Positive Ae liquid crystals for AMLCD

Positive Ae LCs have been used in twisted nematic (TN) [31] and in-plane switching (IPS) [32,33] displays, although IPS can also use negative Ae LCs. For thin-fUm-transistor (TFT) based displays, the employed LC material must possess a high resistivity [34]. Fluorinated compounds exhibit a high resistivity and are the natural candidates for TFT LCD applications [35,36]. A typical fluorinated LC structure is shown below  

For the vertical alignment [39], the LC employed should have a negative dielectric anisotropy. From Equation (6.27), in order to obtain a negative dielectric anisotropy, the dipoles should be 

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