Nematic liquid crystals vertical alignment

ANODIC POROUS AND PILLAR STRUCTURES FOR VERTICAL ALIGNMENT OF NEMATIC LIQUID CRYSTALS... 

C.-W. Kuo, S.-C. Jeng, H.-L. Wang, C-.C. Liao, Application of nanoparticle-induced vertical alignment in hybrid-aligned nematic liquid crystal cell. Appl. Phys. Lett. 91, 141103 (2007)... 

When a discotic liquid crystal is sandwiched between two substrates (or exposed to air), the direction of the uniaxial axis can be controlled by alignment layers, external electric fields, and chiral dopants [46,47]. It is therefore possible to develop discotic compensation films with spatially varied uniaxial axis orientations. For example, Fuji Photo Film Co. developed discotic compensation films for TN LCDs. In both the TN display and discotic compensation film, the liquid crystal directors vary in the vertical direction. Each layer of nematic liquid crystal with a certain director orientation is compensated by a layer of discotic liquid crystal with the same director orientation. 

M. F. Schiekel and K. Fahrenschon, Multicolor Matrix Displays Based on Deformation of Vertically Aligned Nematic Liquid Crystal Phases, Digest 1972 Soc. for Information Display International Symp., San Francisco, Calif., p. 98. 

In the vertically aligned mode (VA mode), the long axis of rodlike hquid crystal molecules is oriented perpendicular to the glass substrate. In general, nematic liquid crystals with a negative anisotropy of the dielectric constant are used. 

Oh SY, Kang SW. Photoreactive self-assembled monolayer for the stabilization of tilt orientation of a director in vertically aligned nematic liquid crystals. Opt Express 2013 21 31367-74. 

Fig. 5.21 Nematic phase. Typical photo [6] of a diffiaction pattern for a ncanatic liquid crystal with the director aligned vertically (a) and the scheme explaining this pattern (b)...

S. H. Lee, K. H. Park, J. S. Gwag, et al., A multimode-type transfleetive liquid crystal display using the hybrid-aligned nematic and parallel-mbbed vertically aUgned modes, Jpn. J. Appl. Phys., part 1, 42, 5127 (2003). 

If the liquid crystal molecules and the rodlike molecules are aligned vertically, there is a possibility that a novel biaxial nematic phase exists on the uniaxial nematic phases Ni and N2. So far, biaxial nematic phases have been attracting attention for molecules having a biaxial molecular shape (plate-shaped or discshaped molecules) [53, 54], but based on the above discussion, the novel biaxial phase can also be produced in the combinations of molecules with uniaxial symmetry. 

Figure 4.2 Preparation of pretilted vertical alignment for VAN-LCD by a photoalignment method [11]. Reproduced from V. A. Konovalov, V. G. Chigrinov, H.-S. Kwok, H. Takada, and H. Takatsu, Photoaligned vertical aligned nematic mode in liquid crystals. Japanese Journal of Applied Physics 43, 261 (2004), Institute of Pure and Applied Physics...

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