Analysis of deformations of flexoelectric homeotropic liquid crystal layers with various anchoring strengths

• Autorzy: Buczkowska M. , Derfel G.
• Języki publikacji: EN

Abstrakty

EN

Deformations of homeotropic layers of nematic liquid crystal possessing flexoelectric properties and subjected to external dc voltage were studied numerically. The influence of the anchoring strengthWwas investigated. The calculations were performed for two types of layers, one with positive dielectric anisotropy and positive sum of flexoelectric coefficients and the other with opposite signs of these parameters. Strongly blocking electrodes were assumed. The threshold voltages for deformations were computed for several anchoring strength values and for low, moderate, and high ion contents. The director distributions were also determined. They were influenced by joined effects of anchoring strength and space charge of ions. For increasing ion contents and increasing anchoring strength, remarkable change of deformation character was noticed. In the case of negative dielectric and flexoelectric parameters, the threshold was nearly proportional to W for low anchoring strength and saturated at some high value of W. In the case of positive dielectric and flexoelectric parameters, the threshold voltage increased strongly with W. In the range of enhanced ion concentrations, the deformation arose in two voltage ranges. The increasing anchoring strength damped the deformations in the whole layer, however, this effect was minor at high ion content.

Słowa kluczowe

EN

flexoelectric nematic; anchoring strength; dc electric field induced deformations

• Wydawca: Stowarzyszenie Elektryków Polskich ; Polska Akademia Nauk ; Wojskowa Akademia Techniczna im. Jarosława Dąbrowskiego
• Czasopismo: Opto-Electronics Review
• Rocznik: 2011
• Tom: Vol. 19, No. 1
• Strony: 56--60
• Opis fizyczny: Bibliogr. 16 poz., wykr.

Twórcy

autor

Buczkowska M.

autor

Derfel G.

• Institute of Physics, Technical University of Łódź, 219 Wólczańska Str., 90-924 Łódź, Poland,

Bibliografia

• [1] R. B. Meyer: Piezoelectric effects in liquid crystals. Phys. Rev. Lett. 22, 918-921, 1969.
• [2] J. C. Jones, E. L. Wood, G. P. Bryan-Brown, and V.C. Hui: Novel configuration of the zenithal bistable nematic liquid crystal device. SID 98 Digest, 858, 1998.
• [3] J. Harden, B. Mbanga, N. Éber, K. Fodor-Csorba, S. Sprunt, J. T. Gleeson, and A. Jákli: Giant flexoelectricity of bent-core nematic liquid crystals. Phys. Rev. Lett. 97, 157802, 2006.
• [4] A. Derzhanski, A. G. Petrov, and M. D. Mitov: One-dimensional dielectric-flexoelectric deformations in nematic layers. J. Phys.-Paris 39, 273, 1978.
• [5] S. Naemura and A. Sawada: Ion generation in liquid crystals under electric field. Mol. Cryst. Liq. Cryst. 346, 155-168, 2000.
• [6] G. Derfel and M. Buczkowska: Flexoelectric deformations of homeotropic nematic layers in the presence of ionic conductivity. Liq. Cryst. 32, 1183-1190, 2005.
• [7] M. Buczkowska and G. Derfel: Influence of ionic transport on deformations of homeotropic nematic layers with positive flexoelectric coefficients. Liq. Cryst. 32, 1285-1293, 2005.
• [8] G. Derfel and M. Buczkowska: Threshold voltage for purely flexoelectric deformations of conducting homeotropic nematic layers. Liq. Cryst. 34, 113-125, 2007.
• [9] M. Buczkowska and G. Derfel: Role of ions mobility in flexoelectric deformations of conducting homeotropic nematic layers. Sci. Bull. Tech. Univ. Lódź, Physics 29, 5-24, 2008.
• [10] A. Rapini and M. Papoular: Distorsion d'une lamelle nématique sous champ magnétique conditions d'ancrage aux parois. J. Phys. Colloq. 30, C4-54-C4-56, 1969. (in French)
• [11] G. Briere, F. Gaspard, and R. Herino: Cinetique de dissociation et relaxation de conduction ionique en phase liquide. J. Chim. Phys. 68, 845, 1971. (in French)
• [12] H. de Vleeschouwer, A. Verschueren, F. Bougriona, R. Van Asselt, E. Alexander, S. Vermael, K. Neyts, and H. Pauwels: Long-term ion transport in nematic liquid crystal dislays. Jpn. J. Appl. Phys. 40, 3272-3276, 2001.
• [13] G. Derfel and A. Lipiński: Charge carrier mobility measurements in nematic liquid crystals. Mol. Cryst. Liq. Cryst. 55, 89-99, 1979.
• [14] M. Y. Jin and J. J. Kim: Low-frequency dielectric relaxations of a nonchiral liquid crystal, 8CB. J. Phys. Condens. Matter 13, 4435-4446, 2001.
• [15] G. Derfel: Numerical study of ionic current in dielectric liquid layer subjected to ac voltage. J. Mol. Liq. 144, 59-64, 2009.
• [16] D. Oliveiro, L. R. Evangelista, and G. Barbero: External electric-field effect on nematic anchoring energy. Phys. Rev. E65, 031721, 2002.