The characteristics of each raw material are different, so the probability of showing white spots is also different. There are two kinds of white spots on the aluminum composite film: one is when the machine is off, but it basically disappears after curing. The other is that there is a drop machine, and it does not disappear when it is cooked. The latter is a big problem that affects the appearance, mainly when there is white or light color printing, the poor hiding power of white and light color is easy to see.

White spots caused by insufficient gluing amount The gluing amount is small and white spots occur due to clogging and wear of the gluing network cable, insufficient solid content of the adhesive, etc. Solution: Clean the gluing wire roller frequently to maintain a stable gluing amount. When the machine is stopped, start the mesh roller to make it run idly to avoid blockage. According to the state of the printed matter, adjust the glue concentration and select a suitable mesh roller.

Including two aspects, one is the high solvent residue in the printing process. On the other hand, the solvent residue in the compounding process is high. In these two cases, due to the relatively good barrier properties of polar materials, the residual solvent after compounding is too high. After entering the curing chamber, a large amount of solvent remaining in the compound film is quickly released, which is bound to form bubbles and white spots, and even appear There are no white spots when the machine is off, but white spots appear after curing.

Try to ensure that the solvent residues in the printing process and compounding process are qualified. If necessary, put the unloaded sample into an oven at 80°C for 30 minutes to see if the white spot is eliminated. The oven temperature setting of the compound equipment should have a gradient, so as to avoid excessively high oven temperature in the first section, skinning on the glue coating interface, and incomplete solvent volatilization.

Ink hiding power is poor, especially pale ink. The light passes through the ink layer and is reflected back by the aluminum layer, and the white point generated selects the ink with good hiding power and fine ink particle size. Appropriately increase the amount of ink, improve the concealment rate. This does not mean the adhesive itself, but mainly because the adhesive has high surface tension, poor coating performance, and white spots formed by uneven coating.