한국정보디스플레이학회:학술대회논문집
The Korean Infomation Display Society (KIDS)
- Annual
Domain
- Electricity/Electronics > Display
2000.01a
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We have developed a high performance vertical alignment TFT-LCD, that shows a high light transmittance, and wide viewing angle characteristics with an unusually high contrast ratio. In order to optimize the electro-optical properties we have studied the effect of cell parameters, multi-domain structure and retardation film compensation. With the optimized cell parameters and process conditions, we have achieved a 24" wide UXGA TFT-LCD monitor (16:10 aspect ratio 1920X1200) showing a contrast ratio over 500:1, panel transmittance near 4.5%, response time near 27 ms, and viewing angle higher than 80 degree in all directions.
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Fringe-field switching (FFS) technology exhibiting a high image quality has been developed. In this paper, one pixel concept, manufacturing process, materials, and electro-optic characteristics of FFS mode comparing with conventional in-plane switching mode, and its possible application to reflective type will be discussed.
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We compared various LCD modes for wide viewing angle. These modes can be classified as film-compensation, multi-domain, IPS. So far, IPS and multi-domain VA represent best performance. The performance gap with respect to CRT is diminishing.
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The wide viewing angle and fast response time characteristics of negative dielectric anisotropy nematic liquid crystal (NLC) using a novel vertical-alignment (VA) - 1/4
${\pi}$ cell mode on a homeotropic alignment layer were investigated. Good voltage-transmittance curves and low driving voltage using the novel VA - 1/4${\pi}$ cell mode without a negative compensation film were obtained. The iso-viewing angle characteristics of NLC using the novel VA - 1/4${\pi}$ cell mode without a negative compensation film can be achieved. The fast response time of 24.4 ms in NLC was successfully measured. The iso-viewing angle, fast response time, and low driving voltage characteristics using the novel VA - 1/4${\pi}$ cell mode can be achieved. -
An 18.1" Thin Film Transistor Liquid Crystal Display (TFT LCD) monitor adopting high brightness In Plane Switching (IPS) technology was realized. While conventional IPS structure used a Chromium (Cr) and Molybdenum (Mo) for a drain electrode, Indium Tin Oxide (ITO) was proposed and verified in this paper. Black sticky micropeal spacers were introduced for the reduction of light scattering phenomena, which was observed at dark room with the conventional micropeal spacers. With the proposed method, more than 10 % aperture ratio was increased and the excellent image quality was obtained.
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21.6" a-Si:H TFT array for direct conversion X-ray detector with 2480 by 3072 pixel is successfully developed. To obtain good X-ray image quality, novel structure, storage on BCB structure, is proposed. The structure reduces the parasitic capacitance of data line, one of the main sources of signal noise. Also, the structure shows higher failure resistance against defects than that of the old design.
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The gate bias stress effect of the hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs) with a
$SiN_x/BCB$ gate insulator have been studied. The gate planarization was carried out by spin-coating of BCB (benzocyclobutene) on Cr gates. The BCB exhibits charge trappings during a high gate bias, but the stability of the TFT is the same as conventional one when it is between -25 V and +25 V. The charge trap density in the BCB increases with its thickness. -
A low-power source driver for TFT-LCDs has been proposed using the triple charge sharing method that enhances the AC power saving efficiency of the prior charge sharing method. The AC power saving efficiency of the proposed source driver reaches 66.6%. In addition, a novel OP-AMP with low-quiescent current has been developed. The measured quiescent current of the OP-AMP is
$5{\mu}A{\sim}7{\mu}A$ at VDD=5V and VSS=0V with load resistance of$2k{\Omega}$ and load capacitance of 300pF. -
We have developed the 12.1" SVGA reflective type color TFT-LCD(Thin Film Transistor - Liquid Crystal Display) with the high aperture ratio and well designed reflector for the applications such as mini note PC, Note PC and electronic book. The panel shows the high reflectance(30%) and contrast ratio(20:1) resulted from optimizing the optical films and designing the embossing shaped reflector. By improving the chromacity, the color reproducibility was increased up to 20%. As removing the backlight unit, we reduced the power consumption, thickness and weight of the panel to 0.8W, 2.2mm, and 250gram, respectively. According to the above performances, we have obtained fabrication process for mass production, and furthermore, could have access to fast market launching.
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Laser diagnostic method in a plasma display discharge cell was introduced. The information of electric field, potential and electron temperature et al. in the surface of plasma display panel can be measured using laser induced fluorescence spectroscopy. However, because of the very small discharge dimension of
${\sim}$ 100${\mu}m$ , the measurement attempt has almost not been performed. In this paper, the direct measurement possibility of the parameters and the recent work of electric field measurement are demonstrated in the plasma display panel. -
Kim, Jae-Sung;Jeon, Chung-Huan;Lee, Eun-Cheol;Ahn, Young-Joon;Kang, Seok-Dong;Ahn, Sung-Yong;Shin, Young-Kyo;Ryu, Jae-Hwa 23
A new PDP cell structure called CSP (Charge Storage Pad) improves the luminous efficiency by 1.6 times and prevents cross talk between adjacent cells. The CSP, which is a conducting material, is inserted between the dielectric layer and the MgO film in the front plate. This CSP produces a longer time-averaged discharge path to get a high luminous efficiency and confines the discharge to prevent cross talk. -
This paper deals with the effect of the thickness of R,G and B phosphor on the electrical and optical characteristics in the reflective type AC PDP. By analyzing various parameters, such as addressing voltage, surface discharge voltage, luminance and luminous efficiency, the optimum value of the phosphor thickness is 50
${\mu}m$ under the condition of 150${\mu}m$ barrier rib height. -
We examined (
$He_x-Ne_{l-x}$ )-Xe gas discharge in an AC PDP cell by computer simulation to understand the gas mixing effects. The breakdown and sustain voltage were significantly lowered with the addition of Ne into He-Xe. The luminance and efficiency in ($He_x-Ne_{l-x}$ )-Xe also improved when compared with the He-Xe or Ne-Xe gas mixture. The luminance is maximum around$30{\sim}40%$ He addition, while the efficiency shows peak values at 70% He. Two-dimensional numerical simulation was done to explain these results. -
CaS:Pb thin film used as phosphor layer in electroluminescent devices were deposited by an atomic layer deposition (ALD). The photoluminescence emission and excitation spectra were measured at 5 and 300K for the
$CaS:Pb^{2+}$ phosphors with different Pb concentration from 0.001 at.% to 0.648 at.%. The emission spectra of these samples were characterized as UV emission and blue emission with the center of peak around 360 and 425nm, respectively. The UV emission was dominant at the low$Pb^{2+}$ concentration of 0.001 at%, whereas with increase of Pb concentration, the blue emission became a major component and to longer wavelength. -
$Zn_2SiO_4:Mn$ phosphors have been recently spotlighted as a green component for plasma TV application. Commercial phosphors such as P1 and P39 have been known to be a very efficient green light emitter for lamp and CRT application. Unfortunately, such commercial phosphors are not suitable for the plasma TV application as both the emission intensity and the decay time do not meet the requirement for plasma TV. The present investigation aims at improving the existing$Zn_2SiO_4:Mn$ phosphors for the purpose of adapting them to PDP application. -
