Patricia E. Cladis Pictures are the broadest band of information humans can process, making electronic displays an important interface between human customers and an increasing variety of multimedia, broadband, and mobile communications services expected to become even more important in the 21st century. While creating new markets of its own, the technology of choice for multimedia applications is the thin-film transistor liquid crystal display that is a fusion of fine processing silicon technology on a large area dielectric, the display panel, and the oldest liquid crystal display technology, the twisted nematic.
Liquid crystal displays are no longer only seen in watches, parking meters, gasoline pumps, and calculators, but now are also colorful, high-resolution, low-power consuming and fast displays creating new (portable) products such as videophones, personal communicators, videocamcorders, laptop computers, and car navigation systems. LCDs are also revolutionizing old products, such as displays used in avionics and domestic television.
Display technologies other than the CRT are known as flat panel displays; "nonemissive" flat panel displays refers to those technologies that do not emit light. For example, in the only nonemissive display technology, LCDs, liquid crystal materials act as electrically-controllable light valves for an external source of light, and use color filters rather than phosphors in their color displays (see Liquid Crystal and Other Nonemissive Displays for detailed descriptions of LC technologies).
When this light valve is a simple shutter, monochrome displays (bright or dark) can be made with large contrast ratios (the ratio of light intensity of the bright state to that of the dark state). A continuous grey scale is obtained when the light intensity varies continuously from fully off to fully on with increasing applied voltage. In combination with RGB color filters, a continuous grey scale can be used to make a true color display, the most powerful of all displays. In TFT LCDs, 16.7 million colors are now possible (shown, for example, by the Sharp Corporation at the 1992 Japan Electronics Show in Osaka, Japan).
Once a true color display is seen, multicolor and monochrome displays are unacceptable to many customers in the same way black-and-white TV is unacceptable to viewers of color television. A brightly-colored display is cheerful and friendly. Product enhancement from a color display can outsell an equivalent monochrome product in the consumer market.
About 90% of the world supply of LCDs (and virtually 100% of TFT LCDs) are manufactured by Japanese leaders in the semiconductor industry. According to a Nikkei Microdevices survey, since 1989 LCD production of both passive and active LCDs has grown in Japan at a staggering 35% annual rate (in yen) to about $3.5 billion (435.5 billion yen) in 1991. In 1992, the total LCD growth rate slowed somewhat to a still phenomenal 20%, reaching $4.7 billion (516.5 billion yen), with the TFT LCD sector reporting an outstanding 161% growth (to $1.2 billion or 132.2 billion yen) (Nikkei 1992). According to NEC and Sharp executives, "Nothing has changed the outlook for a 1 trillion yen liquid crystal market (in Japan) by 1995" (Nikkei 1992).
Indeed, Figure F.1 shows that Asada (a Sharp vice-president) was right on track (Asada 1990) for the LCD world market, where the 1 trillion yen mark is expected by the turn of the century.
Figure F.1. Asada's 1990 view of the display business by technologies (Asada 1990).
It is interesting to note that during 1988-1989 most U.S. and European companies abandoned R&D and plans to manufacture LCDs because they were perceived as a cheap component, not strategic to consumer markets and available in large quantities from Japan. While this is correct for small alphanumeric displays, now the superb picture quality (without introducing health hazards) and outstanding color of TFT LCDs make them strategic to ever-more-sophisticated consumer products.
In fact, the price to the consumer of a product made by assembling high-value-added components from overseas may be higher, but not necessarily better, for consumers compared to similar products from companies with a manufacturing capability of at least the strategic components. In view of the trend in silicon microelectronics towards smaller, faster, and cheaper devices, one not entirely impossible projection is that, as TFT LCD technology evolves, microelectronics will migrate to the display panel, leading to a paradigm-shift in product design when the display panel is the product and there is nothing left to assemble.
Because of their strategic importance to the rapidly evolving and ever expanding high-tech market for consumer-oriented services and goods, LCDs are a very well-studied technology both in Japan and in the United States (Nikkei 1992).
By microelectronic standards, the STN technology is very mature. Its customer base that has held up, and may even be growing, are electronic games using small displays. Another is the laptop computer market, particularly for color STN displays. Small, high-quality alphanumeric displays are a commodity in the world market and are sold in large quantities by weight rather than by piece count -- with excellent customer service to support their use.
A widely-held opinion that has driven the rapid development of TFT LCDs is that STN LCDs and MIM LCDs cannot satisfy the performance demands of future broadband, multimedia communications. While STN (and MIM) supporters look to innovative driver chips (1,400 MIPS control LSIs) for the new addressing techniques known as "active addressing" to improve STN color range and speed, others feel that this is only shifting the burden from a more expensive display panel with better picture quality to more expensive driver chips that are already an expensive part of high resolution displays.
Another area of improvement for STN is the replacement of glass substrates with lighter-weight plastic ones, bringing down the overall display weight. Indeed, as of this writing, Sharp was scheduled to start shipping small, monochrome STN displays on plastic substrates with VGA resolution (640 x 480 pixels) in the summer of 1994 (Journal of Electronic Engineering 1993).
Because of reduction in investments starting about three years ago, STN technology in Russia was effectively frozen at that time, which is a long time in this business.
While there are many applications for STN displays, and probably even more innovative products to come, large investments are being made in parts of Asia in TFT LCDs, particularly in those countries that already have STN factories. For example, as far back as two years ago, a prototype line reportedly replaced the MIM line at the Electronics Research Service Organization (ERSO) of the Industrial Technical and Research Institute at Hsinchu, Taiwan (Chen and Wu 1993). Taiwan has at least two STN plants, one with Hitachi, and the other one with Sharp. Since then, as TFT LCD technology approaches maturity, plans, funded by both government and industry, have been activated to mass-produce TFT LCDs in Taiwan and South Korea.
Asada, Atsushi. 1990. "Electronic Displays: A Revealing Look at the Latest in LCDs." Display Devices Dempa Publications, Inc. Jul.:30.
Chen, H.K., and B.S. Wu. Private Communication. ITRI/ERSO. Hsinchu, Taiwan.
Journal of Electronic Engineering. 1993. "TechWatch" (No Author). Dempa Publications, Inc., New York, NY. December:16.
Nikkei Microdevices. 1992. Flat Panel Display 1993. Dec. 10.