The Evolution and Applications of LCD Displays

LCD (Liquid Crystal Display)

Basic Definition

LCD is a display device that realizes color rendering by controlling light transmittance through liquid crystals. It leverages the unique properties of liquid crystal materials: by applying an electric current to rearrange liquid crystal molecules, it achieves image formation.

Development History

1888: Austrian botanist Friedrich Reinitzer discovered liquid crystal materials.
1968: Dr. G. Heilmeier from RCA Corporation discovered the dynamic scattering effect of liquid crystals, marking the dawn of the liquid crystal display era.
1971: The Twisted Nematic (TN) LCD mode was invented, laying the industrial foundation for mass production of liquid crystal displays.
1988: Sharp Corporation demonstrated the world’s first 14-inch active-matrix full-color display, propelling LCD technology into the full-color era.
After 2010: LCD emerged as the mainstream display technology globally. In 2021, China became the world’s largest LCD producer.

Working Principle

Core Structure

The key components of an LCD panel include a backlight source, lower polarizer, lower glass substrate, liquid crystal layer, upper glass substrate, and upper polarizer.

The backlight source emits white light as the primary light source for display.
The liquid crystal layer is the core functional material, whose molecular orientation can be altered by electric fields.
The upper and lower polarizers are oriented perpendicular to each other.

Display Mechanism

Without electric field: Liquid crystal molecules are arranged in a specific helical structure, which twists the polarization direction of light passing through the lower polarizer by 90°. This allows the light to pass through the upper polarizer, making the pixel appear bright.
With electric field: When voltage is applied, the long axes of liquid crystal molecules tend to align parallel to the direction of the electric field, losing their ability to twist polarized light. The light is blocked by the upper polarizer, making the pixel appear dark.
Grayscale and color display: By precisely adjusting the voltage amplitude, the twisting angle of liquid crystal molecules can be controlled to achieve graded light transmittance (grayscale display). Combined with red, green, and blue (RGB) color filters, full-color display is realized.

Product Classification

By Application and Display Content

Segment LCD: Used in digital meters and simple indicators, displaying fixed segments (e.g., numbers, icons).
Dot Matrix Character LCD: Built-in character libraries, suitable for displaying text content (e.g., calculators, small embedded devices).
Dot Matrix Graphic LCD: Supports flexible display of custom graphics and images, but requires more complex control circuits (e.g., monitors, mobile phone screens).

By Physical Structure

Common types include TN-LCD, STN-LCD (Super Twisted Nematic), DSTN-LCD (Double Super Twisted Nematic), and TFT-LCD (Thin-Film Transistor). Among them, TFT-LCD is the mainstream display technology, featuring wide viewing angles, a broad operating temperature range, and high display quality.

Application Scenarios

Benefiting from its advantages of small size, light weight, low power consumption, and low radiation, LCD is widely applied in consumer electronics such as televisions, computer monitors, laptops, tablets, and smartphones. It also plays an important role in industrial control systems, medical equipment, and automotive electronics.

Advantages

Compared with early Cathode Ray Tube (CRT) displays, LCD has prominent advantages: ultra-thin design, portability, low power consumption, low heat generation, long service life, and zero radiation.