As competition for smart devices becomes increasingly fierce. Many manufacturers hope to highlight themselves through differentiation of hardware and technology. Many times, when we have not yet understood new technologies, new technical concepts have emerged in the market, such as In-Cell, On-Cell and OGS full-fit technology, which are now popular in the touch market, let us learn about it together.
01 Screen structure
From the perspective of the screen structure, we can roughly divide the screen into three parts, from top to bottom, namely the protective glass, the touch screen, and the display screen. These three parts need to be fitted. Generally, two bonds are required, one bond between the protective glass and the touch screen, and the other bond is between the display screen and the touch screen. According to the fitting method, it can be divided into full fitting and frame sticking.
02 Box stickers
The so-called frame sticker is also called oral glue bonding, which means that the four sides of the touch screen and the display screen are simply fixed with double-sided tape. This is also the bonding method used by most display screens at present. Its advantage is that the process is simple and low-cost. However, because there is an air layer between the display screen and the touch screen, the display effect is greatly reduced after the light is refracted, which has become the biggest disadvantage of the frame sticker.
03 Fully fit
Full fit means using water glue or optical glue to completely stick the panel and the touch screen together in a seamless manner. Compared with frame stickers, it can provide better display effect. The most common fully fitted screens on the market are mainly OGS solutions dominated by the original touch screen manufacturers, as well as On Cell and In Cell technology solutions led by panel manufacturers.
Advantages of full fit: Full fit technology eliminates the air between the screen, which helps reduce the reflection between the display panel and the glass, which can make the screen look more transparent and enhance the display effect of the screen.
Another benefit of full fit technology is that the screen will never get dust again. The touch module also improves its strength due to its close integration with the panel. In addition, full fit can effectively reduce the interference caused by display panel noise to touch signals. Although the advantages of full fit are huge, the yield rate is relatively low. The consumption and scrapping of surface glass and even panels during the bonding process caused by poor yield will inevitably lead to an increase in costs. Therefore, the control of defoaming and bonding yield will become a more important factor than material cost.
Fully fit three screen technologies: In-Cell/On-Cell/OGS
01. In-Cell
In- Cell refers to the method of embedding the touch panel function into the liquid crystal pixel, that is, embedding the touch sensor function inside the display screen, which can make the screen thinner. At the same time, the In-Cell screen must also be embedded with a matching touch IC, otherwise it is easy to cause incorrect touch sensing signals or excessive noise. Therefore, for any display panel manufacturer, the threshold for entering In-Cell/On-Cell-style touch screen technology is indeed quite high, and it is still necessary to overcome the difficulty of low yield. Because once In-Cell is damaged, it will not only lose the touch screen, but also the display will be scrapped together, so manufacturers have higher requirements for In-Cell yield.
02. On-Cell
On Cell refers to the method of embedding a touch screen between the color filter substrate and the polarizer of the display screen, that is, installing a touch sensor on the liquid crystal panel, which is much less difficult than In Cell technology. Samsung, Hitachi, LG and other manufacturers are making rapid progress in On-Cell structural touch screens. At present, On Cell is mostly used in Samsung AMOLED panel products, and has not yet technically overcome the problems of color unevenness caused by thinning and touch control.
03. OGS /TOL
OGS technology integrates the touch screen with the protective glass, and plates the ITO conductive layer on the inner side of the protective glass, and directly coats and lithography on the protective glass. Due to the saving of a piece of glass and a single bond, the touch screen can be made thinner and cheaper. Currently, among domestic mobile phone brand manufacturers, such as Tianyu Bumblebee 1st generation, Gionee Fenghua and Xiaomi 2, have adopted OGS technology. However, OGS still faces problems of strength and processing cost. Since OGS protective glass and touch screen are integrated, it usually needs to be strengthened first, then coated, etched, and finally cut. This is very troublesome to cut on reinforced glass, with high cost and low yield, and it causes some capillary cracks to form along the edges of the glass, which reduces the strength of the glass. At present, insufficient strength has become an important factor restricting the development of OGS.
In the internal documents of some touch manufacturers, TOL (Touch On Lens) is used to express OGS, and the two are the same. Of course, there are other OGS-fully-fit screen structures, such as GG, GG2, GF, etc.