Aris Silzars Display Technology Consulting

DISPLAY CONSULTING

The Display Continuum

The Bumpy Road to Success – or – Avoiding the Potholes of Failure…

It took LCD technology roughly forty years to overtake CRTs for television applications. It took Plasma Display technology nearly as long. Now, the latest exciting display technology vying for a place in the television and computer display marketplace is OLED. But it too has now been in development for roughly twenty years. Along the way there have been many other attempts to develop new display technologies that either failed entirely or found more limited product applications. For example, the Texas Instruments DLP technology has done well as the light engine in conference room projectors. LEDs had, until recently, found only a modest market for large stadium displays and for a few electronic billboards. Other technologies such as inorganic EL and the various attempts at Field Emission Technologies have not yet become major commercial successes in spite of many years of serious effort.

For a display technology to succeed much has to go right and sometimes even a seemingly trivial problem can lead to failure. For example, inorganic EL displays were having reasonable success as specialty products for instrumentation applications, but as the desire for full-color in displays became more important, the lack of a good blue phosphor limited the viability of this technology.

Even the mainstream LC technology has had an amazingly challenging road to travel. By all reasonable engineering standards this technology has no right to be in the leading position it now holds. The list of potential challenges and problems-to-solve appears dauntingly long:

To begin, the dielectric constant variation that results from LC molecule orientation is quite small.
This small effect can vary with the thickness of the LC layer.
The LC materials are temperature sensitive even in normal ambient environments.
The small variations in dielectric constant are direction dependent resulting in inherently limited viewing angles.
The LC molecular orientation is dependent on surface conditions and stable viewing and good contrast depend on the continued application of a holding voltage.
LC displays have low light transmission efficiency because of the need to use polarized light and color filters.

And this is only an abbreviated list! Nevertheless, this technology had its modest successful beginnings in watches and portable calculators. LCDs provided the needed low power operation that other display technologies at that time could not. From there the technology was able to move into more demanding instrumentation, industrial, and avionics display applications. However, the major applications breakthrough came with the advent of the laptop computer. There was no other display technology that could operate with sufficiently low power consumption to allow for adequate battery life. So even though the first laptop computers had LC displays with monochrome screens, poor contrast, slow response, and limited resolution, they allowed this new category of products to be brought to market. It was a mainstream application that allowed an extensive technology infrastructure to develop.

There is an important fundamental concept that is illustrated by this specific example. For a new technology to succeed it must have the opportunity to enter the market by solving a critical problem and it must allow for the technology to have a period of less-than-perfect performance so that further development can take place.

The amazing end result for LC technology has been that all of the daunting technical challenges have yielded to a solution. The numerous potholes of failure were all successfully avoided. This is indeed a rare outcome. The LC displays that are currently available for laptop and television applications are basically “good enough” for all but the most unusual of circumstances. They have excellent resolution, adequate brightness, good contrast under a variety of ambient conditions, wide angle of view, and adequate response speed to display full-motion video. What else could we possibly want? Sunlight readability is perhaps not as good as it could be. Color gamut will continue to improve with the introduction of LED backlights. But, by and large, we have a display technology that is performing to our expectations and can be considered to be an excellent replacement for CRT technology.

Plasma display technology is today in a similar position of being quite “good enough” for television applications. It did not have the benefit of having a new product category such as laptop computers to aid in its development, but it did get some early help with the neon-orange monochrome display terminals for banking institutions.

Another example of a display technology that has been many years in the making is “electronic paper” from E-Ink. The early excitement and promises of how this technology would replace printed paper have not yet become reality. However, after many years of serious effort there are the beginnings of commercial success with the E-books that are now coming into wider use. How successful this technology will eventually become is still hard to say. But at least there is a reasonable expectation that future commercial viability is possible.

From these examples, we can see that the path from the early demonstrations of a working technology to eventual success is typically a lengthy and seemingly torturous one. Even technologies of more limited scope such as the Texas Instruments DLP have taken many years of dedicated effort before achieving commercial success. And, unfortunately, it can take only one small but significant flaw for a new technology to be cast aside – that tiny but fatal flaw.

In LCDs, it took many years to develop the active matrix technology with a transistor at each pixel along with a storage capacitor to hold the image for the entire frame. In the early days of laptop computers, this active matrix technology was not yet available and those displays were of limited resolution and poor contrast. The fortunate outcome for LC technology was that these transistors only have to switch voltages in the 5-volt range and at relatively slow speeds. This makes it possible to fabricate the large transistor arrays from amorphous silicon using relatively modest photolithography processes.

For Plasma Displays, on the other hand, we had the serendipity of built-in storage once a pixel discharge is initiated. Therefore, while higher voltage drivers are needed, they are only needed one for each row and one for each column. There is no need for a sample-and-hold circuit at each pixel.

Our newest challenger for widespread display applications, the OLED, has struggled for many years to solve problems related to lifetime degradation of the light emission process. It appears that perhaps this part of the bumpy road is now coming to a successful end. Given the potential image qualities and overall efficiency of this emissive technology, this could be a major step forward to successful large-scale commercialization.

And even field-emission technology – a technology that has struggled for so long that it has almost become the standard bearer for “things that will never work” -- may be showing signs of success with the recent new efforts in Japan. If manufacturability can be proven, this technology could also produce outstanding picture quality.

It is exciting to see that even as LCDs have come to dominate the display market place that there are still others willing to take risks and put in the intense effort needed to traverse the bumpy roads of new display technology development. So much has to go right and it only takes one serious pothole to eliminate a new technology from the race to commercial success. We scientists and engineers must surely be a tough bunch to be willing to undertake these pioneering efforts over and over again. The “goodness” in all this is that at times we succeed even beyond our own expectations.

Should you wish to comment on this column or on another topic, you may contact me by e-mail directly from this site or call me at 425-898-9117.