Sorting hype from reality in flexible displays

11/01/2011







Though fully flexible displays remain very much a work in progress as manufacturers continue to address issues in fabrication and stability, flexibility creates immediate value by enabling roll-to-roll production, improving mechanical properties, reducing shipping costs, and allowing for lighter and thinner displays. The shift away from cathode ray tubes (CRTs) to liquid crystal displays (LCDs) enabled applications that would not exist without flat panel displays (FPDs), such as laptop computers and digital cameras. Electrophoretic and organic light-emitting diode (OLED) technologies appear well-suited to take advantage of this transition, as both of these technologies score well in our analysis of technology value and maturity. However, electrowetting displays will be a future contender, offering higher value, but currently less mature. Each display frontplane technology requires enabling materials and processes to become a reality in devices.

Dr. Jonathan Melnick, Analyst, Printed Electronics Intelligence, Lux Research

Flexible displays enable both robustness and novel form factors. Electrophoretics ??? reflective displays which use colored charged particles that respond to an applied voltage ??? are already widespread through their use in e-readers. The saturation of the leisure e-reader market leads developers to look towards educational devices, such as e-textbooks, where robustness provides value in the hands of school children.

The U.S. Army contracted development of flexible 4 inch electrophoretic wrist displays, which should be field-tested within a year. These displays will use amorphous silicon (a-Si) backplanes to drive the display (manufactured using modified conventional vacuum deposition techniques), with substrate immobilization and lower temperatures used to make the process compatible with plastic substrates. However, this approach limits the value due to limited cost reduction potential, but leads flexible TFT technologies for maturity. Longer term printed silicon and metal oxide TFTs offer the most value, but lag in maturity due to relatively little endorsement from would-be adopters and products far from reaching the market.

Flexible OLED displays could lead to the devices of science fiction movies, where vibrant color, bendable displays are folded, rolled, or even crumpled. OLED display materials are susceptible to degradation from atmospheric water and oxygen, and current production on rigid, glass substrates provides sufficient barrier properties. However, flexible plastic substrates offer insufficient protection, so barrier films are required and key to the future of flexible OLED. Samsung's acquisition of Vitex, developer of multilayer barrier films, illustrated the importance of these films. Alternative technologies to circumvent this issue are also emerging. For example, Corning Display developed thin, flexible glass ??? an intriguing strategy that may be a worthy challenger to plastics. OLEDs generally require higher performance and stability than organic or a-Si TFTs can provide. As a result, OLEDs require higher value TFTs, which are generally less mature.

Developers will find applications to realize value in flexible display technologies. Look for electrophoretics, with their lower performance requirements to be the first to market. However, material developers will create new materials and manufacturing techniques for TFTs and barrier films. Once the flexible substrates offer the required robustness, look for OLEDs to emerge, which will open the possibility for futuristic displays for yet undiscovered applications.

Lux Research provides strategic advice and on???going intelligence for emerging technologies. Visit www.luxresearchinc.com for more information.

Solid State Technology | Volume 54 | Issue 10 | November 2011

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