奈米粒子對於高分子分散液晶顯示器光電性質之影響研究

Abstract

本研究的目標針對分散型液晶顯示器(PDLC)混合奈米粒子在液晶的應用。使用TiO2，SiO2，和Al2O3的奈米粒子。尺寸分別為13奈米的Al2O3，20奈米的SiO2和20奈米的TiO2。奈米粒子用來調整聚合物基體的光學折射率。而且，奈米粒子呈現不透明的光色，在產品初期產生霧化效果阻絕光線。另外，奈米粒子比聚合物有更佳的導電性，對於PDLC可提供較低的驅動電壓，有助於產品的應用特性。 在實驗中，我們選擇高複方屈折率(Δn)的E7液晶混合物。以及 NOA65 UV硬化型的預聚合物，因為這兩者能夠比較容易的均勻混合。 NOA65的np是1.524，這與液晶E7的no(1.52)是較接近的。我們首先針對對比值與液晶、預聚合物、介面活性劑（surfactant）和間隔材（spacer）之間的重量百分比關係作調整。最佳值的條件是48.5 wt% 的E7，48.5 wt% 的NOA65，2.5 wt% 的介面活性劑（surfactant），和0.5 wt% 的間隔材（spacer）。透過與奈米粒子的混合，我們觀察到適量的添加對對比值能稍微地提升。我們增加0.19 wt% 的Al2O3在聚合物基體裡，PDLC顯示器的對比值從15.1增加到66.8。我們增加0.48 wt% 的SiO2在聚合物基體裡， PDLC 顯示器的對比值從15.1增加到80.5。我們增加0.019 wt% 的TiO2在聚合物基體裡， PDLC 顯示器的對比值從15.1增加到32.5。但是，我們增加更多的奈米粒子在聚合物基體時，PDLC顯示器的V90也同時的提昇。這可能是由於奈米粒子的聚集緣故吧。

The goal of this study is aimed to blend nanoparticle with liquid crystal for the application of polymer dispersed liquid crystal (PDLC). The nanoparticles of TiO2, SiO2, Al2O3 are used. Their size are 13nm for Al2O3, 20nm for SiO2, and 20nm for TiO2. Nanoparticles are used to adjust the reflective index of the polymer matrix. Furthermore, nanoparticles which show white opaque color, are used to block the light in the initial stage of the products. In addition, because nanoparticles have better electric conductivity than polymers, they can lower the driving voltage of a PDLC cell, This is beneficial for the application of the PDLC products. In our work, we choose E7 as a liquid crystal mixture, which shows high refractive index (Δn). NOA65 is selected as UV curing pre-polymer, which can easily homogeneously mix with E7 liquid crystal. The np of NOA65 is 1.524, which is close to no (1.52) of E7. We first adjust the contrast ratio via changing weight % between liquid crystal, pre-polymer, surfactant, and spacer. The optimized concentration is 48.5 wt% for E7, 48.5 wt % for NOA65, 2.5 wt % for surfactant, and 0.5 wt% for spacer. By mixing with nanoparticle, we observe that the contrast ratio can slightly enhance in a suitable concentration. If we add 0.19 wt % of Al2O3 in polymer matrix, the contrast ratio of a PDLC cell can increase from 15.1 to 66.8. If we add 0.48 wt % of SiO2 in polymer matrix, the contrast ratio of a PDLC cell can increase from 15.1 to 80.5. If we add 0.019 wt % of TiO2 in polymer matrix, the contrast ration of a PDLC cell increase form 15.1 to 32.5. However if we add higher weight ratio of nanoparticle in polymer matrix, the V90 of a PDLC cell are also increased. This could be due to the aggregation of nanoparticles.