Alignment Technology and Applications of Liquid Crystal Devices

Takatoh, Kohki; Sakamoto, Masanori; Hasegawa, Ray; Koden, Mitsushiro

doi:10.1201/9780367800949

Cited by 44 publications

(26 citation statements)

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“…In order to obtain well-defined surface anchoring conditions, an alignment layer is usually coated on the surface of the solid. The alignment layer can be, for example, a long-chain aliphatic layer, a spin-coated polymer film, or a thermally evaporated SiO film [21].…”

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

“…To obtain uniform planar alignment in liquid crystals, one of the feasible methods is mechanical rubbing of a spin-coated polymer film on the substrate. Although this method was developed by Mauguin more than one hundred years ago [57], it still dominates in the alignment process in the current manufacture of liquid crystal devices [21]. In the process, most often a thin film is spin-coated on a solid substrate from the solution of polyimides or nylon.…”

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

“…Then, the substrate is unidirectionally rubbed by a cloth with short fibers. The unidirectional rubbing results in the formation of uniform microgrooves on the substrate which has been considered as one of the two mechanisms responsible for the uniform planar anchoring [21]. The other mechanism is believed to be the reorganization of the polymer molecules [20][21].…”

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

“…By changing the angle between evaporation beam and substrate normal, one can obtain different surface structure of the oblique evaporated film. A tilt angle of up to 20 degree can be achieved by this method [21].…”

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

“…The physics and material properties of liquid crystals at interfaces have been one of the most important aspects in liquid crystal research [20]. While the knowledge of liquid crystal/solid interfaces may be in the state of maturity partly due to the crucial importance in liquid crystal displays [21], more efforts are still needed to make in order to understand the properties of liquid crystals interfaced to fluids or air. In contrast to most of the investigated liquid crystal/solid interfaces which are rigid, the fluid or air interfaces are obviously soft and hence deformable.…”

Section: Introductionmentioning

confidence: 99%

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Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring

Feng¹

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This dissertation concerns research on the structures and self-organization at liquid crystal interfaces laden with surface-active molecules. Of particular interest are the surface ordering phenomena occurring at interfaces formed between liquid crystals and a second fluid or between liquid crystals and air. A major part of the research has been dedicated to exploring the influence of surface-active molecules on the surface-induced pretransitional order and surface anchoring behavior at interfaces of liquid crystals. First, smectic surface layering transitions and nematic prewetting behavior have been investigated at surfactant-laden interfaces between isotropic liquid crystal phases and a water/glycerol phase whose polarity can be systematically varied by the water-to-glycerol ratio. It is shown that the polarity of the immiscible liquid phase can strongly influence the surface coverage of the surfactant molecules and hence the surface ordering behavior of liquid crystals. Second, surface properties of liquid crystal/air interfaces can be manipulated by the adsorption of a special kind of surface-active molecules, i.e., semifluorinated alkanes. The absorbed layer (also called the Gibbs film) of the semifluorinated alkane C 18 H 37 −C 12 F 25 undergoes at the liquid crystal/air interface a structural phase transition from a dilute state at higher temperatures to a dense state at lower temperatures. The structural phase transition causes an anchoring transition from homeotropic to planar of the liquid crystals at the air interfaces. If this transition occurs in the isotropic temperature range of the liquid crystals, it destroys the smectic surface order or changes the orientation of the nematic surface order. This dissertation further describes in situ AFM measurements on the self-organized structures formed in the Gibbs film of C 18 H 37 −C 12 F 25 at the liquid crystal/air interface. It is revealed that the Gibbs film of C 18 H 37 −C 12 F 25 is not featureless but consists of ordered hexagonal surface micelles which are similar to the Langmuir films formed by semifluorinated alkanes. einer hexagonaldichten Packung von Oberflächenmizellen besteht. Ähnliche Oberflächenmizellen wurden in übertragenen Langmuir-Filmen von semifluorinierten Alkanen beobachtet.

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Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

Section: Surface Anchoring At Rigid Interfacesmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring

Feng¹

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Förster Resonance Energy Transfer in Luminescent Solar Concentrators

et al. 2022

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Luminescent solar concentrators (LSCs) are an emerging technology to collect and channel light from a large absorption area into a smaller one. They are a complementary technology for traditional solar photovoltaics (PV), particularly suitable for application in urban or indoor environments where their custom colors and form factors, and performance under diffuse light conditions may be advantageous. Förster resonance energy transfer (FRET) has emerged as a valuable approach to overcome some of the intrinsic limitations of conventional single lumophore LSCs, such as reabsorption or reduced quantum efficiency. This review outlines the potential of FRET to boost LSC performance, using highlights from the literature to illustrate the key criteria that must be considered when designing an FRET‐LSC, including both the photophysical requirements of the FRET lumophores and their interaction with the host material. Based on these criteria, a list of design guidelines intended to aid researchers when they approach the design of a new FRET‐LSC system is presented. By highlighting the unanswered questions in this field, the authors aim to demonstrate the potential of FRET‐LSCs for both conventional solar‐harvesting and emerging LSC‐inspired technologies and hope to encourage participation from a diverse researcher base to address this exciting challenge.

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Synthesis and Study of Copolymers Bearing Two Coumarin Side Groups in Monomer Unit: Toward Photoalignment of Liquid Crystals

Chen

Han

Hou

et al. 2023

Macro Chemistry & Physics

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Photodimerization of coumarin derivatives in photoactive polymers under linearly polarized UV (LPUV) light irradiation is a photochemical reaction often used to prepare the surface alignment layer that can orient liquid crystals (LCs) due to the anisotropic interfacial interactions. Herein, the synthesis of a series of novel coumarin‐containing copolymers and their use for the photoalignment surface layer of LCs is reported. These copolymers have the particular feature of bearing two coumarin side groups in each monomer unit, which is designed to have a high content of the chromophores. The alignment of LCs induced by the photoalignment layers of the coumarin‐containing copolymers is investigated. It is found that the photoalignment layers can effectively induce orientation of LC molecules along the direction of the UV light polarization used to prepare the surface layers, with an order parameter of around 0.5 achieved by adjusting the preparation conditions. Moreover, the electro‐optical behaviors of LC cells made with the photoalignment layers are investigated, confirming the alignment of LCs without the use of rubbed surfaces. Optically inscribing the photoalignment layer for nonuniform and organized LC alignment is also demonstrated.

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Alignment Technology and Applications of Liquid Crystal Devices

Cited by 44 publications

References 0 publications

Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring

Structures and Self-Organization at Liquid Crystal Interfaces: Surface Ordering and Anchoring

Förster Resonance Energy Transfer in Luminescent Solar Concentrators

Synthesis and Study of Copolymers Bearing Two Coumarin Side Groups in Monomer Unit: Toward Photoalignment of Liquid Crystals

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