The manufacturing process of the touch screen is similar to the manufacturing process of the liquid crystal display panel in many places. In both cases, transparent electrodes are formed on two opposing substrates, and then functional materials are printed on the transparent electrodes to form a pattern, and then the upper and lower substrates are bonded together and transferred to the final process.
Most of the touch screen manufacturers directly purchase the substrates with transparent electrodes formed, and apply them to the company's manufacturing process. The lower glass substrates invested are mainly the second-generation liquid crystal display panels with a size of 370_ x 470mm or 400mm x 500mm; the upper film substrate Directly purchase 650mm or 1000mm roll film, then cut it according to the appropriate size and put it into the subsequent manufacturing process.
The transparent electrode pattern making method is different from that of the liquid crystal display panel. Liquid crystal display panels use photolithography to form transparent electrode patterns, which require resin materials with good photosensitivity and expensive exposure and development equipment. There are mainly the following methods for making transparent electrodes on touch screens.
① Print the photosensitive material on the position of the transparent electrode of the product, and use it as a mask to etch away the unnecessary part of the transparent electrode.
② Insulating film is printed where transparent electrodes are not needed.
③ Design and make transparent electrodes with laser.
Compared with the LCD panel, the pattern of the transparent electrode of the touch screen is very simple. Since expensive photolithography processes are not required, various manufacturers choose low-cost manufacturing methods as much as possible to form transparent pixel electrodes. In the past, methods ①, method ②, or the use of light to make transparent pixel electrodes were mostly used. Recently, the methods of using laser processing to form transparent electrodes have gradually increased.
Although laser processing equipment is not cheap, it requires less space. In addition, the laser processing method is realized by a dry process, no wet etching process is required, and waste liquid treatment is omitted, which is very effective for the processing of ITO thin films. Its representative equipment manufacturer is Ultech.
After the transparent pixel electrode pattern is formed, silver glue is printed on each substrate, and then a circular spacer is set on one side of the substrate, and then the two substrates are bonded together. The bonding method of the two substrates is the same as that of the liquid crystal display panel. Some first print the frame sealant, and then use heating or UV irradiation to cure the frame sealant, and some use double-sided adhesives and other adhesives for bonding.
After completing the bonding of the two substrates, the FPC is then strongly bonded. The liquid crystal display is laminated in a state of so-called molher glass. However, TP is often sized first, and then attached to the panel of the set size.
capacitive (projection type) touch screen, only one glass substrate is used. The difference from the resistive touch screen process is that the coating and patterning process is repeated on a glass substrate. This is the technical focus of the capacitive touch screen manufacturing process.
