降低膽固醇液晶彩色濾光片色偏之研究

Abstract

近年來由於節能減碳意識的抬頭，持續提升大型顯示器的效率是個受 關注的議題。此外，增長手持裝置操作時間的關鍵之一也在降低小型顯示 器的功耗。有別於一般彩色液晶顯示器上吸收型的彩色濾光片，使用膽固 醇液晶螺旋結構的彩色濾光片，可以反射特定光波長範圍而有效率的產生 彩色光。然而此高效能的膽固醇液晶彩色濾光片存在著斜視角產生色偏的 問題。 本論文嘗試以重新分配顯示器出射光的方式來改善膽固醇液晶彩色濾 光片的的大視角色偏問題。實驗上我們驗證了在選擇適當的背光光型分佈 並搭配不同光柵分光角度的機制，對顯示器的紅綠藍三主要色光都可顯著 提高大視角的色彩穩定度。我們也依照混色的原理，提出一個簡單的色彩 穩定度預測模型。經由實際驗證，這個模型可以提供準確度約在七成以上 的預測。

Improving energy efficiency of liquid crystal displays (LCDs) has beenhighly concerned in recent years. Unlike the conventional absorptive color filters adopted in LCDs, the combination of a cholesteric liquid crystal (Ch-LC) film and a quarter wave plate can be utilized as color filters partially reflecting instead of absorbing backlight to enhance its efficiency. However, the selective reflection of Ch-LC color filters is viewing-angle dependent, which results in severe color shift problem. In this thesis, transparent gratings were applied to modify backlight distribution for reducing color shift of Ch-LC color filters. Ch-LC color filters for red, green, and blue light reflections were fabricated and the viewing angle dependences of color coordinates were investigated. The results showed that the reduction of color shift strongly depended on the backlight distribution and grating properties. According to the color matching theory, we also developed a simple model to evaluate the color stability of our proposed Ch-LC color filters.