The surface capacitive touch screen has the three advantages of high precision, high durability and high sensitivity. In particular, the touch screen of a ticket vending machine terminal operated by many people is widely used because of its excellent durability. Unfortunately, it also has the following shortcomings, so it can only be used in restricted places.
(1) Like the above, the panel is almost made of a sheet of glass. It is used for small and medium-sized thin touch screens. The glass substrate is easily broken.
(2) In order to improve the optical characteristics, a thicker film such as an anti-glare film or a polarizer is attached. The capacitance change is small and the detection is impossible.
(3) The surface capacitive touch screen requires a separate circuit, and the entire unit is very expensive.
The internal capacitive touch screen solves these problems on the basis of taking full advantage of the three major advantages of surface capacitive touch screens, and is an upgraded version of surface capacitive touch screens. The basic detection principle is exactly the same as the usual surface capacitive type. It's just that a lot of work has been done in the detection circuit or data processing, and even small changes in capacitance can be detected stably.
The degree of freedom in the choice of substrate material is more extensive, and the ability to choose various materials becomes the advantage of this method. The materials used are not limited to glass, but films and plastics can also be used. And it doesn't matter if it is a film or a plastic plate or glass on the touch side. The transparent conductive film can be coated on the substrate side or on the touch control side. Of course, various transparent conductive films other than ITO can be used. The transparent conductive film becomes thinner inside, so it is called an "internal capacitive" touch screen.
In the case of a touch surface film, it can prevent the thin and light glass panel from breaking, and it can solve the above problem at one time.
The disadvantages of (1) and (2). In order to meet various structures, the internal capacitive touch screen has different performances depending on the structure. Shown below are the advantages of a low-priced touch screen formed on a 0.125mm anti-glare film/l.lmni thick general ITO glass.
(1) There is almost no internal reflection, the transmittance is very high, and there is almost no color change.
Transmittance (550nm) >92 percent
(Through low-reflection material and low-reflection treatment of the interface, the transmittance can be achieved above 98 percent )
(2) It is easy to suppress vertigo, ultra-low reflection and other optical design. Newton's ring does not occur on the structure.
(Can give full play to the performance of the functional film)
(3) Because there is no movable part, there will be no ITO leakage, and the durability is relatively high. The durability of keystrokes is >50 million times.
(The durability is so large that it can almost support the ITO inside the film is damaged, and it has almost permanent durability)
(4) High degree of freedom in panel design
It is possible to produce high water-resistant panels, corresponding to the narrow frame of the circuit unit.
Moreover, the internal capacitive touch screen can also correspond to a certain degree of gloved input. It can be used with surgical gloves or rubber gloves for clean rooms, and it can also be used stably for the input of cotton gloves. It has passed various reliability tests and is more suitable for car navigation and other equipment.
The inside of the capacitive touch screen is a five-wire resistive bottom electrode with a protective layer inside the panel, which is a very simple structure. Because there is no need to do a special film forming process, it can be easily produced with equipment for making resistive touch screens. In terms of materials, there is no need for circular spacers and expensive top electrodes, so the production cost is lower than that of ordinary resistors. Touch screen panel.
