Bistable twisted nematic liquid crystals display with permanent grayscales and fast switching

Permanent grayscales in a π bistable twisted nematic liquid crystal display have been demonstrated. This display can be switched between –22.5° and 157.5° twist states by means of a combination of strong in-plane electric fields and vertical electric field for creating both the planar anchoring breaking and an electro-hydrodynamic flow. The switching of the twist states during the Frederiks transition is sufficiently inhomogeneous such that domains of –22.5° twisted and 157.5° twisted states are formed. The ratio of these domains can be controlled by the vertical electric field. Fast switching of 1 ms was achieved for gray scales. These grayscales have very long lifetime.