雙色性染料對紫外光聚合高分子分散液晶之影響

Abstract

本論文主要在探討雙色性染料對子外光聚合高分子分散液晶(UV Curing PDLC)的影響,製作條件包括聚合時紫外光之強度和染料之濃度.其次我們 也研究表面處理對PDLC的影響,製作條件是不同的表面處理方式,包括水平 排列,旋轉九十度排列和沒有排列三種.我們利用對各樣品穿透率之量測來 了解各樣品在不同的條件影響下所呈現的特性,而在我們的測量中,據有較 低的最小穿透率時,即意味著有較高的對比度.實驗中我們使用單體NOA65 和液晶E7,ZLI4281/2,ZLI2806的混合液來製作 PDLC薄膜樣品.在雙色性染 料的影響方面,隨著染料濃度增加,在不加電壓的情況下,最小穿透率隨著 降低,但因染料對紫外光也有吸收效應,所以欲得相同液晶滴大小時,染料 濃度大者需用較強的紫外光來聚合.在表面處理方面,若以偏振光為光源, 則水平排列樣品在分子指向與入射光偏振方向相同時會有最低的最小穿透 率,其次是旋轉九十度排列,最後是沒有排列的樣品.若以自然光為光源入 射,則旋轉九十度排列的樣品會有最低的最小穿透率,其次是沒有排列,最 後是水平排列樣品.此實驗結果與理論相吻合. The transmission properties of dichroic dye doped polymer dispersed liquid crystal(PDLC) films which have been formed by ultraviolet(UV) initiated photopolymerization and liquid crystal (LC) phase seperation are studied as a function of the polymer's curing UV intersity and dichroic dye concentration. We find that the dichroic dye plays a role that increase not only the absorption in incident light but also the liquid crystal droplet size of the PDLC films. The minimum transmission of PDLC films decreases as dichroic dye concentration increases. On the other hand, the effect of surface treatment on transmission of PDLC is studied. Different off-state alignments of the liquid crystal in PDLC droplet are obtained by the surface treatment. In twisted 90.degree. alignment type, the minimum transmission is lower than that in random alignment type and in parallel alignment type of equal thickness. It can be predicted that the contrast of twisted 90.degree. alignment type is higher than the other two types. The experimental results agree with the theoretical prediction well.