Another app note from Micrel the MIC4826/7 Electroluminescent (EL) lamp drivers and designing with EL lamps (PDF!):
The design of an EL lamp circuit begins with the selection of
a lamp. A typical lamp will exhibit a capacitance on the order
of 2nF to 3.5nF per square inch. When a high voltage AC
signal is applied across the electrodes of an EL lamp, an
electric field is generated across the plates of the lamp. This
electric field excites the phosphor atoms to a higher energy
state. When the electric field is removed, the atoms fall back
to a lower energy state, emitting photons as visible light. The
wavelength of the emitted light is determined by the type of
phosphor used and the frequency of the excitation voltage.
Figure 1 shows a typical bridge configuration that is applied
to the EL electrodes to generate the AC signal. Typical AC
voltages applied to the EL lamp are 50V to 250 VPK-PK, with
a frequency of 50Hz to 1KHz.