• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.17 no.6
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• pp.622-632
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• 2004

We have studied how liquid crystal's rubbing direction and voltage driving method affect generation of disclination line. At first, generation of disclination line in vertical alignment(VA) cell and VA-twisted nematic(TN) cell has been examined. When liquid crystal's rubbing direction of bottom substrate was 0$^{\circ}$, the degree of generated disclination line was the smallest value. Further, the generation of disclination line above the electrode is less in the frame inversion than in the line inversion. Secondly, we have examined a generation of disclination line in reflective fringe-field switching cell. When the distance between common electrodes is over 3 ${\mu}{\textrm}{m}$ with on-state of one pixel and off-state of neighboring pixels, the reflectance appears only on-state pixel without generating reflectance in adjacent pixels.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
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• v.16 no.4
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• pp.322-329
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• 2003

We have studied how surface pretilt angle affects generation of disclination line in liquid-crystal-on silicon cells for 45$^{\circ}$-twisted nematic (TN) and vertical alignment (VA) modes with pixel size of 15$\mu\textrm{m}$. Our studies show that when the pretilt angle is increased from 0$^{\circ}$to 3$^{\circ}$ in the 45$^{\circ}$-TN cell, the disclination line at left side of on-pixel becomes weak and is well suppressed with $\theta$$\_$p/=3$^{\circ}$ although the pixel size Is decreased. In the VA cell, when the pretilt angle is decreased from 89$^{\circ}$ to 86$^{\circ}$, the disclination line at right side of the on-pixel is suppressed well and even for a smaller pixel size, it does not exist when $\theta$$\_$p/=86$^{\circ}$. The results inform that the pretilt angle strongly affects the image quality of microdisplays.

• 한국정보디스플레이학회:학술대회논문집
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• 2003.07a
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• pp.585-588
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• 2003

We have studied how rubbing direction affects generation of disclination line in transmissive microdisplay for $90^{\circ}$ twisted nematic (TN) mode with pixel size of $22.2{\mu}m$. The rubbing direction of bottom substrate is changed from $0^{\circ}$ to $-135^{\circ}$ with a decrease step of $45^{\circ}$, and the results show that the generation regions of the disclination line are of a smallest size in $-135^{\circ}$ direction. The results were the same although the pixel size decreased. Consequently, the use of proper rubbing direction of liquid crystal can help overcome the problems of low aperture ratio and low contrast ratio in transmissive-type microdisplays. In addition, the pretilt angle of initial liquid crystal is found to make an important contribution to generation of the disclination line.

• Journal of Information Display
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• v.8 no.2
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• pp.1-4
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• 2007

IPS and VA have evolved in various structures such as H-IPS, AS-IPS, and S-PVA gain more competitiveness. The new pixel structures inherently have more domains which cause disclination areas. The effect of disclination is no longer neglected in those structures. A new simulation tool based on FAST Q-tensor method enables one to predict the shape of disclinations and the resulting optical properties. It ensures more accurate results compared to vector-based simulation. We applied this simulation tool for the development of 26-inch wide monitor having H-IPS mode.

• 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.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2009.11a
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• pp.187-187
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• 2009

The PVA(patterned vertical alignment) mode has a excellent dark state at normal direction. but they has a disclination area at divided domain region at voltage on state. so this disclination make a slow response time and decrease transmittance. To overcome this problem, we research about polymer stabilized vertical alignment (PS-VA) method which was using the UV curable reactive mesogen. According to our research, UV exposure condition which was UV dosage condition effected to rising time and decay time and also threshold voltage.

• 한국정보디스플레이학회:학술대회논문집
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• 2004.08a
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• pp.1151-1154
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• 2004

In this study, we presented a novel method to calculate unknown voltages on the floating electrodes introduced in a unit pixel of TFT-LCDs using three-dimensional molecular director simulation. For the simulation of the potential distribution profiles generated under the influence of the floating electrodes, we used the floating boundary condition on the surface enclosing the floating electrodes. The constraint for the floating boundary condition was derived from the charge neutrality condition about the floating electrodes disconnected from voltage sources. For the pixel with the floating electrodes patterned between the pixel and the data electrodes, we simulated the molecular director and the potential distribution in three-dimension, and then observed the location of the disclination lines around the edge of the pixel electrode. As a result, it was revealed that the floating electrodes significantly affect the electro-optical characteristics such as the location of the disclination line.

• Journal of the Optical Society of Korea
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• v.18 no.6
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• pp.783-787
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• 2014

This paper presents an improved vertical alignment nematic liquid crystal mode characterized by the protrusions or slits of the top substrate and additional stripe type common electrodes with polarity switching of the bottom substrate to improve multi-domain vertically aligned (MVA) and patterned vertically aligned (PVA) nematic modes. MVA and PVA modes have disadvantages such as an LC disclination in the vicinity of the middle region of electrodes between the top and bottom protrusions in MVA mode or the top and bottom slits in PVA mode. Therefore, the stripe type common electrode generating a horizontal electric field and the protrusion or slit producing some pretilt of liquid crystals (LCs) were used to improve the LC disclination, which influences the transmittance and response speed. The simulation results showed that the proposed VA mode has higher transmittance than the MVA and PVA modes. As a result, the proposed VA mode can improve the response speed and transmittance remarkably, which makes it useful for upgrading the LCD display quality.

• 한국정보디스플레이학회:학술대회논문집
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• 2002.08a
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• pp.427-429
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• 2002

In this paper, we investigated dynamic behaviors of liquid crystal director profiles by simulating two different modeling equations based on vectorial and tensorial approaches. By performing 3-dimensional simulation for a unit pixel, we found that the simulation results from the each of modeling equations lead to different motional behaviors of liquid crystal directors around the disclination line. This is due to the fact that the vectorial approach has a physically meaningless sign of liquid crystal director ${\overline{n}}$. Consequently, it is clarified that the tensorial approach gives more realistic behaviors for the rotation of the directors around the disclination line when the voltages were removed since it maintains nematic symmetry that gives an equivalence of ${\overline{n}}$ and its opposite - ${\overline{n}}$.

• 한국정보디스플레이학회:학술대회논문집
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• 2006.08a
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• pp.621-624
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• 2006

Pixel structure of the fringe-field switching (FFS) mode to improve transmittance has been studied. New FFS structures related to the electrode structure at the edges of pixel, and the pixel electrode width and distance between electrodes was optimized. The former improves transmittance by minimizing the region of disclination lines. The latter improves it by increasing light efficiency above center of electrodes and also response time.