Liquid crystal display device employing a guard plane between a layer

Abstract

The present invention provides for touch input functionality in a liquid crystal display having a plurality of cells each comprising a first substrate having a common electrode integrated thereon, a second substrate having a pixel electrode integrated thereon, and liquid crystal material disposed between the common electrode and pixel electrode. A first conductive layer (signal layer) and second conductive layer (guard plane layer) are integrated onto the first substrate and disposed between the first substrate and the common electrode. Contact position of a touch input device with the first substrate is determined by applying a first signal to the signal layer. A second signal is applied to the guard plane layer to thereby lower capacitive coupling between the signal layer and the common electrode. Response to the first signal is measured to determine contact position of the touch input device. Preferably, the portion of the signal layer disposed opposite the pixel electrode is a patterned layer of black matrix material, and the guard plane layer may be a transparent ITO layer. Alternatively, portions of the signal layer and guard plane layer disposed opposite the pixel electrode may be a patterned layer of black matrix material.