| 摘要: | 薄膜電晶體-液晶顯示器電視之液晶面板因背光模組內部冷陰極螢光燈管熱源的影響導 致翹曲變形，進而造成液晶面板與前框發生壓擠情形，導致液晶面板局部畫質不良現象。本 文發展一套驗證技術方法，運用數值分析與實驗量測並相互驗證來探討23 吋液晶顯示器之 液晶面板因熱導致熱結構問題引致的畫質不良與畫質改善之研究。整體之數值分析裡，首先 運用計算流體力學之有限體積法求得整體液晶顯示器模組之溫度分佈，在此以求得液晶面板 之溫度分佈，而後運用熱彈性之有限元素法的數值法來模擬液晶面板熱結構現象，本文在數 值分析之研究方法能有效模擬出實際物理現象。 此外，本文建立一套實驗量測平台，運用NI 的設備與撰寫LabVIEW 程式來完成量測設 備與感測器之整合，本文共進行三種量測實驗於液晶顯示器與液晶面板，其量測是從液晶顯 示器開機後到穩態之整個暫態過程，在溫度量測上包含液晶顯示器之背光模組內部的冷陰極 螢光燈管模組、反射片、擴散板及液晶面板之量測。在熱變形方面，即量測液晶面板之熱變 形量，在熱應變之量測中即量測液晶面板之熱應變，以瞭解液晶面板之溫度與熱變形及熱應 變分佈之相互關係，其中在液晶面板之實驗量測中皆包含有加前框與未加前框之量測。 在液晶面板之畫質改善部分，本文提出兩種設計變更之研究方法，以改善液晶顯示器畫 質不良現象，第一項之設計變更是在液晶面板與前框增加適當的間距，主要防止熱變形後的 液晶面板與前框產生壓迫，藉此改善液晶面板畫質不良現象。另一項設計變更是在背光模組 開散熱孔以自然對流機制進行散熱，此舉將有助於液晶顯示器在不加裝額外冷卻元件之條件 下獲得散熱能力的提昇。研究結果顯示能有效降低液晶顯示器整體構件之溫度，特別是能有 效的降低液晶面板溫度，避免液晶面板在熱變形後與前框產生壓迫，以改善畫質不良現象。 此研究旨在建立一套系統性之模型分析及驗證技術，藉此修正原分析模式，研究中將提 出設計變更準則，以改善液晶面板畫質不良現象。將能縮短設計時程、節省開發成本，並能 運用此驗證模式至其它之液晶顯示器產品上，以提升平面顯示器設計研發能力。 The heat source form cold cathode fluorescent lamps (CCFLs) on the backlight unit (BLU) causes panel of thin film transistor-liquid crystal display (TFT-LCD) TV to warp, then LCD panel extrudes with the front shield and leads to local worse image quality on the TV. The study aims at developing a reliable procedure for evaluating the performance of 23 inch TFT-LCD TV in thermal fluid fields and thermal-mechanical of LCD panel by using numerical simulation and experimental measurement during the operation, as well as for reducing their temperature and thermal deformation to improve image quality of TFT-LCD TV by design modification. In the numerical simulation, first, thermal fluid fields of the whole TFT-LCD TV are analyzed by using computational fluid dynamics (CFD) with finite volume method (FVM) to acquire mainly the temperature field of the LCD panel. Second, thermal-mechanical of the LCD panel is analyzed by thermo-elastic finite element method (FEM). The results show good compatibility to demonstrate that the simulation process successfully predicts to warp phenomenon and defects of display in the panel of TFT-LCD TV. In addition, the data acquisition system (National Instruments®, NI) is employed to acquire sensor data and drive the motion apparatus as well. As a driving program, LabVIEW® is used to integrate the operation and data-acquisition interfaces. The sensing equipment includes three major parts which are explained in detail in the following separately. The thermocouples are used to measure the temperature variation on the CCFLs, the rubber caps, reflection sheet, diffuser plate inside BLU and LCD panel of the TFT-LCD TV. The non-contact displacement sensor (NCDS) transversely moves by an X-Y table to acquire the thermal deformation displacement data of the LCD panel with and without the front shield, respectively. The strain gages are used to measure the thermal strain of LCD panel with and without the front shield, respectively. Consequently, the temperature, thermal deformation and thermal strain distributions on the LCD panel can be obtained. During the operation, all the measurements are conducted and recorded from power-on (initial transient) till reaching a steady state. The study proposes the LCD TV module improving technology to solve the thermal deformation of LCD panel problem and to improve the image quality of LCD TV. The first task shows the successful choosing an appropriate gap between the panel and the front shield to prevent extrusion, and thus to achieve the improvement of image quality. In another design modification, the concept of opening aperture at the BLU provides an effective heat dissipation by natural convection for a TFT-LCD TV without adding extra heat management modules. The results show effectively lower the whole temperature distribution of TFT-LCD TV and effectively reduce the thermal deformation of LCD panel. This prevents the LCD panel from squeezing by the front shield. Again, the color distortion is also removed. The study had set up a systematic analysis and an experimental measurement. The achievements can assist engineers in designing, analyzing, and testing for the improving image quality of LCD-TV. The technology will promote an ability about the research and development of flat panel display (FPD) industry. The applied approaches can even be broadened to other TFTLCD products. |
