A Little Drop of Silicone
Rheometry samples in the lab
WACKER, however, now sells a new silicone elastomer (under the brand name LUMISIL®), which gives manufacturers the ability to make optical LED lenses in a single step: a drop of the silicone is dispensed directly onto the chip, where it is activated with UV light to cure it and shape it into the lens geometry.
“LUMISIL® allows us to manufacture optical lenses for light-emitting diodes in a way that is both economical and extremely fast – at an appropriately high throughput and with no complex molding step,” explains Dr. Phillip Müller, who bore the responsibility for developing this high-performance optical silicone. LUMISIL® has very smart flow and cross-linking properties, Müller points out, adding that the encapsulation process is sufficient to produce an optical lens with the ability to radiate light in a way that is ideally suited to general lighting purposes.
The benefits of LUMISIL® apply to more than the manufacturing process, however: its use is also recommended by the quality of the resulting materials. The silicone is light-resistant, does not turn yellow or brittle, and protects the semiconductor chip from heat, cold and other sources of stress, such as humidity. Lighting manufacturers use lead-free soldering techniques when processing an LED, which generates temperatures of 270 °C or more. Unlike other materials (such as the epoxy resins that used to be used), however, the silicone lens can easily withstand even this level of heat. “The use of WACKER’s UV-activated silicone plays a major part in the 15 percent increase in brightness that our LEDs produce,” says Dr. Michael Kruppa, senior manager for back-end technology materials development at OSRAM Opto Semiconductors, the lighting manufacturer’s LED subsidiary in Regensburg, Germany.
OSRAM Opto Semiconductors uses LUMISIL® for LEDs in its Golden Dragon Plus series, one of the manufacturer’s most widespread product lines for general lighting applications.
The following photo gallery showcases five applications – from South African World Cup stadiums to street lamps in Siberia to lighting for Danish greenhouses – featuring OSRAM’s Golden Dragon Plus series, which uses LEDs encapsulated with LUMISIL® from WACKER.
Five Examples around the Globe
LIGHT IN THE SIBERIAN WINTER
Kemerovo, a Siberian city of 520,000 residents located on the Trans-Siberian Railway, has been saving more than €20,000 per year since its large-scale conversion to LED street lighting. Replacing 200 street lamps has also reduced carbon dioxide output by over 200 kilograms each year.
Built into each of the street lamps manufactured by LLE TD Focus are 90 LEDs of the Golden Dragon Oval Plus series, which have been specifically designed for street lighting and meet the special demands of an efficient lighting solution with no light pollution. The light-emitting characteristics of the integrated, durable silicon lenses ensure that the LED light is only directed at those areas of streets and plazas that actuallyneed to be lit.
A BRILLIANT WORLD CUP
The Arch, the arc of LED light over Durban Stadium, quickly became the visual hallmark of the 2010 FIFA World Cup in South Africa. It spans this temple to soccer with over 12,000 Golden Dragon Plus LEDs. At 350 meters in length and weighing in at 2,600 tons, the 30-story Arch could be seen from a considerable distance and, as such, came to symbolize the coming together of some 70,000 sports fans at the stadium on the east coast of South Africa.
Energy-saving Osram lighting technology also found its way into nine other World Cup stadiums: Green Point Stadium in Cape Town, for instance, was fitted with LED beam lights made by African manufacturer BEKA – lights that likewise incorporated Golden Dragon Plus series diodes. The lenses for these diodes were cast from LUMISIL®, the igh-performance optical silicone from WACKER.
At 37 percent efficiency, Golden Dragon Plus diodes from OSRAM, which incorporate lenses of WACKER’s LUMISIL® high-performance optical silicone, are among the most efficient sources of deep-red light (roughly 660 nm wavelength) on the market.
This deep red plays an important role in plant growth, as plants absorb very high levels of chlorophyll in this range. A pilot project conducted in cooperation with Fionia Lighting A/S and Danish distributor Arrow confirms the huge energy-saving potential of LEDs on this market. Fionia Lighting A/S developed a customized greenhouse lighting system that, among other components, incorporates roughly 50,000 Golden Dragon Plus LEDs. These diodes emit light at an angle of 170 degrees, making them well-suited to reflector systems for large-scale crop lighting. Because they last for 100,000 hours, these Golden Dragon Plus LEDs can be operated maintenance-free for many years, during which time they will typically generate 330 mW from 400 mA operating current.
ATMOSPHERIC OLD-TOWN LIGHTING
OSRAM Opto Semiconductors and Siemens are working together on a joint pilot project that demonstrates how energy-saving LED lighting can be used in the heart of Regensburg, Germany, without compromising the style of this UNESCO World Heritage Site. Prior to now, the medieval plazas and alleyways of the city have been lit primarily with 90 watt mercury vapor lamps.
Creating agreeable lighting in keeping with the style of a historic city center means having to consider the various colors of the buildings and making appropriate adjustments to the way in which the light is used, its color temperature and color rendering index. Street lamps must not produce a glare in residential buildings, for instance, nor should they have a negative impact on the romantic atmosphere of candlelit restaurants.
Photo Source: OSRAM
PUTTING LUXURY GOODS IN A FAVORABLE LIGHT
Retail competition is intense these days, with rivals often right in the store next door or, at the very least, on the next street corner. Given the retail density in shopping centers and downtown shopping districts, the problem today is quite literally putting one’s own goods in the proper light.
A pleasant atmosphere and stylish aesthetics can make or break a purchase decision, especially in the mid range and luxury class of consumer goods. No matter what they are selling – high-heel shoes, blouses or handbags – or where they are selling it – in the showroom or store window – major department store chains such as Macy’s and Dillard’s rely on lighting as a critical tool for presenting their products in an attractive light. Leaving artificial lights on for more than twelve hours is not only expensive, however, it can also damage goods over the long term.