Ferroelectric liquid crystal display device with a particular angle between the polarizer optical axes and the molecular director
US5638143A · kind A · utility
Assignee
Inventors
Key dates
| Filing date | Jun 15, 1994 |
| Grant date | Jun 10, 1997 |
| Priority date | — |
| Expiry date | Jun 15, 2014 |
Classification
- Technology area (CPC G)Physics
- CPC primaryG02F1/133531
- WIPO fieldOptics
- WIPO sectorInstruments
Abstract
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, eg a smectic c, held between two glass walls (2, 3) coated on their inner faces with electrodes (5, 6). Polarizers (8, 9) are arranged either side 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 axis of the polarisers are rotated away from a crossed, or othogonal position. eg by +/-20.degree., and the cell rotated between the polarisers (8, 9); the precise optimum rotation depends upon material, and ac bias voltage.
Source: USPTO / EPO open patent data. Objective bibliographic and citation counts.