The conventilonal fluorescent lamp includes a pair of metal electrodes. In the lamp fabrication process, after evacuation, the lamp is filled with Ne-Ar gas. When alternating current of high voltage is applied to both ends of the lamp, the primary electrons are accelerated by the electrical field, thus ionizing the gas. When such ionization continues, spark plasma, in which cations and negative electrons coexist, is formed. When the electrons in the plasma collide with neutral mercury atoms, the mercury atoms are excited. As such, the electrons or cation, colliding with metal electrode, create sputtering at the electrodes. The metal electrode component, scattered through sputtering, is bound to mercury, thus forming a compound. When this compound is deposited around the electrodes, blackening occurs, which results in a decreased lifetime. In order to solve the problem, CPFL includes ceramic-glass composite electrodes having high sputtering resistance such as glass frit.
CPFL with ceramic electrode using ECP has a dielectric constant much higher than glass having a dielectric constant of about 10, and has high secondary electron emission. Furthermore, polarization thereof under the same electric field is at least 2 times that of glass. Thus, under condition of the same electrode area and the same dielectric area, many more electrons and ions may be moved in the glass tube, thereby greatly increasing the brightness of the lamp. Also, the temperature stability dielectric constant is superior at temperature of -30℃ and above. Thus, when the lamp is driven, brightness is maintained uniform even though the temperature is increased by the impulse of ion and electrons colliding with the electrodes. That is, there is no brightness variation even in response to changes in the external environment. As a result, CPFL can save energy with high brightness and efficiency.
Disadvantages of LED
  • 1. Price LEDs are currently more expensive, price per lumen, on a startup cost basis, than more conventional lighting technologies. The additional expense partially stems from the relatively low lumen output and the drive circuitry and power supplies needed.
  • 2. Color Quality White LEDs currently offer poor color rendering and a high color temperature. As improvements are made to the technology in the lab, however, we can expect these problems to be corrected.
  • 3. Product Standardization There is currently no standardization for this technology, raising questions about maintainability. Will the manufacturer offer matching spare parts when systems begin to fail or will entire systems need to be replaced?
  • 4. Safety There is increasing concern that blue LEDs and white LEDs are now capable of exceeding safe limits of the so-called blue-light hazard as defined in eye safety specifications such as ANSI/IESNA RP-27.1-05: Recommended Practice for Photo biological Safety for Lamp and Lamp Systems.