Frequently Asked Questions
Continuing innovation with new materials and techniques has kept us at the forefront of new technologies. To keep our customers informed of the unique features and advantages of our products, we put this section together to provide answers to the questions most frequently asked. If you don't find the information you need here, or for help with your design, please call one of our sales engineers. A complete list can be found in the contact us section of our site.
How can I change the brightness of an EL lamp?
What are the unique features of Technomark EL?
Will using EL in my application cause interference?
How do I describe and specify colors?
What colors are available?
Will EL work in my application?
How do I power a Technomark EL lamp?
How long will a battery last?
What shapes and sizes can I use?
What properties of an EL lamp influence the overall cost?
- An increase in applied voltage increases the brightness.
- An increase in the frequency increases brightness.
- A typical curve showing the change of brightness with voltage is indicated in the Tech Specs section of our site.
- For small changes in voltage and frequency, the dependence of brightness on voltage or on frequency is essentially linear.
Thin: Standard Technomark EL products are typically between 0.008" and 0.010". EL lamps can be introduced into existing hardware with minimum changes to the packaging or mechanical layout. No special mounting hardware is required.
Flexible: Technomark EL lamps are generally prepared on flexible polyester substrates, allowing them to be used in applications (such as safety garments) or assemblies where bending is required.
Rugged: The all-polymer design with Technomark's PolyWeld technique produces a tough lamp, which will survive heavy-duty use. There is high resistance to chemical attack, no tendency to delaminate, even with thermal cycling.
Uniform: EL light is emitted uniformly over the entire lit area. As a result, no need exists for light pipes, diffusers, reflectors or multiple sources to provide flat, uniform illumination over a wide area.
Cool: In an EL display, the light is generated by a purely solid state process, so no heat is generated. This means no energy is wasted in heat, no thermal stress is produced, and no heat has to be dissipated and removed from the assembly.
Versatile: Technomark lamps are manufactured using printing techniques. As a result, anything that can be rendered in two dimensions can be illuminated. Technomark also offers a unique connection to the graphic arts industries through its heritage in screen-printed graphics. The result is a line of display products, which look equally good lit or unlit.
Protection against electrical interference should be a reasonable concern when any features are added to an application which use AC power. However, a well-designed EL display should not cause problems.
Many people who remember using EL 20 years ago recall the need for large, inefficient, and noisy inverters as well as high impedance lamps. Modern technology has made the use of EL much easier and has reduced the concerns about interference significantly.
If interference does arise, it is likely to come from one of three areas: overdriving the lamp, feedback of the inverter circuit switching noise onto the DC supply, pick up on very high impedance lines which are run too close to the lamp. Good design practices will eliminate all of these areas of potential concern.
Technomark EL is used successfully in many applications, which might be viewed as sensitive to interference, including GPS Systems, CB Radios, Broadcast Band Radio, Thermometers and Thermostats, Communications Systems, Diagnostic Equipment, and Test Instrumentation.
For further information ask your Technomark Sales Engineer for the appropriate Applications Notes.
Other systems can be used for specification but with caution.
Color temperature is not an appropriate scheme for describing EL colors because the physical process at work is not thermal so the emission spectrum is unlike that underlying the color temperature scheme.
PMS values can be used as an approximation, but can be misleading. Even for objects viewed in reflected light, PMS values depend on the lighting and the substrates used. In the case of EL, the self-luminous nature of the object severely distorts the perception of the PMS equivalent colors.
Often, the provision of a sample by the customer is most helpful.
In all cases, Technomark adopts and maintains internal specifications and monitors these during manufacture and test so that the customer can rely on receiving the same color of product time after time. Even if a customer specified color by example, the example will be measured to derive the quantified units used in maintaining performance.
In general, a simple specification of the color family will suffice; Blue, or Green, for example. These can usually be chosen by reference to sample lamps.
Customers should recall that the brightness of a lamp can alter color perception and that any change in the frequency of the AC used will also modify the color. Colors (as with any property of EL lamps) should always be specified with the operating point (voltage and frequency).
The basic EL phosphors come in Green, Blue-Green, Blue, and Amber. Each is a relatively pure color with emission over only a restricted range of wavelengths. (See spectra under Technical) Technomark also offers a number of formulations to produce "white" light. These are best optimized for individual applications (see Sales for information).
Technomark has a unique (patented) approach to making lamps with multiple colors on a single substrate. These permit either complicated self-illuminated graphics to be made, or areas of lamp to be designated for functional distinction.
Colors can be changed or optimized by the inclusion of a filter in the construction. This can be a simple (optimized) design such as the Technomark NVIS-A design, or can be a more complicate overlay, permitting a sign to be made which looks good both with the backlight on and off.
Examples of successful uses include:
- Pagers, mobile phones, GPS units
- After market automotive accessories
- Point of purchase displays
- Costume jewelry and novelties
- Switch and control panels
Many applications have a source of AC power available on board, in which case that power can be applied directly to the lamp.
Power derived from batteries is usually direct current (DC) power. In this case a circuit must be used to change the power for the lamp from DC to AC. Such a circuit is generally called an inverter circuit.
Inverters are available often either made from discrete components or in packed modular form. In addition, the heart of an inverter circuit can be found nowadays in the form of an IC, such as the Technomark MM803S.
Power use for an EL lamp is very low and is generally limited by the efficiency of the inverter circuit. Thus optimizing efficiency for the lamp system often amounts to optimizing the inverter.
The current draw of the inverter is a property of the individual circuit. Since the lamp itself uses very little power (typically 15 mw per square inch) the current going to the lamp is small. The current drawn (at low voltage) from the battery however will depend on the losses in the inverter circuit. With modern designs, this can be kept well below 50ma at 3VDC for reasonable sized LCD backlights.
The impact on battery life of any circuit which draws current will depend on the frequency with which that circuit is used. Since most EL applications (especially as backlights) have intermittent use, the impact on battery life is much less than if they were used 100% of the time.
Consider for example, the backlight in a mobile phone. It goes on for 10 seconds whenever the phone is used. Suppose that phone makes or receives 120 calls per day. The lamp is on for 1200 seconds, or 1/3 hour. If the inverter circuit draws 20ma, then the total impact on the battery is to require 6.6mah. A power pack equivalent to 2 x AA cells would thus last hundreds of hours.
The development of a use model is very important for understanding the aging properties of the entire EL system.
The total area of the lamp structure will influence the quantity of substrate used. Avoid log tails, large internal unlit areas, and wasted borders in order to cut down on the total area of substrate used.
The total lit area influences the amount of phosphor used. Selective deposition of light , available through the Technomark printing process permits the use of phosphor to be optimized and thus the cost for phosphor minimized.
For help with your design, contact your Technomark Sales Engineer.