$Zn_{1-x}Cd_xO$ thin films were grown on (0001) sapphire substrates by pulsed laser deposition. The energy bandgap of $Zn_{1-x}Cd_xO$ films decreases withincreasing Cd content. An increase of Cd content also leads to the emission broadening and degraded crystallinity. The absorption edge and ultraviolet emission peak shift to lower energy from 3.357 eV to 3.295 eV and 3.338 eV to 3.157 eV, respectively, with increasing Cd content from 0.3% to 3%. The Stokes' shift between the absorption and emission indicates the increase of localization of exciton with Cd content.

We have designed a single gap transflective liquid crystal display (LCD) driven by a fringe electric field, in which the +LC (${\Delta}{\varepsilon}$=7.4, rubbing angle= $80^{\circ}$) is homogeneously aligned in the initial state. This device is a problem that the voltage-dependent transmittance and reflectance curves do not match each other. Thus a dual driving circuit is required. This study shows that optimization of the rubbing angle in the transmissive and reflective regions solves this problem so that the transflective display with a single cell gap and single gamma curve for reflective and transmissive region is possible.

In an effort to improve the electrical properties of ZnO:Al transparent electrode films, post-annealing treatment in hydrogen atmosphere was attempted with varying annealing time at 573 K for compatibility with typical display device fabrication processes. It was observed that carrier concentrations and mobilities increased with longer annealing time with small changes in crystallinity. This resulted in substantial decrease in resistivity from $4.80{\times}10^{-3}$ to $8.30{\times}10^{-4}{\Omega}cm$ due to increased carrier concentration. Such improvements in electrical properties are attributed to the passivation of the grain boundary surfaces. The optical properties of the films, which changed in accordance with the Burstein-Moss effect, were consistent with the observed changes in electrical properties.

We studied the nematic liquid crystal (NLC) alignment capability by the Ultraviolet (UV) alignment method on a-C:H thin-films, and investigated electro-optical performances of the UV aligned twisted nematic (TN)-liquid crystal display (LCD) with the UV exposure on a-C:H thin film surface. A good LC alignment by UV irradiation on a-C:H thin-film surfaces was achieved. Monodomain alignment of the UV aligned TN-LCD can be observed. The good electro-optical (EO) characteristics of the UV aligned TN-LCD was observed with oblique UV exposure on the a-C:H thin film surface for 1min.

In this study, Al doped ZnO(AZO)thin film were prepared on glass substrates by FTS(Facing targets Sputtering) system. We investigated electrical.. optical and structural properties of AZO thin film under the substrate temperature of the R.T. $100^{\circ}C$, $200^{\circ}C$, respectively, From XRD measurements it was found the crystallization of AZO thin film was increased with increasing the substrate temperature.

In this study Al electrode for OLED was deposited by FTS(Facing Targets Sputtering) system which can deposit thin films with low substrate damage. The Al thin films were deposited on the cell(LiF/EML/HTL/Bottom electrode) as a function of working gas such as Ar, Kr or mixed gas. Also Al thin films were prepared with working gas pressure (1, 6 mTorr ). The film thickness and I-V curve of Al/cell were evaluated by $\alpha$-step and semiconductor parameter (HP4156A) measurement. In the results, when Al thin film were deposited using pure Ar gas, the turn-on voltage of Al/cell was about 11[V]. And the turn-on voltage of Al/cell can be decrease to about 7[V].

$Nd:YVO_4$ 연속발진 레이저(CW laser:Continuous wave laser)로 제작한 다결정 실리콘 박막의 이온도핑 효과를 조사하였다. PECVD로 증착한 비정질 실리콘 박막을 CW 레이저를 조사하여 결정화한 후 $B_2H_6$ 플라즈마 이온 도즈량을 변화시켜 이온 도핑을 하고 급속열처리 방법과 퍼니스 어닐링 방법으로 도펀트 활성화를 하였다. 이온 도핑된 CW 다결정 실리콘 박막의 이온 도즈량에 따른 판저항 변화를 비교하고, 급속열처리(RTA: Rapid Thermal Annealing)와 퍼니스 어닐링(FA: Furnace Annealing) 전후의 결정성 변화를 라만 스펙트럼(Raman spectrum) 을 통하여 분석하였다. 이온 도즈량이 증가함에 따라 판저항은 감소하고, 어닐링 후 이온 도핑에 의해 손상된 박막이 복원됨을 확인 할 수 있다.

