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The Disadvantages Of TFT With Capacitive Touch

Blaze Display Technology Co., Ltd. | Updated: Nov 27, 2018

The transmittance and clarity of the capacitive touch screen is superior to that of the four-wire resistive screen, and of course it cannot be compared with the surface acoustic wave screen and the five-wire resistive screen. The capacitive screen is seriously reflective. Moreover, the four-layer composite touch screen of the capacitor technology has uneven light transmittance for each wavelength of light, and there is a problem of color distortion. Due to the reflection of light between layers, image characters are also blurred.

Current: The capacitive screen is used in principle as an electrode of a capacitor component. When a conductor is coupled to a capacitor with a sufficient amount of capacitance between the working surface of the ITO and the interlayer, the current flowing away is sufficient to cause the capacitive screen.

Although the capacitance value is inversely proportional to the distance between the poles, it is proportional to the relative area and is also related to the insulation coefficient of the medium. Therefore, when a large area of the palm or hand-held conductor is close to the capacitive screen instead of touching, it can cause the malfunction of the capacitive screen. In humid weather, this situation is particularly serious, holding the display and palms close to the display 7 cm. Within 15 cm of the display or the body close to the display can cause malfunction of the capacitive screen. Another disadvantage of capacitive screens is that they do not respond when touched with a gloved hand or a non-conductive object, because of the addition of a more insulating medium.

Drift: The main disadvantage of the capacitive screen is drift: when the ambient temperature and humidity change, the environmental electric field changes, causing the drift of the capacitive screen, resulting in inaccuracy. For example, if the temperature of the display rises after power on, it will cause drift: when the user touches the screen, the other hand or the side of the body will drift near the display; the larger object near the capacitive touch screen will drift after being moved, and if the user touches it, if someone touches it, it also causes drift; the drift of the capacitive screen belongs to the technical insufficiency. The environmental potential surface (including the user's body) is far away from the capacitive touch screen, but it is much larger than the finger area. They directly affect the touch position.

Others: In addition, in theory, many linear relationships should be nonlinear. For example, the total amount of current drawn by people with different body weights or different finger wetness is different, and the total current amount and the four currents are different. The change is a non-linear relationship. The custom polar coordinate system of the four corners used in the capacitive touch screen does not have an origin on the coordinates. After the drift, the controller cannot detect and recover, and after the four A/Ds are completed, four The calculation process of the value of the divided flow to the X, Y coordinate value of the touch point in the Cartesian coordinate system is complicated. Since there is no origin, the drift of the capacitive screen is cumulative and often requires calibration at the job site. The outermost bauxite protection glass of the capacitive touch screen is very scratch-resistant, but it is afraid of the nail or hard object knocking. If a small hole is knocked out, the interlayer ITO will be damaged, whether it hurts the interlayer ITO or the damage during installation and transportation. The inner surface of the ITO layer, the capacitive screen will not work properly.


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