Flexible Displays Set To Go Mainstream

However, LCDs don't operate well on a bent substrate. In a conventional LCD, two glass plates sandwich a TFT layer embedded in amorphous silicon. Using a flexible polymer film instead of glass affects the LCD's image quality. This quality depends on the cell gap between the polymers and distorts the image, making it very difficult to view at different angles.

OLEDs are another competitive technology (Fig. 6). Based on the electroluminescence of organic compounds, OLEDs are brighter than LCDs. They also offer wider viewing angles and faster response times. Unlike LCDs, OLEDs don't need a backlighting source, so they're thinner and lighter than LCDs, too. These are crucial attributes for many military applications, where soldiers are otherwise burdened with loads of electronic gear.

One of the biggest attributes of OLEDs is their low power dissipation. Bi-stable OLEDs draw power only when they're on, which means lower power dissipation and longer battery life—obviously very attractive attributes for portable electronics. OLEDs are also more durable than LCDs. They're about 10 times more impact-resistant than plastic-substrate LCDs and 100 times more than glass LCDs.

OLEDs have some important drawbacks, though. They require a strong barrier against moisture. Using them on plastic substrates lets moisture move easily through the substrate. Though their lifetimes have improved more recently, they're limited, particularly for the color blue. And, compared with LCDs, OLEDs have limited lifetimes of about 20,000 hours, which translates into over two years of continuous use.

Nevertheless, hundreds of companies and academic laboratories are working on developing the right combination of substrate materials and electronics to enable the large-scale manufacture of flexible displays. For instance, DuPont is investigating the use of polyester films. The firm's Teijin facility in the United Kingdom is putting together a family of engineered substrates for flexible displays and their attendant electronics.