A Novel Cold Cathode Fluorescent Lamp with an Adiabatic Layer

A novel cold cathode fluorescent lamp (CCFL) with an adiabatic layer suitable for backlighting in PDAs (Personal Data Assistants) is described. The adiabatic layer (100-200 μm) is formed between a light tube and an outer tube and is filled with low-pressure gases. This raises the temperature of the light tube to the suitable value (50-70°C), which maximizes luminous efficacy even in low lamp wattage operation and at low ambient temperatures. The results of experiments and heat transfer analyses show that the optimum pressure in an adiabatic layer lies between 1Pa and 10Pa. At a pressure of less than 1Pa, the lamp temperature maintains a constant level because the conduction loss is lower than the radiation loss.