In the production process of mobile phone screen, the protective glass, touch screen and display screen need to be fitted twice. If the frame is used, the display effect will be greatly reduced. If the full fitting rate is another problem. Because the protection glass, touch screen and display each after a joint production process, yield will be greatly reduced, if can reduce the number of joint, certainly will also increase the rate of joint, at present a few development direction: dominated by original touch screen manufacturers OGS scheme, and dominated by panel makers On-Cell and In-Cell In technical proposal.
At present, more powerful display panel manufacturers tend to promote on-cell or in-cell solutions, mainly because they have the production capacity of display screen, that is, they tend to make touch layer In the display screen; While the manufacturers of touch module or upstream materials tend to OGS, which is to make the touch layer on the protective glass, mainly because they have strong manufacturing capacity and technology. The common features of both can reduce the number of times of fitting, so as to achieve cost saving and improve the rate of good products of fitting. In addition, due to the lack of a touch layer, the material cost can be saved and the thinness can be realized. Among them, Apple iPhone5 adopts in-cell technology.
In-cell refers to a way to embed touch panel functionality into liquid crystal pixels, by embedding touch sensors inside the display to make the screen thinner and thinner. At the same time, the in-cell screen must be embedded with a touch IC, otherwise it will easily lead to wrong touch sensing signals or excessive noise. So for any panel maker, the barriers to entry for in-cell/on-cell touch screens are fairly high, and they still need to get past the low yield. Currently, in-cell technology is used In addition to Apple’s iPhone 5 and Nokia’s Lumia920. Among them, the thickness of iPhone5 screen is estimated to be 2.54mm, and in-cell thinning contributes 0.44mm, accounting for about 25% of the thickness reduction of 1.7mm. The iPhone5 lacks the touchscreen layer of the iPhone4S
Although the giant apple is currently pushing in-cell technology, it will be limited to high-end smart phones In the next few years. The main problem is the yield rate. Once in-cell is damaged, not only the touch screen will be lost, but also the display screen will be scrapped.
OGS technology is to integrate the touch screen with the protective glass, coating the ITO conductive layer on the inside of the protective glass, and directly coating and lithography on the protective glass. Due to the saving of a piece of glass and a single lamination, the touch screen can be made thinner and cheaper. At present, domestic mobile phone brand manufacturers such as Tianyu bumblebee 1 generation, Gionee fenghua, Xiaomi 2 have adopted OGS technology.
But OGS still faces issues of strength and processing costs. Since the OGS protective glass and touch screen are integrated, they usually need to be strengthened first, then coated, etched and cut.It is very troublesome to cut the reinforced glass in this way, with high cost and low yield, and some capillary cracks are formed at the edges of the glass, which reduce the strength of the glass. At present, the insufficient strength has become an important factor restricting the development of OGS.
On-Cell refers to the method of embedding the touch screen between the color filter substrate and the polarizer of the display screen, namely, the touch sensor On the LCD panel, which is much less difficult than In Cell technology. Samsung, Hitachi, LG and other manufacturers have made rapid progress in on-cell structure touch screen. At present, On Cell is mostly used in Samsung AMOLED panel products, but the technology has not been able to overcome the problem of color inequality caused by thin shape and touch.
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