In real life, we will come into contact with many electronic products, such as mobile phones, computers, smart watches and so on. We will find that most of these electronic products have displays, so how do these displays work? What is it made of? How does it work? Hope to answer our doubts in the following article.

What is LCD

First understand what is liquid crystal. Liquid crystal is an organic compound, which is between solid and liquid, and its molecular arrangement has regularity. Liquid crystal looks like a liquid in terms of form and appearance, but its crystal molecular structure shows a solid form, CH KO N-CH-O) OCH, within a certain temperature range, it can exhibit a variety of physical properties. It not only has mechanical properties such as liquid fluidity, viscosity, deformation, etc., but also has various physical properties such as crystal natural effect, optical multi-anisotropy, electro-optical effect and magneto-optical effect. It is a new type of substance called solid, liquid , The fourth state after the gas. It is because of its multiple properties that it has multiple physical properties, and it is gradually researched, developed and used by people.

2. The classification of liquid crystals

According to the different molecular structure arrangement, it can be divided into three kinds of clay-like Smectic liquid crystals, Nematic liquid crystals similar to thin matchsticks, and Cholestic liquids similar to cholesterol. Because the molecular structures of these three liquid crystals are different, their physical properties are not the same. The liquid crystals usually used in the manufacture of liquid crystal displays are Nematic liquid crystals, which are similar to fine matchsticks.

3. The internal structure of the LCD screen

The liquid crystal display is composed of two glass substrates with transparent electrodes (ITO). The plates are engraved with 90-degree alignment grooves, separated by 5um glass beads or plastic beads evenly, and then the liquid crystal is poured in . Due to the alignment groove, the liquid crystal molecules are forced to be twisted to 90 degrees, and two polarizers whose optical axes are perpendicular to each other are added to the glass substrate. The optical axis of the upper polarizer is parallel to the orientation of the liquid crystal of the substrate, and the optical axis of the lower polarizer Parallel to the liquid crystal orientation of the lower substrate. Since the liquid crystal itself cannot emit light, a light source must be installed behind the glass substrate, that is, a backlight plate with uniform light emission. The light we see on the image is the light emitted by the backlight plate. Generally speaking, the liquid crystal display is composed of four major parts: glass substrate, liquid crystal, polarizing plate and backlight plate.

4. The working principle of the LCD screen

We have introduced the basic structure of the LCD screen above, and then we will introduce how the LCD screen works. The liquid crystal in the liquid crystal layer is contained in a small cell structure. One or more cells constitute a pixel on the screen. There is a transparent electric plate between the glass substrate and the liquid crystal material. The electrodes are divided into rows and columns, in rows At the intersection of the column and the column, the rotation state of the liquid crystal molecules is changed by changing the voltage. The liquid crystal material acts like a small light valve. When no electric field is applied, the light passes through the first polarizer to become polarized light parallel to the orientation of the liquid crystal on the substrate. The polarized light is rotated 90 degrees by the liquid crystal layer and is exactly parallel to the optical axis of the polarized light of the lower substrate. At this time, the light can pass through. However, when the display screen is in a bright state, when an electric field is applied, the liquid crystal molecules will be aligned in the direction of the electric field. The original twisted arrangement becomes a vertical parallel arrangement. Polarized light does not interact with the vertically aligned liquid crystal layer. When the light reaches the polarizer at the exit end, The polarization axis is perpendicular to the polarization direction of the emitted light, and the light is blocked and cannot pass. At this time, the display screen is dark. If the applied electric field is not very strong, the liquid crystal molecules will be in a semi-rotating state. At this time, the light will only partially pass through the polarizing plate, and the display will appear in an intermediate state between light and dark. According to the above characteristics, we can pass Electric fields of different strengths are added to change the different degrees of rotation of the liquid crystal molecules, to change the strength of the light passing through, and finally to achieve images with different brightness at each point. This is the working principle of a monochromatic liquid crystal display.

With the development of science and technology, our lives are full of electronic smart products. We hope to better help us choose better technology products through our understanding of professional knowledge.