단일벽 탄소나노튜브 투명 필름 히터의 열적 성능 평가

다국어 초록 (Multilingual Abstract)

Thin indium tin oxide (ITO) films are used as transparent heaters in various applications, such as outdoor panel displays, avionic displays, liquid-crystal display (LCD) panels for use in harsh environments, periscopes, and vehicle window defrosters. However, ITO film heaters have some limitations, such as a slow thermal response and complex fabrication processes. Because carbon nanotube (CNT) films have high thermal conductivity and can be produced by using various common fabrication methods, they can be promising alternative to ITO films in the field of transparent heaters. Therefore, we fabricated transparent film heaters using single-walled carbon nanotubes (SWCNTs) and investigated their heating performance.
Among the many fabrication methods for the transparent SWCNTs film, we chose the vacuum filtration method due to the easy controllability of transparency and excellent uniformity of networked SWCNTs. As a result, we made SWCNTs films with transparency of 97~65 % according to the sheet resistance of 3500~230 Ω/sq. We tested the film heaters as shown in Figure 1 and verified the heating capability of the SWCNTs films. Figure 2 shows the temperature change when a SWCNTs film with transparency of 79 % and sheet resistance of 580Ω/sq is heated. The steady state temperature was reached within 60 seconds showing a uniform temperature distribution over all area. For eight different SWCNTs films on glass substrates (2.5㎝×2.5㎝×0.3㎝), we experimentally obtained optical transmittance and steady state temperature according to the sheet resistance of the SWCNTs film for the applied voltage of 60V as shown in Figure 3. Figure 4 shows an example of the transparent heater application. Since dew or frost on the vehicle window disturbs riders' visibility, it is very important to remove dew or frost as soon as possible for safety. We checked the possibility of the transparent SWCNTs heater as a defroster for vehicles. We prepared the SWCNTs film with sheet resistance of 1190Ω/sq and optical transparency of 91.3%. The SWCNTs film was inserted in a refrigerator for 1 hour. Frost was grown overall surface of SWCNTs film. Consequently, the transparency of the film was significantly reduced and the words in the background was not recognized as shown in Figure 4(a). After 1 minute Joule heating of the transparent heater, the frost on the surface was completely removed and the background words were clearly visible as shown in Figure 4(b). For this case, used power was 2.11 Watts.
In summary, we verified the heating capability of the transparent film heater using SWCNTs. Therefore, this film would be a good candidate for the film heater in many applications requiring both transparency and heating function.