The Dynamic ECD, a reflective display device developed by Funai Electric Advanced Applied Technology Research Institute Inc, smoothly displays characters and images on the entire screen despite the fact that it is a passive-matrix display driven by the line-scanning method (See related article).
This is possible because the new display device is designed to increase the dye concentration by repeating scan-write operations for each line so that the characters and images stand out on the screen.
High-speed scan repeated to display image
The Dynamic ECD features high-speed performance, which enables to display an A6-sized image within 0.1 seconds when the electrode density is set to 3 pieces/mm. Existing passive-matrix electronic paper displays change images by wiping the entire screen in about one second. Thus, the images being changed can be clearly observed. In addition, the only way for a bistable device to display grayscale images is to employ dithering.
On the other hand, Funai's device can increase the contrast by repeatedly wiping the entire screen in an extremely short time. Because the contrast reaches 100% within 0.1 seconds, the device can smoothly display images on the entire screen just like an active matrix panel. At present, the device scans the screen two to five times before the contrast reaches 100%.
Gray scale representation is also possible with pulse width modulation. Although the device supports only four levels of gray scale at the moment, it will be possible to provide higher levels in the future, the company said.
Write voltage of 6V, hold voltage of 3V
The write and hold voltages of the Dynamic ECD is 6V and 3V, respectively, according to the company. In other words, the device requires a voltage to retain an image on the screen, and it is not a bistable ultra-low power device like e-paper. For the moment, Funai plans to expand the applications of the device to displays for mobile information devices.
The power consumption is 0.16mW/cm2 for writing and 0.08mW/cm2 for holding. The writing speed is 0.1 sec/60 lines, while the erase speed is 0.5 sec/60 lines. At present, it has a life of about 1,000,000 writes, according to the company.
The latest prototype was manufactured by using a glass substrate. Spacers are dispersedly located in the device to maintain the gap of 50μm. Another device that employs a plastic film is also under development, the company said. It aims to reduce the price of the latest device to 1/3 of that of the existing LCD panels.