1. The surface tension of the ink is low, resulting in poor coating effect of the adhesive and uneven coating. Therefore, the adhesion between the ink layer and the aluminized layer and the tightness of the layer will be inconsistent, thereby plating. The reflective effect of the surface of the aluminum layer is also strong and strong, forming white or gray spots visually.
2, the ink's hiding power is not strong or the leveling is poor, resulting in uneven coverage (especially white ink and light yellow ink) where the hiding effect is not good, the color of the aluminized layer will penetrate through the ink.
3, the adhesive concentration is too high, the viscosity is too large, it is easy to reverse the adhesion of the ink into the glue, so that the color of the printed layer changes. At the same time, if the viscosity of the adhesive is too large, the fluidity is not good, and the uneven amount of the glue is easily caused, which affects the reflective performance of the surface of the aluminized layer and causes spots.
4. The ink and the adhesive do not match, so that the adhesive has poor penetrability to the ink, and there is a phenomenon of repulsion and speckle.
5. The composite film is not completely dried, and the solvent volatilization is insufficient, causing excessive solvent residue in the adhesive, and some of the ink is dissolved, thereby forming spots, and many microbubbles are formed after the ripening.
6. The quality of the aluminized film itself is relatively poor, and there are many light-transmitting points. After the compounding, the rate of repair of the aluminized layer is different, forming spots.
7. The temperature of the drying tunnel (especially the first drying tunnel) is too high, causing the surface glue to dry too fast and the surface conjunctiva; when the internal solvent is vaporized in the second and third drying tunnels, it will break through the surface film. The adhesive is squeezed to expose the ink, causing uneven thickness of the adhesive layer to cause spots.
