Dynamic behavior of twisted nematic liquid-crystal layers in switched fields

Doorn, C.Z. Van

doi:10.1063/1.322177

Cited by 232 publications

(101 citation statements)

References 24 publications

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“…The temporal variation of the director profile has been resolved with a resolution of 0.2 ms as the cell relaxed from a distorted state at 7 V to an equilibrium state at 0 V. In order to fit the dynamic optical data, a "backflow region" was identified for short time scales, which was predicted by Berreman [3] and van Doorn [4]. In the backflow region, the midplane tilt of the director was found to increase to a maximum value of 101 ± after the voltage had been removed for 1.4 ms.…”

Section: -2mentioning

confidence: 99%

“…This coupling between fluid flow and director alignment has no isotropic counterpart and is described by the Leslie-Erickson [1,2] hydrodynamic continuum theory of nematic liquid crystals. Numerical methods for solving Leslie-Erickson equations of motion have been used to study the switching dynamics of a 90 ± twisted nematic (TN) cell [3,4]. This modeling work showed that upon removal of a suitably large externally applied field a temporary reverse of the twist direction occurs during the first few ms.…”

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confidence: 99%

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Direct Optical Quantification of Backflow in a90°Twisted Nematic Cell

2002

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Optical guided mode observations of the transient director profile (optical tensor distribution) during the relaxation of a 90 ± twisted nematic cell directly reveals backflow. In the first 6 ms of the relaxation process, after a voltage across the cell is removed, the midplane tilt of the director increases, reaching a maximum value of 101 ± at 1.4 ms. This increase in midplane tilt is attributed to coupling between fluid flow (backflow) and director reorientation. A 270 ± twisted state of the opposite handedness to the 90 ± twisted state found at equilibrium is shown to exist during the backflow period. Good fits of theoretical models with experimentally determined time dependent director profiles yield the viscosity coefficients.

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Section: -2mentioning

confidence: 99%

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confidence: 99%

Direct Optical Quantification of Backflow in a90°Twisted Nematic Cell

2002

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“…The three elastic constants k 11 , k 22 , and k 33 are called the splay, twist, and bend constants, respectively (8) (9) . On the other hand, the energy density f elec that the liquid crystal receives from electric field is given by…”

Section: Self-consistent Analysis Of Liquid-crystal Orientation and Ementioning

confidence: 99%

Analysis of Light Leakage in Liquid-Crystal Devices with In-Plane Switching Electrodes

et al. 2004

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To realize wider viewing angle for a liquid-crystal display (LCD), particular attention is being paid to the in-plane switching (IPS) mode of LCD, where pixel electrodes and common (opposite) electrodes are arranged on the same array substrate and liquid crystal is made respond by an electric field generated in parallel to the substrate. So far, two types of array electrode structures are proposed in IPS-LCD. One is the array structure with two electrode layers where pixel electrodes and common electrodes are formed on different conductive layers. In the other array structure they are formed on one conductive layer. Although both electrode structures of IPS-LCD have problems dependent on the process conditions, light leakage observed only in the former structure along the edge of the common electrodes at zero bias is an essentially serious problem. By studying light wave propagation in the IPS-LCD using a two-dimensional finite-difference timedomain method we have found that the light leakage is caused by the tapered side surfaces of the common electrodes.

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“…The dynamic data were analyzed by using a modeling program (DIMOS) based on the Ericksen-Leslie hydrodynamic theory [1][2][3] using the approximation of Berreman and van Doorn [4,5]. This means that in this modeling the fluid inertia is ignored and flow is restricted to the plane of the cell.…”

Section: P H Y S I C a L R E V I E W L E T T E R Smentioning

confidence: 99%

“…Their switching dynamics, key to their functionality as video displays, is understood in terms of the foundational theory pioneered by Ericksen [1,2] and Leslie [3]. Developed in the 1960s, and simplified by Berreman and van Doorn [4,5], this theory of flow in anisotropic fluids is still very widely used. However, there exist very few detailed experimental confirmations of many of its predictions.…”

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confidence: 99%

Flow-Induced Twist-Compression in a Twisted Nematic Cell

Ruan

Sambles

2003

Phys. Rev. Lett.

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An optical convergent-beam guided-wave technique is used to explore in detail the dynamic flow effects in a twisted nematic cell. During switch-on it is found that the dynamic flow compresses the director twist to regions close to the cell walls. For high fields this twist compression takes the cell far beyond the Mauguin limit and it no longer effectively guides the polarization of the light through the cell. This results in a very fast switch to a transient dark state. DOI: 10.1103/PhysRevLett.90.168701 PACS numbers: 83.80.Xz, 47.17.+e, 42.79.Gn, 78.20.-e Nematic liquid crystals form the basis of the majority of flat screen displays. Their switching dynamics, key to their functionality as video displays, is understood in terms of the foundational theory pioneered by Ericksen [1,2] and Leslie [3]. Developed in the 1960s, and simplified by Berreman and van Doorn [4,5], this theory of flow in anisotropic fluids is still very widely used. However, there exist very few detailed experimental confirmations of many of its predictions. This is particularly true as regards to switch-on dynamics where the influence of flow in a relatively fast, field-driven process has barely been explored. Some simple experiments [6,7] have confirmed the theoretically predicted ''backflow'' in a twisted nematic (TN) cell during switch-off by recording an optical ''bounce'' effect in transmission. However, almost all the experiments [8] are based on simple transmission or reflection observations during switching and as such the signals from the liquid crystal cell are an integrated response. Only recently, using a convergentbeam optical guided-wave technique [9,10], have details of the director profile in the liquid crystal cell during switch-off been unambiguously obtained, thereby establishing the validity of the theory. Further there has been no published work which details the change of director profile within a cell during switch-on, a much faster process providing a more rigorous test of the theory.In this present study a convergent-beam system is used to investigate the switch-on dynamics of a twisted nematic cell detailing directly the strong influence of flow on the twist profile, and, in particular, the strong compression of director twist to the cell walls.The liquid crystal cell comprises two low index glass plates (n 1:5170 at 632.8 nm), each coated inside by a thin ( 50 nm) layer of indium tin oxide (ITO), on top of which are surface aligning layers of rubbed polyimide. The plates are assembled together with 6:0 m spacers in between. A twisted director profile is established by setting the angle between the rubbing directions of the upper and lower plates to about 87 . The cell is filled with liquid crystal ZLI-2293 (Merck) in the isotropic phase and then slowly cooled down to room temperature forming a monodomain.The cell is then inserted between the two glass hemispheres, optical contact being achieved with matching fluid. The glass hemispheres and the matching fluid have the same index as the glass substrates of the ...

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Dynamic behavior of twisted nematic liquid-crystal layers in switched fields

Cited by 232 publications

References 24 publications

Direct Optical Quantification of Backflow in a90°Twisted Nematic Cell

Direct Optical Quantification of Backflow in a90°Twisted Nematic Cell

Analysis of Light Leakage in Liquid-Crystal Devices with In-Plane Switching Electrodes

Flow-Induced Twist-Compression in a Twisted Nematic Cell

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