Printability of BOPP Glossy Films: Exploring Offset Flexography and Gravure Print Methods
Printability of BOPP Glossy Films: Exploring Offset Flexography and Gravure Print Methods
Have you ever wondered how the shiny, glossy wraps on vegetables like cauliflower are printed? This fascinating process involves a combination of specialized film materials and meticulous printing techniques. In this article, we delve into the printability of BOPP (Biaxially Oriented Polypropylene) glossy films, with a focus on the suitability of common printing methods such as offset flexography and gravure printing. We also examine the crucial step of corona treatment in preparing these films for high-quality print jobs.
Understanding BOPP Films
Biaxially Oriented Polypropylene (BOPP) films are widely used in packaging applications due to their excellent clarity, stiffness, and chemical resistance. BOPP films are made by extruding polypropylene resin, orienting it in both directions, and then cooling it rapidly. This process renders the film clear, transparent, and resistant to deformation. The glossy finish of BOPP films makes them particularly attractive for packaging high-end products, where visual appeal is crucial.
The Role of Corona Treatment in Printability
Despite their numerous advantages, BOPP films present a challenge when it comes to printing. Their smooth, non-porous surface makes it difficult for ink to adhere properly. To address this issue, manufacturers often employ a process called corona treatment. During corona treatment, the surfaces of BOPP films are exposed to high-frequency alternating current electromagnetic fields. This treatment slightly alters the surface chemistry of the film, creating microscopic irregularities that improve its ability to accept and retain ink.
Offset Flexography Printing
Offset flexography is a common printing technique used in the packaging industry. It is known for its ability to print on a wide variety of surfaces, including plastics and films. During offset flexography, an ink-covered rubber roller transfers the ink to a blanket cylinder, which then transfers the ink onto the BOPP film. This method is particularly effective when combined with corona treatment, as the pre-treated surface ensures better ink adhesion.
For a successful offset flexography print job, it is essential to choose the right ink. Water-based inks are often preferred for BOPP films because they are more environmentally friendly and have a lower melting point, allowing them to bond better to the film surface without damaging the material. Additionally, the printing speed and quality depend on the equipment's setup and the skill of the operator.
Gravure Printing Explained
Gravure printing, another popular method for packaging applications, involves using a steel roller etched with raised cell patterns that hold the ink. The ink roller transfers the ink to the pre-etched roller, which then transfers the ink to the substrate, in this case, BOPP film. Gravure printing offers high-quality results and the ability to produce intricate designs, making it suitable for applications requiring sharp details and fine text.
Gravure printing on BOPP films is more challenging than offset flexography due to the inherent smoothness of the film. However, with proper corona treatment, the printed surface can achieve a consistent and high-quality finish. The key factors in achieving success with gravure printing on BOPP films include the viscosity and tack of the ink, the speed at which the film passes through the machine, and the precision of the etching on the gravure cylinder.
Conclusion
The printability of BOPP glossy films is a testament to the advancements in packaging technology and printing methods. While traditional printing techniques face challenges when working with these smooth films, corona treatment and meticulous process control can overcome these hurdles. Understanding the nuances of BOPP films and the role of specialized treatments like corona treatment is crucial for achieving optimal print results using common printing methods such as offset flexography and gravure printing.