Improvement of voltage-dependent dynamics through an oblique electric field in vertically aligned liquid crystal director surrounded by patterned polymer walls

Kim, Sang Gyun; Kim, Youn Sik; Srivastava, Anoop Kumar; Oh, Seung-Jin; Lee, Gi Dong; Lee, Seung Hee

doi:10.1016/j.cap.2007.06.004

Cited by 8 publications

(3 citation statements)

References 7 publications

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“…In the conventional LSH cell in which the LC orientation in the on state is defined only by the polymer walls surrounding the LCs, when V > V th , collision of the LCs occurs as a result of the undefined azimuthal direction of the surface pretilt angle in the initial state, which instantaneously generates an undefined LC texture. Nevertheless, with time, it reaches a stable final state with a radial configuration of the mid-director due to chiral dopant with a defect point at the centre of each room [11,14]. The orientation of the polymerized reactive mesogen at the surfaces follows the LC orientation because UV is irradiated at this stage when the orientation of the LCs has a defined pretilt angle with axially symmetric alignment in azimuth, as shown in figure 2.…”

Section: Experimental Conditions and Formation Of Surface Pretilt Anglementioning

confidence: 99%

“…This phenomenon is particularly undesirable with touch panel LCDs. Another type of VA was suggested to suppress ripples, known as a locked-super homeotropic (LSH) cell, where the LC is surrounded by polymer walls [11][12][13][14]. In all VA modes, the vertically aligned LCs at the initial state are deformed in different directions in the presence of an electric field to generate the same phase difference according to the viewing angle in order to show wide viewing angle.…”

Section: Introductionmentioning

confidence: 99%

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Trapping of defect point to improve response time via controlled azimuthal anchoring in a vertically aligned liquid crystal cell with polymer wall

Kim¹,

Kim²,

Kim³

et al. 2008

J. Phys. D: Appl. Phys.

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Conventional multi-domain vertically aligned liquid crystal (LC) cells have defect points due to the collision of LC directors during the formation of multiple domains. In addition, the location of defects changes with time resulting in a slow response time. This paper proposes a robust vertically aligned LC cell, where the LCs are locked by polymer walls, and the azimuthal anchoring on the surface of the alignment layer is controlled by the polymerization of a UV curable reactive mesogen monomer. As a result, the defect points are trapped at a single position, resulting in a greatly improved response time.

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Section: Experimental Conditions and Formation Of Surface Pretilt Anglementioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Trapping of defect point to improve response time via controlled azimuthal anchoring in a vertically aligned liquid crystal cell with polymer wall

Kim¹,

Kim²,

Kim³

et al. 2008

J. Phys. D: Appl. Phys.

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show abstract

“…As a result, the defect points were trapped at a single position, resulting in a greatly improved response time. Kim et al [15] proposed advanced cell structure where the bend and twist deformation was controlled by polymer wall plus an oblique electric field through patterned electrode. The device shows wide viewing angle characteristics with advantages that it is free from rubbing process and spacer.…”

Section: Introductionmentioning

confidence: 99%

Reverse-mode polymer dispersed liquid crystal films prepared by patterned polymer walls

et al. 2015

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This article proposes a methodology to prepare polymer dispersed liquid crystal (PDLC) films working in the reverse-mode operation, where the ion-doped nematic liquid crystals (NLCs) with negative dielectric anisotropy (Δε) were locked by polymer walls. On-state and off-state of films were controlled by an electric field. In the absence of an electric field, it appears to be transparent. In the field, the homogeneous alignment NLCs form dynamic scattering, giving rise to opaque. The effect of the cylindrical holes with different diameters of photo masks and liquid crystal Δε on the electro-optical properties and transmittance wavelength range of 400-3000 nm light of samples were investigated. It was found that it exhibited very good electro-optical characteristics, high contrast ratio and excellent infrared energy-efficient of films used as switchable windows.Keywords: reverse-mode polymer dispersed liquid crystal; polymer walls; nematic liquid crystal; negative dielectric anisotropy; electro-optical properties IntroductionPolymer dispersed liquid crystal (PDLC) films are technologically important class of materials that find numerous applications as electrically switchable optical devices.[1-3] PDLC films are formed by liquid crystal (LC) microdroplets embedded in a polymer matrix. They can exhibit either a droplet morphology in which droplets of LC are embedded in a polymer matrix, or a polymer ball morphology in which the LC takes up the voids and the crevices of a network structure formed by small polymer balls. In the normal-mode operation, they are in an opaque state (offstate) and can be turned into a transparent state (onstate) by controlling the LC molecule orientation by means of a suitable voltage. The reverse-mode PDLC films are transparent in its off-state and can be turned into an opaque on-state. A greater interest has been aroused by reverse-mode PDLC films that are useful as switchable windows, automotive applications [4,5] and used in a wide range of applications that need a transparent state in the absence of any applied voltage.Several authors have reported examples of reverse-mode PDLC films obtained by modification of the polymer surface energy,[6] by functionalising the LC/polymer matrix interface,[7] by using dualfrequency addressable LC,[8] by means of rough surfaces [9,10] or by increasing the LC content. [11]

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Synthesis and electrochemical properties of azo and anthraquinone derivatives

Jung

Park

2010

Current Applied Physics

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Improvement of voltage-dependent dynamics through an oblique electric field in vertically aligned liquid crystal director surrounded by patterned polymer walls

Cited by 8 publications

References 7 publications

Trapping of defect point to improve response time via controlled azimuthal anchoring in a vertically aligned liquid crystal cell with polymer wall

Trapping of defect point to improve response time via controlled azimuthal anchoring in a vertically aligned liquid crystal cell with polymer wall

Reverse-mode polymer dispersed liquid crystal films prepared by patterned polymer walls

Synthesis and electrochemical properties of azo and anthraquinone derivatives

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