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Flat panels go nanotech: Taiwan’s ITRI pioneers CNT-FED, part three
Chris Hall, DigiTimes.com, Taipei [Tuesday 25 January 2005]

TFT LCD looks firmly entrenched as the dominant flat-panel technology, but in fact the displays industry is keen to find a technology that delivers better performance – and, crucially, at lower cost. Alternative technologies exist, but often suffer from their own well known drawbacks. In the case of OLED technology, for example, there is the infamously short lifetime of the display.

One promising technology is the carbon-nanotube field-emission display (CNT-FED). In Taiwan, key development work on CNT-FEDs is ongoing at the Electronics Research and Service Organization of the Industrial Technology Research Institute (ERSO/ITRI). Recently, following ITRI’s announcement of the development of a 20-inch CNT backlight unit (CNT-BLU), DigiTimes.com had the opportunity to talk with Dr. CC Lee, deputy director of flat-panel development at ERSO/ITRI.

This is Part III of a three-part interview. Part I appeared on January 21, and Part II appeared on January 24.

Q: Are there any other critical stages in the development of the technology, as well as vacuum sealing?

A: In addition to the vacuum sealing process, we have also studied two critical points, one is the phosphor efficiency for backlight applications. For backlight applications we need to increase the phosphor, and then we can reduce the power consumption of the BLU. However, there is no commercialized production of white phosphor for the backlight, so we have cooperated with UCL and MRL in ITRI, and also established cooperation with institutes and companies elsewhere – including in Russia and mainland China – in order to supply the high-efficiency white phosphor.

For the BLU, white-phosphor efficiency is the critical point, but for display applications there is no problem with obtaining color phosphor because efficient color (RGB) phosphors for the display are available. So we don’t worry about the display applications, but we do worry about the BLU and obtaining high-efficiency white phosphor because it is not standard. We have put a lot of effort and study into obtaining and improving the performance of high-efficiency white phosphor.

In addition, we have also considered the process integration of the cathode emitter device because its uniformity is fully dependent on the uniformity of the cathode. If we can control the process and material of the cathode structure, and we also control the emitting site of the CNT emitter by means of a surface-treatment process, then we can get a uniform cathode structure.

So vacuum sealing is one critical point for mass production, but the phosphor, the materials issue and the uniformity and controllability of the cathode, are also critical issues for performance.

Q: According to a report published last August, the ITRI CNT-FED project has developed an inductively-coupled plasma chemical vapor deposition (ICP-CVD) technique for the production of CNT-FEDs. What is the current status of this technology? Is it still in development? What are the key characteristics of this process, and does it have any advantages over the use of screen-printing techniques?

A: There are more than 10 organizations in ITRI. One internal organization that specializes in the development of manufacturing equipment has developed a new ICP-CVD process, a new method for growing the CNTs directly on the cathode. If this process is developed successfully, it would mean we do not need to use printing technology. This is a different process integration strategy, but it is still in development. The possible advantage of this CVD approach is that it should allow us to control uniformity more easily than with printing technology.

Q: I understand metal catalysis is a key development in this process.

A: For CVD technology, we need to apply a coating of catalyst prior to the CVD process. The catalyst in this case is nickel, in nano-sized particles. These particles enable uniform coating of the cathode with CNTs.

Q; What about the carbon nanotubes (CNTs) themselves? What is the availability? What is the cost?

A: Two years ago, the CNTs were expensive, but now the cost has come down to around US$10 per gram. Some companies say they will reduce the cost of a one gram to one (US) dollar, for the next three years. But generally, you can say that if the quantity of the CNT-FEDs in mass production increases, then you can expect the material cost to be reduced. Even though the CNTs are currently priced a little high, you don’t need to worry because a single panel uses less than a gram of CNTs.

Q: And the size of that panel could be what?

A: Up to 40 inches. You don’t need to put too much CNT on the cathode.

Nevertheless, cost remains an issue for the cathode. There are three materials used in the cathode, including the silver used for the electrodes. In addition to silver and the CNTs, there is also the glass insulator, and it is the high cost of the glass that remains an issue. The cost of the glass remains high, currently, because there is little demand for 2.8mm glass.

There are other factors in the high cost of the glass. The glass for CNT-FED is from a single supplier, Asahi, and the glass is only of one type, PD200, which has been qualified by the panel makers. For other makers, such as Corning, the cost of investment in this type of high-strength glass remains prohibitive.

Q: Do you produce the CNTs at ITRI?

A: We do produce the CNTs at ITRI, but we are also cooperating with some materials companies in Taiwan for production of the CNTs because we want to help build the materials channel in Taiwan. So we have a cooperative program with the materials suppliers, right now, in Taiwan.

Q: I’ve heard that other companies and organizations are involved in the CNT-FED project. Can you give any details?

A: We have a cooperative relationship with both Tsinghua University and National Taiwan University. Tsinghua University takes care of some fundamental research in the formation and growth of carbon nanotubes. National Taiwan University takes care of some research in related phosphors.

Q: What about Teco and Delta Optoelectronics? Some reports have suggested they have some involvement in this project.

A: We have a public relationship with Teco. We are cooperating with them to evaluate the possibilities for the commercialization of CNT-FED technology. And within ITRI, we also cooperate with the MRL (Materials Research Laboratory). MRL also cooperates with Tatung Co. in the development of materials for CNT-FED. A professor from Tatung Institute is also a participant in the CNT-FED program.

Delta transferred some technology from ERSO and studied CNT-FED technology when the company began operations. They studied the technology for two to three years and then decided to focus on PLED business. They have the core technology, so if at some point in the future they wanted to return to CNT-FEDs, they could do that.

Q: Has ITRI now developed its own IP in CNT-FED technology?

A: Currently, worldwide, the IP we have developed at ITRI for the design and production of CNT-FEDs competes directly with that of South Korea, Japan and the US. Normally at ITRI we are a little behind the leading institutes and companies, but in this case, CNT-FED development, we have developed simultaneously with other organizations and countries, at the same tempo. We are confident that we have IP that can protect our own technology development and interests in this area. If any company in Taiwan wants to develop and mass produce CNT-FEDs, we are confident that they would not have to worry about IP issues as they have had to do before, in the cases of PDP and TFT-LCD production, for example.

http://www.digitimes.com/news/a20050125PR203.html