19-03-2024 | Schurter | Industrial
Developing touchscreens for outdoor use requires specialist knowledge. Based on many years of experience, SCHURTER engineers find the right combination of components, materials, software, assembly and integration for every situation. Its specialists analyse the specific application necessities and shape the design to optimise the touch panels for the intended outdoor use. Expertise and proactive advice throughout the development process result in reliable end products of the highest quality.
Thanks to the rise of smartphones, we have all become accustomed to the touchscreen. We can perform an infinite number of operating actions by touching the screen, swiping across the screen, or moving two fingers at once. However, touchscreens' application possibilities go far beyond what we are used to from our smartphones. Touchscreens are also gaining ground for operating machines and devices outdoors.
Apart from many advantages, it also has limitations: a smartphone is difficult to read in bright sunlight, and the screen quickly cracks if the device is dropped or hits a hard object. Yet there are plenty of ways to make touchscreens suitable for use in harsh outdoor conditions. For this, several factors need to be considered in the design. Outdoor control panels must withstand myriad weather conditions, including heavy usage and prolonged exposure to sunlight.
If water or another liquid hits the touch panel surface, it can cause unintended actions or malfunctions. Touchscreens used outdoors should, therefore, at least be resistant to rain, but often even to running water. In medical or maritime applications, the salinity of the water is a factor to consider, while these control panels frequently have to operate in extreme temperatures as well. One way to make touch panels moisture-resistant is to seal the front glass around the housing using gap encapsulation. Also, the structure of the sensor design and the firmware algorithms can be optimised, particularly for conductive liquids such as salt water. In addition, control panels in outdoor applications are often exposed to extreme temperature fluctuations, such as icy cold in winter or intense heat in summer. To ensure functionality, suitable materials and a robust construction are required.
Extra attention must be paid to readability to be able to use a touchscreen outdoors in bright sunlight. Also, prolonged exposure to the sun's UV rays can damage the touchscreen over time, resulting in a yellowed, opaque or even cracked screen. This detracts from the application's appearance and can affect its performance. The materials used must, therefore, be resistant to UV radiation, even with prolonged exposure to sunlight. Here, UV-filtering materials are often
chosen and certified according to ASTM G154 and MIL-STD-810H standards based on 1,000 hours of exposure in an accelerated UV ageing test. For optimum readability, the screen can be equipped with a non-reflective surface. In addition, an LCD display should be selected that offers a sharp, clear image and colour fidelity. For outdoor use, resistive touchscreen solutions are available with a film between two layers of glass (called glass-film-glass or GFG) or low- reflective glass, which is readable in direct sunlight. To further enhance readability, optical bonding of the display with the glass front panel and sensor can be chosen. This optical bonding eradicates the air gap in the structure and thus minimises reflections. Also, optical bonding increases the mechanical stability of the control panel. With reduced reflection, this technique provides a wider viewing angle, making the display more readable from different positions.
Machines for outdoor industrial use must withstand harsh conditions. They must be able to operate reliably, even in hazardous areas. However, applications placed in public spaces sometimes have to endure tough conditions. Vandalism resistance is an important requirement for these applications.
To ensure the safety and functionality of touchscreens, even under these extreme conditions, they can be fitted with an extra-thick front panel. Polymer composite-based materials can make unbreakable front panels that can withstand impacts up to the IK 10 standard. In such applications, the front panel is also equipped with an additional foil for increased protection against cracking and shattering. Thanks to robust housing and extra-strong components, control panels can be fitted with the necessary mechanical strength to withstand all expected environmental influences effortlessly.
