摘要:

The pre-transitional Kerr effect in K18 is examined using a novel technique. Mixed polarisation grating coupled guided modes are excited within the liquid crystal layer, these are probed for small changes in position using a differential technique which resolves induced birefringences to an accuracy of 5 × 10−8. The experiment is performed at several different temperatures in order to characterize this pre-transitional behaviour, and from this, one of the Landau expansion coefficients can be found.

ISSN:1058-725X    

DOI:10.1080/15421409208048675

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We establish some phenomenological relationships for the scattering properties of select films of nematic dispersions. For powered films of similar structure but containing different LC's, angle and polarization-dependent transmission measurements show that film scattering depends simply on the refractive index mismatch between the polymer and nematic. We find little wavelength dependence on the film scattering cross section when the refractive index mismatch between LC and polymer is small. We examine the importance of the refractive index gradient produced by anti-correlated LC droplets as a factor in the film scattering of unpowered films. We find that in unpowered films it appears that these gradients are at least as important in contributing to film scattering as the more familiar LC/polymer refractive index gradient.

ISSN:1058-725X    

DOI:10.1080/15421409208048676

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

In a normally white (NW) twisted nematic (TN) liquid crystal displays (LCDs), there are two optical eigenmodes, an extraordinary-ray mode (e-mode) and an ordinary-ray mode (o-mode). With zero or a low-bias voltage as the brightest state of the display, both eigenmodes have insufficient display performance for the analog grayscale application. The former has a large color change as a function of viewing zone. The latter has quite a narrow horizontal viewing zone. By applying a threshold voltage as a bias to represent the brightest level of the e-mode NW, the optical performance in the vertical viewing zone was much improved. Further optimization of the d*delta-n for this mode of operation resulted in a small color change and a wide viewing zone by choosing d*delta-n = 0.47 micrometers. We conclude that the threshold-voltage biased e-mode NW of the first-minimum thin-film-transistor (TFT) driven TN can achieve a wide viewing angle for analog-grayscale applications.

ISSN:1058-725X    

DOI:10.1080/15421409208048677

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

We investigate the third-order nonlinearity of DANS and DAN2 side-chain polymers by tunable third-harmonic generation and nonlinear distributed coupling. The large third-order susceptibility can be interpreted in terms of microscopic cascading of second-order hyperpolarizabilities.

ISSN:1058-725X    

DOI:10.1080/15421409208048678

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The role of hydrodynamic couplings and fluctuations on the transient dynamics of the magnetic Freedericksz transition is analyzed for three different geometries. An anisotropic response for the transverse orientational fluctuations of the director at finite wave numbers and for an arbitrary velocity field is also described.

ISSN:1058-725X    

DOI:10.1080/15421409208048679

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The dynamics of nematic defects may not seem to be too important for device applications, if one knows how to avoid them. This may change in future, when disclinations can be used to store and process information, which appears possible due to their high entropy. The application of the differential equations of nemato-dynamics is however interesting from a theoretical point of view: it elucidates the capabilities and also the weaknesses of the present theory.

ISSN:1058-725X    

DOI:10.1080/15421409208048680

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The alignment of a nematic liquid crystal MBBA on dipalmitorylphosphatidylcholine (DPPC) monolayers has been investigated. The monolayers are prepared using Langmuir-Blodgett techniique. In the liquid-expended state, the monolayers induce homeotropic alignment of liquid crystal molecules. While in the liquid-condensed and the solid-condensed states, the homeotropic alignment disappears. The experimental result is useful to select a suitable aligning layer for fabricating liquid crystal devices.

ISSN:1058-725X    

DOI:10.1080/15421409208048681

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

Spectroscopic absorption measurements in the wavelength range from 700 to 300 nm are used to study the orientation of optically nonlinear side-chain groups in an acrylic polymer and dye guest molecules in a polymer matrix by corona poling process. The time stability and the annealing behaviour of these films are measured. The poling process produces efficient orientational order at room temperature of the acrylic side-chain polymers. With stepwise annealing up to poling conditions the orientation order was measured. The guest-host systems show a different behaviour.

ISSN:1058-725X    

DOI:10.1080/15421409208048682

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

A set of liquid crystals and polymer complex (LCPC) films which have different polydomain focal conic textures and different polymer wall were prepared. The electro-optical properties of cholesteric liquid crystals and polymer complex were investigated using OS - 6411C Digital Storagescope with He-Ne laser and candescent light. These LCPC films may have various threshold-voltage, electro-optical response time and contrast ratio which depend on LCPC's composition, especially the focal conic liquid crystal textures in polymer matrix and polymer wall effect. Among these, the best LCPC film was developed which has a very low driving-voltage, quick response time and high contrast ratio. The results reveal that the cholesteric twisting power and polymer wall effect are most important factors for electro-optics of LCPC films.

ISSN:1058-725X    

DOI:10.1080/15421409208048683

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor

摘要:

The forward stimulated O → E scattering with the replication of wave front in nematic liquid crystal 5CB was observed for λ = 0.63μm radiation with very low intensity, 0.03W. The scattering was due to short- period (3μm) gratings of director and therefore the frequency shift was 30Hz, buildup time was 0.04 seconds.

ISSN:1058-725X    

DOI:10.1080/15421409208048684

出版商:Taylor & Francis Group    

年代:1992

数据来源: Taylor