Look around anywhere and you're bound to see flat-panel display technology at work—at the office, your doctor's office, bank and retail-store terminals, your home, your car, wherever. Most notable in this arena are large-screen (diagonals greater than 30 in.) consumer TVs, where liquid-crystal displays (LCDs) and plasma-panel displays (PDPs) are trying to compete with the venerable CRT. Rear-projection technologies using digital mirror devices (DMDs) and front-projection organic LED (OLED) technology are also mounting a challenge for large-screen dominance.
The CRT is still king in large-screen displays, mainly due to its high resolution, large grayscale range, and ability to show motion without any artifacts, all at an amazingly low price compared to flat-panel displays. Performance in non-CRT displays, particularly LCDs and PDPs, continues to improve while costs come down. Nevertheless, they still command prices of several thousand dollars, a price point too high for many mass-market consumer TV applications. They're seen mainly in high-end premium TVs.
One dark-horse candidate, the electroluminescent (EL) display flat panel, could figure more prominently in large-screen consumer TVs mainly due to its inherently low-cost manufacturing advantages. For instance, iFire Technology has demonstrated a "color by blue" technology that promises to cut costs even further for large-screen thick-film EL panels (Fig. 1). The company estimates that it will cost 30% to 40% less than other flat-panel display technologies.
The "color by blue" EL panel features performance on par with commercial TV products now available. Luminance is 600 cd/m2 (greater than 300 cd/m2 with contrast enhancement). It also boasts a 500:1 contrast ratio, a white-color temperature of 10,000 K, and a color gamut that meets 118% of EBU standards and 85% of NTSC standards. The new color technology uses a high-luminance inorganic blue phosphor, combined with special color-conversion materials that absorb the blue light and re-emit red or green light, to generate other colors.
Commercial volume production of 34-in. diagonal HDTV display modules is expected to begin in 2005. Production will be done by Dai Nippon Printing in Japan. In addition, iFire has a nonexclusive technology agreement with Sanyo to develop 34-in. diagonal EL displays.
EL displays aside, LCDs, PDPs, and rear-projection TVs will garner more and more of the total worldwide dollar market over the next few years, although their total numbers will grow more slowly. That's according to a study by iSuppli/Stanford Resources, presented by senior vice president David E. Mentley at the last SID Conference (Fig. 2). No matter what type of flat-panel technology is used, LCDs now capture about 80% of the total dollar volume spent on flat-panel displays worldwide. They dominate the scene in notebook and laptop computers, monitors, and small-screen TVs (less than 30-in. diagonal). Not surprisingly, most technological advancements are occurring in LCDs.
LCD'S CONTINUAL FACELIFT
Consistently, LCDs show marked improvement in all performance aspects, including readability, response times, and driving characteristics, with low-cost manufacturing as a major objective. One example is a 30-in. thin-film transistor (TFT) LCD public-information display from Global Display Solutions that's sunlight-readable and viewable under all weather conditions.
Some semiconductor companies with large fabrication facilities, like Samsung, believe that they have the edge in reducing LCD manufacturing costs because they can amortize their production costs by using existing fabrication facilities. Last month, Samsung announced an 1870- by 2- by 200-mm glass substrate for its seventh-generation TFT LCD line, which will allow for the production of 32- and 40-in. diagonal TFT LCDs. Samsung has already demonstrated the largest diagonal LCD panel, a 54-in. prototype.
LG Philips, a joint venture between Netherlands-based Royal Philips Electronics and South Korea-based LG Electronics, has already introduced a 52-in. prototype active-matrix LCD color panel that it intends to mass-produce by year's end (Electronic Design, Jan. 20, 2003, p. 24). At the Society for Information Display Conference in May, both prototypes on display showed brilliant and clear color images (Fig. 3).
The LG Philips prototype uses Philips' super-in-plane switching technology to achieve 12-ms response times. It's another indication of the improvements in LCD switching times, which are now at 10 ms or less for smaller-size displays, making for fewer smearing effects as can be seen in the Sharp's AQUOS line of TVs with LCD panels.
Active-matrix LCDs (AMLCDs) continue to be the major technique used for portable and desktop displays due mainly to their low power consumption, light weight, and sharp image quality. Yet AMLCD backlighting lacks efficiency. No more than 10% of the backlighting output is emitted from the display's front to the viewer, because the polarizer and color filters absorb much of this light. Blocking effects caused by a limited aperture ratio for each AMLCD pixel is another reason.
Attempts to solve these impediments employ field sequential color-illuminated LCDs and static illumination. A novel method proposed by IBM is to use a linear fluorescent lamp with a special collimating optical structure as well as discrete LEDs. IBM researchers in the U.S. and Japan have also proposed a pixel-level data-line multiplexing technique for amorphous-silicon AMLCDs. It allows for the reduction of data drivers by one-half or less, without the need for a large number of demultiplexing circuits, no increase in gate-driver circuits, or a special scaling graphics processor. Reports show that this improves an AMLCD's power consumption and costs compared with conventional methods now in use.
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