• Korean Journal of Optics and Photonics
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• v.22 no.1
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• pp.23-29
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• 2011

Bistable chiral splay nematic liquid crystal display (BCSN LCD) is a memory type liquid crystal display using splay and $-\pi$ twist states as two stable states. When the cell thickness to pitch (d/p) ratio is 0.25, splay and $-\pi$ twist states have permanent memory time. However, when the transition from $-\pi$ twist state to splay state is caused by a fringe field, pixel regions show that the splay state is not perfect, but rather includes a contribution from the $-\pi$ twist state. In this paper, we propose a reflective BCSN LCD using $-\pi$ twist state in which the two stable states do not coexist. The fabricated reflective BCSN LC cell shows a high contrast ratio of over 30:1 and response times of 950 ms and 450 ms in vertical and fringe field switching, respectively. The proposed cell also shows wide viewing angle characteristics of $180^{\circ}$ in left- and right directions.

• Journal of the Society of Cosmetic Scientists of Korea
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• v.30 no.2
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• pp.279-294
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• 2004

This study described about a liquid crystalline technology that is used in cosmetics industry. Various intermediate phases may exist between solid and liquid. At high surfactant concentration, several liquid crystalline phases can be made to have formed. Although molecular arrangement with crystallization is not regular, it is known that more relative regular state is liquid crystalline or meso-phase than liquid phase. Usually, it described in detail about manufacturing method that explained about a kind of liquid crystalline technology in cosmetics, a new liquid crystalline technology, and makes liquid crystalline. Specialty, it introduced about kind of special an emulsifier to form liquid crystalline. There were hydrogenated lecithin, ceramide, dipalmitoylhydroxyproline, DEA-cetyl phosphate, Gemini-surfactant in representative raw material to form liquid crystalline. Liquid crystalline extent that used polarization microscope to observe formation, and appears best from 400times, 600times, 1,000times well appeared. Also, droplet particle size that liquid crystal is made best 1.0-10.0$\mu\textrm{m}$ be. General emulsion more than superior result that measures the skin moisturizing effect to take advantage of liquid crystalline technology of vitamin was seen. As presence at a clinical result, wave and general emulsion more than superior result (more than 20%) that measures skin moisturizing effect about liquid crystalline of vitamin B$\_$5/ were seen (ANOMA t-test, p<0.05)

• Polymer(Korea)
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• v.35 no.5
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• pp.493-498
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• 2011

Reactive mesogens were used to prepare photo-cured liquid crystal films in which orientations of liquid crystal molecules were preserved by crosslinked networks of cured reactive mesogens. The molecular orientations of liquid crystal mixtures of photo-reative mesogens and non-reactive nematic liquid crystals were studied and compared before and after curing reactions. The effects of temperature and the amount of the non-reactive nematic liquid crystal in the mixture on birefringence of the liquid crystal films were investigated. It was found that optical compensation films with different birefringence could be prepared by controlling the amount of the nematic liquid crystals in the reactive mesogen mixtures.

• Korean Journal of Optics and Photonics
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• v.19 no.1
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• pp.48-53
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• 2008

We propose an optical configuration to compensate dispersion characteristics in the dark state of normally black twisted nematic (NB-TN) liquid crystal display (LCD). We employed a half-wave plate (HWP) and a +A plate to achieve the superior dark state. By using the parameter space diagram (PSD) method, we could obtain the optimum values of parameters and the high contrast-ratio over 500 : 1 could be obtained. Furthermore, excellent dispersion characteristics were also obtained in the bright state. We could confirm the performance of the proposed structure using both the numerical calculations and the experiments.