$Nd:YVO_4$ 연속발진 레이저 (CW laser)를 이용하여 다결정실리콘 (CLC poly-Si)을 제작하였다. CLC 다결정 실리콘의 결정화 영역은 결정립 크기에 따라 SLC(Sequential Lateral Crystallization) 영역, SLG(Super Lateral Grain) 영역 및 Small Grain 영역으로 구분된다. 레이저를 중첩스캔 하여 제작한 CLC 다결정실리콘의 경우, 레이저 스캔 경계에서 단결정립이 형성됨을 SEM으로 확인하고, CLC 다결정실리콘의 결정성을 XRD와 라만 스펙트럼(Raman spectrum)을 이용하여 조사하였다.

본 논문에서는 p-type 고분자 물질인 P3HT (Poly-3-hexylthiophene)를 잉크젯 프린팅 방식으로 활성화층을 적층함으로써 Organic thin film transistor를 제작하여 이에 대한 특성을 연구하였다. Piezoelectric 방식의 잉크젯 프린팅을 이용하여 P3HT single drop jetting 시 두께 $150{\sim}200{\AA}$, 직경 약 70 ~ 80 um정도의 drop profile을 얻을 수 있었다. P3HT의 solvent로서 Chlorobenzene을 사용하여 농도 약 0.5 wt.%의 Ink-jet용 ink를 제작하여 이를 Channel Width 37, 236 um 크기의 Au 전극 위에 jetting 하여 각각의 특성을 측정하였다. 상기 실험은 상온의 외부환경에서 실시되었으며 실험 결과 최대 ${\mu}=1{\times}10^{-2}\;cm^2/Vsec$, $I_{on}/I_{off}=10^3{\sim}10^4$ 정도로서 off current가 높은 편이나 이동도 측면에서는 다른 방법의 박막 증착 실험결과와 비교할 때 동등 수준의 결과를 얻을 수 있었다.

본 논문에서는 비정질 As-Ge-Se-S 박막의 에칭 레이트를 측정하였으며 As-Ge-Se-S 박막에 회절격자를 형성 시킨 후 선택적 에칭을 통한 엠보싱 홀로그램을 제작하였다. NaOH 수용액으로 0.26N, 0.33N, 0.40N 농도로 변화시키며 수행하였으며 에칭 시간에 따른 에칭되는 두께의 변화를 측정하였다. 에칭 레이트는 NaOH 용액의 농도가 0.26N, 0.33N, 0.40N 일 때 각각 $2.5{\AA}/s$, $3.3{\AA}/s$, $3.9{\AA}/s$ 였다. 또한 2차원 엠보싱 회절격자를 형성 시킨후 0.26N NaOH용액으로 60초간 선택적 에칭을 수행하여 AFM(Atomic Force Microscopy) 으로 측정한 결과 선명한 엠보싱 형태의 회절격자를 확인 할 수 있었다.

The silver photodoping effect in amorphous AsGeSeS chalcogenide thin films for holographic recording has been investigated using a HeNe laser ($\lambda$=632.8 nm). The chalcogenide films prepared in this work were thinner in comparison with the penetration depth of recording light ($d_p$=1.66 mm). The variation of the diffraction efficiency $(\eta)$ in amorphous chalcogende films exhibits a tendency, independently of the Ag photodoping. That is, n increases relatively rapidly at the beginning of the recording process, reaches the maximum $({\eta}_{max})$ and slowly decreases. In addition, the value of ${\eta}_{max}$ depends strongly on chalcogenide film thickness(d) and its peak among the films with d = 40, 80, 150, 300, and 633 nm is observed at d = 150 nm (approximately 1/2n), where n is refractive index of the chalcogenide (n=2.0). The ${\eta}$ is largely enhanced by Ag photodoping into the chalcogenides. In particular, the value of hmax in a bilayer of 10-nm-thick Ag/150-nm-thick AsGeSeS film is about 1.6%, which corresponds to ~20 times in comparison with that of the AsGeSeS film (without Ag).

