Principles of three types of LCD displays

TN type liquid crystal display principle

Although other forms of liquid crystal displays can be claimed to have been refined with the TN-type as their starting point, the TN-type is considered to be the most fundamental liquid crystal display technology. Its operating system is also more straightforward than those of other technologies. A straightforward structural diagram of a TN-type liquid crystal display is shown in the figure, which also includes polarizers for the vertical and horizontal axes, an alignment film with fine-grained grooves, a liquid crystal substance, and a conductive glass substrate.

1.In the absence of an electric field, incident light flows through the liquid crystal layer after passing through the polarizer, and the liquid crystal layer's twisted and ordered molecules cause the polarized light to rotate 90 degrees. As a result, the electrode surface is completely brilliant and the light may travel through it without obstruction.

2.When an electric field is supplied, each liquid crystal molecule's optical axis rotates in the same direction as the electric field, which prevents the liquid crystal layer from rotating light. As a result, the polarization direction of the polarized light from the incident polarizer matches that of polarized light from another polarizer. The electrode surface is in a dark condition because the direction is in a vertical relationship and cannot pass through. The liquid crystal material is sandwiched between two transparent conductive glasses and a polarizer is attached to it perpendicular to the optical axis. The liquid crystal molecules are rotated and arranged in sequence in accordance with the direction of the fine grooves on the alignment film. The light will be smooth if the electric field is not produced. The liquid crystal molecules enter from the polarizer, spin in the direction they are moving, and then leave from the other side.When two pieces of conductive glass are electrically charged, an electric field is formed between them that affects how liquid crystal molecules are arranged, twisting the rods so that light cannot pass through and blocking the source of light. This method of obtaining light-dark contrast is known as the "twisted nematic field effect," or TNFE (twisted nematic field effect). The twisted nematic field effect is the basis for almost all liquid crystal displays used in electrical devices.

STN liquid crystal display principle

The liquid crystal molecules in the twisted nematic field effect of TN rotate incident light by 90 degrees, whereas the liquid crystal molecules in the super twisted nematic field effect of STN rotate incident light by 180 to 270 degrees.

It should be emphasized that there is no method to modify the color of a basic TN liquid crystal display, which only has two light and dark (or black and white) scenarios. Light green and orange are the primary colors seen on a STN liquid crystal display because of the interaction between liquid crystal materials and the phenomena of light interference. However, if a color filter is added to the conventional monochrome STN liquid crystal display, every pixel of the monochrome display matrix is split into three sub-pixels, each of which passes through the color filter in turn. Display the red, green, and blue primary colors. It may also display the colors in full color mode by balancing the proportions of the three fundamental colors. Additionally, if the TN type liquid crystal display screen is larger, the contrast ratio will seem bad; however, with the enhanced technology of STN, it is possible to compensate for the absence of contrast ratio.

TFT liquid crystal display principle

The major parts of TFT-type liquid crystal displays, which are more intricate, consist of fluorescent tubes, light guide plates, polarizers, filter plates, glass substrates, alignment films, liquid crystal materials, thin-mode transistors, and others. The fluorescent bulb, which serves as the backlight for the liquid crystal display, must be used as the light source at the beginning. These light sources will go through the liquid crystal after passing through a polarizer first. The way the liquid crystal's molecules are arranged at this point alters the angle at which light enters the material. After that, the light must travel through a second polarizer and the color filter in front of it. Therefore, we can regulate the final light strength and color by changing the voltage value that stimulates the liquid crystal, and we can then alter the color combination of various hues on the liquid crystal panel.