FIG. 1 shows a structure of a known discharge lamp, including a sealed vessel (such as a glass tube) 10, a fluorescent layer 11, noble gas 20 (such as argon or neon), mercury atoms 21 and a pair of electrodes 30. The electrodes 30 are disposed on two ends of the sealed vessel 10 and connected to a power source (not shown). When voltage applied between the two electrodes initiates a discharge process, electrons generated during the discharge process collide with mercury atoms 21 such that the mercury atoms 21 are excited to an excited state. Afterwards, ultraviolet light is emitted as the mercury atoms 21 move from the excited state back to the unexcited state. The ultraviolet light is then converted into visible light after passing through the fluorescent layer 11.
The fluorescent layer 11 is formed by mixing red fluorescent powder, green fluorescent powder, and blue fluorescent powder, and the percent ratio of three fluorescent powders can be adjusted to obtain the desired color temperature and chromaticity. However, each of the three fluorescent powders can affect the property of the fluorescent layer 11, which makes the process more complex and therefore increases the manufacturing cost. In addition, mercury may lead to significant environmental contamination.
Therefore, it is necessary to provide a discharge lamp which can reduce the production cost of the fluorescent powder, simplify the process of producing the mixed fluorescent powder, and comply with environmental protection trends.