Bistable Dual Frequency Liquid Crystal Devices Assisted by Ferroelectric Liquid Crystals

Abstract

The demand for energy-saving devices has been increasing in recent years Among overall energy consumption human spend most of energy on sustaining the comfortable indoor environment in buildings To overcome this problem developing the energy-saving smart windows and some other related devices becomes more and more important Liquid crystals have a great potential in developing photonic devices which can control the optical behavior of liquid crystals by external stimulation and be used as smart devices In this study we have fabricated a series of bistable cholesteric liquid crystal devices using dual frequency nematic liquid crystal HEF951 and a synthesized chiral ferroelectric liquid crystal 3C by photo-polymerization Dual frequency nematic liquid crystal offers a new way to operate these bistable liquid crystal devices through high or low frequency alternative electric field at driving voltage Chiral ferroelectric liquid crystal 3C was used for the inducing of nematic liquid crystal forming cholesteric liquid crystal phase and decreasing the driving voltage and response time of the fabricated bistable liquid crystal devices Formation of polymer network via the assistance of ferroelectric LC in these bistable liquid crystal devices the response time was significantly decreased The fabricated bistable liquid crystal devices show stable opaque focal conic state and stable transparent planar state without any energy consumption For 1BC cell after driving with 66 V the cell shows 78 33% and 9 39% transmittance for planar state and focal conic states respectively Switching of the bistable liquid crystal cells from one state to another state was achieved by one-step voltage bias with various frequencies Furthermore the response time of 1BC cell was calculated as 2 3 ms The result suggests that the fabricated bistable liquid crystal devices are good enough to be applied in liquid crystal displays and other related smart devices

Date of Award	2020
Original language	English
Supervisor	Jui-Hsiang Liu (Supervisor)