As the demand of internet networks using backbone communication systems recently increased, the researches on the high-speed wideband optical communication systems are required. For high-speed optical communication systems, asymmetric sampled grating distributed feedback laser diodes (DFB-LDs) are developed and the reliability of DFB-LDs is examined. The reliability of DFB-LDs is performed by monitoring I-V and L-I characteristics and two degradation phenomena related to the electrical characteristics of LDs are observed during the life tests. The first degradation phenomenon by increasing the reverse current is considered as a formation of leakage current path enough to prevent lasing operation in lateral blocking layer near active region of lasers. The second degradation phenomenon by decreasing the forward current is considered as activation of non-radiative Auger recombination process by thermal energy and the second degradation phenomenon is recovered after the off-test period at room temperature Eventually, evaluating the reliability of DFB LDs can allow us to improved the manufacturability in high-volume manufacturing.

Homogeneously aligned nematic liquid crystal modes are representatively the -FFS (fringe-field switching) mode using liquid crystal (-LC) with negative dielectric anisotropy, the +FFS mode and the IPS (in-plane switching) mode using +LC with positive dielectric anisotropy. In view of image quality evaluation standard of LCD, we compared characteristics of the brightness, the contrast ratio (CR) and color shift when the modes have respectively optimized phase retardation values $(d{\Delta}n)$. Consequently, in the most sensitively viewing angle of a man's physical vision, both FFS modes have advantage over the IPS mode from the brightness & the CR point of view. We are also confirmed that the +FFS mode out of them shows the smallest color shift according to all viewing directions in grey levels.

We have studied electrode-optic characteristics of IPS (in-plane switching) mode with electrode on top substrate. Because the IPS mode does not have electrode on top substrate. it shows not only slow response time due to weak electric field but also slow discharging problem when electrostatic field is generated after fabricating the cell. To solve these problems. we have formed additional electrode including dielectric layer in the inner part of the cell and studied electrode-optic characteristics of new IPS cell by changing thickness of dielectric layer.

We have studied a field sequential liquid crystal display (FSLCD) with electrically controlled birefringence (ECB). The ECB mode exhibiting fast response time, high transmittance, low operating voltage and adequate viewing angle. The positive liquid crystal (LC) is better than negative LC on dielectric anisotropy, birefringence and rotational viscosity. Because $K_{11}$ value out of the elastic coefficient of LC is also larger than $K_{22}$ value, decay time of VA-ECB is advantage. However, the transmittance & response time reduced with decreasing the cell gap. This drawback can be overcome by using LC with high ${\Delta}n$ but VA-ECB is occured loss of light efficiency because the $\gamma$ value increased by high ${\Delta}n$ of LC. Consequently, the HA-ECB mode is one of strongest candidate for FSLCD application.

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.

Liquid crystal (LC) alignment using a photoalignment method by irradiation of polarized ultraviolet (UV) on an alignment layer has been investigated. Photoalignment method exhibits weaker anchoring energy than rubbing method so that we have studied electro-optic characteristics of fringe-field switching (FFS) mode with alignment layers using the photo and rubbing alignment methods. The cell using photo alignment layer shows lower threshold and operation voltage than those using rubbed alignment layer. Also. the former method shows higher transmittance than that of the latter.

Eye Glass Display (EGD) with microdisplay to realize the virtual display can make the large screen, so virtual image has been developed by using microdisplay panel. This paper shows study of low cost lens design and simulation for microdisplay system with 0.6"LCoS panel. Lens design optimized consider to spherical aberration, astigmatism, distortion, and chromatic aberration. Code V is used and it designed an aspheric lens about exit pupil 6mm, eye relief 20mm and 35 degree of field of view (FOV). With the application this aspheric lens to liquid crystal on silicon (LCOS) type's microdisplay, virtual image showed 50 inch at 2m. One side of the aspheric lens was constituted from diffractive optical element (DOE) for the improvement in a performance. It had less than 2.5% of distortion value and modulation transfer function in axial had 20% of resolution with 32 lp/mm spatial frequency. The optical system is suitable for display of 15.6 mm-diagonal with SVGA.

