新穎透明電極用於可撓式高分子分散式液晶晶胞之製作與特性研究

Flexible Polymer Dispersed Liquid Crystal Cell based on Novel Transparent Electrodes

邱崇欽(Chung-Chin Chiou)

指導教授 ： 許根玉

國立交通大學/電機學院/光電工程系所/碩士(2018年)

摘要

此篇論文透過將多層結構金屬薄膜(TiO2/Ag/TiO2)與石墨烯兩種不同的可撓式電極，運用在高分子分散型液晶(PDLC)晶胞的特性分析，來說明這兩種新穎透明導電電極應用於可撓式光電元件的可行性與前瞻性。PDLC為一由微米大小的液晶滴與聚合物基材組成的複合型晶胞，可經由上下透明電極板施以電壓，在液晶層內產生外加電場，來進行液晶分子的調控，進而產生電光調制的效應。
其中，鍍有TiO2/Ag/TiO2 之可撓PET基板為透過射頻磁控濺鍍機將三層材料依次濺鍍在100m厚的PET塑膠基板上，它的特點在於濺鍍溫度可維持在40-60℃，不會破壞塑膠基板，我們透過SEM顯微鏡來分析基板的表面形貌，使用四點探針量測其片電阻，光譜儀測量穿透率，以及自製的彎曲測試機量測可撓特性，綜合這些量測，我們找到最佳厚度組合，以之進行元件製程。另外，鍍有石墨烯的可撓PET基板的產生，則是將低壓化學蒸鍍(LPCVD)成長在銅膜之石墨烯薄膜，經由轉印的技巧將其轉印在100m厚的PET基板上，我們經由對三種不同轉印方式得到的石墨烯基板進行拉曼光譜量測量，評估各種轉印方式對石墨烯的品質之影響，發現使用熱解黏膠的方式最為快速簡單，然後我們以此方法轉印數個不同層數石墨烯基板，再將轉印而來的基板進行如上述對多層鍍膜金屬基板的各種電性、光學以及機械性質的測量，進行轉印次數對基板性質的影響研究，找到最佳的轉印次數後，製作基板以供元件製程使用。我們量測各型態的PDLC晶胞樣品的穿透率-電壓曲線，藉以研究樣品晶胞的電光調制性質，並分析兩種透明導電層應用於可撓式元件之特性。

關鍵字

可撓式 ； 電極 ； 高分子分散式液晶

並列摘要

In this thesis, we demonstrate the fabrications and characterizations of flexible polymer dispersed liquid crystals (PDLC) cell with novel transparent electrode, including multilayer structure (TiO2/Ag/TiO2) and graphene layers as transparent conductive electrodes (TCE). The cell is formed by a PDLC layer sandwiched with two flexible polyethylene terephthalate (PET) substrates with TCE layers. The PDLC is composite layer that consists of submicron-size droplets of liquid crystal randomly dispersed in a polymer matrix. Its transmission can be modulated by applying an external voltage on the TCE. Thus, we have studied the modulation characteristics of each device to evaluate those TCE films for applications on flexible optoelectronic device.
For preparation of flexible substrate with TiO2/Ag/TiO2, we deposited three layers on PET by using the Radio Frequency (RF) magnetron sputtering technique on PET at low temperature (40-60℃). Meanwhile, flexible substrate with graphene is obtained by transferring the graphene thin film, which is grown on copper foil by low pressure CVD method, onto a 100-m thick PET film. Several measurements have been conducted to characterize those substrates. First, the SEM microscope is performed to study the surface structure of the thin film. Second, the sheet resistance of substrate is taken by a 4-point probe platform and then transmittance spectrum of substrate is taken by a spectrometer. In addition, the flexibility of the substrate is conducted by using a homemade bending testbed. With these results, we can make figure of merit to select the best substrate for fabricating PDLC device. Thus, after preparation of those devices, the transmittance dependence on the driving voltage and response time of each device are measured and discussed.

並列關鍵字

flexible ； electrode ； PDLC

參考文獻

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