Effect Of Alignment Layers Research Articles

The influence of orienting layers on blue phase liquid crystals in rectangular geometries

In this paper, the influence of homeotropic and homogeneous orienting layers is presented in a cell filled with chiral nematic liquid crystals stabilized in a blue phase. The change of selective Bragg reflection from red to blue light was observed for homogeneous layers in rectangular geometries. The growth of blue phase crystals domains in a glass cell as well an influence of temperature and the electric field on such a structure, are also presented. Full Text: PDF ReferencesF. Reinitzer, Beitrage zur Kenntniss des Cholestherins, Monatsh Chem. 9, 421-441, (1888). CrossRef J. Yan, M. Jiao, L. Rao, and S.-T. Wu, "Direct measurement of electric-field-induced birefringence in a polymer-stabilized blue-phase liquid crystal composite", Opt. Express 18, 11450-11455 (2010) CrossRef Y. Chen, D. Xu, S.-T. Wu, S.-i. Yamamoto, Y. Haseba, "A low voltage and submillisecond-response polymer-stabilized blue phase liquid crystal", Appl. Phys. Lett. 102, 141116 (2013) CrossRef Y. Huang, H. Chen, G. Tan, H. Tobata, S. Yamamoto, E. Okabe, Y.-F. Lan, C.-Y. Tsai, and S.-T. Wu, "Optimized blue-phase liquid crystal for field-sequential-color displays", Opt. Mater. Express 7, 641-650 (2017) CrossRef V. Sridurai, M. Mathews, C. V. Yelamaggad, G. G. Nair, "Electrically Tunable Soft Photonic Gel Formed by Blue Phase Liquid Crystal for Switchable Color-Reflecting Mirror", ACS Appl. Mater. Interfaces, 9 (45), 39569-39575 (2017) CrossRef E. Oton, E. Netter, T. Nakano, Y. D.-Katayama, F. Inoue, "Monodomain Blue Phase Liquid Crystal Layers for Phase Modulation", Sci. Rep. vol.7, 44575 (2017) CrossRef Q. Liu, D. Luo, X. Zhang, S. Li, Z. Tian, "Refractive index and absorption coefficient of blue phase liquid crystal in terahertz band", Liq. Cryst., Vol. 44, No. 2, pp. 348-354 (2017) CrossRef Y. Li, Y. Liu, Q. Li, S.-T. Wu, "Polarization independent blue-phase liquid crystal cylindrical lens with a resistive film", Appl. Opt., Vol. 51, No. 14, pp. 2568-2572 (2012) CrossRef M. M. Sala-Tefelska, K. Orzechowski M. Sierakowski, A. Siarkowska, T.R. Woliński, O. Strzeżysz, P. Kula, "Influence of cylindrical geometry and alignment layers on the growth process and selective reflection of blue phase domains", Opt. Mater. 75, 211-215, (2018) CrossRef H. Claus, O. Willekens, O. Chojnowska, R. Dąbrowski, J. Beeckman, K. Neyts, "Inducing monodomain blue phase liquid crystals by long-lasting voltage application during temperature variation", Liq. Cryst. 43 (5), 688-693, (2016) CrossRef M. Takahashi, T. Ohkawa, H. Yoshida, J. Fukuda, H. Kikuchi, M. Ozaki, "Orientation of liquid crystalline blue phases on unidirectionally orienting surfaces", J. Phys. D: Appl. Phys. 51 (10), 104003 (2018) CrossRef P. Joshi, X. Shang, J. De Smet, E. Islamai, D. Cuypers, G. Van Steenberge, S. Van Vlierberghe, P. Dubruel, H. De Smet, "On the effect of alignment layers on blue phase liquid crystals", Appl. Phys. Lett. 106, 101105 (2015) CrossRef K. Orzechowski, M.W. Sierakowski, M. Sala-Tefelska, P. Joshi, T.R. Woliński, H.D. Smet, "Polarization properties of cubic blue phases of a cholesteric liquid crystal", Opt. Mater. 69, 259-264 (2017) CrossRef P.-J. Chen, M. Chen, S.-Y. Ni, H.-S. Chen, Y.-H. Lin, "Influence of alignment layers on crystal growth of polymer-stabilized blue phase liquid crystals", pt. Mater. Express 6, 1003-1010 (2016) CrossRef CrossRef

