Rubbed polyimide alignment layer

Electro-optic effects induced by doping liquid crystals with one-dimensional metal nanoparticles were not only investigated in standard electro-optic test cells, but also in costume-made cells consisting of a thin layer of liquid crystal either deposited onto a thin film of alumina with embedded GNRs [443], or using rubbed polyimide alignment layers modified with solution-cast GNR [444]. In both cases, surface plasmon resonance frequencies of the GNR integrated into these liquid crystal cells could be electrically controlled. 

FIGURE 10.19. Polarized absorption spectra for a film of PF2/6 oriented on a rubbed polyimide alignment layer. The spectra were measured for light polarized parallel (filled circles) and perpendicular (open circles) to the rubbing direction. (From Ref. 4.)... 

Pattison, L.R. et ah. Temperature dependence of the ordering of semiconducting fluorene-thiophene copolymers on rubbed polyimide alignment layers, in Organic photovoltaics VI, ed. Z.H. Kafafi and P.A. Lane, SPIE, Bellingham, WA, 2005, 143-150. 

ITO electrode and then flattened by a polymer film. For phase-only modulation, homogeneous LC alignment should be used. Thus, the polymer surface and the bottom ITO glass substrate with a thin polyimide alignment layer are rubbed in anti-parallel directions. The cell gap is controlled at 18 pm by Mylar spacers and hermetically sealed using ultraviolet-curable glue. To achieve a fast response time, a dual-frequency liquid crystal (DFLC) is used. The physical properties of the DFLC mixture are summarized as follows crossover frequency /<, 5 kHz, An 0.285 (at X=633nmand T=22°C), and dielectric anisotropy Ae = 4.73 at/= 1 kHz, and Ae = -3.93 at 50 kHz. 

Paek SY. Comparative study of rubbing parameters on polyimide alignment layers and liquid crystal alignment. J. Ind. Eng. Chem. 2001 7 316-325. 

Enhancement of bistability by doping polyimide alignment layers with a charge transfer complex (CTC) and an appropriate rubbing process has been reported [34]. 

A standard TN-LCD consists of a nematic liquid crystal mixture of positive dielectric anisotropy contained in a cell with an alignment layer on both substrate surfaces, usually rubbed polyimide, crossed polarisers and a cell gap of 5- 0fim, see Figure 3.7. The nematic director is aligned parallel to the direction of rubbing in the azimuthal plane of the device. The alignment layer induces a small pretilt angle (6 1-3°) of the director in the zenithal plane. The... 

Anisotropic orientation of PFs may also have been achieved in LB films and by LB film transfer methods [112] but in this case uniaxial alignment has not as yet been achieved. Alignment can also be achieved using a top down approach rather than a bottom up strategy. Samuel and coworkers [113] used a rubbed polyimide surface coated with an intervening thermotropic liquid crystal layer to produce uniaxial orientation starting at the top surface of a PF2/6 LED device. 

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