The four common UV LED bands look almost identical on a datasheet and behave very differently in production. Choosing the wrong one is the single most common reason a new lamp “doesn't cure as well as the old one”.
365 nm
The shortest of the mainstream bands and the highest-energy option. It suits clear coatings, optical adhesives and formulations built around a 365 nm photoinitiator. Deep penetration on clear films is good. The trade-offs: lower wall-plug efficiency than 395 nm (more heat per unit of UV) and a shorter LED lifetime.
385 nm
The usual compromise for industrial printing. Many UV flexo, offset and inkjet inks are formulated to work across 385–395 nm, and 385 nm gives better through-cure on pigmented films than 395 nm.
395 nm
The workhorse. Highest efficiency, longest life, lowest cost per watt of the four, and the band most ink makers design around today. If your ink datasheet says “395 nm” and your substrate is not heat-sensitive, this is usually the right answer.
405 nm
Visible violet, gentlest on heat-sensitive substrates and commonly used in 3D printing resins and some adhesives. Penetration through white or filled coatings is weaker, and some operators find the visible glow distracting.
How to decide
- Start from the ink or adhesive datasheet — the photoinitiator's absorption peak decides it
- If the datasheet lists a range, default to the shortest wavelength in that range for through-cure
- If the substrate is thin film or veneer, consider stepping up to 405 nm and raising dose instead of irradiance
- If you run several inks, ask whether a dual-wavelength head is cheaper than two machines
Wrong wavelength cannot be fixed by turning up the power. Match it first, then size the head.
