Henkel Corporation has expanded its line of silicone Loctite Liquid Optically Clear Adhesives (LOCAs) to include patented formulations that fixture in less than 2 seconds, require 3 to 10 times less energy to cure than traditional one-part silicone LOCAs, and are fully compatible with either 365 nm or 405 nm LED light sources. Specifically designed for direct bonding cover lenses or touch panel sensors to LCDs, the newest silicone LOCAs offer radically increased cure speeds and highly advanced optical properties after RA testing. A 750 micron thick lamination delivers a b* value of 0.3 for yellowing and 0.2% haze after 500 hrs QUV aging, with 50% less yellowing and 95% less haze when compared to traditional one-part silicone LOCAs.
Five products with ultra low shrinkage and high flexibility are available in the Loctite® LOCA silicone line. All these silicone LOCAs minimize MURA by reducing the stress created during cure and better distributing stress over the display area.
The newest products in the silicone LOCA line, Loctite 5191 and 5193 silicone LOCAs and matching dam, Loctite 5191DM, feature a patented chemical breakthrough that radically increases cure speed and improves optical properties. As Loctite 5191 cures solely on exposure to UV light, it is easier to handle in some lamination equipment. Loctite 5193 cures on exposure to UV and moisture, which provides excellent cure in shadowed areas. The low viscosity LOCAs are easy to apply and are designed for high efficiency production processes, requiring only 2,000 mJ of energy for full cure.
Loctite 5192 and its matching dam, Loctite 5192DM, are used in many high volume display applications. UV curable Loctite 5192 cures with moisture in shadowed areas, protecting the display from problems with uncured adhesive such as bubbles, delamination, MURA and/or adhesive migration into the backlight unit of the LCD. The dual cure capability ensures full adhesive cure and robust display performance, and eliminates the cure-through depth limitation of side curing and the work-in-process and potential LCD damage of heat curing.