Nematic homogeneous photo alignment by polyimide exposure to linearly polarized uv.

Hasegawa, Masaki; Taira, Yoichi

doi:10.2494/photopolymer.8.241

Cited by 193 publications

(122 citation statements)

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“…To elucidate a basic concept of photodegradation effect, we would like to revisit original works of literature. Hasegawa and Taira [30] first reported that a PI film exposed to linearly polarized ultraviolet (LPUV) light induces a uniform parallel (homogeneous) alignment of LC molecules. The average molecular orientation of the LC molecules is parallel to the film surface and perpendicular to the polarization direction of the LPUV light.…”

Section: Introductionmentioning

confidence: 99%

Surface alignment of liquid crystal multilayers evaporated on photoaligned polyimide film observed by surface profiler

Oo¹,

Iwata²,

Kimura³

et al. 2005

Science and Technology of Advanced Materials

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The investigation of the surface alignment of liquid crystal (LC) multilayers evaporated on photoaligned polyimide vertical alignment (PI-VA) film was carried out by means of the novel three-dimensional (3D) surface profiler. We report the first use of the surface profiler to visualize a microscopic image of the monolayer arrangement of LC molecules in contact with the surface of photo-treated PI-VA film. The photoinduced anisotropy of partially UV-exposed PI-VA film can be visualized as a topological image of LC multilayers. It seems that the topology of LC multilayers is indicating the orientational distribution of LC molecules on the treated film. It was found that the periodically photoaligned PI-VA film surface can align an adsorbed LC monolayer and the LC molecular alignment can be extended to the bulk via the epitaxylike LC-LC interaction, i.e. a short-range molecular interaction. With regard to the unexposed PI-VA film surface, noticeable anisotropy in the monolayer alignment was not observed, indicating that the long-range elastic interaction may be responsible for the bulk alignment. The appearance of small droplets in the masked region may be presumably related to the dewetting phenomena. q

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Section: Introductionmentioning

confidence: 99%

Surface alignment of liquid crystal multilayers evaporated on photoaligned polyimide film observed by surface profiler

Oo¹,

Iwata²,

Kimura³

et al. 2005

Science and Technology of Advanced Materials

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“…an isomerization type 2)3) , a dimerization type 4) and a degradation type 5) , according to alignment-ability generation mechanism. Since it is frequently observed that the degradation type of PAF generates unnecessary over decomposed product during UV irradiation process 9) , the isomerization type of PAF is more preferable to simplify the manufacturing process of LCD, which can omit degradation materials removal steps, and we have put isomerization type PAF into practical production for fringe field switching (FFS) LCDs.…”

Section: Introductionmentioning

confidence: 99%

[Paper] Development of a Novel Azobenzene Diamine Compound for Photoalignment Film with High Transmittance

Tsukada

Ooki

Oguchi

et al. 2017

MTA

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“…Photochemical processes control LC orientation through a photochemical reaction, for example, photoisomerization, photocrosslinking or photodegradation. [8][9][10][11][12][13][14] In contrast, a photophysical process exploits the nonlinear optical (NLO) effects of an LC. 7,15 When a homeotropic LC is vertically irradiated with linearly polarized light, the interaction between the optical field and the LC molecules generates a torque to rotate the molecular director along the polarization direction, leading to homogeneous (in-plane) orientation.…”

Section: Introductionmentioning

confidence: 99%

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

Usui

Katayama

Wang

et al. 2016

Polym J

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Irradiation of dye-doped liquid crystals (LCs) with linearly polarized light leads to molecular reorientation, which manifests functional properties for various nonlinear optical (NLO) applications. Material designs with lower light intensity thresholds for molecular reorientation have been explored, and nematic LCs have been one of the most attractive choices because of the high NLO properties. Here we present a different approach to reduce light intensity for reorientation by modifying a substrate surface that controls initial molecular orientation in polymer-stabilized nematic LCs doped with oligothiophene. The surface of the glass substrate was treated with various concentrations of a silane coupler. Water contact angle measurement and analysis of samples using polarized optical microscopy revealed that surface anchoring in the initial state decreased as the silane coupler concentration decreased. The threshold intensity was successfully reduced by 30% simply by optimizing the silane coupler concentration. This finding clearly indicates that weak surface anchoring is key to the reduction of light intensity for molecular reorientation. INTRODUCTIONLiquid crystal (LC) materials have had a great impact on our modern information society. 1-3 Various LC materials and devices including LC displays, 3 smart windows, 4 reconfigurable optical elements 5 and tunable optical metamaterials 6 have been realized. 2 In these applications, light modulation is the most important factor and is achieved by orientational changes of LC molecules using an external field.Molecular reorientation of conventional LCs has been performed by an electric field. However, molecular reorientation triggered by an optical field has attracted attention because it enables the development of all-optical devices. 7,8 Such photoinduced molecular reorientation includes photochemical and photophysical processes. Photochemical processes control LC orientation through a photochemical reaction, for example, photoisomerization, photocrosslinking or photodegradation. [8][9][10][11][12][13][14] In contrast, a photophysical process exploits the nonlinear optical (NLO) effects of an LC. 7,15 When a homeotropic LC is vertically irradiated with linearly polarized light, the interaction between the optical field and the LC molecules generates a torque to rotate the molecular director along the polarization direction, leading to homogeneous (in-plane) orientation. On the other hand, rotation of the molecular director is disturbed both by the interaction between LCs and the glass substrate surface, a process which is also called surface anchoring, and by bulk elasticity. These torques reach a balance that determines a specific light intensity that allows

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Nematic homogeneous photo alignment by polyimide exposure to linearly polarized uv.

Cited by 193 publications

References 4 publications

Surface alignment of liquid crystal multilayers evaporated on photoaligned polyimide film observed by surface profiler

Surface alignment of liquid crystal multilayers evaporated on photoaligned polyimide film observed by surface profiler

[Paper] Development of a Novel Azobenzene Diamine Compound for Photoalignment Film with High Transmittance

Effect of surface treatment on molecular reorientation of polymer-stabilized liquid crystals doped with oligothiophene

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