Active-matrix deformed-helix ferroelectric liquid crystal displays

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Abstract
Active-matrix DHFLC displays have potential for a better performance than can be obtained with TN AM-LCDs. Alignment of DHFLC is still difficult and the defect structure lowers the contrast. A forming voltage improves the contrast, but the defects reappear during temperature cycling in the S*C-phase. At least four different types of defects can be distinguished. Active-matrix driving of DHFLC is thoroughly investigated. The symmetric DHFLC mode is the preferred mode, for it prevents the occurence of image retention. Voltage driving and charge driving are both possible. Special measures have to be taken to improve the step response of the display. A diode-AM-DHFLC display is described which operates at video speed and shows a good step response and a wide angle of view.