Capacitive touch screen classification

Capacitive touch screen classification

Surface capacitive touch screen

Surface capacitive touch screen technology uses ITO (Indium Tin Oxide, a transparent conductive material) conductive film to sense the touch behavior of the screen surface through an electric field induction method. But the surface capacitive touch screen has some limitations, it can only recognize one finger or one touch.

Projected capacitive touch screen

The projected capacitive touch screen is a sensor that uses the electrodes of the touch screen to emit electrostatic field lines. There are two types of capacitors generally used in projected capacitive sensing technology: self-capacitance and interactive capacitor.

(1) Self-capacitive

Self-capacitance, also known as absolute capacitance, is one of the most widely used methods. Self-capacitance usually refers to the capacitance formed by the scan electrode and ground. On the glass surface, there are horizontal and vertical scanning electrodes made of ITO. These electrodes and the ground form the two poles of a capacitor. When touched by hand or touch pen, a capacitor is connected in parallel to the circuit, so that the overall capacitance on the scan line is changed. When scanning, the control IC scans the vertical and horizontal electrodes sequentially, and determines the coordinate position of the touch point according to the capacitance change before and after the scan.

(2) Interactive capacitive

Mutual capacitance is also called span capacitance, which forms capacitance at the intersection of the horizontal and vertical ITO electrodes on the glass surface. The scanning method of interactive capacitance is to scan the capacitance change at each intersection to determine the position of the touch point. When touched, it will affect the coupling of adjacent electrodes, thereby changing the capacitance at the intersection. The scanning method of interactive capacitance can detect the capacitance value of each intersection and the capacitance change after touch, so it needs scanning Compared with the self-capacitance scanning method, the time is longer, and X*Y electrodes need to be scanned.

The difference between resistive screen and capacitive screen

①The resistive screen needs to be lightly touched and pressed when touching the mold, while the capacitive screen can be activated with a slight finger touch

②The resistive screen can be touched with any object, while the capacitive screen is the working principle of human body thermal induction, and can only be touched with the thermal area of the finger, nails and stylus are invalid. Since the area of the fingertip is much larger than that of a stylus, the touch accuracy of a capacitive screen mobile phone cannot be as high as a resistive screen when touching relatively small icons or menus.

③Capacitive screens can easily perform multi-touch, while resistive screens generally cannot achieve multi-touch.

④The inside of the resistive screen is soft, usually 4 to 5 layers of ultra-thin tempered glass are mixed with fine carbon particles (only visible under a microscope), and the touch screen circuit is connected by pressing the upper and lower carbon particles to contact each other. , Produce touch reaction, easy to produce scratches, easy to break, easy to touch screen is not working, and capacitive screens are made of single-layer thickened tempered glass, which has high hardness, wear resistance and long service life

⑤The resistive screen has poor visibility in the sun, while the capacitive screen is very good and has strong visibility in the sun.