Difference between resistance and capacitive touch screen

Capacitive touch screen and traditional resistive touch screenDifferences. When a resistive touch screen is working, only one touch point can be judged at a time. If there are more than two touch points, no correct judgment can be made, therefore, the resistive touch screen is only applicable to the judgment of some simple actions such as click and drag. The multi-touch of capacitive touch screen can divide users' touch into two tasks: collecting multi-point signals and determining the meaning of signals to complete the judgment of complex operations.

Using the stretching and transposition of two fingers, you can perform interesting operations such as amplification and rotation on the screen, which was almost unimaginable before the appearance of the capacitive touch screen. After Apple's iPhone went public, it soon became a touch trend. Soon, Apple followed suit and launched an iPod Touch that also supports multi-touch (which is actually equivalent to a simplified version of the iPhone ), it is also sought after by users and media.

The success of Apple's two products stimulated other IT vendors. Samsung has been committed to portable digital audio and video product market, but also the first follow-up, launched its own first multi-touch products-YP-P2, in the portable digital audio and video market has made a great response.

Relatively speaking, Chinese manufacturers have slowed down in the follow-up of capacitive touch screen products until the launch of the t50. However, due to the gap in manufacturing technology and technology, the sensitivity and operation sensitivity of capacitive touch screen Products in China are slightly different from those of foreign manufacturers.

In fact, the implementation principle of the touch screen is roughly the same, and transparent touch panels are added to the ordinary LCD screen. What we call Resistance Type and Capacitive Type is divided according to their working principle. Currently, there are four types of touch screens: resistance, Capacitive, infrared, and surface acoustic. In our real life, we have the most contact with the resistive touch screen, which has been widely used in mobile phones and portable digital products.

Working principle of resistive touch screen

Before analyzing the working principle of capacitive touch screen, let's take a look at the working principle of the resistive touch screen.

The resistive touch screen is mainly controlled by pressure sensing. It consists of a display screen and a resistor film screen closely attached to the display screen. This resistor film screen is usually divided into two layers, one layer is composed of glass or organic glass base layer, its surface is transparent conductive layer; the base layer is pressed against the hardened and scratch-proof plastic layer that we normally access. The plastic layer also has a conductive layer, which is separated between the two conductive layers. When we touch the screen with our fingers or other objects, the two conductive layers are in contact and the resistance changes. The Controller determines the coordinates of the contact points based on the specific changes in the Resistance and performs corresponding operations.

Working principle of capacitive touch screen

Unlike the resistive touch screen, capacitive touch screen uses the current sensing of the human body to work. The sensor screen of capacitive touch screen is a layer-4 composite glass screen. The inner surface and interlayer of the glass screen are coated with a conductive layer, and the outermost layer is a thin layer of silicon Earth glass protective layer. When we touch the sensor screen with our fingers, the electric field of the human body forms a coupling capacitor between the finger and the surface of the touch screen. for high-frequency current, the capacitor is a direct conductor, so the finger sucked a small current from the contact point. The current flows out of the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the distance from the fingers to the four corners. The controller accurately calculates the ratio of the four currents, obtains the position of the touch point.

Compared with the traditional resistive touch screen, capacitive touch screen has the following advantages:

1. novelty. Capacitive touch screens support multi-touch, making operations more intuitive and interesting.

2. It is not easy to touch by mistake. Because the capacitive touch screen needs to sense the current of the human body, only the human body can operate on it. When it is touched by other objects, it does not correspond, so it basically avoids the possibility of false touch.

3. high durability. Compared with the resistive touch screen, capacitive touch screen has better performance in dust, water resistance, wear resistance and other aspects.

As a red touch screen technology, capacitive touch screen has the following advantages, including gorgeous interface, multi-touch, and only human body sensing:

1. low precision. Due to technical reasons, the accuracy of capacitive touch screen is still less than that of resistive touch screen. In addition, you can only use your fingers for input. It is difficult to recognize complicated handwritten input on a small screen.

2. Easy to be affected by the environment. When environmental factors such as temperature and humidity change, the capacitive touch screen may be unstable or even drifting. For example, when a user moves his or her body closer to the screen, it may cause drift, even in a crowded crowd. This is mainly due to the working principle of capacitive touch screen technology. Although the user's fingers are closer to the screen, there are still many electric fields near the screen that are much larger than the fingers at the same time, this will affect the judgment of the touch position.

3. high costs. In addition, the current capacitive touch screen is attached to the touchpadLCDThere are still some technical difficulties in the panel step, the yield rate is not high, so the cost of capacitive touch screen is also increased virtually.

Outlook

In the past, due to cost and technology, the use of resistive control panels far exceeds the capacitive touch technology. However, in the last phase, the price of capacitive touch screens is declining with technological advances and batch processing, and the price gap with the resistive touch screens is also getting smaller and smaller, in terms of price, we gradually have the ability to compete with the resistive touch screen.

