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The Miracle Liquid…

In the mid-60s some interesting work was done at Sarnoff Labs in Princeton that demonstrated the capability of a liquid crystal-like material to modulate light. It seemed that there might be some limited use for such a material – perhaps in simple numerical displays – possibly watches or instruments. Inherently, displays made with this new liquid were temperature sensitive, slow to respond, had poor contrast, and a limited viewing angle. The need to polarize the light in order to see the image caused significant light loss. To try to do a color display would require the addition of filters and even more light loss with less that 10% of the light getting through.

lcd fire

Nevertheless, researchers persisted and by the mid-90s laptop computers began to show up with displays that were pixelated into rows and columns. This was a major advance from the segment-addressed displays that were suitable for watches and instruments. However, these displays were only useable for word processing and other applications that did not require fast response. However, even with design refinements, such as dual-scan addressing, the contrast was poor and the viewing angles severely limited.

So after 30 years of development from the mid-60s to the mid-90s, we were only able to make displays with liquid crystals for limited applications. And even in these applications the image quality was marginal.

At the major display conferences, there were technical presentations describing new designs that put an active storage element, such as a transistor and a capacitor, at each picture element. However, the consensus among display experts was that this approach would be a very expensive proposition. Semiconductor technology would have to be used on a scale that was much larger that any silicon wafers. And not only that, the yield would have to be much higher than in a typical silicon process where defective parts are simply discarded. It would not be possible to do this with a display of useful size. The most optimistic projections for active matrix displays were that they would eventually reach sizes no larger than about 20-inches in diagonal measure.

And then miracles happened! LC materials were developed that were less temperature sensitive. The speed of response improved to be even faster than needed for video applications, The inherently poor contrast and limited viewing angles were overcome with various new structures such as multi-domain cells. Manufacturing costs for active matrix backplanes were reduced to be competitive even with the inherently simpler structures of CRTs. Backlight efficiency was improved and large displays could be made that were energy efficient.

Every limitation was overcome to provide displays that ended up better than any and every other technology. CRTs were not suitable for laptop computers or other portable products and were limited on the upper end by weight and bulk. EL could not do full color. FEDs failed miserably for a variety of reasons. Plasma displays tried to be competitive at the larger sizes but in the end could not keep up. Conference room projectors still have some market but are being replaced with large LCD panels.

How was it that a thin layer of soapy liquid became not only the dominant display technology but for all practical purposes the only one? There is no inherent law of nature that I can think of that would have predestined this outcome. Why all the pieces fell into place and why all the inherent limitations could be overcome will be something that we can ponder over and appreciate as we view our 65-inch and larger Ultra-High Definition televisions and communicate on our cell phones with their 500 line/ inch ultra-sharp displays.

Should you have some thoughts on this topic or others you may reach me directly from this site, by e-mail at CONTACT or by telephone at 425-898-9117.

 

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