The effect of
$Y^{3+}$ addition to$SrTiO_3:Pr^{3+}$ on the photoluminescence and cathodoluminescence was studied. We discovered that light emitting levels of$Pr^{3+}$ vary by addition of$Y^{3+}$ . In$(Sr_{1-x}Y_x)TiO_3:Pr^{3+}$ , both the green and red emission are discovered while the red emission prevails in$Sr(Ti_{1-x}Y_x)O_3:Pr^{3+}$ .$Sr(Ti_{1-x}Y_x)O_3:Pr^{3+}$ shows enhancement of red emission by two kinds of enhancement process. -
The luminescence behaviors of Yttrium niobate and Bi doped Yttrium niobate were investigated under UV and low voltage electron excitations and interpreted with the first-principle calculations. In the UV excitation and emission spectra of
$YNbO_4$ and$YNbO_4:Bi$ , we were able to separate host contribution and Bi contribution and found that the shift in emission peak to longer wavelength is mainly due to Bi contribution. Using density functional theory, the cluster calculations were carried out for both$YNbO_4$ and$YNbO_4:Bi$ . From the calculated density of states, we were also able to explain the charge transfer gap in the host and the effect of Bi in the excitation and emission spectra theoretically. -
The ZnS:Tb thin-film electroluminescent devices were grown by atomic layer deposition with utilizing single-layer aluminum oxide and/or multilayered tantalum aluminum oxide,
$Ta_xAl_yO$ , as upper and lower insulating layers. These devices were investigated in terms of the luminescent and electrical characteristics. From this analysis, the devices using the$Ta_xAl_yO$ instead of$Al_2O_3$ were observed to have a lower threshold voltage for emission due to the higher relative dielectric constant of$Ta_xAl_yO$ insulators than that of the$Al_2O_3$ device. And there was a large amount of dynamic space charge generation in the phosphor of the device with the$Ta_xAl_yO$ insulators seemingly due to electron multiplication such as trap ionization. -
STN LCDs on Plastic Film substrates for mobile communication devices have been researched and developed at KETI in KOREA. The Plastic Film substrate is so weak to heat and pressure that its fabrication process is limited to
$110^{\circ}C(Tg)$ . In order to maintain uniform pressure on Plastic Film substrate we used newly designed jig and fabrication process. Electro-optical characteristics are better than or equivalent to those of typical glass LCD though it is thinner, lighter-weight, and more robust than glass LCD. -
Photosensitive polyimides containing cinnamoyl and coumarin side groups were synthesized in a high molecular weight, giving a good quality of films. Nematic liquid-crystal (LC) molecules on the film were aligned along the direction with an angle of
$97-99^{\circ}$ respect to the polarization of ultraviolet (UV) light. The LC alignment was induced mainly by the photoaligned polymer chains made by the first UV-exposure even though the film was treated by multiple exposures with changing the polarization of UV light. From these results, it is concluded that the LC alignment on the film is induced by the photodimerization rather than the trans-cis photoisomerization. -
The fringe-field switching (FFS) display is known to exhibit wide-viewing-angle and high transmittance. We have simulated pretilt effects on electro-optic characteristic of the device when a liquid crystal with positive and negative dielectric anisotropy is used. The results show that asymmetry in contour of luminance and light leakage in the dark state are increased but voltage-dependent transmittance curves remain about the same, as the pretilt angle increases to
$10^{\circ}$ . -
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Parameters of a biaxial compensation film and a liquid crystal cell for the optically compensated bend mode LCD with wide viewing angle were optimized. For practical approach, we calculated the optical refractive indices of a retardation film when thickness of a retardation film was fixed at 50
${\mu}m$ . Furthermore, we also optimized optical parameters of LC cell when parameters of a retardation film were different with designed values, because the biaxial compensation film with exact designed values was very difficult to fabricate. In experiments, we achieved the wide viewing angle of over the${\pm}$ 60 degrees by using a biaxial compensation film with a practical thickness value. -
5.2" microtip field emission displays (FEDs) with high voltage applications are fabricated. Nano-structural analysis on microtips is performed for the reliable operation of FEDs. Chemical compositions on the apex of microtips are fully analyzed. A charging mechanism on spacers is simulated and experimentally confirmed with micro-images. A gas-aging mechanism is also studied with integration step of FEDs. The brightness of more than 300
$cd/m^2$ is achieved. In addition, as a new concept, 9" color carbon nanotube FEDs (CNT-FEDs) are introduced using well-aligned carbon nanotubes on glass substrates by paste squeeze and surface treatment techniques. A number of carbon nanotubes,$5-10/{\mu}m2$ , are uniformly distributed over a large area. The turn-on fields of 1$V/{\mu}m$ and field emission currents of 1.5 mA at 3$V/{\mu}m$ are acquired. Different mechanisms between microtip FEDs and CNT-FEDs are discussed. -
Choi, W.B.;Lee, N.S.;Chung, D.S.;Kang, J.H.;Kim, H.Y.;Chang, H.R.;Hong, S.S.;Han, I.T.;Park, S.H.;Yun, M.J.;Kim, J.M. 51
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Measurements of the direct current resistivity, on multiwalled carbon nanotubes(MWNT) for field electron emitter source that had been screen printed in a thick film form were made as a function of temperature T in the range of 1.7K-390K. In this measuring temperature range, the electrical resistivity for the MWNT show that the main contribution to the conductivity comes form carries that hop directly between localized states executing variable range hopping processes. This thick-film form system for large area display showed a high bright light emission as well as very low turn-on field as like an individual MWNT system at room temperature. Furthermore, the electron emission characteristics followed well typical Fowler-Nordheim conduction under the vacuum.
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We report the fabrication of carbon nanostureture films with excellent electron-emission characteristics on chrome electrodes using a pre-deposited transition metal catalyst layer. The emission current densities of 1
${\mu}A/cm^2$ and 1$mA/cm^2$ were measured at the electric field of 2.5 and 4.8$V/{\mu}m$ , respectively, and the current fluctuation of less than 2.5% was observed at the average current density 211${\mu}A/cm^2$ for the measurement duration of 20 minutes. We counted more than${\sim}10^4$ emission sites per$cm^2$ from the emission images, and also noticed good mechanical stability. Moreover, we were able to fabricate good electron-emitting carbon films on chrome electrodes on Corning glass substrates at the nominal temperature below$650^{\circ}C$ . -
Lee, Cheol-Jin;Park, Jung-Hoon;Son, Kwon-Hee;Kim, Dae-Woon;Lee, Tae-Jae;Lyu, Seung-Chul;Kang, Seung-Youl;Lee, Jin-Ho;Park, Hyun-Ki;Lee, Chan-Jae;You, Jong-Hun 57
we have grown vertically aligned carbon nanotubes on a large area of Co-Ni codeposited Si substrates by thermal chemical vapor deposition using$C_2H_2$ gas. The carbon nanotubes grown by the thermal chemical vapor deposition are multi-wall structure, and the wall suface of nanotubes is covered with defective carbons or carbonaceous particles. The carbon nanotubes range from 50 to 120 nm in diameter and about 130${\mu}m$ in length at$950\;^{\circ}C$ . Steric hindrance between nanotubes at an initial stage of the growth forces nanotubes to align vertically. The turn-on voltage was about 0.8$V/{\mu}m$ with a current density of 0.1${\mu}A/cm^2$ and emission current reveals the Fowler-Nordheim mode. -
We have developed the LCD Simulator, which is called "ProLCD", in order to reduce time and efforts for the design and analysis of LCDs. We describe the numerical models implementing the computation of LC directors and electro-optics, the graphic user interface and the visualization modules. Many applications show that ProLCD is a very useful, interactive design tool with good reliability.
