本文關(guān)鍵詞： 聚合物分散液晶 紫外光聚合 巰基 電光性能 微觀形貌　出處：《北京科技大學(xué)》2017年博士論文　論文類型：學(xué)位論文

【摘要】：聚合物分散液晶(Polymer Dispersed Liquid Crystal,PDLC)薄膜是將向列相液晶微滴均勻分散在高分子網(wǎng)絡(luò)中而形成的復(fù)合材料。因其制備方法簡單、不需要使用偏振片、基板內(nèi)表面不需要取向處理、液晶層厚度不需要嚴(yán)格控制、可實(shí)現(xiàn)高亮度大面積柔性顯示,目前已逐漸成為平板顯示領(lǐng)域中研究的熱點(diǎn)。在光閥、電控調(diào)光玻璃、大面積柔性顯示及投影顯示儀器等方面具有廣泛的應(yīng)用前景。本論文研究以丙烯酸酯/硫醇高分子網(wǎng)絡(luò)為基體的PDLC材料、利用掃描電鏡觀察高分子網(wǎng)絡(luò)的微觀形貌、利用液晶綜合參數(shù)測試儀測試PDLC薄膜的電光性能、利用紫外/可見/近紅外分光光度計(jì)測試PDLC薄膜在不同波段光的透過率,研究PDLC薄膜的電光性能的優(yōu)化方法并進(jìn)行了綜合分析。主要研究內(nèi)容如下:(1)采用紫外光聚合法制備基于液晶/丙烯酸酯/硫醇的PDLC薄膜,研究了各組分的比例對PDLC薄膜電光性能的影響。實(shí)驗(yàn)結(jié)果表明:我們可以通過調(diào)控PDLC樣品中液晶含量以及光可聚合單體硫醇的含量及其官能度對聚合物網(wǎng)絡(luò)中的液晶微滴尺寸加以控制,從而使PDLC薄膜的電光性能得到優(yōu)化,獲得較低閾值電壓的PDLC薄膜材料。(2)通過添加手性化合物制備基于膽甾相液晶/丙烯酸酯/硫醇的聚合物分散液晶(PDChLC)薄膜。實(shí)驗(yàn)結(jié)果表明:螺距是影響薄膜電光特性的主要因素。隨著螺距的減小,薄膜的驅(qū)動(dòng)電壓和飽和電壓呈逐漸增大的趨勢,并且該薄膜的對比度進(jìn)一步提高。和基于向列相液晶PDLC體系相比較,薄膜驅(qū)動(dòng)電壓和飽和電壓有所升高,而關(guān)態(tài)透過率降低,對比度有所提高。這主要是由于膽甾相液晶的螺距越短,螺旋扭曲力就越大,因此驅(qū)動(dòng)電壓和飽和電壓與螺距變化趨勢相反。(3)研究了不同交聯(lián)劑比率、紫外光強(qiáng)度及聚合溫度對聚合物分散液晶薄膜電光性能的影響。研究表明交聯(lián)劑比率對PDLC薄膜的聚合物網(wǎng)絡(luò)形貌和液晶微滴尺寸有明顯的影響。同時(shí),PDLC薄膜中液晶微滴的尺寸隨著聚合溫度的上升先減小后增大,而隨著紫外光強(qiáng)度的增加逐漸減小。
[Abstract]:Polymer Dispersed Liquid crystal crystal (PDLC) thin film is a composite material formed by uniformly dispersing nematic liquid crystal droplets in polymer networks. Because of its simple preparation method, no polarizer is needed, and the inner surface of the substrate does not need orientation treatment. The thickness of liquid crystal layer does not need to be strictly controlled, it can realize high brightness and large area flexible display, so it has gradually become a hot spot in the field of flat panel display. Large area flexible display and projection display instruments have wide application prospects. In this paper, the PDLC materials based on acrylate / mercaptan polymer network are studied, and the morphology of polymer networks is observed by scanning electron microscope (SEM). The electro-optic properties of PDLC films were tested by liquid crystal comprehensive parameter tester, and the transmittance of PDLC films in different bands was measured by ultraviolet / visible / near infrared spectrophotometer. The optimization method of electro-optic properties of PDLC thin films was studied and analyzed. The main contents were as follows: (1) the PDLC films based on liquid crystal / acrylate / mercaptan were prepared by UV photopolymerization. The effect of composition ratio on electrooptic properties of PDLC thin films was studied. The experimental results show that we can control the content of liquid crystal in PDLC sample, the content of photopolymeric monomer mercaptan and their functionalities on the properties of polymer networks. The size of liquid crystal droplets is controlled, Thus, the electro-optic properties of PDLC thin films are optimized. PDLC thin films with lower threshold voltage were prepared by adding chiral compounds to polymer dispersed liquid crystal films based on cholesteric liquid crystal / acrylate / mercaptan. The experimental results show that pitch is the key factor affecting the electrooptic properties of the films. As the pitch decreases, Compared with nematic liquid crystal liquid crystal (PDLC) system, the driving voltage and saturation voltage of the film are increased, but the off state transmittance is decreased, compared with the nematic liquid crystal PDLC system, the driving voltage and saturation voltage of the film are gradually increasing, and the contrast of the film is further improved. This is mainly because the shorter the pitch of the cholesteric liquid crystal is, the greater the twist force is, so the driving voltage and saturation voltage are opposite to the pitch. The effects of UV light intensity and polymerization temperature on the electrooptic properties of polymer dispersed liquid crystal films were studied. The results show that the ratio of crosslinking agent has a significant effect on the morphology of polymer networks and the size of liquid crystals in PDLC films. The size of microdroplets decreases first and then increases with the increase of polymerization temperature. However, the intensity of ultraviolet light decreases gradually with the increase of UV intensity.
【學(xué)位授予單位】：北京科技大學(xué)
【學(xué)位級別】：博士
【學(xué)位授予年份】：2017
【分類號】：O753.2;TB33

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