Jpn. J. Appl. Phys. 46 (2007) pp. 1617-1619  |Previous Article| |Next Article|  |Table of Contents|
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Brief Communication

Dielectric and Flexoelectric Responses of Nematic Liquid Crystals on Circularly Orientating Patterns

Jong-Hyun Kim1,2 and Hiroshi Yokoyama2,3

1Physics and Institute of Quantum Systems, Chungnam National University, 220 Gung-dong, Yuseong-gu, Daejeon 305-764, Korea
2Yokoyama Nano-Structured Liquid Crystal Project, JST, Tsukuba, Ibaraki 300-2635, Japan
3Nanotechnology Research Institute, AIST, 1-1-4 Umezono, Tsukuba, Ibaraki 305-8568, Japan

(Received November 29, 2006; accepted December 25, 2006; published online April 5, 2007)

We fabricated circularly orientating alignment patterns, in which nematic liquid crystals align concentrically, on the uniformly rubbed layer. Texture indicated disclination perpendicularly to the rubbing for radial alignment and parallel for tangential. Shape and direction of the disclination were changed by the strength and frequency of in-plane electric field. The change was proportional to the strength. The response up to several tens Hz was asymmetric to the electric polarity. Above this frequency, the response was symmetric and only strength dependent. We attribute the asymmetric response to both flexoelectric and dielectric effect, and symmetric response to the dielectric effect alone.

DOI: 10.1143/JJAP.46.1617
KEYWORDS:nematic liquid crystal, nano-rubbing, flexoelectric effect, circular orientation pattern, alignment

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References | Citing Articles (2)

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  9. The director of the twist disclination is expressed as φ= ϕ/2. ϕ is the angle around the disclination. The dielectric response of the director to the electric field is proportional to sin (φ- φE)2. φE is the direction of the electric field. If we add all the contributions of the director around the disclination, the dielectric response becomes independent on the direction of the disclination.
  10. Assume that the disclination is along the y direction and the director around the disclination is φ= 1/2 tan -1(z/x) = ϕ/2. Then director is expressed by n(φ) = (sin φ, cos φ,0). The flexoelectric polarization for a given point is p = sin ϕ/2r((e1 - e3)/2 sin ϕ, -e1sin 2(ϕ/2)-e3cos 2(ϕ/2), 0). Adding up all the contributions around the disclination, it results in ptot = π/4 a(e1-e3, 0, 0). Here a is a parameter which indicates the effective range of the disclination. The polarization is practically perpendicular to the disclination.

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