擬PI垂直配向共聚薄膜液晶元件的光電特性探討

Electro-Optical Characteristics of the Pseudo-PI Vertical Alignment Copolymer Films Liquid Crystal Device

本研究目的為發展擬-聚醯亞胺 （polyimide, PI） 垂直配向共聚薄膜，為非接觸光配向方式之液晶元件。利用液晶／光硬化單體之相分離技術，將具有負誘電異方性液晶、烷基長碳鏈壓克力單體、兩種不同長度的雙酚主鏈型壓克力單體與光起始劑以適當比例摻混；經由紫外光 （ultra-violet, UV） 照射後，因相分離而形成雙層垂直配向共聚薄膜。而針對不同長度的主鏈型壓克力單體結構對於液晶分子在此垂直配向模式下之光穿透度、對比度以及反應時間等光電特性探討。由此實驗結果發現改變不同長度的主鏈型壓克力單體可以改善液晶元件的光電性質，並且在適當比例之液晶摻混系統下其對比度可達2028:1。而此新穎垂直配向技術於液晶顯示器工業可縮短傳統配向技術之PI 段前製程，並期望利用此光配向方式製作具有傑出的光電特性且低價化之液晶元件。

The purpose of this study is to develop a pseudo-Polyimide (PI)vertical alignment (VA) copolymer film which is a non-contact photoalignmentmethod for liquid crystal (LC) devices. We used the LC/photocurablemonomer phase separation technique. In a mixture of negativedielectric anisotropy (N-type) LC, and alkyl long carbon chain acrylicmonomer, two different lengths of biphenol main chain type acrylic monomersand a photoinitiator were combined in the proper ratio. Forming theupper and lower layers of a VA copolymer film only required Ultra-Violet(UV) light irradiation to aid the phase separation of the LC mixture system.As for the different length main chain type acrylic monomer structures forthe LC molecules under the VA mode, properties such as optical transmittance,contrast ratio and response time, have been characterized. Theresult of this experiment revealed that changing the length of main chain type acrylic monomers in some cases improved the electro-optical propertiesof LC devices. The contrast ratio reached 2028:1 under the properratio LC mixture system. This novel VA technology for the liquid crystaldisplays (LCDs) industry can replace PI pre-processing and we hope to usethe photoalignment technique to build in excellent electro-optical characteristicsand low cost LC devices.