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In the field of flexographic printing, the occasional ink adhesion failure of film label printing has been a problem for printing enterprises. Flexo printing has the advantages of low cost, high efficiency and adaptability. However, in the printing of film labels such as ice-cream container labels, water bottle labels, yogurt labels, shower gel bottle labels, perfume bottle labels, medicine bottle labels and other film labels, due to a combination of factors such as substrate properties, ink compatibility and printing process, unsatisfactory printing effects and ink adhesion failure will occasionally occur. This article will deeply analyze the reasons of these problems from the characteristics of flexography printing and put forward targeted solutions.

MJRY Series Stack Type Flexo Label Printing Machine for Beer Labels

Why Choose Flexographic Printing

Flexographic printing is a type of printing method that uses flexible printing plates, which are usually made of materials such as rubber or photopolymer. This printing method has its own unique advantages.

Low Cost 

The production cost of flexographic printing plates is relatively low, which is suitable for mass production and can effectively reduce unit costs.

Strong Adaptability

Flexographic printing can adapt to a variety of different substrates, such as paper and paper containers (hamburger wrapper, paper placemat, paper tray liner, baking paper, paper coffee cups, paper ice cream bowls, medical sterilization pouches, fast food paper bags, etc.), film (diaper packaging, sanitary napkin packaging, juice bottle labels, etc.), aluminum foil (chocolate wrapper, candy wrapper, pill blister pack, facial mask pouch, cigarette inner liner, etc.), non-woven fabrics (bed sheet, lazy rags, disposable surgical gowns, shopping bags, etc.) and so on.

MJCI Series CI Type Flexo Printing Machine for Cupcake Liner

High Printing Quality

Flexography printing can achieve high quality printing effect with bright colors and rich layers, and is suitable for fine printing.

Environmentally Friendly

The ink used in flexo printing is mostly water-based or solvent-based ink, which is friendly to the environment and meets the requirements of modern environmental protection.

Solvent-Based Ink for Flexo Printing Machinery for Luxury Paper Bags

What Issues in Flexo Printing of Film Labels

The main problems in flexographic printing of film labels are poor printing effect and ink adhesion failure.

Poor Printing Effect

Streaking: During flexo printing, film labels such as body wash labels, beverage labels, hand soap wash label, toothpaste tube labels and other film labels may show vertical, horizontal or irregular streaks. This is usually due to anilox roll scoring or uneven ink distribution. Anilox roller scoring affect the uniformity of ink transfer, while ink clogging cause uneven ink distribution during the printing process, resulting in streaks.

Color Deviation: The surface characteristics of film materials are different from those of paper, which may result in insufficient ink adhesion on the surface of the substrates, thus affecting color reproduction. In addition, factors such as the drying speed of the ink and the humidity of the printing environment can also affect the printing color.

MJUT Series Inline Type Flexographic Press for Laundry Detergent Label

Ink Adhesion Failure

Poor Match Between Ink and Substrates: The ink used in flexo printing needs to match the surface properties of the film substrates. If the ink surface tension is excessive or does not match the surface properties of the film substrates, the ink will not be able to firmly adhere to the surface of the substrates, resulting in poor printing results and ink adhesion failure.

Insufficient Ink Drying: In the process of multi-color printing, if the ink of the previous color is not completely dry, the printing of the subsequent colors may cause the ink layers to interfere with each other, resulting in ink adhesion failure. In addition, insufficient power of UV curing lamps or too fast printing speed can also lead to incomplete curing of UV ink, which in turn triggers ink adhesion failure.

How to Prevent Ink Adhesion Failure

Ink adhesion failure during flexographic printing can be resolved by using specially formulated inks and compatible auxiliary materials, ensuring ink compatibility with film coatings, adjusting ink drying speed, ensuring complete ink drying or curing, and managing press speed during multi-color printing.

Use Specially Formulated Inks & Compatible Auxiliary Materials

There are many inks on the market that are specially designed for skin care labels, medical device labels, vitamin bottle labels, cell phone battery labels, note book labels, and other film self-adhesive printing products, even for specific types of film substrates. Film label printing should use special ink, varnish oil and matching additives, otherwise there may be a mismatch between the ink and the printing substrates, resulting in the ink adhesion failure.

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Ensure Ink Compatibility With Film Coatings

For film substrates with coated surfaces, it is necessary to use inks that match the coating. If the ink is not selected properly, ink adhesion failure may occur. Suitable ink enables the resin in it firmly bond with the resin in the coating, so that the ink layer will not come off even if the ink is not completely dry.

Adjust Ink Drying Speed

Pay attention to the expiration date of the ink, if the ink dries slowly, you can add the appropriate amount of drying agent to speed up the drying speed.

Ensure Complete Ink Drying or Curing

Regularly cleaning the ink curing system and replacing the UV lamps on time is essential to ensure that the UV ink is fully cured. Regularly check the performance and condition of the UV curing system by equipment or UV test strip and adjust the ink film thickness and printing speed according to this data to achieve optimal printing results.

UV Curing System of Horizontal In-Line Flexo Printer for Wrap Labels

Managing Press Speed During Multi-Color Printing

For labels with multi-color printing such as condiment labels, ham sausage labels, cookies labels, instant noodles labels, etc., it is not recommended to use too fast printing speed. It is recommended to adjusted the printing speed to 30-50 m/min to ensure that each layer of ink dries sufficiently, reducing waste and improving print quality.

Although the problems of poor printing effect and ink adhesive failure in flexographic printing of film labels such as chocolate labels, nuts labels, bakery labels, jam jar labels are complex and diverse, these problems can be effectively solved by optimizing the selection and use of inks and optimizing the printing process. In actual production, printing companies should flexibly adjust and optimize the printing process according to specific substrates and process conditions to improve printing quality and production efficiency. At the same time, regular maintenance of equipment and testing of key parameters in the printing process are also important guarantees for ensuring printing quality.