• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.17 no.3
• /
• pp.305-310
• /
• 2004

We have studied the optimal phase retardation value of a homogeneously aligned liquid crystal (LC) driven by fringe-field when using the LC with positive dielectric anisotropy. In general, the transmittance of a homogeneous aligned LC cell under crossed polarizer is maximum when a twist angle of LC by in-plane rotation is 45$^{\circ}$ with polarizer and the cell retardation becomes λ/2. However, the device using the LC with positive dielectric anisotropy does not follow this since the degree of rotation of the LC is dependent on electrode position and in addition the LCs tilt up along the fringe-field. At the center of common and pixel electrode, the LC is most twisted around a middle position of a cell whereas at the edge position of pixel electrode, the LC is most twisted near bottom surface of a cell. Consequently, the optimal phase retardation of the device becomes much larger than λ/2 and the transmittance can be described using the combination of the in-plane switching and twisted nematic mode.

• Journal of Sensor Science and Technology
• /
• v.28 no.6
• /
• pp.341-344
• /
• 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.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.35 no.1
• /
• pp.58-65
• /
• 2022

The field of liquid crystal display (LCD) is constantly in the spotlight and the process of depositing an alignment layer in the LCD manufacturing process is very important to obtain excellent performance such as low-power driving and high-speed response to improve LCD performance. Therefore, research on liquid crystal (LC) alignment is being actively conducted. When manufacturing LCD, it is necessary to consider the effect of the alignment layer thickness as one of the factors affecting various LCD performances. In addition, previous studies confirmed the LC alignment characteristics correlate with the rotation speed in the spin coating process. Therefore, the electro-optical properties of the LCD were investigated by manufacturing a polyimide alignment layer by varying the rotation speed in the spin coating process in this study. It was confirmed that the thickness of the polyimide alignment layer was controlled according to the spin coating conditions. The average transmittances of anti-parallel LC cells at the spin coating speed of 2,500 rpm and 3,000 rpm are about 60%, which indicates that the LC cell has relatively higher performance. At the spin coating speed of 3,000 rpm, the voltage-transmittance curve of twisted nematic (TN) LC cell was below 1.5 V, which means that the TN LC cell operated at a low power. In addition, high-speed operating characteristics were confirmed with a response time of less than 30 ms. From these derived data, we confirmed that the ideal spin coating speed is 3,000 rpm. And these results provide an optimized polyimide alignment layer process when considering enhanced future LCD manufacturing.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.18 no.8
• /
• pp.724-728
• /
• 2005

Electro-optic characteristics of reflective hybrid aligned liquid crystal (LC) cell driven by fringe field using a nematic LC with positive dielectric anisotropy have been studied. Optimized optical configurations are achieved by using a single polarizer, half-wave film and a cell with quarter-wave retardation. The simulation results shows an optimum cell retardation of $0.30{\mu}m$. This value may allow a practical cell gap larger than $3{\mu}m$, which makes it easy to control in the manufacturing process. Furthermore, this LC cell with optimized cell parameters shows low wavelength dispersion and the contrast ratio greater than 5 over exists about $100{\circ}$ in vertical direction and $160{\circ}$ in horizontal direction. Also, when using the LC with positive dielectric anisotropy rather than negative dielectric anisotropy, the display shows low power consumption and fast response time.

• Transactions on Electrical and Electronic Materials
• /
• v.8 no.6
• /
• pp.274-277
• /
• 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.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2005.07a
• /
• pp.415-418
• /
• 2005

To understand effects of carbon nanotubes (CNTs) dispersed in nematic liquid crystal (NLC) on electro-optic characteristic and orientation of the LC, we CNT-doped homogeneously-aligned NLC cells driven by in-plane field have been fabricated. The CNTs were aligned with a LC director from the initial state to below critical ac field, whereas the CNTs disturbed the LC director field above critical ac field. We observed motional textures in the form of vertical stripes in the local area between electrodes, which were associated with a deformation of the LC director orientation. This indicates that CNTs start vibrating three dimensionally with translational motion. Further, the hysterisis studies of voltage-dependent transmittance under dc electric field show that the amount of residual dc, which is related to image sticking problem in liquid crystal displays, is greatly reduced due to ion trapping by CNTS while keeping operating voltage and response time about the same compared to the un-doped LC cell.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.19 no.5
• /
• pp.427-431
• /
• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.06a
• /
• pp.378-378
• /
• 2007

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

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2007.11a
• /
• pp.399-399
• /
• 2007

Recently, it is widely studied to liquid crystal (LC) alignment using ion-beam exposure. Because conventional rubbing method has some problems such as defects from dust and electrostatic charges during rubbing process. Therefore rubbing-free techniques like ion-beam method are strongly required. We studied LC alignment by controlling ion-beam energy density and electro-optical (EO) characteristics of twisted nematic LC on the polyimide surface. In this experiment, a good uniform alignment of the nematic liquid crystal (NLC) with the ion-beam exposure on the polyimide (PI) surface was observed. In addition, it can be achieved the good EO properties of the ion-beam-aligned twisted nematic liquid crystal display (TN-LCD) on PI surface.

• Korea Journal of Cosmetic Science
• /
• v.1 no.1
• /
• pp.19-29
• /
• 2019

In this work, we fabricated liquid crystal (LC) emulsions with fatty alcohol in order to stabilize high content ceramide in cosmetic formulation. We investigated the role of fatty alcohol and surfactant in the formation of higher order structure. As a result, we found that they play a crucial role to form higher order structure. SAXS study shows that ceramide can be incorporated up to 3% in cosmetic formulation with higher order structure and its stability was maintained up to 12 weeks at room temperature. According to WAXS study, the higher order structure can suppress the re-crystallization of ceramide in cosmetic formulation. Finally, we performed in vivo skin barrier recovery test for the damaged skin. LC emulsions with ceramide and O/W emulsions show significant effect in skin barrier recovery at D 1, D 2 and D 6 compared to the untreated condition. While only LC emulsions show significant skin recovery effect at D 14. We expect that LC emulsions are the promising skin carrier to stabilize ceramide and LC emulsions with ceramide can improve the skin barrier function.