Selective Inkjet Printing of Conductors for Displays and Flexible Printed Electronics

A mask-less and selective printing of conductor patterns is of significant importance for all display applications. Printing on structured surfaces such as microlenses or gratings is a challenge. Typically used processes require thermal curing to achieve the conductivity. This limits the applicability to flexible display applications where low temperature processes are preferred, especially for roll to roll (R2R) scale up. We have used an approach of printing a catalyst containing ink, followed by an electroless plating of copper. This paper details the processes, microstructures and properties of highly conductive and printed copper on patterned flat surfaces as well as structures with micro-optic lens structures. A process has been developed on surfaces with lens structures where the conductor is required to be in the valley between the lenses and between structures with narrow lines and narrow pitch. This is a low temperature process, requiring a plating bath temperature of <;45°C and thus very compatible with flexible substrates and R2R processing.