摘要
本研究採用新的製備程序來製作PDLC膜。其概念是將熱硬化樹脂和光硬化樹脂混合成雙官能性的樹脂系統與適量的液晶均勻混合後。先以光起始聚合反應，形成能夠支撐整個PDLC膜的亞克力半膠化薄膜，再對未反應的環氧樹脂作熱處理，使其行熱硬化反應而引發相分離。研究中分別選用固態顆粒狀之DICY與液態之AN2143作為環氧樹脂的硬化劑，以探討液晶於不同系統中相分離行為的差異。結果顯示當以DICY作為硬化劑時，無論是溫度引發相分離或聚合引發相分離（polymerization-induced phase separation），固態粉末之DICY顆粒，具有類似成核劑的作用而促使液晶E63之相分離行為提早發生。因此，在聚合反應過程中若有液晶相分離發生時，其相分離行為分為兩階段，即DICY引發與非DICY引發之相分離。反觀，在液態硬化劑AN2143的系統中，液晶相分離而形成微滴的行為，是發生在硬化後的降溫程序而非聚合過程，且若硬化的時間過長，則在降溫的過程中液晶微滴的形狀會由近乎圓形變至不規則形狀。此外，在TSC的實驗中，發現若硬化後的PDLC膜中有液晶微滴存在時，則TSC圖譜中則會出現分別代表液晶微滴之玻璃轉移、環氧樹脂之玻璃轉移及□轉移的電流峰。□轉移為PDLC 膜經電場極化後，累積在液晶微滴/基材樹脂界面的空間電荷，在除去電場後的升溫過程之放電行為。其中TSC圖譜中代表□轉移的電流峰強度會隨硬化劑含量或熱硬化時間的增加而增加。當PDLC膜處於電場作用的環境中時，累積在液晶微滴/基材樹脂界面的空間電荷會降低實際穿越液晶微滴的電場強度，而使得PDLC膜的Vth與△V增加。但若PDLC膜之操作溫度提高時，PDLC膜的Vth與△V則逐漸遞減。

在研究中，我們嘗試建立一組理論模式，來模擬光線通過PDLC膜時的光散射行為。理論模式乃以AD近似理論為基礎作進一步的修正與擴充後而得。由於光線多重散射行為過於複雜，目前尚無理論模式建立。故我們僅針對光線之單一散射行為探討，即假定PDLC膜中液晶微滴是單層分佈。有關PDLC膜中液晶微滴粒徑分佈，我們採用Weibull分佈函數來描述。假定各微滴的液晶分子呈單向排列，且指向矢一致的條件下（即on-state狀態），由模擬結果可瞭解不同微滴型態下的光散射行為。將模擬結果與實驗數值比對，還可部分定量化的解釋與描述PDLC膜之電光性質與液晶微滴粒徑分佈或基材折射率間的相互關係。

The polymer-dispersed liquid crystal (PDLC) film was prepared from UV curable acrylic, thermal curable epoxy, and liquid crystal (LC) mixture. The UV irradiation and heat treatments were in sequential steps. In this studies, solid DICY and liquid AN2143 were respectively selected to be the curing agent for epoxy. The results showed that, for DICY system, in either thermal or polymerization-induced phase separation, the undissolved DICY particles acted as nucleation agents and were capable of inducing E63 to separate out early. Hence, the LC droplets were formed during polymerization. However, for AN2143 system, the LC droplets were not formed during polymerization but during the subsequently cooling process. A thermal stimulated current (TSC) analysis was used to investigate the physical structures of PDLC. In the TSC spectrum of PDLC, three relaxation peaks were observed: the glass transition of liquid crystal, the glass transition of polymer matrix, and the □ transition. The □ transition represents the discharge behavior of space charges, and its intensity increased as the curing time and content of the curing agent increased. The space charges would reduce the actual electrical field across the LC droplets, therefore the switching voltage of PDLC increased as the curing time and/or content of curing agent increased. In the last part of this research, we established the theoretical model to describe the light scattering behaviors of PDLC film. The model was based on the anomalous-diffraction (AD) approach and the uniform molecular orientation pattern in LC droplets was used in the model of simulation. Then, the Weibull function was adopted to define the morphologies of LC droplets in PDLC film. According to the simulation results, it could be understand that the relationship between light scattering behaviors, morphology of LC droplets, the refravtive indices of polymer matrix and molecular orientation pattern in LC droplets.

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