The properties of phosphorus doped ZnO multilayer thin films deposited on (001) sapphire substrates by pulsed laser deposition (PLD) were investigated by using annealing treatment at various annealing temperature after deposition. The phosphorus doped ZnO multilayer was composed of phosphorus doped ZnO layer and two pure ZnO layers on sapphire substrate. The structural. electrical and optical properties of the ZnOthin films were measured by X-ray diffraction (XRD). Hall measurements and photoluminescence (PL). As the annealing temperature optimized. the electrical properties of the ZnO multilayer showed a electron concentration of $1.56{\times}10^{16}/cm^3$, a resistivity of 17.97 ${\Omega}cm$. It was observed the electrical property of the film was changed by dopant activation effect as thermal annealing process

PDP 방전 셀의 최적화 및 진공자외선 발광효율을 향상시키기 위한 목적으로 AC - PDP 미소방전에서 제논 여기종 원자의 밀도를 측정하는 레이저 흡수법을 개발하였다. 본 연구에서는 PDP 셀의 기체 압력을 350Torr, 제논 함량 10%로 고정하고, 전극 위에서의 여러 위치에서 준안정 준위 제논의 밀도를 흡수법으로 측정하였다. 실험 결과 제논 여기종의 밀도의 최대값은 전극의 위치(가장자리에서 안쪽으로의 거리)가 $50{\mu}m$, $120{\mu},\;150{\mu}m$ 일 때 $3.5{\times}10^{12}cm^{-3}$, $2.8{\times}10^{12}cm^{-3}$, $2.2{\times}10^{12}cm^{-3}$로 나타났다.

현재 널리 상용되어 있는PDP는 3전극 변방전형이다. 3전극 면장전형 PDP는 주방전이 유전체 아래에 서로 평행하게 위치하고 있는 ITO투명전극 사이에서 발생한다. 따라서 방전시의 전기장은 MgO 보호막 위에서 아치형태로 형성되게 된다. 플라스마 방전 시 전자에 의해 이온화된 이온 입자들은 전기장에 의해 그 방전경로가 정해지게 된다. 물론 전기장은 표면에서 수직이지만 전기장에 의해 가속되어진 이온입자들은 MgO 보호막에 기울어져서 입사하게 된다. 따라서 플라스마 방전시의 이온들의 MgO 보호막으로의 입사각은 매우 다양하다. $\gamma$-FIB (Focused ion beam) 시스템은 이온입사에 의한 물질의 이차전자방출계수 측정에 효과적인 장비이다. 본 실험은 이러한 $\gamma$-FIB 시스템을 이용하여 다양한 각도로 입사하는 이온빔에 의한 MgO 보호막의 이차전자방출계수를 측정하였다. 또한 이온화 에너지가 다른 여러 종류의 불활성 기체를 사용하여 이온의 입사하는 각도에 따른 MgO 보호막의 일함수를 측정하였다. 이온빔의 입사각은 각각 $0^{\circ}$, $10^{\circ}$, $20^{\circ}$, $30^{\circ}$로 변화시키면서 이차전자방출계수 및 일함수를 측정하였다. 이러한 실험을 통해 입사각이 클수록 이차전자방출계수는 증가하고 일수는 감소하는 것을 확인 할 수 있었다.

이번 실험에서는 변방전형 교류 PDP에서의 3차원적인 전자온도와 이온밀도의 측정을 마이크로 랑뮈르 탐침법을 통해 실험적으로 연구하였다. 스테핑 모터에 연결된 마이크로 랑뮈르 탐침은 20um씩 움직이며 탐침에 인가하는 플러스와 마이너스의 직류전압을 통해 I-V곡선을 구할 수 있고 이를 통해서 전자온도와 플라스마 밀도를 구할 수 있다. Ne+Xe(4%) 200Torr의 혼합가스에서 전극의 테두리를 따라(X축) 전자온도 및 플라스마 밀도를 측정한 결과 중앙지점에서와 전극의 경계지역에서 이온밀도는 $7.69{\sim}11.1{\times}10^{11}cm^{-3}$ 까지 측정되었다. 또한 전자온도는 플라스마 밀도와 균형적인 관계에 있다는 것은 주목할 만하다. 전자온도는 전극 사이의 중심에서 가장 적게 1.3 ~ 3.15eV까지 측정되었다. Y축으로 측정했을 경우 이온 밀도와 전자온도는 전극 갭 중앙에서부터 약 80um 떨어진 지점에서 서로 교차하며 증가 및 감소였으며 이온밀도는 $8.3{\sim}11.1{\times}10^{11}cm^{-3}$로 측정되었고 전자온도는 이와 균형적인 관계를 가지고 1.2~1.6eV로 측정되었다. 또한 이러한 특성은 AC PDP 에서 나타나는 줄무늬 현상과 관련이 있는 것으로 보인다. Z축으로 측정했을 경우 약 125um높이에서 가장 높게 측정되었으며 $1.1{\times}10^{12}cm^{-3}$정도로 측정되었다.

