For a flat-panel display technology that's relatively more mature than other competitive approaches, liquid-crystal displays show an unstoppable trend of improvements in all key performance aspects of flat-panel displays: contrast ratio, color display brilliance, response time, viewing angle, and resolution. All of this applies across a very broad spectrum of display panel sizes, from micro-displays of an inch or smaller in diameter to very large displays of 60 inches or more for consumer and outdoor applications.
Much of the progress in LCD technology can be traced to process improvements and innovative design approaches, many leading to decreasing unit prices and a greater presence in a host of applications. While competitive approaches like CRTs, plasma discharge panels, electroluminescent displays, and organic LED (OLED) displays are making their own impressive gains, they're increasingly facing stiff competition from LCDs for flat panels and eventually winding up in more specific and "niche" applications.
SIZE DOES MATTER
Because of its pursuit of the large-screen consumer TV market, size is of paramount importance to LCD screen manufacturers. Developments in digital high-definition TV (HDTV) technology continue to push color LCD large-screen technology, even though its market share is still small. That should change, though, with large-scale investments in LCD production facilities and frenetic efforts to improve liquid-crystal performance for consumer HDTV applications (see "The Business of LCDs," p. 62). Of course, size and other important parameters such as response time, resolution, brightness, and viewing angle are all interrelated. Each of these areas is seeing marked improvements.
At the Society for Information Display (SID) Conference, Samsung announced a super patterned vertical alignment (S-PVA) technology that sets new state-of-the-art color performance for LCD TV screens. The company also announced the development of a 57-in. UXGA (1920 by 1080 pixels) LCD TV, the world's largest for HDTVs, with sub-10-ms response times and a 1000:1 contrast ratio. The S-PVA technique employs new color filters with a contrast ratio that's superior to presently used filters, because the liquid-crystal optical path is perfectly parallel to the optical path.
LG Philips reported good results in color-image quality for television-bound large-diagonal (up to 50 in.) LCDs using its super in-plane switching (S-IPS) technology. IPS LCDs may also provide better viewable angles than twisted-nematic (TN) LCDs. The main limitation of IPS and S-IPS technologies is that they require more power and may have a slower response time than a TN LCD.
Taiwan-based AU Optronics reported on a 46-in. TFT HDTV LCD that uses multidomain vertical-alignment (MVA) liquid crystals for color management and image enhancement that produce high-quality color (75% of the NTSC color gamut), bright (600 nits), and high-contrast-ratio (800:1) images. In MVA, the molecules of liquid crystals are normally aligned at right angles to the substrates, swinging through 90° to lie parallel with the substrates in the presence of an electromagnetic field.
This new mode produces a display that has an ultra-wide viewing angle (140° in all directions) and a high contrast ratio. It also features higher brightness and a response time of about 25 ms, which is shorter than IPS, super twisted-nematic (STN), and TN LCDs. The display consumes less power than IPS, but it is still too power hungry for battery-sensitive applications.
When it comes to the Qualia series of 40- and 46-in. LCD TV sets, Sony goes the route of LED backlighting. According to Sony, a large gamut of reproducible color hues is possible using backlighting LEDs, offering vivid, realistic scenes not possible by other techniques.
Samsung also uses LED backlighting on its TV sets, which the company says solves the life-span and color-quality limitations of traditional fluorescent backlighting lamps. The same can be said for NEC-Mitsubishi Electronics Display of America. In addition, many companies at SID, including Sharp and Toshiba, as well as LG Philips and Samsung, either exhibited or talked about LCD products with diagonals of 45 in. and larger that offer a resolution of at least 1024 by 1280 pixels.
If it hasn't already done so, Sharp will soon be in production with a 45-in. LCD color screen. The company is a leader in automotive color LCDs primarily for rear-seat entertainment. Sharp, which pioneered continuous-grain (CG) silicon technology, has shown that CG silicon can produce exceptionally crisp high-readability color LCDs for cell phones (Fig. 1).
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