An Investigation of the Ink-Transfer Mechanism During the Printing Phase of High-Resolution Roll-to-Roll Gravure Printing

Reducing the linewidth of electrodes is of high importance for increasing not only the efficiency of photovoltaic devices but also the performance of organic thin-film transistors. In particular, controlling the line pattern in printing processes has been difficult. In this paper, we report an analytical approach for obtaining high-resolution control over the ink-transfer mechanism in roll-to-roll (R2R) gravure printing. A dimensionless adhesion-force difference was defined for a simple ink-transfer model, and it was used to predict and evaluate the ink-transfer mechanism with respect to several parameters, such as the surface tension of the ink, surface energy of the substrate, and surface energy and aspect ratio (AR) of the cell. It was found that the low-surface-tension inks, high-surface-energy substrates, and low-surface-energy and high-AR cells are preferable to increasing the ink-transfer ratio during the printing phase. Finally, a matching-logic flowchart was developed for controlling the ink-transfer mechanism and fidelity of R2R gravure printing. The printed patterns obtained had an average width as small as 15.3 mu m (standard deviation = 0.9 mu m).