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Deep-UV LEDs attracting attention about water disinfection

Leading UV light field with high-output products that hold the key to market expansion

Stanley Electric's high-power Deep-UV LEDs have attracted a great deal of attention, especially in the hygiene field.
Stanley achieved the highest output power in the field (50 mW) emitting at 265 nm, optimal for sterilizing water.
This is because the possibilities of expanding Deep-UV light applications to equipment such as water purification devices have further increased.
The company is pursuing an even higher light output by making full use of technologies, materials and processes that have been cultivated with visible light LED and IREDs for many years. Their idea is to accelerate the development of Deep-UV LEDs' new market.

Toru Kinoshita

Stanley Electric Co., Ltd.
R & D Center Chief Engineer

A Deep-UV LED is an LED that emits light in the wavelength range called "UV-C" (100 to 280 nm). Currently, the development of Deep-UV LEDs is becoming particularly active. This is because the demand for Deep-UV LEDs has increased dramatically as an alternative device to replace mercury lamps, which have been the main light sources used for UV light application equipment such as sterilization equipment.

Deep-UV LEDs have a superior advantage compared to mercury lamps, such as small size, high efficiency, zero warm-up time. For this reason, as a general view in the UV light field, mercury lamps will replace LEDs in a natural transition. While LED device manufacturers focus on accelerating the development of Deep-UV LEDs, new entries from other fields such as materials / material manufacturers and precision pump manufacturers are appearing one after another.

In this situation, one LED maker that is showing a strong presence is Stanley Electric. "We have been consistently working on light technologies since the beginning of our company; we have been developing LEDs since the 1960's and have accumulated abundant technologies and know-how on LEDs" (Toru Kinoshita, Chief Engineer, R & D Center). In addition, in January 2017 Stanley Electric entered into an agreement with Tokuyama (a company dealing with chemicals and electronics materials), which handed over its Deep-UV LED technology and equipment; Stanley Electric further strengthened its Deep-UV LEDs' technology development.

Number one provider of highly-demanded 265 nm wavelength

The latest result announced by Stanley Electric in May 2017 is a Deep-UV LED with an output of 50 mW emitting at 265 nm (Fig. 1); the company has already established mass production technology, and plans to start mass production in 2017. Several companies have commercialized Deep-UV LEDs emitting 265 to 285 nm, with output power of 20 to 75 mW. However, Stanley Electric's Deep-UV LEDs boast the most powerful light output among the 265 nm wavelength products, which currently is the most promising application for water disinfection. "Where chlorine disinfection is ineffective, the wavelength that is effective for sterilization of pathogenic microorganisms ("Cryptosporidium") in water is 265 nm (Fig. 2). Mercury lamp sterilization systems have already been adopted in water purification facilities in Europe and the United States in advance. Recently it has been adopted in water purification plants in Japan. The first Deep-UV LED market is driven by small and medium type water sterilization system applications and ― in the future ― the replacement of light sources on large scale water sterilization systems (such as water purification facilities) is to be expected" (Mr. Kinoshita).

Fig. 1: High-output Deep-UV LED emitting at 265 nm; light output of 50 mW

High-output Deep-UV LED photo
Item Specifications
Wavelength 265 nm
Light output 50 mW
Forward current 400 mA
External quantum efficiency 2.6 7%
Forward voltage 8. 8V
Light distribution angle 140 °
Package size 3.5 × 3.5 mm
*Specifications are subject to change without notice.

Fig. 2: Deep-UV light emitting at 265 nm, effective for sterilization of the pathogenic microorganism "Cryptosporidium"

Deep-UV light emitting at 265 nm effective for  sterilization of the pathogenic microorganism Cryptosporidium

For Deep-UV LEDs, the biggest challenge in order to replace mercury lamps is light output, on which the market is focusing. In fact, Deep-UV LEDs possess many excellent features over conventional mercury lamps, but at present the output is much lower. The light output of mercury lamps is usually 1 W or more, while for Deep-UV LEDs amounts only to dozens of mW ― it is off by a digit. As technology development progresses and output increases, new applications expand as mercury lamps replacement progresses. This is why Stanley Electric's Deep-UV LED gained attention from the UV field for its world-class high output.

The company's key efforts to establish Deep-UV LED mass production technology with superior characteristics ahead of time are mainly two; both are countermeasures to technical problems peculiar to Deep-UV LEDs, which hinder high output.

Two countermeasures to the problems that hinder high output