Nematic phase liquid crystal composition

Abstract

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.

Description

technical field [0001] The present invention relates to liquid crystal compositions, especially nematic liquid crystal compositions, as liquid crystal materials. Background technique [0002] Currently, liquid crystal displays are widely used, and liquid crystal materials are developing rapidly, especially nematic liquid crystal materials are developing the fastest. Nematic twisted nematic (TN for short) displays are known from M. Helfrich, Appl. Phys. Lett., 18, 127 (1971). In the TN display mode, the manufacturing process of TN displays is relatively simple, the process control is relatively easy, and the selection of liquid crystal materials is relatively wide and common. The types of liquid crystals used in the TN display mode include esters, biphenylnitriles, pyrimidines, dioxanes, cyclohexylbiphenyls, and the like. Various types of liquid crystal monomers have the following performance characteristics: [0003] (1), biphenyl liquid crystal: low viscosity, large bire...

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Problems solved by technology

[0005] (3) The birefringence (Δn) of pyrimidine liquid crystals is large, the viscosity is large, and the low temperature performance is not good;

[0006] (4) There are many types of ester monomers, which can be combined according to different needs, but the disadvantage is that the viscosity is high

[0017] However, at present, the synthesis of new liquid crystal molecules is becoming more and more difficult, and there are relatively few compounds with practical application value. It is difficult for a single compound to meet the stringent requirements in practical applications. Can make up for the lack of mutual performance

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