In recent years, the soft packaging, labeling, and decorative film markets have seen rising demands for print quality. Beyond color, clarity, and appearance, factors such as scratch resistance, rub resistance, and post-processing stability have become key concerns for manufacturers.

In practice, printing quality is not determined solely by inks and equipment. For polyolefin films like BOPP, PP, OPP, and PE, the condition of the substrate surface can significantly affect ink adhesion and overall print performance.

These films are widely used in food packaging, personal care packaging, labels, and decorative films due to their transparency, chemical resistance, and ease of processing. However, their inherently low surface energy and low polarity make it difficult for inks to wet and adhere reliably.

As a result, printers may encounter issues such as:

• Ink peeling during tape testing
• Poor resistance to rubbing or scratching
• Ink detachment during rewinding or die-cutting
• Variability in print quality across different film batches
• Surface tension degradation during storage
• Reduced layer stability in subsequent processing

These issues not only affect the final product appearance but can also lead to increased rework, material waste, and production adjustments.

Corona Treatment Remains Fundamental, but Not Sufficient

Corona treatment has long been a standard method to improve polyolefin film printability. By increasing surface energy, it allows inks to spread and adhere more effectively.

However, the effectiveness of corona treatment depends on factors such as film formulation, treatment intensity, storage time, and environmental conditions. Its effect may diminish over time, and additives migrating to the surface can further impact ink wetting and adhesion.

Consequently, even when using the same ink and process, different film batches may exhibit variable adhesion performance. While adequate for standard printing applications, higher-end projects often require additional surface solutions.

Water-Based Print-Receiving Coatings as a Complementary Solution

To further improve printability on low-surface-energy films, more manufacturers and printers are turning to print-receptive top coatings.

Applied before printing, these coatings form a thin interface layer between the film and the ink after drying, improving ink wetting, spreading, and adhesion.

Unlike modifying the ink formulation, top coatings enhance the film surface itself, providing a more stable foundation for printing. This can help minimize performance differences across batches and production setups.

Well-chosen top coatings can also enhance the stability of printed layers during rewinding, die-cutting, and transport.

Gloss and Matte Requirements Differ

As packaging designs become more diverse, different surface aesthetics are needed.

Some applications require high transparency and gloss for a vivid printed effect, while others prioritize a matte finish and soft tactile feel. These requirements influence the choice of top coating and its compatibility with inks.

For instance, SA-248G water-based gloss top coating is suitable for corona-treated PE, PP, OPP, and BOPP films, improving UV ink adhesion while maintaining a glossy finish. For applications requiring a matte look, SA-248M provides a suitable alternative.

Top Coating vs. Bottom Primer

In film coating and label manufacturing, both top coatings and bottom primers improve adhesion, but they address different surfaces.

Top coatings are applied to the printing face to enhance ink adhesion. Bottom primers are applied to the adhesive face to improve bonding with adhesives, such as pressure-sensitive or other coating layers.

Identifying whether the adhesion problem occurs on the printing side or adhesive side is essential to selecting the right surface treatment.

Surface Treatment Becomes Part of Print Quality Control

Manufacturers increasingly value consistency and reliability in soft packaging and label production. Issues like ink peeling or insufficient rub resistance are not always due to ink alone—film surface conditions often play a critical role.

From corona treatment and surface cleaning to print-receptive coatings, film surface treatment is becoming a central part of print quality control.

Sinograce Chemical is committed to providing reliable, easy-to-apply surface treatment solutions for film printing. Its SA-248G gloss top coating and SA-248M matte top coating help improve UV ink adhesion on BOPP, PP, and OPP films while supporting consistent production and print quality. These solutions offer practical technical support for the evolving demands of the soft packaging and label industry.