Development of World’s First High-Luminous-Energy LED Lighting Unit for Grain Growth


USHIO LIGHTING, INC. (USHIO LIGHTING), Showa Denko K.K. (SDK) and Chiba University have jointly developed the world’s first* 1 high-luminous-energy LED lighting unit suitable for cultivation of rice and other types of grain. The unit has been put into operation at Chiba University’s facilities.

The unit uses SDK’s 660-nm-wavelength red LED chips that promote plant’s photosynthesis and blue LED chips that help morphogenesis. The unit is also based on USHIO LIGHTING’s LED heat dissipation/packaging and optical design technologies. Due to the combination of the two companies’ proprietary technologies, the unit is characterized by its high output and high heat dissipation.

The unit has been introduced into research facilities of Professor Eiji Goto, Graduate School of Horticulture, Chiba University, and optimized for grain growth under his guidance. The university has started experiments, using the newly developed LED lighting unit, in cultivating fruit vegetables (tomatoes, etc.) and grains (rice, etc.) that require a large quantity of light.

Characteristics of the new “high-luminous-energy LED lighting unit”

higher ampere and fewer LED chips

Due to the use of proprietary LED packaging/heat dissipation and optical design technologies, we have succeeded in using LED chips at high levels of ampere that was not possible before, and in reducing the number of LED chips to be used. As a result, we have achieved photon flux density of approx. 1,000 µ mol · m-2 · s-1 (micromole per square meter, per second) at the irradiation distance of 20 cm, despite the fact that the unit uses only around 2,500 LED chips.

World’s first technology

It is the first time in the world that such a high photon flux density (approx. 1,000 µ mol · m-2 · s-1) has been achieved for a large area of approx. one square meter. This LED lighting unit is not only at a laboratory level: it can be used on a commercial scale.

Proprietary LED packaging/heat dissipation technologies

We have adopted a new specialty substrate with high heat conductivity, and directly packaged ultrabright LED chips on the substrate. This structure has enhanced the level of heat dissipation for this lighting unit. Although an air-cooling system is adopted, the rise in temperature of LED chips has been reduced substantially. If no heat dissipation measure is taken, the temperature of LED chips, put into operation at 100 mA, rises from room temperature to nearly 200° with the lapse of time. However, this unit can restrict the temperature of LED chips to 50° or lower, regardless of the duration of chips’ light emission.

Proprietary optical design technology

This unit fully utilizes technologies and know-how regarding optical design and light distribution simulations accumulated by USHIO LIGHTING, a specialist in lighting. To realize the full potential of ultrabright LED chips used, we have attached a lens, a condenser lens, and a reflector to each LED chip. We have also conducted special simulations to reduce light leakage and to ensure efficient emission from LED chips.

High photon flux density

Because of the higher heat dissipation efficiency, it has become possible to avoid adverse factors caused by heat, such as deterioration of LED chips, and decline in emissive efficiency and life. Thus, we have achieved a high photon flux density of approx. 1,000 µ mol · m-2 · s-1 (a level required for rice cultivation) at the irradiation distance of 20 cm with an approx. one-square-meter lighting unit.

This opens up the possibilities of cultivating fruit vegetables, beans, grains or potatoes under artificial light. Furthermore, the new LED lighting unit can be used to meet diversified market needs for plant growth. Demand for plant growth facilities is expected to increase, reflecting the public awareness of food safety and the need for improving the food self-sufficiency rate. Demand for LED lighting will also increase as the key element of the plant growth facilities, owing to its ability to control lighting and to provide optimized light necessary for plant growth.

USHIO LIGHTING will use this heat dissipation technology and expand its applications to many other areas. The company expects to grow the business to 300 million Yen in fiscal 2011, including sales in related areas.

*As of October 2010, to the best of our knowledge.
*Photon flux density: The number of photons in the 400-700 nm area per second, per square meter. As for foliage vegetables, often cultivated at plant growth facilities, it is generally said that the level of photon flux density should be around 150-200n µ mol · m-2 · s-1.

