• 대한금속재료학회지
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• 제46권6호
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• pp.377-381
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• 2008

Prism sheet of LCD BLU which depends on supply from Japan and U.S.A was studied by using Si anisotropic etching and injection molding technologies. First, the prism sheet was patterned on Si wafer through photolithography, and the best conditions of Si etching were determined through etching Si wafer with TMAH to obtain straight optimized zigzag patterns, and a cross pattern to provide light diffusion and concurrent focusing. The etch rate of TMAH was concluded to be constant for $25wt%-70^{\circ}C$ condition. Ni stamp of prism sheet was made by electrodeposition using patterned Si wafer, normal or fast H/C(Heating/Cooling) injections were carried out to fabricate prism sheet. It was known that fast H/C injection could fabricate prism sheet more accurately than normal injection. Zigzag patterns and the cross pattern showed higher transmissivity than the straight patterns because of light diffusion through diagonal direction. The fast H/C injection for zigzag patterns showed lower transmissivity than normal injection because there occurred more light diffusion through precise injection patterns, but the fast H/C injection for straight patterns showed only refraction without diffusion, causing lower transmissivity than normal injection.

• Journal of the Optical Society of Korea
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• 제13권4호
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• pp.478-483
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• 2009

An optical sheet with a cone array is designed, simulated, and fabricated in order to substitute the dual crossed prism sheets in the edge-type LCD backlight. The optimum structure of cone textures that is compatible with the dual crossed prism sheets was obtained by simulating the backlight installed with the cone array optical sheet. A SU-8 photoresist films of thickness $30{\sim}50{\mu}m$ were spin-coated on a polyethylene terephtalate film (PET), and the cone texture array was formed by using the diffuse lithography that employed a photomask with circular patterns and an optical diffuser.

• Journal of the Optical Society of Korea
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• 제13권1호
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• pp.152-157
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• 2009

The structure of the prism sheet and the reflective polarizer sheet in the direct - illumination liquid crystal display (LCD) backlight is optimized and fabricated. The apex angle of the prism sheet was changed from 90 degree to 96.5 and 101.5 degree and the angular spread of the diffuser films attached on the reflective polarizer sheet was changed from 7 to 1.5 degrees. The measured view angle, the normal luminance, and the contrast ratio from the optimized backlight unit showed improved optical performances.

• Journal of the Optical Society of Korea
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• 제12권1호
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• pp.25-30
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• 2008

The optical performances of 15-inch edge-lit backlight were simulated by using a Monte Carlo ray-tracing technique. The backlight model was built by combining a wedge-type light guide plate, a diffuser sheet, a tubular fluorescent lamp with a lamp reflector, and two crossed prism sheets. Angular distributions of the luminance on each optical component obtained from simulation were consistent with those obtained from experiments on a real 15-inch backlight. The constructed backlight model was used to evaluate the optical performances of a micro-pyramid film. It was found that the on-axis luminance gain on the pyramid film is higher than that on one prism film but much lower than that on the two crossed prism films. These results suggest that a reliable simulation model can be used to develop new hybrid films and to optimize the optical structure of edge-lit backlight in order to reduce the developmental period.

• 한국광학회지
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• 제18권6호
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• pp.401-409
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• 2007

액정 디스플레이에 사용하는 직하형 Back Light Unit(BLU)의 확산판과 프리즘판의 개수를 줄이면서도 성능을 개선한 새로운 일체형 복합필름을 제안하고 이들의 광학적 성능을 시뮬레이션으로 분석하였다. 막대 프리즘의 형태와 원통 렌즈 형태를 하나로 합친 복잡한 일차원 형태의 광학프리즘을 만든 후, 이를 연속적으로 배열하여 일체형 복합필름을 구성하였다. 일체형 복합필름의 성능은 조명계 프로그램으로 확인하여 최적의 구조를 정하였다. 이러한 최적 조건하에서 한 장의 일체형 복합필름을 사용하는 10인치 크기의 BLU에서 계산한 광효율은 53.5%이고, 광휘도 균일도는 83.5%였으며, 각도별 광휘도 분포인 배광곡선은 수직으로 $90^{\circ}$이고 수평방향으로 $112.5^{\circ}$이다. 그리고 이러한 설계로 새로운 일체형 복합필름을 제작하였다.