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We have studied the molecular orientation by the phase transitions of the chiral smectic liquid crystals, 4-(1-Trifluoromethyl-6-ethoxy-hexyloxycarbonlphenyl)-4-nonyloxybiphenyl-4-carbo-xylate (R-TFMEOHPNBC) to seek the original solution of the zig-zag defect using two different experimental techniques; optical system and x-ray scattering. The phase sequence is gamma ferroelectric
$(SmC{\gamma}\;^*)$ ${\rightarrow}$ smectic A (SmA)${\rightarrow}$ isotropic (I). Existence of two layer spacing at chiral smectic phase gives a possibility of the molecular orientation in two different tilt angles,${\theta}\;_1$ and${\theta}\;_2$ , which are separated each other to the layer normal at a given temperature. The gamma ferroelectric-like phase is, first, discovered in the single compound. -
The low-temperature Si oxidation kinetics by inductively coupled oxygen plasma has been studied. Linear rate constants had negative values when the oxide growth rate was described by linear-parabolic growth law. The analysis of transverse-optical mode frequencies and etch rates indicated that the density of surface oxide was lower than that of bulk oxide. The oxidation kinetics could be explained qualitatively by assuming a surface layer with larger diffusion coefficient and a bulk layer with smaller diffusion coefficient.
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Various fluoride films on a glass substrate were prepared and characterized to provide a seed layer for crystalline Si film growth. The XRD analysis on
$CaF_2/glass$ illustrated (220) preferential orientation and showed lattice mismatch less than 5 % with Si. We achieved a fluoride film with breakdown electric field of 1.27 MV/cm, leakage current density about$10^{-6}$ $A/cm^2$ , and relative dielectric constant less than 5.6. This paper demonstrates microcrystalline silicon$({\mu}c-Si)$ film growth by using a$CaF_2/glass$ substrate. The${\mu}c-Si$ films exhibited crystallization in (111) and (220) planes, grain size of$700\;{\AA}$ , crystalline volume fraction over 65 %, dark- and photo-conductivity ratio of 124, activation energy of 0.49 eV, and dark conductivity less than$4{\times}10^{-7}$ S/cm. -
Polycrystalline silicon (poly-Si) thin film transistors (TFT's) employing vertical amorphous silicon (a-Si) offsets have been fabricated without additional photolithography processes. The a-Si offset has been formed utilizing the poly-Si grain growth blocking effect by thin native oxide film during the excimer laser recrystallization of a-Si. The ON current degradation of the new device after 4 hour's electrical stress was reduced by 5 times compared with conventional poly-Si TFT's.
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There are currently considerable interest in the applications of conjugated polymers, oligomers, and small molecules for thin-film electronic devices. Organic materials have potential advantages to be utilized as semiconductors in field-effect transistors and light-emitting diodes. In this study, pentacene thin-film transistors (TFTs) were fabricated on glass substrate. Aluminums were used for gate electrodes. Silicon dioxide was deposited as a gate insulator by PECVD and patterned by reactive ion etching (R.I.E). Gold was used for the electrodes of source and drain. The active semiconductor pentacene layer was thermally evaporated in vacuum at a pressure of about
$10^{-8}$ Torr and a deposition rate$0.3{\AA}/s$ . The fabricated devices exhibited the field-effect mobility as large as 0.07$cm^2/V.s$ and on/off current ratio as larger than$10^7$ . -
The design of large area thin film transistor liquid crystal displays (TFT-LCDs) requires consideration of cross-talks between the data lines and pixel electrodes. These limits are imposed by the mutual coupling capacitances present in a pixel. The mutual coupling capacitance causes a pixel voltage error. In this study, semi-empirical model, which is adopted from VLSI interconnection capacitance calculations, is used to calculate mutual coupling capacitances. With calculated mutual coupling capacitances and arbitrary given image pattern, the root mean square (RMS) voltage of pixel is calculated to see vertical cross-talk from the first to the last column. The information obtained this study can be utilized to design the larger area and finer image quality panel.
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In recent years, attempts have been made to greatly improve the display quality of active-matrix liquid crystal display devices, and many techniques have been proposed to solve such problems as gate signal delay, feed-through voltage and image sticking[1-3]. To improve these problems which are caused by the feed-through voltage, we have evaluated new driving methods to reduce the feed-through voltage. Two level gate-pulse was used for the gate driving of the cst-on-common structure pixels. These gate driving methods offer better feed-through characteristics than conventional simple gate pulse. Optimized step signal will compensate by step pulse time and voltage. The evaluation of the suggested driving methods were performed by using a TFT-LCD array simulator PDAST which can simulate the gate, data and pixel voltages of a certain pixel at any time and at any location on a TFT array. The effect of the new driving method was effectively analyzed.
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Tone reproduction characteristics of color and gray have a great influence on the picture quality in visual display. In this study, we optimized tone reproduction characteristics of color and gray of CRT monitor by setting brightness to the optimum level, in which offsets for RGB channels can be assumed to zero. The optimum brightness level could be found by measuring a few tones of neutral for the combination of 2 levels of brightness and 2 levels of contrast. As the result, the relationship between normalized DAC count and normalized luminance of primary color or gray has been simply presented by gamma and result in good phosphor constancy.
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We verified the charged static electricity on LCD glass influences upon the etching uniformity of dry etching process by plasma. In the TFT-LCD manufacturing process, we mainly paid attention to eliminate the static electricity for TFT reliability. The static electricity caused the serious ununiformity of etching surface profile and etching rate in the dry etch process. Through our experiment on the made static electricity from -200V to -1000V, it was confirmed that the static electricity on LCD glass caused the etching rate variation of
$1.5%{\sim}15%$ . We recommend the etching process equipment for LCD manufacturing have to establish the soft X-ray exposure module system for eliminating the static electricity inside the loading and unloading chamber. -
General stereo vision system shows things in 3D, using two visions of left and right side. When the viewpoints of left/right sides are not in accord with each other, it gives fatigue to human eyes and prevents them from having the 3-D feeling. Also, it would be difficult to track mobile objects that are not in the middle of a screen. Therefore, the object tracking function of stereo vision system is to control tracking objects to always be in the middle of a screen while controlling convergence angles of mobile objects in the input image of the left/right cameras. In this paper, object-tracker in stereo vision system is presented which would track mobile objects by using block matching algorithm of preprocessing and JTC.
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Tin-doped indium oxide(ITO) thin films were deposited on polyethylene terephthalate(PET) at room temperature by oxygen ion beam assisted evaporator system and the effects of oxygen gas flow rate on the properties of room temperature ITO thin films were investigated. Plasma characteristics of the ion gun such as oxygen ions and atomic oxygen radicals as a function of oxygen flow rate were investigated using optical emission spectroscopy(OES). Faraday cup also used to measure oxygen ion density. The increase of oxygen flow rate to the ion gun generally increase the optical transmittance of the deposited ITO up to 6sccm of
$O_2$ and the further increase of oxygen flow rate appears to saturate the optical transmittance. In the case of electrical property, the resistivity showed a minimum at 6 sccm of$O_2$ with the increase of oxygen flow rate. Therefore, the improved ITO properties at 6 sccm of$O_2$ appear to be more related to the incorporation of low energy oxygen radicals to deposited ITO film rather than the irradiation of high energy oxygen ions to the substrate. At an optimal deposition condition, ITO thin films deposited on PET substrates showed the resistivity of$6.6{\times}10^{-4}$ ${\Omega}$ cm and optical transmittance of above 90%. -
In this study, high-density plasma etching characteristics of ITO(indium tin oxide) films used for transparent electrodes in display devices have been investigated. The etch characteristics of ITO as a function of
$Ar/CH_4$ gas mixtures were analyzed using QMS(quadrupole mass spectrometry), OES(optical emission spectroscopy), and ESP(electrostatic probe). ITO etch rates were increased with the addition of moderate amount of$CH_4$ to Ar due to the increased chemical reaction between$CH_3$ or H and ITO in addition to the physical sputtering of ITO by Ar ion bombardment. However, the addition of excess amount of$CH_4$ decreased the ITO etch rates possibly due to the increased polymer formation on the ITO surface. Also, the measurement data obtained by QMS and OES suggested that$CH_3$ radicals are more activity involved in the etching of ITO compared to H radicals. -
A new technology realizing interconnection between Plastic Film LCDs panel and a driving circuit was developed under the processing condition of low temperature and pressure with ACFs developed for Plastic Film LCDs. The conduction failure of interconnection of the two resulted from elasticity, low thermal resistance and high thermal expansion of plastic substrates. Conductive particles with elasticity similar to the plastic substrate did not damaged a ITO electrode on plastic substrates, and low temperature and pressure process also did not deform the surface of plastic substrates. As a result highly reliable interconnection with minimum contact resistance was accomplished.
