Relationship between field emission property and composition of carbon nanotube paste for large area cold cathode J.The authors have developed a spherical field-emission cathode based on carbon nanotube paste. The cathode was formed on a 2 mm stainless-steel ball with a silver paste sublayer which provide good adhesion between carbon nanotubes and the metal substrate. The emission current with a density of 300 mA/ cm 2 was obtained and the current showed good stability. The cathode was assembled into a luminescent lightbulb with 8 kV anode voltage. The luminous efficiency was 26.4 lm/ W on pulse mode.