Why alternating current is used to switch cells that contains liquid crystals? Question might look silly but I did not find simple answer.
Does this help?
http://www-g.eng.cam.ac.uk/CMMPE/displays2d.html
In most cases your are interested in evaluate the two molecular stable states of the liquid crystalline compounds, when they are bistable. If you apply a direct current, you will see how it behaves in that especific applied field, you will reach a stationary state, to get the other stable state you need the opposite field, then it's usual to use an alternating current to get both results and some other features from this systems, like if you are interested in know how fast is the swiching, for futher applications in on/off technologies, for example. Hope it helps somehow
AC is used to switch LCD's as DC would result in electrolysis of the LC and one-way degradation of the ITO electrodes. I worked in this industry for 7 years.
AC is primarily used to prevent charge induction of the molecules. However, DC depending on the strength, not only promotes charge induction but also leads to electrokinetics of the system as well. Since the surface treatment of LCD's is very crucial and is a basic necessity in their functioning, one can not afford the displacement of LC molecules which would eventually compromise the efficiency of LCD's and hence render them dysfunctional over DC field exposure.
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