The basic study on improved picture quality and reduced power consumption of reflective color liquid crystal displays

高质量、轻量、反射、低功耗的彩色lcd是高功能、便携信息终端的重要器件。虽然已经提出了各种类型的反射lcd，但目前只有使用单偏振片tn - lcd和stn - lcd的反射彩色lcd才被用于实际应用。但是，反射色TN-LCD的功耗是反射色STN-LCD的几倍。显然，这将有利于降低TN-LCD的功耗，同时保持其优越的图像质量。为了实现这一目标，我们分析了TFT-LCD的电光特性与导通电压之间的数值关系。(1)带有延迟层的单偏振片DTN-LCD和FDTN-LCD(2)带有四分之一波片的单偏振片DTN-LCD和FDTN-LCD(3)带有两层延迟层的单偏振片TN-LCD。结果表明，即使导通电压降低到2V， LCD也能呈现出高反射率（约50%）和高对比度的消色差图像。此外，我们发现，如果我们优化延迟膜的双折射色散Δ_<nR>(λ)，即使将TFT-LCD的导通电压降低到2V，具有延迟膜的单偏振反射TN-LCD也能显示出高发光反射率和高对比度的NB和/或nw模式消色差图像。为了进一步测试降低功耗的可能性，我们分析了LC材料参数对TN-LCD电光性能的影响。我们的研究结果表明，如果能够开发出具有低阈值电压（即K_<11>的小值和Δ_ε的大值）的液晶材料，则可以获得具有高质量图像的超低功耗反射TFT-LCD。少

High-quality, lightweight, reflective color LCDs with low power consumption are important devices for highly functional and portable information terminals. Although various types of reflective LCDs have been proposed, only reflective color LCDs using single-polarizer TN-LCDs and STN-LCDs are presently being used for practical applications. However, the power consumption of a reflective color TN-LCD is several times greater than that of a reflective color STN-LCD. Clearly, it would be advantageous to reduce the TN-LCD's power consumption while maintaimng its superior image quality.To achieve this, we analyzed the numerical relationship between the electro-optical properties and the on-voltage of a TFT-LCD in the following single-polarizer reflective TN-LCDs.(1)Single-polarizer DTN-LCD and FDTN-LCD with a retardation fun(2)Single-polarizer DTN-LCD and FDTN-LCD with a quarter waveplat(3)Single-polarizer TN-LCD with two retardation filmsOur results showed that the LCD exhibited an achromat … More ic image with a high luminous reflectance (about 50%) and a very high contrast ratio, even when the on-voltage was reduced to 2V. The power consumption of the panel could potentially be decreased to about 1/3 of that presently needed for reflective TETLCDs operating at 3.2V in the on-stateIn addition, we found that a single-polarizer reflective TN-LCD with a retardation film exhibited a NB and/or NW-mode achromatic image of high luminous reflectance and high contrast ratio, even when the on-voltage of TFT-LCD was reduced to 2V, if we optimized the birefringence dispersion of the retardation film Δ_<nR>(λ).To further test the possibility of reducing power consumption, we analyzed the influence of the material parameters of an LC on the electro-optical properties of the TN-LCD. Our results demonstrated that an ultra-low-power reflective TFT-LCD with a high-quality image can be obtained if a liquid-crystal material with a low threshold voltage (i.e., a small value for K_<11> and a large value of Δ_ε) can be developed. Less