The light-emitting diode (LED) lighting market is growing steadily due to consumer acceptance of the energy-efficiency advantages of LED technology. To remain cost-competitive, many manufacturers choose plastic materials for their applications, due to greater design freedom and lower assembly cost.
Customers are accustomed to the soft white diffused light from incandescent bulbs. To this end, many plastic manufacturers incorporate precisely engineered diffusion additives into their plastic. The pellets that are subsequently created can be injection molded into parts such as lenses, or processed by extrusion into profiles, sheets and films. This “built-in” diffusion offers the advantage of eliminating a secondary operation that adds to system cost, and also allows for greater design flexibility in the molded shape.
Scientists at Covestro discovered that older diffusion additives, which tend to reflect light, did not meet LED light transmission requirements. In order to achieve a high lumen output while maintaining an acceptable level of diffusion, Covestro utilizes a light diffusion technology focusing on light refraction versus reflection, which leads to higher light transmission (Figure 1).