Three touch technologies of LCD capacitive touch screen: In-Cell/ On-Cell/ OGS

25 Jun 2024
Touch Panel Basics

Three touch technologies of LCD capacitive touch screen: In-Cell/ On-Cell/ OGS

LCD touch screen structure

The basic structure of ordinary LCD display touch screen can be divided into three layers: protective layer, touch layer and display layer. There will be an air layer between the general protective glass, touch layer and display panel after bonding, because most LCD touch screens use frame bonding technology, and there will be an air layer between the touch screen and the LCD display. The full bonding technology removes the air layer, thereby reducing the thickness of the screen. The screen reflection is greatly reduced, the screen is thinner and more transparent, and it is more completely black when the screen is turned off, and it is still clearly visible under strong light.

OGS/ On-Cell/ In-Cell touch technology for capacitive screens

OGS technology: OGS (one glass solution) is currently the main solution for fully laminated LCD capacitive touch screens. It integrates the touch layer and the protective layer glass together, coats the ITO (indium tin oxide) conductive layer on the inside of the protective glass, and directly coats and photolithographs the protective glass, thus saving a piece of glass and one lamination, making the LCD touch screen thinner and lighter, and reducing costs. However, since the OGS protective glass and the touch screen are integrated together, it usually needs to be strengthened first, then coated, etched, and finally cut. Cutting on the tempered glass is very troublesome, and some capillary cracks will form on the edge of the glass, which will reduce the strength of the glass.
In-cell technology: A method of embedding the touch panel function into the liquid crystal pixel, that is, embedding the touch sensor function inside the display screen. Incell places the ITO touch film under the upper glass substrate of the display panel and fuses it with the liquid crystal layer. The innovation of the In-cell touch panel is that the circuit is loaded on the liquid crystal, so that the LCD screen has the perception and touch input capabilities of the traditional touch screen. In-cell touch panel is not only more accurate, but also eliminates the need for a touch panel, making the entire touch screen thinner and lighter. Traditional touch screens are difficult to see clearly in the sun, but now that there is no touch panel, there is no parallax, and readability is improved.
On-Cell technology: refers to the solution of embedding the touch screen between the color filter substrate and the polarizer of the display screen, that is, equipping the LCD panel with a touch sensor. Its technical difficulty is simpler than Incell. It is currently mostly used in Samsung Amoled panel products. It has not yet overcome the problem of thinness and uneven color when touching.

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