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A high power inverter with 300:1 dimming capability for high luminance, one cell, Osram Planon type, plasma light source for LCD Backlight was designed and tested. It was possible to achieve 300:1 dimming control
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In this work, we proposed a reflective antiferroelectric liquid crystal display (AFLCD) using a half-wave cell whose tilt angle is
$22.5^{\circ}$ . To check the validity of our design, we fabricated a reflective half-wave AFLC cell of which tilt angle is$24.9^{\circ}$ , and measured viewing angle dependent reflectance and VIS reflection spectra. In the results, the half-wave AFLC cell in the reflective configuration exhibits high brightness, high contrast ratio of 20:1. -
The effect of
$Al_2O_3$ on the dielectric constant and the coefficient of thermal expansion of lead borosilicate glasses for the application of PDP glass paste was investigated. Measurements were made theoretically by using empirical equations on the composition of the of glasses in which the$PbO/Al_2O_3$ ,$B_2O_3/Al_2O_3$ and$SiO_2/Al_2O_3$ ratios were systematically varied. As a result, with increasing$PbO/Al_2O_3$ the thermal expansion coefficient and the dielectric constant noticeably increased, while the change of$B_2O_3/Al_2O_3$ and$SiO_2/Al_2O_3$ ratios did not affect those properties of the glasses. -
This paper deals with the relationship between the addressing and the display in ac-PDP. Especially, deals with the transfer probability of surface discharge according to addressing voltage (Va), blocking voltage(Vg) in addressing period and the characteristics of luminance according to sustain voltage(Vs) in sustaining period with ADS(Address Display period Separation) driving method.
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We measured 3-dimensional images of the light emitted from plasma display panel by using newly proposed scanned point detecting method (SPDM). From the 3-dimensional emission images, we know that as the sustain voltage increases, intensity of light detected without phosphor increases and the position of the maximum intensity moves to the outside from the electrode gap. Also, we know that 2-dimensional simulations under the assumption that neglects the Y axis variation do not agree with 3-dimensional experiment results.
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The performance of ac plasma display panels (PDP) is influenced strongly by the surface glow discharge characteristics on the MgO thin films. This paper deals with the surface glow discharge characteristics and some physical properties of MgO thin films prepared by reactive RF planar unbalanced magnetron sputtering in connection with ac PDP. The samples prepared with the de bias voltage of -10V showed lower discharge voltage, lower erosion rate by ion bombardment, higher optic transparency and higher crack resistance in annealing process than those samples prepared by conventional magnetron sputtering or E-beam evaporation.
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Voltage transfer curves have been used for analyzing the micro-discharge characteristics of cells in ac-PDP. This paper deals with the effect of working gas species, pressure and frequency of applied voltage on the micro-discharge characteristics. Using the mixture gases of He+Xe or He+Ne+Xe, wall voltage steeply varied compared with only He gas, and also voltage margin increased. Discharge voltage and voltage margin increased with increasing Xe percentage, and also wall voltage more steeply varied. In addition, the variation of effective wall capacitance which is significantly dependent on the discharge strength is discussed.
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The positive slope of the current-voltage characteristic at pressure up to 850 torr was obtained using the closed microhollow cathode without the individual and/or distributed ballast. This indicates that the stable parallel operation of the discharge was also achieved using the closed microhollow cathode. The parallel operation makes it possible to manufacture de plasma displays with high pressure, small discharge current, and long lifetime.
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We propose the method which is possible to fabricate the electrodes with the fine pattern and low resistance by photolithography and electroplating. The widths of pattern fabricated were 30, 50, 70 and 100um and the thickness could be up to
$10{\mu}m$ . The resistivity of the copper electrode electroplated was below$2.0{\mu}{\Omega}$ cm which is about half of photosensitive silver electrode. Dielectric layer was coated on the electrodes by screen printing and the pores harmful to the discharge were not formed after heat treatment. In the viewpoint of resistance and patterning, this method has much higher potential for large area display than other methods like screen printing, photosensitive conductive paste method and sputtering. -
Sputtering yield of MgO film in the AC-PDPs has been calculated by Monte Carlo simulation of ion scattering. In the ion energy range less than 50 eV, the sputtering yield is 4
${\times}$ $10^{-4}$ for Xe ions and it is between 0.1 and 0.01 for He, Ne, and Ar ions. The erosion rate is estimated about$25{\AA}$ per hour for Xe ions in an actual PDP plasma for sustain and full white mode. -
The breakdown characteristics of surface discharge investigated experimentally agree well with the analytic results of previous reports [1-3] in various electrode geometries. Additionally, we find that the electrode geometry effects on the firing voltage can be understood with the ionization probability relating to the number of priming particles. We have also observed the shape of surface discharge and the surface striations in the gap geometry with the pressure, the applied voltage, and the driving frequency.
