National Tsing Hua University (Hsinchu, TW) reveals carbon nanotube (CNT) array elements and method for producing the arrays as well as an improved carbon nanotube field emission device in U.S. Patent 7,648,406. The field emission device electrodes may be formed by screen printing using a conductive paste.
Nyan-Hwa Tai, Chien-Chao Chiu and Tsung-Yen Tsai developed a method for producing a carbon nanotube array element. The steps include: providing a first substrate coated with a conductive paste layer; forming an array of thin film blocks of catalyst on a second substrate; forming each of the thin film blocks into islands of catalyst; forming carbon nanotube bundles on the islands of catalyst.
Each of the carbon nanotube bundles has a free end portion. The next step involves pressing the second substrate toward the first substrate such that the free end portions of the nanotubes insert into the conductive paste layer; solidifying the conductive paste layer; and removing the second substrate together with the islands of catalyst from the carbon nanotube bundles, thereby forming an open end for each of the carbon nanotubes.
Moreover, by producing the open end for the carbon nanotubes and by controlling the block size and the CNT length, the screening effect can be reduced and the edge effect can be enhanced, as a result, the field enhancement factor is increased significantly so as to improve the field emission property.
A carbon nanotube array element for a field emission cathode device is also disclosed. Carbon nanotube (CNT) has excellent electrical, mechanical, chemical, physical, and thermal properties because of inert and perfect graphene structure and high aspect ratios. In particular, CNT is applied to produce a field emission display device because of low turn-on and threshold voltage.
CNT grown by chemical vapor deposition (CVD) techniques is used as an electron emission source. After externally applying a voltage, electrons are emitted from CNT tips and hit an anode (e.g., indium tin oxide substrate having phosphor coating) to generate light. Under an applied voltage of 3 V/.mu.m, the current density is 1 mA/cm2, and the lifetime is up to ten thousands hours. Moreover, compared to other displays, the field emission display (FED) has advantages of high brightness, wide view angle, small thickness, and low energy consumption