• 한국광학회지
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• 제21권2호
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• pp.53-60
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• 2010

본 논문에서는 휴대전화용 백라이트 유닛의 광학시트를 줄이면서도 휘도와 휘도균일도 및 시야각을 유지하기 위한 복합 도광판을 설계하고 가공하였다. 복합 도광판의 패턴은 가공성을 고려하여 윗면에는 마이크로 급의 프리즘 패턴을 형성하고 아랫면은 나노 및 마이크로 급의 크기가 다른 두 개의 음각 프리즘 패턴을 형성하였다. 이러한 패턴 형상은 금형 코어를 이용한 사출성형을 통해 복합 도광판의 가공성을 확인하였다. 특히 최적화된 복합 도광판은 프리즘 시트 한 장만을 채용하여 통상적인 백라이트 유닛과 유사한 휘도 4560 cd/$m^2$, 휘도균일도 83%, 수직 시야각 $60^{\circ}$, 수평 시야각 $56^{\circ}$라는 성과를 얻을 수 있었다. 결과적으로 도광판의 윗면과 아랫면에 복합 패턴들을 형성함으로써 기존의 백라이트 유닛에서 확산시트 및 프리즘시트 1장을 제거하여 BLU에 적용될 수 있음을 확인하였다.

• 한국소성가공학회:학술대회논문집
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• 한국소성가공학회 2007년도 춘계학술대회 논문집
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• pp.55-59
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• 2007

Technologies of super-precision micro pattern mold machining and high-performance optical films manufacturing using thereof forms the basis of recent display industries which have developed remarkably. Especially, it is the light guide plates and high luminous intensity prism sheets at BLU or FLU in LCD and lenses at virtual keyboard's display to be manufactured by micro machining technology. One way the industry requires to do that is by developing high-performance light guide plates or films which are existing light guide plates, diffusion films and luminance enhancement prism films all in one. In this research effort, basic processing of the micro pyramid structure by shaping method is proposed. Experiments of mold machining of pitch $20{\mu}m$ tetrahedral pyramid and pitch $100{\mu}m$ trihedral pyramid using a $90^{\circ}$ diamond tool were conducted to identify a variety of machining features, such as cutting forces, conditions of the surface, shapes of chips, and influence of materials.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2005년도 춘계학술대회 논문집
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• pp.1597-1600
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• 2005

Recently, the trends of TFT-LCD are large scale and thin thickness, so, the demands of Light Guide Panel(LGP) which is able to substitute for prism sheets are appeared. Functions of LGP obtaining polarization of light of the prism sheet as well as the incidence and reflection of light are demanded. This prismless type LGP to complete functions of the existing LGP and polarization at once must be supported by micro machining technology of LGP surface. In this research, we have used the STAMPER method for the mass product and In-Line process, and the optimized conditions are established by analyzing the cutting force and conditions according to the material and processing properties when the prismless type LGP mold is fabricated. Parameters of the cutting condition were the workpiece and cutting depth.

• Design & Manufacturing
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• 제2권5호
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• pp.1-4
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• 2008

LCD-BLU (Liquid Crystal Display - Back Light Unit) is one of kernel parts of LCD unit and it consists of several optical sheets(such as prism, diffuser and protector sheets), LCP (Light Guide Plate), light source (CCFL or LED) and mold frame. The LGP of LCD-BLU is usually manufactured by forming numerous dots with $50-200{\mu}m$ in diameter on it by erosion method. But the surface of the erosion dots of LGP is very rough due to the characteristics of the erosion 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. Especially, the negative and positive micro-lens pattern fabricated by modified LiGA with thermal reflow process was applied to the optical design of LGP.

• 한국기계가공학회지
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• 제11권5호
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• pp.76-81
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• 2012

The continuing demand for increasingly slimmer and brighter liquid crystal display(LCD) panels has led to an increased focus on the role of the light guide panels(LGPs) or optical films that are used to obtain diffuse, uniform light from the backlight unit(BLU). And the most basic process in the production of such BLU components is the micromachining. LCD BLUs comprise various optical elements such as a LGP, diffuser sheet, prism sheet, and protector sheet with micro patterns. High aspect ratio patterns are required to reduce the number of sheets and enhance light efficiency, but there is a limit to the aspect ratio achievable for a given material and cutting tool. Therefore, this study comprised a series of experimental evaluations conducted to determine the machining feasibility in microcutting various aspect ratio patterns on electroless nickel plated die materials when using single-crystal diamond tools. Cutting performance was evaluated at various cutting speeds and depths of cut using different machining methods and machine tools.