DisplayWeek 2011 Review: LCDs
Liquid-crystal displays evolve in many directions.
by Alfred Poor
IF you stop and think about it, it is remarkable how the liquid-crystal-display (LCD) panel has come to dominate the world of information display. Not only has it displaced a variety of older technologies – most notably the cathode-ray tube (CRT) – it has also managed to enable a host of new applications that were not possible without it. Notebook computers, personal navigation devices, and even cell phones could not have been successful without thin, lightweight, and low-power LCD technology.
So it should be little surprise that LCDs dominated all aspects of Display Week 2011, from the exhibit hall floor to the Symposium sessions. And there seems to be plenty of life left in the technology, with new advances being explored in many different directions.
In the space allotted here for LCD coverage, it would be impossible even just to list all the 2011 Display Week papers, posters, and exhibits that related to LCDs. Instead, here is an overview of some of the highlights.
Display Week As a Materials Show
Materials are a good place to start because there was plenty of news on the subject at this year's show. These developments are likely to have a significant impact on the LCD industry going forward.
For example, LCD production remains a batch process using discrete sheets of motherglass that are then cut into individual displays. There is some question as to whether or not we have reached the practical limits of this approach with Gen 10 production plants such as Sharp's Sakai facility. One possible avenue to lower production costs and higher efficiencies is through the use of roll-to-roll processing for some or all production steps. Substrates other than glass have the flexibility to make this possible, though these alternative materials have shortcomings compared to glass.
As a result, it was interesting that both Corning and Asahi Glass Company showed 0.1-mm-thick glass in their DisplayWeek exhibits (Fig. 1). While this glass has potential for several display technologies (such as serving as an encapsulation layer for OLED panels), it could have a particularly big impact on LCDs. It could eliminate a lot of weight, for example, which has advantages when multiplied times millions of units. And it could help lower production costs by increasing efficiency.
Fig. 1: Corning's 0.1-mm-thick glass is so flexible that it can be moved in a continuous loop around rollers. Photo courtesy of Alfred Poor.
Another group of materials that received lots of attention at Display Week were the metal oxides that are being used instead of a silicon layer for the active backplane in LCDs. Sharp has announced that it will convert about one-quarter of its Kameyama 2 Gen 8 plant to use indium gallium zinc oxide (IGZO) for its semiconductor layer. Samsung also demonstrated a 70-in. UD (3840 x 2160 pixel) LCD panel with a metal-oxide TFT backplane.
Another material that has drawn a lot of interest is "blue-phase" LC technology. This is a phase of liquid-crystal material that normally exists in a narrow range of conditions, but can be stabilized through the use of polymers. The result would be an LCD panel with extremely rapid refresh rates, with the potential for reduced motion blur. It is also possible that the panels could be fast enough to support field-sequential backlight illumination, which could eliminate the need for subpixels and color filters. There were three separate sessions devoted to blue phase alone in the Symposium, as well as a Monday seminar. (For earlier discussions of blue phase, see the November 2009 issue of Information Display.)
One of the most dramatic materials demonstrations was on display at the 3M booth. The company showed its "Collimating Multi-layer Optical Film" (CMOF), which makes possible a new light-mixing technology for LCD-panel backlights that it calls "Air Guide." The traditional approach to LED edge-lighting for LCD panels requires multiple layers of light guides, diffusers, collimators, and other materials. The new 3M approach combines all these functions into a single layer that is adhered to the back of an LCD panel. An air space behind this is then backed by a reflective layer at the back of the display.
The new film can eliminate as much as 3 kg of weight from a typical 52-in. LCD HDTV simply by eliminating the extra materials. It also is so effective at diffusing the edge light that the LEDs can be spaced as far apart as 60 mm instead of the standard 12 mm, which means that either display designers can use fewer LED parts or they can use the standard number with increased reliability because a failed LED will not be noticeable. There are other benefits to this more effective light mixing; for example, less-expensive white LEDs can be mixed to produce the same color temperature as more expensive pieces. As a result, this new Air Guide technology may have a big impact on large-LCD-panel design.
Of course, there were plenty of LCD panels to see and hear about at Display Week. Samsung showed a number of displays using the Nouvoyance PenTile technology, including a tablet-sized panel with 300-ppi resolution and another with a 180-Hz refresh rate that had a field-sequential-color backlight. (Samsung also showed a 46-in. "active retarder" 3-D HDTV that uses passive glasses, employing a second LCD layer to actively switch the polarity of the image's light.)
LG had some impressive LCD panels, including a 4.5-in. display with 329-ppi resolution. A 47-in. panel with LED edge lighting along just on one side demonstrated low power consumption, demonstrating a power reading of 35–38 W.
