Half the quality of film printing is decided before printing — in surface treatment. Here are best practices for corona treatment in film-printing applications.
1. Setting the Key Parameters
1. Power
Power determines discharge intensity. As a rule of thumb, use a power density of 10–20 W/m²/min for print-grade treatment. Too low, and dyne level falls short; too high, and the film surface may be damaged.
2. Line Speed
The faster the web passes the electrode, the shorter the treatment time. Power must track line speed — double the speed, roughly double the power — to keep treatment intensity consistent.
3. Electrode Gap
The gap between electrode and roll is normally 1.5–3 mm. Too large causes unstable discharge; too small risks arcing and substrate damage. Check regularly with a feeler gauge.
2. Verifying Treatment
- Test with a dyne pen: target 38–40 mN/m
- Sample evenly across the web width
- Keep samples and track dyne decay over time
3. Common Defects & Troubleshooting
| Defect | Possible Cause | Solution |
|---|---|---|
| Low dyne level | Low power, large gap, dirty roll | Raise power, adjust gap, clean roll |
| Uneven treatment | Worn electrode, unstable tension | Replace electrode, stabilize tension |
| Pinholes | Over-treatment, contaminant discharge | Reduce power, remove contaminants |
4. Time Management
PE film decays quickly after treatment; print as soon as possible. With an in-line system, you get “treat-and-print” in one pass, eliminating the time-lag issue.
Need an assessment for your printing line? See our in-line corona systems or contact us.