Display Week 2014 Review: OLEDs
OLEDs are no longer on the way; they’re here. At Display Week 2014, not only did we get to see how they have become established in some markets, we also saw how the technology is advancing rapidly in ways that can only expand their appeal in the future.
by Alfred Poor
IN 2014, we can finally stop making hopeful pronouncements about how it’s going to be “The Year of the OLED.” OLEDs have arrived. This technology has established a solid footing in the display industry and shows signs of continuing growth. OLED TVs are shipping in small numbers, but they are shipping at last. They are curved and thin and beautiful. At the same time, OLED technology dominates the markets for high-end smartphones, tablets, and other portable display devices. And at Display Week 2014, we saw new applications made possible by certain expanded capabilities of OLEDs that LCD technology is hard pressed to match. From wearable technology to solid-state lighting, OLED technology is poised to launch new products on several fronts.
Award-Winning Technology
While LCDs continue to dominate the show floor at Display Week and the display industry at large, one need look no further than SID’s own Display Industry Awards to see how OLEDs have become an integral part of this industry. Four out of the six award winners this year were based on OLED technology, including Samsung’s 5.68-in. OLED panel, LG’s 55-in. OLED TV panel, Universal Display Corp.’s green phosphorescent OLED (PHOLED) material, and LG Displays’s G Flex smartphone. (For more information about these products, see the Display Industry Awards article in the May/June 2014 issue of Information Display.)
OLEDs on Display
These award winners were but the tip of the OLED iceberg in the Display Week 2014 exhibit hall. For example, Tianma/NLT was showing a demonstration panel that was 5.5 in. on the diagonal with a 1280 × 720 high-definition resolution and rated at a luminance of 200 nits. AU Optronics Corp. (AUO) showed a 5.7-in. OLED panel with an amazing 2560 × 1440 pixel resolution (quad 720p high-definition resolution) rated at 300 nits; this works out to a pixel density of 513 ppi (Fig. 1). This was probably just a demonstration to show off what the company can do with OLED technology, but it was impressive. The image looked almost as if it were a high-quality print on paper.
Fig. 1: AUO’s 5-in. OLED panel has a pixel resolution of 2560 × 1440 for an impressive 513 ppi. It is rated at 300 cd/m2 and produces imagery that looks almost as if it is printed on paper. Photo courtesy Alfred Poor.
Perhaps the most impressive small OLED panels were the flexible ones. In addition to LG and Samsung’s award-winning curved panels, AUO showed a 5-in. panel with high-definition resolution (1280 × 720 pixels) built on a plastic substrate with a thin-film barrier for encapsulation. The active-matrix panel was just 0.2 mm thick – equivalent to about two sheets of paper – and could be bent to a radius as small as 1 cm. Not all the flexible panels were active-matrix OLEDs, either. It’s great to have a high-resolution color display, but there are times when a lower information density will suffice in order to have a lower-cost display. Futaba makes a wide range of these passive-matrix OLED displays and showed a variety of them in its exhibit. For example, the company was showing a 3.5-in. panel with a pixel resolution of 256 × 64 that was only 0.22 mm thick and could be curved to fit a person’s wrist. This display even included touch functionality.
Some displays pushed the very boundaries of what it means to be flexible. Among the many papers delivered during the Symposium on the subject of flexible OLED displays, researchers from Semiconductor Energy Laboratory (SEL) in Japan, along with colleagues from Advanced Film Device and Nokia, demonstrated a novel OLED display that could be folded in half and still function — even when still folded. The prototype 7.9-in. display on a plastic substrate had a high-definition 1280 × 720 pixel resolution (249 ppi) and was folded to a radius of 2 mm more than 100,000 times without defects appearing. This could lead to a smartphone with a large display that could easily fold up and fit in your pocket.
Even more impressive was an OLED display created on a plastic substrate by Plastic Logic that was demonstrated in the I-Zone (Fig. 2). This panel used an organic thin-film transistor (TFT) backplane, printed on the plastic film at temperatures below 100°C (boiling water). The device was so flexible that it could be rolled around a standard pencil while operating.
Fig. 2: Plastic Logic demonstrated a flexible OLED with a printed backplane on a plastic substrate. Photo courtesy Alfred Poor.
Wearable Displays
These flexible displays point toward one of the fast-growing markets where OLEDs may have a chance to dominate: wearable technology. From Google Glass to the Fitbit, wearable computing has captured people’s imaginations for applications ranging from fashion to fitness, from location tracking, to medical diagnosis and treatment. OLED technology’s flexibility, light weight, low power consumption, and durability make it an attractive choice for these devices.
Already, we are seeing the second and third generation of smart watches coming to the market. At Display Week, Samsung showed the displays that it uses in its latest watches. The Gear 2 has a 1.63-in. OLED display with a pixel resolution of 320 × 320, delivering 277 ppi and 300 nits of luminance. The Gear Fit (Fig. 3) has a curved 1.84-in. display with a high (or wide) aspect ratio (8:27) and a resolution of 128 × 432 pixels, for 244 ppi at 300 nits. On the whole, smart watches appear to be a market segment with potential that has not yet been realized. The devices tend to be large and thick, but the displays appear to be ready once the manufacturers miniaturize the rest of the components and come up with more compelling usage models.
