Consumers are demanding smartphones and other mobile devices to be as thin and lightweight as possible. The traditional structure of adding pro-cap touch to display to LCD, starts with separate LCD panel that is made up of two glass layers that contain liquid crystal material, top glass sheet covered with polarizer. Above that goes the pro-cap touch module. A protective cover glass is then placed on the top of touch panel so that the top electrodes are not exposed. This stacking up of the glass layer limited the designer from making slimmer and lighter displays.
A method that gaining momentum to solve this problem is “one-glass solution” (OGS). The basic idea is to replace the touch module glass by a thin layer of insulating material.
Sensor on Lens
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| Sensor on Lens |
One approach to achieve OGS is “sensor on lens”. In this case, ITO layer is deposited on the back of the cover glass and pattern it to create the electrodes. Thin layer of insulator added to the bottom of that and then second ITO layer is deposited on the back of that, patterning it to create electrodes running at right angles to the first layer. This module then laminated to standard LCD panel.
The touch technology deposited in the cover glass using the sensor on lens approach, results in a separate touch module that can be sold to the LCD display assemblers.
On-cell Pro-cap
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| On-cell Approach |
The other approach is called “on-cell” pro-cap. In this case, conductive layer of ITO is deposited directly onto the top of glass layer of LCD panel and then patterned into electrodes. A thin insulating layer is applied and then second ITO is deposited, electrodes patterned right angle to first layer. Finally top polarizing layer is applied on the top and display is completed by adding cover glass.
The on-cell enable LCD manufacturer to add these touch layers onto their own LCD panels during manufacturing process. The display assembler just have to purchase a cover glass to complete the display.
In-cell pro-cap
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| In-cell Approach |
Some of the panel makers developing “in-cell” touch panels, where one of the conductive layer actually shares the same layer as the thin film transistors (TFTs) used to switch the display’s sub pixels on and off. Tis approach not only reduces the electromagnetic noise in the system, but also uses a single integrated controller for both the display and the touch system. This reduces part counts and can make the display component thinner, lighter, more energy efficient and more reliable.
What are AMOLED Displays?
OLED display stack is somewhat different from a LCD stack. It only requires one substrate (glass) layer as opposed to LCD’s two. OLED material is much thinner than LCD layer. As a result, the finished display can be half as thick as an LCD panel, saving weight and thickness which is important in smartphone design. A number of smartphones today use a form of active-matrix OLED display called super AMOLED.
Other than above differences OLEDs have same stack configuration as that of LCDs and both tend to have cover glasses for protection.
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