Introduction to UV LEDs: Differences from Mercury Lamps, Safety, and Applications | NEXTY Electronics, an Electronic Components and Semiconductor Trading Company

For engineers considering introducing UV LEDs, do you have concerns such as "I don't know the difference between this and mercury lamps" or "I'm concerned about safety and the latest technology?"
In this column, we will provide an easy-to-understand explanation of everything from the basics of ultraviolet (UV) to the differences between UV LEDs and mercury lamps, how to use them safely, and the latest technological trends.

This column is recommended for the following people:

Those who want to learn the basics of UV LEDs
Those who want to know the difference between mercury lamps
Anyone interested in the safe use of UV technology and the latest trends

Understanding UV LED basics, applications, and safety precautions will help you choose the best UV technology for your application.

1. What is ultraviolet (UV) light?

1.1 UV-A / UV-B / UV-C

Ultraviolet (UV) rays are a type of electromagnetic wave with shorter wavelengths than visible light and higher energy.
It is also called UV, which is an abbreviation of "UltraViolet."
Ultraviolet rays generally have wavelengths between 100 and 400 nm and are mainly classified into three types:

UV-A (315-400nm): The longest wavelength of ultraviolet light and has the lowest energy. It mainly affects the surface of materials.
UV-B (280-315 nm): It has more energy than UV-A and affects skin tanning and plant growth.
UV-C (100-280nm): UV light has the shortest wavelength and the highest energy, making it a powerful sterilizer.

The "solar spectrum" refers to the wavelength distribution of light emitted from the sun.
The Earth's ozone layer absorbs most of the UV-C and UV-B rays. Therefore, the main component of ultraviolet rays that reach the Earth's surface is UV-A (see Figure 1).

Figure 1: Solar spectrum and UV components reaching the earth's surface

1.2 Effects of ultraviolet rays on materials

Ultraviolet rays have high energy and have a variety of effects on materials, including chemical changes and deterioration.

1. Accelerating chemical reactions
Ultraviolet light activates molecules and causes chemical reactions, a property that is utilized in resin curing and printing technologies.

2. Bactericidal action
UV-C in particular destroys the DNA of microorganisms and has a powerful sterilizing effect in medical and air conditioning equipment.

3. Discoloration and deterioration
Ultraviolet rays are one of the main factors that cause the deterioration and degradation of plastics and dyes.

2. Main uses of ultraviolet light

Ultraviolet rays are used for a variety of purposes, including sterilization, hardening, and medical treatment, depending on their wavelength.

Uses of UV-A

It is used in curing resins for 3D printers, exposing circuit board registers, preventing counterfeiting of banknotes, and UV-curable inks.

Figure 3: Anti-counterfeiting technology for banknotes

Uses of UV-B

It is used to improve plant disease resistance and environmental tolerance, and to treat skin diseases (phototherapy).

Figure 4: Improving plant disease resistance

Uses of UV-C

It is widely used for hygiene management, such as sterilizing drinking water and air, disinfecting the surfaces of medical equipment and facilities, and sterilizing the inside of air conditioning equipment.

Figure 6: Disinfection of drinking water

Taking advantage of its high energy, ultraviolet light is widely used for sterilization and curing purposes in the medical, food, and manufacturing fields.

3. Structure and Features of UV LEDs

3.1 UV LED structure

There are two main types of ultraviolet light sources: semiconductor elements (UV LEDs) and arc discharge systems (such as mercury lamps).
Here we will explain the structure and materials used in UV LEDs.
UV LED chips use different materials for each emitted wavelength.

UV-A: GaN and AlGaN materials
UV-B/UV-C: AlGaN-based materials

The structure of a UV LED is similar to that of a regular LED.
However, UV rays can cause resin to deteriorate, so UV-resistant materials such as glass or CERAMICS are used for packaging.

