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 isan 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.
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 × 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). 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 × 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 nfor 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-ASketch 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).
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