The size of the LED affects the pixel distance of the LED display, ie the resolution. The 5mm elliptical LED is mainly used for outdoor display of P16 and above, and the 3528 SMD LED is mainly used for indoor display of P6 and P8. Under the premise of constant dot pitch, the size of the LED increases, which can increase the display area and reduce the graininess. However, due to the reduction of the black area, the contrast is reduced. On the contrary, the size of the LED is reduced, the display area is reduced, and the graininess is reduced. Increased, the area of the black area increases, increasing the contrast.
LED brightness is an important determinant of LED display brightness. The higher the brightness of the LED, the greater the margin of current used, which is beneficial 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 angle of view of the LED display. Generally, a 100-degree LED should be selected to ensure sufficient viewing angle of the LED display. For displays with different dot pitches and different line of sight, a balance should be found in brightness, angle and price.
The full-color LED display is composed of countless red, green and blue LEDs. The brightness and wavelength consistency of each color LED determine the brightness consistency and white balance consistency of the entire display. Chromatic consistency. In general, LED display manufacturers require device suppliers to provide light-emitting diodes with a wavelength range of 5 nm and a brightness range of 1:1.3. These specifications can be achieved by device suppliers through a spectral color separation machine. The consistency of the voltage is generally not required.
4, failure rate
Since the full-color LED display 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 LED display. In general, according to industry experience, the failure rate before the LED display starts to assemble to aging 72 hours before shipment should be no more than three ten thousandths (refer to the failure caused by the LED itself).
5, antistatic ability
Light-emitting diodes are semiconductor devices that are sensitive to static electricity and are highly susceptible to electrostatic failure. Therefore, antistatic capability is critical to the life of the display. In general, the human body static mode test failure voltage of the LED should not be lower than 2000V.
6, attenuation characteristics
When the LED display is operated for a long time, the brightness will drop and the color of the display will be inconsistent, mainly due to the brightness decay of the LED device. The attenuation of the brightness of the LED will cause the brightness of the entire screen of the display to decrease. The inconsistency in the brightness attenuation of red, green and blue LEDs can cause inconsistencies in the color of the LED display, which is what we often say about the display. High quality LEDs provide excellent control of the brightness attenuation. According to 1000 hours of normal temperature lighting 20mA standard, red attenuation should be less than 2%, blue and green attenuation should be less than 10%, so blue and green LEDs should not use 20mA current in LED display design, preferably only 70% Up to 80% of rated current. In addition to the characteristics of the red, green and blue LEDs, the attenuation characteristics are affected by the current, the heat dissipation design of the PCB, and the ambient temperature of the LED display.
The viewing angle of the LED display is determined by the viewing angle of the LED. At present, most of the outdoor display screens use a horizontal viewing angle of 100°; a vertical viewing angle of 50°; an elliptical light-emitting diode, and an indoor display screen that uses a horizontal light-emitting diode of 120°; The display on the highway is generally 30° due to its particularity; a circular LED with a viewing angle is sufficient. Some high-rise buildings require a higher vertical viewing angle. The angle of view and brightness are contradictory, and a large angle of view necessarily reduces brightness. The choice of perspective needs to be determined based on the specific application. Since the LEDs are angled, the full-color LED display also has angular orientation, that is, the brightness is increased or decreased when viewed at different angles. In this way, the angular consistency of the red, green, and blue LEDs will seriously affect the consistency of the white balance at different angles, directly affecting the fidelity of the display video color. In order to achieve the consistency of brightness change of red, green and blue LEDs at different angles, it is necessary to strictly carry out scientific design on package lens design and raw material selection, depending on the technical level of the package supplier. In the normal direction, the white balance is good. If the angle of the LED is not consistent, the white balance effect at different angles of the whole screen will be bad. The angle uniformity of the LED can be measured by the LED angle comprehensive tester, which is especially important for medium and high-end displays.
8, life expectancy
The theoretical life of LED is 100,000 hours, which is much larger than the working life of other components of LED display. Therefore, as long as the quality of LED is guaranteed, the working current is suitable, the design of PCB heat dissipation is reasonable, and the production process of display is rigorous, the LED will be the whole display. One of the most durable parts in the machine. Light-emitting diodes account for 70% of the display price, so LEDs can determine the quality of the display. China is a big country in the production of light-emitting diodes, and it is also a gathering place for LED display. The high technical requirements of LED display is the future development trend. The high quality requirements of LED display are not only related to the trend of LED display manufacturers, but also the development of LED display device manufacturers. From the LEDs to check, promote China's transformation from a large LED display manufacturing country to a LED display manufacturing power.