Flexible organic LCD - Large area, high brightness and long lifetime
June 13, 2017
This year at SID Display Week, the industry was celebrating “30 years of OLEDs”, with several display makers showcasing latest versions of OLEDs, both glass-based and flexible. Alongside this it was also clear that LCD, continues to reinvent itself to maintain its dominance. BOE, JDI, AUO and Samsung showcased new LCDs as described in Sweta Dash’s article for Display Daily.
With two invited talks at the show, FlexEnable also showed how it is redefining the boundaries of LCD with flexible organic LCD (OLCD) – a technology that allows the development of high performance, low cost plastic LCDs using an organic transistor backplane (OTFT).
In this article I explain why OLCD on a plastic substrate is the only display technology that is able to deliver flexible displays with very large area, high brightness and long lifetime – features that are required for applications like automotive, home appliances, large area consumer electronics, and digital signage.
Scalability – large flexible displays
One of the strikingly different attributes of OLCD compared to other flexible display approaches is its natural scalability to large sizes, for two reasons: firstly, the LCD frontplane is optically just like a conventional LCD, except that it is made on plastic instead of glass; LCD has been manufactured for very large displays (>80”) for many years making it the most common and trusted display technology today. Secondly, the backplane, which uses OTFT on a TAC film, deploys a complete low temperature process, with a simple handling method - that means the TAC can be released from the glass with ~100% yield regardless of size.
Other flexible display technologies are not scalable to the large display sizes, or large panel production lines, because either the backplane or the frontplane cannot be scaled easily. For example, in the case of flexible OLED displays using LTPS on polyimide, there are limitations in scaling the LTPS backplane, as well as the laser release process that removes the polyimide from the glass.
At FlexEnable we have a 14” prototype line on which we can make OLCDs up to 12.1” in size. With today’s OTFT performance being better than amorphous silicon (a:Si), there is no limitation to the size of flexible OLCD - it can be made as small or as large as the manufacturing equipment used for flat panel displays allows, opening the door to applications like digital signage and large area displays for automotive and home consumer electronics.
High brightness and long lifetime
It is well known that OLED displays provide very high contrast and excellent colour gamut. However, the lifetime of an OLED display is strongly related to the brightness of that pixel: if you double the brightness of the pixel, its lifetime becomes four times shorter. On the other hand, for LCD the lifetime is independent of the display brightness because it is achieved through transmission of a separate light source (the backlight), rather than emission of its own light.
The same comparison applies whether the display is on flex or glass – and today flexible OLCD displays have better TFT stability than their glass a:Si counterparts. FlexEnable’s technical director has provided more details in his blog post on OTFT performance.
In regard to product applications the need for large area, high brightness conformed displays is particularly clear in automotive – read FlexEnable’s article Plastic Displays Will Play a Major Role in Automotive HMIs published in SID Information Display Magazine.
Flexible OLCD allows flexible displays to be incorporated into products in ways that aren’t possible with other display technologies, and we are excited to work with customers on product prototypes. If you are working on a product that requires a flexible display, please get in touch with FlexEnable at email@example.com.