by Ken Werner
For the last couple of years, LG Display (LGD) has shown a 65-inch rollable OLED-TV screen in its analyst/media/customer suite at CES. This year, LG Electronics (LGE) introduced the LG Signature OLED TV R rollable television set to the public with high-voltage fanfare (Fig. 1). The set is a 65-inch, 4K, OLED TV whose screen rises from a slot in its oblong base. The set can operate in different modes with different screen heights protruding from the base.
At LGE’s press event , LG showed videos of the OLED TV Rs in multi-million-dollar apartments with window walls and magnificent views — views you would not want to block with a conventional high-end TV screen. On the evidence of these videos, LGE sees the market for these TVs as the Mar-a-Lago social set. On the show floor, LGE had five of the roll-up sets continually going up and down, and they drew a self-refreshing crowd.
But, although LGE was giving the OLED TV R what looked like a major product roll-out, it’s unlikely the set will be available before the end of the year, if then. An LGD person said LGE intends to wait and see how Samsung responds. I don’t understand that because Samsung doesn’t have a flexible, large-screen technology with which to respond.
Samsung dominates the market for flexible RGB OLEDs for smart phones, but they do not have the display technology or manufacturing facilities needed to make TV-sized flexible displays at an acceptable cost. Samsung has announced it is working on QD OLED, which would use a blue OLED layer with red and green quantum-dot color convertors. At first look, it doesn’t seem reasonable to base a display technology on the least efficient and shortest-lived of the OLED emitters. But let’s switch to a different starting point: LG’s “color by white” OLED technology. LG deposits unpatterned “white OLED,” which is a combination of blue and yellow OLED, which together make “white.” The light passes through an RGB matrix color filter much like the filters commonly used in LCDs.
What’s wrong with this? Well, matrix color filters are an expensive component and they also absorb a lot of light, thus reducing efficiency. You might expect that the blue OLED emitter in the mixture might age more quickly than the yellow and cause the white point to shift. However, painstaking testing over thousands of hours by RTINGS.com indicate the white point is stable over many thousands of hours except where burn-in has taken place. Still, Samsung’s QD OLED approach would remove the possibility of differential aging in the components of the OLED mix since there would only be one component. Since the QD OLED approach efficiently converts colors with the quantum dots instead of filtering them, luminous efficiency of the stack could improve significantly — except that Samsung is finding it must use a matrix color filter to eliminate the blue light that leaks through the green and red subpixel areas because the quantum dots in these areas do not convert 100% of the blue light.
Samsung has announced it is working on QD OLED, but has been cautious about sharing the details. Blue OLED lifetime and efficiency must be significant challenges, and the QDs will have to be patterned. That has already been demonstrated by a Chinese partner, but not yet in any quantity. However, if the challenges can be met and costs contained, Samsung would have a flexible OLED display that could be used in a rollable TV — if the company concludes there is enough of a market to make the effort worth while.
Since we have not yet seen even a technology demo of QD OLED, it is unlikely that Samsung will have a product to challenge LG’s OLED TV R for the next two years. LG does have a habit of worrying about what Samsung will do, but this time the road is clear.