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Led Profiles

PTH is specialized in the extrusion of technical LED PROFILES in Polycarbonate and PMMA Transparent, Opal and Satin material.

Polycarbonate (PC)
High shock resistance (nearly unbreakable)
Good light transmission
Flammability rating UL94 "HB" to "V0" (depending on material type)
High heat deflection temperature (up to ca. 130 °C)
Available in transparent and opal
UV-stabilised Polycarbonate

Polymethylmethacrylate (PMMA)
Unmatched weather- and aging-resistance (no yellowness-effect from UV-radiation)
Very high light transmission
Flammability rating UL 94 "HB" (burns with very low smoke- and pollutant-level)
Reasonably shock resistant
Heat deflection temperature from 850 °C to 1000 °C (depending on material type)
Available in transparent, opal, diffuse/satin ( frost ) and individual colours
On request application of specific materials types the shock resistance for certain needs (i.e. vandalism) can be improved

LED
Light-emitting diode , is an electronic light source.
LEDs are based on the semiconductor diode. When the diode is forward biased (switched on), electrons are able to recombine with holes and energy is released in the form of light.
This effect is called electroluminescence and the color of the light is determined by the energy gap of the semiconductor. The LED is usually small in area with integrated optical components to shape its radiation pattern and assist in reflection.
LEDs present many advantages over traditional light sources including lower energy consumption, longer lifetime, improved robustness, smaller size and faster switching. However, they are relatively expensive and require more precise current and heat management than traditional light sources.  
Applications of LEDs are diverse. They are used as low-energy indicators but also for replacements for traditional light sources in general lighting and automotive lighting.
The compact size of LEDs has allowed new text and video displays and sensors to be developed, while their high switching rates are useful in communications technology.

PHISICS
Like a normal diode, the LED consists of a chip of semiconducting material impregnated, or doped, with impurities to create a p-n junction. As in other diodes, current flows easily from the p-side, or anode, to the n-side, or cathode, but not in the reverse direction.
Charge-carriers—electrons and holes—flow into the junction from electrodes with different voltages. When an electron meets a hole, it falls into a lower energy level, and releases energy in the form of a photon.
The wavelength of the light emitted, and therefore its color, depends on the band gap energy of the materials forming the p-n junction. In silicon or germanium diodes, the electrons and holes recombine by a non-radiative transition which produces no optical emission, because these are indirect band gap materials.
The materials used for the LED have a direct band gap with energies corresponding to near-infrared, visible or near-ultraviolet light. LED development began with infrared and red devices made with gallium arsenide. Advances in materials science have made possible the production of devices with ever-shorter wavelengths, producing light in a variety of colors.
LEDs are usually built on an n-type substrate, with an electrode attached to the p-type layer deposited on its surface. P-type substrates, while less common, occur as well. Many commercial LEDs, especially GaN/InGaN, also use sapphire substrate.
Most materials used for LED production have very high refractive indices. This means that much light will be reflected back in to the material at the material/air surface interface.
Therefore Light extraction in LEDs is an important aspect of LED production, subject to much research and development.

Polycarbonate vs. PMMA
The increasing adoption of LED lighting creates applications for polycarbonates that were previously the preserve of materials such as glass and metal. For instance, because LEDs emit “cold” light without infrared (IR) radiation, thermal stress on the lamp components is reduced, making it possible to replace glass lenses with those made of transparent thermoplastics, most notably polycarbonate and polymethyl methacrylate (PMMA). PC and PMMA have already been applied to LED lamps and luminaires, especially as parts of housings or transparent covers.
PC and PMMA components can be lighter and thinner than glass, and offer design flexibility. In addition, the components have been cost effectively scaled to production volumes using injection-molding processes. Relative to PMMA, polycarbonate benefits from greater heat resistance, higher impact strength and increased resistance to breakage. PC is also more flame-retardant.
Benefits of PMMA over PC include its higher light transmission (> 92%) and better resistance to UV radiation. Special grades of PC have a light transmission in the visible-wavelength range just under 90%, but they absorb radiation in the UV as well as mid- and far-IR regions.
UV exposure will damage standard grades of PC, resulting in an increasing yellowness that impairs the transparency of lenses and covers for lighting fixtures. To counter this phenomenon, a new infusion process has been developed to concentrate UV protection at the surface of PC products.

