| 摘要 |
The invention provides a surface, or electric field, stabilised ferroelectric liquid crystal (SSFLC) device with an improved contrast ratio between its two switched states. The device comprises a liquid crystal cell formed by a thin layer (7), typically 1 to 5 mu m thick, of a smectic liquid crystal material, e.g. a smectic c, held between two glass walls (2, 3) coated on their inner faces with electrodes (5, 6). Polarisers (8, 9) are arranged on either side of the walls (2, 3). The device is switched between two bistable states by application of unidirectional voltage pulses, with or without the simultaneous application of ac bias voltages. To obtain optimum contrast ratio CR, the optical axes of the polarisers are rotated away from a crossed, or orthogonal position, e.g. by +/-20 DEG , and the cell rotated between the polarisers (8, 9); the precise optimum rotation depends upon material, and ac bias voltage. |
