When electronic ink is coated on paper, cloth or other flat objects, people can change the color of hundreds of millions of particles with proper electric shock, thus changing the displayed patterns and characters according to people's settings. Electronic ink can display colors and patterns as long as the colors of dyes and particles in particles are adjusted.
This method uses microcapsules that can change the black and white state under voltage to realize image display. The charged white titanium oxide particles and black carbon powder particles in microcapsules move up and down under the action of voltage, thus drawing a black-and-white image. It has the characteristics of ideal contrast and brightness vision, low power consumption, light weight, easy thinning and free shape. In addition, some products use the electrophoresis phenomenon of charged toner to improve the contrast between black and white by increasing the concentration of toner. Although electronic paper is called "paper", it is actually a soft display similar to paper. In order to make the display have the soft, curly and foldable characteristics of ordinary paper, the key is to replace the glass substrate of the existing display with a soft substrate such as plastic, thin glass or metal sheet. In addition, another important feature of electronic paper display is that the display medium has memory characteristics, so electronic paper does not consume electricity when displaying the picture, but only needs to consume electricity when updating the picture.
At present, there are four kinds of electronic paper display technologies being developed in various countries:
The first is electrophoretic display technology (EPD). Electrophoretic display technology is to encapsulate black-and-white charged particles in a micro-cell droplet structure, and control the black-and-white particles with different charges to move up and down through an external electric field, thus presenting a monochrome display effect of black and white. The representative manufacturers are American E-Ink company and SiPix company. EPD technology is very suitable for electronic paper, because it can display high reflectivity and high contrast in black and white display. At present, Samsung, LG Display, Seiko Epson, Letterpress Printing and Thai Science and Technology in Taiwan Province Province of China have all cooperated with E-Ink to develop various electronic paper displays and adopted their EPD panel "Vizplex".
Followed by electronic powder fluid display technology (QR-LPD). Bridgestone Corporation of Japan released the electronic powder fluid display technology. The display medium is black and white powder with different charges produced by nano-scale crushing of resin. Powders are filled in the micro-cup structure of air medium, and the electrophoresis phenomenon of black and white powder occurs in the air by using the electric field of upper and lower electrodes, in which controlling the working voltage of powder is an important topic in practical application. Because air is used as the medium of electrophoretic powder, QR-LPD reaction speed is fast. However, its disadvantage is that high voltage is needed to drive the electronic powder fluid, which makes it possible to drive the electronic powder fluid only in a passive way at present when the high voltage-resistant TFT (thin film field effect transistor) module has not been successfully developed. At present, Bridgestone is cooperating with Hitachi to invest in the research and development of QR-LPD electronic paper "Albirey".
The third is cholesterol liquid crystal display technology (Ch-LCD). R&D research institutions of this technology include Kent Display Company of the United States, Fujitsu Company of Japan, Fuji Xerox Company of Japan and Industrial Technology Research Institute of Taiwan Province Province of China. Cholesterol liquid crystal is a special spiral liquid crystal mode. This special arrangement structure is realized by adding an optical rotator to nematic liquid crystal, and the display effect is realized by using two different polarized light rotations of cholesterol liquid crystal molecules at different potentials. Cholesterol liquid crystal is a kind of reflective display, which uses external light source to display images, without backlight, and has bistable characteristics, so cholesterol liquid crystal display technology is also very energy-saving. At the same time, the technology can also mix red, green, blue and other colors by adding brighteners with different rotating pitches to meet the needs of color display.
Finally, bistable nematic liquid crystal display technology (Bi TNLCD). This technology was developed by the French company Nemoptic. This technology uses nematic liquid crystal. Display panels are two kinds of substrates, and their liquid crystal molecules have different retention forces. When a certain rated voltage is applied for a long time, liquid crystal molecules will stand vertically relative to the substrate. At this time, if the voltage value is rapidly reduced to zero, the liquid crystal molecules around the substrate with strong holding power will be pulled in the falling direction, while the liquid crystal molecules around the substrate with weak holding power will fall in the opposite direction, and the liquid crystal molecules in the middle position of the substrate will produce a twist angle. If the charged state is slowly released in two steps, the liquid crystal molecules will fall in the same direction due to the weakening of elastic ability, and there will be no twist angle. In these two states, one is black and the other is white, which basically forms a bistable display. By changing the voltage amplitude when the voltage is released in the second step, the ratio of black area to white area will change, that is, the middle tone can be modulated.