Learn how we meet MIL-STD-810F with our Cold Temperature Optical Bonding process!
Optically bonding an LCD, OLED or Plasma display improves both optical performance and durability. By selecting an appropriate adhesive that matches the index of refraction of the flat panel and the overlay, General Digital is able to remove all of the air gaps, thus reducing the number of internal reflecting surfaces that can lead to degradation of optical performance. Providing a durable adhesion between the flat panel and the overlay improves the displays’ ability to resist shock, vibration and moisture.
Optical Bonding is the affixing of two optical elements to one another using a liquid adhesive. The qualifier optical implies that the adhesive is transparent, has a suitable refractive index and is made under adequate control such that there are no significant variations in the optical properties within a single bond. In this way, we differentiate bonding from lamination.
On the practical side, the adhesive must also provide adequate bond strength, have a reasonable pot life after preparing, not present any health or safety issues, be available at reasonable cost from reliable sources, and cure to the proper finished bond condition using temperatures and times that are friendly to optical bonding facilities. Fortunately, there exist a relatively large number of choices. Typical bonded overlays include contrast enhancement filters, EMI/RFI filters, vandal shields, touch screens, and thermal heaters.
Augmentation of Optical Performance of Flat Panel Display and Overlay
Improved Ruggedization
Extended Operating Temperature Range Through the Use of Optically Bonded LCD, OLED or Plasma Display Heaters
Elimination of Condensation and Moisture Between LCD, OLED or Plasma Display and Overlay
Silicone-RTV
Epoxy
Another adhesive that we have used successfully is a flexible epoxy formulation. This makes a much more rigid bond than silicone, but does not have the tendency to form particulate debris. It is not reworkable in the event any problems arise during production or use. However, for some designs in which the use of tape to seal the edge is not practical, this may be the adhesive of choice.
Polyurethane
Polyurethane adhesives possess good environmental integrity for use in high altitudes and may be superior at low temperatures. However, they exhibit a severe yellowing over time when exposed to high ambient (solar) lighting conditions. Because of this tendency to yellow, General Digital Optical Bonding Laboratories discourages the use of polyurethane adhesives
There are numerous configurations available, including over-the-frame, in-the-frame and under-the-frame, as well as behind-the-display and frameless designs. Each have their own unique attributes.
Our first experience in optical bonding was with under-the-frame bonds for the GenStar™ monitor, a 20.1" LCD used in an FAA control tower application. This large size created some severe concerns about handling and yield. Our experiences with this were, however, very good. During 2002, General Digital Optical Bonding Laboratories bonded approximately 500 of these displays with a yield in excess of 95%. It was our early success with this product that encouraged us to offer the bonding service to other customers.
The in-the-frame design is currently in limited production, primarily for avionic applications. The adhesive is epoxy, which was selected so that the bezel could be affixed to the display’s metal frame, with the bonded antireflective glass extending into the opening, reducing any issues of viewing angle and parallax to the display.
One drawback to the under-the-frame and in-the-frame bonds is that they are not suitable for making a liquid-proof seal to the bezel of the monitor. To accomplish this, monitor builders usually prefer to form a seal to the antireflective glass. In this case, an over-the-frame bond is necessary. This bond design is also required in the case of an optically bonded touch sensor. The details of the bond may vary slightly, depending on the nature of the overlay. However, in general, an appropriate gasket is placed onto the face of the OEM frame, forming a well-defined bond thickness and protecting the edge of the seal from abrasion.
It is, of course, possible to bond more than one overlay to the display. A specific example is the use of a conductive glass to control EMI, which is bonded to a touch sensor. As of this writing, General Digital Optical Bonding Laboratories has produced over 475 displays of this design for an aerospace application.
Gasketed Optical Bond
Shimmed Optical Bond
Static Optical Bond
Single Optical Bond Layer
Multiple Optical Bond Layers
Optical Bonding to Both Surfaces (front and back) of LCD, OLED or Plasma Display
Glass (overlay) to Flat Panel
Glass to Glass (robust anti-vandal shield, similar to automotive safety glass)
Polycarbonate to Glass (flat panel) [under development]
Contrast Enhancement Filters
Anti-Vandal Shields
Rugged filters are available in various thicknesses and diagonal sizes to protect the display from harm. Highly resistant to impact, scratching, and chemicals, they are available in several surface finishes to provide optimum viewing of a flat panel display based on a particular application. All finishes are designed for antiglare, maximum light transmission properties, and durability.
Substrates used can be polycarbonate, acrylic, chemically strengthened glass, or thick (6 mm or more) glass.
In many cases, bonding standard glass to the LCD, OLED or Plasma display is sufficient to withstand significant abuse in the field without failure.
EMI/RFI Shields
Enable Display Assemblies to Satisfy FCC and MIL-STD-461 Requirements
Optically Clear ITO Coatings Down to 5 Ohms/Square
Configurations
Heaters help to extend the operating temperatures of flat panel displays and backlights, which will improve the LCD, OLED or Plasma display performance, especially at low operating temperatures. Typical applications include avionic displays, ruggedized electronic devices, handheld terminals, and outdoor card readers.
Heaters
Optically Clear (ITO)
Can be Combined with Other Coatings and Filters
Extends the Expected Life of Backlights When Operated at Cold Temperatures
Touch Sensors
Touch sensor technology simplifies and improves the human interface to the display system. Rather than using keyboards, switches or buttons, designs now include touch technology to increase design flexibility while delivering a better overall user experience.
Types of Touch Technology Available
Support for virtually any touch technology or manufacturer
Privacy Filters
Privacy filters protect the security of on-screen data. Only persons directly in front of the filter will see the screen clearly. A specially-designed film blacks out the screen at viewing angles greater than 30 degrees, side to side.
Various filter sizes available
GenGard F801™
*Extremes are limited by component selection (e.g., LCD and overlay)
†Optical bond only; selection of display, overlay and other electronics will affect temperature extremes of the complete assembly
‡Compliance is influenced by many design and integration factors, which is best discussed with an Applications Engineer to ensure that the customer’s requirements are met
Download the Data Sheet
Download the Product Announcement
XO-Fraim™
Extended Temperature Optical Bond
Cold Temperature Optical Bond
General Digital’s Optical Bonding Laboratories has thermal tested displays to -55° C. Bond failure occurs after temperature cycling; delamination and other anomalies are present. Our cold temperature bond formula prevents delamination and other bonding anomalies. We understand the needs of these unique display users and have designed a bond formulation with these considerations in mind. In addition to providing the optical bonding benefits of improved brightness and contrast, cold temperature optical bonding improves the overall ruggedization of a display. We also offer in-house thermal testing to your specific requirements. Please contact us to learn more about our cold temperature optical bonding solution, and to discuss your design and the many ways in which you can benefit from this solution.
Antireflective (AR)
Antiglare (AG)
For further information regarding optical bonding or to request a quote for your application, please
contactone of our qualified Sales Engineers.
Easy-Clean (smudge resistant)