摘要:

Active Matrix (AM) LCDs and STN LCDs are the leading display technologies for portable applications such as notebook computers. Recently, new LCD device configurations and new LCD operation modes have been introduced. The existing technologies and the new LCD operation modes require improved liquid crystal materials. The history of liquid crystals for display applications and recent progress in new liquid crystal structures is presented.

ISSN:0267-8292    

DOI:10.1080/026782998207613

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Research on mesogens and mesophases began with the surprising observation of a fluid and birefringent phase formed by a pure compound having a calamitic (rod-like) molecule. The structures of the smectic A, nematic and cholesteric phases which emerged after this discovery were elucidated essentially by observations with a polarizing microscope. Smectic polymorphism was also established by microscopic observations. The structures of the different smectic mesophases previously predicted theoretically, was then obtained further type of purposely designed mesophase was the pyramidic type, also exhibiting a rich polymorphism. Research on mesogens and mesophases is a field in continuous expansion. main historical results on the are listed here. The discotic mesophase, and its polymorphism observed. A

ISSN:0267-8292    

DOI:10.1080/026782998207622

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We have performed time resolved diffraction experiments in order to obtain a better insight upon the metastable phases surrounding some thermotropic mesophases of cubic Ia 3 d and Im 3 m symmetries. These metastable phases are columnar hexagonal, smectic or tetragonal, depending on the nature of the mesogenic molecule. Moreover, it appears that the structure of the cubic phase of the 4-alkyloxybiphenyl-4-carboxylic acids previously labelled smectic D varies with the lateral group substituted on the biphenyl core.

ISSN:0267-8292    

DOI:10.1080/026782998207631

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The structure of dispersed liquid crystal droplets elasticity, surface tension, and surface anchoring. For sufficiently large droplets with radius R K / W a, where K is the bulk elastic constant and W a is the anchoring coefficient, the surface terms prevail. As a result, the equilibrium states of large droplets contain topologically stable defects. Application of topological theorems to and hedgehogs is reviewed. is controlled by a balance of the bulk defect structures, e.g. monopoles, boojums

ISSN:0267-8292    

DOI:10.1080/026782998207640

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

Defects are a universal feature in systems of broken equally well in liquid crystals and cosmological theories in both systems are reviewed. It is reported crystals to check theories on the defect evolution of the early universe and how in this way they have contributed considerably to the insight liquid crystals. symmetry. They occur for example field theories. The basic facts of defect how cosmologists have used liquid into defect creation and dynamics in

ISSN:0267-8292    

DOI:10.1080/026782998207659

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We have discovered a spontaneous chiral ordering in thermotropic nematic liquid crystals forming hydrogen bonds, namely in trans -4-alkylcyclohexanecarboxylic acids, which do not contain any chiral group in the molecular structure, and have suggested a possible explanation of this phenomenon. The investigation was performed by polarizing light microscopy, using cells with glass substrates treated to give a uniform planar alignment in the nematic phase. On cooling from the isotropic phase, two types of nematic domains with different alignment were found to grow: some possessing a unidirectional planar orientation as expected, and others with a spontaneous twisted molecular arrangement. The appearance of the twisted domains and the sense of their twist were random, i.e. they always emerged in various regions of the cell with different twist sense: thus, they cannot be regarded as induced by stable defects in the surface aligning film. With the coalescence of the nematic droplets, the number of the domains with the spontaneous twist very quickly characterized by different handedness transformed into a racemic domain with uniform planar alignment. Here the explanation of the macroscopic texture is given in terms of molecular structure, based upon the ability of the carboxylic acids to organize through hydrogen bonds into not only dimers, but also trimers and oligomers. The microscopic structure influences the macroscopic twisted organization of the director inside the domains, and the surface lies normally to the helix axis. A brief review is given of work done in the fields of hydrogen bonded liquid crystals and of order transitions, together with a Landau-de Gennes model describing the mechanism of the spontaneous chiral ordering. decreased, since two chiral domains

ISSN:0267-8292    

DOI:10.1080/026782998207668

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

A brief review is presented of theoretical predictions and experimental observations concerning polar (pyroelectric, ferroelectric and antiferroelectric) achiral mesomorphic phases.

ISSN:0267-8292    

DOI:10.1080/026782998207677

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

The chromophoric biheterocycle 2,5-dihydropyrrolo\[3,4-c]pyrrole-1,4-dione widely variable basic core structure has been introduced into liquid crystal research and the first eight calamitic examples of thermomesomorphic derivatives are presented and discussed. (DPPD) as a

ISSN:0267-8292    

DOI:10.1080/026782998207686

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor

摘要:

We have performed a structural study of the mesophases of some isomeric hexa-substituted phenanthrenes. Evidence for a new hexagonal columnar mesophase with three columns per unit cell was found in a chiral isomer. Moreover, a rectangular columnar phase with four columns per lattice, similar to the low temperature mesophase of a hexa-substituted rufigallol, was found in a different material. The relations between the structures and the electro-optical behaviour of the different mesophases are discussed.

ISSN:0267-8292    

DOI:10.1080/026782998207695

出版商:Taylor & Francis Group    

年代:1998

数据来源: Taylor