Uniform and fast switching for window-size smectic A liquid crystal panels utilising the field gradient generated at the fringes of patterned electrodes
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Li, K., Pivnenko, M., Chu, D., Cockburn, A., & O'Neill, W. (2016). Uniform and fast switching for window-size smectic A liquid crystal panels utilising the field gradient generated at the fringes of patterned electrodes. Liquid Crystals, 43 735-749. https://doi.org/10.1080/02678292.2016.1142012
A method to enable smectic A (SmA) liquid crystal (LC) devices to switch uniformly and hence fast from the clear state to a scattered state is presented. It will allow the reduction of the switching time for a SmA LC panel of 1x1 m2 changing from a clear state to a fully scattered state by more than three orders to a few tens of milliseconds. Experimental results presented here reveal that SmA LC scattering initiates from the nucleated LC defects at the field gradient of the applied electric field usually along the edges of the panel electrode and grows laterally to spread over a panel, which takes a long time if the panel size is large. By patterning the electrodes in use, it is possible to create a large number of field gradient sites near the electrode discontinuities, resulting in a uniform and fast switching over the whole panel and the higher the pattern density the shorter the panel switching time. For the SmA LC panels used here, the ITO transparent electrodes are patterned by laser ablation and photolithography, respectively. It is shown that the defect nucleation time is much shorter than the growth time of the scattered region, hence it is possible to use the density of the field gradient sites to control the uniformity and switching time of a panel. Furthermore, the patterned SmA panels have a lower switching voltage than that of the non-patterned ones in general.
smectic A liquid crystal, field gradient effect, scattering, patterned electrodes
The authors would like to thank the UK Engineering and Physical Sciences Research Council (EPSRC) for the support through the Platform Grant for Liquid Crystal Photonics (EP/F00897X/1) and Dr Anthony Davey for providing the organic SmA LC and Dow Corning Corp. for providing the siloxane-based SmA LC used in this study. The authors would also like to thank Dr Stuart Speakman for the helpful discussions.
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External DOI: https://doi.org/10.1080/02678292.2016.1142012
This record's URL: https://www.repository.cam.ac.uk/handle/1810/253337
Attribution 2.0 UK: England & Wales
Licence URL: http://creativecommons.org/licenses/by/2.0/uk/