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In a liquid crystal cell used for LCD the conductive substrates, usually made of ITO, are in contact with the liquid crystal. The question is: when a voltage is applied to the electrodes to reorient the molecules is there any current flowing through the liquid? The answer should be positive because LCs are conductive materials. But I know that the molecules should reorient themselves under an applied electric field for example between two plates like a capacitor even without being in contact with the LC. So why the electrodes are placed in contact with the LC and why LCDs consume electricity?

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LCs materials are dielectric. But they are not perfect insulators and have some non-zero conductivity, allowing a leakage current to flow, slowly discharging the capacitor. This is caused by mobile ions in the liquid crystal and inside the polyimide layer [2]. Infact a liquid crystal cell can be modeled electrically as this circuit:

               Rl
         _____WWW_____
         |           |
         |     Cl    |
     O--------||---------O

References:
http://www.lintech.org/comp-per/03lcd.pdf‎ p.10-11
http://www.emdmillipore.com/showBrochure?id=200908.037 p.9

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