Brief History and Working Principle of TFT LCD

Thin Film Transistor Liquid Crystal Display, often abbreviated as TFT-LCD, is a type of liquid crystal display that uses thin film transistor technology to improve image quality. Although TFT-LCD is collectively referred to as LCD, it is an active matrix LCD for televisions, flat panel displays, and projectors.

In short, a TFT-LCD panel can be seen as a layer of liquid crystal sandwiched between two glass substrates. The upper glass substrate is a color filter, and the lower glass is embedded with transistors. When the current passes through the transistor, the electric field changes, causing the liquid crystal molecule to deflect, thus changing the polarization state of light, and then using the polarizer to determine the light and dark state of the pixel. In addition, the upper glass is fitted with the color filter, so that each pixel contains three colors: red, blue, and green, which constitute the image on the panel.

●1957 – John Wallmark of RCA applied for a patent for thin film MOSFET.

●1992 – Paul K. Weimer of RCA developed Thin Film Transistor Technology (TFT) using Wallmark's patent.

●1968 – RCA's Bernard Lechner first implemented TFT technology in liquid crystal displays (LCDs).

●1971 – Lechner, FJ Marlowe, EO Nester, and J. Tults demonstrated a hybrid circuit driven 2 × 18 matrix display, using the dynamic scattering mode of LCD.

●1974 – Brody and Fang Chen Luo demonstrated the first planar active matrix liquid crystal display (AM LCD) using CdSe TFT.

●1975 – Brody coined the term "Active Matrix LCD".

●2020 – TFT LCD display technology now dominates the display market. In the past 20 years, it has eliminated the CRT (cathode ray tube) and plasma markets.

TFT liquid crystal display (thin film transistor liquid crystal display) technology has a sandwich structure, and liquid crystal materials are filled between two glass plates. Two polarization filters, color filters (RGB, red/green/blue), and two arrangement layers accurately determine the amount of light allowed to pass through and the color generated.

Each pixel in the active matrix is paired with a transistor, which includes a capacitor to enable each sub-pixel to retain its charge instead of sending it each time it needs to be changed. The TFT layer controls the optical flow, the color filter displays the color, and the top layer holds the visible screen.

The charge is used to make the liquid crystal material change its molecular structure, thus allowing various wavelengths of the backlight to "pass-through". The active matrix of the TFT display is constantly changing and rapidly changing or refreshing according to the input signal from the control device.

The pixels of a TFT display is determined by the color matrix and the underlying density (resolution) of the TFT layout. The more pixels, the more detail is available. The available screen size, power consumption, resolution, and interface (how to connect) define the TFT display.

The pixels of a TFT display is determined by the color matrix and the underlying density (resolution) of the TFT layout. The more pixels, the more detail is available. The available screen size, power consumption, resolution, and interface (how to connect) define the TFT display.

The TFT screen itself cannot emit OLED displays like this. It must be used with a bright white backlight to generate pictures. Newer panels use LED backlights (light-emitting diodes) to generate light, thus using less power and designing for less depth.

The TFT display module includes a TFT display screen, LED backlight, and drive circuit.

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