Industrial adhesives manufacturer, DELO, has developed a new adhesive for automotive lighting applications, the DELO PHOTOBOND OB4189. The product is resistant to yellowing and, with its high aspect ratio, is particularly suitable for bonding microlens arrays, such as those found in headlights and projection systems.
With light considered among the most important elements of automotive design and differentiation, microlens arrays are a key player to these developments. They project LED light, which sits behind a very short focal length, providing sharp images and individual geometries – resulting in their increasing use as optics in headlights and projection systems, due to their small installation depth requirements.
For increased efficiency, such microlenses are often made of optically-pure polymers, in other words, adhesives, and are then fixed to a housing. With a high viscosity of 75,000 mPa·s, DELO PHOTOBOND OB4189 enables a high enough aspect ratio for the bonding process, with the adhesive retaining its shape, rather than flowing, after dispensing, which is important for bonding microlens arrays. It is also extremely resistant to yellowing, which has been proven in 500 hours of lifecycle simulations at 140°C. This resistance is essential for such optically demanding applications.
The modified acrylate used in the new product is solvent free and has been developed for a temperature application range of -40°C to +120°C. It has a compressive shear strength of 30MPa on polycarbonate and 25 MPa on PMMA and can be cured using UV light at 365Nm wavelength and visible light at 400Nm wavelength. The typical exposure time at 400Nm with a layer thickness of 100μm is five seconds. This enables high precision active alignment processes for optical components and low cycle times in automated production.
“With DELO PHOTOBOND OB4189, we added a high viscosity and extremely yellowing resistant product to our portfolio of temperature and humidity resistant active alignment adhesives, that is precisely tailored to the requirements of microlens arrays,” says Christoph Appel, product manager for automotive LED at DELO.
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