Structural bonding and optical bonding for head-up displays (HUD)

Polyurethane structural adhesives bond a variety of different substrates such as plastic, metal and wood. They have strong resistance to humidity and other environmental factors and are known for their cohesive strength and flexibility in use. Henkel offers many types of polyurethane adhesives and here introduces a successful customer case with a polyurethane-based reactive hot melt for an automotive display component head-up display.

Henkel recommended a soft and flexible adhesive in consideration of the CTE difference of the substrates (thin PC film and plastic frame structure in HUD). It is a one-component polyurethane-based reactive (PUR) hot melt adhesive. This product is suitable on account of several benefits that meet the customer's requirements for structural bonding of HUD, such as:

• High creep resistance and reliability under thermal cycle condition
• Bond dissimilar substrates and gap filling
• Fully automated process realisation and cost reduction

In the industry there are two main types of optical bonding materials: Liquid Optically Clear Resin (known as "OCR") and Optically Clear Tape Adhesives (known as "OCA"). Henkel is an industry leader in Liquid Optically Clear Resin (OCR) technology, which we call "LOCA", that provides numerous benefits for flexible designs, faster cure speeds and higher optical performance compared to tape or film-type adhesive. On HUD applications, Henkel's liquid optically clear adhesives (LOCA)—which can be cured under UV—are used. The UV light-curing capability gives a good advantage. Since the liquid adhesive cures instantly to a solid polymer when exposed to UV or visible light, fully automated and improved process efficiency can be expected as well.

As the leading company for Sustainability, Henkel's structural and optical bonding solutions on automotive displays are unique and offer a significant waste reduction compared to manufacturing processes that use the tape-type adhesives conventionally deployed in this area. For further details about the HUD success story, please download the full paper below.