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 hotmelt 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) hotmelt adhesive. This product is suitable because 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 realization and reducing cost

In the industry there are two main types of optical bonding materials: Liquid Optically Clear Resin (so called "OCR") and Optically Clear Tape Adhesives (so called "OCA"). Henkel is an industry leader in Liquid Optically Clear Resin (OCR) technology, and we call it "LOCA" which provides numerous benefits for flexible designs, faster cure speeds, and higher optical performance as compared to tape or film type adhesive. On HUD application Henkel’s liquid optically clear adhesives (LOCA) which can be cured under UV is 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, the 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 reducing the waste on manufacturing process largely compared with the tape type adhesives which are conventionally used in this area. For further detail about the success story in HUD, please download the full paper below.