Nanosys Has Slight Edge On QD Vision in Race for Quantum Dot Patents

Nanosys, which has a partnership with 3M to produce quantum dot-based optical film, has been granted 125 patents stretching back to 2006 and has another 171 pending covering methods for making quantum dot films, nanocrystal light-emitting diodes, light-emitting nanowires, nanowires for fuel cells and medical devices, nanomemories, photovoltaic devices and nanocapacitors. In contrast, QD Vision has been granted seven patents for illumination and backlights dating to 2006-2007, but Chief Technology Officer Seth Coe-Sullivan also was issued four patents and has 37 pending applications. Three of Coe-Sullivan’s granted patents, which date to 2004-2005 and were assigned to the Massachusetts Institute of Technology, cover light-emitting nano-crystals and quantum dot color conversion. Eleven of Coe-Sullivan’s patent applications have been supported by military or government funding. QD Vision has claimed it has more than 200 patents in “various” stages, while Nanosys has 211 display-related patents (CED May 28 p1).

The patent filings variously describe a nano device having dimensions of less than 500 nanometers -- about one hundredth the width of a human hair. Quantum dots are nano-size semiconductors that emit light when excited with the light’s frequency and color depending on the dot size. The dots may emit light of one color when excited by light of another color. Because quantum dots’ surface area is large compared to their volume, the emitted light can be very bright.

In contrast to Nanosys’s film-based approach, QD Vision’s quantum dots are assembled into a glass capillary optical component, integrated with a standard gallium nitride-based blue LED and inserted between an LCD panel’s LEDs and lightguide. The quantum dot phosphors convert blue LED light, which excites them, into different wavelengths based on their size. The larger, seven-nanometer-wide red quantum dots produce longer wavelengths, while three-nanometer green dots have shorter ones. With QD Vision, products typically contain 1-2 of the quantum dot packages and the technology adds less than 10 percent to the bill of materials cost, company officials have said. The glass capillary approach also has a higher operating temperature than film, making it better suited for small volume production, QD Vision officials have said. Coe-Sullivan’s patent applications cover a variety of QD-related topics, including patterned ink-jet printing with nano-ink, quantum dot lighting, photovoltaic solar cells, nanocrystal surface coating and films and blue and white light emitters.

Nanosys’s patent portfolio appears to reach outside quantum dots. A search of patents and applications using the words “quantum dots” turned up 39 applications and 33 patents granted to Nanosys. The filings are meshed in a complex web of competing filing dates that create fertile ground for legal debate over invented and filed-first for key aspects of quantum dot lighting for TVs. Nanosys filings mentioning quantum dots date to April 2002, but early mentions are often in the broader context of photovoltaic and memory devices, optical amplifiers, junctions, waveguides, light concentrators and tagging materials. Several filings from Nanosys in 2003-2004 focus more tightly on multi-color light-emitting nanocrystals and diodes.

Among Nanosys’s early patents was one it first filed for in 2002 that described using nanowires and nanotransistors in LCD and OLED screens, with their small size ensuring minimal blocking of light, creating a brighter picture. A second one granted in 2006 revealed a dense and flexible web of light-emitting nanowires made from gallium, indium, cadmium and sulfur compounds that were chosen to emit required colors. The second patent “opens the door for many applications which are unimaginable with other technologies,” Nanosys said.

Nanosys, however, appeared to be hedging its bets. A 2007 patent application discusses a technique for down-converting the frequency of light -- a method for changing colors -- with nanocrystals made from gallium, selenium, zinc and sulfur. In the patent, when a blue LED is shone on nanocrystals, some emit green light and others red. Part of the original blue light source is combined with red and green emissions to generate a bright, pure white. To protect nanocrystals from being damaged by oxygen in the air, they are sealed in glass capillary tubes slightly larger than a human hair. A patent granted in 2012 builds on the down-converting, claiming a plastic film containing quantum dot nanocrystals that could be used for TVs, PCs, PDAs, cellphones, e-readers and gaming devices.

A QD Vision application filed in 2006 describes a semiconductor comprised of zinc, cadmium and sulfur which emit blue light. A second patent filed a year later covers a method for a self-illuminating “electro-wetting” screen for pocket devices in which quantum dot particles are suspending in a fluid layer over a light source. Another patent, filed for in 2007, describes a solution of quantum dot particles that can be applied to a substrate and paired with a photomasking technique to get a patterned dot coating. QD Vision also describes a film-based approach for quantum dots in a 2007 patent application, describing the conversion of blue to white light in a flexible or rigid film. A quantum dot-enhanced backlight for cellphone keypads also is outlined, using blue or ultraviolet light to excite the dots to emit brighter light of different colors.

The patent filings also provided a window into Nanosys’s decision to shift its development focus to quantum dot-based film from its QuantumRail technology. Nanosys signed an agreement with LG Innotek in 2010 to create quantum dot-enhanced backlights using the QuantumRail glass capillary design, an approach it abandoned a year later in favor of film.

With QuantumRail, the glass capillary optical component contains red and green quantum dots that are to be inserted between the LEDs and the light guide panel of an LED-based LCD to improve color gamut. The organic materials that surrounded the quantum dots deteriorated under high operating temperatures and light flux, limiting the life of the dots when exposed to heat and light flux near LEDs, Nanosys said. QuantumRail approach also lacked control and accuracy when near LEDs and had reliability and optical issues tied to being glued in place, the company said. With issues tied to alignment and optical coupling of a primary light source, QuantumRail could cause light to be wasted as it reflects off the QuantumRail or escapes, Nanosys said. Quantum dot-based film eliminates “integration issues” and increases the “predictability” and control of the primary light, Nanosys said. The film-based approach reduces the amount of light that is wasted and “improves device efficiency,” the company said.