Photoalignment layer

V. Strehmel, B. Stiller, B. Strehmel, A. M. Sarker, and D. C. Neckers, Fluorinated Distyrylbenzenes Containing Copolymers for Photoinduced Formation of Anisotropic Materials as Photoalignment Layers for Liquid Crystals. In Photoinitiated Polymerization, Vol. 847, K. D. Belfield and J. V. Crivello, Eds., American Chemical Society, Washington, DC, 2003, p. 482. 

Fig. 9.11. Polarisation microscope photographs of test displays composed of a patterned photoalignment layer (Staralign 2110 from Vantico) and a uniformly rubbed layer, filled with LC mixture MLC 7700 000 (Merck). The polarisers are crossed, (a) Stripe pattern with line widths of 10 and 3 pm, (b) checkerboard pattern of 10x10 and 100x100 pm.

Fig. 9.20. A schematic of the molecular order of the reactive LC molecules after director patterning. The order is forced to be planar in two domains by a dual domain photoalignment layer. The domains exhibit identical dAn values, but the effective retardation depends on the angle between the main optical axis and the transmissive axis of the polariser.

S.K.-H. Wei, L. Zeng, K.L. Marshall, S.H. Chen, Room-temperature processing of %-conjugated oligomers into uniaxially oriented monodomain films on coumarin-based photoalignment layers. J. Polym. Sci. Part B Polym. Phys. 49, 725-731 (2011)... 

Kawatsuki N, Hamano K, Ono H, Sasaki T, Goto K (2007) Molecular-oriented photoalignment layer for liquid mystals. Jpn J Appl Phys 46 339-341 Kawatsuki N, Nishioka E, Emoto A, Ono H, Kondo M (2012) Blazed surface relief formation in azobenzene-eontaining polymtaie films by asymmetric polarization holography. Appl Phys Express 5 041601... 

Fig. 7.20 Chemical structures and phase transition temperatures of the blue, green and red emitting reactive mesogens and the conducting photoalignment layer...

Fujiwara, T., Loddin, J., Bao, Z. Solution deposited liquid crystalline semiconductors on a photoalignment layer for organic thin-fflm transistors. Appl. Phys. Lett. 90(23), 232108 (2007)... 

N. Kawatsuki, H. Takatsuka, and T. Yamamoto, Thermally stable photoalignment layer of a novel photo-crosslinkable polymethacrylate for liquid crystal display. Japanese Journal of Applied Physics 40, L209 (2001). 

The azimuthal anchoring energy can be measured using a substrate with a rubbed PI alignment layer and that with a photoaligned layer assembled with a twisted nematic configuration [35] (Figure 3.12). 

Another factor, which determines the anchoring energy of the photoaligned layers is the exposure time. In particular, the azimuthal LC anchoring energy of the azo-dye layers can be substantially varied by changing the exposure time (Figure 3.14) [40]. 

Comparison of the Characteristics of Photoalignment Layers for Different Mechanisms of LC Photoalignment... 

Various Methods for the Experimental Characterization of Photoalignment Layers... 

Table 3.1 Characteristics of photoalignment layers for various mechanisms of LC photoalignment (Chapter 2)...

Polarized electroluminescence (EL) spectra can also be used to characterize the quality of the photoaligned layer. The brightness and polarization ratio of EL is shown to depend on the composition and processing conditions of the alignment layer. Photoalignment provides a non-contact method to achieve macroscopic orientation of the chromophore without mechanical damage. EL with a polarization ratio of 11 1 (Figure 3.20) has been obtained from a fluorene-based nematic network formed by the selective polymerization of diene photoactive... 

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