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Of LED display
LED display from a list of light-emitting diodes, permutation and combination, so the quality of the LED display screen directly affects the overall quality.
The importance of LED (light-emitting diode) to display is like a car engine, air conditioning compressor. Choose a good performance of the LED is to complete the basic conditions of a high-performance LED display. The litmus test of a display screen manufacturers can use leds is well. Generally considered display has the following five key performance indicators (kpis) is closely related to the LED quality parameters: brightness and perspective, uniformity and clarity, the rate of pixels is out of control, the life, energy consumption and energy efficiency.1, brightness and perspective
Display brightness is mainly depends on the density of the luminous intensity of LED and LED. In recent years, LED substrate, the extension, the chip and the encapsulation of new technology emerge in endlessly, especially the indium tin oxide (ITO) current extension layer technology and stable and mature technology, the LED the luminous intensity is greatly enhanced. At present, the international first-class brand of small power LED in a horizontal Angle is 110 degrees, under the condition of vertical Angle of view of 50 degrees, luminous intensity of the green pipe has been as high as 4000 MCD, red tube of 1500 MCD, blue tube 1000 MCD. In pixel pitch of 20 mm, the display brightness can reach more than 10000 nit. Display screen can be all-weather work in any environment.
When it comes to screen Angle, there is a phenomenon worth thinking about: LED display, especially the outdoor screen, people's viewing Angle from the bottom up, basic and with the existing LED display product form, half of the luminous flux disappeared in the vast sky.
2, uniformity and clarity
Uniformity of the LED display technology development today, has become the most important indicator of success for display. People often say that LED display "little bright, and patches of brilliance", is seriously uneven between and module between the pixel image of a metaphor. Major point is the "dust effect" and "Mosaic phenomenon".
The root cause of the uneven phenomenon mainly include: LED the inconsistent of performance parameter; Display in the process of production, installation, assembly precision insufficient; Other electronic components of the electrical parameters consistency is not enough; Module and PCB design is not standard, etc.
How to solve the LED performance parameters of the inconsistent phenomenon, at present there are mainly two ways: one is through further subdivision of the LED specification, improve the consistency of the LED various performance; The second is to improve the uniformity of the screen by means of follow-up correction. Subsequent correction from the early module calibration, calibration module, development to today's point correction. Correction technology is from pure light intensity correction, to strong light color coordinates correction.
But, we think the follow-up correction is not everything. Among them, the optical axis is not consistent, inconsistent intensity distribution curve, the attenuation characteristics are inconsistent, poor assembly accuracy and non-standard design cannot be through follow-on correction to eliminate, even the subsequent correction will make optical axis, attenuation and assembling accuracy of inconsistent even worse.
Therefore, our conclusion is: through practice the follow-up correction is just the cure table, and LED subdivision is the fundamental parameters, is the mainstream of LED display industry in the future.
To display uniformity and clarity in terms of the relationship, the industry is often there is a misunderstanding on and that the substitution of resolution for clarity. Screen resolution is actually the human eye to screen resolution, uniformity (signal-to-noise ratio), comprehensive the subjective feeling of brightness, contrast and so on many factors. Pure physical pixel pitch raise resolution, and ignore the uniformity, is no doubt to improve clarity. Imagine a serious "dust effect" and "Mosaic phenomenon" screen, even if its physical pixel pitch again small, high resolution, it is impossible to get a good image resolution.
Therefore, in a sense, the current restriction LED display resolution improvement is a major cause of "uniformity" instead of "physical" pixel spacing.
3, display pixel is out of control
Display pixel control caused for many reasons, one of the most important reason is that "LED failure".
LED the failure cause and can be divided into two aspects: one is LED their poor quality; Second, the improper usage. Through analysis we conclude a LED failure mode and the corresponding relations between the two main reason.
The above we talked about a lot of LED failure usually in LED routine inspection cannot be found in the test. In addition to electrostatic discharge, large current (causes junction temperature is too high), external force, such as the improper use, a lot of LED failure is in the high temperature, low temperature, rapid changes in temperature or other harsh conditions, due to the LED chip, epoxy resin, stents, fuses, solid crystal glue, PPA in the cup body material such as the difference of thermal expansion coefficient, the internal stress of different, therefore, the LED quality testing is a very complicated work.
4, life
The factors affecting the service life of LED display have internal cause and external cause, internal cause are peripheral parts performance, LED light-emitting device performance, fatigue performance; Internal cause have LED display working environment and so on.
