Dependence of threshold behavior upon surface distribution of polymer chains in a twisted nematic liquid crystal

Gwag, Jin Seog; Lee, Gi‐Dong; Yoon, Tae–Hoon; Kim, Jae Chang

doi:10.1103/physreve.69.062702

Cited by 4 publications

(1 citation statement)

References 20 publications

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“…Sugimura et al 6 have introduced a unified surface anchoring energy and have pointed out that commonly assumed separation of Rapini-Papoular (RP) 7 energy into polar and azimuthal parts is not physically justified. Quite recently, Gwag et al 8 have proposed an interesting theoretical approach to this topic. In experimental studies (Gwag et al 9 ) it was assumed that the anisotropy distribution of polyimide (PI) chains induced by the rubbing strength is dominated by a gaussian distribution around the rubbing direction.…”

Section: Introductionmentioning

confidence: 99%

Monte Carlo modeling of optical properties of twisted NLC systems: role of anchoring forces

Pawlik

Mituś

Kajzar³

2006

SPIE Proceedings

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Statistical mechanics of an inhomogeneous NLC molecular alignment in NLC cells with complicated intermolecular and molecule-wall (anchoring) interactions can be easily studied using Metropolis Monte Carlo simulation method for Lebwohl-Lasher lattice system. 1 Those studies have elucidated some microscopic aspects of the role of anchoring forces for local and global molecular ordering, leading to novel features in the external electric field (E) -anchoring strength (α) phase diagram for refractive index or an unexpected maximum of diffraction efficiency for low values of anchoring strength α in planar NLC cells. 2 Quite recently, this approach was used for a study of transmission of light through a twisted NLC cell as a function of applied voltage and light wavelength, for some values of α. 3 First results show interesting generalizations of known analytical results of Yeh and Gu. 4 In this paper we address a question of the importance of fluctuations of local rubbing directions and of fluctuations of anchoring strength for optical properties of NLC based optical systems. Preliminary results for chosen systems are presented.

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Section: Introductionmentioning

confidence: 99%

Monte Carlo modeling of optical properties of twisted NLC systems: role of anchoring forces

Pawlik

Mituś

Kajzar³

2006

SPIE Proceedings

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Reverse tilt domains in liquid crystal cells with a splayed director configuration

Lee

Yoon

Kim

et al. 2006

Journal of Applied Physics

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When an electric field is applied to a nematic liquid crystal cell with splay alignment layers, which is realized by mechanical parallel rubbing, the system exhibits abnormal reverse tilt domains. Even though the system has pretilt angle due to symmetry breaking by rubbing, existence of singular point in a cell by splay geometry and shift of that by locally asymmetric pretilt angle configurations result in the abnormal reverse tilt domains. On the basis of Oseen-Frank theory, dependence of singular point upon the abnormal reverse tilt domains is theoretically investigated for a splay alignment liquid crystal cell. By using the Dickman's Q-tensor method ͓SID Int. Symp. Digest Tech. Papers 24, 638 ͑1993͔͒, liquid crystal director field is calculated for the splay-aligned liquid crystal cell that an electric field is applied to. We presume a model to explain the abnormal reverse tilt domains, and derive the conditions required for the generation and elimination of these domains.

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Effect of polyimide layer surfaces on pretilt angles and polar anchoring energy of liquid crystals

Gwag

Kim

Yoon

et al. 2006

Journal of Applied Physics

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Considering the surface distribution of polyimide chains, the properties of the unidirectional out-of-plane nematic liquid crystal tilt angle are investigated in view of the van der Waals interaction between nematic liquid crystal molecules and two polyimide layers: the anisotropic upper layer and the isotropic lower layer. The dependence of the pretilt angle upon the thickness of the upper polyimide layer oriented by rubbing is estimated from experiment and theory. Another experimental result shows that the relation between the anchoring energy and the thickness of the polyimide layer could be dependent on lower material. This was also explained in view of the nonretarded van der Waals interaction.

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Dependence of threshold behavior upon surface distribution of polymer chains in a twisted nematic liquid crystal

Cited by 4 publications

References 20 publications

Monte Carlo modeling of optical properties of twisted NLC systems: role of anchoring forces

Monte Carlo modeling of optical properties of twisted NLC systems: role of anchoring forces

Reverse tilt domains in liquid crystal cells with a splayed director configuration

Effect of polyimide layer surfaces on pretilt angles and polar anchoring energy of liquid crystals

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