Thinning Down the CRTby John BoydBack in the April issue, I wrote about how the manufacturers of liquid crystal displays (LCDs) were gearing up to boot our big, bulky cathode ray tube (CRT) monitors right off our crowded desktops. With CRT technology maturing quickly and LCD screens just starting to get bigger, brighter, and cheaper, it seemed the inevitable result had to be "sayonara" to the 50-year-old CRT fatso, and hello to slim-line LCD monitors. But now, along come a handful of companies developing full-color Thin CRTs that are seriously expected to grab market share from LCD manufacturers in areas ranging from consumer electronics to PC notebook displays. One of these companies, a Silicon Valley start-up called Candescent Technologies, has been able to raise $230 million in funding since its inception in 1991 (about half of that coming in the past 15 months), including investment from Hewlett-Packard and Compaq. The company could become "a billion dollar start-up," if it completes manufacturing contracts with two new production partners this year, says Nick Sturiale, director of marketing at Candescent.
Only the big survive But where is "there"? For Candescent, it's the ability to produce Thin CRTs with the viewing quality of traditional CRTs, in the form factor and price range of active matrix LCDs. And just how Candescent is going about getting to that point makes for an interesting story. Recall that in the CRT on your desktop, a heating cathode filament generates electrons. These particles are collected and fired by an electron gun at a color phosphor screen on the business-end of a bell-shaped vacuum tube, which can be hundreds of millimeters long. The beam of electrons scans the screen 72 times a second, generating colored light from which the images we see are formed. Candescent's Thin CRT, by comparison, uses a cold cathode technique: a semiconductor technology that generates electrons at room temperature, without the heating process of conventional CRTs. The Thin CRT consists of two pieces of glass fixed about a millimeter apart. One of the glass pieces (the faceplate) is coated with conventional color phosphor, while the other (the baseplate) incorporates an array of millions of nanonmeter-sized cathodes. Some 2,000 cathodes are used to generate each sub-pixel: 6,000 to generate the three primary colors (red, blue, and green). Built-in redundancy ensures that up to 20% of the emitters can be defective without noticeable deterioration of the image.
Low power, low cost, high speed Its response time is also 10 times faster: 5 milliseconds, versus 50 milliseconds for the AMLCD, claims Candescent. This makes it much better suited to fast multimedia action, and means there will be no submarining of the cursor when you move the mouse quickly. And, being a CRT, the viewing angle is superior, which is why Japanese auto manufacturers are keen to procure samples to test in their car navigational systems that are now all the rage. Other companies besides Candescent are competing in this field, including Japan's Futaba KK and US-based PixTech, Micron Technologies, and Motorola. Like Candescent, they have begun (or are preparing) to ship samples. But according to Sturiale, Candescent has come up with some unique technologies and manufacturing methods that give it an edge. While AMLCDs are one of the trickiest of semiconductor technologies to manufacturer, Candescent argues that its Thin CRT is far less complex because it requires fewer process layers, uses fewer special materials, and faces fewer alignment problems. This will result in a fabrication plant costing about one-third less than an equivalent AMLCD plant, the company claims. The first such plant is to be established in the US, a business plan that resulted in the US Department of Defense investing $22.5 million in the venture. Two more plants are planned overseas - one, at least, in Asia - with Japan a strong candidate. "We must be an international company," stresses Sturiale. By the time you read this, Candescent will be producing 320 x 340-mm engineering samples. It will switch to pilot manufacturing of 550 x 650-mm displays in 1998. And in 1999, it will begin production of Thin CRTs for notebook computers, with the aim of becoming a billion dollar company by the turn of the decade.
John Boyd writes illuminating articles for a number of publications, including the
Japan Times and CMP's TechWeb Internet news service. If you're in need of further enlightenment, you might try sending fail mail to John at boyd@gol.com.
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