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Touch Screen Integration: Ensuring optimum translucency with proper bonding techniques


One of the most important steps when integrating a touch screen into an enclosure is bonding the touch screen display to a front element. Though it may seem straight forward, this is a key step that, if mishandled, can lead to critical errors including condensation or air bubbles appearing on the screen.

There are several methods that can be used depending on which type of touch display is being installed.

Optical Wet Bonding

Bonding for capacitive touch screen displays:

Optical Wet Bonding

Optical wet bonding is the preferred choice when bonding a rigid touch screen display with a rigid front, such as glass or plastic. When an optical bond is applied, it eliminates the air gap between the cover and the display. This greatly improves the display’s contrast ratio by reducing reflected ambient light, thus improving visibility.  It also increases durability and protection in outdoor environments.

Optical Wet Bonding Process:

  1. A rigid touch screen or display is selected for the application.
  2. An optically clear adhesive is selected and the operation is setup in a cleanroom environment.
  3. The adhesive is applied to the touch display with a special fixture and attached to a glass front.
  4. The full piece is then finished with a UV hardening method.

Note that the optical bonding process must always be performed in a cleanroom environment to prevent dust and other visible particles from becoming trapped between the touch screen and the display (and causing unintended optical effects).

Full-Faced Lamination

Bonding touch screen displays with flexible elements:

Full Faced Lamination

When dealing with a resistive touch screen and a flexible front, such as a front foil and window, full-face lamination is usually the best option. Fast and efficient, this approach uses a laminating machine to tightly bond the touch screen (or front foil) with a highly transparent adhesive foil. It is then applied to the internal side of a glass or plastic front, or applied directly to a solid touch display.

Airgap with spacer dots

Bonding for resistive touch screen displays

Spacer-Dots_RET

In this process, an enclosure with a rectangular cutout in the front, a continuous flexible membrane, and a touch display is separated by spacer dots. These dots provide a heightened level of touch responsiveness. They also help keep the touch display and front membrane from sticking together, which can create optical problems down the road.

Which is right for your application?

Each of these methods will provide optimal translucency, a flush front, and ensure costly mistakes (such as air bubbles) don’t appear. The question is less about which one is intrinsically better, but which one best meets your application needs.

The experts at Phoenix Mecano have perfected all of these bonding techniques through years of dealing with complex HMI projects, and can help you identify the right approach for your application. They also offer a complete range of services and capabilities to take your touch screen integration project from start to finish, quickly and efficiently.

See a full listing of our services and products at www.phoenixmecano.com.