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What is EL
Jul 03, 2017

Electroluminescent (Electro Luminscent) referred to as EL.

Photospheric material (Phospher Partides) particles of zinc sulfide, by adding the AC voltage generated by the poles generated by the AC electric field, the electrons in the light-emitting layer at high speed operation, start the light-emitting atoms, so that it is accelerated to get enough energy, electric field excited electrons Which is a kind of physical phenomenon caused by the emission of high-efficiency cold light, that is, the phenomenon of electro-luminescence, the electric luminescence is a kind of electric energy from light to light Can be the phenomenon, because in the course of their work will not produce heat, so commonly known as "cold light."

Principle of operation

Cold light is a conversion of electrical energy devices, cold light source general operating voltage and frequency, the adjusted operating voltage can be AC40V ~ AC220V, and the operating frequency from 50 Hz to 4000 Hz, increase the voltage will increase the cold light, if the increase in frequency Can increase the brightness, but at the same time will change the luminous color.

Its luminous characteristics do not produce shadows, not dizzy, uniform brightness and neon effect ... ... and so on; and with the environmental needs, such as: narrow space, complex modeling, temperature and power consumption restrictions, vibration of the environment ... ... Such as the case, EL make up for the traditional light source is impossible.

EL structure

EL in the sandwich structure above and below each have an electrode, where the electrode is ITO film, light from the ITO film surface, the lower electrode for the second electrode, also known as the back electrode, which is the main material of silver or carbon.

Luminescent materials (mainly zinc sulfide, generation formula: ZNS) When it will have different initiators, combined with a variety of substances, so produce different colors of light. (Currently commonly used luminous powder color: pure blue, pure green, blue and green, white)

EL technology involves a complex solid-state chemistry, materials science, vacuum plating (IONSPATTERING ion sputtering), in the current development, manufacturing process requires not only high-tech production and testing technology, but also because of the industry's special needs a lot of high Scientific and technical personnel and skilled workers.

The relation between EL luminous brightness and voltage is: L = Lo exp (-uo / u) where L = luminous intensity, u = excitation condition, structure of light emission and constant of light-emitting powder [1] - [3]

The luminous intensity is proportional to the frequency in the low frequency range. As the frequency increases, the luminous intensity exhibits a saturation state, but there is no significant relationship between the luminous duty cycle of the experimental surface. In other words, at the same frequency, the duty cycle of the waveform , Will not significantly change the luminous intensity.

The polarity of the voltage waveform has a very important effect on the luminous efficiency and lifetime of the EL. Since the electroluminescence of the inorganic electroluminescence in the zinc sulfide is accelerated by the high electric field and then the excitation effect is generated by the excitation and excitation. Pulse voltage as the driving voltage, will affect the service life, and the use of positive and negative pulse voltage as the driving voltage, is conducive to recovery after the collision, will not affect life.

EL leads the two electrodes through the insulation between the two electrodes to isolate the drive circuit when the performance of the capacitive load, the equivalent load of about 0.2-0.9nf / cm2 EL drive current is small, the size of the main area by the luminous material And the required brightness to determine, generally 0.14mA ~ 1mA / cm2, EL area is larger, the capacitive load is also quite increased, the current flow also increased, so its drive circuit with capacitive load capacity and Impact resistance should be quite improved.

EL brightness and its drive power characteristics are closely related to keep the brightness is not bright, must continue to change the polarity of the pulse voltage, that is, with AC to drive EL, when the EL between the two poles, the light layer was established electric field. Electrons in the direction of the electric field to accelerate the direction of the anti-electric field, when the electric field strength is strong enough, the number of electrons in the state of motion is enough, the speed is fast enough, through the collision, the luminous material atoms in the excited state and energy level jump, If the electric field is not changed, the number of electrons in the moving state is gradually reduced, which is not enough to activate the energy level transition of the atom. Then the brightness of the EL gradually decreases until it does not emit light. If the electric field is alternately changed, The electrons are always in the direction of high-speed movement with the change of the direction of the electric field, so that the energy level of the atom is not continuous. When the frequency of the electric field is fast enough, the height will keep steady and flicker-free. In practice, At a certain frequency, the luminance is proportional to the drive voltage, and the peak of the AC voltage that normally drives the EL is 30V to 250V

Brightness is not only affected by the voltage, but also with the frequency, but also can be fine for the landlord in a certain voltage and the frequency is proportional to the frequency, usually working frequency is cold 50-400Hz sometimes KHZ frequency, then the brightness can be connected to the saturation voltage When the brightness has no significant improvement. Wet and brightness, life is inversely proportional.

EL's life is measured from the half-life (half-brightness). It is defined as the period when the brightness of the display is reduced to half the initial brightness. Usually this time is 3000-12000Ph. It can be seen that the EL life is long, but the high voltage and high frequency are long and the brightness is saturated for a long time. This will accelerate its aging , Shorten its life. As the human eye to the brightness of the reaction into a non-linear, semi-bright and full-bright debate is not obvious, so EL can be lower than the full-bright work, and in the circuit to self-test circuit, through the corresponding increase in voltage to extend life, This can also be improved in the production process recipe to extend its life.

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