LCD display related knowledge

Liquid crystal is the most widely used display at present. Liquid crystal display is divided into active and passive. The color high-resolution display is an active display, and segment LCD and Graphic LCD are both passive displays.


Brightness represents the amount of brightness of a screen per unit area. Specifically, the density of light passing through the normal direction of the display screen is expressed in units of (cd/m2) or nits.

contrast ratio

Contrast is the ratio of the transmittance in the state of displaying black to the transmittance in the state of displaying white. That is, the ratio of the two degrees of black to the brightness of white. The larger the value, the clearer the display and the easier it is to read.

Response time

Response time is the time required for the picture to change from white to black and from black to white. A slow response time can leave a “smear” of the image on moving parts of the frame. In practical applications, there is also the response time from gray scale to gray scale, which can better reflect the performance of the display screen.

The structure of LCD Display

the Structure of LCD

The structure of TFT substrate

The structure of TFT in liquid crystal display

The structure of CF substrate

The structure of color filter in liquid crystal display

     The glass substrate carrying active devices (thin film transistors) between the two glasses injected with liquid crystal material is called an array substrate, also known as an Array substrate. Polarizers are pasted on the upper and lower substrates to allow light with only one vibration direction to pass through, and a color filter (abbreviation: CF) is arranged between the upper polarizer and the array substrate. In addition, a backlight source and a driving circuit are mounted on the lower side of the array substrate. The current mainstream LCD uses amorphous silicon thin film transistor TFT-LCD and passive matrix display with nematic liquid crystal. Here, the former is called active drive LCD, and the latter is passive drive LCD.
      The upper part of the LCD display has a color filter substrate (CF substrate), and when the light passing through the array substrate passes through the CF substrate, it will be colored. In fact, a pixel of the LCD is divided into RGB 3 primary colors (red, green, blue). The combination of the three colors is called a pixel (PIXEL), and each pigment R, G, and B is called a sub-pixel. Color display uses color filters to mix RGB light to obtain various colors.

What is the difference between active display and passive display?

serial control LCD

     Common displays are divided into active displays and passive displays. TFT LCD and AMOLED are active displays. The display is complex and can display rich colors at high resolution. Usually it is an interface such as MCU/RGB/DVI/MIPI/LVDS, which requires a relatively strong processor to drive.
    Character LCD, Graphic LCD, Segment LCD and PMOLED are passive displays. Such displays are simple in structure and cannot achieve high resolution and large size. Usually, it can only display black and white. Generally, it is an MCU/RGB interface, which is difficult to drive. Simple and relatively cheap.
    There is a special product is the serial port control display, although it is an active display, but because of the integrated control board, the display content can be controlled by simple instructions, so that the processor with low driving ability can also control the active display

How color lcd produce color

The color of the color liquid crystal display is the light emitted by the backlight through the color filter and then synthesized light, controlling the proportion of different color light to obtain different colors. The light passing through the color filter not only changes color, but also the wavelength.
Measure the color coordinates of the red screen, green screen, and blue screen of the display screen, and then calculate, you can get the color gamut index. The color gamut is inversely proportional to the transmittance of the display, and the higher the color gamut, the more difficult it is for the display to achieve high brightness.

LCD Color Generation
Double chip is the wide viewing angle technology of LCD display
the picture of two domains

The difference between one domain and two domains

    Liquid crystal displays will have the problem of color deviation when viewing from a large viewing angle, because the liquid crystal molecules are rod-shaped, and the refraction of light at different angles is different. Double chips are designed to change this problem, where liquid crystal molecules within the same subpixel are arranged in two different directions and rotate in different directions when working, thus counteracting this bias due to different viewing angles.
     Another way to improve the problem of bias is to arrange the pixels of different rows at different angles, which can also have good results.

More Resources:

TFT LCD– Source: Wikipedia

mass-produced display products– Source:

Thin-film transistor– Source: Wikipedia

Liquid-crystal display– Source: Wikipedia

Frequently Asked Questions

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LCD is the abbreviation of liquid crystal display, the basic structure of LCD is injected in a vacuum environment in two glass substrates, one substrate glass with TFT (thin film transistor)

TFT’s is the abbreviation of thin film transistor, TFT alone can not display the content

TFT’s is the abbreviation for thin film transistor, the main structure of TFTLCD, each sub-pixel has a TFT to control whether the liquid crystal is charged

As the most widely used display, TFT LCD has shown that it is a good choice. It is thinner and lighter than CRT display, has a larger display area, is cheaper than AMOLED, and has a longer lifespan. The usual needs TFT LCD can meet, it can be your first choice

As a replacement for CRT monitors, TFT LCD has the characteristics of thinness and long life. At present, almost all mobile phones use TFT LCD. Using different technologies can make TFT LCD more eye-friendly, with a higher color gamut, and more energy-saving.

Using new technology, TFT LCD can achieve a response time of 2ms, which has met the requirements of game display. We can see that all kinds of video game competitions use TFT LCD

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