With the rapid proliferation of smartphones, touchscreen technology has revolutionized our daily lives. Resistive, capacitive, ultrasonic, and infrared touchscreen technologies, each with their own advantages and disadvantages, have been applied to a variety of electronic devices, not just smartphones, to increase convenience and efficiency.
When you get on the subway on your way home and look around, there’s a common sight you see all the time. Almost everyone has a smartphone in their hand, watching a movie, browsing the internet, or chatting. A few years ago, this was not a common sight, but with the introduction of the iPhone by Steve Jobs and the rapid advancements in technology, it’s hard to find anyone without a smartphone. One of the key technologies that led to this smartphone craze is touchscreen technology. Unlike traditional feature phones, touchscreen technology eliminated the need to attach a license plate to the device, allowing the extra space to be used to create a larger screen, allowing users to watch movies, watch television, use the internet, and do other things that were difficult to do with traditional phones.
Touchscreens work in several ways: resistive, infrared, capacitive, and ultrasonic. A resistive touchscreen, also known as a pressure-sensitive touchscreen, consists of two substrates with transparent electrodes coated with a thin layer of air between them, covered by a film that prevents damage from impact and a softer, scratch-resistant film on top, which is the part we touch directly. Touch works on the principle of recognizing that when pressure is applied, the two electrode substrates in that area stick together, changing their resistance. This method has the advantage of being able to be used with any tool that can apply pressure, such as chopsticks or pens, not just fingers, and is the most common due to its low manufacturing cost. However, it has the disadvantage of being composed of multiple membranes, which makes it less durable and less sharp.
Capacitive methods utilize the static electricity that naturally flows through our bodies. A conductive glass called indium tin oxide is used as a liquid crystal, and when a current is passed through it continuously, electrons are collected where your finger touches it. This is recognized by sensors on the edges of the liquid crystal and that’s how it works. Because it uses a flow of electricity rather than pressure, it works with the lightest touch and has a very fast response time. It also uses tempered glass, so it’s more durable and has a higher resolution, which is why it’s mostly used in consumer electronics such as smartphones and tablet PCs. However, capacitive screens have the disadvantage of not working if there is any damage to the screen, and you can’t use them with gloves, wooden chopsticks, pens, etc. The touchscreen itself is also more expensive than a pressure-sensitive one.
The ultrasonic method, also known as surface wave technology, uses ultrasonic waves passing over the touchscreen panel to detect your position. When you touch the screen, some of the ultrasonic waves are absorbed by your finger, weakening the ultrasonic waves in that area, which is then recognized, recorded, processed, and sent to the controller. This method has a high panel transmittance, but it is easily damaged by external factors and is highly dependent on the cleanliness of the screen. It is mainly used in ATM machines and electronic blackboards because it is easy to make large screens.
Finally, the infrared method utilizes the straightness of infrared light, which means that it is blocked when it encounters an obstacle. When a finger touches the screen and blocks the light rays, the output drops in the blocked area, and the sensor recognizes and judges the area. This method can be realized with a single piece of glass substrate, so it has the highest panel transmittance and is often used for large screens.
Unlike traditional input methods, these various touchscreen technologies allow for accurate and convenient information delivery by simply touching what you see, making it easy to get what you want. When Korean companies entered the smartphone market late after the iPhone revolution, their biggest concern was that they couldn’t beat the iPhone’s tactile sensation. Now, of course, there are many smartphones that boast a more tactile experience than the iPhone, but the time it took for the iPhone to monopolize the smartphone market shows the importance of touchscreen technology. Now, touchscreen technology is everywhere, from smartphones to televisions, computer monitors, ATM machines, and movie theater ticket vending machines, and the possibilities are endless. It will be an important task for Korea’s electronics business to understand exactly how touch screens work and how to develop them further.
