OLED Technology Prepares for Landing in the Commercial TV Market
LG Display reflects on events leading up to the exhibit of its 55-in. OLED display and explains what to expect going forward.
by LG Display
WHEN introduced earlier this year, large-sized organic light-emitting-diode (OLED) technology made TV display technology exciting again – reigniting interest in an industry outshone by advances in smartphones and tablets over the last few years. At CES 2012, stunning images, displayed in a quality never before seen via a TV set, left the record 153,000 visitors to the tradeshow abuzz over 55-in. OLED TVs from set makers such as LG and others. The new TVs were also exhibited recently at Display Week 2012, exciting an even more-demanding audience of display-technology experts (Fig. 1).
Fig. 1: LG Display's 55-in. TV panel was shown at CES and Display Week 2012.
Fast-forward several months, and anticipation is again mounting as manufacturers prepare for the upcoming commercial release of the first 55-in. OLED-TV units by significantly investing in new OLED-panel production lines.
LG received wide acclaim for its 55-in. OLED panel – utilized by sister company LG Electronics in its new 55-in. TV model – which won both the prestigious "Best-of-CES 2012" award and "Best-in-Show" award at Display Week 2012. Here, in a special update toInformation Display magazine, OLED developer and manufacturer LG Display describes the impetus for developing large OLED panels and what to expect for the technology going forward.
How We Got Here
"We found ourselves wrestling with two issues: the need to push beyond LCD-TV technology and whether OLED was the right mechanism to accomplish that."
– Dr. James Lee, Technology Fellow OLED Development Department, LG Display
A few years ago, murmurs began to circulate about stagnation in the flat-panel TV market. LCD and plasma TVs had propelled the industry forward in 2006 as consumers eagerly replaced their bulky cathode-ray-tube (CRT) TVs in favor of the sleeker, high-definition sets. By 2011, however, demand appeared to have slowed, with research firm DisplaySearch forecasting a 1% annual decline in flat-panel TV sales across developed countries such as the U.S. and Europe.
Although partly attributable to the global economic slump, other factors such as rapid advancements in smartphone and tablet technology played a part in the weakening demand. While LCD-TV technology was not anywhere near on its way out (LCD units still account for 90% of current global TV sales), it was clear that the industry needed an infusion of fresh energy.
Researchers at LG Display, including Dr. James Lee, who has been experimenting with OLED for the better part of his career, quickly began to consider the technology as a potential game changer due to its strengths in the quality of the display and the advantages of certain design elements of the TV set itself; the two most critical factors for a successful consumer TV set. As Dr. Lee explained, "We realized that the application of OLED to large-sized TV panels was a canvas full of enormous potential, yet no one, at that point, had made it work."
At the time, in fact, OLED displays were only being utilized in a limited number of smartphone models – and with noticeable problems at that, such as high power consumption and poor outdoor visibility. LG Display researchers soon realized that the issues that made OLED so troublesome for mobile devices were not applicable to larger TV sets. TV is viewed in a very different environment from mobile devices. Utilized indoors, the key requirements of an effective TV set are vivid picture quality as well as a slim and light design for easy installation; both factors that OLED technology is particularly well suited for. By contrast, smartphones and tablets are mainly used to read text and view still images both indoors and outdoors. Therefore, features such as high pixel density, as well as efficient battery consumption, take precedence.
Armed with this philosophy, LG Display changed course to pursue the application of OLED to TVs, and a different technology known as AH-IPS (Advanced High Performance In-Plane Switching) to smartphones and tablets. The company's innovative efforts to develop large-sized OLED-TV panels quickly resulted in breakthroughs beyond existing LCD technology.
Beyond LCD
To understand just what LG Display achieved, it is important to understand the basics of OLED technology. Just like a discrete LED, an OLED cell is a self-emitting device that produces light based on the amount of electrical energy applied to it. It does not require a separate backlight in order to produce light, in contrast with LCDs. When OLED cells are fabricated in three primary colors and arranged on a substrate in a rectangular pattern very similar to how LCD color sub-pixels are arranged; a full-color high-resolution display can be fabricated. OLED technology features a response time to electric signals over 1000 times faster than liquid.
