導光膜與薄型化背光模組光學最佳化研究

數位化產品為人類生活帶來便利性和娛樂性，通常數位產品會透過顯示介面來呈現可觀看及可讀之內容。在許多的顯示介面中，TFT-LCD(薄膜電晶體液晶顯示器)產品因具有輕、薄、省能源及低幅射之優點，已被視為主流顯示技術。 TFT-LCD因本身不會發光，故需透過背光模組提供光源才能顯示各種影像。背光模組的重要零件為導光板(膜)，是控制顯示介面輝度與均勻度的主要核心。其中，導光板上的微結構被設計來達到導光的目的。導光板種類目前技術可分成射出型導光板、押出板印刷導光板和熱壓模具製程導光板(膜)等三種。在這三種導光板當中，現階段只有熱壓成型可以把導光板厚度作薄，熱壓成型以PC材質為主，並以不同厚度的PC材料作為導光薄片，其最薄厚度可到0.1mm，也因為厚度可以達到像片材一樣薄，故此種導光板又被稱作為導光膜(Light Guide Film)，並自2010年起逐漸被廣泛應用於背光模組、發光鍵盤和手機按鍵等產品當中。使用導光膜的主要的好處是它可以讓產品輕薄化，若是應用在發光鍵盤和手機按鍵，則可減少使用LED顆數，具減少耗電量的優勢。本論文主要的研究便是應用於TFT-LCD中導光膜與薄型化背光模組光學之最佳化。我們以13.3吋LED背光模組和3.5吋LED背光模組設計為例，利用熱壓模具製程所製作之導光膜，探討不同的厚度、不同表面和不同的導光板製程之微結構，逐一找出薄型化背光模組光學最佳化設計，以實現輕薄化概念與應用。依據我們的實驗結果，使用較厚的導光膜可以有較佳的輝度，較平滑的導光膜端面可使光亮度有更均勻的分佈，而採用120度V-cut 端面可減少暗區的距離。

關鍵字

導光膜；導光板；背光模組； LGF ； LGP

並列摘要

Digital products bring convenience and entertainment to people’s everyday life. Commonly, observable and readable contents were presented through display interfaces in digital products. Among various display interfaces, the TFT LCD (thin-film-transistor liquid-crystal-display) has been recognized as the mainstream display technology for having the advantages of light weight, slim body, energy saving and low radiation. TFT LCD itself does not emit light, however, and back-lighting module is necessary for TFT LCD to provide illumination for depicting the images. Light guiding plate is one of the core accessories in back-light module, which controls the display lumens and uniformity through using different micro structures on its surface. Currently, there are three different fabrication techniques, injection formation, extrusion formation, and thermal embossing formation, for the light guiding plate. Among these three techniques, thermal embossing formation is the only one that has the ability to make the light guiding plate with a thickness less than 0.1mm. For those extremely thin light guiding plates, it is often called light guiding films (LGF) rather than light guiding plates. The low power consumption and slim body of the LGF make it having been adopted as lighting keyboard in compact products such as personal computers and cell phones since 2010, which can also reduce the number of LEDs used in these products. The main focus of this thesis is to optimize the optical performance of the LGF for its application in slim back-light module. In this work, we take 13.3” TFT LCD and 3.5” TFT LCD as our design object, trying to find the optimum design of the back-light module by using thermal embossing LGF with different thicknesses and micro surface structures. From our experimental results, it is found that using thicker LGF can improve the overall luminescence, smoother edge of the LGF gives more uniform light distribution, and facilitating 120o V-cut at the edge of the LGF reduces the hot-spot when using the LED light bar as the light source.