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Jeoung, J.M.;Leem, J.Y.;Cho, T.S.;Choi, M.C.;Ahn, J.C.;Kim, J.G.;Kim, Y.G.;Cho, D.S.;Kim, S.S.;Kim, T.Y.;Choi, S.H.;Chong, M.W.;Ko, J.J.;Kim, D.I.;Lee, C.W.;Kang, S.O.;Cho, G.S.;Choi, E.H. 113
The secondary electron emission coefficient(${\gamma}$ ) of vacuum annealed MgO films has been investigated by${\gamma}-focused$ ion beam(${\gamma}-FIB$ ) system. The vacuum annealed MgO films have been found to have higher${\gamma}$ values from 0.053 up to 0.121 than those for as-deposited MgO films from 0.026 up to 0.062 for$Ne^+$ ion energies ranged from 50eV to 200eV. Also it is found that${\gamma}$ for air hold of vacuum annealed MgO layers for 24-hours is similar to that for vacuum annealed MgO films without any air-hold. -
Cho, T.S.;Kim, T.Y.;Kim, S.S.;Cho, D.S.;Kim, J.G.;Ahn, J.C.;Jung, Y.H.;Lim, J.Y.;Jung, J.M.;Ko, J.J.;Kim, D.I.;Lee, C.W.;Seo, Y.;Cho, G.S.;Choi, E.H. 115
Influence of sustain pulse-width on electro-luminous efficiency is experimentally investigated for surface discharge of AC-PDP. It is found that the firing voltage is decreased as the pulse-width is increased from$2\;{\mu}s$ to$8\;{\mu}s$ with sweeping frequency range of 10 kHz to 50 kHz. It has been found that the optimal sustain pulse-width is in the range of$3{\sim}4\;{\mu}s$ under driving frequency range of 30 kHz and 50 kHz, based on observations of memory coefficient, wall charge, and wall voltage as well as luminous efficiency. -
Lim, J.Y.;Jung, J.M.;Kim, Y.G.;Ahn, J.C.;Cho, T.S.;Cho, D.S.;Kim, J.G.;Kim, T.Y.;Kim, S.S.;Jung, M.W.;Choi, S.H.;Ko, J.J.;Kim, D.I.;Lee, C.W.;Seo, Y.;Cho, G.S.;Kang, S.O.;Choi, E.H. 117
The secondary electron emission coefficient${\gamma}$ of MgO single crystals according to the gas mixture ratio of Xe to Ne have been investigated by${\gamma}-focused$ ion beam system. It is found that the MgO single crystals of (111) crystallinity has the highest${\gamma}$ from 0.09(0.03) up to 0.16(0.04), while from 0.07(0.02) to 0.15(0.03) for (200) and from 0.06(0.01) to 0.13(0.02) for (220) crystallinity for operating Ne (Xe) ions ranging from 50eV to 200eV throughout this experiment. And it is found that the${\gamma}$ ranged from 0.03 up to 0.06 for Ne-Xe mixtures are much smaller than those of 0.09 up to 0.16 for pure Ne ions under accelerating voltage ranged from 50V to 200V. -
Kim, T.Y.;Cho, T.S.;Kim, S.S.;Cho, D.S.;Kim, J.G.;Ahn, J.C.;Jung, Y.H.;Lim, J.Y.;Jung, J.M.;Ko, J.J.;Kim, D.I.;Lee, C.W.;Seo, Y.;Cho, G.S.;Choi, E.H. 119
Influences of sustain voltage on wall charges and wall voltages are experimentally investigated in surface AC plasma display panels(AC-PDPs), in which electrode gap and width are$80\;{\mu}m$ and$270\;{\mu}m$ , respectively. The filling gas is Ne-Xe gas mixture, and total pressures 300 Torr. Also it is found that the more amount of Xe mixing ratio makes the less wall charge and voltage for sustain voltage ranged from 140 V to 222 V. The response time has been delayed by adding a small amount of Xe to Ne in comparison with that without Xe. It is also found that the wall charge and voltage are reduced by adding a small amount of Xe to Ne in comparison with those without Xe. -
The understanding of reset scheme is essential for the driving of AC PDP (Plasma Display Panel). The characteristics of reset period of AC PDP was examined with the variation of pulse time and voltage in the ADS (Address Display Separated) driving method presented by Fujitsu,. The addressing characteristics showed drastic change as a function of the erasing time and addressing pulse width. In this paper, these results were explained by the change of wall charge variation, and it was estimated with the currents through each electrode.
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Three types of conjugated polymer, poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV), were obtained by Honer-Emmons condensation using potassium tert-butoxide from the synthesized monomers in anhydrous tetrahydrofurane. The Honer-Emmons reaction was found to be a useful synthetic method for the preparing a wide range of EL polymers. The EL devices using poly(DFPZ-AV), poly(MEHPV-PV) and poly(BFMP12-BPV) as light emitting layer gave red, green and blue emission, respectively, which were in close chromaticity with the CIE 1931 NTSC standard.
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We report the use of fluorene based copolymers containing quinoline(POF66, PIF66) and pyridine(PFPV) units as electron transporting polymers for multi-layered LEDs. Double-layer device structure combining PIF66 as electron-transporting layer with the emissive MEHPPV showed a maximum quantum efficiency of 0.03%, which is 30 fold increased compared with ITO/MEHPPV/Al single-layer device. PFPV layer increased the quantum efficiency up to 0.1% in the device structure of ITO/(P-3:PVK)/PFPV/Al. The ETL with the electron deficient moiety improved the LED performance by the characteristics of electron transporting as well as hole blocking between emissive layer and metal cathode.
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Organic light-emitting diodes(OLEDs) are constructed using multilayer organic thin films. The hole-transport layer is PVK and the emitting material is rubrene and
$Alq_3$ . The emitting layer is doped with rubrene partially. As the partially-doped layer migrate from the interface PVK/emitting layer, the emission peak of rubrene decrease and diminish. By comparing with the previous reports, we propose the zero-field hole injection barrier at ITO/PVK interface and hole-trapping effect of rubrene in host materials as predominant factor to determine the emission zone. -
The emission color stability of poly(fluorene) derivatives upon thermal annealing or passage of current in an electroluminescent device is affected by the structure of the main chain polymer unit and particularly by the polymer chain end substituents. Proper attention to these features leads to colorfast blue emission in both photo- and electoluminescence. Furthermore, the spectral emission characteristics can be tuned by the incorporation of various comonomers. Preliminary single layer device studies validate the potential utility of poly(fluorene) homo and copolymers for OLED applications.
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We prepared Si emitters coated with a MOCVD
$CoSi_2$ layer to improve the emission properties. The$CoSi_2$ layer was grown on Si field emitters in situ by reactive chemical-vapor deposition of cyclopentadienyl dicarbonyl cobalt at 600${\sim}$ $650^{\circ}C$ . The$CoSi_2$ coated field emitters showed enhanced emission properties of current-voltage characteristics, which were due to the increase of emitting area from Fowler-Nordheim plot. And the emission current fluctuation decreased due to the chemically stable surface properties of$CoSi_2$ . -
Effect of nitrogen doping on field emission characteristics of patterned Diamond-like Carbon (DLC) films was studied. The patterned DLC films were fabricated by the method reported previously[1]. Nitrogen doping in DLC film was carried out by introducing
$N_2$ gas into the vacuum chamber during deposition. Higher emission current density of$0.3{\sim}0.4$ $mA/cm^2$ was observed for the films with 6 at % N than the undoped films but the emission current density decreased with further increase of N contents. Some changes in CN bonding characteristics with increasing N contents were observed. The CN bonding characteristics which seem to affect the electron emission properties of these films were studied by Raman spectroscopy, x-ray photoemission spectroscopy (XPS) and Fourier transform infrared spectroscopy (FT-IR). The electrical resistivity and the optical band gap measurements showed consistence with the above analyses. -
Field emission mechanism of undoped polycrystalline diamond films with a different amount of nondiamond carbon has been investigated using a transparent anode imaging technique and an electrolytic decoration technique. It is confirmed that for the films with a large amount of nondiamond carbon, electron transport occurs mainly through conductive grain boundaries while for the films with a small amount of nondiamond carbon, electron transports preferentially through diamond surface.
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We synthesized highly aligned carbon nanotubes by thermal decomposition of acetylene gas using metal catalyst island. The alignment technique in this experiment is a very efficient method because it does not require any treatments before and after catalyst metal deposition. Alignment of nanotubes was dominated by the uniform diameter and the high density of metal catalysts. In the field emission test, the uniform emission spots on phosphor screen were obtained from the nanotubes in spite of non-aligned tube nature.
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The origin of the display current in the surface conduction electron emitter displays has been verified in the calculation of the electron trajectory. Some electrons move directly toward the display surface as an anode current which is generated due to the inertial force of electron motion along the curved electric field lines with a small curvature near the fissure area..
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In order to improve electron field emission and its stability, tip surface of amorphous silicon field emitters have been coated with molybdenum layer with a thickness of 25 nm through the gate opening and annealed rapidly in inert ambient. Compared with amorphous silicon field emitters, Mo silicidized amorphous silicon field emitters exhibited lower turn on voltage about 9 V, 3.8 times higher maximum current, 3.1 times lower fluctuation range and less change of the emission current depending on the vacuum level.
