The invention relates to a nematic
liquid crystal combination used for TN, STN, TFT displaying devices, which comprises one of a general formula (I) or / and (II) or a plurality of bicyclo
system derivatives. X' is selected from F and Cl, and F is optimized. Ra, Rb, Ra' and Rb' are respectively and independently selected from
alkyl, alkoxy, alkenyl, alkenoxy, fluoroalkyl, fluoroalkoxy, fluoroalkenyl or fluoroalkenoxy. The combination is characterized in that difluoro chain
hydrocarbon derivatives are used for various displays to result in the lowered low temperature FNP and increased low temperature stability of the combination. Especially under low temperature, the responding time is very fast. In STN displaying, the gradient performance can be improved, and the information capacity of the display can be improved. In the displaying of TN caproic TN type TFT, the gray scale display can be improved and the color expression ability can be enriched.