Ferroelectric liquid crystal displays for television application

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Abstract
The surface-stabilized ferroelectric liquid crystal (SSFLC) effect is a serious candidate for application in television displays, due to its high switching speed and viewing angle independence. For the television application, however, several severe requirements must be fulfilled, of which the demand for a large amount of gray levels is very crucial in view of the bistable character of the SSFLC effect. A review and discussion of the different approaches to realize gradation in SSFLC structures is given. The so-called dither techniques yield discrete gray levels but become complex when many levels are required. Analogue gradation methods are based on in-pixel domain switching but require an accurate control of the multidomain structures. Active-matrix addressing of the SSFLC effect enhances the reproducibility of the multidomain gray levels via the charge-control process, resulting in a fast-switching, viewing-angle-independent video display. Passive-matrix addressing (multiplexing) takes advantage of the bistability and the switching speed of the SSFLC effect. One approach to control the multidomain gray levels in passive-matrix addressing is extensively dealt with; the “texture-method”. The mcchanism, the addressing scheme, the obtainable contrast in the different textures and the applicability of various FLC mixtures are discussed. The resulting performance of test displays, operating at video rate and possessing full gradation, is evaluated. Finally, some indications will be given of the remaining problems, which need further improvement before FLC displays can be successfully applied for television.