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The aerosol pyrolysis technique was introduced to prepare the spherical phosphors for enhancing low-voltage phosphor efficiency. The density, the shape, and the crystallinity of phosphors were controlled by thermal decomposition temperature and phosphor annealing condition. The particle size was adjusted by the precursor concentration and reactor pressure. It was fond that the efficiency of phosphors synthesized in this work was superior to the commercial products at the low-voltage excitation by 1.5 times and the screen efficiency was also higher than that of any value reported in literature.
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Seo, D.S.;Song, B.G.;Kim, C.O.;Hong, J.P.;Jin, Y.W.;Cha, S.N.;Lee, N.S.;Jung, J.E.;Kim, J.M. 145
Primary emphasis was placed on the electrophoretic deposition of low voltage phosphor to indium-tin oxide-coated glass for the application of field emission display. The phosphor deposited by various parameters, such as deposition time and applied voltages was examined in detail. In addition, a comparison was made by analyzing luminance properties of the phosphor mixed with and without conducting$In_2O_3$ powder of less than 1um size. The measurement was performed as a function of$In_2O_3$ concentration from 3% to 15% by weight. The enhanced impact of indium powder mixing on the phosphor was clearly demonstrated by aging performance curve at 1000V excitation voltages with a current density of$1\;mA/cm^2$ -
Sealing of two glass plates composing of FED panel was done in a vacuum chamber. Several factors related with a heating process of a frit glass were investigated, including comparisons with a conventional method.
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Lead-doped calcium sulfide(CaS:Pb) thin film electroluminescent devices were deposited using atomic layer deposition(ALD). CaS:Pb is a very promising blue phosphor showing very high luminance and the color coordinate close to the blue of cathode ray tube. The luminance,
$L_{25}$ , of CaS:Pb(1.6 mol.%) EL device was higher than 80$cd/cm^2$ at a driving frequency of 60Hz. The color coordinates of blue EL emission of CaS:Pb deposited by ALD are consistent with the Pb concentration ranging from approximately 0.5 to 3 mol.%. -
For excimer laser crystallization (ELC), energy density, number of pulses, beam uniformity, and condition of initial amorphous Si (a-Si) films are significant factors contributing the final microstructure and the performance of low-temperature polycrystalline Si TFTs. The process and equipment have been achieved a significant improvement, but still, environmental factors associated with initial amorphous Si (a-Si) films and process conditions need to be optimized.
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Large size poly-Si TFT-LCDs have been fabricated using p-channel thin film transistors for notebook PC application. We have designed and implemented the data sampling circuit and gate drivers that operate with low power consumption and high reliability. The gate driver has a redundant structure. We have realized the uniform and excellent display quality comparable to that of CMOS module. The reliability of panel is investigated and discussed by measuring the bias stability of transistors.
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We propose a new in-situ fluorine passivation of poly-Si TFTs by excimer laser annealing to reduce the trap density and improve the reliability significantly. This improvement is due to the formation of stronger Si-F bonds than Si-H bonds which passivate the trap states.
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In this study, to get the larger drain current of the device under the same operation condition as the conventional gate dielectric SiNx thin film transistor devices, we introduced new gate dielectric
$Ta_2O_5$ thin film which has high dielectric constant$({\sim}25)$ and good electrical reliabilities. For the application for the TFT device, we fabricated the$Ta_2O_5$ gate dielectric TFT on the low-temperature-transformed polycrystalline silicon thin film using the self-aligned implantation processing technology for source/drain and gate doping. The$Ta_2O_5$ gate dielectric TFT showed better electrical performance than SiNx gate dielectric TFT because of the higher dielectric constant. -
A new manufacturing method using laser transfer technology was developed for a color filter of TFT-LCD. This method can make red, green and blue color layer at the same time without several baking processes. Simple process, no residue, good edge profile, and so on are merits of this process. The same performances (such as color characteristics, reliability, hardness and so on) of current color filter were achieved with this process.
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We propose multi-layer aspheric lenticular lens for rear projection screen to provide wide viewing angle. Each pitch of lenticular lens sheet is divided by three region and image light from projection optical system is propagated widely on each region due to different focal point. Besides, to improve vertical viewing angle of screen, we propose glass bead embedded screen on observer side of lenticular lens.
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We discuss the design and fabrication of CCD or C-MOS imaging lenses with hybrid diffractive / refractive optics. The hybrid lenses are made of optical grade plastic materials. We have been able to significantly reduce the number of elements while maintaining very high optical quality. This paper describes the conception, design, fabrication and evaluation of hybrid lenses in comparison with conventional refractive lenses. The new lens has excellent optical quality, very light weight, compact size and low manufacturing cost.
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Spatial independence and temporal stability of flat-panel LCD monitor, LG StudioWorks 500LC, were evaluated. The luminance and chromaticity of stimulus color were measured according to the variation of the size, background color, and location on the screen. The spatial independence at center location is very good and not a limiting factor in its colorimetric characterization, however the spatial non-uniformity is a little severe. The warmup time to stabilize after initial power is about 100 minutes and short-term variance of white stimulus is within 0.1
${\Delta}E^*\;_{ab}$ . -
We propose a signaling circuit that can reduce power consumption and Electromagnetic Interference (EMI) in a Liquid Crystal Display (LCD) controller-to-source driver interface. The proposed signaling circuit consists of a coder/decoder that can minimize temporal bit transitions in a transmission line and a current-mode driver that can convert voltage swing into a very small amount of current. We have simulated the proposed signaling circuit using the HSPICE and the proposed signaling circuit has been designed in a 0.25
${\mu}m$ CMOS technology. -
Choi, J.P.;Jeon, W.G.;Kang, J.;Lim, G.S.;Kim, O.D.;Kim, H.Y.;Song, J.W.;Yoo, E.H.;Park, M.H. 169
The conventional AC PDP has a relatively low efficiency which is close to 1.5 lm/W. If the AC sustain period is replaced by the RF sustain period, due to oscillating and low electric field, almost 60% of the supplied energy is spent by Xe excitation [1]. The efficiency of RF PDP can be$4{\sim}5$ times higher than that of AC PDP. In this paper, we will present the RF PDP that is a new type of PDP. A new display method in PDP using RF pulses is suggested and applied on a 4-inch-diagonal Panel (hereinafter 4" panel). Even though there were many researches in RF discharge, there was not enough research for display application. Now we propose the RF PDP that is a new display field and we will expect to do more research in this field. -
This study uses neon and xenon gas mixture discharges to determine the effects of the neon plasma emission on the characteristics of visible emission from the stimulation of the red, green, blue(RGB) phosphor layers in a surface-type alternate current plasma display panel(AC PDP). With a mixture of less than 2% xenon to neon, it is found that the luminance changes in the visible emission of the phosphor layers are similar to those of the neon plasma emission. In the range of xenon mix ratio from 2 to 5%, the luminance of the red, green, blue(RGB) phosphor layers decreases with a decrease in the neon plasma emission intensity. However, with a mixture of above 5% xenon to neon, the luminance of the red, green, blue(RGB) phosphor layers increases regardless of a decrease in the neon plasma emission intensity. Furthermore, the color purity of the red, green, blue(RGB) phosphor layers improve as the neon plasma emission intensity decreases. Accordingly, it is concluded that the optical properties of the phosphor layers, including color purity and luminance, depend on the neon plasma discharge emission as well as the visible emission from the stimulation of the phosphor layers.
