Nematic planar aligned - layer

Regions in a liquid crystal having a specific cellular periodic flow-pattern in the form of long rolls induced by the application of an electric field perpendicular to a nematic layer with an initial planar alignment of the director. 

Tuning of the pre-tilt angle at the interface was also demonstrated by doping commonly used polyimide alignment layers with POSS nanoparticles [339]. In addition, the fabrication of a tunable liquid crystal flat microlens was achieved by placing a drop of a nematic liquid crystal doped with POSS nanoparticles onto a substrate inducing planar alignment (local HAN mode) [340]. Simultaneously, Takatoh and co-workers extended this concept to a series of metal oxide... 

The electrode surfaces of a normal LCD sandwich cell d 8-10 pm) are coated with an alignment layer in order to induce a planar alignment of a host (chiral) nematic mixture containing the dichroic dye of positive dichroism and a chiral dopant. Due to the absence of polarisers a very thin mirror can be incorporated within the cell on top of the rear glass plate electrode in direct contact with the guest-host mixture, see Figure 3.15. 

Homogeneously planar oriented nematic elastomers have been prepared using a procedure very similar to that presented above. As alignment layers, unidirection-ally rubbed polyimide or rubbed poly(vinyl alcohol) were used [14]. 

In most experiments (and applications) a nematic layer is sandwiched between two solid (glass) surfaces supporting transparent electrodes. Special surface coatings and/or treatments allow control of the director alignment at the bounding plates. There are two basic geometries the planar one where n is parallel to the surfaces (usually along x) and the homeotropic one where n... 

Static force [45,50,51,57] and friction properties [45,46,51,57-59] have been extensively studied in thermotropic nematics. The surface anchoring conditions were symmetric, with both mica sheets inducing either planar or homeotropic alignment. Bare mica naturally induces planar anchoring on cyanobiphenyls such as 5CB the liquid crystal optical axis orients at abont 7t/6 with respect to the slow optical direction of a (birefringent) freshly cleaved mica sheet [60]. A homeotropic ahgnment can be obtained by adsorbing a mono-layer of surfactant [45,50] on mica. 

Flexoelectric patterns also exist for nematic layers with asjrmmetric boundary conditions, i.e. with homeotropic anchoring on one surface and planar anchoring on the other one hybrid-aligned nematics).The critical voltage and the critical wave number obtained with the one-elastic-constant approximation are in a good agreement with experimental re-sults. ... 

Fig. 11.2 Normal light incidence on a planar layer of a nematic liquid crystal with homeotropic (a) and tilted (b) alignment (k is light propagation vector, e is light polarization vector, n is the director)...

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