• Proceedings of the Materials Research Society of Korea Conference
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• 2003.03a
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• pp.129-129
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• 2003

최근에 능동 영역 액정 표시 소자(Active Matrix Liquid Crystal Display, AMLCD)에서 고해상도와 빠른 응답속도를 요구하게 되면서부터 다결정 실리콘(poly-Si) 박막 트랜지스터(Thin Film Transistor, TFT)가 쓰이게 되었다. 그리고 일반적으로 디스플레이의 기판을 상대적으로 저가의 유리를 사용하기 때문에 저온 공정이 필수적이다. 따라서 새로운 저온 결정화 방법과 부가적으로 최근 디스플레이 개발 동향 중 하나인 대화면에 적용 가능한 공정인 금속유도 결정화 (Silicide Mediated Crystallization, SMC)가 연구되고 있다. 이 소자는 top-gated coplanar구조로 설계되었다. (그림 1)(100) 실리콘 웨이퍼위에 3000$\AA$의 열산화막을 올리고, LPCVD로 55$0^{\circ}C$에서 비정질 실리콘(a-Si:H) 박막을 550$\AA$ 증착 시켰다. 그리고 시편은 SMC 방법으로 결정화 시켜 TEM(Transmission Electron Microscopy)으로 SMC 다결정 실리콘을 분석하였다. 그 위에 TFT의 게이트 산화막을 열산화막 만큼 우수한 TEOS(Tetraethoxysilane)소스로 사용하여 실리콘 산화막을 1000$\AA$ 형성하였고 게이트는 3000$\AA$ 두께로 몰리브덴을 스퍼터링을 통하여 형성하였다. 이 다결정 실리콘은 3$\times$10^15 cm^-2의 보론(B)을 도핑시켰다. 채널, 소스, 드래인을 정의하기 위해 플라즈마 식각이 이루어 졌으며, 실리콘 산화막과 실리콘 질화막으로 passivation하고, 알루미늄으로 전극을 형성하였다 그리고 마지막에 TFT의 출력특성과 전이특성을 측정함으로써 threshold voltage, the subthreshold slope 와 the field effect mobility를 계산하였다.

• Korean Journal of Optics and Photonics
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• v.19 no.4
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• pp.249-254
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• 2008

We developed a new x-ray image sensor utilizing a reflection-mode liquid crystal panel as its sensitive element, and tested its functionality by using it to obtain an x-ray image of a printed circuit board. In the liquid crystal x-ray image sensors hitherto reported, the liquid crystal layer is in direct contact with the photoconductive film which is deposited on a glass substrate. In the fabrication of the new x-ray image sensor, a liquid crystal panel is fabricated in the first step by using a pair of glass plates of a few centimeters thicknrss. Then one of the glass substrates is ground until its thickness is reduced to about $60\;{\mu}m$. After polishing the glass plate, dielectric films for high reflectance at 630 nm, a film of amorphous selenium for photoconduction, and a transparent conductive film for electrode are deposited in sequence. The new x-ray image sensor has several merits: primarily, fabrication of a large area sensor is more easily compared with the old fashioned x-ray image sensors. Since the reflection type liquid crystal panel has a very steep response curve, the new x-ray sensor has much more sensitivity to x-rays compared with the conventional x-ray area sensor, and the radiation dosage can be reduced down to less then 20%. By combining the new x-ray sensor with CCD camera technology, real-time x-ray images can be easily captured. We report the structure, fabrication process and characteristics of the new x-ray image sensor.

• Proceedings of the Korean Vacuum Society Conference
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• 2010.02a
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• pp.351-351
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• 2010

OLED(organic light emitting diode)는 액정디스플레이를 대체할 차세대 평판디스플레이로 많은 주목을 받고 있다. 현재 많이 사용되고 있는 OLED의 기판재료는 Glass기판이지만 차세대 Flexible한 display에서의 적용을 위해서는 가볍고 유연한 plastic을 기판 재료로 사용 할 것으로 보인다. 하지만 plastic이 기판재료로 된 OLED의 가장 큰 단점중의 하나가 수분과 산소에 민감하여 열화를 초래한다는 것이다. 이런 수분침투와 열화 과정으로 인해 OLED의 발광효과가 약해져 OLED의 수명과 직접적으로 연결된다. 하여 외부에서 OLED내부로 유입되는 산소, 수분으로 부터 발광재료와 전극의 산화를 방지하며 외부의 충격으로부터 소자를 보호하기 위한 봉지기술은 반드시 필요하다. 따라서 본 연구에서는, flexible한 OLED에 적용되는 금속 코팅한 막의 적층구조 및 기판의 노출온도에 따른 금속 코팅막의 수분침투 특성에 대해 MOCON의 weight gain test (WGT)를 통해 barrier layer에 대해 평가하고 이에 대한 mechanism을 확립하는데 그 목적이 있다. 금속을 코팅한 막은 OLED의 cathode와 anode 재료로 많이 사용되는 Al과 ITO를 sputter장비를 이용해 single layer와 double-layer의 두 가지 구조로 PET기판에 증착하였다. 증착한 Al막의 두께는 각각 50 nm, 100 nm, 200 nm, 400 nm 등 4가지로 하였다. double-layer의 경우에는 총 두께를 절반씩 기판의 양쪽에 증착하였다. 적층구조에 따른 수분침투 특성 평가 결과로 보면 같은 두께일 때 double-layer는 single layer에 비해서 모든 시편에서 수분의 투습율이 낮음으로써 더 좋은 수분침투의 barrier 특성을 나타내었다. 특히 100 nm이상인 경우 투습율은 예상한 값보다 50%이상 낮게 나타났다.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2008.11a
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• pp.305-309
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• 2008

This experimental study has been conducted to investigate the installation of the vertical flame holder shape in ramjet combustor, which affects on the film cooling effectiveness. All slot position, the film cooling effectiveness decreases because of the shear layer and high turbulence intensity between separated flows and coolant flows. When the flame holder is installed, film cooling effectiveness decreases abruptly on the beginning of the slot exit region due to the mixing effect. As the blowing rate increases, the film cooling effectiveness is increased for all cases due to the augmented momentum of injected coolant from the slot.

