High tilted antiferroelectric liquid crystals: Polymer-based approach for phase stabilisation and device development

Abstract

On doping orthoconic antiferroelectric liquid crystal (OAFLC) mixtures with a small concentration of reactive mesogens, new liquid crystalline material was engineered with improved opto-electronic performance. In-situ photo polymerisation of the mixtures resulted in the creation of a polymer network that helped removal of the metastability bought on by F-states (Synclinic Ferroelectric State) in tristate switching devices. These metastable states causes the switching timings of the device to be asymmetrical, with the fall time being significantly longer than the rise time due to the difficulty in relaxing from the Ferroelectric-synclinic to the Antiferroelectric-anticlinic state. The opto-electronic parameters of the device cells were measured before and after the mixtures were stabilised by Ultraviolet light (UV) polymerisation. Polymer stabilisation of the orthoconic state yielded symmetric optical rise and fall times, accompanied by a reduction in the electrical response times. Spontaneous polarisation in the OAFLC mixtures were found to decrease after UV polymerisation; however, this is an important trade-off vis-à-vis symmetric optical response times, considering the overall performance of the material from an application standpoint.