• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2018.06a
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• pp.142.1-142.1
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• 2018

This research presents a new field effect transistor (FET) by using liquid crystal gate dielectric with remote gate. The fabrication of thin-film transistors (TFTs) was used Indium tin oxide (ITO) for the source, drain, and gate electrodes, and indium gallium zinc oxide (IGZO) for the active semiconductor layer. 5CB liquid crystal was used for the gate dielectric material, and the remote gate and active layer were covered with the liquid crystal. The output and transfer characteristics of the LC-gated TFTs were investigated.

• Transactions on Electrical and Electronic Materials
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• v.12 no.6
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• pp.234-240
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• 2011

Electrically tunable focusing liquid crystal (LC) lenses are reviewed in this paper. The distribution of the orientations of LC directors which is controlled by electric fields results in a distribution of refractive indices of LC directors. The incident light can be modulated by the electrically tunable lens-like phase difference of the LC lens. We introduce the basic operating principles of LC lenses and discuss the structures of LC lenses. The major challenges of LC lenses are also discussed. We believe this paper provides a guideline for basic understanding of LC lenses.

• Journal of the Korean Applied Science and Technology
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• v.35 no.4
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• pp.1478-1486
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• 2018

Liquid crystals offer plenty of useful activities as improving the stability of emulsion, increasing moisturizing power, drug release, improving skin feeling and visual effect for cosmetics fields. In order to prepare stable semi-transparent gel emulsion, liquid crystal emulsification method was used. The emulsion stabilities of systems containing glycerin, fatty alcohols, surfactants, water and oil were investigated at various temperatures as time passed. The stabilities of all emulsions were evaluated by means of a polarizing microscope, SEM, rheometer, colorimeter and DSC. Even though the samples stored at $50^{\circ}C$ thermostatic chamber were occurred the reduction of hardness, turbidity and ${\Delta}H$ and the peak shift, the semi-transparent gel emulsion was very stable without separation between water and oils phase in emulsion.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.32 no.2
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• pp.141-146
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• 2019

Non-emissive LCDs need a backlight, and have difficulty implementing wide viewing angles due to differences in phase retardation depending on the behavior of the liquid crystals. Although wide viewing angles are good characteristics for devices such as TVs, they are not good for mobile devices. In this paper, we propose ways to design diffusers with ELC lenses to achieve wide and narrow viewing angles depending on the circumstances. A study was conducted on optimizing the design of a liquid lens diffuser with the same light as that for an OLED, by extracting design factors that affect the performance of the diffuser and applying the Taguchi method to them.

• Proceedings of the Polymer Society of Korea Conference
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• 2006.10a
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• pp.240-240
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• 2006

Thin films of poly(vinyl cinnamate) (PVCi) were prepared on indium tin oxide (ITO) glass and silicon substrates by conventional spin coating and subsequent drying process. The thicknesses of the films ranged 50-120 nm. The films' surface was treated by rubbing, ultraviolet exposure or their combinations in various ways with changing rubbing strength and exposure dose. These films were examined in detail in the aspects of surface morphology and chain orientation. Further, the anchoring and orientation behaviors of liquid crystals on the film surfaces were investigated. All the results will be discussed in detail.

• Korean Journal of Optics and Photonics
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• v.10 no.5
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• pp.386-390
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• 1999

Erasable polarization holographic grating was recorded with two-wave mixing in PCN which was side-chain liquid crystalline polymalonic esters containing two symmetrical 4-cyanoazobenzene as photoresponsive groups. The diffraction efficiency of recorded grating was measured and the characteristics of recording, decay in a dark room and erasing by circularly polarized light were investigated. As the results, birefringence, $\Delta$n of PCN was measured $6.5{\times}10^{-2}$, which was 0~100 times higher than those of crystals such as Fe:$LiNbO_3$, Ce:$BaTiO_3$ crystals. Dark decay rates was $4.3{\times}10^{-5}$ %/hour, which showed the possibility of application as data storage media.

