LCDs and OLEDs and E-Ink, Oh My!

I was reading an article about how campers want to take their media, including TV, with them into nature. And that article prodded me to think a little bit more about portable video products. The ideal video product for campers:

• is lightweight,
• is small when packed away but still has a large screen when used,
• has long play time.

You can think about a lightweight screen that you roll up and transport in a poster tube. Just unfurl the display and you're ready to watch video. This not-so-new concept would be the ultimate product for many uses though. Not just camping.

What type of display is best-suited for such a product? A Liquid Crystal Display (LCD), OLED (Organic Light Emitting Diode) Display or electronic ink (e-ink) display? I'm betting on OLED displays.

(+/-)read why

If you're reading this entry on a thin monitor, then you're reading text on a Liquid Crystal Display (LCD). Your mobile phone probably has an LCD too. LCDs are great, but they:

• require significant power: You can't use your battery-powered laptop all day to surf the Web. And the biggest power hog on your cell phone is your display, as I discussed here. LCDs require constant backlight, which takes a lot of power.
• are difficult to read in direct sunlight: When you use your mobile phone outside on a sunny day, you often have to turn so that your body blocks the sun from shining on the display.
• are inflexible: You have no chance of rolling your LCD monitor up (or folding it) and carrying it in a poster tube. You should be able to slide out individual modular LCDs to create a larger screen.

LCD technology has matured significantly since James Fergason's company first marketed improved LCDs in 1971 (source). I don't see LCDs overcoming the first obstacle since the backlight is an inherent feature of the technology.

Have you used your MP3 player today? If so, there's a 40% chance that you used an Organic Light Emitting Diode (OLED) display instead of an LCD. OLED displays are relatively young--they were first marketed in 2000 in a Pioneer car radio (source), but they have quickly gained market share. OLEDs are super, but they:

• require power to be seen: Something emits light; so that something needs power. Power must be applied as long as you want to see that color, but the power requirements for OLEDs are much smaller than LCDs.
• are moisture sensitive: This disadvantage wouldn't matter if we weren't talking about flexible screens. It's easy to make a rigid moisture barrier, but a flexible water barrier isn't quite as easy. It's doable, but not easy.
• degrade at different rates: The fact that OLEDs degrade at all isn't necessarily a good thing, but the lifetime of an OLED is still longer than the lifetime of most consumer products these days. Degradation shouldn't be a big deal. But if the OLED colors degrade at different rates, then the screen colors will shift a little bit over time.

You can read more about OLEDs here.

Did you see the new flexible clock that Citizen is producing? It uses E-ink technology. E-ink is starting down the same pathway as James Fergason--just 30 years later. Start with watches and clocks and quickly migrate into other types of displays. The Citizen clock presents black numbers, but E-ink has already demonstrated a color display in mid-2002.

If E-ink is 30 years later than LCDs, why bother? The single most important feature of E-ink displays is the fact that you don't need to continuously apply power to show an image. Once an image is shown on an E-ink display, that image remains visible. Power is only needed to change the image. Think about a Magna-Doodle. You use a magnetic stencil to pull black particles toward the screen so that they're visible. Once you can see them, you don't need to use the stencil anymore. E-ink works the same way.

Despite this huge power advantage over competitors and the fact that E-ink has demonstrated flex displays, there is still one major obstacle. E-ink displays have a slow refresh rate. Particles have to move through a fluid to become visible (or invisible). That takes time and power. If you don't use a lot of power, it takes more time. Without having more intimate knowledge of E-ink technology, I'm guessing that this will always be an issue inherent in the technology. (Kind of like the backlight issue for LCDs.)

The good news is that developers will finally have the chance to play with E-ink technology using kits, available here. Kits start to ship in November. After developers play with the technology, we'll have a better idea about the benefits and limitations.

I think that viewers will sacrifice a little color change over time in exchange for fast refresh rates so that the picture isn't jumpy. And this guess favors OLED displays over E-ink displays.

I also think that E-ink displays will have an immediate market niche for which it is far superior to any other display technology. Flexible displays with images that don't need to change more than a once a minute. Electronic store signs. Billboards. Digital picture frames. Once you show an image, you don't need power to keep the image visible. And that's huge! Imagine that picture frame on the wall over your mantle. You can program the frame to show a different image everyday. Since you aren't changing the image, it doesn't require a lot of power. Throw a little solar cell nearby and you don't even need batteries anymore.