Polycarbonate resins offer an alternative to glass and polymethyl methacrylate for LED lighting fixtures, complementing the life span, efficacy and durability of LEDs themselves.
Technological advancements in light-emitting diodes (LEDs), such as higher lumen output and longer life spans, together with their expansion into the huge general lighting market require commensurate advancements in materials used in solid-state-lighting (SSL) products. Polycarbonate (PC) resins in various optical applications for LEDs such as lenses, covers, tubes, pipes, diffusers and reflectors offer a good complement with improved clarity and the ability to withstand high temperatures.
LED technology is rapidly changing to meet market demands for higher brightness, improved aesthetics, lower costs and longer useful life. These trends have raised concerns about components of LED lighting fixtures. One issue is how to increase the durability of these components to match the exceptional – and growing – life span of the LED modules themselves. Another is improving luminous efficacy (using less energy to achieve the same brightness), which is being addressed in part by increasing the light transmission performance of optical lenses and covers. Still another challenge is enhancing the quality of LED light for residential applications, making it softer and closer to incandescent lighting and avoiding hot spots, to drive consumer adoption. Finally, because LED costs remain comparatively high, it is important to protect these expensive modules with impact-resistant components.
Improved-clarity Polycarbonate technologies offer potential solutions to all these issues. Although polymethyl methacrylate (PMMA) and, to a lesser extent, glass, have traditionally been chosen for LED optical applications, both materials have drawbacks that these new Polycarbonate materials avoid. Further, as LEDs continue to evolve and raise the bar on requirements for optical components, the high-performance attributes of Polycarbonate accommodate new demands – higher temperature ranges, longer exposure to heat and tougher flammability requirements.
The latest Polycarbonate technology provides a comprehensive value proposition to meet current and future requirements from molders, manufacturers and regulators . This benefits package includes exceptional mechanical properties and durability, light transmission on par with PMMA, freedom to design and mold configurations and build in specific diffusion levels, and most critically, compliance with safety and sustainability mandates.
These Polycarbonate resins are engineered with improved monomers and are produced using a technologically advanced process. This process results in high-purity resins that provide significantly improved light transmission as molded and after heat aging, as compared to standard- and optical-grade Polycarbonate, as well as other performance enhancements. Improved-clarity resins are helping to drive the growing prominence of Polycarbonate in the LED market, particularly the general- and automotive-lighting sectors.
Let’s consider some of the major advantages of improved-clarity Polycarbonate over traditional acrylics and glass for LED optical components.

Polycarbonate life span
One of the chief advantages of LEDs is their extended useful life of >30,000 hours (more than 10-15 years). While this long life span means LEDs are more environmentally responsible and cost-effective than previous types of lighting, it raises concerns about the durability of LED lenses, tubes, reflectors and covers. Will these parts last as long as the LED itself without degrading from exposure to heat and ultraviolet (UV) light? Will covers and lenses effectively protect the expensive LED light source from impact and damage, particularly in residential retrofit applications where consumers handle, and sometimes drop, the replacement lights?
Improved-clarity Polycarbonate resins provide an array of performance properties that help LED lights operate effectively over their full useful life. First, Polycarbonate is renowned for outstanding impact resistance that surpasses the performance of PMMA by a factor of 10 in typical lab or practical impact measurements and that of glass by a factor of 30.
Because LEDs are increasingly used for architectural lighting, exterior lighting (e.g., parking lots, street lamps) and automotive applications, weather ability is critical to optimal light transmission and life span. Depending upon their formulation, improved-clarity Polycarbonate resins can provide UV and weather ability resistance according to UL746C with the necessary F1 rating. Resistance to UV light, which can cause yellowing and easy break of polymers, is a major aspect of outdoor exposure, however, even interior LED fixtures must be able to withstand UV radiation from ambient light and sometimes from the source itself. Improved-clarity Polycarbonate resins offer enhanced anti-yellowing performance to maintain light transmission and resist becoming brittle so they retain their excellent impact properties.
In outdoor lighting, transparent, weather able Polycarbonate resins offer a welcome alternative to both glass and PMMA because they combine high impact performance to protect the solid-state LED from vandalism and other threats, meet stringent UL requirements for weather ability and flame retardant and optimize forward transmission of light. In contrast, breakable glass does not provide sufficient impact protection, and PMMA does not meet UL94 V0 requirements.
Heat aging, another aspect of LED life span, is becoming even more important as high-brightness LEDs (HB LEDs) with higher lumen outputs place added stress on optical components. Improved-clarity Polycarbonate can handle extended exposure to temperatures of 110°C to 130°C, which is a developing trend for HB LEDs, while retaining their mechanical and optical properties.

