Printing pressure uniformization through adaptive feedforward control in roll-to-roll printing process

Roll-to-roll printed electronics is a fabrication technology for electrical devices using functional ink and flexible material films. When the printing pressure is not uniform between the two rolls in the roll-to-roll process, the printing quality degrades, which makes commercialization of printed electronics difficult. In this study, we constructed a system in which both ends of the impression roll are driven individually, unlike the conventional printing pressure control system, for accurate printing pressure measurement. However, in the actual process, since the printing pressure cannot be measured in real time in the nip, which is the contact surface between one roll and the other roll, a load cell is installed at both ends of the impression roll to measure the printing pressure. This measurement limit causes a measurement delay. To compensate for the measurement delay, we measure the printing pressure and perform a frequency analysis of the measured printing pressure to calculate the correct measurement delay value. Then we calculate the measurement delay using the frequency response function and use a time delay predictor to compensate for the calculated measurement delay. However, even if the measurement delay is compensated for, there is a printing pressure error due to repeatable run-out (RRO). To eliminate the residual error after compensating for the measurement delay, we perform a frequency analysis of the printing pressure after compensating for the measurement delay. We then apply adaptive feedforward control to uniformize the printing pressure additionally.