PUMPED UP PERFORMANCE
Next to size, faster LCD response time is key to raising these displays to the new levels of performance. "We're continuously trying to improve LCD response times, which used to be in the 40-ms range when the technology started, down to the 12- to 18-ms range, and we're not too far off from the single-digit range," claims Bob Dunhouse, engineering manager for NEC Electronics.
Dunhouse credits a feed-forward technique developed by NEC that momentarily electrically overdrives the LCD's TFT drivers for reaching this speed. As mentioned earlier, such parameters as contrast ratios, brightness levels, viewing angles, and image resolution all interrelate with response times, so improvements in any one or two areas sometimes involve trading off from other performance.
According to Samsung, fast LCD response times may already be here. At the SID Conference, the company reported on getting sub-10-ms response times and blur-free video motion pictures on a 57-in. LCD TV screen, using its S-PVA technology. And, AU Optronics reported on a 46-in. TFT LCD for HDTVs with an 8-ms response time.
As for LCD resolution, a number of strides are being made. One particular example comes from Sharp. The company used its CG silicon know-how to produce exceptionally "sharp looking" and clear LCD panels. Sharp did it for cell phones (300 ppi in a 2.6-in. diagonal unit) and PDAs and notebooks (217 ppi for 3.7-in.-diagonal units). It also has produced a system-on-glass (SOG) LCD technology that uses a two-shot sequential lateral solidification process. It provides the highest resolution (200 ppi) for a 2-in. display with an integrated 6-bit source driver.
On another parameter front, viewing angles are becoming much wider. At the SID Conference, Optrex showed off a TN LCD with a 170° viewing angle horizontally and 150° vertically. Key to the development is a novel background film material. Sharp also demonstrated a 160° viewing angle using its Super Mobile CG silicon. Furthermore, Samsung reported on a 160° horizontal and 140° vertical viewing angle with a 300:1 contrast ratio using a unique transreflective low-temperature polysilicon LCD process with a cap-divided vertical-alignment mode.
Design methodologies are also key to improving viewing angle widths. "We've made many improvements in LCD in-plane switching (IPS) techniques and contrast ratios over wide viewing angles," says NEC's Dunhouse. At this time, the company cannot provide further detail on this proprietary material.
LCOS TAKES ON PROJECTION APPS
Manufacturers of large-screen consumer HDTVs featuring 60- to 70-in. diagonal sizes are taking a look at liquid-crystal-on-silicon (LCOS) technology. Also known as "micro-displays," LCOS-based TVs are projection TVs lacking the main attributes of all other flat-panel consumer TV technologies, namely thin panels and small and lightweight features that allow the TV receiver to be hung on a wall. They employ digital light engines but are still considerably thicker from front to back and bulkier than LCD, plasma-panel, and electroluminescent flat-panel displays.
LCOS technology was pioneered by Brillian Corp., which this year launched a 65-in. Gen II LCOS HDTV with resolution of 1280 by 720 pixels and a contrast ratio of 2000:1. Until now, the contrast ratio of LCOS-based projectors has been limited to a range of 500:1 to 800:1. "This is an extraordinary time in the evolution of HDTV products," says Vincent Sollitto, Brillian's CEO, as he touted the LCOS monitor's "near 3D picture quality and artifact-free performance."
LCOS is somewhat of a hybrid technology between digital light processing (DLP) technology pioneered by Texas Instruments and LCD technology. LCOS combines the reflective aspects of DLP technology with the transmissive qualities of LCD technology. It uses liquid crystals instead of the individual mirrors of DLP, where the liquid crystals are applied to the reflective DLP surface mirrors. As the liquid crystals open and close, light is either reflected from the mirror below or blocked. LCOS-based projectors typically employ three LCOS chips, one each to modulate light in the red, green, and blue channels of the spectrum.
LCOS technology has the inherent advantages of LCDs in terms of large form factors and higher resolution. Yet as the light is projected over a distance over large-size panels, the displayed image loses some brightness, contrast ratio, and resolution.
Because LCOS is more difficult to manufacture in chip form, it also is not as cost-competitive as other large-screen HDTV technologies. Even Intel Corp., which has expressed an interest in mass-producing LCOS TV chips, has delayed its plans. Philips has gone ahead with the technology, exhibiting 55- and 62-in. LCOS rear-projection HDTVs at the SID Conference.
SpatiaLight Inc. developed a different version of LCOS light engine chips that supply contrast ratios in excess of 2000:1. Its 1920 SCDTV microdisplay rear-projection system boasts a 90% reflectivity, resolution of 1920 by 1080 pixels, and overall display throughput of 65%, all on a die of just 18.7 mm in diagonal. The die utilizes a silicon backplane with a highly reflective pixellated aluminum top layer to control the orientation of the liquid-crystal molecules. The backplane contains all of the drive electronics as well as the liquid-crystal control circuitry, which simplifies the required input to the display and reduces the size of the control electronics as well as the overall size and weight of the rear-projection TV.
APPLICATIONS GALORE
The mobile-phone market continues to be the largest application market for LCD flat panels in unit volumes shipped, and it's the third largest in dollar value according to market researcher iSuppli Corp. On top of that, LCD flat panels continue to dominate information-display applications in almost every other market segment.
One obviously huge market consists of PDAs, laptops, notebooks, and desktop computers. Then there's the growing market in consumer multimedia devices, like portable media players, digital video disks, and toys. You can't overlook the burgeoning automotive LCD-display industry either.
"We're getting closer to meeting requirements in terms of environmental capabilities," says Optrex America's Dale Maunu, director of Business Development and Procurement. "One area where this is so is the automotive field, where operating temperature ranges from 30°C to 85°C are possible. For non-automotive applications, we're moving forward toward the 20°C to 70°C range."
Wireless monitors using color LCDs are now in vogue for public information displays. This year, Three-Five Systems Inc. introduced a family of commercially available XGA-resolution (1024 by 768 pixels at 30 frames/s) wireless LCD monitors in diagonal sizes ranging from 15 to 40 in. (Fig. 2).
Outdoor signage is one of the newest and fastest-growing market segments. Recently, Sharp previewed 45-in. LCD monitors with 1920- by 1080-pixel resolution for digital signage applications. Plus, Global Display Solutions Ltd. showed off its 32- and 37-in. e-Signage LCDs at the SID Conference, as well as 32-in. moving-floor units with touch-screen panels for factory floor, airport, railway, bus station, supermarket, and shopping center uses (Fig. 3).
Use of proprietary anti-reflective coatings is helping to give LCD panels higher contrast ratios and better readability in outdoor and direct sunlight environments.
"We serve a multi-environment market for industrial applications with varying degrees of outdoor lighting," says Omid Malanie, director of NEC's Display Business Unit. "As a result, we developed a transreflective technology that does not require backlighting. We're investigating both internal and external transreflective methods, where the former has a TFT layer that's coated with a reflective material, and the latter uses a reflective back polarizer."
Optrex America developed an anti-reflective surface treatment for its 6.5- and 8.4-in. VGA and 12.1-in. SVGA TFT LCDs for high ambient-light readability (Fig. 4). The displays are finding homes in industrial applications. To help in high-ambient-light conditions, 3M Touch Systems came up with the MicroTouch M150 high-brightness, 15-in. TFT LCD monitors (Fig. 5). They deliver 400 nits of brightness and a 430:1 contrast ratio.
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