What is LCD？

LCD stands for Liquid Crystal Display. Here are some facts about it:

1. Working Principle

The working principle of LCD is based on the optical anisotropy and electro-optical effect of liquid crystal. Liquid crystal molecules have special arrangement characteristics. Under the action of an electric field, the direction of their molecular arrangement will change, thus affecting the propagation of light.

Taking the common twisted nematic (TN) LCD as an example, when there is no electric field, the liquid crystal molecules are arranged in a twisted shape, which can rotate the polarization direction of polarized light by 90°, so that light can pass through the polarizer to reach the screen; when an electric field is applied, the liquid crystal molecules are arranged along the direction of the electric field, and the polarization direction of the light is no longer rotated. The light cannot pass through the polarizer, thereby realizing the brightness and darkness control of pixels, and displaying images by controlling the brightness and darkness combination of different pixels.

2. Structural composition

Liquid crystal layer: It is the core part of LCD, composed of liquid crystal molecules, responsible for controlling the transmission and blocking of light.

Glass substrate: It is used to fix and support the liquid crystal layer. Usually there is one above and one below, and transparent electrodes and other structures are also made on it.

Polarizer: Located on both sides of the liquid crystal layer, it only allows light polarized in a specific direction to pass through, and cooperates with the liquid crystal layer to achieve light control.

Color filter: For color LCD, color display is achieved through red, green, and blue filters. Each pixel consists of three sub-pixels (red, green, and blue).

Backlight: Provides light source for LCD, generally using cold cathode fluorescent lamps (CCFL) or light-emitting diodes (LEDs) to project light onto the liquid crystal layer.

3. Main types

TN-LCD: Twisted nematic liquid crystal display, which is the most common type of LCD, has the advantages of fast response speed and low cost, but the viewing angle is relatively narrow and the color performance is average. It is often used in early computer monitors and some devices with low display requirements.

IPS-LCD: In-plane switching liquid crystal display, with the advantages of wide viewing angle, high color reproduction, and stable image, it is currently widely used in smart phones, tablets, high-end monitors and other devices, but the response speed is relatively slow and the cost is high.

VA-LCD: vertically oriented liquid crystal display, with high contrast, good black display effect, and wide viewing angle, is widely used in some high-end TVs and professional monitors.

4. Performance parameters

Resolution: refers to the number of pixels on the screen, such as 1920×1080, 3840×2160, etc. The higher the resolution, the clearer the image.

Refresh rate: refers to the number of times the screen updates the image per second. Common ones are 60Hz, 120Hz, 144Hz, etc. The higher the refresh rate, the smoother the dynamic picture.

Contrast: refers to the brightness ratio between the brightest white and the darkest black displayed on the screen. The higher the contrast, the better the layering and color vividness of the image.

Response time: refers to the time required for liquid crystal molecules to change from one state to another, generally in milliseconds (ms). The shorter the response time, the less the ghosting phenomenon of dynamic pictures.

5. Application areas

Consumer electronic products: such as smart phones, tablets, laptops, LCD TVs, etc., are the main application areas of LCD, providing users with clear images and video displays.

Industrial control: Display screens used for industrial automation equipment, instrumentation, monitoring systems, etc. require high reliability and good stability.

Medical equipment: Such as medical monitors, ultrasonic diagnostic equipment, etc., have high requirements for display accuracy and color accuracy to help doctors accurately diagnose the disease.

Transportation field: Used in car dashboards, car navigation systems, traffic lights, etc., need to adapt to different environmental conditions and working requirements.