Active Matrix Touch Sensor Perceiving Liquid Crystal Capacitance with Amorphous Silicon Thin Film Transistors

An active matrix touch sensor is integrated into a liquid crystal display (LCD) panel. The sensor is composed of a liquid crystal capacitor and a sensing circuit with amorphous silicon thin film transistors (a-Si TFTs). The change in sensor capacitance when the sensor is touched is converted into current change by the sensing circuit in the pixel. The proposed touch sensor is pressure-sensitive enough to work at an external push force of 10 gf. The simplified sensing circuit also gives an improved aperture ratio over that in previous work.