Surface-conduction Electron-emitter Display is a new type of flat-panel display technology that utilizes the collision of electrons against a phosphor-coated screen to emit light similar to a cathode ray tube but, instead of having one electron beam hitting the whole screen, each pixel has its own emitter. It’s like every pixel of a SED display is a miniature CRT, resulting in a discrete arrangement that will allow SED screens to behave like a digital display. It has all the advantages of cathode ray tube (brightness and contrast levels, viewing angle) and none of the drawbacks of current flat panel display technologies.
The main advantage of SED’s compared with LCD’s and CRT’s is that it can provide with a best mix of both the technologies. The SED can combine the slim form factor of LCD’s with the superior contrast ratios, exceptional response time and can give the better picture quality of the CRT’s. The SED’s also provides with more brightness, color performance, viewing angles and also consumes very less power. Moreover, the SED’s do not require a deflection system for the electron beam, which has in turn helped the manufacturer to create a display design, that is only few inches thick but still light enough to be hung from the wall . All the above properties has consequently helped the manufacturer to enlarge the size of the display panel just by increasing the number of electron emitters relative to the necessary number of pixels required.
SED is 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. As far as the specs go, this is one hot technology.
Canon began SED research in 1986. Their early research used PdO electrodes without the carbon films on top, but controlling the slit width proved difficult. At the time there were a number of flat-screen technologies in early development, and the only one close to commercialization was the plasma display panel (PDP), which had numerous disadvantages – manufacturing cost and energy use among them. LCDs were not suitable for larger screen sizes due to low yields and complex manufacturing.
In 2004 Canon signed an agreement with Toshiba to create a joint venture to continue development of SED technology, forming "SED Ltd." Toshiba introduced new technology to pattern the conductors underlying the emitters using technologies adapted from inkjet printers. At the time both companies claimed that production was slated to begin in 2005. The 2005 target was not met, and several new targets since then have also slipped by. This failure to meet mass-production deadlines goes as far back as 1999, when Canon first told investors of its intentions to immediately begin mass-producing the technology.
The formation of SED Inc. in 2004 was certainly an acknowledgement by Canon that, no matter how good their engineering and technical prowess, they would have a difficult time manufacturing and mass-marketing this technology on their own. While CES 2005 was the moment for SED to prove its technology was alive and kicking, CEATAC 2005 and CES 2006 showed that SED Inc. could make multiple versions of that same 36-inch display with repeatable image quality and consistency Both Canon and Toshiba started displaying prototype units at trade shows during 2006, including 55" and 36" units from Canon, and a 42" unit from Toshiba. They were widely lauded in the press for their image quality, saying it was "something that must be seen to believe[d]. During the 2006 Consumer electronics show in Las Vegas, Nevada. Toshiba showed working prototypes of SEDs to attendees and indicated expected availability in mid-to-late 2007. At the 2007 Consumer Electronics Show, no SED displays were to be found on The show floor. This led many analysts to speculate that the technology would never reach the consumer market.
October 2006, Toshiba's president announced the company plans to begin full production of 55-inch SED TVs in July 2007 at its recently built SED volume-production facility in Himeji.
In December 2006, Toshiba President and Chief Executive Atsutoshi Nishida said Toshiba was on track to mass-produce SED TV sets in cooperation with Canon by 2008. He said the company planned to start small-output production in the fall of 2007, but they do not expect SED displays to become a commodity and will not release the technology to the consumer market because of its expected high price, reserving it solely for professional broadcasting applications. The cost of a 55” SED TV would be USD 10000.
Applied Nanotech, a subsidiary of Nano-Proprietary, holds a number of patents related to FED and SED manufacturing. They had sold Canon a perpetual license for a coating technology used in their newer carbon-based emitter structure. Applied Nanotech claimed that Canon's agreement with Toshiba amounted to an illegal technology transfer, and a separate agreement would have to be reached. They first approached the problem in April 2005.
Canon responded to the lawsuit with several actions. On 12 January 2007 they announced that they would buy all of Toshiba's shares in SED Inc. in order to eliminate Toshiba's involvement in the venture. They also started re-working their existing RE40,062 patent filing in order to remove any of Applied Nanotech's technologies from their system. The modified patent was issued on 12 February 2008.
On 22 February 2007, the U.S. District Court for the Western District of Texas, widely ruled in a summary judgment that Canon had violated its agreement by forming a joint television venture with Toshiba.[\ However, on 2 May 2007 a jury ruled that no additional damages beyond the $5.5m fee for the original licensing contract were due.
