Source: Institute of source material of Nanjing University of Technology: Wang Haibo Zhang Ricci
The traditional lighting technology is developed on the basis of electric vacuum technology. Due to the development of semiconductor technology, the electronic components of the electron tube are gradually replaced by transistors. Like transistor components, solid-state lighting products offer significant advantages over traditional lighting products. With the increasing demand for energy-saving and environmentally-friendly lighting, white LEDs are rapidly developing worldwide. China is one of the countries with relatively complete development of the LED industry chain. The application of LED is at the forefront of the world.
Under the current technical conditions, there are four main methods for the realization of white LEDs: one is to apply yellow phosphor to the blue chip; the other is to apply three primary color phosphors to the ultraviolet chip; the third is to combine the three primary color chips; the fourth is the ZnSe chip. Independent illumination. At present, the highest luminous efficiency and the highest degree of commercialization are products using a blue chip to coat yellow phosphors.
As companies such as Nichia and Osram started earlier in this field, R&D work was more systematic, and monopoly and patent blockade were formed in the field of white LED. If China's semiconductor lighting industry can't get out of the new road of independent intellectual property rights, it will repeat the mistakes of China's DVD industry.
To break through the patent blocking of foreign white LEDs, it is necessary to make breakthroughs in the realization of the technical route or key materials. According to the National Semiconductor Lighting Engineering R&D and Industry Alliance statistics, most of the patents applied in China's semiconductor lighting field belong to the downstream technology of the industrial chain. Due to the difficulty in finding "new epitaxial materials" with practical value, it is difficult to develop breakthrough materials with independent intellectual property rights in a short period of time.
Phosphor material becomes an effective way to break through patent barriers
Among the four methods implemented by the white LED, the first two methods are obtained by exciting the phosphor material through a non-white light chip, and then obtaining white light after light conversion and mixing. Among them, "Blu-ray chip coated yellow phosphor system" can obtain the white LED products with the highest luminous efficiency and the highest degree of commercialization. Therefore, the phosphor material has become one of the key materials that affect the main indicators of white light LED luminous efficiency, service life, color rendering index, light color temperature and other light sources.
Companies such as Nichia and Toyota Synthetic started earlier in the field of white LED phosphors, and their R&D work is relatively systematic. They all have very mature phosphor production technology. On the basis of early technology accumulation, large companies such as the US and Europe have also formed. With its unique phosphor system and technology; with the industrial transfer, the spread of technology and the early accumulation of electronic technology, Taiwan has sprung up in the LED field in the past 10 years, and has formed a chip represented by TSMC, Yiguang and other companies. Production companies and phosphor manufacturers represented by Hongdae have a certain market share in the mainland market. At present, the phosphors used by most packaging manufacturers in mainland China are imported from Taiwan.
In recent years, many domestic manufacturers have also engaged in research in this area, and have occupied some markets, such as: Beijing Nakamura Yuji, Beijing Nonferrous Metals Research Institute, Nanjing University of Technology Electric Light Source Materials Research Institute, Suzhou intematix, Dalian Luming, Changshu Jiangnan, etc., they have achieved remarkable results in nitride red powder, aluminate and silicate yellow powder. Some products even exceed Taiwan's products, and their technology is close to the world advanced by Japan. Level, this is very beneficial to improve the lighting performance and cost reduction of LED products in China.
Due to the diversity of chemical elements and the diversity of chemical reactions, the use of new phosphor materials will become a more realistic road for China's white LED industry to break through foreign patent barriers in the short-term failure of patent manufacturing technology to break patent barriers. Osram has used TAG instead of YAG to effectively circumvent Nichia's patent restrictions and win the IPR litigation with Nichia, becoming a successful case of breaking through the patent barriers of Nichia.
In addition, China has a unique advantage - rich in rare earth resources. According to statistics, China's rare earth reserves account for 60% of the world's total output, accounting for more than 80% of the output, and the variety is complete, can provide a variety of raw materials for phosphor research and production, such as Y, Eu, Ce, Tb, etc. It is unmatched by Japan, South Korea and other countries.
Therefore, the development of new phosphor materials in China is likely to become the most effective way to break through the foreign blockade. The development of domestic phosphors needs to take the road of independent innovation
Although China's phosphor technology has made great progress and formed a mature product, it is still based on imitation, and there is no legal barrier to avoid foreign patents.
Under this circumstance, the development of domestic phosphors should focus on the following aspects: first, the development of phosphor preparation and post-treatment technology; second, the development and coating technology of new phosphor systems. The third is to seek overall optimization and leading indicators through joint research in the upper, middle and lower reaches of the industrial chain.
The Institute of Electric Light Source Materials of Nanjing University of Technology has also carried out effective exploration in this regard. Through the joint research with epitaxy, chip, silica gel, packaging and other units, the development of a red powder material with tungsten molybdate with independent intellectual property rights, the phosphor can be better matched with the blue chip and effectively packaged with YAG phosphor. , to achieve the purpose of reducing color temperature and improving color rendering. A new process for prefabricated phosphor coating has been developed to improve the matching of phosphors with chips and the heat resistance of phosphors. The light efficiency of white LED produced by domestically produced main materials exceeds 100 lumens per watt, and the cost of light source is less than 6 cents per lumen. The main indicators have reached the international advanced level.
Phosphor coating light conversion is currently the main way to manufacture white LEDs. In this method, the role of phosphor as a light conversion substance is crucial, and it directly affects the main indicators of white LED products. With the breakthrough of LED chip technology, LED luminous efficiency will gradually approach its theoretical luminous efficiency, and the performance of fluorescent powder will directly determine the product performance of LED light source. At present, there are not many phosphors capable of matching blue light, near-ultraviolet light or other chips, and it is necessary to develop a phosphor with high luminous efficiency, long service life, high color rendering index, more stable physical and chemical properties, and simpler preparation process.
Due to the diversity of chemical substances, it is possible to develop original innovative technologies in the field of phosphors and form patents for independent innovation, thus breaking the foreign patent blockade and embarking on a road of China's own white LED industrialization.
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