1, angle of view
The angle of the LED display depends on the angle of the LED beads. At present, most of the outdoor display screens choose horizontal view angle of 100 degrees; vertical view angle of 50 degrees; elliptical LED, indoor display screen, horizontal and vertical are 120 degrees; patch LED. Because of its particularity, the display screen on the highway generally chooses 30 degrees; the circular LED with the viewing angle is enough. Some high-rise displays require higher vertical viewing angles. Angle of view and brightness are contradictory. Large angle of view will inevitably reduce brightness. The choice of perspective needs to be determined according to its specific use.
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the current allowance, which is good for saving power and maintaining the stability of the LED. LED has different angle values. When the brightness of the chip is fixed, the smaller the angle, the brighter the LED, but the smaller the angle of the display screen. Generally, 100 degree LED should be selected to ensure that the display screen has sufficient perspective. A balance should be found in brightness, angle and price for different point spacing and different visual distance display screens.
3. Failure rate
Because the full-color display consists of tens of thousands or even hundreds of thousands of groups of red, green and blue LED pixels, the failure of any color LED will affect the overall visual effect of the display screen. Generally speaking, according to industry experience, the failure rate should not be higher than three-thousandths before the LED display starts to assemble and aging 72 hours before shipment (refers to the failure caused by the LED beads themselves).
4. Antistatic Ability
LED is a semiconductor device, which is sensitive to static electricity and easily leads to static failure. Therefore, the antistatic ability is very important to the life of the display screen. Generally speaking, the failure voltage of human electrostatic mode test of LED should not be less than 2000V.
5, life expectancy
The theoretical life of LED devices is 100,000 hours, which is much longer than the working life of other parts of LED display. So as long as the quality of LED devices is guaranteed, the working current is appropriate, the PCB heat dissipation design is reasonable, and the production process of display screen is rigorous, the LED devices will be one of the most durable parts in the whole display screen.
LED devices account for 70% of the price of LED display screen, so LED devices can determine the quality of LED display screen. Our country is not only a big producer of LED devices, but also a gathering place for the production of LED display screen. The high-tech requirement of LED display is the future development trend. The high-quality requirement of LED display is not only about the trend of LED display manufacturers, but also related to the development of LED display device manufacturers. From the control of LED devices, we will promote the transformation of China from a big manufacturing country of LED display screen to a powerful manufacturing country of LED display screen.
6. Attenuation characteristics
After a long time of work, the brightness of the LED display will decrease and the color of the display will be inconsistent, which is mainly caused by the brightness attenuation of the LED devices. The decrease of LED brightness will result in the decrease of the whole screen brightness. The inconsistency of the brightness attenuation of red, green and blue LED will cause the inconsistency of the color of the LED display screen, which is the phenomenon we often say that the display screen is spent. High quality LED devices can control brightness attenuation well. According to the standard of brightening 20mA at room temperature for 1000 hours, red attenuation should be less than 2%, blue and green attenuation should be less than 10%. Therefore, blue and green LED should not use 20mA current in the design of display screen, and only 70% to 80% rated current should be used.
The attenuation characteristics are related to the characteristics of red, green and blue LEDs. The current used, PCB board heat dissipation design, and the ambient temperature of the display screen all affect the attenuation.
The size of the LED device affects the pixel distance of the LED display screen, that is, the resolution. 5 mm elliptical lamp is mainly used for outdoor display screen over P16, 3 mm elliptical lamp is mainly used for outdoor display screen of P12.5, P12 and P10, 3528 patch LED is mainly used for indoor display screen of P6 and P8, and 2020 patch LED is mainly used for indoor display screen such as P2 and P3. On the premise of unchanged point spacing, increasing the size of LED devices can increase the display area and reduce the particle sensation, but because of the reduction of black area, the contrast will be reduced; on the contrary, the size of LED decreases, the display area is reduced, the particle sensation is increased, the area of black area is increased, and the contrast is increased.
Full-color display screen is composed of countless red, green and blue LED pixels. The consistency of brightness and wavelength of each color LED determines the consistency of brightness, white balance and chroma of the whole display screen. Generally speaking, display manufacturers require device suppliers to provide LED with a wavelength range of 5 nm and a brightness range of 1:1.3, which can be graded by device suppliers through spectrophotometer. Voltage consistency is generally not required.
Because the LED has angle, the full-color LED display also has angle orientation, that is, when viewed from different angles, its brightness will increase or decrease. In this way, the angle consistency of red, green and blue LED will seriously affect the consistency of the white balance of different angles, and directly affect the fidelity of the video color of the display screen. To achieve the matching consistency of brightness changes of red, green and blue LEDs at different angles, strict scientific design is needed in packaging lens design and raw material selection, which depends on the technical level of packaging suppliers. If the angle consistency of the LED is not good, the white balance effect of different angles of the whole screen will be bad. The angle consistency of LED beads can be measured by the integrated angle tester of LED, which is especially important for medium and high-end display.
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