25 July 2008, the U.S. Court of Appeals for the 5th Circuit reversed the lower court's decision and provided that Canon's "irrevocable and perpetual" non-exclusive licence was still enforceable and covers Canon's restructured subsidiary SED. On 2 December 2008, Applied Nanotech dropped the lawsuit, stating that continuing the lawsuit "would probably be a futile effort".
In spite of their legal success, Canon announced at the same time that the financial crisis of 2008 was making introduction of the sets far from certain, going so far as to say they would not be launching the product at that time "because people would laugh at them".
Canon officially announced on 25 May 2010 the end of the development of SED TVs for the home consumer market, but indicated that they will continue development for commercial applications like medical equipment. After considerable time and effort in the early and mid-2000s, SED efforts started winding down in 2009 as LCD became the dominant technology. On 18 August 2010, Canon decided to liquidate SED Inc., a consolidated subsidiary of Canon Inc. developing SED technology, citing difficulties to secure appropriate profitability and effectively ending hopes to one day see SED TVs in the living room.
3.1 Creating the picture
SED is a display device that includes an electron-emitting device which is a laminate of an insulating layer and a pair of opposing electrodes formed on a planar substrate. A portion of the insulating layer is between the electrodes and contains fine particles of an electron emitting substance, that portion acting as an electron emitting region. Electrons are emitted from the electron emission region by applying a voltage to the electrodes, thereby stimulating a phosphorous to emit light.
A conventional cathode ray tube (CRT) is powered by an electron gun, essentially an open-ended vacuum tube. At one end of the gun electrons are produced by "boiling" them off a metal filament, which requires relatively high currents and consumes a large proportion of the CRT's power. The electrons are then accelerated and focused into a fast-moving beam, flowing forward towards the screen. Electromagnets surrounding the gun end of the tube are used to steer the beam as it travels forward, allowing the beam to be scanned across the screen to produce a 2D display. When the fast-moving electrons strike phosphor on the back of the screen, light is produced. Colour images are produced by painting the screen with spots or stripes of three coloured phosphors, one each for red, green and blue (RGB). When viewed from a distance, the spots, known as "sub-pixels", blend together in the eye to produce a single coloured spot known as a pixel.
An SED-TV creates a picture in much the same way (Fig.3.1). It's essentially a flat panel television that uses millions of CRTs instead of one electron gun. These miniature CRTs are called Surface Conducting Electron emitters (SCEs) (Fig.3.2). A set has three SCEs for every pixel -- one each for Red, Green and Blue (Fig.3.3). As with a CRT set, the inside of an SED-TV is a vacuum. All of the SCEs are on one side of the vacuum, and the phosphor-coated screen is on the other. The screen has a positive electrical charge, so it attracts the electrons from the SCEs. A widescreen, high definition set can have more than 6 million SCEs arranged in a matrix, and each one controls the Red, Green or Blue aspect of one pixel of the picture. Rather than directing
electrons to create the image one row at a time, the matrix activates all the SCEs needed to create the picture virtually simultaneously.
The SED replaces the single gun of a conventional CRT with a grid of nanoscopic emitters, one for each sub-pixel of the display. The surface conduction electron emitter apparatus consists of a thin slit across which electrons jump when powered with high-voltage gradients. Due to the nanoscopic size of the slits, the required field can correspond to a potential on the order of tens of volts. A few of the electrons, on the order of 3%, impact with slit material on the far side and are scattered out of the emitter surface. A second field, applied externally, accelerates these scattered electrons towards the screen. Production of this field requires kilovolt potentials, but is a constant field requiring no switching, so the electronics that produce it are quite simple.
Each emitter is aligned behind a coloured phosphor dot, and the accelerated electrons strike the dot and cause it to give off light in a fashion identical to a conventional CRT. Since each dot on the screen is lit by a single emitter, there is no need to steer or direct the beam as there is in an CRT. The quantum tunnelling effect that emits electrons across the slits is highly non-linear, and the process tends to be fully on or off for any given voltage. This allows the selection of particular emitters by powering a single horizontal row on the screen and then powering all of the needed vertical columns at the same time, thereby powering the selected emitters. Any power leaked from one column to surrounding emitters will cause too small a field to produce a visible output; if that emitter was not turned on the leaked power will be too low to switch it, if it was already on the additional power will have no visible effect. This allows SED displays to work without an active matrix of thin-film transistors that LCDs and similar displays require, and further reduces the complexity of the emitter array. However, this also means that changes in voltage cannot be used to control the brightness of the resulting pixels. Instead, the emitters are rapidly turned on and off using pulse width modulation, so that the total brightness of a spot in any given time can be controlled.