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General

Display Market

OLEDs, Flexible Displays and the Future

Lawrence Gasman, Principal Analyst, NanoMarkets

The display industry is currently under pressure to find new sources of revenue and increase profitability. The transition from CRT to FPD is now moving inexorably towards completion and the economies of scale that the FPD industry has found in using ever-larger substrates seems to be petering out. For these reasons and others the display industry is seeking new technologies that can boost its future prospects. There are several potential directions in which the display industry might look for new profits, but OLEDs and flexible displays look particularly promising. Flexible displays may use OLED technology, but in the short term seem more likely to be based on e-paper.

OLEDs

OLED displays first started to appear in the early 1990s. By 2004, firms such as Philips, DuPont and Kodak had quit the business. Active matrix (AM) OLED displays presented technical difficulties and LCDs kept getting better. 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.

But 2008 is proving a breakout year for OLEDs. They have started to be used in cell phone main displays (a 1.1 billion unit market) and early in 2008 the first OLED TVs appeared. A strong interest has also developed in OLED lighting; OLEDs present a low power lighting alternative in a world of costly energy and they complement more ubiquitous HB-LEDs well; the former are floodlight-like, the latter spot-light-like. The low-power aspect of OLEDs is attractive in the mobile display space too, since the power densities of mobile power sources can never quite keep up with all the new features that are being added to mobile communications and computing devices, even with the latest power management tools.

Meanwhile display manufacturers have been retooling for the next generation of AM OLEDs which offer better cost/performance measures. We have also seen the recent commercialization of small molecule OLED inks, which makes it a little more likely that printing can be used extensively to fabricate low-cost OLEDs. However, for OLEDs to reach their potential, they will have to reach and exceed a variety of performance bars imposed by the marketplace. The principal dimensions along which OLEDs must prove themselves are: product lifetime, resolution, durability, and of course, cost. And these are the areas where much of the OLED R&D is focused.

Flexible Displays and E-paper

Most OLED displays today use glass substrates and consequently they are rigid devices. However, the prospect for the flexible display created on metal foil or (less expensively) plastic summons up images of low-cost R2R manufacturing, which again may include printing. However, flexible backplane technology is currently at a stage where it is not really capable of supporting high-quality video of the kind that OLEDs can provide. This is one reason why flexible displays have, at the present time, come to be so strongly identified with e-paper. E-paper is a display concept that seeks to emulate paper as closely as possible, but particularly in the clarity with which it presents text. This includes an emphasis on outdoor readability, a characteristic in which few other display technologies (and definitely not OLEDs) excel. Early e-paper products were novelties such as flexible or ultra-thin clocks and watches, but the thrust of the first major commercialization of e-paper products is now coming in the form of electronic book readers. As with OLEDs, e-paper has taken a big leap forward in the past year. Amazon.com has made its version of an e-paper reader a centrepiece of its business plan. This reader is not flexible (although it has a flexible frontplane) but another reader produced by Polymer Vision and which may well be on the market by the time this article is published, is at least foldable.

The Future

While the term OLED describes a particular technology, e-paper is really a class of display technologies that exhibit paper-like features. The most common e-paper technology is electrophoretic, but there are a variety of other possibilities including especially electrochromic technology and specialised forms of liquid crystal. Unfortunately, what all of the widely used e-paper technologies have in common in addition to being paper-like is that they are typically a monochrome technology. Most e-paper companies already have welldeveloped programmes to bring colour to e-paper, but the current state of the art in colour e-paper tends to be rather pallid and unattractive. E-paper’s ability to be seen in bright sunlight is an obvious and big advantage for a mobile display and one that can’t be duplicated by OLEDs. But most of us moved past the monochrome cell phone display a long time ago.

So the bottom line today is that we have flexible displays based on e-paper, whose addressable markets (in signage, for example) are limited by a lack of colour. And we have OLED displays that can match or beat the most vibrant colour of the best LCDs. Eventually, this must change. Improved colour e-paper is surely on its way, perhaps using some extension of today’s colour filter technology, perhaps using new approaches to e-paper such as electrowetting. Similarly, flexible backplanes that can support the impressive video of which OLEDs are capable are also likely to appear. Perhaps we will speed up these backplanes with a new generation of organic electronics using rubrene transistors and based on some kind of organic CMOS concept. Or perhaps they will use silicon as they do today, but applied using novel printing methods suitable to flexible substrates.

The technological challenges, however, shouldn’t be allowed to obscure the marketing challenges. E-paper book readers are a very “cool” concept, but they will only become a high volume consumer product if people can be convinced to give up on real paper for both books and newspapers. There are lots of environmental and other reasons why they might do this, but the difficulties in persuading them to do so should not be underestimated. Similarly, OLEDs have excellent video refresh rates, making them suitable for the mobile video that many in the wireless industry hope will drive their next revenue surge. But who would really want to watch “Star Wars” on a screen a few square centimetres in size? Potentially, the addressable market for mobile video could be expanded, by rollable OLED displays that one could travel with, unfurl and plug into a cell phone or PDA to create a display that might be the size of a small television. But by just how much would rollable displays expand the “handheld video” market? No one knows!

For now, the marketing challenges associated with OLEDs are heightened by the fact that in almost all of the markets in which they currently compete, OLEDs compete with LCD technology and the advantages of OLEDs are not always that obvious. And, as I have already mentioned, the current generation of E-paper is hurt by the poor quality of the colour it can offer. But the display firms that are supporting these technologies have their eyes on a future in which flexible OLED and E-paper displays find markets that only they can serve.