Achieving specified geometric quality in a fully printed flexible functional layer using process parameters in roll-to-roll printed electronics

Abstract

Roll-to-roll (R2R) gravure printing is mainly used in the manufacture of conductive lines or electronic devices because complex patterns can be printed quickly and accurately on flexible substrates using an engraved pattern roll. Gravure printing has several advantages including multi-layer printing of large-area functional layers and continuous production of electronic devices such as thin-film transistors (TFTs) or complex electronic circuits. Existing studies have demonstrated that printing quality can be improved by determining the desired conditions of coating and printing machine without changing the ink and web properties. However, few studies have focused on controlling the geometry of printed patterns and coated layers according to the web tension and web speed, considering spreading effect and ink transfer. In this study, the effects of the controllable parameters in R2R gravure printing, namely web tension and web speed, on the geometry of the gate electrode, dielectric layer, and source–drain electrode of a TFT are examined. We obtained metamodels to estimate the thicknesses and widths of the conductive and dielectric patterns of a printed TFT according to the web tension and speed of a pilot-scale R2R gravure printing machine using design of experiment. The developed metamodels exhibited superior performance, with an average estimation error of 4.18 ± 3.05%. We further analyzed variations in the thickness of the gate electrode and dielectric layer according to fluctuations in the tension in the R2R printing process. Our results show that fluctuations in the tension should be maintained constant to achieve a uniform geometry of the printed pattern. This study demonstrates that the geometry of the printed pattern can be controlled using web tension and web speed, without changing the ink properties.