With the popularity of Apple's iPhone, iPod Touch and other products, not only have major manufacturers started research and development on capacitive touch screen products, but even many touch screen manufacturers such as 3 m and synaptics have followed up in large numbers, they have invested in the R & D and production of capacitive touch screens. I believe that with the continuous upgrade of competition, capacitive touch screens will be greatly developed in the short term. The application of capacitive touch screens will not only be applied to existing mobile phones, portable audio and video players, it may also expand to more products such as cameras, GPS navigators, and game consoles.

Finally, we should say that although capacitive touch screen has its unique selling point, it is not enough to replace the deep-rooted position of the resistive touch screen in terms of its comprehensive functionality and stability. In a certain period of time, we believe that these two types of touch screens will be more competitive in the market. It's too early to tell who the deer is dead.

From technical principlesDifferencesTouch screen, which 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
. Among them, the touch screen of vector pressure sensing technology has withdrawn from the historical stage. The touch screen of infrared technology is inexpensive, but its outer frame is fragile, which may easily produce light interference and distortion in the case of curved surface. The design concept of capacitive touch screen is reasonable, however, the problem of image distortion is hard to be fundamentally solved. The screen positioning of the Resistance Technology is accurate, but its price is quite high, and it is afraid of scratch. The surface acoustic touch screen solves various defects of the touch screen in the past, clear is not easy to be damaged, suitable for various occasions, the disadvantage is that if there is water drops and dust on the screen surface will make the touch screen become dull, or even do not work. The touch screen is divided into four types based on the working principle of the touch screen and the media for transmitting information. They are resistance type, infrared type, capacitive inductive type and Surface Acoustic type, respectively,
According to the working principle of the touch screen and the media for transmitting information, we divide the touch screen into four types: resistance, Capacitive induction, infrared, and surface acoustic. Each type of touch screen has its own advantages and disadvantages. The key to understanding that type of touch screen is to understand the working principle and characteristics of each type of touch screen technology. Next we will give a brief introduction to the various types of touch screens mentioned above:
1. resistive touch screen (Working Principle of resistive touch screen)
This touch screen uses pressure sensing for control. The main part of the resistive touch screen is a thin screen that is very compatible with the display surface. This is a multilayer composite film that uses a glass or hard plastic tablet as the base layer, the surface is coated with a transparent oxide metal (transparent conductive resistance) conductive layer, the above is covered with a layer of outer surface hardening, smooth and non-erasable plastic layer, its internal surface is also coated with a layer of coating, there are many small between them (less than 1/1000 inch) the transparent isolation points are separated by two conductive layers. When the fingers touch the screen, the two layers of conductive layer have contact at the touch point position, the resistance changes, generate a signal in both the X and Y directions, and then send the touch screen controller. The controller detects this contact and calculates the position (x, y), and then operates based on the simulated mouse. This is the most basic principle of the Resistance Technology touch screen. The key of the Resistance touch screen lies in the material technology. The commonly used transparent conductive coating materials include:
A, Ito, indium oxide, weak conductive body, characteristic is that when the thickness drops below 1800 (ER = 10-10 meters) will suddenly become transparent, light transmittance is 80%, the light transmittance drops, and the thickness of the device increases to 300. Ito is the main material used by the touch screen and capacitive touch screen of all resistor technology. In fact, the working face of the touch screen of resistor and Capacitive technology is Ito coating.
B. Nickel-gold coating, V.LineThe outer conductive layer of the resistive touch screen uses the nickel-Gold Coating Material with good ductility. because of frequent touch of the outer conductive layer, the purpose of using the nickel-gold material with good ductility is to prolong the service life, but 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 face of the resistive touch screen because of its high conductivity, and the metal is not easy to achieve very even thickness. It is not suitable for the voltage distribution layer, it can only be used as a probe layer.

