Development of highly dichroic fluorescent dyes for less energy-consuming passive-type guest/host liquid crystal display systems

无源型全色液晶显示器（LCD）消耗大部分的电力，通常由有限容量的电池提供，用于背光系统。为了在移动的通信工具中使用它们，需要开发更少能耗的显示器。在这种情况下，荧光染料（客体）/LC（主体）系统在这样的显示器似乎有吸引力。本研究以4，7-二溴-2，1，3-苯并噻唑为原料，合成了具有烷氧基、烷氧基甲基、烷氧基羰基、乙烯基和乙炔基的各种对称和不对称的4，7-二芳基-2，1，3-苯并噻二唑类化合物。所有化合物在溶液和固体状态下都会发出强烈的荧光，覆盖从蓝色到红色的整个颜色范围。已经在商业液晶介质中评价了它们的二色性，并且染料显示出N>8.0的实际二色性比，并且在商业LC介质中具有良好的溶解性，而没有LC相的不稳定性。以4，7-二（对辛氧基苯基）-2，1，3-苯并噻二唑为客体染料，在MLC-2039中观察到高达9.1的荧光二色性比，在MLC-2039中混合3%（w/w）的荧光染料可制成LCD工作模型。

Passive-type full-color liquid crystal displays(LCDs) consume a large part of the electric power, usually supplied by batteries of limited capacity, for the back light system. The development of less energy-consuming displays is required for their utilization in mobile communication tools. Within this context, fluorescent dye(guest)/LC(host) systems in such displays seem attractive. For their realization it is crucial to develop strongly fluorescent dyes with highly dichroic properties.In this study, various types of symmetric and unsymmetric 4,7-diaryl-2,1,3-benzothiadiazoles having alkoxy, alkoxymethyl, alkoxycarbonyl, ethenyl-and ethynyl groups have been prepared from 4,7-dibrpmo-2,1,3-benzothiazole. All compounds emit strong fluorescence in a solution and in solid state, covering the full color range from blue to red. Their dichroic properties have been evaluated in commercial liquid crystalline media and The dyes show practical dichroic ratios of N>8.0 and possess good solubility in commercial LC media, without destabilisation of the LC phase. With 4,7-bis(p-octyloxyphenyl)-2,1,3-benzothiadiazole as guest dye, a high dichroic ratio in fluorescence of up to 9.1 has been observed in MLC-2039 as the LC matrix.An LCD working model could be fabricated with a mixture of fluorescent dyes in MLC-2039 at a total concentration of 3%(w/w).