Of all the trade shows I’ve attended, DisplayWeek is certainly among the geekiest. The annual confab is produced by SID (Society for Information Display). Its main focus is display technology for all sorts of devices, from mobile phones to commercial signage to TVs and projectors. I’m particularly interested in future display technologies—of which there are plenty being presented, and at a technical level that would make most heads spin.
One of the booths I visited this year was Nanosys, maker of quantum dots and QD films used by Samsung, Vizio, TCL, Hisense, and others in high-end LCD TVs. At CES last January, I wrote about the company’s plan to replace the tiny red and green color filters in LCD TVs with red and green quantum dots. Light from blue LEDs in the backlight stimulate the QDs to glow red or green, and the amount of light emitted by each subpixel is modulated by the LCD shutter associated with that subpixel. (The blue filter would be replaced by a clear filter to allow the light from the blue LED backlight to pass through and form the blue portion of the image.)
As the company did at CES, Nanosys showed color filter-replacement (CFR) films with tiny rectangles of QD material deposited by a process called photolithography, which is how color filters are currently manufactured. In a private room, the company also showed me larger solid-green and solid-red CFR films that had been inkjet-printed as a proof of concept. Inkjet printing would be very useful in QD-based micro-LED displays, but that is farther in the future.
Replacing color filters with patterned quantum dots presents two major challenges that Nanosys claims to have overcome. First, the QDs in each tiny area must absorb virtually all the light from the blue LED backlight, which means they must be packed together super tightly. By contrast, today’s QD-backlight films must allow lots of blue light to pass through them, which combines with the red and green light from the QDs to form white light. The company has achieved its goal of less than 1% light leakage through its color filter-replacement film, which allows the system to achieve over 90% of the BT.2020 color gamut.
The other challenge is to allow the manufacturing process to take place in open air. Along with the use of photolithography, this makes the process compatible with current color-filter manufacturing techniques. By contrast, OLED material must be manipulated in a vacuum.
Nanosys says that replacing the color filters with quantum dots can boost an LCD TV’s peak brightness to 3000-4000 nits without requiring more power than current models generate. Even better, we could see actual products that implement QD CFR as soon as next year.
In other Nanosys-related DisplayWeek news, the company received the SID Component of the Year award for its Hyperion quantum dots, which include a low-cadmium green emitter and a cadmium-free red emitter. The new QDs match the performance of full-cadmium formulations—reaching nearly 100% of BT.2020—using less than 100 parts per million of the toxic substance. This complies with the RoHS (Restriction of Hazardous Substances) standard for environmentally safe materials. Congratulations, Nanosys!