Capacitive touch screens can be divided into two categories: surface type and projection type. The former is also called the analog capacity combination method, which forms a uniform electric field on the surface of the panel, and detects a weak current value that is inversely proportional to the distance from the four corners to the touch position. The conductive material is a transparent ITO film coated with antimony to form an AT0 conductive film with a resistance of 0.5? 2kfl. The surface of this conductive layer is covered with Yi 02 film. In order to prevent electromagnetic interference (EMI), the conductive layer inside generally uses an ITO film with a resistance of about 100 (1. In terms of reflectivity, it is higher than the resistance of the air layer in the middle. The performance of the touch screen is better, but the transmittance is not as good as that of the optical ultrasonic touch screen.
Projection type is also called projected capacitive combination type, which is a new type of capacitive touch screen. There are two methods: Grid and Wire Sensor. At present, the main focus is on the grid-type touch screen, which is mainly represented by iPhone and PRADA-phone. Both of them etch two conductive films through an insulator. The conductive film is a 100% ITO film. Like the formation of an electric field on the surface of the sensor, it is projected to the outside through a non-conductor such as glass or plastic. You can touch not only the surface of the sensor, but also the glass panel. Thick glass may cause parallax, but it can be solved by optical design.
Generally speaking, the projection type touch screen refers to the grid type touch screen. Because it has the characteristics of recording people, it has become the main projection type touch screen. The characteristics of multi-entry are
① Use your finger to switch the screen;
② Expand the thumb and index finger to enlarge the map;
③ Rotate the thumb and index finger in the clockwise direction to change the direction of the screen, etc., and operate with gestures.
Because the above operations can be input directly on the protective glass on the surface of the mobile phone, the design of the product is very simple.
Depending on the manufacturer of the sensor, the design is different. Currently 4in is the largest size. Compared with the resistance type, the price is very high. In addition, it can record people in words. Compared with the surface type, it is easier to solve the problem of electromagnetic interference. However, since the two etched surfaces overlap, a higher transmittance is required. Since high sensitivity is required, ITO film with lower surface resistance is required compared with resistive touch screens. It has the characteristics of high transmittance, low resistance, and balanced performance. On the other hand, the projection type is also called wire plastic, which detects the vertical and horizontal signals through a complex wire with a diameter of Φ between the glass and the glass or the film and the film. It can also detect the signal from 20mm glass, so it can be used as a large recording machine to stick on the small glass 11, and it can be used as an electronic signage. Table 54 shows the conductivity characteristics of the electro-muscular touch screen and the capacitive touch screen.