• Journal of the Korean Institute of Telematics and Electronics
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• v.10 no.3
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• pp.10-22
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• 1973

Recently, nematic and nematic-cholesteric mixtures of substances have been discovered which have stimulated progress in electronics research and industry. In the liquid crystalline state, compounds with nematic mesopheses possess the ability to scatter light, depending on the strength of an applied electric field. The rewaking of interest in this fascinating but long-neglected area has occasioned the introduction of the subjects at the situation of the chemists. Since 1888 year, approximately 2000 compounds have been found to possess the unusual properties of what are commonly referred to as liquid crystals. In this paper, a comprehensive review will not be attempthed here. Nevertheless, some general information necessary to familarize the reader with rather exotic field will facilitate an understanding of the new effect and its application.

• 한국신재생에너지학회:학술대회논문집
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• 2009.06a
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• pp.711-711
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• 2009

Global warming has been widely recognized as a serious problem threatening the future of human beings. It is caused by the buildup in the atmosphere of greenhouse gases, such as carbon dioxide, methane, hydrofluorocarbons (HFCs), and sulfur hexafluoride (SF6). Particularly, SF6 has extremely high global warming potential compare to those of other global warming gases. One option for mitigating this greenhouse gas is the development of an effective process for capturing and separating these gases from anthropogenic sources. In general, gas hydrates can be formed under high pressure and low temperature. However, SF6 gas is known to form hydrate under relatively milder conditions. Therefore, technological and economical effects could be expected for the separation of SF6 gas from waste gas mixtures. In this study, we carried out morphological study for the SF6 hydrate crystals to understand its formation and growth mechanisms. The observations were made in high-pressure optical cell charged with liquid water and SF6 gas at constant pressure and temperature. Initially SF6 hydrate formed at the surface between gas and liquid regions, and then subsequent dendrite crystals grew at the wall above the gas/water interface. The visual observations of crystal nucleation, migration, growth and interference were reported. The detailed growth characteristics of SF6 hydrate crystals were discussed in this study.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.13 no.1
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• pp.5-14
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• 2003

Principles of a novel pulse growing method are described. The method realized in the crystal growing on a seed from melts under raw melt feeding provided a more reliable control of the crystallization process when producing large alkali halide crystals. The slow natural convection of the melt in the crucible at a constant melt level is intensified by rotating the crucible, while the crystal rotation favors a more symmetrical distribution of thermal stresses over the crystal cross-section. Optimum rotation parameters for the crucible and crystal have been determined. The spatial position oi the solid/liquid phase interface relatively to the melt surface, heaters and the crucible elements are considered. Basing on that consideration, a novel criterion is stated, that is, the immersion extent of the crystallization front (CF) convex toward the melt. When the crystal grows at a <> CF immersion, the raised CF may tear off from the melt partially or completely due to its weight. This results in avoid formation in the crystal. Experimental data on the radial crystal growth speed are discussed. This speed defines the formation of a gas phase layer at the crystal surface. The layer thickness il a function of time a temperature at specific values of pressure in the furnace and the free melt surface dimensions in the gap between the crystal and crucible wall. Analytical expressions have been derived for the impurity component mass transfer at the steady-state growth stage describing two independent processes, the impurity mass transfer along the <> path and its transit along the <> one. The heater (and thus the melt) temperature variation is inherent in any control system. It has been shown that when random temperature changes occur causing its lowering at a rate exceeding $0.5^{\circ}C/min$, a kind of the CF decoration by foreign impurities or by gas bubbles takes place. Short-term temperature changes at one heater or both result in local (i.e., at the front) redistribution of the preset axial growth speed.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.5
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• pp.228-236
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• 2009

In this study, we investigated morphological characteristics of $SF_6$ clathrate hydrate crystals to understand its formation and growth mechanism. $SF_6$ clathrate hydrate crystals were formed in high-pressure reaction cell charged with pure water and $SF_6$ gas at constant pressure and temperature. Two-phase ($SF_6$ gas/aqueous solution) and three-phase ($SF_6$ gas/aqueous solution/$SF_6$ liquid) conditions were investigated, In both conditions, dendritic shape hydrate crystals were grown as like fibriform crystals along upward growth direction at the gas/aqueous solution interface. In the case of the reaction process of three-phase condition, when the $SF_6$ gas bubbles which were generated in $SF_6$ liquid phase due to the reduction of reaction cell pressure stuck to the gas/aqueous interfaces, the hydrate phase were appeared at the surface of the bubbles. This paper presents the detail growth characteristics of $SF_6$ hydrate crystals including crystal nucleation, migration, growth and interference.