Display Week 2010 Review: LCDs
Liquid-crystal-display technology continues to dominate.
by Alfred Poor
JUST by casually walking up and down the aisles of the exhibit floor at Display Week 2010 in Seattle, it could be plainly seen that liquid-crystal-display (LCD) technology continues to be the dominate technology for many display applications. Obviously, cathode-ray tubes (CRTs) and their related components are long gone, and even the more recent competitors in the marketplace such as OLED displays are doing little to claim turf in terms of actual products. Even the bumper crop of touch-technology demonstrations on the show floor exist primarily to support LCD applications.
So, one might expect that LCD technology has become the established technology, satisfied with its success and enjoying its leading role in the display industry, but that couldn't be further from the truth. Just about everywhere at Display Week – on the exhibit show floor, at the Symposium technical sessions, and even in the awards – it was clear that many people in the display industry are working hard to improve all aspects of LCD technology. This is not an industry content to rest on its laurels. Instead, it recognizes the competition from existing and developing technologies and is striving to maintain its advantages.
Who Needs OLED or Bistable Displays?
For example, although OLED and bistable display technologies continue to garner a great deal of attention in the press, LCD performance is improving rapidly, which is reducing the advantages offered by the new challengers.
Among other advantages, OLED technology has always presented the promise of much thinner flat-screen HDTV sets. But improved light-guide plates (LGPs) and light-management films have made it possible to create edge-lit LED backlight units that may make consumers forget the siren song of thin OLEDs. In the exhibit hall, LG showed off a 42-in. 1080p LCD panel that was a mere 2.6 mm thick (Fig. 1); that's about one-tenth of an inch, or the thickness of a typical sheet of corrugated cardboard.
Fig. 1: LG's demonstration 42-in. LCD panel is about as thick as a sheet of cardboard. Photo courtesy Alfred Poor.
e-Book applications have been dominated by ultra-low-power display technologies such as electrophoretic and bistable LC. However, conventional LCDs are also making significant inroads in areas that are generally viewed as belonging to bistable solutions. The 2010 SID Display of the Year Silver Award was awarded to the Pixel Qi 3Qi Multimode LCD. It is able to show full-color full-motion video in low light conditions, but can work without its backlight in high ambient light levels, including direct sunlight. Each pixel has about the same transmissivity as that of a typical LCD panel, but it is also highly reflective. As a result, the reflective mode uses about 80% less power than a typical LCD panel while delivering image quality that is on a par with that of conventional ultra-low-power technologies. This display was developed by Mary Lou Jepson and her team at PixelQi, which is a spin-off from the One Laptop Per Child (OLPC) initiative, for which Jepson developed an earlier generation of the 3Qi screen.
It's Getting Easier to Be Green
Conventional backlit LCDs are inherently somewhat inefficient devices in which much of the backlight illumination is absorbed by the panel, even when displaying a white image on the full screen. Many companies are tackling this problem, aiming to make the displays more efficient by utilizing techniques such as local dimming of LED backlights. By reducing the amount of light in areas where the image is dark, less light is wasted by being absorbed by the LCD panel, which in turn saves energy.
Samsung demonstrated two panels (Fig. 2) that make use of the PenTile® technology from Nouvoyance (formerly Clairvoyance, now owned by Samsung) that makes LCD panels more light efficient by using a different approach to the conventional RGB subpixel design.
Fig. 2: The PenTile® pixel structure of Samsung's demonstration panels uses less power than that of a conventional LCD panel with equivalent resolution. Photo coutesy Alfred Poor.
This novel subpixel design provides equivalent resolution using fewer components than a standard red-green-blue stripe configuration, which allows more light to pass through, allowing the panel to produce the same amount of light using about half the power. In lieu of a stripe configuration, a white subpixel is added to the red, green, and blue pixels, and they are arranged in a quad formation. The white subpixel provides additional brightness, and the novel arrangement of subpixel components makes it possible to create an equivalent resolution with fewer subpixels than a standard RGB configuration (Fig. 3).
Fig. 3: The PenTile® RGBW design appears above the conventional RGB stripe configuration. Image courtesy Nouvoyance, Inc., and Samsung Electronics Co., Inc.
