Optical bonding is the process of filling the air gap between the LCD and glass with an adhesive or resin, such as silicone. Once cured, the silicone adds multiple benefits to the bonded display such as light refraction (from both LCD back-light and outside light), durability against vibration, water, and dust resistant, improved touchscreen accuracy, and prevents fog and condensation in humid environments.
When LCD displays are manufactured, including touchscreens, the front glass of the screen is layered onto the LCD module. This doesn’t present a problem in standard viewing environments, however in certain conditions, like with outdoor placement, the tiny gap between the 2 layers can impair viewing performance.