Electroluminescent film (abbreviated EL ) film, also called phosphor screen, the light -emitting film or capacitor film, a technical application of the electroluminescent electric energy conversion into light.
Electroluminescence is the property of certain materials or material combinations, to emit light upon application of an electric field. In the case of the electroluminescent foil, a semiconductor is excited in a particular capacitor configuration by an alternating electric field to emit light. The electroluminescent film is a Lambert radiator.
The basic structure of an electroluminescent sheet is similar to a plate capacitor: between two conductive layers (electrodes) is electrically insulated, the electroluminescent material. An electrode is translucent and is usually made with indium tin oxide coated plastic film. The second foil reflecting the light. The overall thickness is less than 1 mm. construction:
- Protective plastic film
- Transparent conductive film
- Insulating material with embedded fluorescent
- Metal foil
- Protective plastic film
Wherein said electroluminescent phosphor is usually to zinc sulphide, a II-VI compound semiconductor with the various metals such as manganese ( ZnS: Mn ) is doped, gold, silver, copper, or gallium. White light is usually generated by the superposition of colorful luminous pigments.
The electro luminescent and insulating layers can be applied by screen printing. There are also stretched, round shapes ( luminous tubes, EL wire, Eng. Electroluminescent wire ) made in which the alternating field between a central wire and mounted thereon layers is produced.
The phosphor degraded when it comes into contact with moisture. The surfaces are protected by welded plastic films which should not be damaged. In contrast, light tubes can be shortened, since only the cut surface is damaged.
The materials of an EL film are insulators at DC and not light. Operation of el-lamps and cables requires a sinusoidal AC voltage. Depending on the type, the operation voltage between 30 and 300 volts at a frequency between 50 Hz and 4 kHz. Brightness, to a limited extent also the color and the lifetime depends on the amplitude and frequency of the AC voltage. For example, the lifetime halved the frequency doubles. To maintain optimum operating conditions, manufacturers offer their films along with matched inverters.
The light emission occurs without heat generation, large-area, non-directional and low luminance. The current consumption is about 1 to 2 A / m. The field strength is 10 kV / cm, corresponding to approximately 100 V at a film thickness of 0.1 mm.
EL foils and cables shine in terms of area, but not very bright, the luminance decreases with time. The life of the operating time is specified, after it has fallen by half.
The applications are very versatile with the extraordinary properties.
- Security lighting ( Treppenstufenprofil )
- Self-luminous vehicle license plates
- Self-luminous dials,
- Display backlighting in liquid crystal displays ( LCDs ) and thin-film transistor ( TFT) displays
- Night lighting.
- In a crush-resistant, non-slip floor graphics laminate as
- As flat-field generator for receiving Flat Frames for astrophotography