Other components of LCDs, such as the backlight system, are also becoming more efficient. For example, 3M demonstrated its improved Vikuiti™ Dual Brightness Enhancement Films (DBEF) on an unusual display. The company showed an 18.5-in. desktop computer monitor that used only a single USB cable as its connection to the computer. The USB 3.0 connection not only carried the display signal, but also provided the 8 W of power required to run the monitor. This compares with about 14 W required by a typical panel. The lower power demand means that the monitor maker can eliminate the separate AC-to-DC power converter. Of course, the key to this achievement is the higher light recycling efficiency of the new film, but the concept is broadly based. A typical LCD panel absorbs at least 95% of the light emitted by the backlight, even when showing an all-white screen, so any light that can be recaptured and directed through the panel can result in significant energy savings.
Compare and Contrast
Ambient light can also diminish the image quality of LCD panels despite their ability to show a higher luminance image than some other display technologies. Reflections can be a major source of this problem, thus resulting in anti-glare and anti-reflection solutions getting a lot of attention. Optical bonding processes, while not new, continue to evolve as a result. For example, Toshiba demonstrated its Screen Fit technology that eliminates the air barrier between an LCD panel's top polarizing layer and the cover layer. The optically transparent bonding process eliminates two boundaries, which reduces the internal reflection of ambient light. In its booth, Toshiba showed a 12.1-in. panel with this technology next to another panel based on conventional processes (Fig. 4). The reduction in reflection was striking.
Fig. 4: The panel on the left uses Toshiba's Screen Fit technology to reduce reflections; note how the bright overhead lights are much less visible on the left-hand panel and how much the image on the right is washed out by the ambient lighting conditions. Photo coutesy Alfred Poor.
Even more striking was a demonstration of Sharp's new "moth-eye" anti-reflection (AR) technology. The company has already developed effective AR films that rely on nano-structures to reduce ambient reflection. The new technology uses finely patterned holes and "steeples" that are modeled after the structures found in nature – in the eyes of moths. When the surface of the existing AR films is treated with this new structured pattern, the reduction in glare is remarkable. According to a paper presented, "the minimum specular reflectance was reduced to 0.02% and the average reflectance was less than 0.04% in the visible range (380–780 nm) with little wavelength dependence." The panel displayed in the Sharp exhibit had stunning, deep blacks and showed vivid high-contrast images despite high ambient light levels. (Fig. 5).
Fig. 5: Using the technology based on moth-eye structures, Sharp has developed a new anti-reflection film that yields impressive results. Photo coutesy Alfred Poor.
Big and Small, Short and Tall – and Rugged
If LCD technology demonstrated anything at Display Week 2010, it is how it can be adapted to a wide range of applications. For example, Samsung showed its 84-in. UHD panel with touch. The 3840 x 2160-pixel panel is the equivalent of four 42-in. 1080p panels combined. At the other end of the spectrum, Syndiant showed its tiny LCoS microdisplays intended for use in pocket projectors. The company now has a 0.44-in. WSVGA panel with a1024 x 600-pixel resolution.
In between these extremes, all sorts of LCD panels could be found on display. Tannas Electronic Displays, which specializes in resizing LCDs, showed some of its custom resized panels, including one that was 5 x 35.5 in. Another LCD specialist, CheonJo Smart DNC, also had panels with unusual dimensions, including a 32-in. unit with a 1366 x 435-pixel resolution. These displays make it easier to create novel applications for target markets such as military, aerospace, and digital signage.
Many other companies had specialized panels on display. Hitachi had a wide range designed for industrial applications, as did Sony. Rockwell Collins showed a variety of ruggedized panels for industrial and avionics applications, some of which were designed to handle temperature ranges from -55 to 100°C. Optrex, Vertex LCD, Shanghai Tianma, Bi-Search International, STI, Avnet, and Wintek were among additional exhibitors who showed a variety of panels designed for industrial applications. Product designers should have no problem finding the ideal panel from these combined offerings for whatever product they plan to create.
Display Week 2010 definitely was a showcase for touch-screen and other display technologies, but there is no doubt that LCD technology currently rules the roost. Consequently, many other display innovations not discussed in this article also relate to LCDs. For 3-D LCD news, see the review article on 3-D in this issue, and for news on the proliferation of LED backlighting and other forms of power savings, see the green-manufacturing review article. All in all, manufacturers and researchers clearly recognize that they must continue to improve the technology if it is to hold onto its top spot, and based on the innovation on display this year, it looks as though they are going to enjoy continued success. •