Structure composition of capacitive touch screen

Basic structure:
The basic structure of a capacitive touch screen is: the substrate is a single-layer organic glass, and a transparent conductive film is uniformly forged on the inner and outer surfaces of the organic glass. A narrow electrode is tapered on the four corners of the transparent conductive film on the outer surface. The working principle is that when a finger touches a capacitive touch screen, a high-frequency signal is connected to the working surface. At this time, the finger forms a coupling capacitor with the working surface of the touch screen, which is equivalent to a conductor. Because there is a high-frequency signal on the working surface, when the finger touches, a small current is drawn away at the touch point. This small current flows out from the electrodes on the four corners of the touch screen, and the current flowing through the four electrodes is proportional to the straight-line distance from the finger to the four corners. The controller can calculate the coordinate value of the contact point by calculating the proportion of the four currents.
A capacitive touch screen can be simply seen as a screen body composed of four layers of composite screens: the outermost layer is a glass protective layer, followed by a conductive layer, the third layer is a non-conductive glass screen, and the innermost fourth layer is also a conductive layer. The innermost conductive layer is the shielding layer, which plays a role in shielding internal electrical signals. The middle conductive layer is a key part of the entire touch screen, with direct leads on the four corners or edges, responsible for detecting the position of touch points. 
The topmost covering layer is tempered glass or polyethylene terephthalate (PET). The advantage of PET is that the touch screen can be made thinner, and on the other hand, it is cheaper than existing plastic and glass materials. The insulation layer consists of glass (0.4-1mm), organic film (10-100um), adhesive, and air layer. The most important layer among them is the indium tin oxide (ITO) layer, which has a typical thickness of 50-100nm and a sheet resistance in the range of approximately 100-300 ohms. The three-dimensional structure of ITO technology has a significant impact on capacitive touch screens, as it directly relates to two important capacitance parameters of the touch screen: inductive capacitance (between the finger and the upper ITO layer) and parasitic capacitance (between the upper and lower ITO layers, and between the lower ITO layer and the panel screen).
The structure of capacitive touch screen mainly involves coating a transparent thin film layer on the glass screen, and then adding a protective glass on the conductor layer. The dual glass design can completely protect the conductor layer and sensor, and at the same time, it has higher light transmittance and better supports multi touch.
Capacitive touch screens are coated with narrow electrodes on all four sides of the touch screen, forming a low-voltage AC electric field inside the conductive body. When touching the screen, due to the human electric field, a coupling capacitance is formed between the finger and the conductor layer. The current emitted by the four electrodes flows towards the contact point, and the strength of the current is inversely proportional to the distance from the finger to the electrode. The controller located behind the touch screen will calculate the proportion and strength of the current, accurately calculating the position of the touch point. The dual glass of the capacitive touch screen not only protects the conductors and sensors, but also effectively prevents external environmental factors from affecting the touch screen. Even if the screen is contaminated with dirt, dust, or oil stains, the capacitive touch screen can still accurately calculate the touch position.
Due to the variation of capacitance with different contact areas and dielectric properties of the medium, its stability is poor and drift phenomena often occur. This type of touch screen is suitable for the debugging phase of system development.