Abstract
Advances have been made in the development of carbon nanotube field emission displays. We fabricated a 25 inch diagonal, full color RGB, video display using standard screen printing techniques. The pixel pitch is compatible with an approximately 90 inch diagonal HDTV display and the fabrication processes are scalable to large area displays.
Introduction
The development of carbon nanotube field emission displays (CNT FED) is progressing. The target market for these displays is the large, 60 to 100 inch diagonal, television. For these displays to be cost competitive with existing technologies, inexpensive materials and processes must be used in their fabrication.
Several companies and research groups are pursuing CNT FEDs, although each is taking a different approach. Some companies are using photolithographic patterning techniques to make the gated emitter structure and then growing the CNT emitters directly on the glass using CVD techniques. For example, Motorola demonstrated a 4.6 inch diagonal, full-color display with pixel dimensions representative of a 42 inch diagonal 16:9 HDTV [1]. Using a similar approach, LETI demonstrated a 6 inch diagonal monochrome CNT FED in video mode with 320 x 240 pixels with a size of 350 ¼m. They achieved a luminous level of 800 Cd/m2 with a 50% aperture black matrix and pixel to pixel uniformity within 5% [2]. These direct CVD growth approaches will be difficult and expensive to scale to large area in high volume manufacturing since large sheets of glass will need to be heated very uniformly to high temperatures (600°C or higher).
Thus, there is no manufacturing advantage over LCD TVs. Other companies are dispensing CNT emitters using various printing techniques. Samsung SDI has developed several approaches. One recent approach uses standard lithography techniques to form the emitter structures that have both the emitter extraction gate and focus gate electrodes and incorporating an a-Si resistive layer in the structure to help control uniformity [3]. The unique Samsung approach includes printing the CNT emitter using photosensitive paste and then using backside illumination to expose the paste to form the CNT emitter patterns. Thus, the features are self-aligned and the structure is easier to manufacture. Mitsubishi Electric Corp., as part of an effort funded by the Japanese Government, has developed an approach in which the CNT emitter material is printed early in the fabrication process and then a SiO-based polymer is printed and patterned to form the gate dielectric [4]. Various activation processes have been developed to improve the emission performance of dispensed CNT films [5].
In previous efforts, Applied Nanotech, Inc. has demonstrated a 14 inch diagonal monochrome CNT FED [6] and a 14 inch diagonal color CNT FED. These display panels were made using inexpensive screen printing and frit sealing techniques. Here we present a 25 inch diagonal, full color CNT FED with a pixel pitch compatible with a 60 inch diagonal ATV. This is a direct scale - up of our 14 inch diagonal color display with a pixel pitch of 1.575mm and a color subpixel pitch of 0.525mm. This larger panel demonstrates the scalability of this technology using printing techniques and shows the potential of smaller capital investment in the manufacturing process in the future.
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