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A novel bright reflective color STN-LCD with the ISR (Inner Scattering Reflector) structure has been developed for the first time in reflective color STN-LCDs. The adoption of the ISR structure enables the LCD to obtain not only clear image without blur but also 2.5 times brightness as high as that of conventional reflective color STN-LCDs.

Reflective color STN-LCDs should be one of the most promising devices for mobile business tools (MBT), because thedemand such as low cost, low power consumption, light weight and compact size is especially strong for this application. A reflective color STh-LCD with a single polarizer and double retardation films has been investigated. The double retardation films arranged in front of LC-layer enabled the LCD to cotain reflective electrodes inside the panel. Thisconfiguration achieves the bright image with no parallax. A new construction of a reflective STN-LCD with a singlepolarizer has been decided by means of our own method in which the color difference t E* as the optimizing parameterhas been used. Futher, RGB color filters has been newly designed for our reflective LCD, and the aluminum (Al) layer hasbeen introduced as reflective electrodes. As a result, we have realized 7.8-in.-diagonal refrective color STN-LCD(640 x480) which has 15% reflectance, 1 : 14 contrast ratio, 4096 color capability and the sufficient color gamut. It has beenconfirmed that the single polarizer reflective color STh-LCD has sufficient enough performance for MBT use. We believethat it will be a key device for this application.Keywords: reflective color LCD, super twisted nematic (STh), single polarizer mode, electrically controlled birefringence(ECB), retardation film

— A reflective color STN-LCD with a single polarizer and double retardation films has been investigated. The double retardation films arranged in front of the LC layer enabled the LCD to contain reflective electrodes inside the panel. This configuration achieves a bright image with no parallax. A new construction of a reflective STN-LCD with a single polarizer has been developed by means of our own method in which the color difference ΔE* as the optimizing parameter has been used. Further, RGB color filters have been newly designed for our reflective LCD, and an aluminum (Al) layer has been introduced as a reflective electrode. As a result, we have realized a 7.8-in.-diagonal reflective color STN-LCD (640 × 480) which has 15% reflectance, 14:1 contrast ratio, 4096-color capability, and sufficient color gamut. It has been confirmed that the single-polarizer reflective color STN-LCD has sufficient performance for mobile business tools. We believe that it will be a key device for this application.

A reflective full color TN-LCD using low temperature poly-Si TFTs with high resolution and large visible area has been developed for mobile video tools. The optimized construction of normally white (NW) mode TN cell with a single polarizer and the pixel design of high aperture ratio based on low temperature poly-Si TFTs enabled the LCD to obtain high reflectance of 15%, high contrast ratio of 1:15, good achromaticity and wide color gamut.

One of the biggest challenges for LCD technologies is to realize true “Electronic Paper”. The most appropriate solution for it will be reflective color LCDs. Various types of them will be reviewed, and especially single polarizer modes will be emphasized. The trends to go ahead and key technologies will be also discussed.