• 한국정보디스플레이학회:학술대회논문집
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• 2007.08a
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• pp.948-951
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• 2007

In order to improve the performance of LCD, chiral dopant is added to liquid crystal mixture. When we decide the rubbing direction, we must consider the rotation direction of liquid crystal molecules by chiral dopant. When the rotation direction of liquid crystal molecules caused by dielectric torque decided by rubbing direction and that decided by chiral dopant are coincided, the performance of LCD would be improved along to our initial cell design intentions.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.4
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• pp.426-431
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• 2004

We have studied the pressure-dependent liquid crystal's dynamics in a twisted nematic (TN) liquid crystal panel with thin film transistor by applying an external pressure to it. When the external pressure is applied to the panel in a dark state, the disclination lines were generated as a light leakage whereas they did not appear in a simple test cell that has only pixel and common electrodes. It was because the disclination lines were Provoked by the electric field between pixel electrode and data/gate bus line for active matrix driving. Consequently, the external pressure resulted in dynamic instability of the liquid crystal so that the disclination lines at the data/gate bus line intruded into the active area.

• Transactions on Electrical and Electronic Materials
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• v.7 no.6
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• pp.301-304
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• 2006

We studied the nematic liquid crystal (NLC) aligning capabilities using the new alignment material of the SiC (Silicon Carbide) thin film. The SiC thin film exhibits good chemical and thermal stability. The good thermal and chemical stability make SiC an attractive candidate for electronic applications. A vertical alignment of nematic liquid crystal by atomic beam exposure on the SiC thin film surface was achieved. The about $87^{\circ}$ of stable pretilt angle was achieved at the range from $30^{\circ}\;to\;45^{\circ}$ of incident angle. Consequently, the vertical alignment effect of liquid crystal electro-optical characteristic by the atomic beam alignment method on the SiC thin film layer can be achieved.

• Journal of Information Display
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• v.4 no.1
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• pp.1-8
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• 2003

Recent progress in both low pretilt and high pretilt defect free C1 surface stabilized ferroelectric liquid crystal (SSFLC) devices is reviewed. First, by numerical calculation to investigate the balance between surface azimuthal anchoring energy and bulk elastic energy within the confined chevron layer geometry of C1 and C2, it is possible to achieve a zigzag free C1 state by low azimuthal anchoring alignment with a low pretilt angle. The critical azimuthal anchoring coefficient for defect free C1 state is calculated. Its relationship with elastic constant, chevron angle as well as surface topography effect are also discussed. Second, using $5^{\circ}$ oblique SiO deposition alignment method a defect free, large memory angle, high contrast ratio and bistable C1 SSFLC display, which has potential for electronic paper applications has also been developed. The electrooptical properties and bistability of this device have been investigated. Various aspects of defect control are also discussed.

• Journal of the Korea Institute of Information and Communication Engineering
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• v.9 no.8
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• pp.1793-1798
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• 2005

We model the nucleation and motion of defects in the liquid crystal display device with inhomogeneous surface by using fast Q-tensor method, which can calculate scalar order parameter S and nucleation of the defect in the liquid crystal director field. In order to model the defect, homeotropic aligned liquid crystal cell with step inhomogeneous electrode which has a height of $1{\mu}m$ is used. From the simulation, we can observe the nucleation and line of the defect from surface inhomogeneity and the experiment is performed for confirmation.

• Electrical & Electronic Materials
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• v.10 no.1
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• pp.15-19
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• 1997

The characteristics of the response time and the viewing angle on twisted nematic (TN) liquid crystal display (LCD) and amorphous (a)-TN-LCD without rubbing were investigated. To measure the tansmission-voltage, response time, and viewing angle characteristics, we prepared three kinds of LC cells and then studied the surface liquid crystal alignment effect. It was found that the response time on A-TN-LCD was fast compared to the TN-I-CD, and the weak anchoring strength was attributed to the fast response time on a-TN-LCD. Also, we obtained the wide viewing angle characteristics on a-TN-LCD. The liquid crystal alignment of LCD device for electro-optical characteristics is discussed in the present paper.

• Journal of Information Display
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• v.2 no.3
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• pp.32-38
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• 2001

The most important parameter for TV application of LCD is a fast switching time for the display of moving image. To achieve faster switching time, the novel LC single materials with large dielectric anisotropies ($16{\sim}20$), high clearing temperatures ($195.5{\sim}237.4^{\circ}C$), broad nematic ranges (up to 169.9 $^{\circ}C$) and high birefringence ($0.254{\sim}0.2200$) were developed. KUR-series LC mixtures blended these single materials having significantly higher clearing temperatures and dielectric anisotropy values compared with conventional LC mixture. Especially, their clearing temperatures are $10{\sim}30^{\circ}C$ higher than their host mixture. These LC mixtures showing about lOms of high-speed switching time in Tv/Monitor of TFT LCD, is short enough to be addressed in a single time frame of 60Hz (16.7 ms). The threshold voltage $V_{th}$ was low enough to operate at a driving voltage of 5 V. The VHR values were found to be high enough for TFT-LCD in wide temperature range. Our novel LC mixtures are suitable materials for the inclusion in to LC mixtures for TV application of TN-LCD

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.68-71
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• 2003

To be able to show moving images without visual problems like blurring and tailing, the response time of liquid crystal display (LCDs) must be improved. In this paper we will discuss our progress in improving the response time by optimizing the cell configuration and the use of new liquid crystal mixtures. A 20.1inch diagonal UXGA IPS TFT-LCD has been developed having a response time as fast as l-frame time (16msec) for white-black operation and less than 16msec in all gray levels without applying ODC (Over Driving Circuit). This is very important because one of the technology to reduce motion blurring, the use of scanning backlight is conditioned by 16msec for all grays. The excellent gray-to-gray response can be explained by virtue of fundamental characteristics of S-IPS mode and makes a good contrast with the results of VA mode.

• Proceedings of the KIEE Conference
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• 2002.07c
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• pp.1933-1935
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• 2002

In this paper, we present a study of the structure and electro-optic behavior of hybrid liquid-crystal-silica sphere composite photonic crystals, formed by filling the (26% by volume) void space of fee (face centered cubic) silica opals infiltrated with a nematic liquid crystal. Three dimensional photonic crystals of visible range were fabricated via a self assembly method of silica spheres of submicron diameter. The expected fee structure was confirmed by scanning electron microscopy (SEM) of the dehydrated crystal with glass removed. The photonic crystal exhibited significant electric-field-induced shift of the optical Bragg reflection peak when the liquid crystal has the long molecular axis oriented parallel to the sphere surfaces.

• Korean Journal of Optics and Photonics
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• v.18 no.2
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• pp.100-104
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• 2007

We have measured the optical spectra while varying the temperature of photonic crystal fibers (PCFs) with periodic air holes in the cladding. These are liquid crystal infiltrated fibers. For the liquid crystal infiltrated PCFs, we obtained the transmission of several wavelengths at specific temperatures. The transmission power could be reduced by about $10\sim15dB$ by varying the applied temperature in the liquid crystal PCF. We expect that it is applicable as a wavelength switching device in the specific wavelength band.