With the 2009 LED backlit LCD display allows the display reached it easier to buy , LED backlit LCD display with a more advanced white LED devices from the amplitude reduces costs , environmental protection , energy saving, thin won many fashion ideas mainstream consumers, then what do LED -backlit display technology ? Compared with the traditional CCFL backlight what advantage ?

LED technology was born very early time , in 1923 , Rousseff (Lossen.ow) impurities in the study when the PN junction semiconductor SIC light emission , developed a light-emitting diode (LED: Light Emitting Diode), and this technology at the time and did not receive sufficient attention until 1962 , GE, Monsanto, IBM developed a joint laboratory hair red GaAsP (GaAsP) semiconductor compounds , from visible light emitting diodes into the commercial development process . With the advancement of technology, emitting different colors of LED devices one after another, in the 1970s , due to the large number of applications of LED devices in the home and office equipment leaving the LED price plummeted.

LED with its inherent characteristics, such as energy saving , long life , shock-resistant , fast response , and other characteristics of cold light source in many areas has been widely used in sports stadiums, large screen display system can live games and game scores , time , replay , etc. ; in the transportation industry , you can display road operation ; in the financial industry , can display real-time financial information, such as stocks , exchange rates, interest rates , etc. ; many malls big screen advertising is LED technology brings a new vision feelings.

DIY industry in the early 2000s has been an unprecedented development, the monitor as a display device is also important from a CRT, LCD development nowadays hottest LED backlit display . LED display technology today we have come together to explore it.

LED devices emitting principle

After a simple LED development Shijie Shao we first need to understand the principles of LED light emitting diode chips mainly by the PN junction , the electrode and the optical system. Its luminous body - chip area is 10.12mil (1mil = 0.0254 mm2) , the big chip LED appears on the current international chip area of ​​40mil.

Luminescence process includes three components: the carrier injection under forward bias , recombination radiation and energy transfer . Slight clean semiconductor wafer is encapsulated in epoxy resin composition , when the electrons pass through the wafer , the electrons move to the negatively charged and positively charged region of the hole with the compound, while the disappearance of electrons and holes generated photons. Energy ( band gap ) between the electron and the hole and the energy of photons generated higher. The energy photons in turn corresponds to the color of the light , the spectrum of visible light , blue light , violet light energy to carry up , orange light, red light carries the least energy . Because different materials having different band gaps , it is possible to emit different colors of light.

The basic characteristics of the LED light source

High luminous efficiency

LED After decades of technological improvements , the luminous efficiency has been greatly improved. Incandescent , halogen light efficiency is 12-24 lm / W , fluorescent light 50 to 70 lumens / watt, sodium 90 to 140 lm / W, most of the power into heat loss . LED luminous efficiency will be improved to achieve up to 50 ~ 200 lumens / watt , and its light color is good , narrow spectrum , no colored filters can be sent directly visible .

Less power consumption

LED single tube power from 0.03 to 0.06 watts, DC drives, single -tube drive voltage of 1.5 to 3.5 volts, the current 15 to 18 mA , fast response , can operate at high frequencies .

Long life

Electronic light field radiation emitting filament light easy to burn , heat deposition , the light attenuation and other shortcomings. And CCFL light source life of 50,000 hours compared , LED originals generally reached about the life of 100,000 hours , and in the production process, but also do not want to use CCFL mercury will pollute the environment , but also more environmentally friendly.

Strong safety and reliability

Low heat , no heat radiation , cold light source, can be safely arrived in touch : can precisely control the light pattern and light angle , light color and soft , no glare ; do not contain mercury , sodium and other potential health hazards of substances. The built-in micro-processing system to control light intensity , adjust light way to achieve light and art .

High color purity

LED devices emit optical purity is very high , in the spectrum of the light is focused on the performance of a short wavelength.

High response time

Compared with the CCFL light millisecond response time , LED light sources can achieve nanosecond response time. Therefore, to improve smearing a liquid crystal display also has considerable significance.

The shortcomings of traditional CCFL backlight

Before revealing defects CCFL backlight imaging principle we first look at the LCD display.

It is used in organic crystal molecules in liquid form at room temperature , the characteristics of the order will be arranged by the voltage changes occur, so that the white light emitted by the backlight after transmission of the liquid crystal molecules in different states , three colors through RGB color filters after the realization of imaging film. If we are close to the liquid crystal display screen , you will find an LCD monitor is powered by a tiny red, green and blue dots. Analogy , like LCD imaging principle put a lamp in the back window , through the window of the control switch for light control can be achieved .

