Liquid Crystal Light Modulators: Revised Edition

Author(s): Wiktor Piecek

DOI: 10.2174/9789811470226120010006

Complementary Method of Assessment of Frank Elastic Constants in Nematic Liquid Crystals

Pp: 8-30 (23)

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Abstract

SHS investigation development is considered from the geographical and historical viewpoint. 3 stages are described. Within Stage 1 the work was carried out in the Department of the Institute of Chemical Physics in Chernogolovka where the scientific discovery had been made. At Stage 2 the interest to SHS arose in different cities and towns of the former USSR. Within Stage 3 SHS entered the international scene. Now SHS processes and products are being studied in more than 50 countries.

Abstract

new method for quick and accurate measurements of splay (S), twist (T) and bend (B) elastic constants of nematic liquid crystals (NLC) is proposed. The main concept relies on utilizing an electric field only and on determining magnitudes of nematic elastic constants from threshold fields for Freedericksz transitions in a single, hybrid, In-Plane-Switched (IPS) cell. In Hybrid In-Plane-Switched (HIPS) cell, the deformations of an investigated LC are optically monitored while driven by three separated pairs of electrodes. Two of them are interdigitating ones. Due to the appropriate IPS electrodes and boundary conditions on them, the splay, twist and bend elastic constants can be measured without allaying the magnetic field. In this chapter, we describe the layout of HIPS measuring cells and the results of tests conducted on them using 5CB, 6CHBT (with Δε > 0) and DE (with Δε < 0).

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