Electroluminescence
FAQ
- Click on question to scroll to the answer
below...
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What
is the definition of EL?
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What
powers an EL lamp?
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What
are phosphors?
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What
are the advantages of EL lamps?
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How
much power does EL consume?
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What
is the "actual life" of an EL lamp in use?
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How
many and what EL colors are available?
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Can
multiple colors be printed on one EL lamp?
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Are
the EL lamps that you produce patented?
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Do
you plan on providing DC-AC inverters with the EL
lamps we would purchase?
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What
is the cost of tooling and design for the EL lamp?
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What
testing results can be provided on the EL lamp?
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How
bright is EL and what colors are the brightest?
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What
is the illumination intensity (highest and lowest
range)? Can it be controlled?
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How
flexible is the EL lamp? How far can it be bent,
rolled or crushed under weight and continue to
function?
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How
are EL lamps able to flash?
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How
is the flashing frequency determined?
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Can
the EL lamp have multiple segments and can those
segments be different colors?
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What
is the maximum size EL lamp that can be produced?
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What
is the smallest EL lamp that can be produced?
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Minimum
quantity EL orders?
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How
are the EL lamps tested before shipment to ensure
they meet my criteria?
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Can
an EL lamp be applied to any material?
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What
specifications do I need to provide you in order to
receive an accurate quotation for the EL lamp?
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What
specifications do I need to provide you in order to
receive an accurate quotation for the inverter?
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What
is the resistance to moisture?
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What
is the shelf-life of an EL lamp?
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Is
the location of the power lead important?
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Can
direct power be used with EL?
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What
is the possibility of electric shock?
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What
else should I consider when specifying an EL lamp?
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What
does the sandwiched construction consist of?
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What
is the failure mode?
The EL
lamp is essentially a capacitor structure with phosphor
dielectric sandwiched between the electrodes, one of
which is transparent to allow light to escape.
Application of a voltage through an inverter across the
electrodes generates a changing electric field within
the phosphor, which causes the phosphor to emit light.
EL panels
require alternating current (AC) power. If the power
source is direct current (DC) like a battery, an
inverter is required. An inverter is a device that
converts DC to AC by stepping-up the DC voltage (typical
3 to 24 Vdc) and introducing an oscillation to achieve a
desired AC output (typical 60 to 120 Vac @ 250 Hz to 2
Khz). There are two general types: Resonating
Transformer and Integrated Circuit (sometimes called
"chip" inverters). In most designs the
inverter is unregulated and uses the EL panel as part of
a tuned electrical circuit. An EL panel's electrical
characteristics change as the panel ages. Properly
matched inverters "react" to these changes and
can as much as double the time to 50% of initial
brightness. However, a poorly matched inverter has
little positive affect on life and can introduce Radio
Frequency Interference (RFI) and Electromagnetic
Compatibility (EMC) conflicts with other components or
devices.
Phosphors
are powders made of materials such as zinc sulfide,
doped with either copper or manganese to achieve the
emission colors. (Blue-Green, Yellow-Green, etc., White
is achieved either by phosphor blends or chemically
shifting the emitted color.) The color can be defined
during the manufacture of the phosphor, or can be
achieved by blending phosphors of different colors to
achieve composite color.
EL
lamps/panels are impervious to shock and vibration, no
catastrophic lamp failure, negligible heat emission, EMC
(Electro-Magnetic Interference) and no FRI (Radio
Frequency Interference), a uniform surface
illumination of complex or flat shapes, thin flexible
and lightweight, low power consumption, very low heat
generation, and impact resistance, a 3000 hour time to
half life brightness at 100V and 400Hz can be used as a
guideline but is dependant upon the type of and quality
of the lamp construction, the environmental conditions
and the voltage/frequency. (We are able to deposit the
light emitting particles in any shape, thereby, we are
able to produce any design, font or lettering.)
EL
typically consumes less than 0.25mA-amp at 115V AC per
one square centimeter.
There are
two types of "life": Time to 50% of Initial
Brightness and Useful Life... Time to 50% of initial
brightness is used mostly as a specification to ensure a
specific decay curve over a specific amount of time. It
is also useful for comparison of EL panels from various
suppliers. Many factors affect "Time to 50% of
Initial Brightness" including the type of phosphor,
initial input power (i.e. peak voltage and frequency),
type of input power (power supply or compensating
inverter) and environmental conditions.
