LCD liquid crystal display
Structure of the LCD liquid crystal box is placed in the middle of the two pieces of parallel to the glass substrates, the TFT (thin film transistor) is arranged on the substrate of glass, the glass substrate set color filter, by altering the voltage signal and TFT to control the direction of rotation of the liquid crystal molecules, so as to achieve the control of each pixel of polarized light emitted or not to display purposes.
LED is light emitting diode Emitting Diode Light. The LED application can be divided into two categories: one is the LED display; two LED single application, including LED backlight, infrared LED. Now on the LED display, China"s design and production technology level of basic and international synchronization. The LED display screen is composed of a light emitting diode array. It has low power consumption, long service life, low cost, high brightness, low failure, large viewing distance and so on.
The principle of back lightI In the current market, LCD monitors are mainly divided into two categories, one is the use of traditional CCFL (cold cathode fluorescent lamp) LCD, and the other is the use of LED (light-emitting diode) backlight lcd. Many consumers directly to the first type of display called LCD, the second type of display is called LED. In fact, such a statement is not correct. Therefore, in the distinction between LCD and LED, but also can be distinguished from the principle of backlight.
LED backlight principle
LED backlight using light emitting diode as light source. Light emitting diode made from several layers of thin doped semiconductor material, with a layer of excess electronic, another layer is the lack of electronic and the formation of positively charged holes, when the current through the, combination of electrons and holes, the excess energy is in form of optical radiation is released. Light emitting diodes with different light emitting properties can be obtained by using different semiconductor materials.
LED luminescence technology has obvious advantages in color, so it is favored in the manufacture of display. The outmoded CCFL (cold cathode backlight) due to the limitations of the spectrum, color gamut range is large, about the best performance is only 70% of the NTSC color gamut, higher color effect to pay a high cost.
But the use of LED as a backlight source is completely different, because the LED (light emitting diode) light covering a range of chromatography is wider, emitting area is more uniform, normal color gamut range can be easily reached 100% ~ 130%, not like traditional CCFL backlight appear 30% loss of color. So LED backlight display color is more full, the details of the picture clearer, more natural color transition.
CCFL backlight principle
CCFL (cold cathode fluorescent lamp backlight physical constitution is in a glass tube sealed Sui gas Ne+Ar mixed gas, which contains trace mercury vapor (mg), and in the glass wall is coated with a fluorescent body. The working principle is when high voltage at both ends of the lamp, lamp in a high-speed electrons striking the electrodes to produce secondary electron emission and began discharging and inner tube of mercury or inert gas by electron impact, stimulate radiating 253.7nm UV, UV excited coated in the fluorescent powder on the inner wall of the tube and produce visible light. CCFL lamp life is generally defined as: in the ambient temperature of 25 degrees Celsius, with a rated current drive lamp, the brightness is reduced to 50% of the initial brightness of the working time length of the lamp life. At present, the nominal life of LCD TV backlight can be up to 60000 hours. CCFL (cold cathode fluorescent lamp) backlight is characterized by low cost, but the color performance is less than LED backlight.
There are still a large part of the display using traditional CCFL backlight, but compared to the current LED backlit display price advantage has been getting smaller and smaller, 18 inch led backlit display price has with CCFL displays is almost the same. Expected in the second half of this year, the price of 23 inches will also be flat with the corresponding size of the CCFL backlight display.
Three, the advantages and disadvantages of distinction:
The advantages and disadvantages of LED backlighta advantage
1) screen can do more thin our attention to see some of the liquid crystal display, can see the arrangement of a few filamentous CCFL tube, to make the screen light evenly, also need to add some other device, it can not do a very thin; the backlight is different, LED backlight source itself is planar light-emitting materials, as there is no need to add other devices.
2) not the Yellow becomes dark CCFL fluorescent lamp and fluorescent lamp as, a long time will be aging, so traditional laptop screen after two or three years will yellow and dark, and the service life of the LED backlit screen will be much longer, at least two or three times.
3) more power saving LED is a semiconductor, working at low pressure, the structure is simple, the power consumption is small.
4) more environmentally friendly CCFL lighting in the mercury pollution of the environment, harmless recycling has a lot of difficulties.
Disadvantages:
1) the relative price is higher at present in the case of the same specifications with the traditional CCFL backlight display between 300 - 100 yuan.
Advantages and disadvantages of CCFL backlight source
advantage
1) listed for a long time, the technology is relatively mature
2) color is more stable, professional level display is still used
3) the price is relatively low
Disadvantages:
1) shorter service life. CCFL back light source service life is generally 15000 hours to 25000 hours, in the use of 2 ~ 3 years later, the LCD screen will be dark, yellow, which is a short life cycle of CCFL caused by the defect.
2) the structure is complex, the brightness output uniformity is poor. In the display of the whole white or black screen, the difference between the screen edge and the center is very obvious.
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