The UV curing spectrum ranges from 200 nm to 400 nm wavelength, and different wavelengths within this range are suitable for curing different types of products. Some of the key wavelengths and their applications include:
- • 365 nm (UVA): UV radiation at 365 nm has longer wavelengths and lower energy, so it penetrates deeper into materials. It is good for thick, multi-layered products like 3D prints, laminations or coatings on uneven surfaces. 365 nm UV also post-cures other UV wavelengths by providing broad exposure through the depth. Some photoinitiators can be cured specifically by 365 nm UV.
- • 385 nm (UVA/UVB crossover): 385 nm UV falls at the crossover point between UVA and UVB wavelengths. It has moderate penetration like UVA but faster curing ability than UVA, making it useful for a range of mediums from thin to thick. 385 nm is suitable for most UV-curable inks, coatings, adhesives and resins. Many UV curing lamps and LEDs emit around 385 nm.
- • 395 nm (UVB): UVB radiation peaking at 395 nm has good balance of moderate penetration and reactivity for curing many common UV-sensitive materials. It works well for curing solvent-based inks, coatings, adhesives and resins. 395 nm UVB can penetrate up to 500 micrometers in certain materials. Some photoinitiators have strong absorbance in the 395 nm range.
- • 405 nm (UVB): UVB at 405 nm has higher energy than 395 nm so it cures materials slightly faster and with higher intensity. However, its penetration is not significantly different. 405 nm UVB is often used where very fast, forceful curing is needed, such as for UV-curing 3D printed fine details. It can produce more rapid free radical generation for initiating cure.
- • 450 nm (longwave UVA): UV radiation at 450 nm falls at the longer end of the UVA range. It has the deepest penetration of any UV wavelength but slower curing ability. 450 nm UVA is useful for post-curing UVB or UVB/385 nm exposed surfaces to achieve a high degree of cure throughout the depth without damaging the surface. It can also cure materials with certain yellowing-resistant photoinitiators that absorb longer UVA wavelengths.
In summary, UV Curing at different wavelengths targets different types of products and applications. Selecting a wavelength (or combination) that closely matches a material’s UV absorption characteristics will enable the best results. UVA at 365 nm for thick parts, 385 nm for a range of mediums, UVB 395-405 nm for solvent inks/coatings, and UVA 450 nm for post-curing are some of the most useful wavelengths, but other wavelengths may suit specific needs. With an understanding of each wavelength’s properties, the optimal UV cure can be found for any product.
- • 365 nm UVA – For deepest penetration and post-curing. Slower cure speed.
- • 380-390 nm – Provides good balance of penetration and cure speed for many UV materials.
- • 395-405 nm (UVA/UVB crossover) – Enables fast, deep cure with excellent flexibility.
- • 365-405 nm broad UVA – Combines all UVA wavelengths for maximum depth, speed, flexibility and quality.