 or 85/85.

Clevios™ F ET is one of the ready to use coating formulations that yields SR below 200 Ohm/sq at 12 micron wet film thickness.

Clevios™ F DX2 / Clevios™ XL is a new two-component coating formulation with better hardness and resistance to solvents.

Clevios™ Etch and Clevios™ Set S3 are auxiliary materials to pattern Clevios™ coated films. Clevios™ Etch is a water-soluble powder, and Clevios™ Set S3 is a printable mask (screen printing).

Lower sheet resistance

For touch sensors that require lower sheet resistances (SR) such as for larger displays, Heraeus offers Clevios™ HY E, hybrid materials of silver nanowires (AgNW) and PEDOT:PSS. Clevios™ HY E is a ready-to-use coating formulation. A top coat to protect the silver nanowires from oxidation, Clevios™ OC 1, is also offered. Clevios™ HY E can be patterned in the same way as PEDOT:PSS only based Clevios™ coatings. Read more this topic here.