At present, there are many types of so-called touch screens. Generally, the touch screen is composed of different components from the liquid crystal display of the display device. A transparent touch screen is attached to the front of the display device. This kind of touch screen is called a "narrow" touch screen. Generally, the input medium is a finger. In addition, there are input devices that use special pens or recent LCD monitors that have touch
Touch screens with control functions have also been added, and these are called "broad" touch screens.
Narrowly defined touch screens are roughly divided into four types: resistive, capacitive, optical, and ultrasonic. Broad sense touch screens include electromagnetic induction type and In Cell type. These methods are classified in Figure 2-1. Because no touch screen is omnipotent, there are multiple touch screens. For example, the resistive type is the only superior method that does not choose to enter the media, but it has poor durability and is not suitable for the operation needs of the public. Although capacitive or optical touch screens are relatively expensive and have limitations in use, they are more suitable for products such as electronic kiosks that require long-term durability.
classifies touch screens from different perspectives, which can be divided into "electronic detection methods" and "non-electrical methods". The touch screen using electronic detection is mainly resistive and capacitive. In this case, it is necessary to use a transparent conductive film such as ITO (Indium Tin Oxide) or ATO (Antimony Tin Oxide), which may reduce the transmittance. However, its disadvantage is that even if this optical method is superior in optical characteristics, it will often have the shortcoming of erroneous operation.
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, on which is covered with a layer of hardened outer surface, 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 for insulation. 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 technology touch screens. The key to resistive touch screens lies in material technology. The transparent conductive coating materials are: ??
AITO, indium oxide, a weak electrical conductor, the characteristic is that when the thickness drops below 1800 angstroms (angstroms = 10-10 meters), it will suddenly become transparent, the light transmittance is 80 percent , and the light transmittance will decrease when it becomes thinner. When the thickness reaches 300 angstroms, it rises to 80 percent . ITO is the main material used in all resistive technology touch screens and capacitive technology touch screens. In fact, the working surface of resistive and capacitive technology touch screens is ITO coating.
B Nickel-gold coating, the outer conductive layer of the five-wire resistive touch screen uses a nickel-gold coating material with good ductility. Due to frequent touches, the purpose of using a nickel-gold material with good ductility is to extend the service life. However, the process cost is relatively high. Although the nickel-gold conductive layer has good ductility, it can only be used as a transparent conductor. It is not suitable for the working surface of a resistive touch screen because of its high conductivity and the metal is not easy to be very uniform in thickness, so it is not suitable for voltage distribution layer. , Can only be used as a probe.
