Polymer-stabilized cholesteric textures for scattering-mode projection light valves

Oriented polymer networks are dispersed by photopolymerization in a chiral nematic material to stabilize its focal-conic texture and create a unique electro-optic response for use in an improved display technology. The electro-optic performance of the material is characterized in terms of the monomer and chiral concentration, and the physics of operation is understood by determining the molecular structure and measuring the orientational order of the network. The structure is determined by measuring the birefringence for a range of monomer concentrations at temperatures beyond the N-I transition of the liquid crystal (5CB). Experimental results are fitted with an equation derived from the Landau-de Gennes theory. The value obtained for the fitting parameter yields a measure of the radius of the polymer fibers. Birefringence of the bare network yields values of its orientational order. Polymer networks formed in the liquid crystal environment are further examined with optical and scanning electronic microscopy (SEM). The dissertation in particular addresses the effect of homeotropic orientation on the structure of the polymer network and offers a model on how the networks are formed.; The order parameter of the polymer network is found to be {dollar}sim{dollar}0.3 as opposed to 0.6 for the nematic liquid crystal. The radius of the polymer fibers is found to be {dollar}sim{dollar}-50A, a value consistent with images obtained from SEM studies. In the electro-optical characteristics of the Polymer Stabilized Cholesteric Textures (PSCT) system, the presence of the polymer network does not present any adverse effect on the transmission of the light in the powered state of a cell, mainly because the concentration of the polymer is very low and light scattering by the network is minimal. In the unpowered state, the focal-conic texture is found to be stabilized by the polymer network. The network is also used to optimize the large hysteresis exhibited by the system which is necessary for bistability and for a high contrast projection display system. A bias voltage is defined within the hysteresis loop such that the application of this bias maintains bistable electro-optic performance. A driving scheme is developed for a 320 x 320 pixel passive matrix and a projection light valve constructed complete with drive electronics. The performance of this high resolution light valve is demonstrated by use on an overhead projector.; The 320 x 320 pixel projection light valve proves to be successful and promising for certain commercial and scientific applications. The fabrication of the display is simple: it does not require an active matrix and the electronic hardware requires no custom design. When the light valve is put into operation, it delivers an image with very high brightness and clarity.