On the effect of alignment layers on blue phase liquid crystals

In the present work, the effect of alignment layers on blue phase liquid crystals was investigated. It was found that homogeneous alignment layers have profound selective influence on blue phase II (BPII). In the absence of alignment layers, BPII domains were randomly oriented and showed weak Bragg reflection in the UV, whereas with assistance of anchoring uniform domains with sharp Bragg reflection in the visible range appeared. On the other hand, the magnitude of Bragg shift in response to alignment layers in BPI is negligible. Domains of BP with alignment layers exhibit sharp Bragg reflection peaks (with FWHM < 15 nm), with very vivid colors and possessing fast switching speeds (<5 ×10−4 s). This simple method of selectively assisting one of the cubic phases is expected to be advantageous in the comparative studies of the two phases.

Effect of Alignment Layer on Electro-Optic Properties of Polymer-Dispersed Liquid Crystal Displays

The electro-optic properties of polymer-dispersed liquid crystal (PDLC) cell having parallel alignment layers were examined and compared to the control cell without any pre-treatment. Although the liquid crystal droplets of the treated PDLC was observed to be much smaller than that of the control cell, the contrast ratio of both cells are quite similar over a wide temperature range. The control cell performed better in terms of response time and operating voltage. The retardation characteristics of the cells showed sharp contrast, which may bring about inconsistent consequence in determining their electro-optic properties.

Effect of Alignment Layers on the Response Time in a Half V-Shaped Ferroelectric Liquid Crystal Cell

In this paper, we have studied the influence of alignment layers on the switching characteristics in various half V-shaped switching ferroelectric liquid crystal (HV-FLC) cells. By comparing various combinations of alignment layers, we found that an HV-FLC cell with oppositely aligned polarization dipoles has the shortest response time. Such a cell not only has a faster switching characteristic but also has better alignment and is easily fabricated by a simple manufacturing procedure.

Effect of alignment layer on V-shaped switching in a chiral smectic liquid crystal

The influence of the alignment layer on V-shaped switching in thin homogeneous cells of a chiral smectic liquid crystal were studied by means of electro-optic and switching current measurements.Severalpolyimides withdifferent chemicalstructures wereusedas thealignment layer in thin homogeneous cells; V-shaped switching was observed with some of them and W-shaped switching with others. It was also shown that the switching current constantly flows during the V-shaped transmittance change. In order to clarify this effect of the alignment layer on V-shaped switching, polyimide films with various polarity and thickness were examined. It is concluded that thick alignment layers assist liquid crystal materials in realizing V-shaped switching, even if the materials are not ideal for this process.

Dynamic Orientation Structures of Layer-Tilted Surface-Stabilized Ferroelectric Liquid Crystal Cells

The dynamic orientation structures of layer-tilted surface-stabilized ferroelectric liquid crystals (FLC) under applied field are analyzed with a non-uniform switching model based on a one-dimensional elastic-continuum free-energy theory in which the elastic-distortion, surface-interaction and electrostatic energies, constant electric-displacement and non-uniform permittivity are taken into account. The effect of alignment layers on the electrostatic potential is also included through appropriate boundary conditions. It is found that there exists a spatially varying depolarization field along the FLC layer, which tends to de-stabilize the bistability of the cell, and has intensity increasing monotonically with the spontaneous polarization density of the FLC medium, but decreasing with smaller thickness and higher conductivity of the alignment layers. Results of the director and electric field distributions along the cell, and the optical transmissions are presented for different material constants, surface-anchoring strengths and applied voltage conditions.