Several companies showed LCD panels with narrow bezels designed for video-wall applications, either for control room or digital-signage installations. One of these, from Planar, had a display that used 46-in. panels and had a combined 6.7-mm-wide bezel when tiled (Fig. 2).
Fig. 2: Planar's LCD panels have thin bezels so that they can be tiled to create a video wall. Photo courtesy of Alfred Poor.
There were several LCD panels with integrated photosensors. Samsung showed a 40-in. panel with an IR sensor at every pixel in their high-definition 1920 x 1080 display. The sensors support input from more than 50 simultaneous points without relying on ambient lighting, a technology that Samsung has named "PixelSense." The panel is designed for use in the upcoming Microsoft Surface-2 touch display. Toshiba had a panel that integrated both a photosensor and a 1-bit memory per pixel. This 7-in. QVGA panel with "in-cell write-erasable" technology lets the user write on the screen, which then requires just 0.7 mW to maintain the image. The result is a display that can act much like an Etch-A-Sketch toy, in that you can write on the screen with a light pen and the image will be retained using very little power. You can then erase the image at any time (Fig. 3).
Fig. 3: Toshiba demonstrated an LCD panel that contained both light sensors and 1 bit of memory per pixel, which allows one to write on the screen with a light pen and the image to be retained using very little power. Photo courtesy of Alfred Poor.
Many exhibitors showed LCD panels for industrial and other vertical applications. Unlike the typical consumer products that ship in the tens or hundreds of thousands, devices for medical, aviation, or industrial applications ship in much smaller quantities and a given model may need to have a lifetime that spans many years. Display manufacturers must be able to provide the customers that count on them with a steady and reliable supply.
This is not always easy to accomplish. For example, Sharp Microelectronics was informed not too long ago by its supplier of cold-cathode fluorescent (CCFL) backlights that the company was exiting the market. The Sharp engineers had to design LED-backlight equivalent displays that were plug-compatible with the original CCFL models. In most cases, they were able to incorporate the LED drivers onboard the panel. In a similar vein, Endicott Research Group (ERG) was showing LED backlight drivers at Display Week that were on circuit boards that have the same physical dimensions and mounting holes as the CCFL inverter boards that they are designed to replace (Fig. 4).
Fig. 4: LED driver boards from Endicott Research Group (ERG) are physical replacements for their CCFL inverters. Photo courtesy of Alfred Poor.
NEC LCD Technologies also provides panels for industrial applications. The company has developed a new "Color Xcell" technology that allows the color points to be reset by changing the drivers at the cell level. This provides additional color control and is a feature that will be available in all the company's products eventually. NEC also has seen growing demand for wide-format displays, as well as panels optimized for portrait orientation.
Many other companies exhibited a wide range of LCD panels intended for industrial and other applications. Rockwell Collins showed applications for its Direct Dry Film technology that allows the company to modify bare panels for everything from 3-D tech-nologies to touch screens. Many companies also exhibited high-brightness LCD panels, including INSYNC Peripherals Corp. and Brightview Technologies. GemLight Technologies showed "Sapphire Star" displays that are rated at 2000 cd/m2 or more, but that can also be dimmed to 100:1 as needed.
Different Shapes and Sizes
Some of the LCDs on display were not of the standard 4:3 or 16:9 aspect ratios. Tannas Electronics demonstrated its ability to cut LCD panels to just about any size or shape needed, showing a 5 x 35.5-in. panel that was cut from a 40-in. LCD panel (Fig. 5). FSN also had some novel-sized panels at its booth, including a 1920 x 480-pixel "panoramic" display that it showed in both landscape and portrait modes.
Fig. 5: Tannas Electronics can cut LCD panels to create displays with novel dimensions. Photo courtesy of Alfred Poor.
There were even tiny LCD panels. Perhaps the smallest were the ones shown by Kopin. Their BDM-720P LCD panel has 1280 x 720 pixels – sufficient for HDTV images – in a panel that is just under 0.5 in. on the diagonal. At the same booth, they showed a new SXGA-R5 panel from Forth Dimension Displays (now owned by Kopin) that has 1280 x 1024 pixels on a panel that is just 0.88 in. on the diagonal. Designed for near-to-eye applications such as viewers and head-mounted displays, these panels use ferro-electric LCD technology. Forth Dimension plans to have a QXGA panel available in about a year, with 2048 x 1536 pixels (Fig. 6).
Fig. 6: Kopin's high-resolution LCD panels are less than 0.5 in. on the diagonal. Photo courtesy of Alfred Poor.
Despite of its dominant position in the information-display industry, LCD technology is not sitting still. Big and small, fine resolution and bright, standard or novel shaped, the LCD panel continues to evolve to meet the needs of new applications as they arise. While there are other technologies that show a great deal of promise, it will be increasingly difficult for them to unseat LCDs as the leading way to obtain information from our various electronic devices. •