In this blog post, we will explore the principles of smartphone touchscreens, the characteristics of capacitive touchscreens, and the science behind screen protection technology.
Smartphones have become an indispensable part of modern life. With everyday use, it is easy for small scratches to appear on the screen, so manufacturers use protective films or reinforced glass to prevent this. Normally, a glass screen would break if dropped on the floor, but smartphone screens with this protective coating are resistant to breakage under normal circumstances. What materials are smartphone screens and protective films made of?
To understand the material of smartphone screens, it is important to first understand the touch principle of smartphones. Smartphones use capacitive touch panels. This method uses static electricity to detect the position of your fingers, which requires very sophisticated technology. A smartphone screen is not simply a tool for receiving input, but a sophisticated sensor system that sensitively detects electrical signals even when the screen is touched, allowing it to determine the exact position and intensity of the touch. For example, when you touch the screen with your finger, electrons gather at that point, and the circuit on the back of the screen detects the minute changes in electric current that occur during this process to execute the user’s command. For this reason, it is possible to recognize all parts touched by your fingers, enabling simultaneous input from multiple points, and various technologies are being developed to increase the touch sensitivity of screens. Thanks to these technologies, we can easily perform precise tasks and various multi-touch operations using smartphones. However, the screen does not respond to fingernails, gloves, or clothing that do not conduct static electricity.
The structure of a smartphone consists of two plates (top and bottom) equipped with film. The top plate calculates the presence of input and its coordinates, while the bottom plate receives that information and sends a signal to the controller. Since all signals sent and received are electrical and light, if the top and bottom plates are made of opaque materials, the light will be blocked by the plates and will not be transmitted to the electrodes. Therefore, a transparent material with good electrical conductivity was needed, and various transparent electrodes were developed. Among them, ITO (Indium-Tin Oxide) film is the most efficient. This film is a film with electrodes formed by thinly depositing indium acid in a plasma state on PET, a widely known plastic material. It is transparent, conducts electricity well, and is stable at room temperature, making it harmless to the human body. However, ITO film alone is not resistant to external impact, so liquid crystal protection films and reinforced glass were developed to prevent the screen from breaking or scratching when accidentally dropped or exposed to rain or snow.
LCD protective film is a film that is placed over the screen to protect it from fine dust and everyday scratches. This film adheres well to the screen even with low adhesion, is not highly reactive, and is made of a highly conductive material, usually plastic, especially PET or silicone. Silicone, in particular, is not only stable but also capable of forming various compounds with other atoms, making it widely used not only in smartphones but also in semiconductors. However, since film is also a type of plastic, it has the disadvantage of being easily scratched by knives and nails.
Tempered glass protects smartphone LCDs in a similar way to LCD protective films, but is much stronger than films. It is made by adding impurities during the cooling process of manufacturing ordinary glass. These impurities are larger than glass particles, so they take up more space and cause other particles to gather around them. In other words, it has a higher particle density, making it much more resistant to scratches. In addition, tempered glass has the advantage of feeling much better to the touch than film. However, compared to protective film, it is thicker and heavier.
As technology for protecting smartphone screens advances, the experience of smartphone users is also improving. Smartphone screens, which detect static electricity from the hands and process signals, are made of transparent electrodes with good electrical conductivity. The liquid crystal protection film and tempered glass used for screens have their own advantages and disadvantages. Films are vulnerable to scratches, while tempered glass is thick and heavy. Smartphone companies are currently conducting various research and development projects to solve these problems. For example, films that are scratch-resistant and less prone to fingerprints are being developed, while efforts are also being made to create tempered glass that is thinner and lighter while maintaining its strength. Recently, there has been active research into developing thin, flexible protective films that maintain high strength by combining glass reinforcement technology with nanomaterials. These technologies not only provide a more pleasant experience for users, but also play a major role in extending the life of smartphones. With these efforts by companies, we can look forward to the arrival of a scratch-free smartphone society.
