Basic structure The basic structure of capacitive touch screen is: The substrate is a single layer plexiglass, in the inner and outer surface of plexiglass are evenly forged on a layer of transparent conductive film, respectively, the outer surface of the transparent conductive film on the Four corners of the cone on a long narrow electrode. It works: When the finger touches the capacitive touch screen, in the face of high-frequency signal, at this time the finger and touch screen face form a coupling capacitor, which is equivalent to the conductor, because the work surface has high-frequency signal, finger touch in the touch point to suck a small current, this small current from the touch screen of the four corners of the electrode outflow,
The current of four electrodes is proportional to the line distance between the fingers and the four corners, and the contact point coordinates can be obtained by the calculation of the four current proportions of the controller. Capacitive touch screen can be simply seen as a four-layer composite screen composed of the screen body: the outermost is the glass layer, and then the conductive layer, the third layer is not conductive glass screen, the fourth layer is also conductive layer.
The most internal conductive layer is shielding layer, play the role of shielding the internal electrical signal, the middle of the conductive layer is the key part of the entire touch screen, Four corners or four sides have a direct lead, is responsible for the touch point position detection. The top covering layer is tempered glass or polyethylene terephthalate (PET). PET's advantage is that the touch screen can be thinner, on the other hand than the existing plastic and glass material cheaper. Insulating layer is glass (0.4~1mm), organic film (10~100um), adhesive, air layer. One of the most important layers is the indium tin oxide (ITO) layer, the typical thickness of Ito 50~100nm, and its square resistance is about 100~300 ohm range. The three-dimensional structure of ITO has a great influence on the capacitive touch screen, which is directly related to the 2 important capacitance parameters of the touchscreen: inductive capacitance (finger and upper ito) and parasitic capacitance (between the upper and lower Ito, the lower Ito and the display screen).capacitive touch screen is mainly constructed on the glass screen with a layer of transparent film body layer, in addition to the conductor layer with a protective glass, double glass design can completely protect the conductor layer and sensors, at the same time more light transmittance, but also better support multi-touch.Capacitive touch screen in the touch screen four sides are plated with a long narrow electrode, in the conductive body to form a low voltage AC electric field.
When touching the screen, because of the human electric field, the finger and the conductor layer will form
Capacitive touch screen into a coupled capacitor, the four edges of the electrodes emitted by the current will flow to the contact point, and the current strength and the distance between the finger to the electrode inversely proportional to the controller after the touch screen will calculate the proportion of the current and strength, accurately calculate the position of the touch point. Capacitive touch screen of double glass not only can protect the conductor and sensors, more effective to prevent external environmental factors on the touch screen, even if the screen stained with dirt, dust or grease, capacitive touch screen can still accurately calculate the position of touch. Because the capacitance varies with the contact area and dielectric of the medium, the stability of the capacitor is poor and the drift phenomenon often occurs. This kind of touch screen is suitable for the debugging stage of system development.