AC-PDP에서 발광 휘도와 발광 효율의 개선은 매우 중요한 과제중의 하나이다. 높은 발광 휘도와 발광 효율을 위해선 VUV의 높은 발광 효율이 요구되어진다. 이 실험에서는 AC-PDP에서 Ne-Xe의 2원 혼합기체와 He-Ne-Xe의 3원 혼합기체의 VUV 발광 세기를 측정하였다. 기체 압력은 200 Torr, 300 Torr, 400 Torr, 500 Torr로 유지하였고, Xe 혼합비는 1%, 2%, 4%, 7%, 10%, 15%를 사용하였다. 진공자외선 발광 세기는 He-Ne-Xe의 3원 혼합기체가 Ne-Xe의 2원 혼합기체보다 발광 세기가 훨씬 높다는 것을 알 수 있었다. 그리고 Xe 함량이 증가함에 따라 공명선인 147 nm의 발광 세기는 Xe 혼합비가 약 10%까지는 증가하다가 10% 이후에는 포화되고, 반면 분자선인 173 nm은 Xe 함량과 가스 압력이 증가함에 따라 발광 세기가 증가하였다.

In applying LCD to TV application, one of the most significant factors to be improved is image sticking on the moving picture. LCD is different from CRT in the sense that it's continuous passive device, whichholds images in entire frame period, while impulsetype device generate image in very short time. We realized articulate image generation similar to CRT by CCFL blinking drive and TN-LCD overdriving. As a result, reduced image sticking phenomenon was validated by naked eye and response time measureme.

We investigated the fabrication and characteristics of spin-polarized LEDs based on GaN using (Ga,Mn)N as spin injection source. (Ga,Mn)N thin films were found to exhibit the ferromagnetic ordering above room temperature and the negative MR up to room temperature. The electrical characteristics in spin LEDs did not degraded in spite of the insertion of (Ga,Mn)N films. In EL spectra of spin LEDs, it is confirmed that spin LEDs emit the strong light at 7 K as well as room temperature. These results suggest that it is possible to emit spin-polarized light in our spin LEDs.

In this study, we have investigated transient properties of top emission organic light emitting diode (OLED) with a red electrophosphorescent dopant. The emission spectrum shows a strong peak at 620 nm accompanied with a small peak at 675 nm in the red region. Time evolution of electrophosphorescence reveals a decay time of 703 ms at a voltage pulse of 5 V in a device with an emitting area of 20 $mm^2$. Rise and delay times vary from 450 to 14 ms and 73 to 3 ms, respectively, as the voltage amplitude increases from 4.5 to 10 V. These results are compared with the red emitting device without an electron injection layer.

본 연구에서는 저온 액상반응법을 이용하여 활성제 Eu의 농도를 10wt%로 도핑하고 열처리를 각각 450, 700, $900^{\circ}C$로 1h 유지하여 $Gd_2O_3:Eu^{3+}$ 나노형광체를 합성하였다. 제조된 형광체의 결정화, 입자크기를 XRD, BET로 분석하였고, 이들이 발광 휘도에 미치는 영향을 확인하였다. 또한 합성된 형광체의 PL(photoluminescence) 특성을 알아보기 위해 여기파장 254nm 의한 발광스펙트럼, 611nm에 의한 여기스펙트럼을 조사하였다. 발광 특성은 611nm에서 주 peak을 갖는 $Eu^{3+}$ 이온에 의한 $^5D_0-^7F_{J(J=0,1,2)}$ 전이에 기인된 전형적인 Red 형광체의 특성을 나타냈고, 입자크기는 평균 20-60nm 정도이고, 발광강도는 열처리 온도가 증가함에 따라 향상되었다.

