側入光源式背光模組中發光二極體與導光板之光耦合效率研究

Abstract

薄膜電晶體液晶顯示器(Thin film transistor liquid crystal display，TFT LCD)近年來以超出預期的發展速度飛快的成長，而其中白光發光二極體(Light-emitting diode，LED)效率的快速提升，有效降低了LED光源成本，加上環保意識的抬頭，現已全面導入不含汞與低耗能的LED作為背光模組(Back light unit，BLU)光源。由於LED光源架構的優勢與TFT LCD技術的成熟，突然間產品以出乎意料的速度往大、輕、薄、窄、等方向快速進化，以符合市場的需求。 但同時兼顧大、薄、窄、等需求所須使用之LED側入光源式BLU架構，在組裝作業時LED與導光板(Light guide plate，LGP)所存在的偏差常常會造成BLU輝度(Luminous)不穩定與品味(Taste)異常等問題。 本研究採用TracePro光學模擬軟體進行模擬搭配量測數據來分析LED光源與LGP之耦合狀況，再針對現行LED側入光源式BLU架構進行組裝公差分析，最後根據分析結果提出有效的改善方式。 以3014 LED搭配2.0mm厚度LGP為例，LED發光面與LGP入光面的間隙與LED中心與LGP中心垂直於LGP出光面方向的偏移量在現行架構設計的偏差上分別有著最大10.3%與5.6%的光能量損耗存在，而經過改善後分別可將損耗降低至8.4%與1.2%。

Thin film transistor liquid crystal display’s needs grow dramatically in nearly a decade. The mercury-free and low power consumption light emitting diodes for back light units have been enabled by the improvements in light emitting diode performance that provid high efficiency for cost saving and eco-friendly. And the market demands are pushing the LCD product to go bigger, lighter and slimmer. The rapid-changed specification request from customers often result the unstable luminous and abnormal taste of the back light units from the dimensional deviation of light emitting diode and light guide plate in the assembly process. In this work, we used TracePro to simulate the light coupling efficiency between light emitting diode and light guide plate and measured data to verify the result first. Then we obtained the improvement result for optimizing the structure of back light unit by tolerance analysis. The gap between 3014 LED and 2.0mm thickness LGP in the existing structure has maximum 10.3% light energy consumption. With applying improvement structure, we can reduce light energy consumption from 10.3% to 8.4%. The center offset between 3014 LED and 2.0mm thickness LGP in the existing structure has maximum 5.6% light energy consumption. With applying improvement structure, we can reduce the light energy consumption from 5.6% to 1.2%.