Here's another indication that the ink-jet future is upon us (and it's likely to be a more palatable example than the last one): Cambridge Display Technologies is now able to produce 14" laptop displays by printing the organic polymer LED material using ink-jet tech. Already appearing in small form on cell phones and other handheld devices, organic LEDs have some real advantages over the LCD technology in your laptop or flat-panel screen:

OLED is viewed as a potential successor to liquid crystal displays, used in many flat-panel TVs and computer monitors. Materials in an OLED display emit light when an electrical current is applied. The displays can function without a backlight, which cuts down on power consumption, screen thickness and cost. OLED displays also offer higher resolution than LCDs.

The screens, potentially, also cost less to produce. Cambridge sprays its pixels on with multi-nozzle inkjet printers. The printers can sport 128 nozzles and come from a company called Litrex, which is half owned by Cambridge.

Another big advantage of organic polymer electronics in general is that they have a much lower environmental footprint in terms of energy required to produce them and toxic material content, in comparison to LCDs and traditional (read: obsolete) CRT technologies.

The Cambridge Display website also holds some very useful pages describing and explaining how organic polymer electronic materials work, and their current and potential applications. The same kinds of technology going into organic displays can produce organic photovoltaic materials; like OLEDs, organic photovoltaics are in principle less-costly to produce, have greater flexibility of use, and have a much lower environmental footprint than traditional technologies. Overall, organic polymer electronics look to have significant green advantages over current standard technologies.

OLEDs do have some downsides, which is why they aren't already overtaking LCDs. Until very recently, blue OLEDs with a usable brightness and lifetime were very hard to make; even now, they have lower emissive lifespans than other OLED colors. In general, when used at the level of brightness typical of televisions and laptop displays, OLEDs have shorter lives than LCDs (lifespan refers to the time it takes for brightness to drop to half). Organic electronics in general tend to be much slower than silicon-based electronics, although OLEDs are actually faster than LCDs (so fast-moving images don't "smear"). Finally, although the production costs using ink-jet systems will eventually beat standard LCD costs, OLEDs remain relatively expensive to make.

Still, this is very much a sign of things to come. OLED displays can work on flexible ("roll-up") backing, and coupled with the lower power requirements, they will open up new possibilities for form and function of information devices. The ink-jet production method is likely applicable to a wide array of organic electronic materials, and as it matures, should dramatically lower production costs. In principle -- and this is very much conjecture -- desktop fabber systems would at some point be able to add electronic, power generation and display function to their 3D products.

(Via Engadget)

How the haystack do you turn individual pixels on and off on these things? Electro-luminesence I buy, sure, but how exactly are the electrical impulses fed to the display?

Posted by: Rektide on November 12, 2005 11:56 AM

Jamais,
Ink jetting as a printing technique is highly constrained by the need for a very low viscosity ink. There is no fundamental reason one could not scale down and add digital control to other printing techniques such as electrostatic printing (Xeroxing) or some form of contact printing. By keeping the options open on what printing technique a 3-D printer uses you can reduce the practical constraints that are imposed when you use ink jets. (Electrostatic printing uses solid particles, contact printing can handle viscose fluids)

Posted by: jim moore on November 12, 2005 8:00 PM

Rektide-- OLEDs, like LCDs, are controlled by a backplane of electronics, usually in conjunction with external driver chips. The backplane is traditionally made of glass (these days, 0.7mm or 0.5mm thick) with amorphous or polysilicon transistors. Each pixel on an active-matrix display is individually controllable by a transistor circuit at each pixel, plus row and column drivers for the matrix. ("Passive matrix" means there are only row and column drivers, no transistors).

One thing about driving OLEDs-- Unlike LCDs, you cannot get away with just one transistor per pixel. You must use at least 2, and the best designs these days have 3 to 5, plus some capacitors. This is a heck of a lot of electronics to attach to each pixel, which really cuts down the aperture ratio (how much light gets out--- basically, the electronics block part of the light). It is possible to shine the light out the other side of the panel (not through the electronics), but this adds complication to the manufacturing.

In the future, plastic backplanes might be possible to allow flexing. This would then require switching to organic electronics rather than silicon. We're not technically capable of it quite yet, but it will come someday.

(The reason OLEDs are faster than LCDs doesn't have to do with the electronics, but with the materials themselves. LCDs are light valves that rely on changing the twist of the liquid crystals such that they pass or block light. Twisting takes a few milliseconds up to hundreds of milliseconds, depending on the type of LC. OLEDs are totally different. They create their own light, and the emission occurs in tens of microseconds).

Posted by: Kim on November 13, 2005 7:18 AM