2, 3-Dicyanohydroquinone Derivative Liquid Crystals Having Strong Negative Dielectric Anistropy

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Abstract
Three groups of liquid crystalline derivatives of 2,3-dicyanohydroquinone were synthesized. The dielectric anisotropy values, δε's, for these compounds were estimated to be around −20 by extrapolation. Some basic evaluations of these compounds, in view of their application as component materials for the practically usable nematic mixtures of highly negative δε, were made using their solution in a substituted phenyl cyclohexanecarboxylate nematic mixture; δ ε. viscosity, dichroic ratio of dyes, driving voltages, and response times, are described in relation to their molecular length. By use of several selected members of these compounds in summe of about 20 wt% in low viscosity base nematics, one can make practical nematic compositions having δε of −5 and viscosity of 40 cp at 20°. The guest-host display device can be driven with 3 volts at acceptable response times of 100-200 milliseconds at room temperatures, to give positive color contrast, i. e. colored in on-state.

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