本論文研究題目為『可光控與可電控空間濾波器於鍍有光導電配向膜之液晶薄膜之研究』。本論文主要利用鍍有摻雜碳六十之光導體聚合物配向膜之扭轉型向列相液晶盒，不照光下，外加直流電場下造成配向膜與液晶介面相反電性電荷的累積以形成一個與外加直流電場反向的內建電場，造成屏蔽效應。此效應造成施予液晶層的有效電場小於外加電場，當有效電場小於Freedericksz transition臨界電場時，液晶導軸無法轉動。
當液晶盒受到綠光照射時，光導體膜之導電率會有所提升，使得內部界面累積電荷會產生放電，導致屏蔽效應減弱，使得有效電場越接近外加直流電場。在本研究中，可分別選擇固定外加電壓或固定外加綠光強度，藉以改變綠光強度或改變外加電壓大小來達到調控屏蔽效應強弱，以達成使用同一液晶空間濾波器元件，具有既可光亦可電雙重調控之空間濾波功能。

This thesis is entitled “Optically and electrically-controllable spatial filter based on a liquid crystal (LC) film with a photoconductive layer”. The sample used is a twisted nematics with a photoconductive polymer alignment film doping with C60. Under the application of a dc field, charges with opposite electricity can accumulate on the interfaces between the substrates and the LCs so as to build up an internal field which is opposite to the applied field. The so-call screen effect can cause that the magnitude of the effective field on the LC layer is smaller than that of the applied field on the cell. The LC director cannot reorient unless the effective field is lager than the threshold one for Freedericksz transition.
Once the cell is irradiated with a green beam, the conductivity of the photoconductor may enlarge such that the internal surface charge can discharge to reduce the screen effect. This can lead to the reduction of the difference between the effective field on the LC layer and the applied field on the cell. In this study, one can vary the intensity of the incident green beam or the magnitude of the applied field to optically or electrically control the influence of screen effect on the cell. This method can lead to the achievement for fabricating a LC spatial filter device with an optically- and electrically-controllable filtering ability.

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