Top emission OLED 소자의 안정성 위하여 Parylene을 보호층으로 적용하였다. 고분자화 방법을 이용하여 증착된 Parylene은 진공공정상온에서 증착가능하기 때문에 열에 의한 OLED 소자의 열화를 방지하며 높은 광투과율과 우수한 투습습성에 의하여 고효율 장수명을 OLED 소자에 적합하다. Parylene 5 ${\mu}m$ 의 광투과율은 90 %이상 측정 되었으며 투습율은 0.4849 $g/m^2day$로 측정되었다. Parylene의 보호층로서의 영향을 살펴보기 위하여, 보호층이 형성된 소자와 보호층이 형성되지 않은 소자를 제작하여 대기중에서 그 특성을 측정 비교하였다. 두 제작된 top emission OLED 소자는 최대 휘도가 1000 $cd/m^2$ 이상 측정되었으며, parylene 보호층 공정에 의한 소자의 구동 특성 변화는 나타나지 않았다. 대기중에서 초기휘도 200 $cd/m^2$로 측정된 parylene 보호층이 형성된 소자는 수명이 5 이었고, 보호층이 형성되지 않는 소자의 수명에 비하여 2배 이상 증가하였다.

We report high performance poly (3-hexylthiophene) organic field-effect transistors fabricated on a plastic substrate. The polymer active channel layer was directly printed by the rubber stamp printing method with a pre-patterned elastomer stamp. As a result. organic transistors having average field-effect mobility of 0.079 $cm^2/Vs$ and on/off ratio of $10^4{\sim}10^5$ were realized on a plastic substrate. Also, through the investigation of the molecular ordering of rubber-stamp-printed poly (3-hexylthiophene) films using synchrotron grazing-incidence X-ray diffraction measurements, the films were found to have edge-on structure which is favorable in realizing high performance organic transistors.

공정시 플라스틱 기판의 변형을 방지하기 위해 PC(Polycarbonate) 기판을 약 12시간 동안 pre-annealing시킨 다음 SiN(silicon nitride)와 PI(Poly-imide)를 각각 Sputter와 Spin-Coater를 이용하여 Coating하였다. 완성된 PC 기판위에 Themal Evaporation으로 Calsium을 증착한 뒤 Al을 올렸다. Calsium 증착 된면에 삼성 코닝의 글래스를 UV resin으로 부착 시킨 다음 상온에서 투습률을 측정하였다. 측정 간격은 12시간으로 하였으며 Calsium Test 의 정확도 향상을 위해 CCD Camera로 측정하여 컴퓨터로 분석하였다. 그래픽 저장 파일은 저장시 이미지 손실을 방지하기 위해 Bitmap방식을 그대로 사용 하였으며 정확도 향상을 위한 분석 프로그램은 MicroSoft 사의 Visual C++로 작성하였다. 화상 처리 면적은 컴퓨터 시스템의 처리 속도를 감안하여 70*70 으로 하였다.

Teijin사의 HT100-B60의 폴리카보네이트(polycarbonate) $100{\mu}m$, I-Component사의 PES(polyethersulfone) $200{\mu}m$, Ferrania사의 PAR(polyacrylate) $100{\mu}m$와 $200{\mu}m$를 사용하였다 열팽창계수의 차이로 인해 공정상 기판의 가열과 냉각시 열응력이 발생하여 기판의 크랙발생의 원인이 된다. 이를 최소화하기 위해 모든 공정이 시작하기 전에 pre-annealing을 통해 plastic 기판의 시간별 공정을 실시하였다. plastic film의 annealing time은 0h, 12h, 24, 40h, 50h, 60h, 70h, 80h으로 사간을 달리하여 오븐 안의 진공상태를 조성하여 실험하였다. Thermal evaporator로 Al을 약 170nm 증착하였으며 (주)동진 세미캠의 DTFR-1011s DR LCD용 감광액을 Spin Coating Spread(500rpm/6sec), Spin(3000rpm/20sec)으로 coating하였다.

We have investigated electro-optical characteristics in three kinds of TN cells on the polyimide surface. Transmittance of no thermal stressed TN cells were better than that of thermal stressed TN cells. Also. the threshold voltage and the response time of thermal stressed TN cells were same that of no thermal stressed TN cells. There were little change of value in these TN cells. On the other hand. transmittances of TN cells on the polyimide surface decreased by increasing thermal stress time. Moreover. the residual DC of the thermal stressed TN cells on the polyimide surface showed the characteristics of thermal stressed TN cells were weakened as increasing thermal stress temperature and time. Therefore. thermal stability of TN cells were decreased gradually by giving high thermal stress for a long time.

