Control of an Easy-Axis on Nematic-Polymer Interface by Light Action to Nematic Bulk

Voloshchenko, Dmitry A.; Khyzhnyak, Anatolii; Reznikov, Yuriy; Reshetnyak, Victor

doi:10.1143/jjap.34.566

Cited by 121 publications

(70 citation statements)

References 7 publications

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“…An interpretation involving adsorption of the MR on the surfaces, parallel to the polarization, and subsequent reorientation of the liquid crystal, seems to be the most likely mechanism [4]. The large index grating observed here is caused by a reorientation of the director of dh 8°after 2500 s. We suggest that the absorption grating originates from the microassembly of dye molecules on the surface [14].…”

Section: Gratings Written With High Intensitiesmentioning

confidence: 57%

“…MR is an azo-dye and under the action of light, it photoisomerizes from the trans to the cis form [9]. The spectra show the absorption band of the MR in the trans form [4]. The sample is dichroic, indicating that the MR are roughly aligned along the director, perpendicular to the surfaces.…”

Section: Dichroismmentioning

confidence: 99%

“…We also exclude a photoadsorption eect [4]. The grating would be permanent, and the index grating accompanied by an adsorption grating.…”

Section: Gratings Written With Low Intensitiesmentioning

confidence: 99%

“…Their strong birefringence is used to generate modulation of refractive index by molecular reorientation, with an electric ®eld, or under the action of light. In dye-doped nematics, dierent phenomena may cause reorientation induced by polarized light: the torque induced by the anisotropy of the optical permittivity, and enhanced by some dopants [2]; photoisomerization and reorientation of the azodyes followed by the reorientation of the liquid crystal [3]; photoadsorption of the azo-dyes onto the surface of the sample, changing the anchoring conditions [4]; photorefractive-like eect [5].…”

Section: Introductionmentioning

confidence: 99%

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Analysis of gratings induced in azo-dye doped liquid crystals

et al. 2001

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We investigate the formation of photoinduced gratings in a homeotropic ®lm of nematic liquid crystal doped with methyl red. Using a grating translation technique, we determine the time evolution of the amplitudes and phase shifts of both index and absorption modulations. With low writing intensities, a fast grating caused by photoisomerization of the dye competes with a slower grating, originating from a reorientation of the director. This slower grating only appears if the light polarization has a nonzero projection on the director, i.e. at oblique incidence. The grating decays in the dark. We suggest that its formation may be explained by a light-induced dielectric torque, rather than a photorefractive eect. With high intensities, an even slower grating is formed at normal incidence. We stipulate that it originates from a change in the anchoring parameters caused by the adsorption of photoisomerized dyes on the surfaces. The resulting reorientation of the director is permanent. Ó

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Section: Gratings Written With High Intensitiesmentioning

confidence: 57%

Section: Dichroismmentioning

confidence: 99%

“…We also exclude a photoadsorption eect [4]. The grating would be permanent, and the index grating accompanied by an adsorption grating.…”

Section: Gratings Written With Low Intensitiesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Analysis of gratings induced in azo-dye doped liquid crystals

et al. 2001

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“…Voloschenko et al [36] were the first to identify the adsorption effect in homogeneously aligned azo-dye doped LC films. They found that the absorption band of methyl red (MR) resulted in the photoalignment of LC on an isotropic surface of a polyninylcinnamate (PVCN) film, as depicted in Fig.…”

Section: Bulk-mediated Photo-isomerization and Adsorption Effectsmentioning

confidence: 99%

Photo-Alignment Technology

Lin

2014

Topics in Applied Physics

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LCDs are used in many everyday devices, including mobile phones, notebook computers and wide screen televisions. A typical LCD is composed of two glass substrates between which is a gap that is filled with LC. The arrangement of the LC is controlled by the boundary condition of an alignment film. A long-range orientational interaction causes the preferable alignment of a LC by the surface boundary to extend into the LC bulk. The alignment layer is typically rubbed with a special cloth to induce a unidirectional alignment of the LC. In the first devices based on twisted LCs, these LCs were aligned only by rubbing transparent electrodes. The rubbing technique became much more reliable when the glass substrate was covered with a rubbed polymer layer. The rubbing of polymers is a very simple technique and it is now extensively utilized in both small scientific laboratories and large LCD factories.Despite the extensive use of rubbing in LCD manufacturing, it has some serious shortcomings that arise from the contact involved in rubbing. These critically affect the production of the most recent generation of LCDs and miniature LC photonic devices. First, rotational rubbing for the polymer surface causes the accumulation of static charges and the formation of fine dust particles. The accumulation of static electricity may destroy the transistors or diodes in the LCD. The second shortcoming is the effect of decreasing in manufacturing yield. Rubbing for large and high-resolution active matrix LCDs (AMLCDs) involve additional difficulties that are associated with the precise control of the rubbing characteristics. Other problems are the difficulty of producing local structures with the required LC director alignment in the selected areas of the device. Finally, this method cannot be used to align LCs in closed volumes.For all of the above reasons, new alignment solutions and approaches are sought. There are some alternative methods of rubbing include laser writing, micro-rubbing, ion beam irradiation and photoalignment. Of these methods, the

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Alignment Photoregulation of a Nematic Liquid Crystal by Surface Adsorption of Aminoalkylated Azobenzenes

Ueda

Kudo

Ichimura

1996

Israel Journal of Chemistry

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Adsorption behavior of azobenzenes having an aminoalkyl residue onto a silica surface is described. Immersion of a silica plate in a benzene solution of an aminoalkylated azobenzene resulted in efficient adsorption to form face‐to‐face aggregates which are converted into monomeric states by partial desorption. Silica plates adsorbing the azobenzene bearing an aminoalkyl residue were employed to achieve the surface‐assisted photoregulation of alignment of a nematic liquid crystal between homeotropic and planar modes. Based on these observations, a convenient method to prepare command surfaces for the orientational photoregulation of liquid crystals was presented by filling a liquid crystal containing an aminoalkylated azobenzene into an empty cell composed of clear silica plates.

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Control of an Easy-Axis on Nematic-Polymer Interface by Light Action to Nematic Bulk

Cited by 121 publications

References 7 publications

Analysis of gratings induced in azo-dye doped liquid crystals

Analysis of gratings induced in azo-dye doped liquid crystals

Photo-Alignment Technology

Alignment Photoregulation of a Nematic Liquid Crystal by Surface Adsorption of Aminoalkylated Azobenzenes

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