LCD (Liquid Crystal Display) is to place liquid crystal between two pieces of glass, and control the liquid crystal molecules to produce a picture. The LCD panel itself does not emit light and needs to rely on the backlight to provide light. By changing the arrangement of liquid crystal molecules, the white light emitted by the backlight source is controlled to generate a picture.
How do LCDs (liquid crystal displays) work?
First, you need a light source.
The part that provides light to the LCD screen is the backlight panel, which appears to be a panel that emits white light evenly. Why is it white light? Because white light contains all colors of light, we can process it with liquid crystals to obtain light of different colors and brightness. Just having white light is not enough, we also need it to have a uniform direction. Cover the backlight with a polarizer to unify the direction of the light. Now we have uniform and white light.
Turn white light into a picture
What I have now is just a white screen, how to make it display brilliant pictures? We cover a layer of liquid crystal on the backlight module, let the light pass through the liquid crystal, and control the light by controlling the liquid crystal.
Liquid crystal looks like a liquid from its shape and appearance, but its crystalline molecular structure shows a solid state. Like metals in a magnetic field, their molecules are precisely ordered when subjected to an external electric field. A pair of electrode plates are added on both sides of the liquid crystal layer, and the degree of distortion of the arrangement of the liquid crystal molecules is controlled by controlling the voltage to control the light.
Finally, a second layer of polarizer is covered on the liquid crystal layer. The light that is correctly processed by the liquid crystal can present the picture we see through the polarizer.
What is Liquid Crystal?
Crystals refer to substances that exhibit a certain regular structure in spatial arrangement. A liquid state is a substance that exhibits an amorphous state when the thermodynamic temperature is higher than its intermolecular interaction force. Since it cannot maintain a stable structure, its composition is naturally irregular.
After some substances are in the molten state or dissolved by a solvent, although they lose the rigidity of solid substances, they gain the easy fluidity of liquids, and retain the anisotropic orderly arrangement of some crystalline substances, forming a kind of both crystals. The intermediate state of some properties of liquid and liquid has amorphous properties on the macroscopic level, but there are certain rules on the microscopic arrangement. The orientation-ordered fluid that exists during the transition from solid state to liquid state is called liquid crystal.
From a microscopic observation, a molecule has six degrees of freedom, including three rotational degrees of freedom and three translational degrees of freedom. Its translational freedom is continuously opened in the process of temperature rise, which destroys the spatial order, then its order is mainly contributed by the rotational degree of freedom. Liquid crystal is a material that loses a certain spatial order (positional order) and retains its orientation (orientational order).
Under the action of the power plant, the arrangement of the liquid crystal molecules changes, which affects the light passing through the liquid crystal. This changed light shows changes in brightness and darkness after passing through the polarizer. Accordingly, the purpose of controlling the light can be achieved by controlling the electric field.
color display
If you want to display a colorful picture, you also need a color filter. A pixel consists of 3 liquid crystal cells, each with red, green and blue color filters. In this way, all colors can be displayed through the combination of the three primary colors.
What is Polarizer?
The liquid crystal itself does not emit light, and the backlight provides the light source for the display of the liquid crystal screen, but the polarization direction of the light sent out is inconsistent and radial. If such light passes through the twisting of the liquid crystal molecules, what we see on the screen may be a white piece. , or irregular color blocks. Both the upper glass and the lower glass should be attached with polarizers, but pay attention to the direction. If the lower polarizer filters the light in the X direction, the upper layer can only filter the light in the Y direction. If the upper and lower layers are in the same direction, nothing can be seen.When the backlight source passes through the incident polarizer, only the light whose vibration direction is the same as the polarization axis of the incident polarizer remains. The polarized light passes through the liquid crystal layer and then is emitted by the polarizer.