Thickness Dependent Electro-Optical Behaviour of Homeotropically Aligned Nematic Liquid Crystal
Ankit Rai Dogra, Vandna Sharma, Ridhima Gahrotra, Partha Khanra, Ankit Dogra
Abstract
The homeotropically aligned liquid crystal (LC) display devices are of great interest in recent time. Thus, in the present work, the thickness dependent electro-optical behaviour of nematic liquid crystal (NLC) in homeotropic alignment (HA) has been studied. To achieve the HA of NLC, polyimide (PI) coated ITO glass substrates were used. Consequently, cleaned ITO glass substrates (with thickness of 0.7 mm) were used for the fabrication of the LC cells. The pure NLC material (LC-BYVA) was filled into PI coated cells by the capillary injection method. Subsequently, the filled cells were examined with the help of polarized optical microscope (POM), which show the good dark and bright orthoscopic textures of NLC in field ON and OFF states, respectively under cross-polarizers. The conoscopic study of the images also confirmed the perfect HA of NLC molecules. The dark states change to good bright state with the change in orientation of NLC director from homeotropic to planar at operating voltages as seen under cross-polarizers. The electro-optical (E-O) study also shows the good contrast ratio (CR) of display cells.