Liquid crystal x{14 y matrix display device

Claim 1

In a liquid crystal X-Y matrix display device which has: a liquid crystal X-Y matrix display panel including (1) an Xelectrode member having a first plate and a plurality of stripshaped X-electrodes applied to the surface of said first plate, (2) a Y-electrode member is spaced opposed relationship to said X-electrode member and having a second plate and a plurality of strip-shaped Y-electrodes applied to the surface of said second plate, at least one of said X- and Y-electrode members being light-transparent, and (3) a liquid crystal which fills the space between said X- and Y-electrode members and has a threshold voltage in a.c. operation above which said liquid crystal exhibits a change in the transparency, the direction of said X-electrodes being perpendicular to the direction of said Y-electrodes and said X- and Y-electrodes and said liquid crystal therebetween form a plurality of display elements at the intersections of said electrodes; a signal generator for generating X-address signals and image signals synchronized with said X-address signals; first means coupled to said signal generator and to each of said X-electrodes and supplying each of said X-electrodes addressed by each of said X-address signals generated by said signal generator with an X-address pulse; and second means being coupled to said signal generator and to said Y-electrodes for generating Y-signals and supplying each of said Y-electrodes with Y-signals which have an a.c. voltage amplitude Vy, an average level Vavy and phase phi 2, and supplying each of said Y-electrodes with each of said Ysignals, whereby said display elements change in transparency with the change in the time interval of the Y-signal controlled by said image signal so that a desired image is formed on said liquid crystal layer of the matrix panel; the improvement comprising said first means comprising means for supplying said X-address pulse as a gated a.c. voltage having a time interval T1, an operative frequency f above that which will unduly shorten the life of the liquid crystal and below that which will cause the turn-on threshold voltage of the liquid crystal to exceed the breakdown voltage of the device, phase phi 1 the same as that of said Y-signal, amplitude Vx and average level Vavx, and said second means comprises means for supplying said Y-signal with a frequency the same as the frequency of said X-address pulse and for switching the phase phi 1 of said Y-signal to said phase phi 2 during a time interval T2 with a change in the corresponding image signal and for supplying said Y-signal with an amplitude Vy no higher than said turn-on threshold voltage at said frequency f and more than one-third of said turn-on threshold voltage and substantially equal to a half of said amplitude Vx of said Xaddress pulse, and with an average level Vavy substantially equal to said average level Vavx of said X-address pulse.