How to solve the problem of ink dropping on packaging bag labels affecting product quality?

In the process of printing labels on packaging bags, the problem of ink dropping from the surface layer is easy to occur, which greatly affects the quality of printed matter and even delays the delivery date. Below, Shunxingyuan Packaging, a professional flexible packaging manufacturer, summarizes and lists the common causes and improvement methods of ink dropping from three aspects: tension, ink drying, and matching of ink and materials.

I. Influence of Tension on Ink Dropping and Solutions

For film materials with corona-treated printing surfaces, to achieve good ink wetting, the dyne value usually needs to be above 38 mm/m. Below 36mm/m it is easy to have ink dropping problems; at the same time, the dyne value of this material will gradually decrease over time, resulting in ink dropping problems during printing. The essence of this problem is the tension problem.

Solutions:

1. Use a satellite rotary press with an online corona function to perform online corona treatment to improve the surface energy of film materials;

2. Intermittent printing machines can be used for surface priming treatment to improve the adhesion of surface printing;

3. When the dyne value decreases, corona treatment is needed during printing, but the size of the dyne value cannot fully represent the oil 4 、the adhesion between the surface material and the general dyne value attenuation cycle is 3 months -6 months, so it is recommended to minimize the long-term storage of raw materials in stock.

5. It is recommended to use inks with higher adhesion, and it is recommended to consult ink suppliers.

II. Influence of Ink Drying and Tension on Ink Dropping and Solutions

During the printing process, ink drying and tension may also cause ink dropping. Specifically, the ink layer is too thick, resulting in incomplete drying; insufficient UV lamp energy, aging of the lamp tube, aging of the lamp tube reflector, resulting in UV The lamp drying and curing is insufficient, and the ink layer is not dry; the ink is over-dried, causing the material to deform and the ink layer to peel off.

Solutions:

1. Use deep ink and thin printing, which is commonly known as reducing the amount of ink. For example, the spot color base ink can be mixed a little deeper, and the ink amount can be reduced during formal printing to achieve the effect of the sample, while increasing UV lamp output power, reduce printing speed, increase UV lamp irradiation time to achieve drying effect. This scheme is suitable for old intermittent or satellite rotary machines and old UV lamp tube solutions.

2. Check UV whether the lamp tube is aging, and clean the reflector. Usually domestic UV lamp tube service life 500-1000 hours, imported lamp tube life 1000-2500 hours, the specific can refer to the actual use situation. It is recommended that printing plants clean the UV lamp tubes every six months to ensure normal use.

3. Reduce UV lamp output power. The specific operation is that for general printing plant printing jobs, the first few colors in the color sequence are mostly logos or small characters, and the required light is limited. The resistance can be opened UV lamp irradiation, and it can be dried. Do not over-irradiate with high gear, because the film material has limited heat absorption, excessive irradiation will cause the film material to curl, deform, become brittle, and reduce ink adhesion, etc. The principle of using the lamp should be followed first low gear and then high gear. UV Lamp usage principle.

III. Influence of Ink and Material Matching on Ink Dropping and Solutions

Finally, the degree of matching between ink and materials will also cause ink dropping to a certain extent. For example, if the molecular tension of the ink is too large, a uniform ink layer cannot be formed on the surface of the printing material; or if an expired ink model or inferior domestic ink is used, it will cause ink dropping during printing.

Solutions:

1. Switch to inks that match the printing material, such as film-specific inks and inks with sun and light resistance;

2. For expired inks, printing tests should be carried out before printing, or some simple text or small logo patterns, and some low-grade products should be printed;

3. For printing large-area solid colors and full-page halftone dot line patterns, it is recommended to use inks with good brands and high adhesion.