ABSTRACT
A surface-conduction electron-emitter display (SED) is a flat panel color television technology currently being developed by a number of companies. Surface-conduction Electron-emitter Displays are a new, emerging technology co-developed by Canon and Toshiba Corporation. The hope for this technology is a display which reproduces vivid color, deep blacks, fast response times and almost limitless contrast. In fact, if you take all of the claims made by the backers of SED you would think that there should be no reason to buy any other type of display. An SED display is very similar to a CRT (and now we come full circle) in that it utilizes an electron emitter which activates phosphors on a screen. The electron emission element is made from an ultra-thin electron emission film that is just a few nanometers thick. Unlike a CRT, which has a single electron emitter that is steered, SEDs utilize a separate emitter for each color phosphor (3 per pixel, or 1 per sub-pixel) and therefore do not require an electron beam deflector (which also makes screen sizes of over 42″ possible). After considerable time and effort in the early and mid-2000s, SED efforts started winding down in 2009 as LCD became the dominant technology. In August 2010, Canon announced they were shutting down their joint effort to develop SEDs commercially, signalling the end of development efforts. SEDs are closely related to another developing display technology, the field emission display, or FED, differing primarily in the details of the electron emitters. Sony, the main backer of FED, has similarly backed off from their development efforts.Canon debuted an SED display prototype at the la Defense in Paris in October 2005. The specs referenced a < 1ms response time, 100,000:1 contrast ratio, brightness of 400 cd/m^2, and 180 degree viewing angle in all directions. Actual shipping models are expected to fist be released by Toshiba in 2007. Pricing is expected to be less than LCD and plasma for the same size Main advantages of SED display is
• CRT-matching black levels
• Excellent color and contrast potential
• Relatively inexpensive production cost
• Wide viewing angle
Modern SEDs add another step that greatly eases production. The pads are deposited with a much larger gap between them, as much as 50 nm, which allows them to be added directly using technology adapted from inkjet printers. The entire screen is then placed in an organic gas and pulses of electricity are sent through the pads. Carbon in the gas is pulled onto the edges of the slit in the PdO squares, forming thin films that extend vertically off the tops of the gaps and grow toward each other at a slight angle. This process is self-limiting; if the gap gets too small the pulses erode the carbon, so the gap width can be controlled to produce a fairly constant 5 nm slit between them.
LCDs do not directly produce light, and have to be back-lit using cold cathode fluorescent lamps (CCFLs) or high-power LEDs. The light is first passed through a polarizer, which cuts out half of the light. It then passes through the LCD layer, which selectively reduces the output for each sub-pixel. In front of the LCD shutters are small colored filters, one for each RGB sub-pixel. Since the colored filters cut out all but a narrow band of the white light, the amount of light that reaches the viewer is always less than 1/3rd of what left the polarizer. Since the color gamut is produced by selectively reducing the output for certain colors, in practice much less light makes it through to the view, about 8 to 10% on average