LCD display is a display that uses liquid crystal as the material. Liquid crystal is an organic compound that lies between solid and liquid. When heated, it becomes a transparent liquid, and when cooled, it becomes a crystalline cloudy solid. Under the action of an electric field, the arrangement of liquid crystal molecules will change, thereby affecting the changes in the light passing through it. In this way, people ultimately control the brightness changes of light by controlling the electric field, thereby achieving the goal of displaying images.
According to the arrangement of liquid crystal molecules, common liquid crystal displays are divided into: TN-LCD 、STN-LCD、 Narrow angle DSTN-LCD; IPS, VA, FFS and other broad perspectives.
TN type is currently the most mainstream LCD display mode in the market, widely used in entry-level and mid-range panels.
At present, the common performance indicators are not outstanding, and there are natural chronic diseases in the viewing angle. The TN panels seen on the market are all improved versions of TN+film, Film is a compensation film used to compensate for the insufficient viewing angle of TN panels. If the TN panel is better than the previous two panels, it is because of its output. There are many grayscale levels, and the deflection speed of liquid crystal molecules is fast, which can easily improve their response time. At present, liquid crystal products below 8ms on the market all use TN panels. Overall, TN panel is a product with obvious advantages and disadvantages. The price is cheap and the response time can meet the requirements of the game, which gives it an advantage. Inadequate visual angle and unrealistic color representation are obvious drawbacks
DSTN scans twisted nematic liquid crystal displays through dual scanning to achieve display objectives. DSTN has evolved from Super Twisted Column Display (STN). Due to the use of dual scanning technology in DSTN, the display effect is greatly improved compared to STN.
The wide-angle mode is commonly used in LCD TVs. Taking IPS as an example, it is a panel technology launched by Hitachi in 2001, also commonly known as "Super TFT". From a technical perspective, the liquid crystal molecules in traditional LCD displays generally switch between vertical and parallel states. MVA and PVA have improved it to a vertical bidirectional tilt switching method. The biggest difference between IPS technology and the aforementioned technology is that, regardless of the state, the liquid crystal molecules are always parallel to the screen, but the rotation direction of the molecules is different when turned on/in normal state - note that, The rotation of MVA and PVA liquid crystal molecules belongs to spatial rotation (Z-axis), while the rotation of IPS liquid crystal molecules belongs to in-plane rotation (XY axis). To complement this structure, IPS needs to improve the electrodes, which are located on the same side to form a planar electric field. The problems brought about by this design are twofold. On the one hand, the issue of perspective has been resolved. On the other hand, due to the edge electric field effect, the liquid crystal light efficiency (transmittance) is low, so IPS also has the disadvantage of slow response time. 16.7 million colors, 178 degree viewing angle, and 16ms response time represent the highest level of IPS liquid crystal displays today.
From the perspective of LCD driver mode, the most common is TFT (Thin Film Transformer) driver. It achieves independent and precise control of each pixel point through active switching, thus achieving a more precise display effect than previous passive driving (commonly known as pseudo color).
Therefore, currently most LCD displays, LCD TVs, and some mobile phones are driven by TFT. LCD displays often use narrow angle TN mode, while LCD TVs often use wide angle IPS mode. They are commonly referred to as TFT-LCD.
The composition of TFT-LCD mainly consists of fluorescent tubes (or LED Light Bars), light guide plates, polarizers, filters, glass substrates, alignment films, liquid crystal materials, thin transistors, etc. Firstly, the LCD display must use backlight to project light through the polarizer and then through the LCD light source. At this point, the arrangement of liquid crystal molecules will change the polarization angle of light propagating through the liquid crystal, and then the light must pass through a color filter and another polarizer in front of it. Therefore, by changing the voltage applied to the liquid crystal, we can control the final light intensity and color, thereby changing the color combinations of different tones on the liquid crystal panel.
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