奈米壓印法製備可撓式無配向層液晶元件之製程與光電特性研究

Abstract

可撓式軟基板顯示器被認為是下個世代顯示器的主流，相較於現今蓬勃發展的平面液晶顯示器，它具有更為輕薄、可撓曲以及可捲曲收藏等等特性。一般來說，現在較為成熟並且有較多研究心力投注的可撓式顯示器設計原型有以下三種：微杯電泳顯示器、有機發光二極體顯示器以及液晶顯示器。它們各有不同的特性以及適合的應用設計。而在本論文中所報導的研究工作正是採用液晶顯示器作為我們的設計原型。 在這個研究中，我們成功製作出無配向層的可撓式扭轉向列型液晶元件。藉由奈米壓印技術，我們將微小溝槽的奈米結構轉製在軟性塑膠基板表面上，使其具有配向液晶分子的功能而不需要製作額外的配向層。此外，對於此一無配向層的可撓式液晶元件我們也做了相關的光電特性量測以及模擬，結果其驅動電壓大約為1.2伏特，反應時間則大約為15毫秒，其性質皆可與傳統的硬式基板液晶元件相比較。而此一可撓式液晶元件在撓曲的情形下，其驅動電壓及反應時間皆不會隨撓曲曲率而改變，僅有配向的效果會受到撓曲的影響而變差，進而影響了液晶元件尋常黑操作模式的暗狀態（或是尋常白操作模式的亮狀態）。模擬的結果也顯示向列型液晶元件在撓曲的條件下，其幾何形狀的影響是相當有限的，而可以不列入考慮。 此一新穎的可撓式向列型液晶元件的製作方法不但整合了基板與配向層，並且將來導電性塑膠材料更加成熟的時候，我們可以採用這個設計方法進一步將電極層、配向層以及基板全部整合在一起，提供一個有潛力來解決可撓式液晶顯示器多層結構在撓曲條件下不穩定性問題的方法。

The flexible display is regarded as the mainstream of the next generation of displays. It has advantages of thin profiles, light weight, flexibility, and being rollable. Generally speaking, three leading prototypes of flexible displays are “Electrophoretic Display (EPD)”, “Organic Light Emitting Diode Display (OLED display)” and “Liquid Crystal Display (LCD)”. In this thesis, the prototype we adopt is just LCD. In this thesis, we successfully fabricate the flexible alignment layer-less twisted nematic liquid crystal cell. By means of Nano-imprinting lithography, we can transfer the microgroove pattern onto the thermoplastic, and thus we prepare the patterned flexible substrate which can be used to align LC molecules directly without coating additional layer. We also measure and simulate electro-optical properties of such cell. The threshold voltage is about 1.2 V and the response time is about 15 ms, which are comparable to those of the traditional rigid substrate LC cell. And under bending condition, this flexible LC cell is still functional with its threshold voltage and response time remaining the same; and the result of simulation tells us the effect of geometry is very limited so that we do not have to take it into consideration. When the material “conductive plastic” is more mature and practicable, we can use this design to further integrate the alignment layer, electrode layer and the substrate to reach the goal of “one-step” substrate preparation process of flexible LC cell, and also offers a potential total solution to the problem of instability in multi-layer configuration of flexible LC cell.