However, the application of field emission electrode was not until France Cheng Company exhibited the finished display made of field emission electrode technology at the 4th International Conference on Vacuum Microelectronics in 199 1, which attracted the investment of Candescent, Pixtech, Micron, Ricoh, Samsung, Philips and other companies, and made the FED join the ranks of many flat panel display technologies.
Although FED is regarded as the technology of CRT, its cost can't be compared with CRT in the early stage of development, mainly because of the field emission components. Although the earliest Spindt micro-array is the first technology to realize emission display, its array characteristics limit the display size, mainly because its structure includes a circular hole in each array unit, and the circular hole contains a metal cone. In the manufacturing process, lithography and evaporation technology will limit the size.
The solution is to use this technology instead of Spindt field emission element. After NEC published an article on carbon nanotubes in 199 1, researchers found that graphite synthesized by nanostructures or carbon nanotubes can obtain better field emission efficiency, so the synthesis technology of carbon nanotubes has become a new direction of FED research and development.
At present, in the field of carbon nanotube field emission displays, Japan's Shi Yi Electronics and South Korea's Samsung invested earlier, and Sony, Hitachi, Fuji Photo, Canon, Panasonic, Toshiba, Nikon and NEC also filed patent applications related to nanotechnology, among which carbon nanotubes are the main research and development projects.
Yi Shi Electronics is the first one in the field emission display panel. The company successfully produced 14.5 inch color carbon nanotube field emission display by chemical vapor deposition, and the brightness reached 10000 CD/m2/m2. In addition, South Korea's Samsung has also released a monochrome, 600cd/m2, 15 inch carbon nanotube field emission display, and plans to develop a 32-inch carbon nanotube field emission display for TV sets, successfully achieving low-voltage driving results below 100 volts.
1. Canon and Toshiba develop SED TV.
In the field emission display technology, Canon and Toshiba are developing surface conduction electron emission display (SED), and the technical principle of SED is mainly based on the surface conducted emission electron theory. The difference between SED and CNT FED is that SED has the advantages of smaller driving voltage, no need for coke evaporation electrode and more uniform brightness. Without the focusing electrode, the manufacturing cost can be effectively reduced. The brightness uniformity is a problem of thick film FED, because thick film unevenness means that the current flowing in each pixel is not equal at the same voltage, resulting in uneven brightness on the screen.
Technical differences between table 1 sed and CNT FED
Technology SED CNT FED
Advantages 1 The transmitter has uniform efficiency and uniform brightness.
2. Low driving voltage
3 No focusing electrode is needed. 1 high emission efficiency.
2. It is easier to build a structure.
Disadvantages 1 cracks are difficult to control, and it is difficult to improve the yield.
2 electron emission efficiency is poor. 1 The transmitter is difficult to control and the brightness is uneven.
2 The driving voltage is high.
The electron beam is easy to expand, so the focusing electrode is needed.
Table 2 Performance comparison of various display technologies
Technical support LCD PDP CRT
Power consumption ◎◎△△
Weight ◎◎◎△
Size-○○
Fineness ◎ ◎
Operating environment ◎◎
Brightness ◎◎◎
Coordination ◎ ◎ ◎
Color purity ◎◎◎
Reaction speed χ△χ
Angle of view ◎△◎
Process-increment χ χ
Material cost -Delta χ χ
Drive circuit ◎ ◎△ ◎
In terms of cost, according to Canon and Toshiba, the material cost of the driving circuit of SED panel is similar to that of LCD panel, while the material cost of the panel itself is equivalent to that of PDP, so it has a cost advantage over LCD and PDP as a whole. The fixed cost is high in the initial stage of mass production, but Canon and Toshiba plan to cut this part of the cost before 20 10 to compete with other technologies.
2. The development of carbon nanotube field emission in backlight module.
In recent years, due to the relatively high cost of backlight module of large-size LCD TV, the space and speed of overall cost reduction have been hindered. In addition to the original cold cathode tube, light emitting diode (LED), plane light source technology and carbon nanotube field emission technology have all begun to develop into large-size LCD panels.
At present, South Korea's Samsung Corning, LG Electronics and so on. We have invested in the research and development of carbon nanotube field emission backlight module, and the Institute of Electronics of Taiwan Province Institute of Technology will also develop a sample of carbon nanotube field emission backlight module. In addition, Nissin Machinery Co., Ltd. of Japan also showed the sample of carbon nanotube field emission backlight module in June 5438+ 10, 2005.
5438+0 In June 2005, Nissin Machinery Co., Ltd. and Japan Displaytech2 1 Company jointly developed a backlight module for LCD panel using carbon nanotubes. The sample picture size of this exhibition is 3 inches. Its technical principle is that the glass substrate coated with carbon nanotubes is used as the cathode, the glass substrate coated with fluorescent materials is used as the anode, and the carbon nanotubes are used as the electron radiation source, and the emitted electrons are emitted on the fluorescent materials to emit white light. The diameter of the carbon nanotube used is 20NM, which is a kind of multilayer carbon nanotube with smaller outer diameter in one carbon nanotube. The electric field intensity at the beginning of luminescence is 0.74V/um, which is lower than the previous average of 1 ~ 2v/um. Because the electric field intensity of light emission can be reduced, the voltage applied between the carbon nanotube and the anode can be reduced, thus achieving the purpose of reducing power consumption. When used as a 32-inch TFT LCD backlight, the brightness is 10.000cd/m2, which is about 60W. Compared with cold cathode tube (CCFL) and light emitting diode (LED), the power consumption is lower. It is estimated that when it reaches the practical level in 2006, the target is a realistic brightness of 30000 CD/m2 and a service life of 50,000 hours. In application, it is a small and medium-sized LCD panel for mobile phones and vehicle-mounted terminal products, and plans to develop into large-scale products such as large-screen LCD TVs and lighting equipment in the future.