• Journal of the Korean institute of surface engineering
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• v.38 no.2
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• pp.69-72
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• 2005

ITO-Al-ITO multi-layers were deposited at room temperature by RF magnetron sputtering on polyethylene terephthalate (PET). The films were deposited at various pressures of $8\times10^{-4},\;1\times10^{-3},\;4\times10^{-3},\;8\times10^{-3}\;and\;1\times10^{-2}$ Torr. A correlation between microstructure and electro-optical properties was studied. Films deposited? at low pressure have higher transmission, and lower reflectance and resistance than film deposited at high pressure. Sheet resistance, transmission, and reflectance were $141.6\Omega/\Box\;88\%\;and\;6.8\%$ resectively when the deposition pressure was $8\times10^{-4}$ torr, that was the optimum condition.

• Journal of the Institute of Electronics Engineers of Korea SD
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• v.44 no.4
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• pp.91-96
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• 2007

The light extraction efficiency in GaN-on-sapphire LEDs based on a simple model was analyzed qualitatively. The light extraction efficiency in the LEDs is simulated numerically by using ray tracing method. In the present study, the extraction efficiency was simulated on flat LED and PSS(patterned sapphire substrate) LED. The role of the patterned sapphire substrate in PSS LED are analyzed and discussed. And, the effects of reflectance on flat LED and PSS LED were investigated. This analysis of simulation results provide a numeric figure for the extraction efficiency of LEDs and are helpful in the design of high brightness GaN LEDs.

• Korean Journal of Optics and Photonics
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• v.30 no.6
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• pp.219-225
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• 2019

In an infrared optical system, using a cooled detector generates a phenomenon called a narcissus, in which the focal-plane array cooled to very low temperatures is reflected at the lens surface and detected. The narcissus can be removed by non-uniformity correction of the detector pixel, so narcissus is generally ignored in infrared optics. However, non-uniformity correction reduces the sensitivity of the system. Also, as the housing temperature varies due to an environmental temperature change, or a lens is moved for focusing or athermalization purposes, a narcissus may occur even after non-uniformity correction. To minimize such a narcissus, the amount of the effect must be controlled in the lens-design stage. In this paper we designed a midinfrared optical system and analyzed the narcissus by setting the lens surface reflectance to 1%. In addition, the design was divided into stages of an initial design, an improved design, and a minimum design, and the narcissus was improved to about 56% of that in the initial design.

• Applied Chemistry for Engineering
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• v.24 no.6
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• pp.593-598
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• 2013

In this study, we have evaluated the water absorption phenomenon of photoresist dry film, which is commonly used to build circuits on PCB (Printed Circuit Board) by photolithography, by using ATR-FTIR (Attenuated Total Reflectance-Fourier Transform Infrared). We have firstly observed significant change in fracture mode of dry film with respect to temperature and humidity, which we assumed the material transition from ductile to brittle. Secondly, we have established the process of absorption test for determining the diffusion coefficients of water into the dry film both with gravimeter and ATR-FTIR. We have successfully calculated the diffusion coefficients for each environmental conditions from the results which we achieved by gravimeter and ATR-FTIR. Compared to the gravimeter which is a conventional method for absorption test, the ATR-FTIR method in this study has been found to be very easy to use and have the same accuracy as gravimeter. Moreover, we are expecting to use the ATR-FTIR as an appropriate method to study the absorption phenomena related to any kinds of solvent and polymer system.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.972-975
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• 2003

We have performed computer simulation to obtain electro-optic characteristics of reflective hybrid aligned nematic liquid crystal displays driven by fringe field. The results show that the optimal retardation value of the cell is $0.289{\mu}m$, which allows for the cell to have a practical cell gap of larger than $3{\mu}m$ when manufacturing. A reflectance of the dark state is only 0.114% for an incident light 550nm. At this condition, the light efficiency of white state reaches 92.7%. Further, we have studied a new reflective display with polarizer, optical compensation with half plate, LC plus reflector. The display with optimized cell parameters shows low wavelength dispersion and the contrast ratio greater than 5 over exists about $120^{\circ}$ in vertical direction and $160^{\circ}$ in horizontal direction.

• Journal of Information Display
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• v.5 no.3
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• pp.14-17
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• 2004

We have developed a new type of transflective liquid crystal display (LCD) with a single cell gap and a single LC mode. In our transflective configuration, a single LC mode of a 60$^{\circ}$ twisted nematic LC was used for both transmissive and reflective applications. The measured electro-optic characteristics of our transflective LC cell agree well with numerical simulation results. Moreover, the transmittance was found to show similar behavior to the reflectance.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2011.05a
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• pp.184-185
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• 2011

In this study, in order to obtain a high reflectivity for the LED lead frame, tin dip coating and tin plating were conducted respectively, and wettability of LED lead frame with tin solder also was tested by wetting balance tester. A Cu sheet was plated in Cu brighten electroplating bath and followed by immersion in a Sn electro-less plating bath [1]. On the other hand, in the dip coating process, a Cu sheet was dipped into molten tin. In the progress of wetting test, besides wetting balance curve, the maximum measured force($F_m$), the maximum withdrawal force($F_w$) and zero-cross time($t_0$) were obtained in various temperatures. With the maximum withdrawal force, the surface tension was calculated at different temperatures. The Cu sheet plated with bright Cu and Sn show a silver bright property while that of Cu dipped with Sn possessed a high reflectance density of 1.34GAM at $270^{\circ}C$.

• Journal of Information Display
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• v.12 no.3
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• pp.115-119
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• 2011

Optically isotropic liquid crystal (LC) mixture such as blue-phase LC and nanostructured LC composites exhibit the advantages of fast response time, high contrast ratio and wide-viewing angle due to the induced birefringence along the horizontal electric field. Utilizing this mixture, a novel single cell gap in-plane switching-type polymer-stabilized blue-phase transflective liquid crystal display by embedding the nanowire grid polarizer as a polarization-dependent reflective polarizer in the R region is proposed. This device can be used as a normal black mode without any quarter-wave plate or patterned in-cell phase retarder. Moreover, the transmittance is identical to the reflectance so that it will be suitable for single gamma driving. Detailed electro-optic performances, such as voltage-dependent light efficiency and viewing angle of the proposed device configuration, are investigated.

• Journal of the Korean Institute of Telematics and Electronics A
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• v.30A no.10
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• pp.33-40
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• 1993

A reflection type 16x8 S-SEED array from LP(Low Pressure)-MODVD-grown GaAs/AlGaAs extremely shallow quantum well(ESQW) structures, with 4% Al fraction, has been fabricated. Its intrinsic region consists of 50 pairs of alternating 100.angs. GaAs and 100.angs. $Al_{0.04}$Ga$_{0.96}$As layers. A multilayer reflector stack of $Al_{0.04}$/Ga$_{0.96}$ As(599$\AA$)/AlAs(723$\AA$) was incorporated for the reflection plane below the p-i-n structures. The device processing after the MOCVD growth includes the mesa etching, isolation etching, insulator deposition, p & n metallization, and AR(Anti-Reflection) coating. For switching characteristics of the S-SEED in the form of p-i-n ESQW diode, the maximum optical negative resistance was observed at 856nm. Reflectance measurements showed a change from 15.6% to 43.3% for +0.9V to -6V bias. The maximum contrast ration of the S-SEED array was 2.0 and all the 128 devices showed optical bistability with contrast ratios over 2.4 at 5V reverse bias.