Nematic Liquid Crystal Materials

New materials were also required for AMTFT displays, since the materials existing at the time were too low in resistivity, too high in viscosity and insufficiently stable. Very high resistivity is required because the TFT maintains the charge on the 

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Doping of nematic liquid crystal materials ZLI-389 and K15 with 30a resulted in stable cholesteric phases. The cholesteric phase was induced by the addition of 0.7 wt% 30a to ZLI-389 at 51-54 °C, and the phase was stable for many hours. When... 

Perfluoroalloxy liquid crystals were prepared by the Williamson ether synthesis using perfluoro iodopropene. These materials can be mixed with nematic liquid crystal materials to provide liquid crystal compositions having low viscosity, low refractive index anisotropy, high dielectric anisotropy, and broad nematic phase ranges. 

A recent observation has been that not all porphyrin LC phases are discotic. Thus 5,15-meso-substituted porphyrins have been prepared which show a variety of smectic phases that are not discotic. The porphyrin macrocycle could be acting to impose biaxial symmetry within the meso-phase, which makes the new porphyrins of great interest as new nematic liquid-crystal materials. 

The authors wish to thank Mr. M. Sato and Mr. H. Morishita for their helpful suggestions and advice. They also acknowledge the considerable support of Mr. H. Sato and Mr. U. Fujita (Dai-Nippon Toryo) for supplying the nematic liquid crystal materials. 

Conway, B.E., 1970, Some aspects of the thermodynamic and transport behaviour of electrolytes, "Physical Chemistry Vol. 9A/Electrochemistry, Eyring H., ed.. Academic Press, New York. Creagh, L.T., 1973, Nematic liquid crystal materials for displays, Proc. I.E.E.E., 61 814. 

L. T. Creagh. Nematic Liquid Crystal Materials for Displays, Proc. IEEE, Vol. 61, p. 814 (1973). 

The above overview of nematic liquid crystal material development for field-effect LCDs from 1970 to 1995 is far from being complete. Many interesting and important aspects which advanced nematic liquid crystal R D—especially those which have not made it into the nematic mainstream—are missing in this much too short review. The following two examples serve as an illustration for two R D efforts made by the author that did not make it into the mainstream of LCD development. 

Qi, H. and Hegmann, T. (2006) Formation of periodic stripe patterns in nematic liquid crystals doped with functionalized gold nanopartides. Journal of Materials Chemistry, 16, 4197-4205. 

Thermotropic cholesterics have several practical applications, some of which are very widespread. Most of the liquid crystal displays produced use either the twisted nematic (see Figure 7.3) or the supertwisted nematic electrooptical effects.6 The liquid crystal materials used in these cells contain a chiral component (effectively a cholesteric phase) which determines the twisting direction. Cholesteric LCs can also be used for storage displays utilizing the dynamic scattering mode.7 Short-pitch cholesterics with temperature-dependent selective reflection in the visible region show different colors at different temperatures and are used for popular digital thermometers.8... 

The classical cholesteric phase materials show only a weak anisotropic interaction with electric fields and hence are of limited use in electro-optical response applications. Cholesteric phases for these outlets are consequently produced by adding chiral dopants to nematic liquid crystals. 

Taushanoff S, Le KV, Williams J, Twieg RJ, Sadashiva BK, Takezoe H, Jakli A (2010) Stable amorphous blue phase of bent-core nematic liquid crystals doped with a chiral material. J Mater Chem 20 5893-5898... 

As shown previously, nematic liquid crystals reorient easily in weak electric fields and their high birefringence provides an efficient electro-optic mechanism that makes them excellent candidates for photorefractive materials. However, charge transport relies on the generation of mobile anions or cations. These mobile charges obey the current density (/) equations given by [82,83]... 

The birefringence of the liquid crystals is controlled electronically. Either ferroelectric or nematic liquid crystals are used for the tunable retarders. By varying the input voltage to the liquid crystals the birefringence of that material can be changed to vary the retardation and change the interference pattern in such a way as to scan the spectral region of interest. 

The origins and development of the concept of carbonaceous mesophase, as derived from discotic aromatic nematic liquid crystals, enable applications to be made to industrial processes. The world availability of pitch materials is such that there is an abundance of pitch which produces cokes of little commercial value. A major incentive for research into the Chemistry of mesophase formation is the commercial up-grading of such pitches and the development of specialized pitches. Structure in cokes is described in terms of optical texture. 

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