Performance of Conventional and Novel Deformed Helix Ferroelectric Liquid Crystal Display Operating Modes

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Abstract
Fast response times and wide viewing angles are characteristic features of the deformed-helix ferroelectric liquid crystal displays (DHF-LCDs) presented in this paper. We first discuss the electrooptics of the DHF effect, emphasizing the large electrically induced changes of birefringence which occur in DHF-LCDs with large switching angles. Based on these results a new DHF operating mode is introduced, which allows DHF display cell gaps larger than 5 µm. A second new type of DHF-LCD operating mode is then presented, which is used for low-tilt-angle DHF materials. This second, double-layer DHF-LCD allows fast, bright, ghost-free, low-voltage operation. Finally, the influence of various FLC material parameters and their temperature dependence on DHF display performance is investigated. It is shown that a pitch below 150 nm at room temperature is required for high-contrast DHF-LCDs. It is also shown that with suitable driving electronics, operation of DHF-LCDs at video rates is possible down to -15°C.