Secondary Optics and LED Luminaire Design

    November 25, 2014

One of the challenges of LED design is the accommodation of not just a primary optic to collect, focus and shape the light produced, but the need to also accommodate secondary optics (those that exist outside the LED package) as well. These include reflector cavities, Fresnel lenses and pillow lenses. 

As secondary optics are essential to create the desired appearance and beam pattern of an LED light source, LED manufacturers must use designs that will keep the elements in place to avoid stray light or glare, and adhesive materials that assure consistent, reliable performance.

Henkel’s comprehensive offering of LED-compatible LOCTITE adhesives, sealants, potting materials and threadlockers includes several lens bonding and sealing products used in secondary optics manufacturing applications. These include LOCTITE 5510™ Adhesive/Sealant, which offers a fast skin time and is ideal for bonding dissimilar substrates that are subjected to joint movement or impact. LOCTITE E-30CL™ epoxy adhesive is an impact-resistant glass bonder with exceptional chemical resistance, and LOCTITE Superflex Non-Corrosive RTV Sealant offers resistance to water, steam, chemicals and UV ozone exposure. 

Compatibility between LED lighting and adhesives is also a factor when the LED is sealed into a housing, where it may off-gas into that headspace within the housing. When that happens, VOCs can be released into the LED assembly that could cause the light modules to discolor, reducing the clarity of the LED light. If the adhesive is not compatible, discoloration occurs rapidly – sometimes within hours – resulting in a reduction of light level. 

This is why LED designers and manufacturers cannot afford to take adhesive compatibility for granted – there are simply too many variables and exceptions within chemistries that can be detrimental to product quality. One of the most significant benefits of LED lighting is how long it is supposed to last – up to 50,000 hours in some indoor and outdoor applications. LED-compatible LOCTITE products bond subcomponent assemblies and basic structural elements to help ensure that long life, even for components exposed to extreme conditions.

Download our LED Design Guide for product guides and additional information about LOCTITE LED adhesive solutions from Henkel.

About the Author, Michael Pomykala

Mike is an Application Engineer for Henkel North America, based in Rocky Hill, CT. He is responsible for specialized technical support of the Electrical and Optical market and Defense market for North America. Mike also provides general technical support for the North Central region of the United States. Mike has been with Henkel for two years. He spent his first year in the Prism Program – a rotational program that provides training in various business roles throughout the General Industry segment at Henkel. Mike also holds Bachelors and Masters degrees in Chemical Engineering from the University of Connecticut.

Other posts by


Please make sure your comments are respectful and appropriate. All comments will be reviewed by an administrator, and if approved, will then be displayed on the page.

Leave a Reply

Your email address will not be published. Required fields are marked *