3.2 Features of UV LEDs

UV LEDs have the following characteristics:

Instant on/off: No warm-up time required
Easy to miniaturize: Saves space and improves design flexibility
Wavelength selectable: Select the wavelength that best suits your application
Reduced environmental impact: Mercury-free and environmentally friendly

3.3 The importance of UV LED wavelength and radiant flux

By selecting the optimal wavelength for each application, you can maximize the effectiveness of ultraviolet light.

For example, wavelengths around 365 nm are effective for resin hardening, and wavelengths around 265 nm are effective for sterilization.

Even if the radiation flux is high, the reaction efficiency will be reduced if the wavelength is not appropriate.
It is important to select a UV LED that has both a wavelength suitable for the application and sufficient radiant flux.

4. Comparison of UV LED and mercury lamp

Mercury lamps have been used as ultraviolet light sources for many years.
In recent years, UV LEDs have been attracting attention for their environmental friendliness and are rapidly becoming more popular.
Table 1 summarizes the main differences between the two based on UV-C LEDs.

Table 1: Comparison of UV LED (UV-C) and mercury lamps

	UV LED	Mercury lamp
Light-emitting principle	Semiconductor Light Emission	Mercury vapor discharge
Luminous efficiency	Approximately 3 to 5% (Improved every year)	Approximately 20-40%
price	expensive (declining trend)	Inexpensive
Responsiveness	Instant on/off	slow (Warm-up required)
Dimensions	Can be downsized	large
Environmental load	Mercury free	Use of mercury
Wavelength selectivity	Specific single wavelength	Broad Spectrum

Mercury lamps are still superior in terms of luminous efficiency and cost.
On the other hand, UV LEDs have many advantages, such as fast response, compact size, reduced environmental impact, and wavelength selectivity.
In particular, from 2021, the manufacture, import and export of mercury lamps for general lighting will be prohibited.
This is accelerating the transition to UV LEDs.
Mercury lamps for ultraviolet light are currently not subject to regulation.
However, regulations may be tightened in the future.

5. UV Safety and Proper Use

Ultraviolet rays are high in energy and can have adverse effects on the human body, including on the skin and eyes.
UV-C in particular has a strong sterilizing effect, but it can also cause dermatitis and keratitis even after a short exposure.
To use UV rays safely, it is important to take the following precautions:

1. Wear UV protective glasses
To protect your eyes from UV rays, be sure to wear protective glasses with UV protection.

2. Wear long sleeves and gloves
Wear long sleeves and gloves when working to prevent direct exposure to the skin.

3. Preventing skin exposure
Design your work area and equipment to block UV rays from reaching your skin.

4. Light-shielding cover and interlock mechanism
To prevent UV rays from leaking, install a light-shielding cover or safety interlock mechanism on the equipment.

6. Latest Technology Trends and Future Prospects

Improving the luminous efficiency and reducing costs of UV-A, UV-B, and UV-C LEDs have been long-standing challenges, but recent technological innovations have led to significant improvements.
Demand for UV-C LEDs in particular is rapidly increasing for sterilization and disinfection applications in medical equipment and air conditioning equipment, and the market size is expanding.
Going forward, improvements in luminous efficiency and reductions in manufacturing costs are expected to further accelerate the replacement of mercury lamps with UV LEDs.
In addition, advances in UV wavelength control technology have improved the precision of curing and sterilization processes.
This is expected to lead to applications in a variety of fields, including medicine, food, and electronic component manufacturing.

7. Summary

Ultraviolet (UV) rays are classified into three types: UV-A, UV-B, and UV-C.
In addition, because it has higher energy than visible light, it is used in a variety of fields, including hardening and sterilization.
Mercury lamps, which have been the mainstream up until now, are being replaced by UV LEDs due to their reduced environmental impact, safety, and compact size.
By understanding the basics of the solar spectrum and ultraviolet light, as well as the characteristics and safety precautions of UV LEDs, you can use ultraviolet technology effectively and safely.
We offer UV LED products tailored to your needs. If you are interested, please feel free to Inquiry.