Backlight is an optical component that provides a backlight source in LCD display products.Because the liquid crystal glass itself does not have luminous characteristics, so according to the need to add a light source behind the liquid crystal glass, that is, the back light plate.Applications in medical, beauty, instrumentation, vehicle equipment, industrial equipment, banking terminals, office automation, communications, electronic toys and consumer products.



Working principle of backlight plate:


The LED backlight works by turning a point light source (LED) into a surface light source (backlight, backlight).

Backlight board classification:

At present, there are three types of backlight plate, namely EL, CCFL and LED, according to the light source distribution position, it is divided into side light type and straight down type (bottom backlight type).



Here's a brief introduction to them:


◆ Side light type: the line or point light source is set in the side of the specially designed light guide plate made of backlight plate.According to the needs of actual use, it can be made bilateral or even trilateral.Edge light backlight can generally be very thin, but the light utilization rate of the light source is small, and the thinner the utilization rate is smaller, about 50%.Its technical core is the design and manufacture of light guide plate.Edge light type is commonly used with LED backlight and CCFL backlight.

◆LED backlight: LED light, also known as light-emitting diode, compared with other light sources, the power consumption of a single LED light is very small.From blue to red, LED lights come in a variety of colors, commonly used as "Table 1" and "Table 2";Another special color is white, and Table 3 shows the range of shades commonly used.Colors can be roughly divided into highlights and lowlights: basically, "Table 1" is low-light (although amber, orange, and red also have slightly brighter colors), and "Table 2" and "Table 3" are highlights.

Since white is a mixed color, it has no identified wavelength value. Therefore, it is represented by its coordinate value on the chromaticity chart.We customize it as "cold white" and "warm white".In all kinds of colors, there is the problem of color deviation, among which blue and white are more obvious, especially white. Now the LED supplier can not effectively control it.

◆CCFL backlight: the great advantage of this backlight is high brightness, so the area of large black and white negative phase, blue mode negative phase and color liquid crystal display devices are basically using it.Theoretically, it can make a variety of colors according to the principle of three primary color matching.The disadvantage is that the power consumption is large, but also need to drive the inverter circuit, and the working temperature is narrow, between 0~60 degrees, and LED and other backlight board can reach -20~70 between.

◆ Backlight type: is a flat surface light source with a certain structure, can be a continuous and uniform surface light source, such as EL or flat fluorescent lamp;It can also be composed of more point light sources, such as dot matrix LED or incandescent backlight plate, etc.LED lattice and EL backlight are commonly used.

EL backlight: that is, electroluminescence, is by fluorescent powder in the alternating electric field excitation intrinsic luminescence and light cold light source.Its great advantage is thin, can do 0.2~0.6mm thickness.The disadvantage is low brightness, short life (generally 3000~5000 hours), the need for inverter drive, but also by the interference of the circuit and flicker, noise and other bad.EL is driven by inverter and Driveric driver.

Because the current Driveric frequency and load output voltage do not meet the typical EL conditions (400Hz, AC100V), the brightness is lower than that of the inverter driver.Recently, there have also been white light (panchromatic)EL and LCD backlight panel.However, due to its low brightness, it is basically used for small size LCD display under 4 inches.Such as: mobile phone, PDA, game consoles and so on.Panchromatic (white light), large size brightness backlight board, now the mainstream is still using CCFL as the light source.

◆LED backlight: good brightness, good uniformity.The disadvantage is that the thickness is larger (greater than 4.0mm), the number of LED used is more, and the heating phenomenon is obvious.Generally, low light color is used for design, while high light color is basically not considered because of the high cost.


The classification and knowledge of liquid crystal screen backlight plate