Enhancement of Brightness and Contrast in Fluorescent Liquid Crystal Display Using Sensitizing Effect

报道了一种用二向色荧光粉作为客体材料溶解的发光液晶显示器（LCD）。利用增感效应可以提高液晶显示器的亮度和对比度。(1)通过添加蓝色荧光二向色染料或荧光LC作为增敏剂，可使LC宿主体内香豆素-6的绿色荧光强度显著增加。将该增感技术应用于从绿色切换到蓝色的发光型LCD上，提高了绿色荧光的亮度和颜色切换性能。在蓝色LED和红色荧光LC电池组装的LCD中，通过添加敏化剂，也改善了蓝色到红色之间的颜色切换。这些结果表明，利用增感效应也提高了激发背光的光利用率。(2)二向色染料在LC宿主中的绿色和红色荧光强度的增加可以通过敏化效应获得。在有和没有增敏剂的荧光LC电池中测量了吸收和发射二向色比之间的关系。当电压加到细胞上时，平行于LC方向的偏振紫外光激发的荧光强度降低，并低于垂直于LC方向的偏振紫外光激发的荧光强度。此外，澄清了如果敏化剂的二向色比高于发射器的二向色比，则亮度和对比度都可以增强。(3)将两种或三种荧光染料混合在均质、全氮和各向同性排列的LC电池中，成功地展示了发出白色荧光的液晶显示器。施加电压时，白色荧光强度发生变化，而颜色保持白色。采用TN定向提高了陡度。在三种类型的LC电池中，各向同性排列LC电池的对比度最高，为13.3。

Emissive liquid crystal display (LCD) in which a dichroic phosphor is dissolved as a guest material have been reported. Brightness and contrast of the LCDsare enhanced has been demonstrated by using sensitizing effect.(1)The remarkable increase of the green fluorescence intensity from the coumarin-6 in the LC host can be obtained by adding the blue fluorescent dichroic dye or the fluorescent LC as a sensitizer. Applying the sensitization to the emissive type LCD of which color is switched from green to blue, the luminance of the green fluorescence and the color switching property are improved. The color switching between blue to red in the LCD assembled with the blue LED and the red fluorescent LC cell is also improved by adding the sensitizer. These results indicate that the light utilization of the excitation back light is also increased by using the sensitizing effect.(2)The increase of the green and red fluorescence intensity of dichroic dyes in the LC host can be obtained by the sensitizing effect. Relations between absorption and emission dichroic ratios are measured in the fluorescent LC cell with and without the sensitizer. When the voltage is applied to the cell, the fluorescence intensity which is excited by the polarized UV light parallel to the LC direction decreases and becomes lower than that excited by the polarized UV light perpendicular to the LC direction. Moreover, it is clarified that both the brightness and the contrast can be enhanced, if the dichroic ratio of the sensitizer is higher than that of the emitter.(3)Liquid crystal displays emitting white fluorescence are successfully demonstrated by mixing two or three fluorescent dyes in the homogeneous, TN and homeotropic alignment LC cell. The white fluorescence intensity changes by applying the voltage while the color maintains white. The steepness is improved by using TN orientation. The contrast ratio of 13.3 in the homeotropic alignment LC cell is the highest in three types of LC cell.