Flexible electronics have recently captured the fascination of researchers and companies alike. [1,2] Mobile companies, in particular, aim to re imagine the future with mobile flexible displays which exploit the highly favorable properties of flexible circuitry, such as strength, flexibility, scale, and manufacturability.
OLED displays first started to appear in the early 1990s. Active matrix (AM) OLED displays presented technical difficulties and LCDs kept getting better. [1] Eventually, OLEDs found a home at the low end of the display market; in small displays for the MP3 and cell phone sub-display market primarily. [3] The prospects of OLEDs were revealed as the manufacturing process was perfected and the research accelerated. Display manufacturers across the globe retooled for the next generation of AMOLEDs to build the ultimate flexible display. [4]
In the literal sense, Flexible Displays are graphics mounted onto a flexible, non rigid substrate. [1] These displays/ circuits are thus built on certain types of substrates based on the required properties. Metal foils handle high process temperatures and provide a good barrier to moisture and oxygen. However, they are expensive, cannot handle multiple bends and are best used for non-transmissive displays. [2,5] Plastic displays are a good alternative and possess a reasonable tradeoff amongst mechanical, optical and chemical performance. The last choice for substrates is the Polymer substrate. Polymers are flexible, transparent, lightweight and robust making them an ideal substrate material. [1,2]
This flexible substrate combined with an appropriate display media gives us the flexible display. LCD display media shows significant problems with cell-gap control which directly translates to poor display optical performance. [2] The LCD also requires a flexible backlight to maintain its high performance. AMOLED technology offers significant advantages over LCD and is the current commercial favorite for flexible displays. Electrophoretic Displays also overcome the LCDs drawbacks but are still in research state. This is the most viable alternative to OLED displays. [1,2]
These displays combined with flexible circuitry and batteries, like the ones developed at Stanford University, will give us the first flexible/ rollable phones and PDAs! [6]
The AMOLED display has superior image quality with respect to wide viewing angle, fast response time, being lighter and thinner, lower cost, and lower power. [4,5] AMOLED is the natural choice for the flexible display a it has rugged solid state display media, has full color etc. Thus using light-emitting organic materials, beautiful and efficient displays can be created. The substrate structure of the OLED display allows it to be made bendable, flexible displays. Because these displays will not be covered with glass, they'll be more durable and virtually shatter-proof. [2,5]
Flexible Displays redefine "mobile" as they can be bent into different shapes and sizes to allow easier storage and better portability. They stand to revolutionize the world of portable electronics and in particular, the cellphone. As Frank Gillett, Vice President and principal analyst at Forrester said, bendable displays stand to ultimately reduce the physical footprint of any mobile device. [7]
© Nruthya Kavadichanda Madappa. The author grants permission to copy, distribute and display this work in unaltered form, with attribution to the author, for noncommercial purposes only. All other rights, including commercial rights, are reserved to the author.
[1] J. van den Brand et al., "Flexible Embedded Circuitry: A Novel Process For High Density, Cost Effective Electronics," Microelectronic Engineering 87, 1861 (2010).
[2] W. S. Wong and A. Salleo, Eds., Flexible Electronics: Materials and Applications (Springer, 2009).
[3] A. K. Bhowmik, L. Zilli and P. J. Bos, eds., Mobile Displays: Technology and Applications (Wiley, 2008).
[4] I. J. Chung and I.-B. Kang, "Flexible Display Technology - Opportunity and Challenges to New Business Application," Mol. Cryst. Liq. Cryst. 507, 1 (2009).
[5] J.-K. Jeong et al., "Flexible Full-Color AMOLED on Ultrathin Metal Foil," IEEE Electron Dev. Lett. 28, 389 (2007)
[6] L. Hu et al., "Thin, Flexible Secondary Li-Ion Paper Batteries," ACS Nano 4, 5843 (2010).
[7] C. Bonnington, "Flexible Displays Landing in 2012, But Not in Apple Gear," Wires, 16 May 12.