UV-LED Wavelength Classification

UV-LED Wavelength Classification

Table of content.

1. Concept of Wavelength

The electromagnetic spectrum is arranged by wavelength from short to long as follows: cosmic rays, gamma rays, X-rays, ultraviolet rays, visible light, infrared, microwaves, and radio waves. Ultraviolet (UV) light is defined by the International Commission on Illumination (CIE) and is further divided by wavelength into four types:

  • UVV: 395–450 nm
  • UVA: 320–395 nm
  • UVB: 280–320 nm
  • UVC: 200–280 nm

In UV curing technology, photoinitiators are added to coatings, inks, adhesives, and other materials. When exposed to UV light, these photoinitiators are activated to initiate photochemical reactions, causing coatings, inks, or adhesives to cure. This curing method is fast, efficient, and environmentally friendly, making it widely used in printing, coating, and bonding applications.

Each UV category has a different wavelength range, which determines its penetration depth into substrates:

  • UVV: A visible-range UV wavelength used for curing silver pigments, titanium dioxide, and improving adhesion.
  • UVA: A long-wave UV used for deep-layer curing and strengthening adhesion and bonding.
  • UVB: A mid-wave UV capable of deeper penetration, providing coating and bonding toughness.
  •  UVC: A short-wave UV used for surface curing, producing surface hardness and abrasion resistance.


2. Applications of Different UV Wavelengths


① UVC (100–280 nm)


UVC is almost completely absorbed by air due to its very short wavelength. In UV printing, UVC enhances the surface hardness of ink films. Recently, nitrogen-purging UV printing methods have been used to reduce ozone generation from UVC and allow its full energy to contribute to polymerization and curing. Although this method is more costly, it maximizes curing efficiency.


Main applications of UVC include:

  • Transparent coatings on paper and plastic surfaces
  • Hard coatings for optical and automotive lenses
  • Disinfection and sterilization
  • DNA crosslinking
  • Surface modification

② UVB (280–320 nm)

UVB is known as the most biologically damaging UV wavelength. It carries enough energy to harm biological tissue and cause skin cancer. With the depletion of the ozone layer, limiting exposure time has become increasingly important.

In UV inks and UV printing, UVB generally plays no significant role; therefore, UV lamps for UV printing rarely utilize this wavelength unless specifically required.

Main applications of UVB include:

  • Curing coatings, adhesives, and inks
  • Sterilization
  • Disinfection

③ UVA (320–395 nm)

UVA is the most harmless and most common UV wavelength. It has the lowest energy and is known as “Black Light” or near-UV. It is often used for fluorescence excitation. In UV ink curing, UVA provides the highest polymerization efficiency and is widely used to measure UV lamp aging.

UVA is used in general UV curing and mainly affects adhesion performance in UV formulations.

Common applications of UVA include:

  • Curing inks, coatings, and adhesives
  • UV inspection
  • UV fluorescence

④ UVV (395–450 nm)

UVV is within the visible wavelength range. It cures the deepest layers and is responsible for adhesion performance within UV formulations. UVV performs particularly well when curing white pigments, silver conductive pigments, and titanium dioxide.

Common applications of UVV include:

  • Silver conductive inks
  • Titanium dioxide-based coatings
  • Adhesives and deep potting compounds






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