PC in the LED tube application in the end stronger than the opponent in the end?

Fluorescent tube lighting has become ubiquitous in business environments such as offices and factories. Although this lighting is effective, the trend now is to replace the tube lights as the technology evolves into more advanced LED lighting. LED lighting is very desirable, because of its high efficiency, long service life. Replacing common fluorescent linear lamps with LED tubes, taking advantage of the lumen power ratio provided by Solid State Lighting (SSL) technology, presents design and optics challenges. To meet this challenge, lighting manufacturers often work with material suppliers and use advanced materials to achieve the desired lens aesthetic, assembly methods, and optical performance. This gives them a competitive edge in terms of performance and cost.

In this article, we will discuss the use of polycarbonates in LEDs, describing their physical and optical properties, and other capabilities that LED lighting designers provide.

In order to produce LED lamp materials, there are some criteria to consider. Plastics have become the material of choice, especially polycarbonate because of their unique properties and versatility. Considerations include optical performance, mechanical properties, safety and design flexibility. These are introduced in this article one by one.

Optical performance

LEDs can be very bright unidirectional sources, and the materials the manufacturer needs either allow the light to strike the surface directly for maximum brightness or provide a uniform light distribution. LED manufacturers and designers know that it is hard to find a material that hides LED light and allows the light to travel at optimal levels. This is not only important for aesthetics but also ensures the best possible energy efficiency.

The cover of the LED source regulates the amount of light that is emitted or diffused. Customers often look for materials that provide high definition and purity to ensure optimal light transmission and maximum efficiency. However, manufacturers are also concerned with the uniformity of light distribution. Polycarbonates can be tailored to the specific needs and pass the compounding process to meet the specific requirements of the application. For transparent polycarbonate resin, the light transmittance of up to 90%. In some cases, polycarbonate resins contain light diffusion additives, which are usually polymeric materials with specific geometries, particle sizes and refractive indices that help to balance the required light transmission and light diffusion. For these polycarbonate resins, excellent light uniformity can be achieved while hiding the LED light source, eliminating "hot spots."

To achieve the best light distribution, meeting both the needs of the suppliers and the end-user's expectations, tests should be conducted prior to starting the production of LED lenses or housings to accurately quantify the light transmittance and light diffusivity of these polycarbonate resins. The effect of different light diffusants at different concentration levels in a sample was measured using a variable angle photometer and a direct light source when determining the D50 angle (ie, the amount of transmitted light is 50% of the amount of transmitted light at 0 °). The developer selects the appropriate diffusion technique based on the measured data.

 

Figure 1: Assess the diffusivity of LED tube material by measuring relative transmittance (percentage).

Adjusting performance is usually a cautious balance, as material additives for light diffusion can affect the efficiency of light transmission and illumination, and vice versa.

Mechanical behavior

LED is a solid state device, there is no fragile parts or filaments, it is very strong. In addition, LEDs have a very long life compared to traditional light sources. Polycarbonate, which has excellent toughness and is far superior to acrylic and glass, is the ideal material for lenses, covers or housings to ensure that the LED lamp or fixture is not damaged over its lifetime.

Although glass and acrylic resins meet some of the requirements of LED lighting, respectively, as shown in Figure 2, they are inadequate in terms of impact and heat resistance, as well as design flexibility. In contrast, polycarbonate and polycarbonate blends are increasingly considered as ideal starting points for LED applications because they have the necessary basic properties and can be tailor-made with other monomers, polymers or additives to meet specific Performance requirements.

 

UL (safety) requirements

LED tube not only for optical components, but also as a shell. Due to the LED technology, the electronics are placed inside, so the tubes need to comply with UL 94 standards. The standard bulb is not.

The requirements of resistance to ignition or flame retardance depend on the UL standard. High-power LED light source operating temperature up to 80-110 ℃. Polycarbonate resins provide excellent resistance to ignition for these types of operating conditions. Polycarbonates, acrylics and styrenics (such as styrene acrylonitrile-based SANs) can be considered as materials for lenses, covers and optics for low-voltage applications requiring Class 2 power to UL 94 HB and V-2 flammability requirements . For tougher LED lighting applications using Class 1 power supplies, materials for optics and lenses are UL V-0 and in some cases UL 5VA. In order to ensure the required flame retardance and compliance with the relevant UL 94 ratings, the components must be rigorously tested.

Testing includes the use of a blue flame, added to the sample at the appropriate exposure time in order to achieve the desired flammability rating. Total burn time, drop volume, combustion and glow burning levels, and cotton ignition levels were measured according to rating requirements. For UL 94 V-O certification, a 1 mm thick sample is exposed to a 20 mm flame for 10 seconds, removed for 30 seconds and then re-exposed for 10 seconds. The test settings shown in Figure 3. 5VA certification requires more rigorous testing, more stringent requirements. In the test, a 125 mm flame was placed on a square plaque sample (2.5-3 mm thickness) for 5 seconds and removed for 5 seconds, repeating the process five times.

 

image 3. LED tube material grade V UL94 test settings.

Polycarbonate is a clear plastic resin that provides the required light transmission, thermal stability and ignition resistance for these demanding applications at reasonable cost. In fact, polycarbonate resins have a very wide range of UL flammability requirements that are not possible with other transparent or lightweight diffusers. Polycarbonate is available for UL 94 flammability ratings of HB, V2, V0 and 5VA.

Design flexibility

Although LED tubes are increasingly used in general lighting applications, LED tubes have no standard shape and require design flexibility to achieve the desired value. One advantage of LED lighting is that manufacturers have a high degree of freedom in product design. Unlike traditional incandescent lamps, the lighting industry is no longer subject to aesthetic design, designers can actually "create light." Plastic materials can be used to install LED source or cover LED source, can be formed by injection molding, blow molding and other processes countless shapes and sizes.

Polycarbonate offers a flexible design choice, offering products for a variety of specific processing requirements. In addition, due to the relative strength and toughness of the polycarbonate, the weight, energy and cost of the components can be reduced. As previously mentioned, the ability of polycarbonate to make very thin parts also offers significant advantages for lighting applications, resulting in improved lumen output and higher efficacy, as thin diffusing lenses allow more light to pass through, which is Optical engineers very much expect.

summary

The material of choice for LED lighting applications has a significant impact on achieving the core benefits of LEDs. Traditionally, glass, acrylic, and plastic have been used, and the choice of material will depend on the features of the particular component, the environment to which it is intended to withstand, the characteristics of the LED chip, and regulatory requirements. Plastics have become the material of choice, giving OEMs and mold makers the best chance of gaining the maximum benefit from LED technology.

Materials for LED tube lenses need to provide a range of properties, including LED hot spot hiding, uniform light diffusion, maximum light transmittance, ease of manufacture, and UL flammability compliance. Particularly suited to meet all of these requirements, polycarbonate-based light-diffusing resins enable optical engineers to develop LED tubes with superior energy efficiency and robustness to ensure that LED tubes withstand the long life of LED light sources.

 

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