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Introduction and Comparison of LCD Technologies



●The origin and advantages of full lamination screen technology


There are three types of full lamination screen technologies, namely In-Cell, On-Cell and One Glass Solutions, or OGS (G+G,G+F and G+FF). In a full lamination, the panel is fully bonded to the touch screen in a seamless manner using a water-based or optical adhesive. The other approach is bezel attachment which only attaches the touch panel to the bezel using adhesive.


At present, the common fully laminated screens in the market are mainly based on the OGS solutions dominated by the former touch screen manufacturers, and the On-Cell and In-Cell technology solutions dominated by panel manufacturers, in which the panel is fully bonded to the touch screen in a seamless manner using a water-based or optical adhesive. Full lamination offers a better display quality than bezel attachment.


By eliminating a layer of air between panels, the full lamination technology helps reduce reflection between the display panel and the cover glass, giving a more transparent appearance to the screen assembly. With the full lamination technology applied, reflection on an iMac is reduced by 75%. On top of the improvement in display quality, dust resistance and strength of the touch module due to its full bonding with the display panel, full lamination can also effectively reduce the touch signal interference caused by the display panel noise. It also simplifies the assembly process and brings assembly costs down.



●In-Cell technology is the ultimate OGS technology


It is safe to say that In-Cell is the ultimate direction of the OGS technology development. In-Cell refers to the method of integrating the touch panel function into the liquid crystal pixels, which is to embed the touch sensor function inside the display screen, enabling a thinner and lighter screen. However, due to the high hurdle for In-Cell technology, the yield rate was low in early production. Even with the robust efforts to integrate resources by top companies like Apple, iPhone 5 still faced insufficient production capacity for screens when it hit the market. As the technology matures today, screens adopting In-Cell technology have become more widely available.


When the touch panel component is outside the liquid crystal, light is reflected back and forth between the liquid crystal and the touch panel because they are never 100% bonded. Therefore, visibility of the screen is reduced to a certain extent when viewed under bright light. And because the light cannot be focused, the screen will also produce some blurriness when viewed from the side. As the touch panel is built-in, In-Cell technology enables a more reliable control of such problems. In-Cell technology offers the best display quality among the three technologies.


Compared with the other two technologies, the significant edge in screen thickness of the In-Cell technology has led to lighter and thinner products, which also benefit from a higher cutting efficiency of the glass substrate. In the future, screens adopting the In-Cell technology will become more dominant among high-end mobile phones.



●The principle of OGS technology:


OGS screens and In cell/On cell screens share the structure of protective cover lens + display panel that is lighter and thinner without an additional touch layer in between. The touch layer in the middle is the key to distinguish In cell/On cell screens and OGS screens.


In cell/On cell screens integrate the touch layer and the display panel, while OGS screens integrate protective cover lens and the touch layer.



●Principle and advantages of In-Cell technology:


The general principle of In-cell technology is to embed the touch layer on the liquid crystal pixel layer, enabling a thinner and lighter screen. A supporting touch driver IC has to be integrated into an In-cell screen, otherwise the touch functionality could be susceptible to wrong touch signals or excessive noise interference.




●Principle of On-Cell technology:


On-cell technology is a method of embedding a touch layer between the color filter and the polarizer, in which the touch sensor is bonded onto the LCD panel.






●A comparison of three lamination technologies: In-cell, On-cell and OGS




●Comparison of On-cell and In-cell touch technologies



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