Time-Dependent Electrical Conductivity of Liquid Crystal Cells*

Liquid crystal devices are becoming increasingly ubiquitous. As a rule, the tunability of such devices is achieved by applying an electric field. This field reorients liquid crystals and changes their physical properties. Ions, typically present in liquid crystals in minute quantities, can alter the reorientation of liquid crystals through the well-known screening effect thus altering the overall performance of liquid crystal devices. To mitigate negative side effects caused by ions in liquid crystals, better understanding of ionic phenomena in liquid crystals is needed. Information about ions in liquid crystals can be obtained by measuring their direct current (DC) electrical conductivity. Electrical measurements of liquid crystals are very non-trivial because they can be affected by numerous factors. A very important factor, often overlooked in existing literature, involves interactions between ions and substrates of a liquid crystal cell. In this talk we present an analysis of how such interactions make DC electrical conductivity of liquid crystal cells time dependent.