Search

This study investigated the improvement of the electro-optical properties of a liquid crystal (LC) cell fabricated through brush coating using graphene oxide (GO) doping. The physical deformation of the surface was analyzed using atomic force microscopy. The size of the groove increased as the GO dopant concentration increased, but the direction of the groove along the brush direction was maintained. X-ray photoelectron spectroscopy analysis confirmed that the number of C–C and O–Sn bonds increased as the GO concentration increased. Since the van der Waals force on the surface increases as the number of O–metal bonds increases, we were able to determine why the anchoring energy of the LC alignment layer increased. This was confirmed by residual DC voltage and anchoring energy measurements that were later performed. As the GO concentration increased, the width of the hysteresis curve decreased, indicating that the residual DC voltage decreased. Additionally, the 15% GO-doped sample exhibited a significant increase in its anchoring energy up to 1.34 × 10−3 J/m2, which is similar to that of rubbed polyimide. It also secured a high level of electro-optical properties and demonstrated potential as a next-generation thin-film display despite being produced via a simple brush-coating process. [ABSTRACT FROM AUTHOR]

We investigated the alignment properties of liquid crystals (LC) on a brush-coated composite film made of graphene oxide and zinc oxide (GO-ZnO). The GO-ZnO composites were prepared using a sol-gel solution process, and the resulting solution was brush-coated onto indium tin oxide (ITO) glass. During the annealing process, an anisotropic roughened surface was created; however, the crystallinity analysis of GO-ZnO indicated that the brushed coating did not affect the crystalline structure significantly. The LC molecules exhibited stable alignment characteristics owing to the aligned surface roughness and hydrophilic properties of GO-ZnO, resulting in a homogeneously aligned structure. Residual DC measurements showed similar levels as the conventional rubbed polyimide cells, and a switching voltage of 1.7 V was observed. Brush coating is a cost-effective and simple deposition/alignment process, making it crucial in terms of cost-efficiency and process simplicity. Highlights: Demonstrate the application of brush-coated graphene oxide and zinc oxide films as alignment layers for LCDs. The sol-gel process, which converts precursor solutions into solid gel-like materials, allows production of homogeneously dispersed zinc oxide with graphene oxide. The functional groups present in graphene oxide offer opportunities for further chemical modifications and functionalization, enabling incorporation of specific properties and functionalities tailored toward specific applications. Combining GO and ZnO in a composite has a potential synergistic effect derived from its unique properties, making it a high-performance material for energy harvesting, photocatalysis and sensing applications. [ABSTRACT FROM AUTHOR]

Aluminum–nickel oxide and graphene oxide hybrid films are investigated in this study. The films produced via solution processing were doped with GO at three concentrations: 0, 5, and 15 wt%. The optical transmittances of the produced hybrid AlNiO films were examined for liquid crystal device applications, and their chemical properties were assessed via X-ray photoelectron spectroscopy. Atomic force microscopy and line profiling were used to examine the film surfaces. Polarized optical microscopy and pretilt angle analysis were used to confirm the uniform and homogeneous LC alignment on the hybrid AlNiO layer. The anisotropic oriented nano/microgroove structures on the surfaces of the films are believed to be due to the shear stress generated by the brush-coating process. LC cells assembled using the hybrid films showed stabler and faster switching performances with increasing GO doping. GO doping of the pure AlNiO film was also noted to increase the LC polar anchoring energy. [ABSTRACT FROM AUTHOR]

In this study, we describe the characterization and applicability of the liquid crystal (LC) system of brush-coated indium strontium oxide (InSrO) film. To achieve this aim, the film curing temperature was adjusted and the surface morphology was examined using atomic force microscopy and corresponding line profile data. In particular, we revealed a nano/microgroove anisotropic surface structure on the film after curing at 230°C, which was derived from the shear stress generated during movement of the wet brush hairs and subsequent active thermal oxidation of InSrO. In addition, x-ray photoelectron spectroscopy confirmed the presence of a well-formed InSrO film on the substrate. The film also exhibited hydrophilic properties at higher curing temperatures along with an amorphous structure. The InSrO film represented high optical transmittance to the LC system, and we confirmed the uniform and homogeneous LC alignment state using polarized optical microscopy and pre-tilt angle analyses. The oriented anisotropic film structure induced the alignment of LCs on the surface through geometric constraints. The InSrO film also exhibited advanced electro-optical performance with a fast response time and low operating voltage compared to the polyimide layer conventionally used in LC systems. From these results, we expect that brush-coated InSrO film will be a good alternative in advanced LC systems. [ABSTRACT FROM AUTHOR]

Liquid crystal (LC) orientation films are one of the key technologies in display devices. Currently, the commonly used polyimide rubbing method exposes problems such as micro‐defects and static electricity. In this paper, a thin film was prepared from a mixture of UV‐curable polymer and NiO solution using the UV‐NIL method. At room temperature, all three temperatures showed good liquid crystal alignment properties. However, in terms of thermal stability, it was more thermally stable in the 1‐min sample. This means that the formation of patterns has a significant impact on orientation properties, and the change in van der Waals force due to chemical changes also affects the orientation properties to some extent. In addition, excellent electro‐optical properties were also confirmed. [ABSTRACT FROM AUTHOR]

