Picture display device

Abstract

A picture display device has picture elements disposed in a line and row matrix for applying voltage to liquid crystal material to display a picture in accordance with picture signals applied thereto. The picture signals consist of gate signals sequentially applied to the picture elements along the row directions and video signals simultaneously applied to the picture elements along the line directions. A video signal detecting circuit detects the existence of the picture signals and produces a detection signal whenever the picture signals are temporarily absent for longer than a predetermined time period, and circuitry responds to the detection signal for inverting the polarity of the voltage applied to the liquid crystal material. The video signal detecting circuit may detect the presence of a horizontal or vertical synchronous signal of the video signal, or may compare the average voltage level of the video signal with a reference voltage level, to detect the presence of the picture signals. The inversion of the drive voltage polarity greatly prolongs the life of the liquid crystal and since the inversion is carried out during the time that the picture signals are temporarily interrupted, the inversion of the drive voltage polarity does not disturb the picture or cause picture flicker.