For reference time to 50% brightness for EL panels in
mobile phones is ~4,000 hours. That same panel on a
fixed output power supply would hit 50% brightness in
~2,000 hours.
- In the case of automotive applications 4,250 hours to
50% brightness is considered the industry standard and
is based on the formula: 125,000 miles / avg. speed of
25mph = 5,000 vehicle hours x 85% on-time = 4,250 hours.
- The "Useful Life" of an EL panel is
determined by establishing the minimum brightness level
that still provides functional illumination for a
specific application. The duty-cycle of on time is also
an important factor when discussing "Useful
Life" as the lamp only ages when it is powered.
- A good example is the EL Nightlight, which is
typically powered 24 hours a day. Its 50% brightness is
reached in approximately 8,000 hours and 25% of initial
brightness in ~24,000 hours. However, the nightlight can
remain "useful" for upwards of 5 years or
43,800 hours. If it were switched off for 12 hours per
day, then the "Useful Life" would be 10 years
or 87,600 hours.
White,
Blue, Blue-Green, Green and Orange are the available
standard phosphor EL lamp colors. Other colors are
possible by blending phosphor, adding dyes to the
dielectric and phosphor layers or by using laminated or
printed filters on the face of the panel.
We
produce multiple colors by selective printing of dyed
dielectric layers or top surface filters.
No, this
is readily available technology, originally discovered
in 1935 and perfected through the years.
When our
customers require engineering support in order to select
the appropriate inverter or driver circuits that match
the electrical properties of our lamps, we will of
course provide this assistance through our engineering
team. We would provide a warranty on any lamp and power
unit if our company provided the entire system. A
warranty would not apply if we did not provide the power
units or if we were unable to test and approve the
customer supplied power unit as being compatible.
Tooling
costs are dependant upon the unique specifications of
each job and are, therefore, difficult to specify in
this context. Some of the components for tooling costs
include the lamps complexity and size. Before actual
production of the lamp can be accomplished, detailed
engineering specifications must be determined, and
screens must be designed and produced to print each
layer of the EL lamp. We have a variety of
standard sizes backlights panels available, if one of
this sizes needed there would be no tooling cost. For
smaller panels 150sq cm or smaller the tooling cost
would probably be about USD120 one time fee for a custom
animated design/shape/or size. The cost will increase as
the size of the panel increase. Once we know the dimensions/shape/design/lighted
area/animation sequence (if any) we can quote the accurate
tooling cost.
Bend
tests - We recommend no bends tighter than 3 times
the material thickness (.5 millimeter or .0196 inch
minimum).
Crush tests - Unless something sharp is dropped on
the lamp, it will survive, although terminations may get
damaged breaking the bus-bar or converter.
Extended life tests - Life testing needs to be
carried out at the customer's facility.
Extreme temperature tests - This is only required
for the automotive and telephone industries.
Humidity tests - Since each client has differing
requirements, we would suggest a resource or in-house
customer testing.
UV exposure - We recommend add protective UV
layers if the lamp will be exposed to direct sunlight on
a constant basis, for example outdoor sign applications.
Weathering tests - These tests must be performed
at the customer level.
Blue-green
lights are the brightest and generate 15-20 foot
lamberts. (A lambert allows you to see the light at
160-degree angle.) With this amount of light output,
even small lamps can be easily seen for miles at night
(subject to no obstacles blocking the line of sight of
course). EL is especially good for areas that are
obscured by smoke, fog, dust and hazy conditions.
Yellow-green lamps can be made equally bright at higher
frequencies but the lamp life is reduced.
Voltage
increases light output and frequency changes the color
or chromacity, however, for every gain there is a
sacrifice, so making it brighter would mean losing some
life. Flashing and fading can double or even triple the
life. With a lower input, the lifespan is increased.
Higher voltage and frequencies, as well as elevated
temperatures during operation will degrade efficiency of
the lamps. To improve the life of the lamp, operation or
output at lower temperatures and voltage are encouraged.
EL can be
rolled, bent and crushed to degree not found in other
lamp and will normally continue to function, of course
sharp objects must be avoided. One of the unique
features of EL is its flexibility. The substrate is a
polyester film coated with an ITO transparent conductor
and several layers of material, which allow for a much
higher bend factor.
