Quantum Dots made their debut at CES 2015: Here is how they work
Stephan Jukic – January 10, 2015
If there’s one display technology that received an inordinate amount of attention at this year’s CES, it was something called quantum dots. Both Samsung and LG promoted the now famous dots in select models of their latest 2015 4K TVs and they weren’t the only ones present who had something to say or show about this new development.
Given all the hype, you’re probably wondering just what quantum dots are and what they means for ultra HD TV picture quality. After all, with LED, LCD, OLED 4K and UHD as the existing key tech acronyms to keep track of, who wants yet another thing clouding up the scene?
Fortunately in this case, quantum dots are a very real thing and they’re worth paying some attention to as one of the “buzzwords” for 2015 TVs.
In simplest terms, quantum dots are tiny elemental particles (about 10 thousand times narrower than a human hair) that glow when subject to a source of light. When a very large number of them is placed on a very fine sheet of film and that film is then exposed to a strong source of directed light, the dots polarize into different colors and shine brightly enough to create a notably better picture than what you’d get without them. Thus, the latest 4K TVs with the quantum dots built into them have exactly the sheet of thin film mentioned above installed right in front of their very bright full array LED lighting systems that sit at the back of the screens.
This is the very simple explanation for this interesting new technology, now down to some more concrete details.
The technical terms for quantum dots is “nanocrystal semiconductors” and instead of actually being a whole new display technology (as they’re often referred to as) they’re really just a new part of the much wider series of systems that makes up the entirety of your 4K TVs overall display.
Most importantly of all, quantum dots do two fundamental things better than a normal LED LCD screen can: they fix the problem of light glare that happens to TVs with LED backlighting and while fixing this problem, they also produce far more vibrant color overall.
When it comes to the way in which quantum dots work inside an LCD TV, we need to go through a brief rundown on how LCD TVs themselves work, and where they get deficient.
The three key parts of an LCD display are the LED backlight, color filters that turn that light into tiny points of red green and blue light and a liquid crystal grid of millions of tiny “windows” through which the colored light from the LEDs and filters passes.
These little liquid crystal “windows” are in fact the pixels inside the TV and they open or close in different ways to blend those three core colors into images. Since each of these liquid crystal pixel windows has its own internal red, blue and green subpixels, they can open and close these to create distinct colors.
Thus, by mixing the amount of light from different subpixel arrangements, a TV can create all the colors and tones we see.
The problem arrives when LED lights in modern LCD TVs try to produce white light. Because white LEDs are actually blue LEDs with a coating that makes them appear white, the color that is created in fact has a sort of bluish off-white quality that anybody familiar with the ugliness of fluorescent lighting will recognize well. This off-white white, when mixed with the red and green colors in the TV then creates a less than clean spectrum of all the other colors your TV tries to produce.
The result of this problem, as of recently, has been a race by engineers in the R&D departments of select TV makers (mainly LG and Samsung) racing to find a way of creating a cleaner source of white that will make all the other colors produced from it look more accurate, closer to the vibrancy they’d have in real life.
This is where quantum dots fit into the picture.
As we’d already mentioned, quantum dots are really, really tiny crystals that glow when illuminated by light. The colors in which they glow depend on their size but because technicians can now control that size really carefully by adding or taking atoms away from each dot, the light each dot creates can be almost perfectly controlled.
Furthermore, quantum dots, once built into place in their substrate, are very stable and can keep their specific color capacities for a long time and each individual dot can thus also keep its particular shade of color stably.
Once this was developed in a feasible way for TV screens, designers at the major electronics companies started producing sheets of quantum dot saturated film filled with dots that have been constructed to glow in precise shades of green and red.
These red and green dots are scattered all over the film and not organized into any perfectly engineered pattern of subpixels but this doesn’t really matter, because what the dots really achieve is to allow the blue light of the LEDs behind the quantum dot film to hit them and in doing so create a much “cleaner” white light that the regular LCD filter we’d already discussed can then convert into much better blue, green and red colors that in turn allow a much more realistic overall spread of colors on the screen.
Because the original ugly direct blue light of the “white” LEDs has now been filtered and cleaned through the quantum dot film, the screen colors themselves lose the damage done to them by having bluish LED light directly hit the LCD screen’s red, green and blue filters.
This is how quantum dot based LCD TVs produce way better, more natural looking color gamuts than normal LCD TVs, and this is why Samsung, LG nad other companies are all so interested in seeing this technology move forward in their 4K TVs.
Story by 4k.com