一種利用摻雜染料液晶凝膠之電控偏光片

Abstract

利用摻雜染料之液晶凝膠的技術，我們展示一種電控式偏光片，此一偏光片之機制結合了染料分子的光吸收作用、聚合物網絡的光散射作用與液晶排列的方式。本論文中，我們利用場發射電子掃描顯微鏡去觀察摻雜染料之液晶凝膠內的聚合物網絡形態，並且探討光聚合溫度與高分子單體濃度對此的影響。實驗結果顯示，聚合物網絡是由許多奈米大小的高分子顆粒所組成，並垂直於玻璃基板。此外，聚合物網絡與高分子顆粒的大小與光聚合溫度以及高分子單體濃度息息相關：隨著光聚合溫度的升高，聚合物網絡與高分子顆粒也跟隨著增大。不同大小的聚合物網絡也明顯影響著電控式之偏光片的光電特性。此電控偏光片操作在穿透式模式下，在光聚合溫度10□C時，消光比為10:1，操作電壓約 30 Vrms，反應速度約6 ms。同時，考慮光吸收作用與光散射作用，我們也對摻雜染料之液晶凝膠進行光學特性的計算分析。同時，我們對顏色的問題進行探討，並提出不同的方法來解決顏色的問題。最後，我們展示利用摻雜染料之液晶凝膠實現的光電元件--電控式光圈。

An electrically tunable polarizer using dye-doped liquid crystal (LC) gels is demonstrated. The main mechanism of such a polarizer is a combination of the light absorption and the scattering owning to dichroic dyes and poly-domains resulting from polymer networks. In this thesis, we observe the morphologies of dye-doped liquid crystal gels by a scanning electron microscopy. The polymer networks perpendicular to the glass substrates are chain-linked by lots of nano-sized polymer grains. The sizes of poly-domains and polymer grains depend on curing temperatures and monomer concentrations. The domain sizes of polymer networks and the sizes of polymer grains increase by increasing the curing temperature. The domain sizes have influence on electro-optical properties of the electrically tunable polarizers. In our experiments, the maximum contrast ratio of the polarizer can be electrically tuned is around 5:1~10:1 at 10□C curing temperature. The operating voltage is around 30 Vrms. The response time is around ~ 6ms. The optical analysis based on the scattering theory and the absorption theory is discussed as well. Furthermore, we focus on the color issue of dye-doped LC gels LC gels and provide several methods to improve the colors. One application of electrically tunable iris is also demonstrated.