New liquid crystal alignment materials for low temperature process
LAM TU NGOC
Chen, Huang-Ming Philip
|Abstract:||液晶配向層材料在影像品質以及液晶顯示可靠度扮演重要的角色。對聚亞醯胺層(Polyimide film)的配向摩擦(Rubbing)方法會影響配向膜的製備。然而，製備此配向膜的烘烤溫度高於200°C是使其在軟性基板應用上的主要限制因素。此外，可用於低溫製程之新型液晶配向材料為節能的新興需求。因此，各種具有明顯的化學官能基例如聚乙烯醇(polyvinyl alcohol, PVA)、聚苯乙烯(polystyrene, PS)、聚乙烯苯磺酸(polystyrene sulfonic acid, PSSA)、聚(4-乙基苯酚)(poly- (4-vinylphenol, PVP)和聚乙烯吡咯烷酮(polyvinyl pyrrolidone, PVPD)皆列入研究材料中。這些材料的製程溫度都可以低於110°C。
我們研究了各種高分子表面在作為液晶顯示器上之新型液晶配向材料的光學特性和表面定向。並檢驗這些新型液晶配向材料在機械摩擦配向處理後的光電特性、指向秩序參數(order parameter)和極化錨定能(polar anchoring energy)等等表現。這些新型液晶配向材料的鍵結定向可以透過表面選擇性技術，即近緣X-射線吸收細微組態(near edge X-ray absorption fine structure, NEXAFS)來作歸類。NEXAFS的測量結果明顯地顯示配向摩擦後的高分子表面面內和面外的不對稱性。可證實這些新型液晶配向材料是適合用於平板液晶顯示器低溫製程的軟性基板上。|
Liquid crystal alignment layer plays an important role to the image quality and liquid crystal display’s reliability. The rubbing method on polyimide (PI) film has dominated the alignment films’ preparation. However, high baking temperature over 2000C that is required for the film preparation is a major limitation for its applications into flexible substrates. New alignment materials for low temperature process are the emerging needs of energy conservation. Various alignment materials containing distinct chemical functional groups, such as polyvinyl alcohol (PVA), polystyrene (PS), polystyrene sulfonic acid (PSSA), poly- (4-vinylphenol) (PVP) and polyvinylpyrrolidone (PVPD) are studied. The process temperature for these materials can be as low as 1100C. Optical properties and surface orientation of a variety of polymer surfaces were investigated as new liquid crystal alignment materials in liquid crystal displays (LCDs). The performances of these new liquid crystal alignment materials induced by mechanical rubbing treatment were examined by their electro-optical properties, order parameter and polar anchoring energy. The bonding orientation of these new alignment materials were characterized through surface sensitive technique, near edge X-ray absorption fine structure (NEXAFS). The NEXAFS measurements clearly indicated the in plane and out of plane asymmetries at the surface of rubbed polymers. These new liquid crystal alignment layers are suitable for flexible substrates of low temperature process in flat panel liquid crystal displays.
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