• Proceedings of the Optical Society of Korea Conference
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• 2006.07a
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• pp.91-92
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• 2006

Liquid crystal (LC) alignment on $a-SiO_x$ thin film was investigated by means of X-ray photoemission spectroscopy and optical transmittance as we varied the deposition temperature and the target-to-substrate distance. LC molecules can be aligned vertically on $a-SiO_x$ film when the stoichiometric parameter x of $a-SiO_x$ is smaller than 1.56, but they can be aligned homogeneously when x is larger than 1.56. We also found that whether liquid crystals can be aligned vertically or homogeneously on $a-SiO_x$ film can be predicted simply by measuring the change in optical transmittance by deposition of $a-SiO_x$ thin film layers.

• Transactions on Electrical and Electronic Materials
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• v.7 no.1
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• pp.30-35
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• 2006

We have studied the motion of charged micro-particles that are immersed in a nematic liquid crystal (LC) and controlled by in-plane field. The LC is an anisotropic liquid such that the viscosity of the LC depends on flow direction, phase of the LC, and temperature, which affects the motion of the charged particles under the influence of electric field. This study shows that the motion of charged particles mainly depends on the applied voltage and the LC phase, but does not show any significant influence from the initial alignment of LC, although one may expect directional difference in drag force due to interaction between LC and particle. The viscosity changes due to temperature variations in nematic phase also show no signification influence on particle velocity when compared to the effect from varying in-plane field strength.

• Korean Journal of Optics and Photonics
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• v.22 no.2
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• pp.90-95
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• 2011

We propose a super-thin and light-weight liquid crystal cell, in which glass substrates are eliminated and polarizers are used as substrates. We fabricate a polarizer substrate by depositing a-SiOX as a buffer layer, indium-tin-oxide as a transparent conducting layer, and a-SiOX as an alignment layer on a polarizer sequentially at a low temperature. We use the ion-beam method to align liquid crystals on polarizer substrates.

• Prospectives of Industrial Chemistry
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• v.24 no.6
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• pp.19-31
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• 2021

자극응답성 액정 엘라스토머(liquid crystal elastomer)는 하이드로겔(hydrogel), 형상 기억 고분자(shape memory polymer)와 더불어 생체 특성을 모방한 인공 근육, 소프트 액추에이터 및 소프트 로봇을 위한 스마트 소재로 최근 높은 관심을 받고 있다. 특히, 액정 엘라스토머는 고무 탄성과 액정 이방성이 결합된 비등방성 탄성 고분자로, 열, 빛, 전기 및 수분과 같은 외부자극에 반응하여 가역적이며, 액정 분자들의 배향조절을 통한 프로그램된 변형이 가능하다. 액정 엘라스토머가 개념 증명을 하는 수준을 넘어 실제로 유용한 소프트 액추에이터 및 로봇 시스템에 적용되기 위해서는 우수한 구동력 및 작업 용량, 높은 구동 변형률, 빠른 응답 시간, 낮은 구동 온도, 다양한 외부 자극반응성 및 높은 에너지 전환 효율 등을 확보하는 것이 중요하다. 본 기고문에서는 액정 엘라스토머의 개념에 대해 소개하고, 이러한 소재가 소프트 액추에이터로써 광범위하게 활용될 수 있도록 다양한 성능들을 향상시킬 수 있는 방법에 대해 소개하고자 한다.

• Journal of the Korean Institute of Telematics and Electronics D
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• v.34D no.3
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• pp.114-122
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• 1997

The surface characteristics of polymers for liquid crystal alignment are studied by optical second-harmonic genertion (SHG) tecnique. Using SHG technique, the LC monolayers on rubbed polymer have already been studied. But, in this paper, the SH signals of polymer were observed and the orientational distribution of oriented polymer was studied. Te SHG experiments for side-chain type and main-chain type polymers are carried out as a function of rubbing strength. The orentational distribution of surface molecules of polymers is compared with the LC pretilt angle measured by the crystal rotation method.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2008.04a
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• pp.42-42
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• 2008

