Addressing scheme for switch controlled liquid crystal displays

In known thin film switch controlled matrix multiplexed liquid crystal displays (LCD's), alternating pulses of an applied waveform are of reverse polarity. If the transient behaviour characteristic of the switches controlling the LCD is not saturated during application of a selection pulse, the selected pels may experience a relatively low RMS voltage in the ON state. To ensure that selected pels are fully turned on, the addressing waveform proposed consists of a series of pulses of one polarity followed by a corresponding series of pulses of opposite polarity. Transient effects are minimized by applying the series of unipolar pulses and the pels are consequently subjected to a high RMS voltage. However, net DC current through the LC is still zero as required in order to guard against irreversible electrochemical degradation of the LC. The higher RMS voltage can be used to improve contrast ratio or to increase the level of multiplexing.