利用光聚合引發相分離製作高分子穩定垂直配向液晶顯示元件之表面型態及光電特性之研究

Abstract

本研究最主要的目的為利用光配向技術發展新式高分子穩定垂直配向模式之液晶元件。利用液晶/壓克力單體之相分離技術，將具有負誘電異方性液晶、兩種市售及三種自身合成的單體與光起始劑以適當比例摻混調配出垂直配向的液晶。最後經由UV光照射後而產生相分離而具有垂直配向的上下層微結構高分子薄膜，對於一般需凸塊和摩擦配向的製程省略，為其優點。微結構高分子薄膜提供比較弱的表面能量，在不需要透過任何的表面處理下可以引起液晶分子自發性的垂直配向。除此之外，此高分子薄膜也可以提供MVA 之效應並同時兼具有廣視角與高對比度。 本研究主要的方向有兩個部分：第一部份為使用不同單體對高分子型態與顯示器元件的光電特性之影響。第二部分是藉由單體的混摻來製備液晶材料與顯示器元件並探討其高分子型態與光電特性。由實驗數據顯示，單純M1單體的高分子型態為均勻顆粒狀是有助於在對比度與反應時間的提升。在M1+M3的組合，雖然保有均勻顆粒狀的型態，但對比度較M1下降5.3%，不過在反應時間與Vth方面是優於M1。以文獻所發表的PSA液晶面板而言，對比度主要是來自於MVA凸塊的去除與開口率的增加，故M1+M3的組合的效果最好並期望利用此光配向方式製作具有良好光電特性及低價化之液晶元件。

The main goal of this study is to use photo-aligment to develop a method for new type polymer-sustained vertical alignment of liquid crystal display device (PSVA LCD). We used the LC/photo-curable monomer phase separation technique and the vertical alignment liquid crystal (VALC) is achieved by mixing negative dielectric anisotropy (N-type) LC, five kinds of the reactive LC monomers which contain two commercial and three synthesized monomers and a photo-initiator. There are upper and lower bilayer of VA microstructure polymer film by UV irradiation, at which the phase separation is carried out, thus, the advantage is omit from protrusion and rubbing processes. Microstructure polymer films provide weak surface energy and induce vertical alignment for liquid crystal spontaneously without any surface treatment. Besides, the polymer films can also provide MVA effect with wide viewing angle and high contrast ratio. There are two main topics in this study. In the first part is to observe the comparison of five different reactive monomers for E-O characteristics and morphology. According to the result of experiment, monomer M1 is capable of fastest response time and highest contrast ratio, because uniform bead like morphology provide a good alignment ability to liquid crystal molecule. In the second part, The responses time and Vth in low gray level could be improved by adding a small amount of M3 into M1, but the contrast ratio decreases 5.3% compare with M1. In general, it is well known that the pixel structure of PSA LCD are protrusion free and higher aperture ratio compare with MVA LCD. By mixing of the M1 and M3 monomer which provided good performance and we hope to use the photo-alignment technique to manufacture excellence electro-optical characteristics and low cost of the LC devices.