Printing on film-based self-adhesive materials can present challenges, and ink bleed is a common problem encountered by print manufacturers. Ink drop refers to the poor firmness of the printed ink layer on the surface of the material due to factors such as low surface tension, insufficient UV curing, and excessive ink additives. Severe printing ink loss not only affects product quality, but even leads to scrapping of batches of products. In this article, we will explore the top three causes of ink bleed on printed film self-adhesive materials and provide effective solutions to overcome this problem.
1. Low surface tension of film materials
One of the main reasons for the ink droplets on printed film-based self-adhesive materials is the low surface tension of the film. Generally speaking, the higher the surface tension, the better the ink fastness after printing. There is no problem with the surface tension of most paper-like materials, but the surface tension of film-like materials is often uneven. This low surface tension can lead to poor ink adhesion, which can lead to reduced ink droplet and print quality. If there is ink loss during the printing process, you can use a dyne pen to test the surface tension value of the material. Generally speaking, materials with a surface tension lower than 38 datones are prone to ink loss. To resolve this issue, consider the following solutions:
A. Surface treatment: implement the surface treatment process to enhance the surface tension of the film material. This can be achieved by corona treatment, flame treatment or plasma treatment, which can change the surface characteristics, increase wettability and promote ink adhesion.
B. Primer coat: Apply a suitable primer coat to the film material prior to printing. Primers help create a bond between the ink and the surface of the material, improving ink adhesion and reducing the chance of ink dripping. Consult your coating supplier to select a suitable primer that is compatible with the film material and ink formulation. Some professional label printing companies will also directly use coated PET self-adhesive materials for printing. The coating changes the surface wetting characteristics of PET self-adhesive materials, and the performance is stable, and the firmness of the ink layer can be effectively improved.
2. Insufficient UV curing
Insufficient UV curing will also lead to ink droplets when printing film-type self-adhesive materials. Incomplete curing will result in an ink layer that does not achieve optimum hardness and adhesion, resulting in poor smearing and fastness. Incomplete curing means that the surface layer of the printing ink has been dried and cured, but the inside is not completely cured. The ink loss caused by this kind of situation mostly occurs in the printing of large area patterns. This is because large-area patterns use a large amount of ink, and the inside of the ink layer is not so easy to cure completely. To resolve this issue, you can refer to the following solutions:
A. UV Intensity and Dose: Make sure the UV curing system is properly calibrated and delivering adequate UV intensity and dosage. Monitor and adjust UV intensity levels to achieve optimal curing for the specific ink and film material being used. For example, darker patterns absorb more UV light and often require more power to dry completely. Consult ink and equipment manufacturers for recommended UV curing parameters.
B. Curing time and temperature: optimize the curing time and temperature settings to ensure sufficient exposure and ensure that the ink layer is fully cured. Consult the ink manufacturer’s guidelines for recommended curing parameters and adjust accordingly for the printing conditions and equipment used.
C. Service life of UV lamps: At present, the service life of UV lamps on toppan printing equipment is between 800 and 1000 ساعت ها. If the lamps have not been replaced when the rated life is exceeded, it is easy to cause the ink to dry out. Therefore, when replacing the UV lamp tube, it is necessary to make detailed records, and when the UV lamp tube reaches the service life, it must be replaced in time.
3. Excessive ink additives
The presence of excessive ink additives will cause ink drops when printing film-type self-adhesive materials. In the printing process, the printing ink often encounters the problems of thickening, high viscosity and poor inking. Therefore, many operators will choose to add varnish to improve the fluidity of printing ink. با این حال, if the amount of varnish is used improperly, it is very easy to affect the ink viscosity, surface tension and adhesion performance, resulting in ink drop. Please consider the following solutions to resolve this issue:
A. Ink Formulations: Review and optimize ink formulations with the aim of reducing additive overuse. Since not all materials can be perfectly matched with inks, finding the right ink is best achieved by working closely with the ink supplier to develop a custom ink formulation that balances ink properties and minimizes the risk of ink drops.
B. Compatibility testing: Send the material to the ink supplier for testing to ensure that the ink additive used is compatible with the film material and printing process. Compatibility testing is performed between ink and film materials to determine any interactions or incompatibilities that may cause ink drops. Test different ink formulations and adjust additive levels to find the best combination that provides good adhesion while minimizing ink dripping.
Conclusion
Overcoming the challenges of ink droplet printing in film-based self-adhesive materials requires a multifaceted approach. By addressing the causes of low surface tension, insufficient UV curing and excess ink additives, printers can significantly improve ink adhesion and achieve better print quality. Implement surface treatments or primer coats to enhance surface tension, optimize UV curing parameters to achieve full ink cure, and fine-tune ink formulations to minimize the use of excess additives. By adopting these solutions, manufacturers can overcome ink drop challenges and produce high-quality prints on film-based self-adhesive materials.
