Number of views：2107order Release Date：2020-11-26

Substances in an intermediate state have both fluidity and continuity similar to liquids, as well as anisotropy similar to crystals. Ordered fluids like this are called liquid crystals.

Basic structure of 1-2 LCD monitoring devices

Some components of different types of LCD monitoring devices may vary, and some may not require polarizing plates. But the basic structure of two conductive glasses sandwiching a liquid crystal layer and sealing them together into a flat box is the same. If a polarizer is needed, it should be attached to the outer surface of the conductive glass.

1-3 Explain three ways of display using TN LCD

TN-LCD (twisted nematic liquid crystal monitoring device)

A nematic liquid crystal (Np liquid crystal) with positive dielectric anisotropy of about 10um is filled between two conductive glass substrates. The liquid crystal molecules are arranged along the surface, but the long axis of the molecules is continuously twisted 90 degrees between the upper and lower substrates, forming a twisted (TN) arranged liquid crystal cell.

1. Reflective type

Reflective type can save power by utilizing external light. TN type (twisted nematic) liquid crystal devices generally operate in a reflective type, where incident light first passes through the liquid crystal cell and is then reflected by the reflector. The reflector consists of a diffuse reflector and a mirror surface, which are adhered to the outer surface of the base glass. When two polarizing plates are orthogonal and the device operates in positive display, when not powered on, light passes through the upper polarizing plate and becomes linearly polarized light. When passing through the liquid crystal layer, the polarization direction rotates by 90 degrees and can reach the reflector through the lower polarizing plate. The reflected light has no change in polarization and once again passes through the liquid crystal cell and the upper polarizing plate to reach the human eye. When a sufficiently high voltage is applied, the liquid crystal molecules will be parallel to the electric field, and the polarization plane of light will no longer rotate, so light cannot pass through the liquid crystal cell to reach the reflective surface. Reflective will not be washed away even under direct sunlight. However, when observing liquid crystal devices in the dark or with insufficient background brightness, other artificial light sources need to be added. For this purpose, a light bulb is often installed at the edge of the diffuse reflection plate.

2. Transmissive type

TN type liquid crystals can also operate in transmissive mode, with the polarizer above the liquid crystal cell being a linear polarizer. The polarizer below is a linear analyzer. Their polarization axes are parallel to each other and aligned with the orientation of the liquid crystal molecules on the top substrate surface. When an external electric field is applied (relaxation state) and the incident light reaches the bottom of the liquid crystal cell, the polarization plane of the light will be perpendicular to the polarization axis of the polarizer, and the light will be blocked by the polarizer. When viewed from the back, the liquid crystal cell is opaque. After applying an external electric field, the incident light passes through the polarizer without rotating, and the liquid crystal cell appears transparent. So transmissive liquid crystals place the light source behind the display and the display modulates the incident light.55 inch LCD splicing screenLCD advertising machine