利用附加相對電極設計高穿透率低操作電壓藍相液晶顯示器之模擬分析

High Transmittance And Low Operation Voltage Blue-Phase Liquid Crystal Displays With Added Opposite Electrodes

曾培鈞(Pei-Chun Tseng)

指導教授 ： 蔡永傑

國立臺灣大學/電機資訊學院/光電工程學研究所/碩士(2016年)

https://doi.org/10.6342/NTU201700021

摘要

液晶在我們生活中已經是不可或缺的一部分，許多科技產品，像是手機、電腦、電視、平板，都與液晶有所關聯，近年來藍相液晶的發掘，學者提出用高分子聚合物來改善藍相液晶溫度範圍過窄的問題，有效將溫度範圍從1K增加到60K左右，稱之為高分子穩定藍相液晶。高分子穩定藍相液晶有許多的優勢可以有望成為下一個世代顯示器的材料，像是i) 暗態等相性(isotropic dark state) 不像向列型(Nemetics)液晶為異相性與異相性做轉換，所以藍相液晶會有完全暗態的現象。ii) 亞毫秒的反應時間比傳統向列型(Nemetics)液晶快10倍以上，也可以應用在場序式液晶顯示器上，沒有明顯的顏色間斷，不需要色彩濾波器。iii) 不需要配向層處理，可以節省製作成本。被視為極具有潛力的液晶材料。但直到現在高分子穩定型藍相液晶還不能普及，主要的原因在於高分子穩定型藍相液晶顯示器過高的操作電壓以及低穿透率的缺點。因此必須設計新的電極結構，來降低無效區(dead zone) 增加穿透率，並且降低操作電壓。
凸出物之雙邊型電極結構(different electrodes on two sides of protrusion)，由於電極兩側會有電壓差，進而解決電極上方缺乏水平電場的問題，被視為使高分子穩定型藍相液晶顯示器降低其dead zone的方法之一，與單一的電極結構操作電壓並不會相差太多，另一種添加浮接電極也可以修正高分子穩定型藍相液晶顯示器中的電場分佈來提升整體的穿透率，製程上較為複雜一些，上下基板需要對準才能有效的解決電場分布，但其提供了一個不錯的方法以提升穿透率，上述兩種雖然可以有效的提高穿透率，但操作電壓還是偏高的，在本篇論文，我們進一步設計的附加相對電極來改良操作電壓的問題，利用長方體電極的低操作電壓特性，再添加相對的電極，能在電極上方產生較強大的水平電場，以消除錯位線或是無效區域，以達成提升穿透率與降低操作電壓的效果。此外，我們也在模擬過程中，提供了添加不同電極結構的比較，利用更尖、更細的電極來減少dead zone的區域，但操作電壓幾乎不便，而我們使用韓國商業液晶模擬軟體Techwiz(Sanayi System)來進行模擬並分析其結果。

關鍵字

高分子穩定型藍相液晶 ； 降低操作電壓 ； 錯位線 ； 突出物之雙邊型電極結構 ； 添加相對電極結構

並列摘要

Liquid crystal display has become an important part of our life. Many technology products have been associated with liquid crystal, such as mobile phones, computers, televisions, flat-panel. In recent years, the blue phase liquid crystal is proposed, researchers widen the effective temperatures range from about 1K to 60K, by using a polymer stabilization technique, called Polymer-Stabilized Blue-Phase Liquid Crystals (PS-BPLC). Polymer-stabilized blue phase liquid crystal has many advantages that can be expected to become the next generation display materials, such as i) the isotropic dark state. Unlike nematic liquid crystal which is based on anisotropic-to-anisotropic, so there will be completely dark state. ii) sub-millisecond response time. It 10 times faster than nematic liquid crystal, it also can enable advanced technologies such as Field-Sequential-Color (FSC) without color filters, there is no obvious color breakup. iii) no alignment required, the manufacturing cost can be saved. It is regarded as a very promising LCDs material. However, PS-BPLC displays has not been in mass production. The main reason is the obstacles of polymer-stabilized blue phase liquid crystal display, high operating voltage and low transmittance. Therefore, a new electrode structure must be designed to reduce the dead zone area to increase transmittance and reduce operating voltage.
The structure of different electrode on two sides of protrusion, because two sides of protrusion have differential voltage, that solve the lack of a horizontal electric field above the electrode. It regarded as one method that reduce dead zone on PS-BPLCD. The operating voltage has no big change with conventional structure. Another method, we can add floating electrode to adjust the electric field distribution to increase transmittance. But the manufacturing process is more complex, it requires alignment of upper and lower substrates in order to effectively adjust the electric field distribution. Although the above two ways can effectively improve the transmittance, but operating voltage is still high. In this thesis, we design a new structure, added opposite electrodes on rectangular electrode to solve the problem of operating voltage. Because of rectangular electrodes low operating voltage characteristics, if we add the opposite electrode, it can produce stronger horizontal electric field over the electrodes. It not only eliminates disclination lines or dead zones to increase transmittance but lower operating voltage. In addition, we compare different electrode structure, like more sharper and taper electrode to reduce the dead zone region in simulation. The operating voltage is almost same. We carried out the designs and computer simulations using a commercially available LCD modeling software 3D Techwiz (Sanayi System) from Korea.

並列關鍵字

PS-BPLC ； low operation voltage ； disclination ； structure of different electrode on two sides of protrusion ； added opposite electrodes on rectangular electrode

參考文獻

[2] Alexander G P and Yeomans J M 2009 Numerical results for the blue phases Liq. Cryst. 36 1215–27

[5] S. Yoon, M. Kim, M. Su Kim, B. Gyun Kang, M.-K. Kim, A. Kumar Srivastava, et al., "Optimisation of electrode structure to improve the electro-optic characteristics of liquid crystal display based on the Kerr effect," Liquid Crystals, vol. 37, pp. 201-208, 2010.

[6] Y. Li and S.-T. Wu, "Transmissive and transflective blue-phase LCDs with enhanced protrusion electrodes," Journal of Display Technology, vol. 7, pp. 359-361, 2011.

[7] Y. Liu, Y. Li, D. Lai, J. W. Shiu, and S. T. Wu, "P. 77: High Transmittance Blue‐phase LCD with a Floating Electrode," in SID Symposium Digest of Technical Papers, 2013, pp. 1279-1281.

[8] H. Fan, J. Cui, and Q.-H. Wang, "High transmittance blue-phase liquid crystal display with improved protrusion electrodes," Liquid Crystals, vol. 42, pp. 481-485, 2015.