The basic study on new high picture quality reflective-type color liquid crystal display

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High-quality, lightweight, reflective color LCDs with low power consumption are important devices for highly functional and portable information terminals. Though various reflective LCDs have been proposed, only reflective color LCDs using a single-polarizer TN-LCD and STN-LCD are presently being used in practical applications. However, the quality of the reflective LCDs must be improved. To achieve this, we proposed some new reflective LCDs like the following and numerically analyzed the electro-optical properties of the LCDs.1. Single-polarizer DSTN-LCD and FDSTN-LCD with a quarter-wave plate2. Single-polarizer DTN-LCD and FSTN-LCD with a quarter-wave plate3. Single-polarizer MDTN-LCD with a retardation filmWe found that the display mode (1) exhibits a high contrast ratio of infinity in theory and high luminous reflectance of 48 %, independent of the duty ratio, and display modes (2) and (3) exhibit a very high contrast ratio and a high luminous reflectance of 50 % through optimum deign of the device parameters. In addition, the consumption of the reflective color TN-LCD is several times larger than that of the reflective color STN-LCD. It is thus desirable to reduce the TN-LCD's power consumption while maintaining its high image quality. In order to confirm the possibility to reduce power consumption, we analyzed the relationship between the electro-optical properties of some new reflective LCDs like the following and the on-voltage of a TFT-LCD.1. Single-polarizer DTN-LCD and FSTN-LCD with a quarter-wave plate2. Single-polarizer DTN-LCD and FSTN-LCD with a retardation film3. Single-polarizer TN-LCD with retardation film of the two sheetsWe found that the LCDs exhibit an achromatic image of high luminous reflectance of about 50 % and a very high contrast ratio, even if the on- voltage is reduced to 2V. The power consumption can thus be decreased to about 1/6 to 1/7 that ofa current reflective 5V TFT-LCD in the on- state.