1. Field of the Invention
This invention relates to a multi-layered-type liquid crystal display device with the use of a twisted nematic display process that can attain an excellent color display.
2. Description of Prior Art
Liquid crystal display devices are now being used in clocks and electronic calculating machines, in displays of computers terminal and word processor, in televisions, and in a variety of other uses in many fields. Recently, there has been an extremely large demand for liquid crystal display devices because of the changes to multicolor and full-color displays, which are already being made use of in the fields of graphic display and image display. Color display, that has been widely put into practical use, is attained by a liquid crystal cell with color filter layers. The liquid crystal cell functions as a light-switcher, and produces various colors. The main kind of display mode is a twisted nematic display mode attained by a liquid crystal cell in which the liquid crystal is twisted at 90.degree.. (The "twisted nematic" is referred to hereinafter as "TN".) However, when the TN display device is driven at a high duty ratio, the contrast of the image decreases. On the other hand, a supertwisted birefringence effect (which is referred to hereinafter as "SBE") process has been suggested, which produces TN oriented liquid crystal which is twisted at angles of approximately 180.degree. to 270.degree. larger than 90.degree.. With the SBE process, the curve in the vicinity of the threshold value increases steeply, and even when the duty ratio increases, it is possible to obtain a high contrast ratio. However, because birefringence effects of liquid crystals are used, the dependence of the display characteristics on the wavelength of light is theoretically higher than with the TN display in which the liquid crystal is twisted at 90.degree.. Thus, it is very difficult to adapt it for use in a full-color display.