DC EL lamp

All of the above-mentioned EL lamps use AC power. Several techniques for making DC EL lamps are now known, which can be roughly divided into two categories: (1) vacuum-deposited (properly activated) continuous thin films of zinc sulfide, and (2) structures that allow DC current to pass through the phosphor layer.

Evaporated-deposited zinc sulfide films often have a brightness that exceeds that of conventional EL lamps when operated at low voltages ranging from a few volts to 80 volts. However, this lamp requires a process to form a starting current to achieve full light output, and due to structural difficulties, the life is much shorter than that of ordinary EL lamps, making it unworthy of reproduction.

A light-emitting device that can operate with DC and use ordinary phosphors and has both ceramic and organic structures has been manufactured. Generally, organic-structured devices must be treated with copper salts to produce a copper sulfide conductive layer around each phosphor particle, which requires the use of an appropriate medium to bond the phosphor to allow the DC current to pass smoothly. This is the same as the structure of the evaporated zinc sulfide film, which often requires the process of forming the starting current, and the coating is not stable and has a short life, but its brightness is much better than that of general electroluminescent devices.

These types of DC electroluminescent lamps are unlikely to occupy an important position in the market unless their stability and life can be improved. However, since it can operate at a relatively low voltage, it may be used in modern transistor electronic devices.