Dielectric Permittivity and Viscoelastic Measurements of Two Tricomponent Mixtures Consisting of Laterally Fluorinated Terphenyl Derivatives
S. Basak a, P. Dasgupta a, B. Dasa, M.K. Das b and R. Dabrowski c
aDepartment of Physics, Siliguri Institute of Technology, Siliguri, Darjeeling - 734 009, India
bDepartment of Physics, University of North Bengal, Siliguri, Darjeeling - 734 013, India
cDepartment of Advanced Technologies and Chemistry, Military University of Technology, 00-908 Warsaw, Poland
Received: April 14, 2012; in final form: November 5, 2012
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Two tricomponent room temperature nematic eutectic mixtures ABC and ABD with laterally fluorinated constituents A and B were prepared as base mixtures for vertically aligned mode LCD's. The physical properties of these mixtures viz. birefringence, dielectric anisotropy, bend elastic constant, relaxation time and rotational viscosities were determined in order to compare with the optimum values required to achieve the target specifications of VA mode materials. The dielectric anisotropy, Δ ε, and optical birefringence, Δ n, of these mixtures were found to be in the range of (-1.3 to -1.4) and (0.13 and 0.14), respectively, at around 20°C. The figure of merit for the ABD mixture has been found to be higher than that of ABC mixture throughout the entire temperature range. The pretilt angle effect in the physical parameters has also been studied. At T=20°C, the response time decreases to 25% and 35% for mixture ABC for 2° and 5° pretilt respectively in comparison to zero pretilt. On the other hand, at the same temperature for the ABD mixture these values are reduced by 16% and 35%, respectively.

DOI: 10.12693/APhysPolA.123.714
PACS numbers: 61.30.-v, 78.20.Fm, 87.19.rd, 87.19.rf, 83.60.Bc