It has been about 30 years since cholesteric liquid crystals were considered as a candidate for an electrooptic flat panel display. The reflective bistable cholesteric liquid crystal display (BCD) has two stable optical contrasting states at zero field. One is the weakly scattering focal conic state and the other is the reflecting planar state....[ Read more ]

It has been about 30 years since cholesteric liquid crystals were considered as a candidate for an electrooptic flat panel display. The reflective bistable cholesteric liquid crystal display (BCD) has two stable optical contrasting states at zero field. One is the weakly scattering focal conic state and the other is the reflecting planar state.

The planar state reflects a brilliant pre-selected color without the use of a polarizer, color filter or dichroic dye. The bistability and reflectivity of bistable cholesteric display allow for a high information content display on a low cost passive matrix with reduced power consumption, since power is not needed to continuously refresh the image. The reflected color of the cholesteric liquid crystal mixture provides for a bright display that does not need polarizers and is readily viewed in front-lit condition.

In this research work, a BCD panel was successfully made and two driving circuits were implemented. One is using field programmable gate array (FPGA) and the other is using commercial STN driver chips. A low cost, novel and portable BCD was developed. The display is well suited for applications in electronic newspaper, pagers, personal data assistants, etc.

First of all, a BCD panel by using MLC 6204-000 have been developed. However, the driver speed is not high enough which has 40ms reset time and 20ms addressing time. Therefore, a new developed BCD panel by using DLC 42121 is developed. The driver speed is much faster than that using MLC 6204-000. The reset time is only 10ms and the addressing is only 4ms which is suitable for application in electronic newspaper, pagers and personal data assistant. The voltage requires for reset is ±30V and the FC selection voltage is ±20V and P selection voltage is ±30V.