Fig. 3: The Samsung Gear Fit smart watch sports a curved OLED display that would be a lot more attractive if the rest of the watch were thinner. Photo courtesy Alfred Poor.
Not all smart watches rely on OLEDs, however. E Ink’s bistable display technology is a good choice for such applications, as it only draws power when the contents of the display change. The company had some smart watches on display in its booth. And there are small, direct-view LCD panels that are also suitable for wearable applications. For example, Sharp showed its octagonal 0.99-in. transflective memory display, which includes memory for each of the 128 × 128 pixels. This design means that the panel only draws 10 µW when displaying a static image and 45 µW when changing the screen’s contents.
Of course, some display panels are too small to see unaided with the naked eye. These are suitable for a variety of applications, but Google Glass has many people rethinking the role of head-mounted displays for wearable computing. Sony presented a Symposium paper describing a new 0.23-in. OLED microdisplay with a pixel resolution of 640 × 400. The panel has a pixel pitch of only 7.8 µm and draws just 80 mW when producing 20 nits. The design is based on a white OLED panel with color filters for the subpixels. eMagin also showed OLED microdisplays built directly on silicon backplanes, including a 0.62-in. panel with a pixel resolution of 1280 × 1024.
Other companies also showed microdisplays using additional technologies. Kopin exhibited its White Pupil: a 0.2-in. LCD imager with a pixel resolution of 428 × 240 with optics that could easily be incorporated into the frames of eyeglasses, as shown in (Fig. 4). Using Kopin’s bright backlight technology, this device can deliver more than 5,000 nits. The result is a sunlight-readable head-mounted display that consumes less than 100 mW. Holoeye showed its LCOS imagers, which were as small as 0.26-in. with a high-pixel resolution of 1280 × 720.
Fig. 4: Not all glasses are made by Google; the Kopin White Pupil demonstrator shows how Kopin’s head-mounted display can be hidden in an eyeglass frame. Photo courtesy Alfred Poor.
There were some other novel microdisplays that could be suitable for wearable-technology applications shown in the I-Zone. INSiAVA has developed an emissive display fabricated on a CMOS backplane. Its 320 × 240 pixel panel can show graphic images and video. Ostendo Technologies showed its Quantum Photonic Imager, which stacks LEDs on a CMOS backplane. (This technology won the award for Best Prototype in the I-Zone.) The imager can have a pixel pitch of 5–10 µm and brightness of more than 20,000 nits while consuming less than 300 mW. Lumiode is another I-Zone company that showed an LED matrix display technology it was developing.
Solid-State Lighting
We have been hearing for some time that OLEDs are good for more than just information displays. Their emissive properties and potential for low-cost roll-to-roll manufacturing make them an attractive candidate for solid-state lighting (SSL) applications. The Symposium program included two sessions devoted to the use of OLEDs in lighting.
There were few lighting exhibitors on the show floor at Display Week (in part because Lightfair International was going on at the same time), but UDC showed its “moon window” in its booth (Fig. 5).
Fig. 5: Perhaps the most unusual display at the show was the Moon Window from Universal Display Corporation, which demonstrated how transparent white OLED panels can make windows a light source at night. Photo courtesy Alfred Poor.
This full-size window had a bright-white OLED image of a full moon on the glass, demonstrating how a window could use a transparent OLED device to admit sunshine during the day and then be a source of artificial illumination at night. OLED materials supplier Novaled also showed transparent OLED lighting panels in its booth. During his keynote speech, Dr. Michael Heckmeier from Merck showed examples of how Merck’s OLED materials are being used to create lighting for automotive applications, including replacements for location and signal lamps that are incorporated in the body of a car’s exterior.
Other SSL technology products were also present. LEDs are already generating significant energy savings worldwide. The same type of diffuser technology used for LCD backlight panels has direct application for LED-based SSL solutions. For example, Luminit, a maker of light-management films and panels, displayed a variety of its light-shaping diffuser products in the Display Week Exhibit Hall.
There were other materials stories at Display Week 2014, especially for OLED technology. One of the most intriguing, perhaps, was Dr. Heckmeier’s keynote address about collaboration between Merck and Epson to develop soluble OLED materials for use in inks that could be employed to fabricate OLED displays through ink-jet printing and other processes. Also, Beneq had an exhibit showing its thin-film encapsulation barriers for OLED devices. Based on atomic layer deposition (ALD), this clear and flexible technology could be suitable for roll-to-roll production of OLED displays and lighting devices.
OLEDs on the Rise
While they are not likely to challenge LCDs in all markets, OLEDs have already established dominant positions in several arenas. And, as we saw throughout Display Week 2014, the new markets for wearable computing and solid-state lighting are opening doors where OLED technology may have a strong competitive advantage over other approaches. OLEDs are here to stay and growing stronger. •