1). The peripheral parts
Besides LED devices, LED display also use many other peripheral parts, including PCB, plastic shell, switching power supply, connectors, chassis, etc., of any part of a problem, can lead to the life of the screen. So, display the longest life is decided by the key components of the short-lived life. , for example, LED, switch power, metal shell are calculated by 8 years, material, standard, and circuit protection process performance can only support the work for three years, three years later because of corrosion damage will happen, so we can only get a 3 years of the life of the display screen.
The influence of 2). The LED device performance
LED light-emitting device is display is also related to the life the most the most critical parts. For the LED, mainly the following indicators: attenuation characteristics, water vapor permeability properties, resistance to ultraviolet prevention performance. If the LED display manufacturer for the LED indicators of performance evaluation of the device does not pass, is applied to the display screen, can lead to a large number of quality accident, serious influence the life span of the LED display.
3.) product of anti-fatigue performance impact
How the anti-fatigue performance of LED display products, depending on the production process. Poor anti-corrosion treatment technology to produce module to guarantee the anti-fatigue performance of changes in temperature and humidity, protective circuit board surface will appear crack, led to the decrease of the protective performance.
So the LED display production process is to determine the key factors of display life. Screen production involved in the production process are: components, storage and pretreatment furnace welding technology, anti-corrosion treatment, waterproof sealing process, etc. The effectiveness of the process and selection of materials and grouting parameter, control, and related operator quality, for the vast LED display manufacturer, it is very important to the accumulation of experience, a factory with many years of experience in the production process of the control will be more effective.
4). The influence of the working environment
For different purposes, display of working conditions vary widely. From the aspects of environment, the indoor temperature difference is small, no rain and snow and ultraviolet radiation; Outdoor temperature up to 70 degrees, and the wind or sunshine. Harsh environment will aggravate the ageing of the display, working environment is one of the important factors affecting the service life of the display.
The life of the LED display is decided by many factors, however, is caused by many factors of life end can be via change parts (such as switching power supply) to keep the continuation of life. And the LED is not may be a lot of change, therefore, once the LED life end, means that the screen life termination.
We say the LED display screen, the life of a life decision but is not to say that the LED life is equal to the display screen life. Because the display is not at work, each LED all the time in full, video programming on display in the normal circumstances, the life of the display period should be LED life period of 6 ~ 10 times, when the LED to work in a small current under the conditions of life can be longer. Therefore, choose the brand of LED display screen life period of up to 50000 hours.
How to make leds last longer? Normally we can start from two aspects of device fabrication and device applications. In device manufacturing ways: choose high quality epitaxial materials; Increasing the chip area, reduce the current density; Balanced current density; Lower thermal resistance; Choose good performance and strong ability to resist ultraviolet encapsulation materials can make leds last longer.
In terms of device applications: heat as from module design to project implementation and system maintenance in the future a center; Reduce the LED working current; Correctly configured LED, make each color LED synchronous attenuation can be prolonging the service life of the LED.
The quality of LED lamp is stable, and the lamp body itself is important heat dissipation, high brightness LED full color on the market at present the heat dissipation, usually adopt natural cooling, the effect is not ideal. Heat do not ideal, the life of itself of lamps and lanterns will be affected.
5, energy consumption and energy efficiency
Improve the LED lights, reduce energy consumption of the display is an important development direction of LED display technology, it has the following positive significance: one is energy saving, emission reduction and environmental protection; The second is to reduce power capacity expansion, the investment of power device and a cooling device; 3 it is to save electricity to reduce operating costs; Four is lowering the temperature rise of the display screen; Five is slow attenuation of LED; Six is to improve the system reliability; Seven is extend the life of the screen; Eight is to minimize the temperature drift of display photoelectric parameters, stable image effect.
LED luminous efficiency (namely the external quantum efficiency) is determined by leds internal quantum efficiency and escape rate. Nowadays, LED the internal quantum efficiency is as high as 90% or more, but because of the escape rate is low, so the external quantum efficiency become the bottleneck of LED lights. In order to break through the bottleneck of restricting the development of industry, many innovative solutions have been proposed, at the same time, the theory, most of which has entered the stage of experiment, some have succeeded, and laid a solid foundation for the final industrialization.
of the LED display technology.
Anyway, device manufacturing and device application itself is a unity of a complementary device technology bring prosperity to the application market, and the application of the demand of the market is device the eternal power of technological progress. Only upstream and downstream enterprises work together to create a new future of LED display technology.