Principle Of Liquid Crystal Display

Principle Of Liquid Crystal Display

Dec 20, 2017

1.  Common liquid crystal display

The liquid crystal display is divided into the electro-optical effect and the thermo optical effect of the liquid crystal.

Field effect: using anisotropic dielectric constant, belonging to this category are twisted nematic (TN), super twisted nematic (STN), double scanning super twisted nematic (DSTN) and DSTN (HPA), the effect of type (GH), phase type (PL-LCD), electrically controlled birefringence type (ECB) and ferroelectric effect type (FLC).

Current effect: the anisotropy of the heterosexual and electrical conductivity by the dielectric constant, which belongs to the only dynamic scattering type (DS).

The writing type of the thermal light effect is divided into the laser writing type and the heat discoloration of the bile chisel, and the laser is mainly used to heat the liquid crystal.

Electrothermal effect: the use of electrode heating to change the state of liquid crystal, with storage.

2. Three ways of liquid crystal display

The reflection formula is shown in Figure 7. The main feature is that the light source is not needed, so the power consumption is low. It is mainly used in the external environment light, generally used in the display of the instrument and the screen of the mobile phone. Sometimes in order to increase the brightness of the image at night or background brightness is insufficient, can increase the small side light source in the diffuse reflection plate edge, has now developed the image display notebook computer LCD screen using the ambient light reflection, the main work in the field, biggest feature is the power, long working time.


The transmission is shown as shown in Figure 8. It must use the light source, the main characteristics of high brightness, high contrast, wide viewing angle, most LCD screen work in this way, but the power consumption is high, especially in the portable notebook computer performance is particularly prominent, has developed a fuel cell battery with higher performance or longer, so power consumption is reduced to the secondary position.


Projection is mainly used in projection devices. It is used not only for front projection but also for rear projection. LCD device plays a role in projector, and it has modulating effect on transmission light source, so it is commonly called liquid crystal light valve. LCD projector with high brightness, high contrast, no geometric distortion, no convergence advantages of simple structure, poor light path, especially in recent years, the rapid development of the LCOS projector is more typical, in LCOS active matrix fabricated directly on silicon substrate, the size can be very small, a higher degree of integration, especially for in HDTV and combining the requirements of data display and television technology applications.