Liquid optically clear adhesive (LOCA) is liquid-based bonding technology used in touch panels and display devices to bind the cover lens, plastic, or other optical materials to the main sensor unit or each other. These adhesives improve optical characteristics and durability. LOCA glue is often hardened using ultraviolet light. Primary advantages of LOCA compared to other adhesives are its: Re-workability Adhesion to non-even surfaces Superior optical properties Durability LOCA follows traditional die-cut film adhesives, also known as optically clear adhesives (OCA tape). LOCA also allows for thinner designs and new technologies, such as the use of silicone, that improve the properties of the final product. Overview Optical bonding, including LOCA and non-liquid OCA tape, are used in a wide range of electronic equipment, especially those with touch panels. The adhesive bonds the touch panel to the main liquid crystal display, and also bonds any protective cover, such as the lens, to the touch panel. After application, the adhesive is cured onto the device through ultraviolet light (UV), heat, moisture, or a combination, depending on the manufacturer and specifications. Major applications include capacitive touch panels, 3D televisions (3D TV), and glass retarders. Optical bonding improves optical performance of displays. It eliminates the air gap between the cover glass and LCD, and usually includes an anti-reflective (A/R) coating (as well as anti-smudge and anti-glare treatments on the cover glass). Optical bonding improves the contrast ratio by reducing the amount of reflected light, thus improving viewability. This is especially important in outdoor applications, where direct sunlight can decrease viewability. Fresnel reflections from the glass as well as the adhesive can degrade LCD viewability. Reflection is caused by an impedance mismatch between air and the glass. The reflection makes the white brighter, but dilutes black and other colors, which decreases contrast. LOCA suppliers aim to match the refractive index of glass and clear plastic PMMA (refractive index approximately 1.5) used in displays to minimize loss. LOCA suppliers such as Momentive Materials and Henkel report an increased contrast of 400% in sunlight through the use of LOCA with Anti-Reflective glass, vastly improving the viewing experience. Besides the optical advantages, bonding a sheet of glass to the LCD also improves display durability. It can resist scratches, condensation, and has an improved operating temperature range. As touchpad devices become ubiquitous in consumer markets, this increased ruggedness becomes even more important. Also, reducing light loss due to reflection