18.5L:Late‐News Paper: The First Active‐Matrix CNT Field Emission Display

Abstract

The active-matrix driven diode-type field emission display (FED) was fabricated using carbon nanotubes (CNTs) as electron emission sources. The a-Si TFT and screen-printed CNT film were successfully integrated for the active-matrix cathode. We fabricated the first prototype AM-CNT FED panel as 3-inch in diagonal with 96x64 pixels. The driving voltage of AM-CNT FED was below 25 V and the operation was well stabilized by the control of driving TFT. IntroductionSince the first application of CNT as electron sources for FED [1], there were many attempts to make FED using CNT [2][3][4]. To construct reliable and low-voltage-driving triode structure for CNT-FED was one of the critical issues in these attempts. The distance between the emission gate electrode and CNT must be small enough to induce field emission at low voltage. In the case of CNT emitters, it is very difficult to make self-aligned emitter tips for the emission gate electrode. Therefore, the emission gate electrode should be electrically isolated for reduction of leakage currents which are originated from the asymmetric position of emitter tips. The electric field induced by the bias of the anode electrode should be shielded for the reduction of off-currents. These constraints require very complicated and expensive processes for the CNT-FED. So, for the application in large size display panel, another approach should be done.We suggest that the active-matrix driven diode-type CNT FED can be the good choice for CNT-FED.For the case of active-matrix driven display panel, the control device is integrated into each pixel. The driving voltage for the panel is the operation voltage of control device which is usually low enough to use general purpose driving IC for display panel.The off-currents are also suppressed by the off-characteristics of control device. Therefore, there is no need to use complicated triode structure for the lowering of operation voltage and reduction of leakage currents for CNT-FED.We adopted diode structure for the field emitter, which is very simple and is suitable for manufacturing large size panel. The low-driving voltage for the CNT-FED panel is achieved by the integration of a-Si TFT as a control device. The cathode electrode of diode-emitter is connected to the drain electrode of control-TFT. The emission current from the diode-emitter should be equal to the operation current of control-TFT. Therefore, the gate bias which control the current flow in TFT is enable to adjust the emission current from diode-emitter. There are so many CNT emitters in each pixel of CNT-FED. The turn-on voltage is depends on the length and surface condition of CNT. Up to now there is no known method to control the emission characteristics of each CNT. In general the variation of emission currents from CNT emitters is larger than that of on-currents in a-Si TFTs. So, the uniformity of the emission currents are greatly improved through the TFT-controlled emission currents.The reduction of power consumption is another advantage of the active-matrix drive...

Pen-writable nanocarbon arrays fabricated using liquid-crystalline materials for potential use in displays

“…Due to their high aspect ratios 2 and small tip radii, CNTs are able to emit electrons at low voltage, 3 making them an excellent candidate for field electron sources in flat-panel displays. 1,4,5,6 The high conductivity of CNTs make them a good choice for use in conjunction with polymers for transparent conducting films, which could be used as flexible display substrates. 7,8 CNTs must meet several criteria if they are to be widely adopted for use in the display industry.…”

“…9 Since field emission was first demonstrated in CNTs, 1 a number of prototype displays have been fabricated using them as a fieldemission source. [4][5][6] Currently, conducting films fabricated using nanotubes are available with surface resistivity on the order of 450 Ω/ᮀ with greater than 95% transmission at 550 nm. This is comparable to the performance of ITO in numerous commercial applications.…”