Liquid crystal displays (LCDs) use the unique properties of liquid crystals to control light and create images. Here's how they work:
-
Liquid Crystals: Liquid crystals are substances that have properties between those of liquids and solid crystals. They can flow like a liquid but have molecules that are organized like a crystal. This unique property allows them to be manipulated electrically.
-
Structure of an LCD: An LCD typically consists of several layers:
- Backlight: A source of light, often made from LED or fluorescent technology, which illuminates the display from behind.
- Polarizers: Two polarizing filters are placed on either side of the liquid crystal layer. Light can only pass through these filters if it vibrates in a specific direction.
- Liquid Crystal Layer: This layer is sandwiched between the polarizers and is composed of liquid crystal molecules. The orientation of these molecules can be changed by applying an electric field.
- Electrodes: Thin layers of conductive material (usually indium tin oxide) create a grid of electrodes on the glass layers attached to the liquid crystals.
-
Creating an Image:
- Light Passage: Light from the backlight passes through the first polarizer, which only allows light vibrating in a specific direction to pass through.
- Electric Field Application: Depending on the image being displayed, a voltage is applied to specific electrodes in the LCD. This voltage alters the orientation of the liquid crystal molecules.
- Modulation of Light: When an electric field is applied, the liquid crystals twist and change their ability to rotate the direction of the incoming light. If light passes through the liquid crystal layer, it will be affected by how the crystals are oriented (twisting or not twisting). This determines how much light can pass through the second polarizer.
- Second Polarizer: The angle of the light, after passing through the liquid crystal layer, determines whether it can pass through the second polarizer. Depending on the applied voltage and the corresponding liquid crystal orientation, varying amounts of light reach the viewer's eyes, creating different levels of brightness and colors.
-
Color Creation: In color LCDs, additional layers, including color filters (red, green, and blue), are incorporated. Each pixel is typically divided into three sub-pixels with these colors. By varying the voltage applied to each sub-pixel, different combinations of red, green, and blue light can be mixed, allowing the display to show a full spectrum of colors.
-
Refreshing the Image: The entire process happens rapidly as the display is refreshed many times per second, enabling smooth motion and dynamic images.
In summary, LCDs utilize the characteristics of liquid crystals to control light flow through precisely aligned layers and electrical input, creating the images we see on screen.