sustainabLED™ is an initiative aimed at embodying Nichia's efforts to reduce environmental impact through its LEDs. Previous blog posts have highlighted initiatives focused on reducing quantity, such as resource circulation and material reduction. This post focuses on LEDs that contribute to the realization of a mercury-free society. By improving performance without the use of hazardous substances, Nichia strives to further reduce environmental impact.

Moving Toward the Replacement of Ultra-High-Pressure Mercury Lamps

The shift from fluorescent lamps to LEDs is a global trend. In Japan as well, the manufacture and sales of fluorescent lamps are scheduled to be prohibited by 2027. Replacing mercury-containing fluorescent lamps with mercury-free LEDs offers a range of benefits, including elimination of mercury, longer lifetime, instant-on capability, and improved energy efficiency.

In industrial applications, ultraviolet (UV) mercury lamps, which operate on the same principle as fluorescent lamps, are widely used. Similar to fluorescent lamps, these UV mercury lamps are now being replaced by LEDs that emit UV rays. This post focuses on the use of UV LEDs as a replacement for ultra-high-pressure mercury lamps, a type of UV mercury lamp.

Ultra-high-pressure mercury lamps are widely used as essential light sources for photolithography applications. In particular, for semiconductor photolithography, high-intensity UV light sources are required to precisely pattern circuits onto semiconductor wafers. Ultra-high-pressure mercury lamps play a key role in this process. As the name suggests, these lamps operate under extremely high pressure, where the discharge is highly concentrated within the lamp. This enables the generation of UV rays with a very small emission area while achieving exceptionally high optical output. Because no alternative technology had been able to provide comparable performance, the RoHS Directive recognizes that suitable alternatives for UV-based photolithography applications have not yet been fully established. As a result, ultra-high-pressure mercury lamps remain exempt from the regulation, allowing their manufacture and sales at least until February 24, 2027.

In semiconductor photolithography, the i-line uses UV energy at 365nm. Although ultra-high-pressure mercury lamps emit a broad spectrum of light, UV wavelengths other than 365nm are filtered out, resulting in unused and wasted output.

On the other hand, UV LEDs are attracting increased attention as an efficient alternative technology with minimal energy loss since they not only do not contain mercury but also emit UV output at a single peak wavelength. However, due to the difference in output, they have not yet been regarded as a direct replacement for ultra-high-pressure mercury lamps, and those lamps continue to be manufactured and sold.

It is often said that if ultra-high-pressure mercury lamps can be replaced by UV LEDs, other types of UV mercury lamps will also be able to be converted to UV LEDs. Given the potentially significant impact on people's daily lives and the environment, Nichia is actively working to advance the development of 365nm LEDs.

Technological Advancements: LEDs Contributing to a Mercury-Free Society

Ultra-high-pressure mercury lamps have long been considered difficult to replace due to the lack of viable alternative technologies. However, Nichia's technological advancements are now steadily overcoming these challenges. Among Nichia's UV-A LED products, the NWSU333 Series offers the highest output, delivering high-intensity UV radiation from a compact package measuring just 6.8mm × 6.8mm. Compared with other Nichia UV-A LEDs, it achieves more than three times higher optical output at their respective rated drive currents. By arranging LEDs at close intervals and utilizing advanced optical technologies to efficiently collect and focus the UV rays, research and development is progressing toward achieving performance comparable to ultra-high-pressure mercury lamp light sources.

Benefits of LED Conversion

LED conversion offers numerous advantages, some of which are outlined below. These benefits extend beyond reducing environmental impact to improving productivity and safety.

Environment & Safety

• Mercury-free: Elimination of hazardous substances and no risk of mercury exposure for workers
• Simplified disposal: No special handling required
• Reduced waste volume: Lower replacement frequency due to longer lifetime

Energy Efficiency & Cost

• Energy savings: Reduced power loss associated with omnidirectional emission and unnecessary spectral output from mercury lamps
• Cost reduction: Lower replacement frequency due to longer lifetime

Productivity & Operability

• Reduced standby time: Instant-on operation
• Improved controllability: Easy output control eliminates the need for mechanical shutters
• Reduced maintenance burden: Longer lifetime decreases replacement frequency, reducing maintenance work and equipment downtime

Design & Equipment

• Simplified power systems: Stable UV output is achieved immediately after power-on, eliminating the need for ballasts
• Compact size: Greater flexibility in equipment design

From these perspectives, it becomes clear that UV LEDs represent an innovative solution that enables both environmental impact reduction and improved industrial efficiency.

Summary

Nichia will continue to focus on developing products that are considerate of the global environment. Step by step, Nichia will advance its efforts toward a sustainable future.