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Electric fields and the wall voltages in a surface-type AC PDP cell were measured using a Laser Induced Fluorescence Spectroscopy. For the condition of He 100Torr, 200V sustain voltage and 50kHz sustain frequency, the wall voltage dropped from about 50V to about -75V within
$1{\mu}sec$ after the main discharge. And the wall voltage decreased with the rate of$10.8V/{\mu}sec$ due to the accumulation of the space charges after$1{\mu}sec$ . But when the operating pressure was 40Torr, it increased with the rate of$4.5V/{\mu}sec$ because the diffusion effect of the wall charge on MgO surface was more dominant than the accumulation effect of the space charges. During the pulse-off period, the wall voltage decreased slightly due to the diffusion of the wall charge. When the sustain voltage was 250V, the self-erasing discharge occurred, and the absolute value of the wall voltage decreased rapidly just after the pulses were off, which was caused by the accumulation of the charges generated by the self-erasing discharge. -
Barrier rib for the plasma display panel (PDP) was made by photolithographic process utilizing photosensitive barrier rib paste. The barrier rib paste was prepared by first dissolving poly(MMA-co-MAA) binder polymer in butyl carbitol(BC) solvent at 15 wt% concentration. To this solution were added a mixture of functional monomers , Irgacure 651 photoinitiator, and barrier rib power and then the whole mixture was dispersed in the three roll mill for 2 hour. The effect of component and concentration of photosensitive barrier rib paste was studied. After optimization of the paste formulation and photolithographic process, barrier rib could be obtained with good resolution up to 110-120
${\mu}m$ height and 80-90${\mu}m$ width. -
The glass compositions of
$PbO-SiO_2-B_2O_3$ system and$P_2O_5-PbO-ZnO$ system for the transparent dielectric materials for front panel and$P_2O_5-ZnO-BaO$ and$SiO_2-ZnO-B_2O_3$ for the reflective dielectric materials for back panel of PDP(Plasma Display Panel) were investigated. As a transparent dielectric materials for front panel,$PbO-SiO_2-B_2O_3$ glass showed good dielectric properties, high transparency and proper thermal expansion matching to soda-lime glass substrate. And the reflective dielectric materials for back panel were prepared from parent glass of$SiO_2-ZnO-B_2O_3$ system and oxide filler. It was found that these glass-ceramics are useful materials for reflective dielectric layers, as those have a similar thermal expansion to soda-lime glass plate, high reflectance, low sintering temperature. -
A new driving circuit for scan electrode in AC PDP has been developed. The number of scan driver switches can be reduced to one half of the conventional circuit. Capacitance between the electrodes is utilized. Experiments and analysis of the new structure has been carried out to confirm its robustness.
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Choi, Seung-Ho;Lee, Soon-Il;Oh, Soo-Ghee;SunWoo, Jin-Ho;Kim, Jae-Gak;Lee, Gol-Hee;Kim, June-Dong 185
For the quantitative investigation of the erosion of MgO layers in real ac-PDP cells, we constructed a microscopic spectrophotometer which is capable of measuring transmission spectra from the area as small as 20${\times}$ 20${\mu}m^2$ . In the test on the sputtered MgO films with a thickness gradient, we were able to probe the thickness variation of 1000 nm over$1000-{\mu}m$ distance. Using this instrument, we were able to determine not only the erosion rate at the particular position of ac-PDP cells but also the relative erosion rate at different positions in a single ac-PDP cell. -
The conventional firing process method for the transparent dielectric layer in PDP Technology has disadvantages of low through put, high power consumption and large process area. We propose the rapid thermal scinterring (RTS) method as new process method to overcome these disadvantage characteristics. As the experimental result of this method, the optic transmittance(wavelength : 600nm) rate of transparent dielectric layer was more improved than conventional furnaces under the optimized gas supplying. Further, it was certified this method had the best conditions on the firing process of the PDP transparent dielectric layer.
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A plasma display panel(PDP) with a new discharge cells are investigated electrically and optically. These cells have the structure of a long discharge path length and a small electrode area. They have shown a higher luminous efficiency and a lower power consumption about
$30{\sim}40%$ improvement than the conventional standard ac PDP cells. -
New copolyimides containing nitrile side group were synthesized from copolymerization of pyromellitic dianhydride, m-phenylene diamine and 3,5-diaminobenzonitrile and subsequent thermal imidization of the resulting poly(amic acid). Crystallinity, glass transition temperature and initial decomposition temperature of copolyimides were almost identical to those of homo polyimide prepared from PMDA and m-PDA. Change of pretilt angle induced by the orientation layer of resulting copolyimide was investigated by using a nitrile-containg nematic liquid crystal cell after rubbing. As the content of polar nitrile group was increased in the copolymer, pretilt angle was increased from
$3.65^{\circ}$ to$6.49^{\circ}$ . The mechanism of this was speculated as the dipolar interaction between the liquid crystal and nitrile groups in copolyimide. -
We have calculated the d/p boundary values in which the low twist defect and the stripe domain defect can occur with dielectric constants and elastic constants and compared them with experimental data using the compensation factors. We estimated d/p margin for
$250^{\circ}$ twist angle without experimental data and investigated qualitatively the reasonability of the behavior. -
Fast response time is realized by using LTN-LCDs. To calculate the dynamic electro-optical characteristics, Ericksen-Leslie theory is used for the dynamic profile of molecules and order tensor representation is adopted for the free energy calculation.
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A surface-assisted photo-control of the liquid crystal (LC) alignment has been achieved by modifying the topmost surface of the polyimide film with photo-reactive molecules. Recently, photo-alignment technique using a thin film of poly(vinyl cinnamates) have been reported. However their commercial potentiality is limited by their low thermal stability. To enhance thermal stability, we synthesized the chalcone derivatives as the photo-reactive molecules and introduced the materials on the surface-modified polyimide film.. We identified that the photo-chemical reaction of the chalcone derivatives occur in few minutes with irradiation of UV light. The photo-alignment characteristics of the modified polyimide films treated by polarized UV light and their LC cells are investigated as a function of exposure dose.
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Measurement of low cell gap and retardation by using a rotating polarizer method was proposed. For more precise calculation and measurement, we applied a retardation film that has large retardation value of
$1\;{\mu}m$ to measurement system. From experiments, we proved that cell gap and retardation could be measured even though the values of those are so small. -
This seminar outlines the technology involved in the backlighting of TFT LCDs. It covers basic terminology, lighting requirements, lamp types and optical techniques. These will be reviewed and compared. Optical factors will be covered and related to space constraints. The spectral requirements, luminance levels, system efficacy, power requirements, lamp temperature, as well as other parameters affecting system performance will be discussed.
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We have developed 14.1" XGA transflective panel for both transmissive mode and reflective mode. We designed new panel structure, optimized optical films and adopted pixel with high aperture and high transmittance color filter. This can be applied for mobile tool and sub-note without regard to environment.