Understanding the characteristics of the liquid crystal display imaging principle and LED products later, we look back at how the performance of today's conventional LCD monitors , LCD monitors from its birth date can not solve its easy to produce motion blur , poor contrast , color gamut and small birth defects. These are derived from the type CCFL backlight .

CCFL exactly?

CCFL light source that (Cold Cathode Fluorescent Lamps) cold cathode tube . Whether it is from the light-emitting principle , or from the physical structure point of view , CCFL light source and fluorescent tubes we use every day are very close . Both ends of the tube through the electrodes , so that the lamp by the collision of gaseous mercury UV excited phosphors on the wall , which emit light.

Defects in a CCFL light source

Even in terms of mainstream monitors, LCD TV, etc. , but it is not an optimal solution. Subject to the impact of process technology and production principle of CCFL , CCFL generally tubular light source to achieve uniform backlighting , the lamp must be used to simulate a large number of real surface light source . The resulting high power consumption , high-calorie very obvious , and can not achieve perfect flat light .

CCFL light defect two

Life CCFL light source only 50,000 hours or so, but with the growth of the use of time , the light emitted by the light source will become dim and yellow. As the LCD TV backlight remains constant as long as the boot after a consistent state , so that , after several years of use , the LCD TV will be obvious color cast, light attenuation problem.

CCFL light defect three

CCFL brightness are generally constant, even if the liquid crystal molecules in a fully closed state , there will be some light coming from the transmission , so the current LCD TV is difficult to show true black , which also led to the LCD TV poor contrast defects .

CCFL light defect four

CCFL biggest flaw from a defect on the spectral characteristics . We have said above , the white light emitted to the backlight after the final RGB color filter to achieve the imaging , so the white light emitted by the backlight R / G / B three primary colors of light wavelength ( i.e., three primary color purity ) will directly affect the final color display effect . From this perspective, it is not white CCFL issued an ideal light source spectral characteristics . So most of the LCD monitors currently on the market can meet the standard NTSC color gamut standard 60 % -78 % , greatly reduced the effect of natural color .

The new LED display technology analysis

Use in a variety of LCD LED light source devices are provided on a large area of ​​uniform LED backlight unit by way of a large plane order. According to the different colors of LED light can be divided into white LED backlight and RGB-LED backlight. Advantage of the white LED technology is mainly reflected in terms of power consumption , and therefore on the power requirements to have a broader application of high mobile devices , since 2004 , there are many laptops start using this technology .

LED color gamut advantages

RGB-LED backlight that can be issued by the high purity of red , green and blue light LED devices, to achieve a wide color gamut of traditional CCFL light source can not be achieved. The current mainstream RGB-LED backlight can already reach 105% of the NTSC color gamut , and as long as the use of more robust LED devices , now can achieve more than 120% of the NTSC color gamut . For this to restore the image -based displays, will be a very effective means to improve the image quality.

In addition to good color gamut performance, using RGB-LED light source can also be effective to enhance the contrast of the display to achieve more accurate color gradation and layering stronger screen. Since the backlight LED light source is many small units, each of which can be a light emitting device for precise brightness control. Conducted a small area under the original characteristics of the light-emitting screen brightness correction becomes possible, for example, in a strong chiaroscuro screen , LED backlight in dark areas can be completely closed and the LED backlight bright areas of high light output , resulting the effect will be to enhance the contrast of the past, LCD monitors with CCFL light sources can not match.

In addition to enhancing the role of the quality of LCD monitors use RGB-LED light source , you can achieve a smaller thinner thickness and weight , but also more in line with "flat " concept and a modern aesthetic . BenQ recently released V-Series products has taken control of the thickness of 15mm, in the future there may be more light and thin .

LED current shortage

Although the RGB-LED technology has many advantages, but in the current level of technology , it is inevitable that there are still some limitations . First , LED backlight used to a lot of independent LED devices, so to ensure the consistency of each light-emitting device is a more difficult problem , which also led to high rejection rate and cost burden. Second, although the higher the purity of RGB-LED color , but after long-term use of each LED color decay rate is not consistent , which will also have a greater impact on picture quality .

Show revolution imperative

Currently we are exposed to market LED -backlit displays are using lower-cost white LED backlit display , RGB-LED technology because of its cost and the current application of the few high-end products, saving products popular in the wind , the more lightweight and energy-efficient LED -backlit displays will replace the undisputed CCFL backlit display .

As in previous years the CRT LCD sideline , like color reproduction of LED devices around 100,000 hours of life and gluten are so CCFL shame. Nanoscale response time for the user's gaming and entertainment with an excellent choice. LED backlit display with its slimmer , energy saving, environmental protection and other requirements of the DC consumer trend is bound to replace CCFL.

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