Scalability of Roll-to-Roll Gravure-Printed Electrodes on Plastic Foils

Roll-to-roll (R2R) gravure printing is considered to be a leading technology for the production of flexible and low-cost printed electronics in the near future. To enable the use of R2R gravure in printed electronics, the limits of overlay printing registration accuracy (OPRA) and the scalability of printed features with respect to the physical parameters of the gravure system, including given plastic substrates and inks, should be characterized. Important parameters of printed lines include surface roughness, thickness, line widening, and line-edge roughness. To date, there are no comprehensive reports regarding the limits of OPRA and the scalability of printed electrodes, including the control of surface roughness, thickness, line widening, and line-edge roughness using R2R gravure printing. In this paper, we examine ways of evaluating the OPRA limit of our gravure system. We find that OPRA is limited in the web moving direction to 40 mu m and in the perpendicular direction to 16 mu m, showing the importance of web handling on registration. Furthermore, we demonstrate the scalability of printed electrodes formed using a R2R gravure system to linewidths of 317 mu m, with 440 nm thickness, 30 nm of surface roughness and edge waviness of 4 mu m on PET foils, and describe optimization strategies to realize improved surface roughness, thickness, line widening, and line-edge roughness for future printed electronics applications.