TFT-LCD touch screen

Working principle of resistive touch screen

The resistive touch screen is mainly controlled by pressure sensing. It consists of a display screen and a resistive thin film screen that closely fits the display screen. This resistive film screen is usually divided into two layers. One layer is a base layer made of glass or plexiglass, and its surface is coated with a transparent conductive layer; the base layer is pressed with a hardened and scratch-resistant plastic layer that we usually contact directly. There is also a conductive layer inside the plastic layer, and the two conductive layers are separated. When we touch the screen with a finger or other object, the two conductive layers come into contact, and the resistance changes. The controller judges the coordinates of the contact point and performs corresponding operations based on the specific change in resistance. This touch screen uses pressure sensing for 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 is coated with a layer of transparent oxide metal (transparent conductive Resistance) conductive layer, covered with a layer of hardened outer surface, smooth and scratch-resistant plastic layer, and its inner surface is also coated with a layer of coating, there are many small (less than 1/1000 inch) transparent between them The isolation point separates and insulates the two conductive layers. When the finger touches the screen, the two conductive layers are in contact at the touch point, the resistance changes, signals are 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), and then operates according to the way of simulating a mouse. This is the most basic principle of resistive technology touch screens.

Working principle of capacitive touch screen

Unlike resistive touch screens, capacitive touch screens use the current induction of the human body to work. The sensing screen of the capacitive touch screen is a four-layer composite glass screen. The inner surface and interlayer of the glass screen are each coated with a conductive layer, and the outermost layer is a thin protective layer of silica glass. When we touch the sensor screen with a finger, the electric field of the human body makes the finger and the surface of the touch screen 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. . This current 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. .

Compared with traditional resistive touch screens, capacitive touch screens have the following advantages:

1. Operation is novel. The capacitive touch screen supports multi-touch, the operation is more intuitive and interesting.

2. Not easy to touch by mistake. Since the capacitive touch screen needs to sense the current of the human body, only the human body can operate it, and it will not respond when touched with other objects, so the possibility of accidental touch is basically avoided.

3. High durability. Compared with resistive touch screens, capacitive touch screens have better performance in terms of dustproof, waterproof, and wear resistance.