• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2004.05a
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• pp.161-164
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• 2004

본 연구에서는 고휘도 백라이트에 있어서 일반적으로 휘도 향상을 위해서 사용하는 프리즘 혹은 편광프리즘 등의 고가의 기능성 광학시트를 사용하지 않고, 확산시트만을 사용하여 고성능의 BLU 를 제조할 수 있는 핵심부품으로서 프리즘 도광판에 대해서 연구하였다. 고휘도 프리즘 도광판을 구현하는 방법으로 먼저, 광학적으로 시뮬레이션을 통해서 가능성을 검증하고, 기본적인 광학구조의 설계를 수행한 후, 이를 stamper 방식의 사출성형으로 실물을 구현하여 설계의 재현성을 확인하는데 역정을 두었다. 실험결과, 17 inch, 두께 8 mm 사양의 모니터용 도광판에 있어서, 고휘도 BLU를 구현하기 위해서 도광판 밑면과 윗면에 프리즘 구조를 부가한 도광판의 경우에 기존의 인쇄형 도광판보다 약 20%의 휘도향상 효과를 확인할 수 있었으며, 향후 확산시트만을 사용한 고휘도 백라이트로의 응용가능성을 검증할 수 있었다.

• International Journal of Naval Architecture and Ocean Engineering
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• v.8 no.5
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• pp.456-465
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• 2016

In order to optimize the performance of a Wells turbine with fixed guide vanes, the designs of an end plate and a ring on the tip of the turbine rotor are proposed as penetrating blade tip treatments. In this study, numerical investigations are made using computational fluid dynamics (CFD)-based ANSYS Fluent software, and validated by corresponding experimental data. The flow fields are analyzed and non-dimensional coefficients $C_A$, $C_T$ and ${\eta}$ are calculated under steady-state conditions. Numerical results show that the stalling phenomenon on a ring-type Wells turbine occurs at a flow coefficient of ${\phi}=0.36$, and its peak efficiency can reach 0.54, which is 16% higher than that of an unmodified turbine and 9% higher than in the case of an endplate-type turbine. In addition, quasi-steady analysis is used to calculate the mean efficiency and output work of a wave cycle under sinusoidal flow conditions. As a result, it has been found that the ring-type turbine is superior to other types of Wells turbines.

• Transactions of Materials Processing
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• v.16 no.1 s.91
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• pp.42-47
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• 2007

LCD-BLU is one of kernel parts of LCD and it consists of several optical sheets: LGP, light source and mold frame. The LGP of LCD-BLU is usually manufactured by etching process and forming numerous dots with $50\sim300{\mu}m$ diameter on the surface. But the surface of the etched dots of LGP is very rough due to the characteristics of the etching process during the mold fabrication, so that its light loss is high along with the dispersion of light into the surface. Accordingly, there is a limit in raising the luminance of LCD-BLU. In order to overcome the limit of current etched dot patterned LGP, optical pattern with continuous microlens was designed using optical simulation CAE. Also, a mold with continuous micro-lens was fabricated by UV-LiGA reflow process and applied to 7 inch size of navigator LCD-BLU in the present study.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2006.05a
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• pp.189-190
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• 2006

A patient table considering x-ray transparency, mechanical safety and compact multi-axis moving mechanism has been developed. The goal of medical imaging technology is to keep radiation exposure of patients during x-raying to a minimum. In order to obtain clear pictures at low dose, however, the x-ray table which supports the patient must be sufficiently permeable to radiation to allow good image resolution. The table top is made of low density foam for x-ray transparent effective area and structural aluminum plate to connect moving mechanism under the table, covered with thin carbon fiber. This sandwich construction is very rigid and lightweight, so the table top can handle relatively heavy load comparing to its cantilevered structure which is unavoidable as long as cooperate with C-arm radiography. To verify the design results finite element static analysis and experimental tests have been done. According to the verification the results well satisfy certification guide lines as a medical device.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.5 s.182
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• pp.190-196
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• 2006

Transparent materials are widely used in the fields of optic parts and bio industry. We have experiment to find out the characteristics of the micromachining inside transparent materials using femtosecond laser pulses. With its non-linear effects by very high peak intensity, filament (plasma channel) was formed by the cause of the self-focusing and the self-defocusing. Physical damage could be found when the intensity is high enough to give rise to the thermal stress or evaporation. At the vicinity of the power which makes the visible damage or modification, the structural modification occurs with the slow scanning speed. According to the polarization direction to the scanning direction, the filament quality is quite different. There is a good quality when the polarization direction is parallel to the scanning direction. For fine filament, we could suggest the conditions of the high numerical aperture lens, the short shift of focusing point, the low scanning speed and the low power below 20 mW. As the examples of optics parts, we fabricated the fresnel zone plate with the $225{\mu}m$ diameter and Y-bend optical wave guide with the $5{\mu}m$ width.

