• Title/Summary/Keyword: AMLCD

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The Fabrication of Four-Terminal Poly-Si TFTs with Buried Channel (Buried Channel 4단자 Poly-Si TFTs 제작)

  • Jeong, Sang-Hun;Park, Cheol-Min;Yu, Jun-Seok;Choe, Hyeong-Bae;Han, Min-Gu
    • The Transactions of the Korean Institute of Electrical Engineers C
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    • v.48 no.12
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    • pp.761-767
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    • 1999
  • Poly-Si TFTs(polycrystalline silicon thin film transistors) fabricated on a low cost glass substrate have attracted a considerable amount of attention for pixel elements and peripheral driving circuits in AMLCS(active matrix liquid crystal display). In order to apply poly-Si TFTs for high resolution AMLCD, a high operating frequency and reliable circuit performances are desired. A new poly-Si TFT with CLBT(counter doped lateral body terminal) is proposed and fabricated to suppress kink effects and to improve the device stability. And this proposed device with BC(buried channel) is fabricated to increase ON-current and operating frequency. Although the troublesome LDD structure is not used in the proposed device, a low OFF-current is successfully obtained by removing the minority carrier through the CLBT. We have measured the dynamic properties of the poly-Si TFT device and its circuit. The reliability of the TFTs and their circuits after AC stress are also discussed in our paper. Our experimental results show that the BC enables the device to have high mobility and switching frequency (33MHz at $V_{DD}$ = 15 V). The minority carrier elimination of the CLBT suppresses kink effects and makes for superb dynamic reliability of the CMOS circuit. We have analyzed the mechanism in order to see why the ring oscillators do not operate by analyzing AC stressed device characteristics.

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Optical Simulation Study on the Performances of Collimating Films for LCD Backlight Applications (액정표시장치 백라이트용 집광필름의 광학특성 분석을 위한 시뮬레이션 기법 연구)

  • Park, Ji-Hee;Lee, Jung-Ho;Jeong, Jin-Ha;Nahm, Kie-Bong;Ko, Jae-Hyeon;Kim, Joong-Hyun
    • Korean Journal of Optics and Photonics
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    • v.18 no.6
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    • pp.432-440
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    • 2007
  • Optical simulation methods such as a ray tracing technique have been widely used to predict the optical performances of collimating films for LCD backlight applications. It is necessary to optimize simulation conditions which have substantial effect on the simulation result in order to predict accurate performances of collimating films. We have set up a very simple backlight model consisting of a reflection film, a virtual flat light-source, and a prism film, which is a representative collimating film for backlight, in order to analyze the simulation conditions which are strongly correlated with the on-axis luminance gain and the viewing-angle characteristics of prism films. It was found that the dependence of the relative change in the on-axis luminance on the structure and material properties of collimating films can be derived from the above-mentioned simple BLU model and from simulation using it. However, the exact reflection property of the reflection film and the distribution of the incident light onto the optical film were found to be very important for revealing exact viewing-angle characteristics of collimating films.

Optimization of Optical Structure of Lightguide Panel for Uniformity Improvement of Edge-lit Backlight (엣지형 LED 백라이트의 균일도 향상을 위한 도광판의 광구조 최적화)

  • Lee, Jung-Ho;Nahm, Kie-Bong;Ko, Jae-Hyeon;Kim, Joong-Hyun
    • Korean Journal of Optics and Photonics
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    • v.21 no.2
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    • pp.61-68
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    • 2010
  • Optical simulation methods were applied to the edge-lit LED backlight for LCD TV applications in order to optimize the optical structure of the light guide plate(LGP), and thus to improve the uniformity properties by removing the bright spots caused by LED's. The edge-lit LED backlight consisted of three white LED's with a lamp cover, a light guide plate, and a reflection film. When there was no pattern on the entrance side surface of the LGP, the illuminance uniformity was sensitively dependent on the distance d between the LED and the entrance surface. The illuminance uniformity increased with d but its increasing rate slowed down when d was beyond ~ 1.5 mm. When micro-patterns such as a lenticular lens array (LLA) or a serration pattern were formed on the entrance surface, the illuminance uniformity was improved substantially even for the case of very small d. At the same simulation condition, the lightguide with serration pattern showed a better uniformity than that with LLA pattern. Additional improvement could be achieved by changing the refractive index of the micro-patterns. These results suggest that using micro-patterns is a very effective way to reduce the bright spots due to their refracting function for the concentrated incident rays onto the LGP.