Touch screen type

Touch screen type

Touch screen types can be divided into several types according to various forms. First, according to the working principle of touch screens and the medium of information transmission, we divide touch screens into four types, which are resistive, capacitive, infrared and surface acoustic wave; The second is from the installation method, the touch screen can be divided into: plug-in, built-in and integral; third is to distinguish the touch screen from the technical principle, which can be divided into five basic categories: vector pressure sensing technology touch screen, resistive technology touch screen, Capacitive technology touch screen, infrared technology touch screen, surface acoustic wave technology touch screen.

Resistive touch screen

This kind of touch screen uses pressure sensing to control the main part of the resistive touch screen is a resistive film screen that fits well with the surface of the display. This is a multi-layer composite film. It uses a glass or hard plastic plate as the base layer, and the surface is coated with a Layer of transparent oxidized metal (transparent conductive resistance) conductive layer, and then covered with a layer of hardened outer surface of smooth and scratch-resistant plastic layer. Its inner surface is also coated with a layer of coating. There are many small (less than 1/ The transparent isolation point (1000 inches) separates the two conductive layers and insulates them. When a finger touches the screen, the two conductive layers are in contact at the touch point, the resistance changes, and signals are generated in both X and Y directions. Send the touch screen controller to the controller to detect this contact and calculate the position of (X, Y), and then operate according to the way of simulating a mouse. This is the most basic principle of resistive touch screens. The key to resistive touch screens lies in material technology.

Commonly used transparent conductive coating materials are: AITO, indium oxide, weak conductor, the characteristic is that when the thickness drops below 1800 angstroms (angstroms = 10-10 meters), it suddenly becomes transparent, and the light transmittance is 80%. The light transmittance decreases when it becomes thinner, and rises to 80% when it reaches a thickness of 300 angstroms. ITO is the main material used in all resistance technology touch screens and capacitive technology touch screens. In fact, the working surface of the resistance and capacitance technology touch screens is ITO coating. B nickel gold coating, the outer conductive layer of the five-wire resistance touch screen is used Nickel-gold coating material with good ductility, the outer conductive layer is frequently touched. The purpose of using nickel-gold material with good ductility is to extend the service life, but the process cost is relatively high. Although the nickel-gold conductive layer has good ductility, it can only be used for Transparent conductor is not suitable as the working surface of resistive touch screen, because it has high conductivity and metal thickness is not easy to be very uniform. It is not suitable for voltage distribution layer and can only be used as a probe layer.

Capacitive touch screen

The capacitive technology touch screen works by using the current induction of the human body. The capacitive touch screen is a four-layer composite glass screen. The inner surface and the interlayer of the glass screen are each coated with a layer of ITO, and the outermost layer is a thin layer of silica glass protective layer. The interlayer ITO coating is used as the working surface on the four corners. Lead out four electrodes, the inner ITO is a shielding layer to ensure a good working environment. When the finger touches the metal layer, due to the human body electric field, the user and the touch screen surface form a coupling capacitor. For high-frequency current, the capacitor is a direct conductor, so the finger draws a small current from the contact point. It flows from the electrodes on the four corners of the touch screen, and the current flowing through these four electrodes is proportional to the distance from the finger to the four corners. The controller obtains the position of the touch point by accurately calculating the ratio of these four currents