• Korea-Australia Rheology Journal
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• v.19 no.3
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• pp.171-176
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• 2007

LCD-BLU (Liquid Crystal Display-Back Light Unit) of medium size is usually manufactured by forming numerous dots with $50{\sim}300\;{\mu}m$ in diameter by etching process and V-grove shape with $50\;{\mu}m$ in height by mechanical cutting process. However, the surface of the etched dots is very rough due to the characteristics of the etching process and V-cutting needs rather high cost. Instead of existing optical pattern made by etching and mechanical cutting, 3-dimensional continuous micro-lens of $200\;{\mu}m$ in diameter was applied in the present study. The continuous micro-lens pattern fabricated by modified LIGA with thermal reflow process was tested to this new optical design of LGP. The manufacturing process using LIGA-reflow is made up of three stages as follows: (i) the stage of lithography, (ii) the stage of thermal reflow process and (iii) the stage of electroplating. The continuous micro-lens patterned LGP was fabricated with injection molding and its test results showed the possibility of commercial use in the future.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2014.10a
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• pp.99-101
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• 2014

A Comprehensive Vibration Assessment Program (CVAP) for steam generator internals (SGI) of Advanced Power Reactor 1400 (APR1400) is being performed in accordance with the United States Nuclear Regulatory Commission (U.S. NRC) Regulatory Guide 1.20 (RG 1.20) revision 3. This paper studies the vibration characteristics of moisture separator assembly as part of the vibration and stress analysis program for APR1400 SGI CVAP. The natural frequencies, mode shapes, and structural behavior of moisture separator assembly were investigated through modal analysis using finite element method and experimental measurement. Since the moisture separator consists of several items with complicated shape, an idealized shell model was used in the finite element analysis. Group of local modes caused by moisture separators and significant modes of shroud and separator support plate were identified. The results of this paper are to be utilized in the structural response analysis of moisture separator assembly.

• Journal of the Semiconductor & Display Technology
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• v.19 no.3
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• pp.30-35
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• 2020

A microlens has been fabricated by various methods such as a thermal reflow, hot embossing, diamond milling, etc. However, these methods require a relatively complex process to control the microlens shape. In this work, we report on a simple and cost-effective method to fabricate a cylindrical microlens (CML), which can diffuse light widely. We have employed a slot-die head with the dual plate (a meniscus guide with a protruded μ-tip and a shim with a slit channel) for coating of a narrow stripe using poly(methyl methacrylate) (PMMA). We have shown that the higher the coating gap, the lower the maximum coating speed, which causes an increase in the stripe width and thickness. The coated PMMA stripe has the concave shape. To make it in the shape of a convex microlens, we have applied the thermal reflow method. When the stripe thickness is small, however, its effect is negligible. To increase the stripe thickness, we have increased the number of repeated coating. With this scheme, we have fabricated the CML with the width of 223 ㎛ and the thickness of 7.3 ㎛. Finally, we have demonstrated experimentally that the CML can diffuse light widely, a feature demanded for light extraction efficiency of organic light-emitting diodes (OLEDs) and suppression of moiré patterns in displays.

• Journal of the Korean Society of Manufacturing Technology Engineers
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• v.19 no.4
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• pp.553-561
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• 2010

In flat panel display or semiconductor industries, they install the equipments with fine line width and high throughput for fabrication and inspection. The equipments are required to have the linear stage which can position the work-piece with high speed, fine resolution on wide range of motion. In this paper, a precision planar linear XY stage is proposed. The stage has a symmetric planar window configuration and is guided by air-bearings on granite plate. The symmetric planar window configuration makes the stage has robustness against dynamic and thermal disturbances. The air-bearings let the stage move smooth on straight guide bar and flat granite surface. The stage is actuated by linear motor with Halbach magnet array (HMA). HMA generates more confined magnetic flux than conventional array. The linear motors are optimized by using sequential quadratic programming (SQP) with the several constraints that are thermal dissipation, required power, force ripple and so on. The planar linear XY stage with the symmetric planar configuration and the linear motors is implemented and then the performance such as force ripple, resolution and stroke are evaluated.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2000.07a
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• pp.600-603
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• 2000

Recently, Display devices have become important in the information-oriented society and flat display devices are greatly demanded. Liquid crystal display(LCD) represents one of the most promising devices for large size desk-top monitors, notebook PC and car navigation system. However LCD cannot give forth light itself and must have backlight system. The most popular backlighting system is composed of a lighting-guide plate and CCFL as a lighting source. The number of CCFL must increase up if the area of display is increased. So a new backlighting source with high luminance is needed for large LCDs. In this paper, we proposed a surface discharge FFL with the new electrode structure like the needle shaped electrode as the variation of cell structure to high luminance and low power consumption. In comparison with different electrode structure it has low discharge voltage and current and good optical characteristics. So it has better discharge characteristics than different surface discharge FFL and can be fungible for a backlight as a lighting source in LCDs.