Plastics
technologies are evolving to promote more widespread use of LEDs for street
lighting and automotive headlamps.
One of the
interesting LED displays at K 2010 this week in Düsseldorf, Germany, features
custom polycarbonates made with a new multi-material injection molding
process.
Bayer
MaterialScience is showing LED lenses for headlights and fiber optics for
daytime running lights in the front headlamps of the new Audi A8.
The
components were developed in collaboration with Audi AG and Hella KGaA Hueck
& Co. The ten plastic lenses used in the headlamp are made from Makrolon
LED 2245, which offers high transmission for long light paths, high thermal
resistance and excellent yellowing stability to LED light.
"Our
material meets the high optical requirements for exposed headlamp parts and is
within the narrow color tolerance range. It also enables enhanced design
freedom and a considerable weight reduction," says Martin Döbler, an expert in
optical polycarbonate applications at Bayer MaterialScience. LED lenses are
around 50 percent lighter than their glass counterparts.
The
polycarbonate headlamps are expected to be particularly attractive to
manufacturers of electric vehicles, who are leading the fight against vehicle
weight.
The
rectangular, slightly curved LED headlamp lenses for the Audi A8 are 4 cm long,
2 cm wide and 1 cm thick. They cannot be produced via standard injection
molding because of the complex shape and thick walls of the optical components.
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A new
multi-layer injection molding process offers sophisticated mold temperature
control to provide dimensional stability and fast cycle times for
high-precision LED lenses with walls of greatly varying thickness.
Road Lighting
LED street
lamps made with polycarbonate in place of glass are also a Sabic focus.
The concept
was drawn up in conjunction with Cologne-based agency
DESIGNquadrat GbR because of efforts in
many European countries to reduce the costs of powering street lights. There
are 27 million street lights in operation throughout Europe.
Almost all
major international light manufacturers are working on concepts for LED street
lamps for a very good reason. A street light based on a 901 milliwatt-output
LED can produce the equivalent luminance as a traditional light with only half
of the power consumption.
The street
lamp on display at K 2010 is designed with a two-leaf floral shape. One leaf
incorporates six LEDs with one lens each. A photovoltaic cell is integrated in a
leaf pointing towards the sun to further reduce the amount of energy drawn from
the electricity grid.
"The design of the LED lenses shows that,
compared with glass, polycarbonates offer much greater design freedom for
precision optical parts," says Klaus Reinartz, head of the global LED project
for general lighting at Bayer MaterialScience.
Other
advantages of polycarbonate include its high heat resistance and high break and
shatter resistance, which protects the LED lamps against vandalism.
Expanded use
of polycarbonate in lighting fits into plans by resin producers to find new
markets to replace packaging applications that have been cut back because of
concerns
about bisphenol A in the transparent, high-impact plastic.
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