The LCD' require an alternating feild to be applied across them.
The LCD to function must get a feild across it , the direction of feild is not a concern.
Also due to the nature of the LCD crystal, if only one direction of feild is applied the pixel gets burnt and the impression remain of the LCD panel.
The voltages that are needed for LCD are bacically Dc but the direction in frames of the voltage get reversed.
Hope it helps
thx, ur post was helpful. can u plz explain how the no. of bias voltages is related to the mux ratio (i.e number of common planes). detailed explanation will be highly appreciated (in-case u hav tym fr dat )