Induced Alignment in Nematic Liquid Crystal by Dichro Disperse Orange 3 Azo dyeic

Abstract

We have developed a new type of liquid crystal heterogeneous system which contains nematic liquid crystal doped with disperse orange 3 azo dye. The suspension of azo dye molecules in nematic liquid crystal shows a unique property of self-orientation in the liquid crystal system which can be observed in the optical textures taken under crossed polarizer in polarizing optical microscope. This alignment is self sustained by dye molecules in liquid crystals without any need of surface treatment technique. Hence this newly developed material can be used in the displays designing without any need of additional surface treatment. Optical textures investigations shows the spontaneous anchoring transition from planar to homeotropic alignment with increase in dye concentration from 0.3 to 0.5 weight %. The order parameter S=0.9 of 0.5% dye doped nematic liquid crystal shows perfectly vertical liquid crystal alignment in homeotropic state, which was confirmed by polarizing fluorescence spectroscopy with the help of parallel (Ivv) and perpendicular component (IVH) with optical rotation of the emitted PL intensity, when polarized excited molecules falls on the dye doped nematic liquid crystal sample. Hence the resulting suspension combines the unique anisotropic properties of nematic liquid crystals and azo-dyes. The optoelectronic behavior of dye doped nematic liquid crystal shows the electrically tuning of photoluminescence contrast with application of electrical square wave pulse.