In order for a display technology to be suitable for large-scale (on the order of wallpaper) integration into the home, it has to fulfill some rather exacting performance requirements. It has to be energy efficient, flexible enough to withstand spills and dings, have good picture quality, and be able to perform in an environment with direct sunlight. Surveying today's technology, we are pretty far off from electronic wallpaper, though some excellent new smaller-scale devices have emerged.

Requirements of new display technologies
1. Efficient energy use
2. Flexibility- where can it be used? How much punishment can it take?
3. Performance- brightness, color accuracy, contrast, refresh rate, show up in direct light

Technologies Currently In the Market:

LCD Displays
LCD's (liquid crystal displays) are the most common form of flat-panel display available today. They are used in an enormous variety of devices, ranging from the readout on your digital watch to laptop displays to desktop flat panel displays. Standard LCD construction is basically a sandwich of transistors, liquid crystals, and color filters between two pieces of polarized glass, which are oriented at 90 degrees to each other. The active part of the display is the liquid crystal layer; each crystal's orientation is controlled by a transistor (transistors, in some cases). The polarized light shining through the rear polarizer from a back light is twisted 90 degrees or let to pass through straight depending on the orientation of a the crystal it comes in contact with. Light that was twisted by the crystals passes through a color filter and out through the second piece of glass; light that was not twisted is blocked.
light being twisted and passed throughlight remaining straight and being blocked
The main advantages of LCD's over standard CRTs (cathode ray tubes, the kind of device that drives a normal monitor or TV) are their low power consumption and their light weight and thin profile. They have several disadvantages though; compared to a CRT their colors are less bright, they have less contrast, and their viewing angle is very limited. Also, since the number of crystals and hence pixels is set when they are manufactured, the resolution they are manufactured at is the only resolution they can ever be used at without some sort of software interpolation which degrades image quality. Liquid crystals also respond slower than the electron guns in a CRT, making the screens refresh rate much lower than a standard CRT and occasionally creating "ghosting" problems. Their complicated and delicate construction makes them very difficult to manufacture, hence very expensive. Finally, since they are an emissive display (they emit colored light to create images), they cannot be used in direct sunlight or bright ambient lighting conditions.
Several technologies are in development to correct these problems. Toshiba is developing a LCD that works by reflecting ambient light rather than using a back light. There is also a lot of research going on with low temperature polysilicon substrates that would allow both the transistors and liquid crystals be bound to the same substrate, greatly reducing manufacturing complexity.
In final assessment, however, I do not feel that LCD's will ever make a practical large-scale (wall size or bigger) display device, because of their manufacturing complexity, their fragility (two glass layers) and finally because they rely on emissive display.

Plasma Displays
Gas plasma displays work much the same way LCD's do, but instead of liquid crystals passing light through a colored filter, they contain noble gasses that emit ultraviolet light when excited by the transistors that in turn makes some phosphors glow red, green, or blue, creating pixels. They are much easier to manufacture large than are LCD's, but cannot be made much smaller than 40". They have much wider viewing angles, but consume much power. They also have the drawback of color banding in low-contrast scenes. Other than that, their drawbacks and benefits are much the same as LCD's. animation of how a plasma display works

Field Emission Displays
FED's work using the exact same principal that a CRT does (electrodes striking a phosphor causing it to luminesce), but simply replace the big heavy electron guns used in classic CRTs with a thin array of hundreds of tiny little cathode tubes. The tubes are positioned in a flat plane a few millimeters away from the phosphor surface. The end result is a display that is as bright and fast as a CRT but as thin as a LCD. They also use less power than a normal CRT. They still, however, have the drawbacks of being inflexible and emissive, keeping them from being suitable for truly large-scale display. Also, I could not find examples of FED's larger than 5.6" or with resolutions greater than 320x240, leading me to believe they are difficult to manufacture at large scale or precisely. field emission display diagram

Technology in the not terribly distant future
These new technologies offer several exciting new advantages over existing ones. Unlike most existing display tech, LEP's and Digital INK work on flexible substrates, meaning they can be configured into non-planar shapes. Also, since they are no longer constrained to being sandwiched between glass plates, they offer the possibility of being much tougher, cheaper products.

Microdisplays
"Microdisplays" are tiny reflective LCD panels made by a company called, oddly enough, MicroDisplay. Their main advantages are that they are tiny, reflective rather than emissive, much brighter and with a wider viewing angle than today's LCD's, and since they manufactured right onto a silicon control back plate rather than between glass and a layer of transistors, they are much easier and cheaper to manufacture. They show promise as cheap and effective displays for use in wearables and other little gadgets like cell phones, in tiny little projectors. The only drawback right now is that the maximum resolution available is 1024x768 pixels, good enough for watching TV but not really very high. Considering that is on a display that is only .63" across, however, that is quite good.
Microdisplays could be useful in tiny projectors that could easily be built into ceiling panels or behind walls to use as display devices in the home.diagram of construction of microdisplay

LEPS
LEP's, or Light Emitting Polymers, are exactly what the name says; they are polymers that, when excited by an electrical current, give off light. Red, green, and blue polymers have all been successfully manufactured, and a prototype display demonstrated. They are turned into a display by ink jet printing them onto a transistor matrix like those found in LCD's, but unlike LCD's, printing them on is more or less the last step. Since they emit colored light, none of the mess and expense associated with the layers of polarized glass, color filters, and liquid crystals that a LCD uses are needed at all. LEP's are as efficient as today's LED's, which are very efficient. They have the potential to be used as flexible, cheap, and tough displays. Their only drawback is that they still depend on emitting light to create an image, making them impractical in daylight or other brightly lit environments. They are a very young technology, and it will be several years before real consumer products start appearing. cross section of LEP display

Digital Ink
By far the most exciting, and most radical, new display technologies is the digital ink being developed by E Ink, a Media Lab spin-off company. The driving idea behind their research is to create as close as possible a digital analogue (ha ha) to "real" ink; a substance that can be printed onto many different media types, that is reflective rather than emissive, thin and lightweight, and as high resolution as print. While the technology is still a ways off from replacing more traditional ink, it offers some very exciting possibilities. The basic idea behind it is quite simple; a circuit is printed, using conductive ink, onto a substrate (some sort of paper or plastic or whatever); that circuit pattern is then coated in the "digital ink," which consists of tiny clear microcapsules containing a mixture of colored dye and white particles. The particles are charged, so that when the driver circuit underneath them fires the particles are drawn to the bottom of the capsule, forcing the dye to the top. Therefore, what one sees from the top is the color of the dye. If the charge is reversed, the particles force themselves to the top and the dye to the bottom, changing the perceived color of the surface from the color of the dye to the white of the particles. By putting down a pattern of capsules with red, green, and blue dyes, a color display can be created.e-ink diagram

 

Image Credits
LCD images courtesy of Tom's Hardware Guide
Plasma display image courtesy of Mohit Tinani
Field emission image courtesy of PixTech, Inc.
Microdisplay image courtesy of MicroDisplay, Inc.
LEP image courtesy of Cambridge Display Technology, Ltd