• Elastomers and Composites
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• v.45 no.4
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• pp.286-290
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• 2010

Liquid-crystalline (LC) monomer, which was functionalized with a coumarin group on their extremity, was synthesized by UV light irradiation in their LC phases. LC monomer was converted into the dimers by the cycloaddition reaction of the coumarin group, and the LC phases were maintained after photodimerization reaction. The dimers showed LC phases in the wider temperature range than those of the corresponding monomer. Structures of the compound were identified by FT IR and $^1H$ NMR spectroscopies. Their phase transition temperatures and thermal stability were also investigated by differential scanning calorimetry (DSC), gel permeating chromatography (GPC) and polarized optical microscopy (POM). From optical polarizing microscopy, the prepared polymer shows enantiotropic liquid crystallinity with smectic and nematic textures.

• Polymer Science and Technology
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• v.15 no.3
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• pp.296-302
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• 2004

최근 분자들의 자기조립 현상을 나노-바이오 소자 개발에 응용하는 연구가 활발히 진행되고 있으며, 이러한 응용을 위한 대표적인 자기조립체로는 양친성 계면활성제, 블록공증합체, 콜로이드와 초분자체를 들 수 있다. 대부분의 콜로이드가 구형 모양으로 vander Waals interaction에 의하여 3-D결정 (crystal) 형태의 자기조립구조를 형성하는 반면에, 콜로이드를 제외한 대부분의 자기조립체는 적정 조건에서 액정 (liquid crystals), 결정 (crystal) 및 무정형 (amorphous)을 형성한다. 적용하고자 하는 응용의 범위와 재료의 특성에 따라서 각 상태 (phase)를 이용할 수 있으나, 액정상을 이용하는 것과 결정상을 이용하는 경우가 대부분이다. (중략)

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.404-410
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• 1994

The contrast and the brightness of a liquid crystal display panel are expressed in terms of the characteristic parameters of the rotational transformation on the Poincare sphere of the liquid crystal (LC) cell, which is the geometric representation of the electro-optic polarization transmission characteristics of the cell. From these, we show that the contrast and the brightness of the displayed images can be maximized when the rotation angle becomes $180^{\circ}$ for the rotational transformation corresponding to the change of the state of the LC cell from non-select to select state. state.

• Journal of Satellite, Information and Communications
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• v.9 no.1
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• pp.33-37
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• 2014

This paper introduces homogeneous liquid crystal (LC) orientations on chemically modulated polystyrene (PS) surfaces using various ion beam (IB) exposure time. Transparent PS was replaced with conventional polyimide material. As a non-contact process, IB bombardment process induced LC orientation in the direction parallel to the IB process. Through x-ray photoelectron spectroscopy, it was shown that the chemical compositional changes of the IB-irradiated PS surfaces were determined as a function of IB exposure time.Using this analysis, the optimal IB bombardment condition was determined at IB exposure time of up to 15 s. Moreover, thermal stability on IB-irradiated PS surfaces were carried out which showed that a relatively high IB exposure time induced a thermally stable LC alignment property.

• Korean Journal of Optics and Photonics
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• v.5 no.3
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• pp.411-417
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• 1994

The electro-optic polarization transmission characteristics of a liquid crystal (LC) cell is represented by a rotational transformation on the Poincare sphere, and its characteristic parameters, the angle and the axis of the rotation, are experimentally determined with respect to the voltage applied to the LC cell. From the experimental data obtained, we determine driving voltage for the LC cell to give the rotation angle near $180^{\circ}$ of the rotation for the change of the state of the LC cell from non-select to select state, which is a necessary condition for the realization of maximally bright images. The directions of the transmission axes of the polarizer and the analyzer which form a liquid crystal display panel together with the LC cell, are determined from the general characteristics of the rotaional transformation of the LC cell. cell.

• Polymer(Korea)
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• v.39 no.1
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• pp.185-190
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• 2015

Since a transition from liquid crystal to crystal state is slow for the large photo-reactive liquid crystal molecules, it needs a long time for recrystallization of LC242 molecules when lowering the temperature of the liquid crystal. Although liquid crystals usually align along one direction, the directions of individual liquid crystal molecules are little different from one another with increasing temperature, resulting in changes of birefringence of the liquid crystal films. When the photo-reactive liquid crystals are photo-cured, faster curing kinetics and much larger curing degrees are observed for the films cured at the liquid crystal phase.