Reflective-type TN-LCDs with a single polarizer

Abstract

In recent years, compact, portable information equipment such as notebook computers and PDAs has progressed remarkably. This, in turn, has created a need for bright reflective color liquid crystal displays (LCDs) without a backlight. In responses to this requirement, we have previously proposed a new, achromatic reflective TN-LCD, and STN-LCD with one polarizer and one retardation film. The LCDs enables creation of a reflective color LCD using a color-mixing system such as the micro color filter type. However, the TN-LCD of the normally black mode has the problem that the higher the resolution is, the lower the luminance becomes due to the space between electrodes. In order to solve this problem, we will propose a normally white mode achromatic reflective TN-LCD, composed of the above mentioned normally black mode reflective TN-LCD and one liquid-crystal polymer film with a twist angle of the same magnitude, but with an opposite-handed to the LC layer. The electro-optical properties of the LCD have been numerically analyzed, and it was found that several sets of solutions exist for obtaining an achromatic image with high luminance as well as a high contrast ratio. In this paper, we will focus on the achromatic reflective TN-LCD of normally white mode, which is promising for a new reflective LCD in respect to full color displays, especially for document displays.