Electroluminescence is shedding a whole new light on everything from displays to safety gear.
Imagine a light source thin enough to wear on a T-shirt or adorn a magazine cover, efficient enough to run on battery
power and light a room, yet rugged enough to do duty as a billboard covering an entire building.
These are just a few of the fast-multiplying applications in the exciting world of lighting display that is being opened up by electroluminescent technology. You’ve probably seen it, without realising it. You know those lighting effects in the movie Tron that you thought were computergenerated? That was actually EL.
The technology is not new: it was being mooted for US aircraft instruments in the 1930s. However, advances – specifically, in materials suitable for thin film displays – have boosted development of the concept. So much so, that a local concern has convinced itself that EL is the next big thing and has made the switch from importing EL displays to becoming first in Africa to manufacture them.
“Essentially, we print micro-encapsulated phosphors (see “Inside EL”) to produce a variety of effects at a huge efficiency gain compared with conventional displays such as neon,” says Stephen Schutte, executive director of Cape Town-based Lumo Technologies. “The display operates at very low power – half that of traditional lighting. A typical setup uses the mains 220 V supply with a 12 V inverter.”
Lumo makes two types of display:
- A white backlit panel like a light-box, with light shining through a translucent overlay. Light intensity can be varied according to the amount of phosphors used.
- An animated electroluminescent panel. It’s the second method that has advertising and marketing specialists all agog. Because of the thinness of the material used in producing the display, it can be bent and shaped (anything short of an actual fold). It can be dropped into a table top, curved around a bottle, or moulded around a car’s bodywork.
A printed circuit board and an appropriate power source – say, miniature disc batteries, perhaps even solar – add to EL’s versatility. “Because the display is a moving as opposed to a static source, it’s been calculated that awareness is increased more than six-fold,” says Schutte.
The applications are wide-ranging. “We can light up DVD covers and high-visibility clothing. We have done a magazine cover.” It can be activated by sound, touch, even proximity.
As with all new technology, there’s a distinct slowness to embrace EL. “To get the market to understand that there are
no bulbs here is the hardest thing,” says Schutte. “Having said that, though, I have not been in a presentation where the client has not gone ‘wow’.”
Some fields are receptive, though. “We have had good response from the advertising world, especially the drinks business. They are aware of the possibilities.”
One of his company’s landmark (in more ways than one) installations has been a huge billboard that covers the entire frontage of a building in Cape Town’s nightlife artery, Long Street. To the uneducated eye, the nished product looks like a conventional animated neon display showing beer being poured into a glass.
“The question is, what would you normally use to accomplish this?” Schutte asks. The usual options are digital TV, neon and LED. “In this outdoor application TV is a nonstarter; neon costs 40 to 50 per cent more; and LED is hellishly expensive.” In the end, it cost about R1,5 million to achieve the desired effect – and you couldn’t do the same thing with alternatives unless you had deep pockets, he says.
But there are many, many more applications. And more become apparent all the time. “We have started to print for the
safety industry. We can do lanyards, harnesses, rope – we can produce a rope that lights for eight hours,” Schutte explains.
They are moving into the realm of vehicles, working with the likes of vehiclebranding company Graffiti, which does upwards of 100 promotional brandings of vehicles a month.
In-store, instead of the expense and complexity of running mains power down the aisles for their displays, supermarkets
could use self-contained battery-powered units. “We can incorporate a sensor unit to detect a customer in close proximity. This could lend a kind of ‘interactivity’ to the display, with possibly a touchscreen element as well that activates the lighting only when touched.
“This is opening up huge possibilities.” EL needn’t be restricted to the world of marketing and commerce, either. It surely wont be long before we’re able to simply touch a blank wall at home and see it spring into glowing life with gentle mood lighting that can be static or animated, according to our wishes.
Unlike incandescent lighting – which essentially uses the principle of heating materials until they glow – electroluminescence relies on an electronic reaction that causes certain substances to emit light. These substances are typically found in the form of a semiconductor and composed of rare earth compounds or transition metals.
In use, a strong electric field excites and accelerates the chosen material’s electrons. These electrons interact with semiconductor “holes” and release their energy as light.
One of the more common combinations used to create the kind of thin film used in the lighting applications shown here is zincsulphur-manganese (ZnS:Mn). The raw materials used in the local process cost nearly R1 million a kilogram and are sourced from China, which dominates world markets.
“Without divulging too much, we mix phosphors with chemicals and print a series of layers on an energy-conductive film,” says Lumo’s Stephen Schutte. “We then capture that with a laminator.”
Naturally, nothing is forever. Typical lifespan is about two years, after which time the phosphors degrade and light output drops.