1. Perspective
The viewing angle of the LED display is determined by the viewing angle of the LED lamp beads. At present, most outdoor displays use elliptical LEDs with a horizontal viewing angle of 100°; and a vertical viewing angle of 50°; while indoor displays use SMD LEDs with a horizontal and vertical viewing angle of 120°. The display screen on the highway generally uses 30° because of its particularity; a round LED with a viewing angle is sufficient. Some high-rise display screens have higher requirements for vertical viewing angles. Viewing angle and brightness are contradictory to each other, and a large viewing angle will inevitably reduce brightness. The choice of perspective needs to be determined according to the specific purpose.
2. Brightness
LED brightness is an important determinant of display brightness. The higher the brightness of the LED, the greater the margin for the use of current, which is good for saving power 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 sufficient viewing angle of the display screen. For displays with different dot pitches and different viewing distances, a balance should be found in brightness, angle, and price.
3. Failure rate
Since a full-color display screen is composed of tens of thousands or even hundreds of thousands of red, green, and blue LEDs, 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 from the start of the assembly of the LED display to the 72-hour aging before shipment should be no more than three ten thousandths (referring to the failure caused by the LED lamp beads itself).
4. Antistatic ability
LED is a semiconductor device, which is sensitive to static electricity and can easily cause static failure. Therefore, the antistatic ability is very important to the life of the display screen. Generally speaking, the failure voltage of the human body electrostatic mode test of the LED should not be lower than 2000V.
5. Life
The theoretical life of the LED device is 100,000 hours, which is much longer than the working life of other parts of the LED display. Therefore, as long as the quality of the LED device is guaranteed, the working current is appropriate, the PCB heat dissipation design is reasonable, and the display screen production process is rigorous, the LED device will be the entire display screen. One of the most durable parts in the machine.
LED devices account for 70% of the price of LED displays, so LED devices can determine the quality of LED displays. my country is not only a major producer of LED devices, but also a gathering place for LED display manufacturing. The high technical requirements of LED displays are the future development trend. The high quality requirements of LED displays are not only about the trend of LED display manufacturers, but also the development of LED display device manufacturers. From the checkpoint of LED devices, it promotes China's transformation from a large LED display manufacturing country to a powerful LED display manufacturing country.
6. Attenuation characteristics
LED display screens will appear brightness decline and display color inconsistency after long-time work, mainly due to the brightness decay of LED devices. The attenuation of LED brightness will reduce the brightness of the entire screen. The inconsistency in the attenuation of the brightness of the red, green, and blue LEDs will cause the color of the LED display to be inconsistent, which is the phenomenon that we often say that the display is spent. High-quality LED devices can well control the brightness attenuation range. According to the standard of 20mA lighting at room temperature for 1000 hours, the red attenuation should be less than 2%, and the blue and green attenuation should be less than 10%. Therefore, the blue and green LED should not use 20mA current when designing the display. It is best to use only 70% to 80 % Of rated current.
The attenuation characteristics are not only related to the characteristics of the red, green, and blue LEDs, but also the current used, the PCB board heat dissipation design, and the ambient temperature of the display screen all have an impact on the attenuation.
7. Size
The size of the LED device affects the pixel point distance of the LED display screen, that is, the resolution. 5mm oval lights are mainly used for outdoor display screens above P16, 3mm oval lights are mainly used for outdoor display screens of P12.5, P12, P10, and 3528 SMD LEDs are mainly used for indoor display screens of P6 and P8. 2020-type SMD LEDs are mainly used for indoor displays such as P2 and P3. Under the premise that the dot pitch is constant, the size of the LED device increases, which can increase the display area and reduce the graininess, but because the black area is reduced, the contrast will be reduced; on the contrary, the LED size is reduced, the display area is reduced, and the graininess is increased. , The area of the black area increases, increasing the contrast.
8. Consistency
The full-color display is composed of countless red, green, and blue LEDs. The brightness and wavelength consistency of each color LED determines the brightness consistency, white balance consistency and chromaticity of the entire display. Sex. Generally speaking, display screen 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 spectroscopy 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, when viewed from different angles, its brightness will increase or decrease. In this way, the angle consistency of the red, green, and blue LEDs will seriously affect the consistency of the white balance at different angles, and directly affect the fidelity of the video color of the display screen. 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 package lens design and raw material selection, which depends on the technical level of the package supplier. No matter how good the normal direction white balance is, if the LED angle consistency is not good, the white balance effect of the whole screen at different angles will be bad. The angle consistency characteristics of LED lamp beads can be measured with an LED angle comprehensive tester, which is particularly important for medium and high-end display screens.
