Stream Restoration Project
In line with the Cheonggyecheon stream restoration project, outdoor advertisement renovation projects have been conducted since September 2004, and this required the largest reported quantity of LED modules in Korea’s outdoor advertising industry’s history. Some 3000 outdoor advertisements had been established along the 5.8 km-long shopping district alongside the Cheonggyecheon stream, and of these, some 1400 billboards were removed and replaced with LED channel signs. Most of the replacements were, more importantly, white LED modules. A LED module manufacturer who noted that LED modules supplied to the Cheonggyecheon stream outdoor advertisement renovation projects were all white LEDs said, “The 5.8 km-long shopping district alongside the Cheonggyecheon stream is comparable to a huge exhibition site encompassing all local producers of LED modules for outdoor ads. If these installed LED module-based outdoor ads trigger problems, it will directly lead to the fall of the LED module suppliers and ad sign makers involved.” If problems arise from the manufactured LED channel signs, the module supplier and the outdoor ad maker involved will face the threat of going out of business.

Light Speed Maintenance Rate
One of the criteria for assessing the performance of light sources including LEDs is light speed maintenance rate. The light speed maintenance rate is the measurement of the degree a light source can maintain its initial brightness after light emission versus a later time. If a light source cannot maintain its initial brightness intensity, it is not a good lighting source. Usually, the light speed maintenance rate is tested based on 100 hours and 1000 hours of use, and this is the same for LEDs. As the better the concatenation, the higher the class, the less the difference between the brightness at 100 hours of use and that at 1000 hours is, the better the LED’s quality is. Usually, if the brightness difference falls within 10%, the LED is considered good. In particular, the light speed maintenance rate is important for white LEDs, because white LEDs age faster than other LEDs. Outdoor ads are now manufactured using white LEDs that are more expensive than other light sources. If the luminosity falls by 30 to 40% three months later, this will create an embarrassing situation.

Tremendous Efforts to Develop Technologies
In 2007, two methods to manufacture white LEDS are expected for use in ordinary lighting. As surveyed last month, one method involves coating a blue chip with yellow phosphor, thus producing double-color LEDs. The other method involves combining red, green, and blue LEDs. Importantly, these two methods are the most efficient and have the best potential to spur the growth of white LED manufacturing methods developed thus far, and they are already all patented by foreign corporations. As mentioned in last month’s news article on the U.S. market, Gree, Nichia, Lumiled, Osram, and Toyota Gosei?also called the “Big 5”?are among those that have patented white LED manufacturing methods. They hold cross licenses over their technologies and patents, thereby controlling the global market. A researcher in Korea’s largest LED manufacturing company admitted that, “Any other corporation in the world cannot be free from the said five American companies in terms of double-color LED manufacturing methods.” To shift away from this reality, many local Korean LED manufacturers are exerting tremendous efforts to develop their own technologies in their bid to protect their foothold on the Korean market.
In the 2004 Korea Electronics Show, AUK Co., Ltd., a LED specialist won the Superior Award (given by the Minister of Commerce, Industry, and Energy) in the electronics parts technology category. The company’s white LEDs presented a solution to international patent problems, thus attracting the industry’s attention. Kang Cheong-won, a researcher at AUK, said, “Our technology is to allow blue LED-emitted light to pass through the bottom and lower side of the module structure and mix phosphors, thus creating a white light source and reflecting the light to all sides. This method can use even light consumed for the bottom in the existing white LED, thus improving the luminosity by over 30%.” Unlike existing methods, this method uses the refraction principle inside the chip, and refracts and reflects all light sources from the chip in the head-on direction, greatly improving the luminosity.
White LEDs are envisioned to replace ordinary lighting. To tap the global lighting market currently estimated to be worth KRW 70 trillion, local and overseas LED companies are striving to join in the fray. If in 2007, white LED lighting appliances are commercialized, the markets of outdoor advertisements and ordinary lighting can expect formidable challenges or opportunities.