SUDBURY, MA—DELO has developed a new transparent, active-alignment adhesive for assembling automotive headlights.

Photobond OB4210 is characterized by its yellowing stability at high temperatures. It is highly resistant to temperatures and media.

The UV-curing adhesive’s transparent characteristics make it hardly distinguishable from the lens material. Its yellowing resistance is higher than similar products, retaining its transparency even after a typical 500-hour storage period at 140 C. This is important for bonding increasingly powerful LED modules that generate more heat. The acrylic adhesive works with a variety of materials found in a headlight, where it has stress-equalizing effects and a wide elasticity range. Thanks to its near-instantaneous UV curing, it is suitable for high-end applications such as the active alignment of lens systems and optics in matrix LEDs, microlens arrays, or digital light-processing headlamp systems. 

In addition to an application temperature range of -40 to 140 C, the adhesive has a high compression shear strength of 35 MPa on polycarbonate, a common optical material in the automotive lighting sector. Its low viscosity of 3,000 mPa-s and subsequent good flowability also facilitates applications on larger surfaces. The exposure time required to cure the adhesive can be reduced to 1.5 seconds at high UV intensities, and therefore offers process advantages in the form of higher cycle times in production.

Photobond OB4210 addresses two challenges for headlight manufacturers—miniaturization and increased functionality—since headlights are becoming increasingly slim and more powerful. Conventional assembly processes for headlights, such as threaded fasteners, are reaching their limits, and adhesives are increasingly in demand. To bond optics and lenses, however, they must meet stringent requirements. They should be stress-compensating and low-outgassing, withstand high temperatures and various environmental influences, and still remain highly transparent.