Simplified LED backlight heat dissipation mechanism
On October 25th, Nikkei BP reported that the Japanese electrical and chemical industry has made the β-SiAlON green fluorescent material reach a practical level. A high color rendering white LED that can be used in combination with green and red fluorescent materials on blue LEDs. Compared with ordinary silicate-based green fluorescent materials, it has a characteristic of a decrease in luminous intensity when temperature rises (Fig. 1). This product is expected to be applied to white LEDs for LCD TV backlights.
When the white LED is lit for a long time, "the temperature immediately above the chip will reach 100 to 150 ° C" (Electrical Chemical Industry). If it is a white LED using a silicate-based green fluorescent material, there is a problem that the green light-emitting intensity is lowered and the color balance is broken. Therefore, for an LED backlight such as a liquid crystal television, a sufficient heat dissipation mechanism is indispensable.
The β-SiAlON green fluorescent material developed this time (Photo: Electrochemical Industry)
The green fluorescent material of this time has a strong covalent bond between atoms, and has excellent structural stability to temperature, so the variation in luminous intensity is small. If it is a white LED with a small color change at high temperatures, the heat dissipation mechanism of the backlight can be simplified. Although the price is "multiple times" of the silicate-based material (Sakamoto Junichi, deputy director of the electronic components division of the Electronic Materials Division of the Electrical and Chemical Industry Electronic Materials Division), it is helpful by adopting the white LED based on this development. To reduce the cost of the final product.
The fluorescent material was sold in October 2009. In addition, the company also decided to invest in the equipment of the Otsuka City Plant in Fukuoka Prefecture, which is a production and development product, and "start a new furnace in 2010" (the executive director of the company and the director of the electronic materials division of the Electronic Materials Division, Yamamoto).
It is estimated that Sharp, which will provide assistance in development, will use the material first. For this material, the Japanese Materials Research Institute has a patent, and the electrical chemical industry has a cooperative relationship with the agency, so it can be sold freely. "The large-scale sales will be launched" (Electrical Chemical Industry), and the first-time sales are expected to reach billions of yen.
The difficulty of this material is the intensity of the luminescence at room temperature. The luminescence intensity is slightly lower than that of the silicate-based material. The company said that it will strive to improve to the same level through improvement. This fluorescent material is added to a material (matrix crystal) in which part of Si crystallized by β-type silicon nitride (Si3N4) is replaced by Al and part N is replaced by O, and Eu (Eu) and Se (Se) which are responsible for light emission are added. Made of rare earth elements. "Using the difference in the bonding force of rare earth ions" (the company's research institute of the Central Research Institute of the Ministry of Science and Technology), the fine-tuning of the rare earth ions around the matrix crystal can improve the luminous intensity.
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