| A cholesteric liquid crystal can be either in a planar texture, or in a focal conic texture, or in a fingerprint texture, or in a homeotropic texture. In this dissertation, we study the dynamics of the transitions among these textures, which have played an important role in driving bistable cholesteric liquid crystal displays.; We studied the homeotropic→planar transition with consideration of surface anchoring. Based on a tensor representation of the free energy expression, our 1-D modeling shows that, in a cell with homeotropic anchoring, the helical twist can be continuously “injected” from the surface of the cell to the bulk, which leads to a much faster homeotropic→planar transition than in a cell with homogeneous anchoring where the change of pitch is a discontinuous jump and a nucleation process.; We studied the field induced fingerprint→homeotropic transition in cells with finite thickness using both 2-D and 3-D modeling. When the field is above a critical field, parallel fingers (parallel pi-walls) become circular pi-walls. When the field is increased further, the circular pi-walls can be unwound into the homeotropic texture smoothly through a cylindrical conic structure.; We also studied the homeotropic→focal conic transition. Our 3-D modeling shows that the homeotropic texture with nucleation seeds will relax to the focal conic texture when the field is dropped to about 0.9 Ec, which is close to the value observed in experiment. In a cell with homogenous anchoring, a finger texture grows parallel to the rubbing direction. In a cell with homeotropic anchoring, the finger grows along all directions.; Bistable reflective cholesteric liquid crystal displays suffer from a slow response and require a high driving voltage. By studying the frequency dependence of their electro-optical performances, we have found that at an intermediate frequency, the driving voltage is reduced, the response time is reduced, and the contrast ratio is increased. We qualitatively understand the frequency dependence of the driving voltage in terms of ionic effects. |
