| 摘要 |
PROBLEM TO BE SOLVED: To improve light emitting efficiency by specifying the frequency of a second voltage superposed on a first voltage. SOLUTION: Voltage V1, V2, each produced by superposing a first voltage having a first frequency on a second voltage having a second frequency higher than the first frequency, are applied to electrodes 21, 22 of a discharge tube 20. The first voltage having the first frequency is applied to the discharge tube 20 so that discharge is caused by the voltage. Next, when the second voltage having the second frequency is superposed, electrons, ions, and plasma already formed and present in the discharge tube oscillate along with changes in the electric field. When the second frequency is chosen in the range of 2.4-20MHz, further a resonance phenomenon of electrons, ion and plasma is also generated. As a result, temperature of these particles rises and electron temperature approaches a value preferably for radiating visible light or ultraviolet rays, and light emitting efficiency is improved. |
