A modified offset roll printing for thin film transistor applications

In order to realize a high resolution and high throughput printing method for thin film transistor application, a modified offset roll printing was studied. This roll printing chiefly consists of a blanket with low surface energy and a printing plate (cliché) with high surface energy. In this study, a finite element analysis was done to predict the blanket deformation and to find the optimal angle of cliché's sidewall. Various etching methods were investigated to obtain a high resolution cliché and the surface energy of the blanket and cliché was analyzed for ink transfer. A high resolution cliché with the sidewall angle of 90° and the intaglio depth of 13 μm was fabricated by the deep reactive ion etching method. Based on the surface energy analysis, we extracted the most favorable condition to transfer inks from a blanket to a cliché, and thus thin films were deposited on a Si-cliché to increase the surface energy. Through controlling roll speed and pressure, two inks, etch-resist and silver paste, were printed on a rigid substrate, and the fine patterns of 10 μm width and 6 μm line spacing were achieved. By using this printing process, the top gate amorphous indium-gallium-zinc-oxide TFTs with channel width/length of 12/6 μm were successfully fabricated by printing etch-resists.