In this paper, we have improved a novel fast response time liquid crystal operating mode using tilt angle in the unique condition by hot-plate equipment. The new control of tilt angle for nematic liquid crystal (NLC) with negative and positive dielectric anisotropy on the rubbed homeotropic polyimide (PI) using baking method by Hot-plate equipment was investigated. LC tilt angle decreased with increasing baking temperature and time. Especially, the low LC tilt angle of positive type NLC (${\Delta}n$>0) on the rubbed homeotropic PI surface by increasing temperature and time was measured. The EO characteristics of the high tilted OCB(HTOCB) mode using control of tilt angle on the homeotropic surface than that of conventional OCB cell can be improved. We suggest that the developed the HTOCB cell using control of tilt angle on the homeotropic surface is a promising technique for the achievement of a fast response time and a high contrast ratio.

We synthesized the two types of photoalignment material of high thermal resistance with hydroxyl aromatic polyimide, and studied the liquid crystal (LC) aligning capabilities on the photopolymer layers. Also, electro-optical (EO) performances for the twisted-nematic (TN)-liquid crystal display (LCD) photoaligned with linearly polarized UV exposure were investigated. A good LC alignment with UV exposure on the two types of photopolymer surface can be obtained. The Voltage-transmittance (V-T) curve in the photoaligned TN cell with UV exposure was different from two type. The response time of photoaligned TN cell was measured about 21 ms in two alkyl chain and about 15ms in four alkyl chain.

We have investigated the EO characteristics generation of pretilt angle for a nematic liquid crystal (NLC) alignment with photoalignment method on three kinds of photopolymer surfaces using polymer substrates. The LC homogeneous alignment were observed on the PMI3CA (N-(phenyl)maleimide with 3-carbon chain cinnamoyl group) and PMIF (N-(phenyl)maleimide including fluoro cinnamoyl group). However, the homeotropic alignment on the PMI5CA(N-(phenyl)maleimide with 5-carbon chain cinnamoyl group) was obtained. Also, EO characteristics of the flexible photoaligned TN-LCD using PMIF surface are better than that of the flexible TN-LCD using PMI3CA surface. Also, the stable EO performances of flexible photoaligned VA-LCD using the PMI5CA surface was observed.

유기발광소자의 발광층의 두께에 따른 임피던스의 변화를 살펴보았다. 임피던스는 두께에 따라 저항의 변화에 따른 의존성을 보이며, 그에 따른 임피던스와 Cole-Cole 반원의 변화, 두께에 따른 $1/\tau$ 의 변화를 살펴보았다. 발광층의 두께는 각각 100, 200, 300 nm의 두께로 열증착하여 실험하였고, 소자의 구조는 $ITO/Alq_3/Al$의 구조로 측정 하였다. 유기발광소자의 발광층인 $Alq_3$의 두께가 증가함에 따라 임피던스의 크기가 증가하고, 위상각의 크기는 100nm의 경우 0V에서 용량성을 보이다가 6~10V까지 부성저항특성을 나타낸 후 약 22V에서 저항성을 나타내고, 200과 300 nm의 경우 12V까지 용량성을 나타내다 이후 22V 근방에서 $0^{\circ}$에 가까워지며 저항성을 나타내는 것을 알 수 있었다. 또한 두께에 따른 Cole-Cole 반원을 살펴보면 두께가 증가할수록 반원의 크기가 증가하는 것을 알 수 있으며, 이를 통해 간단한 등가회로를 예측할 수 있었다. 그리고 벌크내의 용량성$(C_p)$을 측정하여 두께의 증가에 따라 $C_p$ 값이 감소하는 것을 알 수 있었다.

We have studied conduction mechanism that is interpreted in terms of space charge limited current (SCLC) region and tunneling region. The OLEDs are based on the molecular compounds, N,N'-diphenyl-N,N'-bis(3-methylphenyl)-1,1'-biphenyl-4,4'-diamine (TPD) as a hole transport, tris (8-hydroxyquinolinoline) aluminum(III) $(Alq_3)$ as an electron injection and transport and emitting layer. We manufactured reference structure that has in $ITO/TPD/Alq_3/Al$. Buffer layer effects were compared to reference structure. And we have analyzed out electrical conduction mechanism in $ITO/Alq_3/Al$ device with various temperature.