Application of amorphous oxide TFT to electrophoretic display

Application of amorphous oxide thin film transistor (TFT) to electronic paper is demonstrated. We have fabricated a 4-in. bottom gate amorphous In–Ga–Zn–O (a-IGZO) TFT array and combined it with an electrophoretic frontplane. The resolution of the display is 200 ppi and the number of the pixel is 640 × 480 (QVGA). As far as we know, this is the largest pixel count display which has been driven by oxide based TFTs. Moreover, we propose a low-cost fabrication process for oxide based TFT. A printing process was employed to form the source and drain electrodes. The source and electrodes were printed by a standard screen-printing method. A fine pattern for the source and drain electrodes with a channel length of 40 μm was successfully printed onto the a-IGZO semiconductor layer. Our a-IGZO TFT with printed source and drain electrodes shows high on/off ratio of more than seven orders of magnitude and field effect mobility of 2.8 cm2/V s.