Printed FEDs promise to undercut plasma panels

Printed FEDs promise to undercut plasma panelsSteve Bush
After last week’s look at silicon LEDS, I thought I would explore some of the other up-and-coming emissive display technologies.
The first is from Oxfordshire’s Printed Field Emitters (PFE).
It has been working on an electron emissive material to go at the back of field emission displays (FEDs) as an alternative to micromachined Spindt cathodes, diamond films and diamond-like carbon films.
The advantage of its material, claims the company’s Dr Richard Tuck, is that it can be applied using a printer rather than chemical vapour deposition or other ‘high-tech’ process.  
  Printed light … Oxfordshire company Printed Field Emitters (PFE) is developing electron-emissive materials, for use in field emission displays (FEDs), that can be printed. As with all FEDs, electrons hit a phosphor to create light. The picture shows a three-colour sample under test.  
 
So keen is the company on printing that it is also looking at printing the spacers essential for preventing FEDs imploding.
Other FED companies are looking at more elaborate schemes, for instance, Candescent is using short glass fibres stood on end. Printed spacers are not necessarily as fine as fibres, but large area displays – where PFE is aiming its technology – have big pixels which can accommodate fatter spacers.
The only non-printing process, according to Tuck, is a single self-aligning whole-panel lithographic stage used to open-up emission sites.
Tuck reckons that the 1m diagonal hang-on-the-wall TV market is the one to go for and claims printed FEDs will undercut the price of similarly-sized plasma panels. He says panel costs will not differ between types, but drive electronics will be considerably cheaper for printed FED panels as lower voltage, lower frequency signals are required.
At the other end of the size scale, the confusingly named FED Corporation has just licensed organic light emitting diode (OLED) technology from Kodak.
FED Corp began life five years ago as a field emission display company. Three years ago it changed horses to LCD and OLED technology when it realised FEDs were less suitable as micro-displays, its target market. Micro-displays are predicted to be a fast growing market as games headsets and wearable computers become more popular.
Now FED Corp aims to sample silicon-backplane miniature LCDs this year and silicon-backplane miniature OLED displays soon afterwards.
Many companies are in production or close to production with silicon-LCDs, but FED Corp sees an advantage in moving to silicon-backed OLED displays. “We think a LCD headset display will use around 2W of power. An OLED version will probably get down to 0.5W,”said company executive v-p Susan James.
OLEDs are sometimes called molecular emitters, or small molecule emitters, to differentiate them from light-emitting polymer (LEP) displays of the type that Cambridge Display Technology (CDT) is working on and licensing.
OLEDs and LEPs have broadly similar characteristics and both CDT and Kodak have licensees who are making equipment with their technology. In the OLED case it is Pioneer which is using organic LEDs in car radio displays. OLEDs, from Kodak, have been around for the longest and this is what the company is banking on to promote its technology in the market. OLEDs can also provide a long-life blue emitter, something that the LEP brigade is only just testing. On the other hand OLEDs need to be vacuum deposited, whereas LEPs can be printed.


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