Weiluntong touch screen - the internal structure of the resistive touch screen

(1) FILM - that is, the film used for touch, the base material is PET. When touched, the ITO of the upper and lower layers is brought into contact by deforming the film, resulting in different "resistance values" in the X and Y axes (similar to the principle of moving rheostats).

According to the different requirements of use, the surface of FILM is divided into two types: bright surface (smooth surface) and matte surface (blurred surface), similar to the difference between ordinary glass and ground glass. The bright surface is generally widely used in small-sized consumer electronics, the main advantage is that the surface is smooth, high light transmittance, and has obvious advantages in appearance and viewing, the advantage of matte surface is that there is no reflection, no Newton ring, and it is not easy to cause visual fatigue when viewing for a long time.

Because the touch screen is generally used for writing and touching, the surface hardness of FILM is generally required to reach the standard of 3H to prevent friction and scratching.

(2) ITO film - the abbreviation of Indium Tin Oxide, it is a conductive film. Extremely fine, it is done on film and glass by means of a "sputtering" (similar and spraying) process. The "linearity" of the touch screen is largely determined by the uniformity of the film. In particular, the film itself is a retractable part, and the uniformity of the ITO film on its surface is even more important.

(3) Glass - on the one hand, it plays a bearing role to carry the operating pressure and prevent the deformation of the whole finished product. On the other hand, the surface of the film is coated with ITO film, which works together with the film to complete the "touch function".

(4) Partition point - is a kind of insulating glue substance, the diameter is generally 0.03-0.05. The partition point is attached to the glass by the method of "silk screen printing", and the distance between it and the above film is 0.05-0.07. Its function is to prevent malfunction and accuracy of the touch action, and the size of the separation point can also be used to adjust the amount of the operating force when touching.

(5) Silver wire - used to conduct current signals, it is also printed on FILM and glass through the method of "silk screen printing".

(6) Insulating glue - used to prevent the short circuit of the upper and lower silver wires, and also to make the FILM suspended on the glass "support frame", the total thickness is about 0.10mm.

(7) Adhesive glue - it is used to bond the upper and lower layers into one.

(8) Transparent oil - its function is to adjust the range of non-action area, on the one hand, it can appropriately expand the view area (according to the customer's requirements for the view area), and on the other hand, it can prevent malfunction.

(9) FPC cable - connect the touch screen with the motherboard to complete the signal transmission (see the figure below). The definition of FPC mainly includes four aspects: the shape of the FPC, the number of pins and contact surfaces of the FPC (front or back), and the thickness of the stiffener of the FPC.

(10) Touch screen shape - the specifications and dimensions of the touch screen, including length, width and thickness. At present, there are two kinds of thickness of touch screen on the market: 1.0mm and 1.4mm, because the glass of touch screen is currently widely used 0.70mm and 1.10mm thickness.

The length and width of the touch screen generally refer to the size of the glass (rigid body), and the factory produces it with the maximum tolerance size during processing, which is mainly due to the processing process and machining accuracy (final cutting of the glass) and the "edge loss" factor of the glass.

When designing, the external dimensions are generally determined according to the shape of the TFT LCD, which is mainly a simplification for easy installation and positioning. Generally, different TFT LCDs correspond to a touch screen alone, if the size of the LCD is very small, the touch screen can be shared and shared, and the TFT LCD should be positioned differently.

(11) Viewable area - an area where the line of sight is not obstructed. Out of sight is the area where the line of sight is not "penetrable". Therefore, the "viewport" should be larger than the display cover window to avoid the image being obscured by the touchscreen.

How to determine the viewing area: The viewing area of the touch screen is determined according to the size of the window area of the face cover. First, according to the image effective area of TFT LCD, the size of the cover window is determined by unilaterally reducing 0.5mm-1.5mm, and then unilaterally expanding the cover window area by 0.5mm-1mm (according to the actual condition of the structure) as the viewing area of the touch screen.

(12) Non-action area - there will be no operation response to touch in this area, this area is mainly used to prevent misoperation of the process area, not the part required for product function.

(13) Action area - is the area used when carrying out touch operation, and all operations in this area must have an operation response. It is the functional area of the touch screen and is the most important area in the design.

(14) Cover window area - this area will not be reflected in the official design drawing of the touch screen, but it is an important basis for determining the visual area/non-action area/action area (see the method of determining the visual area above) to prevent malfunction caused by the surface cover.

Weiluntong touch screen - the internal structure of the resistive touch screen

Weiluntong touch screen - the internal structure of the resistive touch screen

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