Printing applications of a-Si thin film transistors

Abstract Amorphous silicon (a-Si:H) thin film transistors (TFT) have been used to drive the printing transducers in three different types of printers: ionographic, electrographic and liquid crystal shutter printers. In the ionographic printer application, arrays with both digital and analogue a-Si TFT circuits have been made to produce black-and-white and grey-scale prints. In the electrographic printer application, high voltage a-Si TFTs capable of switching 400 to 500 volts were utilized to initiate the air breakdown required by the printing mechanism. In the liquid crystal printer application, each pixel has a four-TFT sample-and-hold circuit to allow synchronized reversal of the applied voltage across the liquid crystal shutter as required by long life operation. These three printing applications of a-Si TFT will be described in this paper.