Considerable attention has been focused on the applications of flexible liquid crystal (LC)-based displays because of their many potential advantages, such as portability, durability, light weight, thin packaging, flexibility, and low power consumption. To develop flexible LCDs that are capable of delivering high-quality moving images, like conventional glass-substrate LCDs, the LC device structure must have a stable alignment layer of LC molecules, concurrently support uniform cell gaps, and tightly bind two flexible substrates under external tension. However, stable LC molecular alignment has not been achieved because of the layerless LC alignment, and consequently high-quality images cannot be guaranteed. To solve these critical problems, we have proposed a PDMS pixel-wall based bonding method via the IB irradiation was developed for fasten the two substrates together strongly and maintain uniform cell gaps. The effect of the IB irradiation on PDMS with PI surface was also evaluated by side structure configuration and a result of x-ray photoelectron spectroscopic analysis of PDMS interlayer as a function of binder with substrates. large number of PDMS pixel-walls are tightly fastened to the surface of each flexible substrate and could maintain a constant cell gap between the LC molecules without using any other epoxy or polymer. To enhance the electro-optical performance of the LC device, we applied an alignment method that creates pretilt angle on the PI surface via ion beam irradiation. Using this approach, our flexible LCDs have a contrast ratio of 132:1 and a response time of about 15 ms, resulting in highly reliable electro-optical performance in the bent state, comparable to that of glass-substrate LCDs.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.06a
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• pp.376-376
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• 2007

In Liquid Crystal Display (LCD) manufacturing, the organic over coat materials over coat materials for insulation layer of color filter with acryl ate was widely used. Therefore, we approach that the organic overcoat material can use to insulation layer for color filter and liquid crystal (LC) alignment layer in this research. The LC aligning capabilities was successful stuided for the first time. The organic overcoat layer and polymer layer was coated by spin-coating. In order to characterize the LC alignment, electric optic and residual DC and atomic force microscopy (AFM) image was used. The good LCD aligning capabilities treated on the organic overcoat thin film surfaces with ion beam exposure of $45^{\circ}$ above ion beam energy density of 1200 eV can be achieved. Also the good LCD alignment capabilities treated polymer on surfaces with ion beam exposure of $45^{\circ}$ above ion beam energy density of 1800 eV can be achieved. Comparing electro-optical characteristics between the Polyimide (PI) and the overcoat, the resultant transmittance of the overcoat considerably matched that of the PI and the residual DC also exhibited similar features with the PI.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2007.11a
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• pp.371-371
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• 2007

In this study, liquid crystal (LC) aligning capabilities for vertical alignment on the $CeO_x$ thin film by thermal evaporation method were investigated. Also, the control of pretilt angles and thermal stabilities of the NLC treated on $CeO_x$ thin film were investgated. The uniform LC alignment on the $CeO_x$ thin film surfaces and good thermal stabilities with thermal evaporation can be achieved. It is considerated that the LC alignment on the $CeO_x$ thin film by thermal evaporation is attributed to elastic interaction between LC molecules and micro-grooves at the $CeO_x$ thin film surface created by evaporation. In addition, it can be achieved the good electro-optical (EO) properties of the VA-LCD on $CeO_x$ thin film layer with oblique thermal evaporation.

• Polymer(Korea)
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• v.26 no.4
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• pp.431-438
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• 2002

We studied the orientation behavior and thermal stability of polyimide (PI) molecules under irradiation of polarized UV (PUV) using polarized fourier transform infrared (FTIR) spectroscopy. In the case of PUV-exposed PI films, the remaining PI molecules after photo-degradation showed molecular orientation perpendicular to the irradiated PUV polarization direction predominantly, due to the preferential degradation of PI molecules parallel to the irradiated PUV Polarization direction. On the other hand, the rubbing of PI films induced reorientation of the PI molecules parallel to the rubbing direction. We also investigated the thermal stability of the alignment layers furled by rubbing and PUV irradiation on the PI films using Polarized FTIR. The thermal stability of the PUV irradiated PI alignment layer is lower than that of the rubbed PI layer due to the fragmentation reaction of the PI by PUV.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2006.06a
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• pp.461-462
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• 2006

A single-gap and single-gamma transflective liquid-crystal (LC) display using patterned vertical alignment (PVA) mode was designed. In the device, a vertical electric field drives a vertically aligned LC to tilt down to optimize polarization efficiency. Electrodes of transmissive and reflective area were patterned $22.5^{\circ}$ and $45^{\circ}$ with respect to the polarizer so that a tilt-down direction of the LC director was $22.5^{\circ}$ and $45^{\circ}$ in the reflective and transmissive regions, respectively. In the device, the cell gap was the same for both regions, and the gamma curve matched each other in both regions because tilt angle of LC director was the same according to the applied voltage. Moreover, the dark state was irrespective of the cell retardation value at normal direction, which was highly important in massive fabrications. The switching principle and electro-optic characteristics of the device are reported herein.