Continuous liquid crystal pretilt control through textured substrates

Lee, Fuk Kay; Zhang, Baoshe; Sheng, Ping; Kwok, Hoi Sing; Tsui, Ophelia Kwan Chui

doi:10.1063/1.1833552

Cited by 39 publications

(18 citation statements)

References 9 publications

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“…Kim et al [18][19][20] presented a general approach to establishing in-plane alignment bistability by exploiting the orientational frustration induced by a checkerboard pattern. Lee et al [21] subsequently demonstrated a continuous variation in LC pretilt using a checkerboard pattern comprising regions with orthogonally etched grooves. Bechtold and Oliveira [22] experimentally investigated the equilibrium configuration of the director for a submicron patterned substrate, creating alternating homeotropic and random planar stripes by selectively irradiating a SAM with deep UV.…”

Section: Introductionmentioning

confidence: 99%

Nematic liquid crystal alignment on chemical patterns

et al. 2007

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Patterned Self-Assembled Monolayers (SAMs) promoting both homeotropic and planar degenerate alignment of 6CB and 9CB in their nematic phase, were created using microcontact printing of functionalised organothiols on gold films. The effects of a range of different pattern geometries and sizes were investigated, including stripes, circles and checkerboards. Evanescent Wave Ellipsometry was used to study the orientation of the liquid crystal (LC) on these patterned surfaces during the isotropic-nematic phase transition. Pretransitional growth of a homeotropic layer was observed on 1 µm homeotropic aligning stripes, followed by a homeotropic mono-domain state prior to the bulk phase transition. Accompanying Monte-Carlo simulations of LCs aligned on nano-patterned surfaces were also performed. These simulations also showed the presence of the homeotropic mono-domain state prior to the transition. * Electronic address: s.d.evans@leeds.ac.uk

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Section: Introductionmentioning

confidence: 99%

Nematic liquid crystal alignment on chemical patterns

et al. 2007

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“…In contrast, topographically or chemically patterned surfaces permit essentially arbitrary control of the easy axis and anchoring potential through appropriate adjustment of the pattern features [1]; suitable patterning techniques include atomic force microscope scribing of polymer films [2,3], microcontact printing of self-assembled monolayers (SAMs) [4][5][6], and photolithography [7][8][9][10]. By imprinting a design of appropriate symmetry, it is also possible to pattern a surface to promote more than one stable alignment orientation [2,[11][12][13][14] thus enabling the fabrication of bistable devices [2,10,[15][16][17][18].…”

Section: Introductionmentioning

confidence: 99%

Independent control of polar and azimuthal anchoring

et al. 2013

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Monte Carlo simulation, experiment, and continuum theory are used to examine the anchoring exhibited by a nematic liquid crystal at a patterned substrate comprising a periodic array of rectangles that, respectively, promote vertical and planar alignment. It is shown that the easy axis and effective anchoring energy promoted by such surfaces can be readily controlled by adjusting the design of the pattern. The calculations reveal rich behavior: for strong anchoring, as exhibited by the simulated system, for rectangle ratios 2 the nematic aligns in the direction of the long edge of the rectangles, the azimuthal anchoring coefficient changing with pattern shape. In weak anchoring scenarios, however, including our experimental systems, preferential anchoring is degenerate between the two rectangle diagonals. Bistability between diagonally aligned and edge-aligned arrangement is predicted for intermediate combinations of anchoring coefficient and system length scale.

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“…The method to increase the pretilt angle for the surface patterning process for LC alignment is divided into two aspects, the groove-shape design [21,40] and the formation of physically or chemically inhomogeneous textures. [17,41,42] However, because the groove-shape design and physically inhomogeneous texture are difficult to apply to nanometer-scale structures with better optical performance and it is difficult to know the exact LC transition direction, the chemically inhomogeneous texture is the appropriate method to increase the pretilt angle and ensure a fixed LC direction and good optical properties. Therefore, we will now proceed to investigate the increase of the pretilt angle by the formation of the chemically inhomogeneous texture and this will be described in future reports.…”

Section: Lc Alignment and Pretilt Formationmentioning

confidence: 99%

The Directional Peeling Effect of Nanostructured Rigiflex Molds on Liquid‐Crystal Devices: Liquid‐Crystal Alignment and Optical Properties

Kim

Lim

Park

et al. 2008

Adv Funct Materials

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We report a new strategy, the directional peeling of a rigiflex mold with a nanostructure, to overcome several problems with general patterning techniques for liquid‐crystal (LC) alignment. These include difficulty in generating the pretilt angle and in controlling the LC rising‐up direction, formation of local domains, and weak optical properties. The directional peeling of the rigiflex mold results in pretilt‐angle formation and controls the LC rising‐up direction. In addition, a nanostructure with small spacing aligns the LC with a high order parameter because of a strong confinement effect and suppresses diffraction due to its small spacing. Eventually, the nanostructure achieves improvements in the optical properties. In summary, while recent patterning techniques for LC alignment only solve one problem, the directional peeling of the rigiflex mold with a nanostructure simultaneously overcomes several problems with LC alignment and optical properties.

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Continuous liquid crystal pretilt control through textured substrates

Cited by 39 publications

References 9 publications

Nematic liquid crystal alignment on chemical patterns

Nematic liquid crystal alignment on chemical patterns

Independent control of polar and azimuthal anchoring

The Directional Peeling Effect of Nanostructured Rigiflex Molds on Liquid‐Crystal Devices: Liquid‐Crystal Alignment and Optical Properties

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