Merck KGaA, which is a Germany-based chemical and pharmaceutical company and also well known as a leading liquid crystal maker in the field of displays, is renovating displays with its own quantum dot technology.
A quantum dot is a minute compound semiconductor particle measuring several nanometers to several tens of nanometers. It has a wavelength conversion function. When it receives light, it emits light of a different color. When quantum dots are used for the backlight unit of a liquid crystal display (LCD), they make the color of the display vivid and reduce its power consumption.
Conventional quantum dots look like particles, but the nanocrystal being developed by Merck looks like a rod. Therefore, the company calls it "quantum rod." We interviewed Stephan Dertinger, Head of Technology Scouting & Feasibility Asia, Emerging Technology, Performance Materials Advanced Technologies, Merck, on the characteristics of and development strategies for the technology. (Interviewer: Naoki Tanaka, Nikkei Electronics)
Q: What is the difference between quantum rods and conventional quantum dots? How are quantum rods superior to quantum dots?
Dertinger: When applied to LCDs, quantum rods are superior in brightness. Though it depends on the usage of an LCD, with quantum rods, it becomes possible to achieve three times higher brightness with the same display performance. When this capability is used to reduce power consumption, the battery life of a mobile device is much improved. Furthermore, quantum rods might enable to manufacture LCDs at lower costs.
In terms of color reproducibility, we have already achieved a performance equivalent to that of an LCD using conventional quantum dots. Quantum rods can realize a 100% color gamut on NTSC standards.
Q: How do quantum rods realize a high brightness?
Dertinger: When light is applied to quantum rods, they emit light of a different color, and it is polarized light. They emit polarized light because their nanocrystal has a rod-like shape and, thus, directivity. As a result, they can be used for LCDs as they are.
Currently, a polarizing plate is used for LCDs to generate polarized light. But, because of this, half of backlight is lost. Our technology can eliminate this loss.
We are developing the "ABEF," a film made by dispersing quantum rods in resin, which is placed on top of the light-guiding plate of a backlight unit. The light transmittance of the ABEF is currently 80%. We believe that, by optimizing the designs of LCD panels in accordance with the ABEF, the light transmittances of displays will improve in the future.
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