An in-cell capacitive touch sensor integrated in an LTPS WSVGA TFT-LCD

This paper discusses an In-cell capacitive touch sensor and its integration in an LTPS TFT-LCD with 7-inch screen size and WSVGA resolution. The operation of the newly developed sensor is based on capacitive coupling between user's finger and the detection electrode on the TFT substrate, and is purely capacitive. The sensors and the sensor driver circuits have been integrated in the TFT substrate of the prototype TFT-LCD using LTPS technology. The prototype having 256x150 sensors shows advantages such as smooth operation with no touch force, high position accuracy, multi-touch (10 or more), a thin and light LCD module, high display quality, and thus is suitable for various applications such as cell-phones, smart-phones, mobile-PCs, and automotive-use displays.