Industry News

Main types of LCD touch screen

2021-09-17

Main types of LCD touch screen  

 

From the technical principle to distinguish the touch screen, can be divided into five basic types: vector pressure sensing technology touch screen, resistance technology touch screen, capacitive technology touch screen, infrared technology touch screen, surface acoustic technology touch screen.  The touch screen of vector pressure sensing technology has withdrawn from the historical stage.  Infrared touch screen is cheap, but its frame is fragile, easy to produce light interference, distortion under curved surface;  The design of capacitive touch screen is reasonable, but the problem of image distortion is difficult to be solved.  The positioning of the resistive touch screen is accurate, but its price is quite high, and it is easy to scratch;  The surface acoustic touch screen solves the various defects of the previous touch screen. It is clear and not easy to be damaged. It is suitable for various occasions.  According to the working principle of the touch screen and the transmission medium of information, we divide the touch screen into four types, they are resistance type, capacitance induction type, infrared type and surface acoustic wave type.  Each type of touch screen has its own advantages and disadvantages. The key to understanding which touch screen is suitable for which occasion is to understand the working principle and characteristics of each type of touch screen technology.  

Here is a brief introduction to the various types of touch screens mentioned above:  

1, resistive touch screen (resistive touch screen working principle diagram)  

The touch screen is controlled by pressure sensing.  The main part of the resistive touch screen is a resistive film screen which is very compatible with the display surface. This is a multi-layer composite film, which takes a layer of glass or hard plastic plate as the base and is coated with a layer of transparent oxide metal (transparent conductive resistance) conductive layer.  It is covered with an outer hardened, smooth, friction-proof plastic layer, and its inner surface is coated with a number of tiny transparent points (less than 1/1000 of an inch) separating the two conductive layers.  When the finger touches the screen, the two conductive layers contact at the touch point, the resistance changes, and the signal is generated in the X and Y directions, and then sent to the touch screen controller.  The controller detects this contact and calculates the position of (X, Y), acting in a manner that mimics the mouse.  This is the most basic principle of resistance technology touch screen.  The key of resistance touch screen lies in material science and technology. The commonly used transparent conductive coating materials are:  

A, ITO, indium oxide, are weak conductors of electricity. When the thickness drops below 1800 angstroms (angstroms = 10-10m), ITO suddenly becomes transparent, with A transmittance of 80%. When the thickness drops below 1800 angstroms, the transmittance decreases, and rises to 80% when the thickness reaches 300 angstroms.  ITO is the main material used in all resistance technology touch screens and capacitance technology touch screens. In fact, the working surface of resistance and capacitance technology touch screens is ITO coating.  

B. Nickel-gold coating. The outer conductive layer of the five-wire resistance touch screen uses the malleable nickel-gold coating material. Due to frequent touch of the outer conductive layer, the malleable nickel-gold material is used to extend the service life, but the process cost is relatively high.  Although the nickel gold conductive layer has good ductibility, it can only be used as a transparent conductor, which is not suitable for the working surface of the resistance touch screen because of its high conductivity and the metal is not easy to achieve a very uniform thickness, so it is not suitable for the voltage distribution layer, but can only be used as an exploration layer. 

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