This week in the Display 101 series we will talk about the importance of the gasket that lies between the touch panel and the TFT.

So, let’s start from the physical aspect.

The physical connection between the touch panel and the LCD is crucial for the module’s efficiency. In the text below, we’ll describe both the physical features and the risks of bonding the LCD TFT with the touch panel.

Gaskets

When connecting the LCD with the touch panel it is important to keep in mind the physics. The cost-efficient solution is bonding by the double-sided adhesive gasket (we call it DST – double – sided tape).

The gasket thickness depends on the size of the module. We optimized those for:

 

module size thickness of the gasket
2.8” 0.3 mm
3.5” 0.3 mm
4.3” 0.3 mm
5.0” 0.6 mm
7.0” 0.6 mm

 

The advantage of DST bonding is tightness. The air gap between the touch panel and the LCD to provide the clear, undisturbed picture has to be free from any pollution. The tight assembly protects the module from the humidity and may protect from various chemicals dissolved in the air. Those can not only disturb a clean view but also be dangerous for the mechanics of the device.

The main advantage of using the gaskets is creating the distance between the TFT LCD and the touch screen. The distance is necessary because of electromagnetic radiation.

Why do we care about electromagnetic radiation?

Every electronic component emits electromagnetic radiation – LCD and CTP also. The distance in the assembly is the compromise of module thickness and its immunity for noise resulting from the radiation of attached TFT. We are scaling the touch sensor sensitivity and gasket thickness to get the most optimized solution for the module.

Talking about electromagnetic radiation it is worth to mention the EMC – Electromagnetic Compatibility. That is the ability of a given electronic device to work properly in a specific electromagnetic environment and not emit any noises (EM Susceptibility) that will interfere with other closely located devices (also be immune for the noises from the environment – EM Immunity).

To illustrate the issue – to not cause any disturbances when the radio plays next to it.

It is worth to mention that the electromagnetic interferences are caused by the emitted radiation (emitted by the device, as well as the environment), the compatibility is the equipment characteristic for the whole device ( application), not just it’s components (display module). What that means, it is worthless to certificate the component, if putting that in the environment of the whole final device the physics of electromagnetic phenomena changes utterly.

We hope you enjoyed our Display 101 post about the necessity of a gasket for smart displays. Tell us what aspect of smart displays you would like to read about next. Just send us a message on social media, or tag us in your post.