废弃液晶显示屏中液晶的回收与性能检测

为回收废弃LCD(液晶显示器)显示屏中的液晶,提出了“超声波辅助有机溶剂溶解液晶屏、膜过滤和减压蒸馏”的回收方法,并以TN-TFT显示模式的液晶屏为试验对象,对回收液晶的光电性能进行检测和相变分析,以评估其潜在的利用价值.结果表明:方法的回收率达50％；收集物液晶特性明显,呈现出较宽的向列相温变区间和较高的清亮点温度,但纯度不高,达不到日常显示所用的液晶纯度要求(GCMS＞ 99％)；响应时间为33.2 ms,可以满足日常LCD显示屏的要求；介电常数为4.71,折射率为0.089,虽与纯净液晶相比稍有下降,但可满足标准AM-LCD显示的参数要求；阈值电压为3.2V,比纯净液晶有所提高,可进一步去除离子性杂质进行提纯,以降低阈值电压.

Liquid Crystal Recovery and Performance Test from Wasted Liquid Crystal Display Screens

In order to efficiently use valuable liquid crystals from wasted LCD screens, a recycling method using the organic solvent with the ultrasonic wave dissolving LCD screens was proposed. In this method, liquid crystals were collected through membrane filtration and vacuum distillation. Using TN-TFT LCD screens as our experimental materials, detection of photoelectric properties and analysis of phase transition for liquid crystals were conducted. Meanwhile, the potential value of this process was also evaluated. The results showed that the recovery rate of the liquid crystal could reach 50% using this method, the collection has evident characteristics of liquid crystal and shows a wide nematic phase temperature interval and high clearing point. The purity of the collected liquid crystal, however, was not high to fulfill the requirements of purity (GCMS>99%) for watching despite the fact that its response time of 33.2ms meets the demands of LCDs. Although the dielectric coefficient of 4.71and refractive index of the collection of 0.089were a little lower than that of the pure liquid crystal, the liquid crystals could still satisfy the requirements of the standard AM-LCD parameters. The threshold voltage was 3.2V which is higher than that of the pure liquid crystal, which can be lowered by removing ionic impurities.