A brief discussion on the advantages and disadvantages of LED in backlight modules

1. Application in backlight module Has the advantage of power saving LED is used in backlight module as light source, replacing traditional cold cathode fluorescent lamp (CCFL). It is not only thin and light, power-saving, small in size, long in life, low in voltage, and fast in startup, but also has the concept of environmental protection. For notebook computers , depending on the processor and size, the power consumption of LCD panel accounts for about one-third of the whole machine. Due to the low power consumption of LED, the use time of NB using LED backlight can be extended by more than 1.5 hours; and the thickness of light guide plate with LED can be reduced from 2mm to 0.6mm (13.3-inch product), the thickness of the screen can be reduced, and the weight of the whole machine will also be reduced; and each CCFL currently contains about 2mg of mercury, using LED as light source can reduce the use of mercury. If RGB three colors are used to mix into white light, it can provide better color saturation, and the color of the TV screen will be brighter. LED can achieve regional dynamic control, and turn off when the screen is black in some areas to improve the contrast between light and dark, and it can also save power. LEDs have a fast response speed. Using RGB three-color LEDs with fast-response liquid crystals can use the color sequential method to omit the use of color filters. The luminous efficiency of LEDs is only 20 to 40 lm/W, which is not as good as CCFL's 80 lm/W. At the same time, the high cost is the biggest weakness of LED backlight modules. The unit price of a CCFL and a high-brightness LED is around US$1.5, but the number of LEDs used far exceeds that of CCFL. In addition, LEDs have poor heat dissipation. Large-size TVs still need to add a heat dissipation substrate, which will be another expense. The color decay speed of each LED is different, and long-term use will cause uneven color. LCD upstream and downstream manufacturers have invested in LED factories. The current main purpose is not to obtain LED production capacity but to consider technology. Technically, the packaging form of LEDs, the wavelength of light, the light angle, etc. will affect the backlight module. Both panel manufacturers and backlight module manufacturers need to cooperate with LED manufacturers with close relationships to provide special specifications of products for various experiments and reliability tests . In addition, panel manufacturers and backlight module manufacturers have faced the problem of CCFL shortage. Mastering the source of materials has become an important issue for panel manufacturers and backlight module manufacturers. They invest in LED factories to prevent the concerns of shortage after large-scale use of LEDs, rather than focusing on short-term benefits. 2. Impact and Observation Points Compared with CCFL, using LED as a backlight source has the advantages of being thin, environmentally friendly, and energy-saving, but the cost is the biggest disadvantage. It is expected that the proportion of LED backlights used in notebook computers will be less than 8% in 2007. The main reason is the competitive demand in other application fields. LEDs must be screened. How to remove LEDs that do not meet the requirements of backlight modules will be the most urgent issue to be solved; at the same time, TFT-LCD manufacturers and backlight modules want to lower prices to reduce costs, and LED manufacturers have good gross profit margins in other application fields. Whether they can supply in large quantities has also become a key. In 2006, notebook computer manufacturers only launched 11.3-inch and 12.1-inch notebook computers with LED backlights. Since there were not many notebook computers below 12.1 inches, and LED backlights were considered high-end models, the demand was limited. Starting in 2007, Apple, Asus, DELL and other computer manufacturers will successively launch 13.3-inch and even larger 15.4-inch products using LED backlights, but they are still positioned as high-end models and have no intention of shipping in large quantities. If the computer manufacturers do not change their product positioning of using LED backlight modules, it will not be of much help to the LED industry. As for environmental protection, the European Union (EU) implemented the RoHS Directive (The Restoration of Hazardous Substances in Electrical and Electronic Equipment) in July 2006 to ban hazardous substances in electronic products . Although mercury is a regulated item, CCFL can still be used due to the exclusion clause. Before the exclusion clause is abolished, it is impossible to force the use of CCFL. In the field of LCD TV , the cost of LED backlight module is too high, almost three times that of CCFL backlight module of the same size. The price of LCD TV using LED backlight is more than 30% of the same size. CCFL manufacturers have also launched wide color gamut fluorescent tubes (Wide Color Gamut-CCFL), which can reach more than 92% NTSC. However, the current TV signal is only NTSC 82%, and the effect of high color saturation is still limited. Therefore, SONY and Samsung have launched LED backlight module LCD TV, but the sales are not good. The significance of the technology indicator is greater than the actual profit. At present, LED will still be mainly used in small and medium-sized computers below 10 inches. In the notebook computer field, it is still necessary to wait for the computer manufacturers to launch mid-range products using LED backlight modules before the market can expand. As for the TV field, there are still cost and technical problems to be solved. In the next 2~3 years, it is likely that high-end products and even technical strength demonstrations will still be the main focus.