多區域垂直配向液晶顯示器之漏光改善研究

Abstract

多區域垂直配向（MVA, Multi-domain Vertical Alignment）面板在製造過程中，於半成品檢查發生漏光顯示不良。多區域垂直配向液晶顯示器於電壓不供給的狀態下為暗態黑畫面，未加電壓目視面板即有漏光現象；目視觀察其發生漏光區域位於面板邊緣，特別集中發生於面板注入口開口側，且注入口開口無框膠的區域即未發生漏光現象，故與框膠材料具有關係；使用偏光顯微鏡細部觀察面板注入口開口側的漏光現象，其框膠距離有效顯示區（AA, Active Area）為四側最短，與面板設計面亦存在關係。進一步將面板拆解後，在液晶層未去除情況下，使用偏光顯微鏡觀察，在彩色濾光片（CF, Color Filter）可視畫素發亮漏光，並且發亮漏光的位置在彩色濾光片的配向突起層（Protrusions）上，故與彩色濾光片結構設計亦有關聯，經由相關文獻的參考，此型態的漏光不良多為液晶配向異常，聚醯亞胺側鏈與液晶側鏈的配向力不足。 本研究在彩色濾光片設計與光罩不變更情況下，嘗試從聚醯亞胺（PI, Polyimide）配向膜材料、框膠材料與液晶盒製程參數研究改善此一漏光現象，研究結果顯示：（1）使用黏度較高的同質性聚醯胺酸溶液（PA, Polyamide），增加彩色濾光片配向突起層表面聚醯亞胺膜與液晶配向力；（2）使用熱穩定性較佳的框膠以減少框膠在固化過程中小分子的釋放，減少影響聚醯亞胺側鏈與液晶側鏈氫鍵或凡得瓦爾力；（3）在框膠固化加熱過程延長抽真空時間與液晶注入前增加溫度與抽真空時間，抽離框膠在固化過程中小分子的釋放；以上3點研究對策可有效降低多區域垂直配向面板因框膠關係與彩色濾光片設計關係所造成的漏光發生率。

Light leakage has been detected during semi-production inspection of multi-domain vertical alignment (MVA) liquid crystal display. The display should be normally black without applying voltage. Light leakage was observed at the edge of the panel with bare eyes. This phenomenon usually happened at the unsealed opening side of the sealant. With closer observation, the light leakage is related to the sealant materials. Under polarizing microscopy observation, the distance to opening side is the closest side to the active area (AA) among all four sides of the sealant. This result suggested its relevance to the panel design. We dissembled the panel without removing the liquid crystal for further observations under polarizing microscopy. Leaked light was seen on the protrusions of the color filters suggesting its relevance with design of the color filter. References have shown light leakage were often results of deviated polyamide and LC molecule alignment. In this study we altered polyimide (PI) alignment, sealant material to study the means to prevent light leakage. The results suggested: (1) using polyimide with higher viscosity can enhance the polyimide film on the protrusions of color filter and LC molecule alignment; (2) using better thermal stability sealant to minimize small molecule released during the process in order to minimized the influence of the polyimide and LC molecule alignment; (3) prolong evacuation time between preheating and cooling of sealant in order to remove the small molecules released during the process. The above three methods effectively reduced the light leakage from on Multi-domain Vertical Alignment (MVA).