Assembly of bulb as encapsulation method for electroluminescent devices

Abstract

A glass flask obtained of pickled food was developed as bulb with intern vacuum to tests of encapsulation method for electroluminescent devices. Two metal valves to vacuum or insert inert gas, one pressure gauge (with high or low pressures) and one printed circuit board with copper strips for electrical connections were adapted to the glass flask lid and sealed with epoxy. In the first investigation, intern vacuum was carried out and the possible variation of intern pressure was observed by elapsed time (for seven days). In the second investigation, four incandescent lamps (12 V and 10 W) were used without outer bulb to obtain the tungsten filaments that were polarized under vacuum atmosphere at different situations. After seven days, only an insignificant increase of intern pressure was observed. The tungsten filaments were polarized at least 40 times inside the bulb with intern pressure at 101325 Pa (or 76 cm.Hg), while outside the bulb (at room pressure) only two polarizations with significant degradation were obtained. A layer of tungsten oxide (WO 2) with greenish yellow color was formed on the surface of the tungsten filament which was obtained by microscopies and confirmed by EDXS measurement.