BackLight is located atLiquid crystal display(LCD) is a kind of light source behind it. Its luminous effect will directly affect the visual effect of the liquid crystal display module (LCM).The LCD itself does not emit light. It displays graphics or modulates lightresult。
·RelativeTFT-The backlight used in LCD has high requirements for shading, so most of the black and white glue is applied to the backlight of TFT-LCD.
·In addition to black and white glue, there is black and black glue (black on both sides), whose main function is still to fix and block light;Black silver glue (black on one side, silver on one side), in addition to shading, the silver side has a reflective effect.Black and white glue is the mainstream product in the market.
Applicable light source
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In the design of backlight, the selection of light source is very important.The light source used determines the power consumption, brightness, color and other photoelectric parameters of the backlight, as well as its service conditions and service life.The following table is available forLiquid crystal displayLight source of backlight and its characteristics Brief comparison introduction: light source shape, light source type, color, power consumption (W)（watt）Life (h)
(hour) characteristics
Point light source Lamp 2800K or so, above 1.0, 2000 Simple, small, low price, large volume, serious heating
Linear light sourceCCFL(ColdcathodeFluorescent tube) red, green, blue and their mixed colors 1.0~10.0 25000, high brightness, long life, high inverter drive voltage
HCFL 4.0~220 5~7000 seriously heats
Areal light sourceVFD(FlatFluorescent lamp）Below 200mW/cm2 5000 high brightness, good uniformity dual power drive
EL (electroluminescent film) below 20mW/cm2 5000 thin, good uniformity, short life, low brightness
OLED (organic light-emitting diode) over 1000 thin, good uniformity, high brightness and short life
FED(Flat field emission) Brightness above 10000 is under development
Module technology
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The core technology of the light source module isLight guide plateHowever, only a few large manufacturers can overcome the corresponding mold technology problems.[1]
form
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The backlight is mainly composed of light source, light guide plate, optical module and structural parts:
Light source: mainly EL, CCFL and LED backlight types;
Frame member: Structural parts include: back plate (iron back plate, aluminum back plate, plastic back plate), plastic frame, lamp holder, aluminum profile, aluminum base strip, of which the back plate and plastic frame are mandatory parts, and other structural parts are not fully used
Development trend
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Specifications
With the rapid development of the international IT industry, relevant LCD industries are constantly innovating. LCD products are developing in a diversified and lightweight way. Backlight, as one of the core components of LCD products, is bound to cooperate with this development trend and devote to product diversification and portability.
Light guide plate
The core technology of backlight module isLight guide plateThere are mainly two types of light guide plates, printing and injection molding. Others, such as injection molding plus printing, laser dotting and corrosion, account for a small proportion and are not suitable for batch production.The printed form has become the mainstream technology for a long time in the past because of its low cost, but its main disadvantage is that the qualified products are not high. LCD products require more precise light guide plate structure, and the injection molding light guide plate must become the mainstream of backlight development, but the corresponding mold technology problems can only be overcome by a few large Japanese manufacturers.
brightness
LCD has always had high requirements for the brightness of backlight source, but the high brightness also makes the LCD power consumption high. As the most power consuming accessory in LCD module, the backlight source can no longer meet the requirements of portable information products. Therefore, it is not suitable to increase the brightness of backlight source without increasing the power consumption and then increase the most power consuming accessoryPortable productsTherefore, it is also one of the main development trends to improve the backlight brightness and then increase the LCD brightness without increasing power consumption.The current goal is to reach 500-700cd/m2 brightness and 100000 hours of service lifeFluorescent lamp。[2]
Development forecast
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The global LCD and backlight industry focuses on Asia. In 2000, the regional distribution proportion of LCD production value was Japan (61%), South Korea (24%), and Taiwan (9%), which almost arranged the global production capacity.The second is mainland (3%), Europe (2%) and North America (1%).The main production areas of different LCD products are different, but it is obvious that Japan dominates the whole market trend, especially in the high price product market.Japan, known as the kingdom of liquid crystal display, not only has a long history of development, but also can provide various materials and equipment. In addition, each manufacturer has downstream application product brands, development and production capacity, and the complete industrial structure is the biggest advantage.Korean manufacturers are large enough and concentrate on large size panels, creating the top two TFT-LCD manufacturers in the world in a short time.Rising star Taiwan, with the world's most important downstream application product production kingdom, a huge domestic demand market, and full financial support, quickly seized the market.In 1999, Taiwan's LCD sales were about 436 million dollars;In 2000, the output value reached US $25.57;It is estimated that by 2005, Taiwan's TFT-LCD output value will reach US $11.629 billion, accounting for one third of the global TFT-LCD market share.
The backlight market mainly changes according to the changes in the LCD product market. According to the statistics of the Taiwan Investment Policy Commission, the global LCD market will grow at an annual rate of more than 15% in terms of the overall number. The consumer public's requirements for high image quality, high resolution and perspective of products will certainly make the CCFL backlight develop rapidly.In addition, according to the statistical data of the global backlight module market from Fuji Research Institute, Japan, the global sales of backlight modules reached 59 billion yen in 1999, althoughBacklight moduleThe price of LCD will decrease with the continuous reduction of LCD price. It is estimated that it will still grow rapidly at a rate of more than 12%, and the sales amount will reach 113 billion yen by 2003.[3]
