Basic knowledge of LCD

Basic knowledge of LCD

The traditional CRT monitor mainly relies on the electron beam emitted by the electron gun in the picture tube to shoot the phosphor inside the display screen to emit light. Under the intentional interference of the artificial magnetic field inside the display, the electron beam will deflect at a certain angle to scan the target cell. Phosphor powder and display different colors. However, TFT-LCD adopts the "backlight" principle, using a lamp tube as the backlight light source, and achieving a more ideal display effect through the auxiliary optical module and the liquid crystal layer to control the light.

Liquid crystal is a kind of regularly arranged organic compound. It is a substance between solid and liquid. Currently, the nematic columnar liquid crystal whose molecular arrangement is most suitable for manufacturing liquid crystal displays is generally used. The liquid crystal itself cannot construct light. It mainly displays images by changing the arrangement of liquid crystal molecules due to the electric field generated by the change of voltage.

The liquid crystal panel is mainly composed of two soda-free glass sandwiched by a polarizer, a liquid crystal layer and a color filter. Polarizers and color filters determine how much light can pass through and what color light is generated. Liquid crystal is poured between two well-made planes to form a liquid crystal layer. There are many grooves on these two planes. The grooves on a single plane are parallel, but the grooves on the two parallel planes are parallel. Are perpendicular to each other. Simply put, if the grooves on the back plane are arranged longitudinally, then the front plane is arranged horizontally. The arrangement of liquid crystal molecules between two planes will form a gradual twisting state of 90 degrees in the Z axis. The light from the backlight source, that is, the lamp tube, passes through the backlight plate and reflective film on the back of the LCD screen to produce uniform backlight light. The light passes through the back layer and is twisted in the Z-axis by the liquid crystal, so that it can pass through the front layer plane. If a voltage is applied to the liquid crystal layer, an electric field will be generated, and the liquid crystal molecules will be rearranged. The light cannot be twisted and cannot pass through the front layer plane, thereby blocking the light.

The shortcomings of liquid crystal displays are that they are significantly different from CRT displays in brightness, image uniformity, viewing angle and response time. The response time and viewing angle both depend on the quality of the LCD panel, and the image uniformity has a lot to do with the auxiliary optical module. The brightness of the LCD mainly depends on the backlight source. Of course, the design of the entire module is also a factor that affects the brightness of the product.

Brightness-----Liquid crystal is a substance between solid and liquid. It can't emit light by itself. It needs additional light source. Therefore, the number of lamps is related to the brightness of the liquid crystal display.

Signal response time-----The response time refers to the response speed of the liquid crystal display to the input signal, which is the response time of the liquid crystal from dark to bright or from bright to dark, usually in milliseconds (ms). The signal response time is divided into two parts, namely "rise time" and "fall time", and what we call response time refers to the sum of the two. The smaller the response time, the better. The shorter the time, the less likely it is that there will be traces like afterimages or smearing when the user is watching the moving screen.