Professor Goto’s comment

First of all, the number of LED chips used in this unit is surprisingly small. To realize the photon flux density of (approx. 1,000 µ mol · m-2 · s-1) with such a small number of LED chips, various technologies are utilized. Besides, due to the use of an air-cooling system, the unit is compact despite the fact that it gives high luminous energy. Thus, we can put this unit at any place we like for experiment, and we can use it in a multistage cultivation system as well. When strong light (equal to sunlight) is necessary for environment control rooms or plant growth equipment, high-pressure sodium lamps or metal halide lamps have been used in the past 30-40 years. However, those lamps present such problems as the rise in plant temperature due to emission of much infrared, and low uniformity in light intensity on the illuminated area because of the use of point light sources. The newly developed unit has resolved those problems. It is a breakthrough that will enable the cultivation of fruit vegetables, beans, grains and potatoes under artificial light. As LEDs can produce a wide variety of light quality, I will aim to identify optimum lighting environment for plant growth and use the know-how for commercial plant growth facilities. Artificial light sources are also used in mushroom cultivation, pest insect control, aquaculture, fishery, and livestock. With the successful development of this lighting unit, I hope LEDs will be used increasingly in agriculture, forestry and fisheries.

Rice cultivation experiment.


red-blue LED

red LED

blue LED



USHIO LIGHTING, INC., headquartered in Tokyo, was established in 1963. A member of the USHIO Group, the company operates mainly in the areas of illumination and images. It provides lamps, LEDs and image/illumination devices for commercial facilities, stages, studios, and halls. It also produces and sells illumination devices for marine/security/display applications. In the industrial sector, the company sells precision exposure systems, plastic molding/treatment systems, and food packaging systems. The company’s operations are based on an integrated business model, covering all stages from light sources to illumination/image systems. Furthermore, the company provides maintenance services, and has established a position of a total solution provider by expanding businesses in production, software and contents. The company, with 357 employees, recorded sales of approx. 9.1 billion Yen in the fiscal year ended March 2010.

Showa Denko K.K.

Showa Denko K.K. (headquartered in Tokyo, Tokyo Stock Exchange 4004) was established in 1939 through the merger of Showa Fertilizers K.K., which became the first in Japan to produce ammonia based on domestically developed technology, and Nihon Iodine K.K., which pioneered in the commercial production of aluminum in Japan (company name changed to Nihon Electrical Industries K.K. in 1934). SDK began with electrochemistry by fully utilizing hydraulic power, Japan’s valuable resource. The company successively launched various chemical products based on domestically developed technologies. Through integration of various materials and technologies derived from electrochemistry, the company now offers individualized products in many fields, including petrochemicals, chemicals, inorganics, aluminum and electronics.  In the area of hard disk media (a major component of hard disk drives, used as data storage device in PCs, etc.), SDK has the largest share on the global market as an independent supplier. The company also provides ultrabright LED chips (used in LCD TVs as backlight, next-generation lighting, and plant growth facilities), and lithium-ion battery materials, including anode materials already adopted in electric vehicles. The company, with 11,564 employees on a consolidated basis, recorded sales of \678.2 billion in the fiscal year ended December 2009.

Chiba University

Chiba University’s Graduate School of Horticulture has long been engaged in the relevant research: for about 50 years in the sunlight type greenhouse, and for more than 20 years in the artificial-light type plant factory. Since 2009, the university has been conducting a “plant growth facility research center” business with the support of the Ministry of Economy, Trade and Industry. The university has expanded plant growth facilities for research at its campuses in Matsudo and Kashiwa-no-ha, aiming to establish its status as a leading research organization in this area and to promote industrialization of Japanese agriculture.


USHIO, INC. (headquartered in Tokyo, Tokyo Stock Exchange 6925) was established in 1964. The company deals in discharge lamps for use in exposure equipment, cinema projectors, and data projectors. It also supplies halogen lamps for various types of illumination equipment and OA equipment. The company also produces and sells various optical devices containing its own lamps. It enjoys high market shares for many of its products. The company, with around 4,700 employees on a consolidated basis, recorded sales of 119 billion Yen in the fiscal year ended March 2010.