Determination of the difference of flexoelectric coefficients in a nematic liquid crystal using a conoscopic technique

The conoscopic images of twisted nematic liquid crystal devices filled with E7 are analysed under the application of in-plane electric fields. The differences observed between the images for positive and negative applied fields are attributed to the flexoelectric effect. By comparison of the conoscopic images with theoretical predictions made using an extended Jones technique, the sign and magnitude of the difference between the splay and bend flexoelectric coefficients is determined for E7.