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Dynamics and uniformity of reorientation in liquid crystal cells with PVK alignment layers
,Sergei S. Slussarenko
School of Physics and Astronomy, University of Southampton
School of Physics and Astronomy, University of Southampton, UK
23Institute of Physics, National Academy of Sciences,Kiev, Ukraine
We present experimental results on dynamics of Freedericksz transition in liquid crystal cells with alignment layers made of poly(N-vinyl carbazole). DC electric field causes the build-up of, unusually strong, surface charge layers on a liquid crystal-polymer interface that screen liquid crystals from the external field. The process of surface charge build-up and discharge in illuminated areas takes place due to low dark conductivity and high photoconductivity of poly(N-vinyl carbazole), rather than due to its photorefractive nature. If the illuminating beam has a Gaussian profile, reorientation starts from a very small volume, with a clear disclination line in the reorientation spot.