Peculiarity of an Oblique Liquid Crystal Alignment Induced by a Photosensitive Orientant

Dyaduysha, Andrey; Khizhnyak, A. I.; Marusii, Tatyana; Reshetnyak, Victor; Reznikov, Yuriy; Park, Woo-Sang

doi:10.1143/jjap.34.l1000

Cited by 30 publications

(11 citation statements)

References 5 publications

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“…In particular, optical methods appear more attractive with respect to the rubbing technique since light can be focused and used to develop microstructures where the LC director orientation varies at high spatial resolution, as required for construction of complex electro-optic devices. The surface-mediated LC photoalignment has been demonstrated in the literature using molecular layers (or polymeric film) containing different photoreactive groups: azoaromatics [2][3][4][5], cinnamates [6,7], and coumarins [8].…”

Section: Introductionmentioning

confidence: 99%

Azo-Containing Polymer Brushes: Photoalignment and Application as Command Surfaces

Camorani

Cristofolini

Fontana

et al. 2009

Molecular Crystals and Liquid Crystals

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A brush polymer containing photosensitive mesogenic side chains has been directly synthesized on glass substrates by a grafting method involving polymerization of a metacrylic azobenzenic monomer under Atomic Transfer Radical Polymerization (ATRP) conditions. Brush polymer surfaces, with respect to more traditional films, are resistant to solvents and to high temperatures due to the covalent bonds between chain and substrate, which stabilizes the film morphology. The peculiar characteristics of the present polymeric brushes, namely the intrinsic in-plane orientation of the mesogenic units located in the side chains, together with the possibility of a fine control on the structure, make them very attractive for application as command surfaces.We then employed such brushes as photo-controllable command surfaces in twisted=planar switchable cells filled with a low molecular weight liquid crystal and we characterized the molecular order at interface by means of confocal polarized Raman microscopy.

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Section: Introductionmentioning

confidence: 99%

Azo-Containing Polymer Brushes: Photoalignment and Application as Command Surfaces

Camorani

Cristofolini

Fontana

et al. 2009

Molecular Crystals and Liquid Crystals

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“…Therefore, new LC alignment techniques without rubbing procedure have been investigated and developed. Among the various optical LC alignment techniques, a modified surface with photo-isomerizable molecules (so-called Command Surface), [1] photo-reactive polymers such as poly(vinyl cinnamate), [2,3] and an anisotropic photo-degradation of polymer surface [4] are well known. Besides the optical alignment technique, it is well known that nematic liquid crystalline molecules are aligned well on the film with surface relief parallel to the direction of grooves, [5] thus this can also be applicable for the LC alignment.…”

Section: Introductionmentioning

confidence: 99%

UV‐Curable Azobenzene Polymer Bearing Photo‐Crosslinkable Moiety for Stabilization of Photo‐Fabricated Surface Relief Structure

Kimura

Kim²,

Fukuda

et al. 2002

Macro Chemistry & Physics

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In order to find a new class of photo‐processable liquid crystalline (LC) aligning material, five kinds of new maleimide‐based copolymers bearing both azobenzene and cinnamate moieties with different functionalization ratio have been synthesized. The properties of these five copolymers were compared regarding physical and chemical properties that are required for our aim. The photo‐induced surface relief (PSR) gratings could be fabricated on the films of these copolymers using an Ar+ laser (λ = 488 nm), and were successfully immobilized and bleached by UV‐light irradiation that causes photo‐crosslinking of the cinnamate moiety and photo‐degradation of the azobenzene moiety, respectively. The PSR inscription rate and the thermal stability have been investigated regarding the functionalization ratio between cinnamate and azobenzene side chain. The residual ratio of the PSR structure after UV‐curing was increased with increasing photo‐crosslinkable moiety. It was confirmed that the UV‐cured PSR grating structure becomes transparent at visible wavelength and was able to align LC molecules parallel to the grating direction.

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“…Among alternative processing techniques [3][4][5][6][7][8][9][10][11][12][13][14] it has been shown that photosensitive polymer films align LC molecules homogeneously when exposed to linearly polarized ͑near͒-UV ͑LPUV͒ light. Some of the processes studied were: dimerization-based systems such as derivatives of polyvinylcinnamate, [8][9][10] isomerization-based systems such as polymer films doped with photoisomerizable azobenzene molecules, [11][12][13] and the decomposition of polymer chains. 14 The photoalignment method offers advantages in applications to LC displays ͑LCDs͒, particularly in fabricating high-resolution multidomain LC devices.…”

Section: Introductionmentioning

confidence: 99%

“…For this purpose, several photoalignment techniques have been proposed such as combining double exposure and oblique irradiation of LPUV light techniques. 10 Recently, a new method using unpolarized ͑near͒-UV ͑UPUV͒ light has been developed for the decomposition of polymer chains. 14 This technique is of great advantage for aligning large phototreated areas, since it does not require a polarizer.…”

Section: Introductionmentioning

confidence: 99%

Director tilting of liquid crystals on photoisomerizable polyimide alignment layers doped with homeotropic surfactant

Park

Han

Jung

et al. 1999

Journal of Applied Physics

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Director tilting of liquid crystal (LC) molecules on photosensitive alignment layers has been investigated. The layers, polyimides with photoisomerizable groups in their main chains, were irradiated with unpolarized near-UV (UPUV) light at oblique incidence. The irradiated film was found to align LC molecules homogeneously with a negligible pretilt angle. It was found that the pretilt angle can be generated successfully by introducing surfactant lecithin and decreasing the incidence angle of the UPUV light. The LC alignment and electro-optical properties of the LC cells with the photoalignment layers were demonstrated to be suitable for twisted nematic LC, vertical alignment LC, and surface-stabilized ferroelectric LC devices.

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Peculiarity of an Oblique Liquid Crystal Alignment Induced by a Photosensitive Orientant

Cited by 30 publications

References 5 publications

Azo-Containing Polymer Brushes: Photoalignment and Application as Command Surfaces

Azo-Containing Polymer Brushes: Photoalignment and Application as Command Surfaces

UV‐Curable Azobenzene Polymer Bearing Photo‐Crosslinkable Moiety for Stabilization of Photo‐Fabricated Surface Relief Structure

Director tilting of liquid crystals on photoisomerizable polyimide alignment layers doped with homeotropic surfactant

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