Electronic Design

Full-Color Displays Will Dominate In Cell Phones Of The Future

If you've ever been overwhelmed by the large array of flavors at Baskin-Robbins, then you know what it's like for a newcomer who faces the over 30 versions of displays. Fortunately, we can thank Jyrki Kimmel from the Nokia Research Center, in Tampere, Finland, for his largesse in this area. As the center's senior research manager for displays and optics, Kimmel spoke at the Society for Information Display (SID) Symposium in Long Beach, Calif. recently. He shared his views on choosing displays for portable communication devices.

Kimmel began by noting that digital convergence is transforming the market landscape. He believes this will bring about a huge increase in various multimedia, which will seize a significant measure of the available bandwidth.

What this means is that there will be a blurring of today's distinct devices: digital cameras, TVs, cinemas, telephone message boards, and PCs. And they may all merge into a single portable communication device. Built-in cameras may become commonplace. It's also possible that the telephone function, a central part of contemporary cell phones, will become a mere add-on. So the cellular phone as we now know it may no longer be recognizable. If Kimmel's prognosis is accurate, how will it affect displays?

For starters, they'll become larger, commanding a greater amount of the device's viewing area. They'll also be able to run at video rates while retaining low power consumption. (The latter isn't so easy considering power consumption varies directly with frequency.) In addition, displays will be in full color.

Cell phones in Japan—where Nokia commands just 1% of the market—are already in color. (Not to worry, Nokia shipped 78 million phones last year to the rest of the world.) By 2001, Kimmel expects color displays to populate the majority of Japanese phones.

Unlike today's cell phones, the display is expected to dominate a major portion of the user's interface. This is because it will deliver video as well as perform the functions required by today's cell phones.

According to Kimmel, a number of LCD varieties predominate in many classes of portable terminals. These include super-twisted nematics (STNs) in e-books, film-compensated STNs (FSTNs) in mobile phones, thin-film-transistors (TFTs) in web browsers, and reflective TFTs in PDAs.

As for the future, Kimmel believes organic light-emitting diodes (OLEDs) hold great promise. These devices are thin, relatively inexpensive, and easy to manufacture. Plus, they consume little power and can be mounted on plastic substrates. There are some issues that have yet to be overcome, however. The fact that OLED's of the three different primary colors degrade at varying rates remains one of them.

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