• 한국정보디스플레이학회:학술대회논문집
• /
• 2007.08a
• /
• pp.356-359
• /
• 2007

Writable Cholesteric Liquid Crystal Display and the algorithm used to detect its image were developed. We could use any hard tip, ex: the tip of a forefinger, to directly write an image on the surface of Cholesteric Liquid Crystal Display (CHLCD). By measuring the capacitance of one pixel of test cell (12mm x 15mm/1x1), F-state or P-state could be detected. By measuring the capacitance of one pixel of 4.1" CHLCD (241um x 241um/ 320x320), F-state or Pstate could not be detected, due to the effect of parasitic capacitance. Therefore, high frequency measurement and the algorithm were developed to detect the image on CHLCD.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.302-305
• /
• 2008

We present a new touch screen method, which utilizes the variation of liquid crystal capacitance according to the touch event on the screen. It is integrated in the AMLCD with the conventional LTPS process. Its resolution is same as the display resolution as well as performs the multi-touch sensing function basically. The design concept and the operation are verified with the SPICE simulation.

• ETRI Journal
• /
• v.34 no.4
• /
• pp.633-636
• /
• 2012

A dynamic analysis of an amorphous silicon (a-Si) thin film transistor liquid crystal display (TFT-LCD) pixel is presented using new a-Si TFT and liquid crystal (LC) capacitance models for a Simulation Program with Integrated Circuit Emphasis (SPICE) simulator. This dynamic analysis will be useful when predicting the performance of LCDs. The a-Si TFT model is developed to accurately estimate a-Si TFT characteristics of a bias-dependent gate to source and gate to drain capacitance. Moreover, the LC capacitance model is developed using a simplified diode circuit model. It is possible to accurately predict TFT-LCD characteristics such as flicker phenomena when implementing the proposed simulation model.

• KIEE International Transactions on Electrophysics and Applications
• /
• v.11C no.4
• /
• pp.142-145
• /
• 2001

The residual DC phenomena in the in-plane switching(IPS)-liquid crystal display(LCD) by the voltage-transmittance (V-T) and capacitance-voltage (C-V) hysteresis method on rubbed polyimide (PI) surfaces were studied. We found that the residual DC voltage in the IPS-LCD was decreasing with the increasing concentration of cyano LCs. The residual DC voltage of the IPS-LCD can be improved by the high polarity of cyano LCs.

• Transactions of the Korean Society of Mechanical Engineers B
• /
• v.25 no.2
• /
• pp.205-215
• /
• 2001

An experimental study has been performed to investigate the heat transfer characteristics of fin and tube heat exchanger. The existing transient and steady methods are very difficult to apply for the measurements of heat transfer coefficients of a thin heat transfer model. In this study the lumped capacitance method was adopted. The heat transfer coefficients were measured by using the lumped capacitance method based on the liquid crystal thermography. The method is validated through impinging jet and flat plate flow experiments. The two experiments showed that the results of the lumped capacitance method with polycarbonate model showed very good agreements with those of the transient method with acryl model. The lumped capacitance method showed similar results regardless of the thickness of polycarbonate model. The method was also applied for the heat transfer coefficient measurements of a fin and tube heat exchanger. The quantitative heat transfer coefficients of the plate fin were successfully obtained. As the frontal velocity increased, the heat transfer coefficients were increased, but the color-band shape showed similar patterns regardless of frontal velocity.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.11a
• /
• pp.297-298
• /
• 2005

We have fabricated twisted nematic (TN) liquid crystal cells doped by carbon nanotubes (CNTs) with different CNT wt. %. With a minute amount doping, multi-walled CNTs did not perturb the liquid crystal orientations at the off- and on-state. The hysteresis studies of voltage-dependent capacitance (V-C) under the influence of electric field generated by ac and dc voltage show that the residual do, which is tightly related to image sticking problem in liquid crystal displays, is greatly reduced due to ion trapping by CNTs. Also, the V-C hysteresis shows dependency of capacitance on concentration of multi-walled CNTs.

• Proceedings of the Korean Vacuum Society Conference
• /
• 2015.08a
• /
• pp.163-163
• /
• 2015

The effect of nematic liquid crystal(5CB-4-Cyano-4'-pentylbiphenyl) on the amorphous indium gallium zinc oxide thin film transistors(a-IGZO TFTs) was investigated. Through dropping the 5CB on the a-IGZO TFT's channel layer which is deposited by RF-magnetron sputtering, properties of a-IGZO TFTs was dramatically improved. When drain bias was induced, 5CB molecules were oriented by Freedericksz transition generating positive charges to one side of dipoles. From increment of the capacitance by orientation of liquid crystals, the drain current was increased, and we analyzed these phenomena mathematically by using MOSFET model. Transfer characteristic showed improvement such as decreasing of subthreshold slope(SS) value 0.4 to 0.2 and 0.45 to 0.25 at linear region and saturation region, respectively. Furthermore, in positive bias system(PBS), prevention effect for electron trapping by 5CB liquid crystal dipoles was observed, which showing decrease of threshold voltage shift [(${\delta}V$]_TH) when induced +20V for 1~1000sec at the gate electrode.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
• /
• 2005.05a
• /
• pp.114-117
• /
• 2005

We have fabricated twisted nematic (TN) cell doped by carbon nanotubes (CNTs). The CNTs with a minute amount of doping do not perturb the liquid crystal orientation in the off- and on-state. The hysteresis studies of voltage-dependent transmittance and capacitance under ac and 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.

• 한국정보디스플레이학회:학술대회논문집
• /
• 2008.10a
• /
• pp.228-230
• /
• 2008

The response time characteristic of low voltage liquid crystals (LCs) is investigated and a new simulator for low voltage LCs is proposed. In order to enable low voltage operation, it is important to minimize Vth of LCs and variation of pixel voltage caused by dynamic capacitance operation of LC Display. Because dynamic capacitance variation is much larger for low voltage LC operation compared to that of conventional LC material, it is necessary to make a better model for dynamic capacitance operation. A proposed minimizing Vth of LCs and variation of pixel voltage study results through a new constant charge model improve response characteristics for low voltage LCs operation.

• Journal of the Korean Institute of Electrical and Electronic Material Engineers
• /
• v.32 no.5
• /
• pp.382-386
• /
• 2019

The alignment characteristics of liquid crystal (LC) molecules on a solution-derived lanthanum zinc oxide (LZO) film under ion-beam irradiation were demonstrated. Using the solution process, an LZO film was fabricated on the glass substrate and cured at $100^{\circ}C$. Afterwards, ion-beam irradiation was performed following the LC alignment method. Using this film, an LC cell was fabricated and the characteristics of the LC alignment were verified. Cross polarizing microscopy and the crystal rotation method were used to investigate the alignment state of the LC molecules on the LZO films. Furthermore, field emission scanning electron microscopy and X-ray photoelectron spectroscopy were used to explore the effect of the ion-beam irradiation on the LZO film. Through these, it was confirmed that the ion-beam irradiation induced surface modification, which demonstrated anisotropic physical and chemical surface characteristics. Due to this, uniform LC alignment was achieved. Finally, the residual DC and anchoring energy of the LC cell based on the LZO films were measured using a capacitance-voltage curve.