What is a liquid crystal display

LCD(Liquid Crystal Display), for many users may not be a new term, but the history of the existence of this technology may be far more than we imagined – as early as the end of the 19th century, Austrian botanists discovered liquid crystal, that is, liquid crystal. That is to say, a substance has both the fluidity of a liquid and a certain arrangement like a crystal. Under the action of electric field, the arrangement of liquid crystal molecules will change. This affects its optical properties, a phenomenon called the electro-optical effect. Using the electro-optical effect of liquid crystals, British scientists produced the first liquid crystal display (LCD) in the last century. Today’s liquid crystal display is widely used in the linear liquid crystal, if we look at it in the micro, we will find that it is particularly like cotton swabs. Compared with the traditional CRT, LCD is not only small size, thin thickness (the current 14.1-inch machine thickness can be only 5 centimeters), light weight, less energy consumption (1 to 10 microwatts/square centimeter), low operating voltage (1.5 to 6V) and no radiation, no flicker and can be directly matched with CMOS integrated circuits. Due to its many advantages, LCD has entered the field of desktop applications since 1998.

The first operational LCD was based on Dynamic Scattering Mode (DSM), developed by a team led by George Hellman at RCA. Heilman founded Optec, a company that developed a series of LCDS based on this technology. In December 1970, the rotating nematic field effect of liquid crystals was patented in Switzerland by the Central Laboratory of Zant and Helfrich Hoffmann-Le Rock. In 1969, James Ferguson discovered the rotational nematic field effect of liquid crystals at Kent State University in Ohio and registered the same patent in the United States in February 1971. In 1971, his company (ILIXCO) produced the first LCD based on this characteristic, which quickly replaced the poor performance of the DSM-based LCD.

It was only after 1985 that the discovery became commercially valuable, and in 1973 the Japanese company Sonbao first used it to make digital displays for electronic calculators. Nowadays, LCD is the main display device for notebook computers and handheld computers, and it also plays a very important role in projectors, and it is beginning to gradually penetrate the desktop display market.

LCD characteristics

Thin body saves space

Compared with the more bulky CRT monitors, LCD monitors only need one-third of the space of the former.

Save electricity, no high temperature

It is a low-power product, you can do no heat (the main power consumption and heating part exists in the backlight tube or LED), and the CRT display, due to the development technology inevitably produce high temperature.

Low radiation, good health

The radiation of LCD monitors is much lower than that of CRT monitors (just low, not completely without radiation, electronic products have more or less radiation), which is a boon for people who work in front of computers all day.

The picture is soft and does not hurt the eye

Unlike CRT technology, the LCD screen does not flicker, which can reduce the damage of the display to the eyes, and the eyes are not easy to fatigue.


Liquid crystal display is a kind of display using liquid crystal as the material. Liquid crystals are organic compounds that are intermediate between solid and liquid. When heated, it turns into a transparent liquid, and when cooled, it turns into a crystalline, cloudy solid. Under the action of the electric field, the liquid crystal molecules will change in arrangement, thus affecting the change of light through its light, which can be manifested as the change of light and dark through the action of the polarizer. In this way, people ultimately control the light and dark changes of the light through the control of the electric field, so as to achieve the purpose of displaying the image.

According to the arrangement of liquid crystal molecules, common liquid crystal displays are divided into: narrow-angle TN-LCD, STN-LCD, DSTN-LCD; Wide viewing Angle IPS,VA,FFS, etc.

Among them, TN-LCD, STN-LCD and DSTN-LCD three display principles are the same, but the distortion Angle of the liquid crystal molecules is different.

TN: Twisted Nematic liquid crystal molecules are twisted at 90 degrees.

STN: Super twisted nematic type (Super TN) Its S is the meaning of super, that is, the twisting Angle of the liquid crystal molecule is increased, which is 180 degrees or 270 degrees, so as to achieve a better display effect (due to increased contrast).

DSTN: Double layer STN. D stands for double layer, so it is better than STN. Because the structure of DSTN display panel is more complex than TN and STN, the display picture quality is more exquisite.

Resolution and display size

LCD liquid crystal display is widely used in industrial control, especially the man-machine of some machines, the panel of complex control equipment, the display of medical equipment and so on. I commonly used in industrial control and instrumentation in the LCD LCD display resolution is: 320×240, 640×480, 800×600, 1024×768 and above resolution screen, commonly used sizes are 3.9″, 4.0″, 5.0″, 5.5″, 5.6″, 5.7″, 6.0″, 6.5″, 7.3″, 7.5″, 10.0″, 10.4″, 12.3″15″17″20″ even now 50″YIS etc. The colors are black and white, false color, 512 color, 16 bit color, 24 bit color, etc.

Some users tend to confuse resolution and point distance, in fact, these are two distinct concepts. Resolution is usually expressed as the product of horizontal pixel points and vertical pixel points, and the more pixels, the higher the resolution. Therefore, the resolution is usually measured by the number of pixels, such as: 640×480 resolution, the number of pixels is 307200.

Note: 640 is the number of horizontal pixels, 480 is the number of vertical pixels.

Because in the graphics environment, high resolution can effectively shrink the screen image, so in the case of constant screen size, its resolution can not exceed its maximum reasonable limit, otherwise, it will lose meaning.

The size of a CRT display refers to the diagonal size of the picture tube. The maximum visible area is the maximum area that the display can display graphics. The size of the picture tube is usually measured in diagonal length, in inches (1 inch =2.54cm), common 15 inches, 17 inches, 19 inches, 20 inches, etc. The display area is smaller than the size of the display tube. The display area is expressed as the product of length and height, and is usually also expressed as the diagonal length of the visible part of the screen. The 15-inch display has a viewing range of about 13.8 inches, the 17-inch display has a viewing area of mostly between 15 and 16 inches, and the 19-inch display has a viewing area of about 18 inches.

The size of the LCD display refers to the diagonal size of the LCD panel, in inch units (1 inch =2.54cm), and now the mainstream has 15 inches, 17 inches, 19 inches, 21.5 inches, 22.1 inches, 23 inches, 24 inches and so on.

Display size Max resolution 14 inches 1024 x 76815 inches 1280 x 102417 inches 1600 x 128021 inches 1600 x 128024 inches 1920 x 1080(Full HD)

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