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Mechanical Optical Bonding Configuration

Options available for bonding optical filters and substrates to touchscreens and displays to provide structural ruggedization and integrity.

There are a variety of design configurations that can be used for optically bonding components. Common components include cover glass, optical filters, touchscreens, and displays, but solutions are highly customizable based on the customer’s application needs.

  • Over-Touchscreen Bonding – This is typically a thin optical filter, so the required flexibility is maintained for the resistive touchscreen, and in the case of a projected capacitive touchscreen, the field strength stays within functional parameters.  

 

  • Under-Touchscreen Bonding – The optical filter can be of any size as long as it is greater than the optical area and the thickness can vary depending on system requirements.  

 

  • Over-Frame Bonding – This design uses the original frame of the display for mechanical support. A sealant prevents ingress of the bonding adhesives into the display electronics. The cover glass/optical filter or touchscreen rests over the frame of the display and is optically bonded to the front surface of the display.

 

  • Under-Frame Bonding – The frame of the display is removed, and the cover glass/optical filter or touchscreen is bonded to the front surface of the display. The frame may be replaced after the bonding process, or the bonded display may be integrated into a custom bezel or enclosure.

 

  • In-Frame Bonding – The frame of the display is left in place and the cover glass/optical filter or touchscreen is bonded within the frame inset area of the display frame.

 

  • Rear-Surface Bonding – The display is disassembled and a component (e.g., transparent heater) is optically bonded to the rear surface of the display. This design is commonly used for low temperature operation of LCDs and, in some cases, to improve the ruggedness and mechanical strength of the display.

 

In general, over-frame bonding is most typical, especially with touchscreens and digitizers. It is also the least invasive optical bonding process and preferred because the display’s frame provides additional mechanical support of the cover glass.  In the case of LCDs, it is important to avoid stress that can be induced by the bonding process, causing optical effects such as “glow marks” and “picture framing”.

DONTECH & Mechanical Optical Bonding Configuration

Dontech has extensive engineering and technical support resources that can assist you with your optical bonding mechanical design needs. Our technical staff have diverse backgrounds relevant to high-performance display and precision optics markets. For many of our top customers, we function as an extension of their engineering departments, supporting projects from concept to final system delivery. We will integrate our optical filters and other enhancing components into touchscreens, displays, and systems to the level that is needed by our customers.

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