A nanostructured composite of ultraviolet (UV)-curable polymer and TaO was fabricated by UV imprinting and confirmed by physical and chemical analysis using atomic force microscopy (AFM), X-ray diffraction (XRD), and Fourier-transform infrared (FTIR), and X-ray photoelectron spectroscopy (XPS). Increasing the content of UV-curable polymers in the composite can successfully network with TaO and allow transfer. It was confirmed that nanostructured composite films could be successfully deposited on glass substrates depending on the UV-curable polymer content. AFM images with cross-sectional line profiles of 20 wt% composite films demonstrate that nanostructures can be successfully transferred. A uniform alignment was achieved with a stable pretilt angle on the transferred nanostructures. In addition, remarkably high-thermal budgets were observed due to the heat resistance of the films and nanostructures. Also, better C-V characteristics were observed compared to the rubbed polyimide liquid crystal (LC) cell. Therefore, nanostructured composites containing metal oxides and UV-curable polymers have great potential for LC devices considering their flexibility and sensitivity to heat such as rolling capability. This film can be used as an LC alignment layer with strong potential for high-quality LC applications. [ABSTRACT FROM AUTHOR]

This study investigated the modification effects of ion-beam exposure on polyacrylamide films according to molecular concentrations. Surface morphological examination using scanning electron microscopy showed increasing polyacrylamide particle size and film thicknesses with increasing concentrations. X-ray photoelectron spectroscopy and contact angle analysis were used to confirm the surface chemical reconstruction and increased surface energy after ion-beam exposure. As the molecular concentration increased, the changes were also observed to increase. The anisotropic ion-beam exposure induced strong van der Waals interactions with the liquid-crystals, leading to their uniform alignment. The uniform and homogeneous liquid-crystal alignment state was confirmed by polarized optical microscopy and pretilt angle analysis. Electro-optical performance evaluations showed the high potential of the ion-beam-exposed polyacrylamide film for use in liquid-crystal devices. Therefore, the correlation between the film molecular concentration and the IB process is successfully verified, and its applicability to liquid-crystal devices is confirmed. [ABSTRACT FROM AUTHOR]

Uniform and homogeneous liquid crystal (LC) alignment on a poly(ethylene‐co‐vinyl acetate) (EVA) layer subject to plasma ion‐beam (IB) treatment is confirmed. The layer molecular concentrations are controlled to 2, 4, and 6 wt%. Scanning electron microscopy exhibits a wrinkle pattern on the EVA surface that hinders LC alignment after IB treatment. However, X‐ray photoelectron spectroscopy shows chemical reconstruction on the surface; this induces strong van der Waals interactions with the LCs, which contribute to uniform LC alignment. The layer with higher molecular concentration is more heavily modified by IB treatment than that with low concentration, thereby achieving uniform LC alignment and overcoming topological disturbance. Contact angle analysis is used to verify that the surface energy increases via IB treatment; the uniform and homogeneous LC alignment is also confirmed by polarized optical microscopy and pretilt angle analysis. The EVA layer shows good optical transmittance and fine electro‐optical performances in terms of the switching and operating properties. Therefore, the plasma IB treatment is an effective method of deriving the surface characteristics of various polymeric materials for LC alignment, and the IB‐treated EVA layer has potential for application to LC systems. [ABSTRACT FROM AUTHOR]

This study uses imprint lithography to produce an anisotropic unidirectional indium gallium oxide (IGO) film for the uniform liquid crystal (LC) alignment layer. The curing temperature was controlled to 110, 180, and 250 °C during the process, and the 250 °C cured film presented a distinct one‐dimensional pattern transferred from the polydimethylsiloxane (PDMS) mold during scanning electron microscopy (SEM). X‐ray photoelectron spectroscopy (XPS) confirmed an active thermal oxidation effect at a high curing temperature, contributing to the formation of a unidirectional structure. This unidirectional IGO structure functioned as a guide for LCs and induced a uniform alignment state, verified by polarized optical microscopy (POM) and a pre‐tilt angle analysis. The IGO film also revealed improved thermal endurance to the LC alignment state and optical transmittance compared with the conventional rubbed polyimide (PI) layer. Given this performance, the one‐dimensional pattern‐imprinted IGO film can be a promising LC alignment layer for an advanced LC system. [ABSTRACT FROM AUTHOR]

This paper introduces anisotropic nickel yttrium oxide (NYO) film formed by the brush coating technique. X-ray photoelectron spectroscopy confirmed well-formed NYO film after the curing process, and the morphology of the surface was investigated using atomic force microscopy. The shear stress driven from brush hair movements caused the nano/micro-grooved anisotropic surface structure of NYO. This anisotropic surface induced uniform liquid crystal (LC) alignment on the surface, which was confirmed by pre-tilt angle analysis and polarized optical microscopy. The contact angle measurements revealed an increase in hydrophilicity at higher temperature curing, which contributed to homogenous LC alignment. The NYO film achieved good optical transmittance and thermal stability as an LC alignment layer. In addition, the film demonstrated good electro-optical properties, stable switching, and significantly enhanced operating voltage performance in a twisted-nematic LC system. Therefore, we expect that this brush coating method can be applied to various inorganic materials to achieve an advanced LC alignment layer. [ABSTRACT FROM AUTHOR]

Member failure due to low cycle fatigue may occur for steel structures under strong earthquakes. In this paper, the seismic response of single-layer latticed domes composed of welded round pipes is analyzed by the software Open System for Earthquake Engineering Simulation (OpenSees) incorporating low cyclic fatigue, in which the equations of initial camber for members are obtained from the buckling coefficient curve of compression members in Chinese codes. Single-layer latticed domes composed of welded round pipes with different parameters are modeled, and the seismic responses of the domes with and without material fatigue are compared by the incremental dynamic analysis. The results show that under strong earthquakes, the seismic responses including the maximum displacements and plastic development of the domes with fatigue are larger than those of the domes without fatigue. The collapsed PGAs decrease by 10-25% if low cycle fatigue is incorporated. Therefore, the low cycle fatigue of material should be taken into account in the seismic analyses of single-layer latticed domes under strong earthquakes. [ABSTRACT FROM AUTHOR]