Studies on inter-dependency of electrooptic characteristics of orange azo and blue anthraquinone dichroic dye doped polymer dispersed liquid crystals

The optical properties of dyes dissolved in polymer dispersed liquid crystals (PDLCs) typically required fulfilling their absorption properties, degree of alignment and stability for practical applications. Reported herein is the absorption and electro optic behaviour of dye doped PDLCs prepared by equal weight ratio of nematic liquid crystal (LC) and photo-curable polymer (NOA 65) with different weight concentrations (0.0312, 0.0625, 0.1248, and 0.2494%) of azo and anthraquinone dyes. Considering Beer's law, OFF state absorption coefficients were measured followed by dyes' extinction coefficients. Higher absorption coefficient of azo dye doped PDLCs with dye concentrations (0.1248 and 0.2494%) resulted in superior contrast ratio (CR) as compared with anthraquinone dye doped PDLCs. However, at lower concentrations (0.0312 and 0.0625%) of anthraquinone dye, ON state transmittance of dye doped PDLCs is more dominating which resulted in higher CR at these concentrations. The experimental results were found be consistent with the theoretical results. In addition, inter-dependency among transmission, absorption coefficient, CR, applied voltage and response time characteristics of azo and anthraquinone dye doped PDLCs have been discussed and analyzed.