Full-color LED display is a new type of electronic communication media. It has irreplaceable advantages in terms of large size, high brightness and environmental adaptability. It can be used for large-scale indoor and outdoor large-scale graphic and video display. Used in advertising media, stage sets, building decoration, traffic information, stadiums and other purposes. With the rapid improvement of LED chip technology, packaging technology and LED display manufacturing technology and further decline in prices, full-color LED displays are crossing the cost-effective application threshold and gaining huge market applications and demands.
The most critical component of a full-color LED display is the LED device. There are three reasons: First, LEDs are the most used key components in the full-color screen, and thousands to tens of thousands of LEDs are used per square meter; second, LEDs are the main body that determines the performance of the entire screen’s optical display, which directly affects the audience. Evaluation of the display; Third, LEDs account for the largest proportion of the overall cost of the display, ranging from 30% to 70%.
LED is the most critical component of full-color LED display, equivalent to the CPU of a computer. The choice of LED has determined the quality of more than 50% of the entire display. If you fail to choose a good LED, the other parts of the display cannot make up for the defects of the quality of the display.
The quality and parameters of LEDs for full-color LED displays can be attributed to the following five elements:
1. Failure rate
Since the full-color display is composed of tens of thousands or even hundreds of thousands of pixels composed of three types of red, green and blue LEDs, the failure of any color LED will affect the overall visual effect of the display. Generally speaking, according to industry experience, the failure rate from the start of assembly to aging 72 hours before shipment should not be higher than 3/10,000 (referring to the failure caused by the LED device itself).
2. Antistatic ability
LED is a semiconductor device, which is sensitive to static electricity and can easily lead to static electricity failure. Therefore, the anti-static ability is very important to the life of the display screen. Generally speaking, the failure voltage of LED human body electrostatic mode test should not be lower than 2000V.
3. Attenuation characteristics
Red, green and blue LEDs all have the characteristic of brightness decay with the increase of working time. The quality of LED chips, the quality of auxiliary materials and the level of packaging technology determine the decay speed of LEDs. Generally speaking, after 1000 hours, 20mA normal temperature lighting test, the attenuation of red LED should be less than 10%, and the attenuation of blue and green LED should be less than 15%. The consistency of red, green and blue attenuation has a great impact on the white balance of the full-color LED display in the future, which in turn affects the display fidelity of the display.
4. Brightness
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the margin of the current used, which is good for saving power consumption and keeping the LED stable. LEDs have different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the viewing angle of the display. Generally, a 100-degree LED should be selected to ensure a sufficient viewing angle of the display. For displays with different dot pitches and different viewing distances, a balance point should be found in brightness, angle and price.
5. Consistency
The full-color display screen is composed of numerous pixels composed of red, green and blue LEDs. The consistency of the brightness and wavelength of each color LED determines the brightness consistency, white balance consistency and chromaticity consistency of the entire display screen. sex. Generally speaking, display manufacturers require device suppliers to provide LEDs with a wavelength range of 5nm and a brightness range of 1:1.3. These indicators can be achieved by the device supplier through a spectroscopic color separation machine. The consistency of voltage is generally not required.
Since the LED is angled, the full-color LED display also has angular directionality, that is, its brightness will increase or decrease when viewed from different angles. In this way, the angular consistency of red, green, and blue LEDs will seriously affect the consistency of white balance at different angles, and directly affect the fidelity of the video color on the display. To achieve the matching consistency of the brightness changes of the red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design in the design of the packaging lens and the selection of raw materials, which depends on the technical level of the packaging supplier. No matter how good the normal direction white balance is, if the LED angle consistency is not good, the white balance effect of different angles of the whole screen will be bad. The angle consistency characteristics of LED devices can be measured by LED angle comprehensive tester, which is especially important for medium and high-end display screens.
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