多重配向角應用於快速響應之水平配向邊緣場效驅動液晶顯示器

Abstract

目前液晶顯示器在市面上仍是顯示器中的主流，其優點包含高解析度、低功耗而且輕薄，但相比其他類型的顯示器，其有個較主要的缺點，那就是液晶的響應時間慢，而這會導致影像在快速移動時造成影像劣化(image degradation)。在現今趨勢如AR/VR 等將有更多顯示器的應用要求更快的響應時間以達到影像近乎即時零延遲的成像，因此對於液晶顯示器這無疑是個重大的挑戰，而本篇論文將針對水平配向的邊緣場效驅動顯示器並改善其響應時間。 本篇論文採用光配向的方式，將電極邊緣處的液晶使之與電極排列方向夾一小角度，在施加電場後液晶即能夠隨著電場方向而轉向不同的方向以產生虛擬牆幫助響應時間的縮短。分析不同的電極寬度和電極間距所帶來的影響，發現無論是電極寬度或是間距增加，都會同時造成穿透率提升但響應時間變慢，之後探討了虛擬牆間距帶來的影響，發現同樣的虛擬牆間距下其響應時間會在同一個水平上下，並且虛擬牆間距越小則響應時間越快。 接著探討各種配向參數對此結構的影響，發現配向區域的比例對結果幾乎沒有影響，這也提升了其在製程上對位的誤差容忍率，而配向區域的寬度和角度對整體影響不大，僅會稍微影響臨界電壓和上升時間，因此選擇較小的寬度和角度才不會造成在暗態漏光更嚴重，而相鄰的配向區域方向若一致會導致虛擬牆間距變長，使得響應時間變慢，故讓相鄰兩配向區域的液晶交錯排列才能夠得到較快響應時間的結構。最後比較此結構和傳統邊緣場效驅動發現此結構的響應時間確實大幅下降，而利用雙層電極的方式亦可讓原先穿透率不高的單層結構提升穿透率。雖然此結構的液晶初始排列並非均勻，但其在可視角上還是有不錯的表現。

Liquid crystal displays are still the mainstream of the displays on the market. Their advantages include high resolution, low power consumption, thinness and light weight. In contrast to others displays, they have a major drawback which is their slow response time. Slow response time will cause the image degradation of fast-moving pictures. The application of displays like virtual reality or augmented reality will require faster response time to achieve nearly zero latency so it must be a big challenge to the liquid crystal displays without a doubt. Therefore, this thesis focuses on parallel-aligned fringe field switching liquid crystal displays and help to improve their response time. In this thesis, we made the liquid crystals near the fringe of the pixels have a small angle related to the pixel alignment direction. They can rotate in the different directions to generate the virtual walls which can help to reduce the response time. First, we analyzed the effect of the pixel width and the electrode gap width. We found that whether pixel width or electrode gap width increased, it would cause higher transmittance but slower response time. Subsequently, we studied the effect of virtual wall. Same virtual wall pitch caused a same level of the response time, and smaller the virtual wall pitch, faster the response time. After that, we investigated the effects of various parameters of the alignment area. We found that the proportion of the alignment area almost had no effects on the result, and it can rise the allowable deviation in processing. Same did the width and the angle of the alignment area. They only can affect the threshold voltage and the rise time a little bit so we chose smaller width and angle of alignment area to reduce the light leakage in the dark state. Moreover, same direction of the adjacent alignment area would make virtual wall pitch be longer and response time be slower. Therefore, it can help to gain a faster response time structure by making the liquid crystal of adjacent area of alignment area aligned alternately in the different directions. Finally, we compared this structure we proposed with the conventional fringe field switching. The structure we proposed actually have the response time reduced significantly. We can also use the double-layer structure to enhance the transmittance of the single layer structure which has lower transmittance. Although the initial alignment is not uniform in this structure, they still have acceptable performance.