| Ink Migration |
|
| UV-curable inks and coatings have seen continuous growth in application over the past 30–40 years due to their advantages such as reduced emission of volatile organic compounds (VOCs) and rapid curing. A key component in the formulation of UV-curable inks and coatings is the photoinitiator—a highly photoactive compound capable of initiating rapid polymerization upon absorbing energy from specific wavelengths of light. However, since the year 2000, the phenomenon of photoinitiator migration has been increasingly detected in various food packaging materials. One of the most notable incidents occurred in 2005, when infant milk was recalled in Italy. Reports indicated that the contaminated milk originated from the Spanish plant of a major international food company. Testing revealed that a photoinitiator, commonly referred to as ITX, had migrated from the packaging into the milk, resulting in contamination. This incident subsequently triggered further recalls of the product in neighboring countries. |
 Typical milk packaging and printing |
| Three Typical Migration Pathways of Ink into Packaging Materials |
||||
| Diffusion Migration | Set-off | Gas-phase Transfer | ||
| Ink components directly diffuse through the packaging material. | Ink components transfer due to contact between printed and unprinted surfaces (e.g., during stacking or winding). |
Volatile ink components evaporate and then re-condense on the food-contact side of the packaging. | ||
 |
 |
 |
||
| Low Migration |
| During the stacking or winding process after printing, ink components can transfer from the printed surface to the inner side (i.e., the food-contact surface). Additionally, volatile substances in the ink may penetrate the packaging interior via the air. For reasons of food safety, reducing material migration has become a central topic in both research and industrial development. On the materials side, efforts can be made by modifying the formulation of inks or coatings, or by improving the packaging substrate. On the process side, optimizations can be achieved through printing equipment or processing parameters. A direct and intuitive solution is to reduce or eliminate photoinitiators in the formulation. Electron beam (e-beam) curing, which initiates polymerization and crosslinking through high-energy bond breakage, has emerged as an effective alternative. However, the high cost of e-beam equipment remains a significant barrier for many manufacturers. |
| New Technology: DirectCure |
| DirectCure is an innovative technology developed in recent years. It utilizes medium-pressure gas discharge lamps to emit high-energy radiation in the 190–220 nm wavelength range. Under an inert atmosphere filled with nitrogen, the UV radiation directly excites acrylate molecules, generating free radicals that trigger polymerization and crosslinking of inks or coatings — without the need for traditional photoinitiators. Using DirectCure UV for in-line curing or post-curing provides a simple and cost-effective solution for producing low-migration printed materials. Experiments have demonstrated that the migration levels achieved with DirectCure are comparable to those obtained with e-beam curing. |
 |
| Advantages of DirectCure |  |
|
|
| Improved Performance with DirectCure Curing | |
|
|
| Formulation Benefits | |
|
| PrintConcept & IOT |
| PrintConcept, a wholly owned subsidiary of Dr. Hoenle AG in Germany, has been providing UV curing systems for roll-to-roll offset and flexographic printing since 1995. The company is particularly known for its inert atmosphere and low migration solutions. IOT, founded in 1998, specializes in surface treatment technologies including UV, plasma, and ion beam applications. Together with PrintConcept, it offers eco-friendly UV curing systems, with DirectCure already successfully installed at numerous production lines worldwide — especially in food packaging applications. |
 |
版權所有 © 展締科技股份有限公司. All Rights Reserved.
