Introduction and principle of touch panel

- Mar 21, 2020-

The touch panel is coated with a tin antimony oxide film (ATO Layer) and a protective film (Hard Coat Layer) on the surface of the transparent glass, and a shielded layer is required between the LCD monitor and the LCD monitor. The touch panel is a direct embodiment of touch technology, which is used to sense contact signals and analyze them.

 

Touch Panel Technology Introduction The touch panel structure consists of three parts: Sensor, Controller and Software. The sensor is the touch panel part, which mainly receives the information input through contact; the function of the controller is to analyze and calculate the position of the contact point, and convert the analog signal into a digital signal, so that the information equipment can accept the input signal; the software part The communication agreement between the information processing device and the controller allows the information processing device to receive and recognize the signal input by the controller for subsequent processing.

 

Touch panels can be divided into four types: resistive, capacitive, optical, and sonic according to different sensing technologies. The principles and characteristics of various technologies are introduced below.

 

1. Resistive touch panel

The resistive touch panel mainly consists of two sets of ITO conductive layers, spacers and electrodes. ITO glass is mainly used as the base board, and a layer of ITO Film is superimposed on it. Spacer support is distributed in the middle so that the upper and lower boards will not become conductive due to the close proximity. Silver electrodes are printed on the edges to provide voltage. When in use, pressure is used to make the upper and lower electrodes conductive, and the controller detects the change in panel voltage to calculate the position of the contact point for input. The advantages are waterproof, good antifouling, and affordable, but the disadvantages are poor scratch resistance and fire resistance.

 

2. Capacitive touch panel

Capacitive touch panels use the change in capacitance generated by the electrostatic combination between the transparent electrode and the human body to detect its coordinates from the induced inductance generated). The induction principle uses voltage to act on the four corners of the screen's sensing area and forms a fixed electric field. When a finger touches the screen, the electric field can cause a current to be measured by the controller. Depending on the proportion of the current to the four angles, Calculate the contact position. However, the capacitive touch panel must overcome the noise caused by static electricity caused by fingers or other touch media, so it is difficult to design the current and structure. The position can be calculated from the current ratio when subjected to touch pressure.

 

The components of a capacitive touch panel are: a conductive layer is plated on a glass substrate, an electrode layer is made, and a protective film is finally covered on the surface layer to complete the capacitive touch panel, because it is only on a single piece of glass As the electrode and conduction. Resistive touch panels need to overlap the ITO conductive layer of the upper and lower boards, which affects the overall light transmittance of the touch panel. Therefore, the capacitive light transmittance is higher than that of the resistive type, which can reach 90% or more. The product has better fire resistance, antifouling and scratch resistance, and is more resistant to dust and quick response.

 

3. Optical touch panel

The principle of the optical touch panel is to use the light source receiving and blocking principle. The panel is covered with light sources and receivers and arranged in a matrix. When the light is interrupted, the position of the signal receiver cannot be received, and its accuracy is determined. position. The components of an optical touch panel include a glass substrate, an infrared emitting source, and an infrared receiver. The structure mainly arranges the infrared emitting device on the left and lower sides of the glass panel, and sets infrared receivers on the right and upper sides. When a finger or a contact object blocks the infrared rays, the contact can be detected through the information received by the receiver The matrix position of the point. The advantage is that the surface is pure glass, which does not affect the light transmittance, the product has high reliability, scratch resistance, and good fire resistance, but the disadvantage is poor waterproof and antifouling properties. begging.