Flashing
is achieved though an inverter circuit.
Virtually
any "on time off time" can be achieved and is
measured by a cycle (number of seconds or parts of a
second the lamp is switched on and off is the cycle
number).
Yes, it
is possible to print multi-segment lamps up to 64
circuits, or we can matrix them together and address
X-Y. (Matrix addressing is where squares are printed in
bits like a chocolate block and address the sections to
achieve selective illumination.)
Our
maximum dimension EL lamp is 180x80 cm. For backlight up
to 10,000 sq cm, for animated lamp up to 14,000 sq cm.
In
theory, 0.3mm or .0118 inch, but practically .5 inch.
We can
supply samples from our stock for initial evaluation, we
try to keep common sizes in stock for customer testing.
Custom lamp orders we ask please try to order at min
USD700 value of el lamp. For our small line of ready
made products please refer to our most recent catalogue
for min order of any item.
Outside
of our normal Quality Control procedures, the details
are optimized and checked in the design and production
stage as well as a final check before shipment. We check
the following items: light output, connections,
capacitance value, current consumption, dielectric -
this is done as a batch test from the run.
Yes, such
as paper, film, foil, plastic, metal, rubber, glass,
leather and fabrics. This is dependant upon the
environmental conditions. Please consult with us for
more information that is specific to your application.
The
length and wide dimensions, lighted area dimensions,
shape, colors. Typically it is enough when supply us
with the length and wide dimensions and color and shape
for backlight lamp, or if for animated image lamp the
length and wide dimensions and the image or lighted
area, and sometimes the animation sequence but often our
less experienced customers will ask for our recommendation
about the animation. Some applications may require
additional UV or moisture resistant layers, please
contact us with your individual requirements.
We can recommend
based on your panel requirements and use, we need to
know if will be for 12v (for example automotive use) or
will be AC powered (for example EL sign), or if will
need battery operated.
Screen-printable
UV ink is used to encapsulate the phosphors to an
electrical insulation and provide extra protection
against humid environments. Constant exposure to
moisture will adversely impact the illumination of EL.
All polymer are semi-porous and will allow certain
amounts of ingress, however, further protection can be
afforded by laminating with PVC, polycarbonate, etc.,
depending on the application. Please contact us for
assistance.
While it
is commercially prudent to set a time limit of 2 to 3
years, the fact is that storage life is in excess of 10
years if stored in a controlled environment such as 68°
F. 50% RH.
We have
tested the power lead to the inverter/lamp for up to 6
meters or 19.5 feet, however, longer distances are not a
problem as long as voltage drops are taken into
calculations.
EL lamps
require alternating current with an over threshold of
400Hz.
With a
proper termination, there is no risk of electrical
shock. One must be cautious when handling the EL lamp
when the power is on as not to touch the electrical
connection.
You need
to consider that with time the light will gradually
decay as the phosphorescence efficiency declines. The
presence of moisture accelerates this decline. The
phosphors that we will be using are microencapsulated to
hinder the penetration of moisture thus prolonging the
useful life of the lamp. Additionally, the polymer
binders in our EL pastes have been selected to provide a
moisture barrier, which further protects against
moisture related aging. This feature also prevents
moisture from degrading the capacitance of the lamp,
thus providing higher brightness. Higher voltages and
frequencies, as well as elevated temperatures during
operation will degrade the efficiency and the life of
the lamps. To improve the lifetime of the lamp,
operation at lower temperatures, voltages and
frequencies is encouraged. Typically, 80-120V AC and
400Hz are utilized. These conditions result in the best
useful lifetime.
The EL
lamp consists of a sandwich construction containing an
appropriate substrate (polyester or polycarbonate), a
rear electrode, an insulating layer, the phosphor layer,
a transparent or translucent front electrode and a
protective layer. The lamp may be terminated by a silver
conductor and crimped connectors (or other means) to
allow connection to the power source. Special care must
be taken in providing a connection with good integrity..
During
failure the EL lamp will stop lighting. If the lamp was
overpowered, smoke is possible. The life of the lamp
will gradually decrease and, as the phosphor is
exhausted, less of the lamp will illuminate, until
eventually there will be no illumination. A failure and
reliability test analysis would need to be run on each
specific application.
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