"Optical bonding" means "transparent liquid bonding". It describes an adhesive technique used to bond displays, touch or front glasses together with a high optical quality. Optical bonding helps an industrial touch display become more stable, protects against moisture and dust, and improves the optical properties. The unit thus becomes significantly more durable and of higher quality.
Due to significant improvements in automation and production, the advance in the industrial sector is unstoppable, e.g. in demanding medical and outdoor applications.
HY-LINE advises and selects the right bonding process for your application to deliver the optimal end product adapted to your needs.
The end user - at the ticket machine, at the point-of-sale terminal, on the construction machine - expects a display that is readable under all lighting conditions.
The system integrator can improve readability by using a material with better optical properties than air - optical bonding. The increased cost of the process is more than compensated for by the resulting benefits:
If you opt for optical bonding, the display becomes easier to read. You can therefore reduce the display's brightness. This has positive side effects:
When light passes from one medium to another with a different refractive index, most of it is refracted along the optical axis and some of it is reflected. The proportions depend on the ratio of the refractive index. In the case of a composite of cover glass, touch sensor and display, light from the environment, i.e. from the sun or artificial light sources, is reflected several times during the transition, which leads to a reduction in contrast.
Neglecting other components such as the surface finish of the cover glass or the internal structure of the touch sensor results in the ratios shown in the graphic below. On the left, light is first reflected from the surface of the cover glass, then from the underside of the sensor when it passes into the air between the sensor and the displays, and finally when it passes into the surface of the display. At each interface, about 5% is lost by reflection, so that a total of 15% of the light hitting the cover glass is reflected, degrading the contrast of the display.
If the air space between the sensor and the display is filled with a material (see graphic on the right) that has a refractive index similar to that of glass, only a small amount of reflection occurs there. The total reflection is thus reduced to 5%, which can be pushed to below 1% by an anti-glare or anti-reflective coating. However, the light emitted by the display is also reflected and contributes to a deterioration of the contrast with a reduced brightness due to the loss through reflection.
The white paper highlights topics such as components, application areas, advantages and challenges of optical bonding and explains in detail the individual bonding processes for display and touch. (This Whitepaper is in german.)