The standard cathode ray tube (CRT) based monitor, display or television screen has been almost completely eclipsed by liquid crystal displays (LCD) and flat screen plasma displays. Advances in nanotechnology could see these new screens dumped on the street for junk collection sooner than anyone realises.
Types of Screen
The type of screen depends upon the technology used and much of the technology tends to be a closely guarded secret. Leading display technologies include Field Emission Displays, carbon nanotube based screens and electrochromatic screens. Another interesting technology is electronic paper.
Field Emission Displays
Field Emission Displays (FED) and carbon nanotube screens are high-definition colour displays with CRT screen like vibrant colour, rich contrast and fast response – but they are flat. These screens actually work similarly to a conventional CRT screen. CRT screens use a single electron ‘gun’ to scan back and forth across and down the screen to selectively illuminate a phosphor coated screen. Both FED and carbon nanotube screens shoot electrons from an array of millions of electron emitters at a phosphor coated screen. The electron emitting array in FEDs are made from tiny sharp metal points. FEDs have been around since the 1990s but manufacturing large screens was expensive and difficult, plus the screens used extremely high voltages. Several manufacturers are reporting that they have developed new technologies that overcome these difficulties ad that FEDs are very close to hitting the market.
Carbon Nanotube Screens
In carbon nanotube screens the metal point based electron arrays of FEDs are replaced with a self assembled array of carbon nanotubes. The tips of each of these emitters is only 3 nanometers in diameter.
Electrochromatic screens are composed of a sandwich of layers. The outer layers are glass and the inner layers electrodes, ion storage layers and the electrochromatic layer. Applying electricity moves electrons from the ion layers into the electrochromatic layer changing it’s colour or from clear to dark. Selective switching allows an image to be displayed. New developments have resulted is electrochromatic materials that only alter their state with an electric signal. The screen can be turned off and still retain the image. Alternatively only the area on the screen that changes will be drawing electricity. The result is a dramatic reduction in the amount of power required to run a screen.
Electronic paper or electronic ink is currently a black and white only technology. It uses a layer of special microcapsules sandwiched between two large, flat electrodes. At least one of these electrodes is transparent. The capsules too are transparent and contain a clear fluid plus charged black pigment and white pigment holding the opposite charge. Depending on the charge applied to each capsule by the electrodes, either the black or the white pigment is attracted to the surface. Each capsule then becomes a single black or white pixel. When the charge is removed from the electrode the microcapsule retain their state and therefore the image on the ‘electronic paper’.
The sky could really be the limit for these screens. Screens 50 inches across the diagonal and less than 1 inch thick have been produced using some of these technologies and it is expected that these technologies will result in high definition stadium screens and video billboards.
The price of these screens is anyone’s guess but some manufacturers have suggested that these screens will hit the market with “disruptive pricing” significantly lower than LCD and plasma screens.
The base technology for FED and carbon nanotube screens is well developed and some manufacturing steps borrow heavily from LCD, plasma and CRT production. This means the path from concept to market is extremely short. At the time of writing several plants were under construction throughout Asia to build carbon nanotube based displays. Basic black and white electrochromatic screens are already available.
Even though these displays are yet to hit the market, they may already be using redundant technology. Researchers are now investigating the development of screens that are based on Organic Light-Emitting Devices (OLED) and nanocrystals.