| 摘要 |
<p>18 A liquid crystal display device comprises two supporting plates which are kept spaced apart and the facing surfaces of which comprise a pattern of line electrodes and column electrodes, respectively, which form a matrix of display cells. A mixture of a nematic liquid crystal with a cholesteric addition is present between the supporting plates. The mixture has a positive dielectric anisotropy and a natural pitch p such that the ratio d/p has a value between 0.6 and 0.9. The surfaces comprise an orientation layer to provide a progressive molecular twist ? the liquid crystal molecules (director) across the layer thickness a of greater than 1.2 .pi. and less than 1.7.pi. radians, the director assuming an angle of tilt between 0.degree. and 7.degree. at one surface and an angle of tilt between 5.degree. and 70.degree. at the other surface. Below a field strength E1 the display cells are in a first stable state and above a field strength E2 they are in a second state differing optically therefrom. At a field strength EH between E1 and E2 both states may co-exist. Starting from the first state and a field strength EH across the display cells, the liquid crystal material shows a small energy threshold in such manner that a cell can be switched from the first stable state to the second by means of a pulsatory field having an energy content above the energy threshold. With a pulsatory field having an energy content below the energy threshold, the cell returns to the initial state viaa metastable state having a certain relaxation period. When the recurrence frequency with which a picture cell is driven does not exceed the reciprocal value of the relaxation period, more than 2,000 lines can be successively written in this manner within one second.</p> |
