LED backlight is expected to replace CCFL into the mainstream

LED backlight source has a long life (100 thousand hours), the advantages of high color purity and color reproduction rate, high brightness, not afraid of cold, strong adaptability, good reliability, no mercury pollution in the future, the liquid crystal display (LCD) backlight field will occupy a pivotal position. With the continuous improvement of brightness, LED backlight will gradually replace the CCFL (cold cathode fluorescent lamp) backlight becomes the most important LCD backlight, but also will promote the further development of LCD technology.

LED backlight is expected to become mainstream

Liquid crystal display (LCD) has many advantages, such as low power consumption, light weight, thin thickness and so on. It is widely used in the field of computer display, TV and so on. Since the liquid crystal itself does not emit light, the LCD needs to be transmitted or reflected by an external light source. Most of the existing LCD are transmissive, so the backlight is an integral part of them.

The backlight system provides the light source for the LCD panel, which is mainly composed of light source, light guide plate, optical diaphragm and plastic frame. In order to ensure the quality of the display screen, LCD backlight source should have high brightness, uniform lighting, lighting angle, high efficiency, low power consumption, long life, light and other characteristics. LCD backlight is now used mainly CCFL, EL (electroluminescence) and LED, etc.. Compared with CCFL and EL backlight, LED backlight has many advantages, such as high brightness, high color purity, long life, strong adaptability, good reliability, low cost and easy industrialization. Now many of the world's leading LCD manufacturers are actively developing LED backlight system, and has been to the market. LED backlight will become the mainstream of the future LCD backlight.

LED is a kind of semiconductor device, which is formed by the unidirectional conduction of PN junction (P type semiconductor and N type semiconductor on the silicon wafer). When the current passes through, the electrons and holes are combined in the PN junction region. The wavelength of LED is determined by the band gap of the material, so the LED of different materials can emit different colors. Orange series and GaN series materials generally can be divided into LED GaAs lines of blue and white LED series, is a mixture of light of different colors and.

CCFL backlight or fade stage

Compared with the LED backlight, the traditional CCFL backlight has some shortcomings, which is mainly manifested in the:

First of all, CCFL will produce a lot of unnecessary spectrum beyond its peak spectrum, which will lead to the deterioration of brightness and affect the color reproduction of LCD. In LCD, the light emitted by the light source is made up of red, green and blue pixels on the LCD board. To obtain high color reproduction, LCD pixel light can only have a narrow spectrum around the main wavelength. To this end, the need for the development of new LCD backlight, while LED is a good choice.

Secondly, the white light of CCFL belongs to the cool color, the color rendering is poor, and the color produced on the object is not as bright as the sunlight. For example, the current commonly used CCFL LCD TV can only be performed in about 75% colors, using three color LED mixed white light, it can simulate the light of the sun, showing the natural color, irradiation on the object color is more vivid and bright than CCFL.

Thirdly, CCFL is a tubular light source, and it is necessary to distribute the light evenly to each area of the panel. In addition, the thickness of the screen is more difficult to control, and with the increase of the panel, you must use a number of light sources. With the increase of LCD size, the design of LED backlight module is simpler, and the cost is much lower than CCFL.

In addition, CCFL also has the disadvantages of low luminous efficiency, high discharge voltage, low discharge characteristics at low temperature, long time to reach stable gray time, and CCFL contains harmful metals, which do not meet the requirements of environmental protection. Compared with the traditional CCFL backlight, LED as a LCD backlight has the following advantages:

Is a good uniformity. LED is a planar light source, the most basic light-emitting unit is 3 mm to 5 mm length of the square (after packaging), very easy to be combined together to become the area of the surface light source, with a good brightness uniformity. As the backlight of LCD TV, the auxiliary optical components needed by LED can be done very simply, and the screen brightness uniformity is better.

Two is a good color. LED backlight has a better color gamut, color performance is stronger than the CCFL backlight, can display the lack of color of the liquid crystal technology plays a very good role in making up a good color reduction.

Three is a long life. LED the service life of up to 100 thousand hours, even if every 10 hours continuous use, also can use continuously for 27 years, greatly prolong the service life of the LCD TV, can obtain an overwhelming advantage of plasma technology.

Four is a low voltage drive. LED is using 5V ~ 24V low voltage power supply, very safe, driver circuit module design is relatively simple.

Five is good stability. Flat structure allows LED to have a solid internal structure, excellent seismic performance.

Six is green. LED does not exist in the environment harmful metal mercury, more environmentally friendly.

LED backlight technology needs to be improved

In recent years, LED backlight began to be used in LCD TV and high-end LCD display. However, LED wants to occupy the mainstream of large size LCD backlight also need to solve some of the problems: the cost is too high, the price is expensive; the luminous efficiency; using LED as backlight has consistency of white light, this is a disadvantage compared with CCFL LED in the network design;