How to Print Codes on Flexible Packaging Films

Flexible packaging films—like BOPP, PET, PE, and multi-layer laminates—are widely used in food, snacks, pharmaceuticals, and frozen goods. However, their low surface energy, smooth texture, and fast-moving packaging processes create challenges for ink adhesion, drying, and clarity. This guide explains how to print variable data like expiry dates, batch codes, and barcodes on flexible films using the right inkjet technology and ink.

Key Challenges in Film Coding

• Low surface energy: Plastic films resist ink bonding unless treated or matched with the right ink
• Fast conveyor speeds: Requires instant drying to prevent smudging
• Flexible/curved shape: May wrinkle or move during printing, causing misalignment
• Thermal sensitivity: Some films deform under high heat—affecting drying method choices

Best Inkjet Technologies for Film Coding

1. CIJ (Continuous Inkjet)

• Most common for high-speed snack or flow pack lines
• Uses fast-drying solvent-based ink (e.g. MEK) for instant adhesion
• Ideal for inline date and batch code on BOPP, PET, LDPE

2. TIJ (Thermal Inkjet)

• Recommended for medium-speed or intermittent lines
• Water-based ink may require coated films or specially formulated fast-dry solvent ink
• High DPI—great for barcodes on pouches or labels

3. TTO (Thermal Transfer Overprinting)

• Excellent for flexible film printers with form-fill-seal (FFS) or pouching lines
• Uses thermal ribbon—no ink drying time needed
• Sharp resolution; perfect for nutrition labels, logos, variable info

4. UV Inkjet (DOD)

• Best for glossy, laminated, or multi-layer films
• Instant UV curing prevents smearing and increases chemical resistance
• Low-migration inks available for food contact zones

Ink Considerations

• Use inks tested and certified for adhesion to film type (e.g., MEK for BOPP, UV for PE/PET)
• Pigmented inks improve contrast on dark or reflective films
• Low-migration ink is critical for primary packaging in food or pharma

Surface Preparation Tips

• Corona/plasma treatment: Increases surface energy for better ink adhesion
• Clean surface: Remove oil, dust, or anti-static residues from film rolls
• Consistent tension: Prevent wrinkling that may affect print alignment

Drying & Curing Techniques

• Use IR blowers or fans for CIJ/TIJ if drying is slow
• Install UV lamp for UV-curable inkjet printers
• Use TTO where heat sensitivity prohibits solvent or UV drying

Real-World Applications

• Snack packaging (printed with CIJ during form-fill-seal)
• Sachets and pouches (coded with TTO or TIJ pre-sealing)
• Frozen food bags (MEK ink with cold-resistance in CIJ system)
• Medical sample bags (UV inkjet for low migration and smudge-proof finish)

FAQs

• What if the ink wipes off after printing? The ink may not be compatible with the film. Try surface treatment or switch to a more adhesive formulation.
• Can I print on both matte and glossy film? Yes—but glossy films require faster drying inks (MEK or UV) and often corona treatment.

Conclusion

Coding on flexible films requires matching the right printer, ink, and process conditions to your packaging material. With proper selection and testing, inkjet systems can achieve high-speed, high-contrast printing even on difficult surfaces. For tailored recommendations and ink testing on your film type, contact Cheef Inkjet at sales@cheef.cn.