In response to consumer and government regulations for more environmentally friendly lighting products, LEDs continue to be the preferred choice over traditional lighting products. While polycarbonate (PC) resins in LED optical applications are already established, there are many new developments helping to meet market demands to increase brightness, lower costs and offer a longer life span.
Below is an article written by Bala Ambravan and published in the November/December 2012 issue of LEDs Magazine. Ambravan discusses that improved-clarity polycarbonate resins offer an alternative to glass and polymethyl methacrylate for LED lighting fixtures, complementing the life span, efficacy and durability of LEDs themselves.
“From a safety perspective, SABIC’s improved-clarity PC resins provide flame retardancy meeting UL94 V0 down to 1 mm and V2 down to 0.75 mm with high transparency. Although the global safety standards for LED lighting are still evolving (UL in the United States, IEC in Europe and in Asia, UL, IEC or specific local standards), PC provides a higher ceiling in flame retardancy and thermal resistance performance to accommodate evolving regulations. In contrast, PMMA does not meet these UL standards (it only complies with the UL94 horizontal burn rating).In addition to compliance with safety standards, these clear, flame-retardant PCs use technology that supports environmental directives. By avoiding bromines, chlorines and phosphates, these materials comply with eco labels and regulations such as the European Union’s Restriction of Hazardous Substances (RoHS) directive.
PC design options with LEDs
The general lighting industry is fragmented and complex. LEDs are adding complexities. The diversity of the market is creating the need for versatile materials that combine high performance with attractive aesthetics and innovative designs.
LED designs are already more diverse than those used for incandescent or fluorescent lighting. To address this trend, plastics such as PC offer a choice of processing methods (injection and blow molding, and extrusion), molded-in color and the ability to create complex shapes, including part integration. Glass presents significant design limitations in these areas.
When comparing plastic types, PC surpasses PMMA in the breadth of its design window. In particular, PC enables sharp corners and notches that can further accentuate PMMA’s weakness in impact strength. When extruding large diffuser sheets used for wall and ceiling LED applications, PC maintains its impact and rigidity better than PMMA, which tends to sag. Similarly, PC’s dimensional stability, as well as strength and toughness, enable thin-wall molding (ranging from 0.5 mm to 1.0 mm) for cost savings and weight reduction as well as improved light efficiency.
One interesting area for LED design innovation is automotive head lamps. LEDs are being used for special lighting enhancements including so called angel eyes or accent lights providing a halo effect and in strips used for daytime running lights or fog lamps, which have been pioneered by Audi and Mercedes-Benz. Versatile PC resins can contribute high light transmission combined with UV resistance, impact resistance and high heat tolerance to these distinctive designs.
Specialty PC resins have also been engineered with high reflectivity performance. These materials can be used in head lamp reflectors to maximize the luminance of LED modules without the need for secondary coatings or plating. They also offer the opportunity to integrate the reflector into the LED module.
PC is an excellent choice in architectural lighting as well as automotive lighting for light pipes or tubes, which are used to move light from its source to its destination by channeling it over a few millimeters or up to 100 meters. Light pipes provide design flexibility and eliminate components and assembly steps. PC provides the right balance of optical properties (transmission and refractive index), durability and process ability (extrusion or profile) for these applications – particularly long, thin pipes.
PC is becoming a preferred material for tubes, covers, lenses and reflectors in LED lighting designs. Specialized PC grades have been engineered with a range of desirable performance attributes – from thin-wall capability to exceptional heat aging performance to sustainable flame-retardant systems – which build upon the material’s classic impact resistance, toughness and clarity. As LED technology races ahead, new applications are developed, new markets are penetrated and regulations evolve, PC resins provide the variety, performance and versatility to meet these new challenges.”
OrgaLED® Driveover Lines and Shapes are designed to create diffuse light lines which can be integrated into concrete or paving. The OrgaLED strip is encapsulate in a cast polyurethane resin within Epoxy coated Stainless steel bodies with IP67 connectors, creating diffused light lines which are suitable for pedestrian or drive over applications.
Available in all single colors and RGB. Standard lengths are 4ft and 8ft (max), which can be inter-connected with the IP67 daisy chain connectors. Special lengths are on available on request. Continuous runs from a single point can be up to 66ft for single colors and 33ft for RGB, or 132ft and 66ft respectively with T connectors. View Document Library.