Tuning of birefringence, response time, and dielectric anisotropy by the dispersion of fluorescent dye into the nematic liquid crystal

Abstract

In this study, fluorescent dye benzo 2,1,3 thiadiazole has been dispersed into the pure nematic liquid crystal (NLC) 2020, which is composed of fluorinated 4′-alkylphenyl-4-isothiocyanatotolanes, in three different concentrations. Electro-optical and dielectric parameters have been investigated in the present work. Birefringence has been calculated by transmittance technique for pure and dye-dispersed system, and found to be increased for dispersed system. This is the key finding of the present investigation. In this work, response time has also been calculated by optical switching method and found to be decreased after the dispersion of fluorescent dye into the pure NLC 2020. Contrast ratio has also been measured here and found to be increased for the dispersed system. Relative permittivity has been found to be decreased after the dispersion of dye. Dielectric anisotropy has also been calculated for pure NLC and dye–NLC dispersed system, and found to be decreased for dispersed system. The present investigation may be helpful in the improvement of response time of liquid crystal-based devices.