HENGHAO Machinery
Mickey
2025-03-29

The Importance of Corona Treatment in Flexo Printing: How It Enhances Print Quality

Introduction

In flexographic printing, achieving high-quality prints on various substrates can be challenging. One critical factor that directly impacts ink adhesion and print clarity is surface treatment, specifically corona treatment. Without proper surface preparation, ink may not bond well, leading to smudging, fading, or poor durability.

This article explores the importance of corona treatment in flexo printing, how it works, and why it is essential for improving print quality and production efficiency.

What Is Corona Treatment?

Corona treatment is a high-frequency electrical discharge process used to increase the surface energy of non-porous substrates like polyethylene (PE), polypropylene (PP), BOPP, PET, and other plastic films. These materials have low surface tension, which makes it difficult for inks, coatings, or adhesives to adhere properly.

By applying a corona discharge, the material's surface energy is increased, making it more receptive to ink absorption and bonding.

Why Is Corona Treatment Essential for Flexo Printing?

1. Improves Ink Adhesion

Without corona treatment, ink can bead up or smear on low-energy surfaces.
Enhancing surface tension ensures better ink anchoring, preventing fading or peeling.

2. Enhances Print Sharpness and Consistency

Treated surfaces allow uniform ink distribution, reducing uneven prints or blotches.
Ideal for high-resolution printing, where detail and color accuracy matter.

3. Reduces Ink Consumption and Waste

Since treated surfaces absorb ink more effectively, less ink is required.
Reduces ink wastage, lowering overall printing costs.

4. Increases Durability and Resistance

Prints last longer without chipping or fading.
Ideal for packaging, labels, and flexible films exposed to moisture or friction.

5. Improves Lamination and Adhesive Bonding

Essential for multi-layer packaging, where adhesives need a strong bond.
Prevents delamination and peeling over time.

How Corona Treatment Works in a flexo printing machine

Step 1: Substrate Preparation

The plastic film, paper, or laminated material enters the printing line.

Step 2: Passing Through the Corona Treater

The substrate moves under high-voltage electrodes, creating a plasma discharge.
This alters the surface at a molecular level, increasing surface tension.

Step 3: Printing & Coating

The now-treated surface grips ink firmly, resulting in high-quality prints.
Ensures fast drying and strong adhesion.

How to Measure Surface Energy After Corona Treatment

Dyne Testing:

Dyne pens or solutions determine whether the treatment was effective.
A surface energy of 38-42 dyne/cm is typically required for flexographic printing.

Which Flexo Printing Applications Benefit from Corona Treatment?

Flexible packaging (food pouches, snack bags, bottle labels)
BOPP labels & films (transparent labels, shrink sleeves)
PE & PP containers (cosmetic tubes, pharmaceutical labels)
Thermal paper & coated paper applications

Conclusion

Corona treatment is a game-changer in flexographic printing, ensuring better ink adhesion, superior print quality, and increased durability. By integrating a high-quality corona treatment system into a flexo printing machine, manufacturers can reduce costs, improve efficiency, and achieve long-lasting prints on various substrates.