Touchscreen display – the most intuitive way to interact with your device
Touchscreen displays are one of the technologies that have evolved tremendously over the past several years and have gained a lot of traction in various electronics industries. There’s a reason we are observing constant growth of their popularity – they provide the most intuitive way to interact with a machine or appliance. Therefore, when designing a device, you should consider using a touchscreen display to provide the best user experience and ease of use.
In this article you will learn about the most common types of touch panels and their applications.
Capacitive touch displays are among the most widely used today. They combine a number of important advantages, including relatively high transparency, support for multiple touch points, and the ability to cover the display with an additional protective layer. These advantages have allowed them to become a standard in most of today’s smartphones and tablets, as well as ATMs, self-service cash registers, and various types of operator panels.
Capacitive touch is based on the natural electrical conductivity of the human body. Transparent electrodes, usually made of indium tin oxide (ITO), are placed under the front glass layer of the display. Touching the surface causes a disturbance in their electric field, which is measured as a change in the capacity of a given electrode. A special controller continuously reads the state of the electrodes, thus determining touch coordinates. The controller is most often built directly into the touch panel tape or connector.
The method of operation of capacitive panels results in their biggest flaw – the possibility to operate them only with a bare hand or a special, capacitive stylus. In case of typical applications, such as everyday consumer electronics this does not pose any disadvantage. However, the problem starts to arise as soon as the user is wearing gloves. In addition, the touch reading can be easily interfered with, for example by the presence of water droplets on the display surface. Therefore, the usability of this type of touch panel in more demanding environments is very limited.
Resistive touch was one of the first technologies of its kind available on the market. Back then, it was dominant in primary touchscreen devices, like portable computers or PDAs. Although many competing technologies have since emerged, the specific advantages of resistive panels still make them an excellent choice for some applications.
The principle of operation is very simple. Resistive touch panels consist of two layers of transparent, flexible plastic, covered with a thin electrically conductive layer. The layers are placed at a certain distance from each other. If pressure is applied at a given point, they deform and come into contact, allowing the electric current to pass between them. An algorithm then calculates the touch coordinates by generating and measuring the voltage gradient across individual layers.
The main advantages of resistive touch panels are their simplicity and low production costs. Due to their uncomplicated design, making a touch surface of any size is possible and quite easy. Another great advantage is the ability to operate the touchscreen with any kind of object or material – including a stylus, finger, or even a gloved hand. Combined with their high durability, this feature makes resistive touchscreens the best choice in industrial environments or construction sites.
Resistive panels are not flawless, however. One of their drawbacks is the ability to read only one touch point at a time, so features such as gesture control are impossible to implement. Registering touch input also requires more pressure than other types of panels, which makes them far less user-friendly. Another major disadvantage is their relatively low transparency – they only let about 85% of light through, noticeably reducing the brightness and contrast of the display.
Optical touch panels
It is one of the touch technologies that does not require adding any extra layer on the display surface, therefore it does not affect the brightness and readability of the display in any way. All components responsible for its operation are located on the edges of the screen. These include infrared beam emitters and sensors receiving them. When a finger or other object is placed on the screen surface, the beams are interrupted at a given point. On this basis, the coordinates of touch are determined.
Another approach to light-based touch reading is optical imaging. The edges of such a panel emit or passively reflect light, which is obscured when its surface is touched. Sensors placed in adjacent corners of the screen are then able to determine the touch point by triangulation.
The technologies described above allow any flat surface – not just displays – to be easily transformed into a touch-sensitive surface. Interactive school whiteboards and projection screens are good examples of that. However, touch panels of this type have a relatively low precision. They are also susceptible to dirt, which can cause false readings. Unfavorable ambient light conditions, such as direct sunlight, can also interfere with their operation, or even make them unusable.
Bonding methods for touch panel and display
The way in which the touch panel is attached to the display is an aspect that is often overlooked. However, it does have some impact on the functionality of the display. The simplest method to attach the touch panel is to use an adhesive on the border of the display. Installing it in this way, however, leaves an air gap between the screen surface and the touch panel. This results in additional refraction and reflection points that the light must pass through. As a result, the brightness and contrast of the display deteriorates, which is noticeable especially in bright environments.
The solution to this problem is the use of transparent self-adhesive substances known as OCA (Optically Clear Adhesive) or LOCA (Liquid Optically Clear Adhesive). They form a uniform, transparent layer between the display matrix and the touch panel, eliminating the unwanted air void. Thanks to high transparency of the glue (over 99%), it does not negatively affect the display image.
Touchscreen display selection
When choosing a touchscreen display, you should consider the type, properties, as well as the method of bonding of the touch panel. For this purpose, it is worth seeking specialist advice, which our company offers.
InterElcom boasts one of the most attractive touchscreen display offerings on the market, both for industrial and consumer applications. Our wide range of products and the vast experience of our employees are the reasons why our company should become your electronic components supplier. We invite you to take a look at our offer of touchscreen displays and, if you have any questions, to get in touch with us using the contact form on our website.