OLED panels are therefore able to produce remarkable image quality with no motion blur due to their fast response time, as well as dark-room contrast ratios of over 100,000:1. OLED panels also produce richer colors than LCD panels, with OLED achieving 120% of the BT.709 TV color standard, while most LCD TVs achieve roughly 100%. Also worth noting, OLED panels produce consistent picture quality at any viewing angle, an important feature for a family TV (Fig. 2).
Fig. 2: Picture-quality benefits of OLEDs over LCDs.
LG Display's accomplishments have also involved improvements in physical TV set design potential. For instance, OLED's ability to operate without a backlight means a display 80% thinner and lighter than an LCD. Also, with no need for a backlight or liquid crystal, there is potential for developing curved OLED panels without any degradation of picture performance (Fig. 3).
Fig. 3: OLED's one-panel design makes it easier for developers to create thinner, lighter TVs.
WRGB OLED
With LG Display beginning mass production of 55-in. OLED TV panels in the second half of 2012, the appearance of retail OLED-TV sets is just around the corner. Given the timing, the differences between the two versions of large-sized OLED that will be sold, RGB (red, green, blue) and WRGB (white, red, green, blue), are worth examining, as the choice will matter significantly to both consumers and manufacturers. LG Display's 55-in. OLED-TV display, which adopts a WRGB OLED top panel and oxide-TFT-type base panel, provides terrific insight into the advantages of WRGB.
LG Display's 55-in. OLED-TV panel utilizes an oxide-TFT-based panel and a pixel structure called a WRGB (white, red, green, blue) OLED for its top panel. Screen information is displayed through a color refiner below the TFT-based panel that, without risking color interference, leads to a low error rate, higher productivity, and clearer ultra-definition (UD) screen via the benefit of small pixels (Fig. 4).
Furthermore, WRGB OLED realizes identical colors from wide viewing angles through color information displayed through a thin layer. The higher energy efficiency of WRGB OLEDs, especially when considering web-browsing applications for smart TVs, is a key strength. Specifically, the use of white pixels allows WRGB OLED panels to consume less electricity than RGB OLED panels.
WRGB OLED also provides a better return on investment for manufacturers, especially critical as the technology is first introduced to the market. Compared to RGB OLEDs, WRGB OLEDs require 50% less investment in facilities and equipment with a higher yield rate. Clearly, WRGB OLEDs are ideal for large-screen TVs due to their quality and cost benefits.
Fig. 4: This chart compares the productivity benefits of LG OLED technology over other types of OLED implementations.
In addition, LG Display's use of an oxide-TFT-based panel instead of the low-temperature-polysilicon (LTPS) panel used in existing small-sized OLED panels results in faster and more sophisticated processing of light quantity and color information. The oxide-TFT process that LG Display utilizes is similar to the existing a-Si TFT process, with the difference lying in replacing amorphous-silicon with indium gallium zinc oxide (IGZO), which produces image quality that is identical to high-performance LTPS-based panels at significantly reduced investment levels.
What to Anticipate Further Down the Road
In addition to vibrant imagery in a razor-thin design, LG Display's 55-in. OLED TV panel will from the outset incorporate additional innovative features such as film-patterned retarder (FPR) 3-D technology. And the commercial introduction of OLED TV sets is only just the beginning. For example, as the first OLED-TV units will be marketed as premium products, manufacturers have opted to begin with a 55-in. size, currently the largest screen size in the high-tier TV market.
As technology progresses, sizes are expected to vary and prices to come down. LG Display expects that OLED TV will reach a price premium of 50% in about 2015; this is when the market will start to grow. In addition, features such as OLED power consumption are constantly being improved, and the introduction of curved OLED-TV units is also not far off. The next generation of TV technology is now upon us, and consumers as well as the industry are justified for their excitement at what lies ahead. •