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Kim, Young-Kyoo;Park, Seong-Sik;Jung, Young-Yi;Han, Ki-Jong;Lee, Jae-Gyoung;Hwang, Ha-Keun;Choi, Dong-Kwon;Keum, Ji-Hwan;Im, Woo-Bin;Lee, Hyo-Jung;Lee, Hyung-Sik;Kim, Sun-Wook 205
The capacitance-temperature (C-T) measurement technique is proposed in the present work to investigate the thermal stability of organic and polymeric thin films for organic electroluminescent display (OELD). The single layer devices with the individual materials were subjected to the C-T measurement, prior to the examination of the complete OELD. The single layer devices with the small molecules destroyed below$180\;^{\circ}C$ depending on the kinds of materials. However, the device with the hole-transporting polyimide did not show any relaxation up to$200\;^{\circ}C$ . The small molecule based OELDs failed to emit light after annealing, whereas that with the hole-transporting polyimide worked well in spite of large reduction in intensity. -
The temporal response of the electroluminescence (EL) has been studied in the organic electroluminescent devices fabricated with a vacuum-deposited poly(p-phenylene) (PPP) thin film upon the application of a rectangular driving voltage. The blue EL emission arises with a delay time of several hundred nanoseconds and then saturates with the rise time of less than microsecond. The EL delay time is considered as the transit time of holes in the PPP thin film since the hole mobility is much larger than the electron mobility in PPP. The hole mobility is estimated to be
${\sim}$ $1{\times}10^{-5}$ $cm^2/Vs$ in the vacuum-deposited PPP film. -
Yu, Jae-Woong;Kim, Jai-Kyeong;Cho, Hyun-Nam;Kim, Dong-Young;Song, Nam-Woong;Kim, Dong-Ho;Kim, Chung-Yup 209
The energy transfer from photoexcited polyvinylcarbazole (PVK) chromophores with a bandgap of 3.7 eV as a donor to fluorophores of poly(dihexylfluorenevinylene) (PDHFV) or poly(dihexylfluorenedihexoxyphenylenevinylene) (PDHFHPV) as an acceptor in bilayered specimens should be carried out since the spectral overlap pairs fulfills the requirement for the$F{\ " {o}}rster-type$ condition. However, the energy transfer rate from the chromophores with a wider bandgap to the fluorophores with a narrower bandgap is proved to be strongly dependent on the lifetime ratio between the excitons. -
Organic electroluminescent devices (OELDs) have received a great deal of attention due to their potential application as full-color displays. Europium complexes are known as excellent red light-emitting materials for OELDs since they show intense photoluminescence at around 612 nm with a narrow spectral bandwidth. In this study, a novel europium complex,
$Eu(TTA)_3(TPPO)$ was synthesized and its photoluminescent and electroluminescent characteristics were investigated with a device structure of ITO/TPD/$Eu(TTA)_3(TPPO)$ /$Alq_3$ /Al, where sharp emission at the wavelength of 615 nm has been observed. Details on the electrical properties of these structures was also discussed. -
New light-emitting polyimides were synthesized from the conventional polycondensation of 5,5'-bis(4-aminophenyl)-2,2'bifuryl (PFDA) with fluorinated and non-fluorinated aromatic dianhydrides, providing a good quality of thin films: 6F-PFDA PI and ODPA-PFDA PI. Their UV-visible absorbance and photoluminescent characteristics were investigated. The polymers emit blue and blue-greenish light in a quantum yield of 7.3-14.9%, depending on the polymer backbone.
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Kim, Seong-Hyun;Hwang, Do-Hoon;Park, Heuk;Chu, Hye-Young;Lee, Jeong-Ik;Do, Lee-Mi;Zyung, Tae-Hyoung 215
We fabricated the thin-film transistors using organic semiconductor, pentacene, on$SiN_x$ , gate insulator. X-ray diffraction experiments were performed for the sample after heat-treatments at higher temperatures. We confirmed that we obtained "thin-film phase" from the condition used here. From the electrical measurements, we also confirmed that no charges are accumulated at the interface between organic and insulating layer, and FET characteristics of the organic FET using pentacene was discussed. -
This paper describes a formation of the Mo-silicide on Mo tip to compare the emission characteristics of the Mo tip. Cone-shaped Mo tip arrays were fabricated and silicidized by evaporating a 15nm-thick a-Si film on Mo tip arrays and annealing it in inert ambient at the temperature of
$1000\;^{\circ}C$ for 60 sec. The$Mo_5Si_3$ phase of Mo-silicide was observed through X-ray diffraction (XRD) analysis. Although the gate voltage of the Mo-silicide tip increased by 38 V to obtain the current level of 20 nA/tip, the dependence of emission current on vacuum level was improved. -
Kang, Seung-Youl;Jung, Moon-Youn;Cho, Young-Rae;Song, Yoon-Ho;Lee, Sang-Kyun;Kim, Do-Hyung;Lee, Jin-Ho;Cho, Kyoung-Ik 219
We propose a new method for the formation of an aluminum parting layer in the fabrication of field emitter arrays, in which we used a reflow property of aluminum at a lower temperature than the deformation point of glass. After the sputtered aluminum layer on the gate metal was etched for the formation of gate holes, we carried out a rapid thermal annealing process, by which the aluminum slightly diffused into the gate hole. This reflowed aluminum could be used as a parting layer and emitter arrays were easily fabricated using this method. -
The vibration of a mask degrades the color purity in CRT. In order to reduce the vibration. a damping wire is put into contact with the mask in the Flatron. We analyzed the vibration of the mask considering the damping wire using FEM. The natural frequencies and mode shapes of the mask are calculated by modal analysis. And those are compared with the measured results to confirm our finite element model. The modal analysis of the wire is also performed to investigate resonance with the mask. Finally, the transient dynamic analysis of the mask contacting with the wire is performed. The vibration of the mask is measured to confirm our analysis, and the results are in good agreement with the analysis.
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As technology level of TFT-LCD advances, application to TV becomes an emerging important area for LCD makers. In this paper, we review current LCD technology level to be used in TV such as liquid crystal response behavior, color accuracy, contrast ratio, brightness and panel size. Based on the understanding of current limitations in LCD compared with CRT, the improvement plan to render 'near perfect motion picture' reproduction with LCD is proposed. Digital TV is a great opportunity for digital LCD panels, but we have to solve remaining technical and cost issue in order to be competitive with other large size TV technologies such as PDP, CRT or projection type. In preparing the upcoming digital TV era with advanced TFT-LCD, the hurdles and prospect of larger size LCD-TV panels will be discussed.
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LGE developed and demonstrated the first 60-inch full color AC plasma display panel with the 1365
${\times}$ 768 resolution. Both Sol-gel and E-beam method have been tried for MgO layer, and photolithography has been used for electrodes and phosphor layer to fabricate a 60-inch panel. Selective Erase, Selective Write, Address Display Separate, and Address While Display driving scheme have been tested. Its luminance and contrast ratio is about$550\;cd/m^2$ and 500:1, respectively. -
The current status of OLEDs technology is reviewed. Comparison has been made between small molecule based OLEDs and polymer LEDs. In addition, advantages of OLEDs technology and technical issues for commercialization are addressed. Details of these issues will be discussed at the meeting.
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Choi, Young-Chul;Jeon, Seong-Ran;Park, Young-Soo;Bae, Dong-Jae;Lee, Young-Hee;Lee, Byung-Soo;Park, Gyeong-Su;Choi, Won-Bong;Lee, Nae-Sung;Kim, Jong-Min 231
Vertically aligned carbon nanotubes were synthesized on Ni-coated Si substrates using microwave plasma-enhanced chemical vapor deposition. The grain size of Ni thin films was varied with the RF power density during the RF magnetron sputtering process. It was found that the diameter, growth rate, and density of carbon nanotubes could be controlled systematically by the grain size of Ni thin films. With decreasing the grain size of Ni thin films, the diameter of the nanotubes decreased, whereas the growth rate and density increased. High-resolution transmission electron microscope images clearly demonstrated synthesized nanotubes to be multiwalled. The number of graphitized wall decreased with decreasing the diameter. Field emission properties will be further presented. -
We have performed ab initio pseudopotential electronic structure calculations for various edge geometries of the (n,n) singlewall nanotube with on without applied fields. Among the systems studied, the one with the zigzag edge exposed by a slant out is found to be the most favorable for the emission due to the existence of unpaired dangling bond states around the Fermi level. The next favorable geometry is the capped nanotube where
${\pi}-bonding$ states localized at the cap and pointing to We tube axis direction occur at the Fermi level. A scaling rule of the induced field linean in the aspect ratio of the tube is also obtained.