Low drive voltage display device

Claim 1

A display device comprising two support plates spaced at a defined distance from each other and having surfaces facing each other between which a layer of liquid crystal material is provided, a pattern of N row electrodes being provided on one surface and a pattern of column electrodes being provided on the other surface, said row electrodes crossing the column electrodes so that the crossover regions form a matrix of display cells which can be switched from a first condition to a second condition optically different therefrom by means of a row-scanning circuit periodically scanning the row electrodes with a row selection pulse of the magnitude V s , and a column-selection circuit applying data voltages of the magnitude±V d to the column electrodes during a period when a row electrode is scanned such that the optical condition produced in a display cell is determined by the RMS-voltage value across the relevant cell, said RMS-voltage value for the selected display cells, i.e. the display cells in the on-condition, being given by and for the non-selected display cells, i.e. the display cells in the off-condition, being given by ##EQU19## wherein the ratio V1/V2 in the transmission voltage characteristic curve of the optical effect associated with the liquid crystal material is of such a nature that not more then N max row electrodes can be used for a selected contrast ratio between selected and non-selected display cells in accordance with the Alt & Pleshko RMS multiplex drive mode, characterized in that for N<N max the voltage ratio Vs/Vd is defined by the relation: ##EQU20##