Polycarbonate brightness
Some LED applications, such as down lights and spotlights for industrial or commercial spaces, call for maximum brightness. Also, designers and manufacturers are looking for ways to reduce LED costs by optimizing brightness while minimizing power consumption. In these cases, it is vital to take full advantage of every lumen produced by the LED module. In contrast, applications such as residential lighting require a uniform, diffuse light that hides hot spots. Covers, lenses, tubes and reflectors used with LED light sources play a crucial role in striking the right balance between transmission and diffusion.
Improved-clarity Polycarbonate materials offer high transparency that can provide approximately 90-92% light transmission, nearly comparable to that of PMMA. This capability makes them suitable for HB LEDs used to retrofit high-intensity discharge (HID) fixtures and fluorescents, as well as for flashlights and automotive headlamps.
When diffusion is required, specialized Polycarbonate resins can provide a broad spectrum of light management to customize performance without compromising forward light transmission. Different diffusion technologies can provide narrow-angle or wide-angle light scattering, while diffusers plus opacifiers combine translucent scattering with wide-angle light scattering. Polycarbonate manufacturers are able to tailor diffusion properties to meet customer requirements. Diffusion-based Polycarbonate products also provide a system solution that could potentially be more effective and cheaper than a diffuser film that is often used in such applications.
Specialized anti-dust grades of Polycarbonate can meet requirements for reflectors used in LED down light applications. These reflectors need to provide diffused light (rather than specular reflection) and retain their reflective properties over the life of the down light. Anti-dust capability helps to maintain long-term reflectivity performance. At the same time, although the Polycarbonate grades are highly filled, they retain their excellent mechanical properties. Finally, the design freedom provided by Polycarbonate facilitates the creation of diverse reflector shapes. In contrast, anti-dust PMMA materials cannot deliver equivalent mechanical performance and do not meet UL94 V0 flame retardant requirements.

Polycarbonate heat properties
LEDs generate heat that is not fully dissipated by heat sinks. Therefore, materials used for lenses, reflectors and covers in close proximity to the light source must be thermally stable and flame retardant. Heat generation is increasing due to higher brightness of LEDs that require at least 1W of power or more. Miniaturization to reduce material costs and meet market demands is also contributing to higher temperatures –not only are LEDs positioned closer to other components, but heat sinks are shrinking due to lack of available space and therefore are less able to dissipate heat.
In fact, typical operating temperatures for HB LEDs are already around 80°-90°C, and are expected to go higher by 20°-30°C as more powerful modules and smaller form factors are developed. Specialized Polycarbonate resins address this trend by providing thermal resistance up to 130°C, which represents an improvement of 20°-30°C over standard PMMA. Above 110°C, PMMA begins to deform. As mentioned earlier, improved-clarity Polycarbonate grades retain their high light transmission and mechanical properties after extended heat aging, even at elevated temperatures. Some of the LED replacements for higher wattage incandescent bulbs (e.g. 75W or 100W) already require temperature resistance over 120°C.
From a safety perspective, improved-clarity Polycarbonate resins provide flame retardant 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), Polycarbonate provides a higher ceiling in flame retardant 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 Polycarbonate 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.

Polycarbonate 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 Polycarbonate 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, Polycarbonate surpasses PMMA in the breadth of its design window. In particular, Polycarbonate 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, Polycarbonate maintains its impact and rigidity better than PMMA, which tends to sag. Similarly, Polycarbonate’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 Polycarbonate resins can contribute high light transmission combined with UV resistance, impact resistance and high heat tolerance to these distinctive designs.
Specialty Polycarbonate 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.
Polycarbonate 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. Polycarbonate 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.
Polycarbonate is becoming a preferred material for tubes, covers, lenses and reflectors in LED lighting designs. Specialized Polycarbonate 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, Polycarbonate resins provide the variety, performance and versatility to meet these new challenges.

 

 
 

PTH GROUP s.r.l. | VAT.NO: 02607310121

Via Ticino, 15 - 21043 CASTIGLIONE OLONA (VA)
Phone: +39 (0) 331 858378 | Fax: +39 (0) 331 824390
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