Nano boost: A film loaded with quantum dots (left) can be added to an LCD to improve its color gamut. The film converts some of the blue light emitted by the screen’s backlight (right) into red and green light.
A layer of nanomaterial that gives a liquid-crystal display the rich range of colors usually possible only with more expensive technologies will be commercialized later this year by the materials giant 3M and Nanosys, a private company in Palo Alto, California. Nanosys representatives say they are in talks with major display manufacturers to adopt the quantum-dot films, and that they will be in a 15.6-inch notebook computer available next year.
Liquid-crystal displays (LCDs) dominate the market for both televisions and portable electronics. For many years now, manufacturers have concentrated on making LCDs on a large scale at ever lower costs, to the point where they have become commodities. Meanwhile, more expensive display technologies based on organic light-emitting diodes (OLEDs) have come along, offering richer color and, in some cases, better power consumption, but at a higher price.
Representatives from Nanosys say their film—a sheet of plastic embedded with nanoscale spheres of indium-phosphide and cadmium quantum dots—makes it possible to match the color gamut of an OLED in an LCD, without any changes to the manufacturing process, and without adding much cost.
The LCDs used in today’s portable electronics use white light from a set of light-emitting diodes at the edges of the device. Liquid-crystal shutters guide the light, and color filters add hue to it. White light sources are expensive, so these displays use blue light-emitting diodes coated with phosphors that convert their output into white light.
The Nanosys-3M film simply takes the place of the phosphor in this stack of components. Quantum dots in the film convert about two-thirds of the blue light from the backlight into red and green light. Compared to the white light from a conventional LCD, more of the red, green, and blue light passes through the color filters, and the images are brighter and more richly colored.
3M embeds quantum dots from Nanosys in sheets of plastic coated with a film that protects against moisture and oxygen. This plastic sheeting replaces an existing LCD component already sold by 3M, a layer called the diffuser, which evens out the light before it goes into the screen’s filters.
According to Nanosys representatives, a typical high-end LCD provides only about 70 percent of the color range in a standard called Adobe RGB, while an LCD with this film provides the full gamut (as does an OLED display).
Other quantum-dot makers, including QD Vision of Lexington, Massachusetts, are also working on LCD components, but Nanosys is the first to declare a partnership and launch date. Nanosys tried launching a similar product a few years ago, and in 2010 it demonstrated a prototype cell-phone display made with Korean company LG (see “Colorful Quantum Dot Displays Coming to Market”). But that version—which required manufacturers to incorporate a glass capillary filled with quantum dots into the display—didn’t take off because adding the extra component was too complicated. “There were mechanical concerns,” says Jian Chen, director of device technologies at Nanosys.
Nanosys hopes the familiar face of 3M, and the fact that there is no need to change the manufacturing process, will help it work this time around.
“Quantum dots are no longer a lab curiosity,” says Moungi Bawendi, a professor of chemistry at MIT who is on the advisory board of Nanosys rival QD Vision. But companies have struggled to find the right markets for the materials, and today they are only used for niche applications such as biological imaging.
QD Vision launched a lightbulb coated with the quantum dots in 2009 (see “Quantum Dot Lighting”). The product didn’t do well, in part because the lighting market is so fragmented, says Bawendi.
Displays may be different. “It’s just a matter of picking the right markets,” he says.
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