• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2006년도 추계학술대회 논문집 Vol.19
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• pp.53-54
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• 2006

We have studied the viewing angle control of a twist nematic liquid crystal display (TN-LCD). The TN-LCD exhibits a bad image quality along vertical direction, due to characteristics such as low contrast ratio and grey scale inversion. The proposed new TN-LCD has the function of switching between the wide viewing mode and narrow viewing angle mode using two tilted LC layers at both sides of a TN-cell Tilt angles of the two LC layers, $14^{\circ}$ and $60^{\circ}$ were required in both wide viewing angle and narrow viewing angle modes, respectively.

• Fibers and Polymers
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• 제2권1호
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• pp.123-130
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• 2001

Photoresponsive side chain copolymer and homopolymer containing an aminonitroazobenzene were synthesized for studying photoisomerization behavior and photo-induced anisotropy. Trans-to-cis photoisomerization was observed under the exposure of a circularly polarized visible light with UV-Vis absorption spectroscopy. Reorientation of polar azobenzene molecules induced optical anisotropy under a linearly polarized light at 532nm. Polarized absorption spectroscopy was employed to investigate the anisotropy of the polymer film during irradiationg of the excitation light. Layers of two photosensitive polymers were used for aligning liquid crystal(LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

• 한국전기전자재료학회논문지
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• 제13권1호
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• pp.75-79
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• 2000

In this study, we investigated the pretilt angle generation and liquid crystal (LC) alignment by ultravi-olet (UV) light irradiation during imidization of polymide. The generated pretilt angle of nematic (N) LC by using the in-situ photo-alignment method was smaller than that of the conventional UV photo-alignment method. Also, generated pretilt angle of NLC tends to increase by annealing. In case of using the polymer(AL-3046), we found that the in-situ Uv photo-alignment method has higher thermal stability of LC alignment, but it has a disadvantage to control pretilt angle.

• 한국전기전자재료학회논문지
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• 제16권3호
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• pp.214-218
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• 2003

We studied the nematic liquid crystal (NLC) aligning capabilities by the UV alignment method on a diamond like carbon (DLC) thin film surface A good LC alignment by UV exposure on the DLC thin film surface at 200${\AA}$ of layer thickness was achieved. Also, a good LC alignment by the UV alignment method on the DLC thin film surface was observed at annealing temperature of 180$^{\circ}C$. However, the alignment defect of the NLC was observed above annealing temperature of 200$^{\circ}C$. Consequently, the good thermal stability of LC alignment by the UV alignment method o the DLC thin film surface can be achieved.

• Macromolecular Research
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• 제8권4호
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• pp.172-178
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• 2000

We synthesized polymethacrylate and polyurethane bearing a photosensitive azobenzene chromophore. Photo-induced birefringence of the thin film was observed under a linearly polarized light(λ = 532 nm). Dynamic behaviors of birefringence in two polymers were investigated in terms of the rate constants of growth and decay. An induced dichroism was observed from polarized UV-VIS absorption spectroscopy. Layers of two photosensitive polymers were used for aligning liquid crystal (LC) molecules instead of one of the rubbed polyimide layers in the conventional twisted nematic cell. For producing homogeneous alignment of a nematic LC molecule, a linearly polarized light was exposed to the films of two polymers. The stability of the LC alignment upon the linearly polarized light exposure was also studied.

• Transactions on Electrical and Electronic Materials
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• 제8권6호
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• pp.274-277
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• 2007

In this study, liquid crystal(LC) aligning capabilities for homeotropic alignment on the $SiO_x$ thin film by electron beam evaporation method were investigated. Also, the control of pretilt angles and thermal stabilities of the nematic liquid crystal(NLC) treated on $SiO_x$ thin film were investigated. A high pretilt angle of about $86.5^{\circ}$ was obtained, and also the suitable pretilt angle of the NLC on the $SiO_x$ thin film at $10{\sim}50nm$ thickness with e-beam evaporation can be achieved. The uniform LC alignment and good thermal stabilities on the $SiO_x$ thin film surfaces with electron beam evaporation can be achieved. It is considered that the LC alignment on the $SiO_x$ thin film by electron beam evaporation is attributed to elastic interaction between LC molecules and micro-grooves at the $SiO_x$ thin film surface created by evaporation.

• 한국전기전자재료학회논문지
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• 제19권5호
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• pp.427-431
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• 2006

We have studied electro-optic characteristics of reflective $45^{\circ}$ twisted nematic liquid crystal display which implement the new LC orientation using of in-cell retarder film. For the embodiment of reflective liquid crystal display, essentially the optic compensation films was always needed and attached to the outside of glass substrate. In our study, these optic compensation film were not employed in reflective LC cell. On other hand we have employed the in-cell retarder to substitute the optic compensation film and were able to orient the LC molecules using this in-cell retarder. So we have developed the reflective LC cell that has good optical performances without any additional coating process on the in-cell retarder.

• 대한전자공학회논문지SD
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• 제41권8호
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• pp.59-65
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• 2004

본 논문에서는 IT(In-plane switching foisted nematic) 모드를 기반으로 광 투과 특성을 개선시킨 Pseudo-TN IPS(Pseudo-Twisted Nematic In-Plane Switching) 모드를 새롭게 제안하고 그 광 투과 특성을 분석하였다. PTN-IPS 모드의 경우 개구율을 향상시켜 투과율 면적을 향상시킴으로써 종래의 IT 모드보다 약 25%정도의 높은 광 투과 특성을 나타내었으며, 전압인가에 따른 광 투과율의 변화가 선형적이므로, 광 투과율 조절을 위한 액정의 제어가 IT 모드에 비해 용이함을 확인하였다. 또한, IT 모드에 비해 수평방향 대비비는 약 8%정도 특성이 열화 되었으나 수직 방향에 있어서는 약 20%이상의 특성개선을 확인 할 수 있었다. 이와 더불어, 기존 IT 모드가 가지고 있는 샐 갭에 대한 특성 및 장점을 가지고 있어, 차세대 액정 셀을 개발하는데 유용하게 사용될 것이라 생각된다.

• Journal of Information Display
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• 제2권4호
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• pp.19-22
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• 2001

In this paper, we describe the electro-optic effects of photonic crystals made of a synthetic opal filled with a nematic liquid crystal(LC). By applying an external electric field, a shift in the Bragg reflection peak position(stop band) and a field-induced change in its peak reflectivity are observed. These significant surface alignment effects of the opal-LC composite are discussed in a similar manner for Freederick-type transitions of LC within a confined geometry in the presence of external fields.

• 센서학회지
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• 제28권6호
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• pp.341-344
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• 2019

Liquid crystal (LC) mesophase materials manifest a variety of phase transitions. The optical properties of LCs are highly dependent upon the phase and orientation of the optical axis with respect to the polarization of incoming light. Studying the LC phase transitions is significantly important for a wide range of scientific and industrial applications. In this study, we demonstrate the propagation velocity of the phase boundary between the nematic and isotropic phase of 4-Cyano-4-pentylbiphenyl (5CB) liquid crystal for different electric fields using a polarized optical microscope. The results demonstrate that the propagation velocity of the phase boundary exhibits a peak value for a specific voltage, attributed to the supercooling of the isotropic phase of the LC. The analysis of the propagation velocity for different electric fields also provides a simple optical platform to measure the thermal anisotropy and voltage dependent thermal properties of the homogeneously aligned LC.