Challenges thinner devices oled module

Now, that is frivolous fashion. Actively launch increasingly thin touchscreen devices, especially touch-screen phone, face a double problem: First, from the display coupled to the sensor noise increases; Second, the parasitic capacitance of the sensor to improve.
Display the generated noise relative to the charger noise is much lower in terms of strength, but the impact on the performance of a great touch because of its close distance of the touch sensor. Although the AMOLED display is very quiet (but more expensive than LCD), but most of these are on the market today higher ACVCOM noise and DCVCOM type LCD display. The common electrode VCOM of the display layer is the source of noise. Let us come back to discuss the equation (1), this is to determine the parallel plate capacitor touch sensor electrode and the display designated to receive arising between VCOM layer capacitor size. Here, area "A" is the entire custom lcd area of ​​the receiving electrode, the display cover the entire screen, therefore, the distance "d" is that the receiving electrodes and the distance between the layers VCOM.
Previously, touch screen device uses an air gap or shield to protect the screen from the touch sensor coupled to the receiving electrode noise impact. However, these solutions will increase the thickness and costs (4 inch screen shielding layer adds cost up to $ 1.00). Now, as the devices become increasingly thin, the air gap and the shield have been canceled, and the touch sensor using an optically transparent adhesive (OCA) is connected directly to the display. This causes the sensor closer to the receiving electrode VCOM higher noise level, so it will reduce the "d", to increase the capacitance and coupling more noise. Since OCA (dielectric constant of 3) replace the air gap (dielectric constant of a), therefore capacitance will be further improved. Slim-type product development trend is the next part or all of the touch sensor will need to be integrated in the display, which is the so-called in-cell (cell touch), On-cell (plug-touch). This integrated protocol stack will display the sensor closer to the display of the receiving electrode VCOM layer, thereby coupling more noise.
Slimmer shape product development The second problem is the parasitic capacitance touch sensor (CP) increases. In order to try to make the whole protocol stack becomes thinner, ITO substrate layer (made of glass or PET) require increasingly thin. This shortens the sensors transmit and receive the distance between the electrodes, thus increasing the capacitance. CP increases the scanning touch panel requires a longer charging and discharging, which reduces the maximum frequency of the scanning panel. The problem with this is that we want to scan at higher frequencies because of the higher frequency noise is usually small. In addition,low temperature lcd display scan times also mean increased power consumption and decreased refresh rate.