Why does it ripple when your hand presses the phone screen?

Why does the LCD screen appear ripples when pressed?

Because the mobile phone screen is a TN screen, pressing the screen will change the LCD distribution in the screen. This phenomenon can happen on all liquid crystal displays, such as the monochrome LCD screen on the calculator, LCD display, LCD TV, electronic watch, mobile phone, and so on.

These screens, already produced on a large scale, are low-cost, capturing most of the mobile phone market. However, its internal structure determines the disadvantages of monotonous display color, low viewing angle, and proneness to water lines (which have a great impact on the touch experience), so in the wave of the large-screen touch era, this technology has been gradually replaced.

LCD screens have a variety of arrangements, so they are called TN screens, IPS screens, and so on. Among them, the TN type is easy to produce water ripples, which is also the principle used by most soft screens.

Imagine that the liquid crystal is a long rod, which changes the inclination angle relative to the vertical direction to change the gray level. At this time, pressing with a certain amount of force will change the larger value of the inclination angle. At this time, looking at the legendary IPS hard screen, why is it not prone to water ripples? His liquid crystal arrangement is to change the inclination angle relative to the horizontal direction to change the gray scale. At this time, if you press a certain force in the vertical direction, the changed inclination has little effect. At the same time, the recovery speed of the liquid crystal in this arrangement is much faster than that of TN, so it is easy to return to normal quickly. It is emphasized that it is not mainly because of the hard screen; the glass is very hard, so it seems that water ripples are harder to appear when the glass is not pressed. But because of this liquid crystal arrangement, the direction of the electric field that controls the liquid crystal is different; IPS has this ability to use a hard glass screen, and the TN type cannot be used.

The principle of TN liquid crystal display is that the upper and lower glass plates are printed with circuit boards, and harder glass cannot be used. In IPS liquid crystal display, only the lower glass has a circuit to control, so the upper layer can be thick, thin, hard, or soft.