Why is the LCD screen wavy when a finger is touched?

Why do LCD screens often have ripples when you touch them?

To indicate the location on a map or identify a person in a photo for a friend, we often place our finger on a computer screen / laptop. At that point, you realize there are small ripples on the screen around your fingers.

If your desktop / laptop screen shows "ripples" when you touch your finger, it's definitely an LCD screen (liquid crystal display). Note that you won't notice this effect on CRT or LED screens. So where is this interesting phenomenon? Below is an explanation of ScienceABC, starting with understanding liquid crystals.

Liquid crystal

"Liquid crystal" is a term that refers to matter in a medium-sized solid state. This may sound a bit contrary to the knowledge that we have learned in high schools that matter exists in three basic forms: solid, liquid, and gas. In fact, liquid crystals are also a state of matter.

Therefore, "liquid crystals" share both the properties and characteristics of solids and liquids. Based on this principle, it has developed a liquid crystal display TV with a power consumption of only a fraction of the traditional screen.

Specifically, with a liquid crystal display (LCD), liquid crystals are sandwiched between two polarized glass panels (also known as substrates). Light from a fluorescent lamp will pass through the first glass and then the liquid crystal. These liquid crystals will adjust to allow light to pass through at different levels and then light approaches the second glass plate. The result of this process is what we see on the screen. display.

Note that the liquid crystals themselves do not emit light themselves, they are only responsible for controlling light and allowing light to pass or not by changing the way the liquid crystals are connected.

Pixel (pixel)

This term has become very popular in the digital age. A pixel (representing "an image element") is the smallest point on an image. The more pixels per unit area, the sharper and clearer the photo will look. Each pixel consists of 3 cells in red, blue and green. The electrical signals ensure that the liquid crystals in each cell will be bent and arranged in order to produce the desired color on the screen.

So why is the LCD screen (liquid crystal) wavy when we touch it?

We now know what liquid crystals are and how they display different colors on the screen. Let's go back to the first question: why is the screen wavy when I touch my finger?

Under normal conditions, particularly when your finger is placed on the mouse and not on the screen, the connection between the liquid crystals is normal and everything is fine (no ripple phenomenon ).

However, the moment you place your finger on the screen (to identify an object on the image for example), you will affect the bonding of the liquid crystals in the pixel. As a result, you will see ripples of round bridges forming around the finger's contact point on the screen. The deviation of the linkage between the liquid crystals in this case can make the color displayed on the screen no longer standard. But don't worry too much, when you take your finger off the screen, everything will be restored.

One thing to keep in mind is that it should not be frequently applied to the screen, especially using excessive force or sharp objects because it can permanently damage the screen image quality.