EL cell is one of the transducers that transform electrical energy into optical energy. Its electrical equivalent circuit contains not only linear elements but also a nonlinear element. With this considered this paper proposes a comparatively simple equivalent circuit which consists of resistance, nonlinear resistance and capacitance in series.

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ZnS: CuAl powder molded in insulating substance was subjected to high frequency electric field from 120 cycles to 50 megacycles, whereby the E. L. brightness was measured aguinst frequency. The experimental results within this frequency range follow the relation B=exp (-b/i./V), where B and V are respectively the brightness and applied voltage; b is a constant dependent on the frequency, which may be expressed as b=b₀fⁿ.
The wave-forms of brightness under excitation of sinusoidal voltage were observed in the frequency range from 30 cycles to 200 kilocycles. Two peaks in the brightness wave-form where recognized. The ratio of the first peak to the second increases proportionally with the n'th power of frevqency.

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Electroluminescence and electrical properties of the vacuum-deposited thin films of ZnS (Cu, Mn, Cl) are studied. Electrical conduction of the films is affected by surrounding atmosphere, especially humidity and temperature. Negative resistant characteristics are observed at above 50% of humidity and below room temperature, but it is not observed in vacuum, rare gas, oxygen anddry air. ELbrightness of thinner films prepared by one step process is large at DC excitationunder some conditions, and it decreases with frequency of AC excitation. But EL-brightness of comparatively thicker films is scarcely affected by frequency, or it may increase with frequency. EL-brightness of films prepared by two step process (EL films are heated after deposition process) increaseswith frequency of AC excitation. For better light output and efficiency it is effective to utilize the DC excited thin films by “one step process”.

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