• Journal of the Korean Graphic Arts Communication Society
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• v.16 no.3
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• pp.15-27
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• 1998

Several aspects of polymer dispersed liquid crystal(PDLC) film properties make them interesting for display application. Most versions of PDLC materials are able to modulate light without the use of polarizers, which offers advantages in optical throughput(brightness) and viewing angle compared to polarizer-based display. In this papers, we attemped to doe minimum of remaining liquid crystals at polymer network for the liquid crystal-polymer composite (LCPC) films. In results, best phase separation behaviors turned out liquid crystal/monomer/oligomer mixture system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.26 no.9
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• pp.1267-1275
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• 2002

An experimental study was performed to investigate adiabatic wall temperature and heat transfer coefficient around a module cooled by forced air flow. The flow angle of attack to the module were 0$^{\circ}$and 45$^{\circ}$. In the first method, inlet air flow(1~7m/s) and input power.(3, 5, 7W) were varied after a heated module was placed on an adiabatic floor(320$\times$550$\times$1㎣). An adiabatic wall temperature was determinated to use liquid crystal film. In the second method to determinate heat transfer coefficient, inlet air flow(1~7m/s) and the heat flux of rubber heater(0.031~0.062W/$m^2$) were varied after an adiabatic module was placed on rubber heater covering up an adiabatic floor. Additional information is visualized by an oil-film method of the surface flow on the floor and the module. Plots of $T_{ad}$ and $h_{ad}$ show marked effects of flow development from the module and dispersion of thermal wake near the module. Certain key features of the data set obtained by this investigation may serve as a benchmark for thermal-design codes based on CFD.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.2
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• pp.238-246
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• 2004

This paper reports an experimental study around a module about forced air flow by blower (35${\times}$35${\times}$6㎣) in a portable personal computer model(200${\times}$235${\times}$10㎣). Experimental report is to know three data to investigate thermal resistance, adiabatic wall temperature and visualized fluid flow around the module by combination of the moving number and the arrangement method of blower. The channel inlet flow velocity has been varied between 0.26, 0.52 and 0.78㎧, and input power ( $Q_{p}$) to the module is 4W. To investigate thermal resistance. the heated module is mounted on two boards(110${\times}$110${\times}$1.2㎣, k=20.73, 0.494W/ $m^{\circ}C$) in parallel-plate channel to forced air flow. The temperature distribution were visualized by heated module on acrylic board(k=0.262W/ $m^{\circ}C$) using liquid crystal film. Fluid flow around the module were visualized using particle image velocimetry system.

• The Journal of Korea Institute of Information, Electronics, and Communication Technology
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• v.14 no.5
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• pp.362-368
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• 2021

A homeotropic liquid crystal (LC) alignment state on rubbed fluorinated self-assembled monolayers (FSAMs) is described according to alkyl chain length. A simple procedure, gas-phase method, for the preparation of FSAM was used. The average optical transmittance in the visible light range of FSAMs were 76.63% to 78.21%, which were superior to the conventional polyimide layer having a transmittance of 75.89%. In addition, the excellent homeotropic LC alignment characteristics of FSAMs were observed through pretilt angle measurement and polarized optical microscope images. By measuring the contact angles and the surface energies of FSAMs, it was confirmed that pretilt angles of LC molecules increased according to the alkyl chain length. High optical transparency and uniform homeotropic LC alignment characteristics of FSAMs showed the possibility of FSAMs as an LC alignment layers.

• Journal of the Korean Applied Science and Technology
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• v.39 no.5
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• pp.623-631
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• 2022

Using the design of experiment (DOE), factors affecting the particle size of hydrated liquid crystalline vesicles containing a high content of ceramide were analyzed and the mixture composition was optimized. Manufacturing temperature, amount of ethanol, and ultrasonic time were selected as the main variables affecting the droplet size of the vesicles, and the effect of these variables on the droplet size was examined through the signal to noise (S/N) ratios of Taguchi method and ANOVA analysis. In addition, mixture composition experiments of three lipid components constituting the vesicle membrane, hydrogenated phosphatidyl choline (HPC), cholesterol (Chol), and ceramide (Cer), were performed according to the simplex central design matrix of the mixture. Regression analysis was conducted with the experimental data to obtain a model equation, and the optimal mixing composition of the three lipid components to minimize the vesicle droplet size was determined as HPC (0.6), Chol (0.1), and Cer (0.3).

• Polymer(Korea)
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• v.33 no.5
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• pp.496-500
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• 2009

Optically compensated bend liquid crystal display (OCB-LCD) has many application fields owing to its fast response time and wide viewing angle. However, in order to operate the OCB-LCD in bend state, this device needs quick transitions from the initial splay state to bend state. Unlike conventional approach using transient high voltage for the transition, the OCB-LCD with high surface tilt angle, which was achieved by polymerization of UV curable reactive mesogen monomer under certain voltage, was manufactured and the cell showed bend state initially. Electro-optic and electrical characteristics of the cell were analyzed. The cell shows a fast response time owing to high surface pretilt angle and very low residual DC less than 0.1 V although another polymer layer is formed above polymer alignment layers.