About Optical Bonding

Originally developed for avionics and military displays, optical bonding is now moving into industrial and consumer applications such as touch screens, TVs, smartphones, digital signage and medical imaging.

Optical bonding (LCD bonding, direct bonding) refers to a protective glass or touchscreen that is glued in front of a display to enhance its readability in high humidity outdoor environments. When a normal display is used in an outdoor environment, there are some factors that affect its readability. The most common one is “fog”, or condensation, which forms on the inner surface of display's vandal shield. Another factor is the reflection of sunlight, which causes a mirror-image on the display. Both phenomena can be solved by using optical bonding.

Optical bonding is the use of an optical-grade silicon-based adhesive to glue a glass or touchscreen to the top surface of a display. The assembly is cured in a process that affixes the display together while solidifying the adhesive. The main goal of optical bonding is to improve the display performance under outdoor environments. This method eliminates the air gap between the cover glass and the display. Moreover, anti-reflective coating is often used in optical bonding glass. The real problem for display readability in outdoor environments is not the display's brightness but its contrast. Contrast means the ratio of the white level to the black level; in other words, the contrast ratio of display means the difference of light intensity between the brightest white pixel and the darkest black pixel. The main purpose of optical bonding is to increase the display's contrast ratio by reducing the amount of reflected ambient light.

Benefits

Increased Ruggedness (up to 300%)

Bonding a sheet of glass on top of the display increases the ruggedness of the display.

Improved Durability:

A bonded display is better able to resist scratches, fluids, stains and dirt.

Condensation:

The elimination of an air gap between the cover glass and the display means that moisture cannot penetrate and cause fogging on display’s surface.

Increased Sunlight Readability (up to 400%):

By reducing the amount of reflection, the contrast of the bonded display is enhanced. The higher the contrast, the easier it is to read to display screen.

Extended Temperature Range and EMI Filtering:

The temperature range of the display can be extended by incorporating ITO heaters on the cover glass; EMI filters can be added via the same mechanism.

Applications

Industrial: Impact and environmental resistance, increased visibility and durability are all of increased importance in today’s fast-paced industrial environments. When down-time cannot be afforded then using 100% quality tested, ruggedized display units becomes crucial.

Advertising and Kiosk Displays: The additional structural integrity and environmental stability insure long life-cycle and superior performance from your public LCD display products.

Medical: Visibility in all lighting conditions is crucial, as is the ability to sterilize and maintain function during emergency situations in a range of environments.

Marine: Full optical bonding seals sensitive displays to safely improve function when exposed to harsh environments including moisture, vibration, glare and difficult light and temperature extremes.

Avionics: Vibration, G-shock and environmental extremes dictate extremely robust design. The full optical bonding combined with increased backlight performance insures the performance under any conditions.

Military: In a world where the unknown is around every corner, military applications are by far some of the most demanding. Structural integrity and environment imperviability are of paramount importance when a soldier’s life is on the line.