A field emission display (FED) is a flat panel display technology based on field emitting cathodes to bombard phosphor coatings as the light emissive medium.
Field emission display technology is similar to that of cathode ray tubes, however it has the potential to reduce display thickness to a few millimeters. Instead of a single electron gun, a field emission display (FED) would use an array of fine metal tips or carbon nanotubes (which are the most efficient electron emitters known) for emission of electrons (field emission), with many of them positioned behind each phosphor dot. Because of emitter redundancy, FEDs basically could overcome the effect of dead pixels as known from LCDs even if 20% of the emitters fail. Sony is researching FED because it is the flat-panel technology that comes closest to matching the picture of a CRT.
FEDs are supposed to be energy efficient and they could provide a flat panel technology that features less power consumption than existing LCD and plasma display technologies. They are also claimed to be cheaper to manufature, as they have fewer total components and processes involved. As of yet, however, there are no commercial devices available on the market, although small demo panels have been produced in the past.
A similar technology scheduled to be commercialized in the near future is the SED (surface-conduction electron-emitter display), a variant of FED technology. Whereas FED uses a 'Spindt tip' semi-conductor or carbon nanotube emitter, with multiple redundant emitters per area of display[1], SED uses an emitter array based on palladium oxide laid down by an inkjet or silk-screen process.[2]. SED has been considered to be the variant of FED that is feasible to mass-produce, however, even in 2008 no commercial SED display products are made available by the industry.
In 2001, Candescent had spent $600 million on producing FEDs with non-carbon material, but it was abandoned, with assets sold to Canon in August 2004, two months after filing for voluntary reorganization under Chapter 11. The UK company Advance Nanotech, in collaboration with the University of Bristol, has developed a similar panel that relies on specially doped diamond dust. The first 1000 Carbon Nanotechnologies was set to production in late 2006 by Sony. [3]
Nano-emissive display is the name given by Motorola for field emission display. A prototype model was demonstrated by Motorola in May 2005. Nano-emissive display (NED) is Motorola's term for their Carbon Nanotubes (CNTs)-based display technology. In the meantime, Motorola stopped all FED related activities.
Futaba Corporation is actively involved in FED development and production as of 2008.
Potential disadvantages
Although physically simple, actual operation of field emitters in a working device is anything but simple. Field emitters depend on high electric field strength to tear electrons from the surface. Instead of very high voltages, FEDs use very small radii – atomic lattice size – and element spacing for cathodes. This small size renders the cathodes susceptible to damage by ion impact. The ions are produced by the high voltages interacting with residual gas molecules inside the device. FEDs require high vacuum levels which are difficult to attain: the vacuum suitable for conventional CRTs and vacuum tubes is not sufficient for long term FED operation. Intense electron bombardment of the phosphor layer will also release gas during use.
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