Classification and knowledge points of LCD backlight

Classification and knowledge points of LCD backlight panels

Backlights are optical components that provide a backside light source in LCD display products. Since the liquid crystal glass itself does not have light-emitting properties, a light-emitting source, that is, a backlight panel, will be added behind the liquid crystal glass as required. The application range covers medical, beauty, instrumentation, vehicle equipment, industrial equipment, bank terminals, office automation, communications, electronic toys and consumer products.

The working principle of the backlight panel:

The working principle of the LED backlight is to turn a point light source (LED) into a surface light source (backlight, backlight)

Backlight board classification:

At present, there are mainly three types of backlight panels: EL, CCFL and LED according to the type of light source. According to the distribution position of the light source, they are divided into edge type and direct type (bottom backlight type).

Here is a brief introduction to them:

◆Edge-light type: A backlight plate made by placing a linear or point light source on the side of a specially designed light guide plate. According to the needs of actual use, it can be made into a bilateral type or even a trilateral type. The edge light type backlight can generally be made very thin, but the light utilization rate of the light source is small, and the thinner the light source, the smaller the utilization rate, about 50 percent . The core of its technology is the design and production of light guide plates. Edge light type commonly used LED backlight and CCFL backlight.

◆LED light backlight: LED light is also called 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 have many colors, commonly used such as "Table 1" and "Table 2"; another special color is white, and "Table 3" gives its commonly used chromaticity range. In various colors, it can be roughly divided into two types: high light and low light: basically, "Table 1" belongs to low light (although amber, orange and red also have slightly high light), "Table 1" belongs to low light 2" and "Table 3" are highlighted.

Since white is a mixed color and has no identifiable wavelength value, it is represented by its coordinate value on the chromaticity diagram. We customize it as "Cool White" and "Warm White". In all kinds of colors, there is a problem of color deviation, among which blue and white are more obvious, especially white, and now LED suppliers cannot effectively control it.

◆CCFL backlight: The great advantage of this type of backlight is high brightness, so it is basically used in black and white negative phase, blue mode negative phase and color liquid crystal display devices with large area. In theory, it can make various colors according to the color matching principle of three primary colors. The disadvantage is that the power consumption is large, it needs to be driven by an inverter circuit, and the operating temperature is narrow, which is between 060 degrees, while other backlight boards such as LED can reach -2070 degrees.

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

◆ EL backlight: that is, electroluminescence, which is a cold light source that emits light by the intrinsic luminescence of phosphors excited by an alternating electric field. Its great advantage is that it is thin, and it can achieve a thickness of 0.20.6mm. The disadvantage is that the brightness is low, the life is short (usually 30005000 hours), it needs to be driven by inverter, and there will be flickering, noise and other defects due to the interference of the circuit. There are two types of EL drivers: inverter and Driver IC driver.

Because the frequency and load output voltage of the current Driver IC cannot reach the typical conditions of EL (400Hz, AC100V), the brightness is lower than that of inverter driving. Recently, white light (full color) EL and LCD backlight panels have also come out one after another. However, due to the darker brightness, it is basically used for small-sized liquid crystal displays below 4 inches. Such as: mobile phones, PDAs, game consoles, etc. Full-color (white light), large-size brightness backlight panels, and now the mainstream is still using CCFL as the light source.

◆LED bottom backlight: The advantages are good brightness and good uniformity. The disadvantage is that the thickness is large (greater than 4.0mm), the number of LEDs used is large, and the heating phenomenon is obvious. Generally, low-bright colors are used for design, and high-bright colors are basically ignored due to the high cost.