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 (Figure 5). 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 (Figure 6).
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.