In today's world of increasing office automation and computer-aided personal-communications systems, display devices play a very important role as person-machine interfaces. Above all, high-definition, full-color flat-panel displays will be key devices in the near future when processing huge amounts of information—including pictorial images via computer networks and telecommunication systems that transcend the present limitations of time and place—will be possible.
Passive-matrix liquid-crystal displays (LCDs) represent the most widely used choice for portable display devices. Figure 1 illustrates the essential components and operating principle of a typical LCD. Each pixel is addressed by the top- and bottom-line electrodes of the cell based on information signals, producing a light image. By installing a color filter of red, green, or blue for each pixel, full-color images can be displayed. However, the essential problems of crosstalk among pixels and low response speed become serious with an increase in the number of pixels, resulting in a low contrast ratio and failure of the display to keep up with the signals.