1. resistive touch screen

① They are a completely isolated work environment, not afraid of dust, water vapor and oil pollution
② It can be touched by any object and used for writing and painting. This is their great advantage.
③ The accuracy of the resistive touch screen only depends on the accuracy of A/D conversion, so it can easily reach 4096*4096 • comparison, fiveLineResistance ratio 4LineResistance is superior in resolution accuracy, but the cost is high, so the price is very high.
1.1 IVLineResistance Screen
ThuLineWhen two transparent metal layers of resistance analog technology work, each layer adds a constant voltage of 5 V: a vertical direction, a horizontal direction. A total of four cables are required. Features: High Resolution, high-speed transmission response. Surface Hardness treatment to reduce scratches, scratches and prevent chemical treatment. With smooth and fog surface processing. One correction, high stability, never drifting.
1.2LineResistance Screen
V.LineThe base layer of the Resistance Technology touch screen adds the Voltage Fields in both directions to the conductive working surface of the glass through the precision resistance network, we can simply understand that the voltage field in two directions is added to the same working surface, while the outer nickel-gold conductive layer is only used as a pure conductor, the position of the touch point is measured by the X-axis and Y-axis voltage values of the inner Ito contact points after touch. V.LineFour leads are required for the ITO layer of the resistive touch screen, and only one conductor is used for the outer layer.LineTotal5. Features: High Resolution, high-speed transmission response. High surface hardness, reduce scratches, scratches and prevent chemical treatment. The same point can still be used for 30 million times. Conductive Glass is the substrate medium. One correction, high stability, never drifting. V.LineResistive touch screen features high price and high environmental requirements
1. 3 Limitations of the Resistance Screen
Whether it's fourLineResistor touch screen or fiveLineResistance touch screen, they are a completely isolated working environment, not afraid of dust and water vapor, it can be touched by any object, can be used to write and draw, it is suitable for industrial control and office space limited people. The common disadvantage of the resistive touch screen is that the outer layer of the composite film uses plastic materials. People who do not know it are too hard or the use of acute touch may scratch the entire touch screen and lead to decommission. However, within the limits, scratch will only hurt the external conductive layer, the scratch of the external conductive layer for fiveLineIt does not matter for the resistive touch screen, but for the fourLineThe resistive touch screen is fatal.

2. capacitive touch screen

2.1 capacitive technology Touch Screen
It uses the current sensing of the human body to work. Capacitive touch screen is a layer-4 composite glass screen. The inner surface of the glass screen and the interlayer are coated with an ITO layer. The outermost layer is a layer of glass protection layer, and the interlayer Ito coating is used as the working face, four electrodes are extracted from the four corners, and the inner ITO layer is a shielding layer to ensure a good working environment. When the finger is touched on the metal layer, due to the human 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 sucked a small current from the contact point. The current flows out of the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the distance from the fingers to the four corners. The controller accurately calculates the ratio of the four currents, obtains the position of the touch point.
2.2 capacitive touch screen Defects
Capacitive touch screen with better light transmittance and definitionLineResistance screen, of course, not with the surface acoustic screen and fiveLineResistance screen compared. The capacitive screen is highly reflective. In addition, the four-layer composite touch screen of Capacitive technology has uneven light transmittance of various wavelengths, which causes color distortion. Due to the reflection of light between layers, it also causes blurred image characters. In principle, the capacitive screen uses the human body as an electrode of a capacitor element. When there is a conductor close to the interlayer Ito working face and a sufficient amount of capacitance is coupled, the current is enough to lead to the misoperation of the capacitive screen. We know that although the capacitance value is inversely proportional to the distance between Poles, It is proportional to the relative area and also related to the insulation coefficient of the medium. Therefore, when a large area of palm or handheld conductor is close to the capacitive screen rather than the touch, it can lead to the incorrect action of the capacitive screen. in wet weather, this situation is particularly serious, if you hold the monitor in your hand and the palm is close to the monitor within 7 cm or the body is close to the monitor within 15 cm, the screen may be mistakenly operated. Another disadvantage of the capacitive screen is that it does not respond when a gloved hand or an object without conductive hand is touched, because it adds more insulating media. The main drawback of the capacitive screen is drift: when the ambient temperature and humidity change, the Environmental electric field changes, it will cause the drift of the capacitive screen, resulting in inaccuracy. For example, when the screen is turned on, the temperature of the monitor increases, causing drift: when the user touches the screen, the other hand or one side of the body is close to the monitor, and large objects near the capacitive touch screen are moved back to drift, when you touch the screen, if someone comes around to watch it, it will also cause drift. The reason for the capacitive screen drift is the inherent technical deficiency, the environmental potential surface (including the user's body) although far away from capacitive touch screens, they are much larger than the finger area, and they directly affect the determination of the touch position. In addition, theoretically manyLineThe relationship is actually notLineFor example, the total electric traffic consumed by people with different weights or different degree of moisture on their fingers is different, while the changes in the total electric traffic and the changes in the four electric traffic are notLineThe capacitive touch screen uses the four-angle custom polar coordinate system without the origin of the coordinates. After the drift, the controller cannot detect and recover, after the four A/D operations are completed, the calculation process from the four traffic separation values to the X and Y coordinate values of the touch points in the Cartesian coordinate system is complex. Because there is no origin, the drift of the capacitive screen is cumulative, and calibration is often required at the work site. The outermost protection glass of capacitive touch screen has good anti-scratch performance. However, if you are afraid of hitting your nails or hard objects, hitting a small hole will hurt the interlayer Ito, whether it is damage and interlayer Ito or damage the inner surface ITO layer during installation and transportation, the capacitive screen will not work normally.