Patterned field induced polymer walls for smectic A bistable flexible displays

Gheorghiu, Nadina; West, John L.; Glushchenko, Anatoliy; Mitrokhin, M. V.

doi:10.1063/1.2218274

Cited by 27 publications

(14 citation statements)

References 12 publications

(11 reference statements)

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“…[12,13] For instance, Kim et al [14] proposed a robust vertically aligned LC cell, where the LC were locked by polymer walls, and the azimuthal anchoring on the surface of the alignment layer was controlled by the polymerisation of a UV curable reactive mesogen monomer. As a result, the defect points were trapped at a single position, resulting in a greatly improved response time.…”

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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Section: Introductionmentioning

confidence: 99%

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

et al. 2015

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“…The main attraction of LC is its externally controllable characteristics, for example, its optical properties can be modulated by applying electric, optical, or magnetic fields [10][11][12]. In addition to displays and photonic devices, basic works on LCs have drawn increasing attention recently, particularly the dynamically controllable movements of particles in LC media or LC droplets in dielectric media by use of DEP mechanisms [13][14][15]. Traditional DEP mechanisms to manipulate LC or non-LC particles require application of an external voltage.…”

Section: Introductionmentioning

confidence: 99%

External-Voltage-Free Dielectrophoresis of Liquid Crystal Droplets

Lin

et al. 2017

Crystals

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This work reports, for the first time, a dielectrophoresis (DEP) effect-induced motion of liquid crystal (LC) droplets in an LC/monomer mixture sample with a poly-(N-vinyl carbazole) PVK-coated substrate without an external voltage. With the UV pre-irradiation of the PVK layer through a binary mask, a laterally non-uniform electric field can be induced between the pre-illuminated regions and the neighboring non-pre-illuminated PVK regions near the borders of the two regions. The phase separation occurs once the temperature is lower than 50 • C and the LC droplets can form in the sample. The pre-formed non-uniform field provides a DEP-like force to manipulate the small LC microdroplets in the pre-illuminated regions to effectively migrate to the adjacent non-pre-illuminated regions. The continuous supply of the LC from the pre-illuminated regions to the adjacent non-pre-illuminated regions significantly increases the diffraction efficiency of the grating sample. This study provides an insight into developing new external-voltage-free DEP-based devices that can be applied on various fields, such as photonics, displays, and biomedicines.

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“…To solve these problems, several types of polymer wall and/or network as supporting structures have been proposed and demonstrated [17][18][19][20][21]. These structures were fabricated using an anisotropic phase separation method from polymer and SmA LC composite systems by applying a patterned electric field or spatially modulated ultraviolet (UV) intensity [22][23][24]. However, these methods require high electric field to initiate the anisotropic phase separation or remain residual polymers in unexposed regions that reduce optical properties and increase the operating voltage of the devices.…”

Section: Introductionmentioning

confidence: 99%

Flexible Bistable Smectic-A Liquid Crystal Device Using Photolithography and Photoinduced Phase Separation

Yang

Guo

Wang

et al. 2012

Advances in Condensed Matter Physics

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A flexible bistable smectic-A liquid crystal (SmA LC) device using pixel-isolated mode was demonstrated, in which SmA LC molecules were isolated in pixels by vertical polymer wall and horizontal polymer layer. The above microstructure was achieved by using ultraviolet (UV) photolithography and photoinduced phase separation. The polymer wall was fabricated by photolithography, and then the SmA LC was encapsulated in pixels between polymer wall through UV-induced phase separation, in which the polymer wall acts as supporting structure from mechanical pressure and maintains the cell gap from bending, and the polymer layer acts as adhesive for tight attachment of two substrates. The results demonstrated that all the intrinsic bistable properties of the SmA LC are preserved, and good electrooptical characteristics such as high contrast ratio and excellent stability of the bistable states were characterized. This kind of SmA bistable flexible display has high potential to be used as electronic paper, smart switchable reflective windows, and so forth.

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Patterned field induced polymer walls for smectic A bistable flexible displays

Cited by 27 publications

References 12 publications

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

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

External-Voltage-Free Dielectrophoresis of Liquid Crystal Droplets

Flexible Bistable Smectic-A Liquid Crystal Device Using Photolithography and Photoinduced Phase Separation

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