Pearlescent ink in plastic gravure printing common problems and solutions

Pearlescent ink is used by more and more manufacturers because of its strong decorative effect and noble and elegant qualities. However, many manufacturers have not mastered the use of pearlescent ink, cannot achieve the desired results, and even experienced many failures, resulting in great waste. Here, I made some analysis of the common problems of pearlescent ink in plastic gravure printing and proposed corresponding solutions for reference by peers.

One, pearl effect is poor or no pearl effect

the reason:
1. The printing plate is too shallow or the cell site is blocked, and the dry plate phenomenon occurs.
2. The viscosity of the ink is too high or too low and does not match the printing speed.
3. The squeegee angle is too large or the impression cylinder pressure is too high.

Approach:
1. Plates are usually in the range of 25～45μm; use thinner to clean the plates.
2. Adjust the viscosity of the ink to match the speed of the press.
3. Adjust the angle of the squeegee, generally 45 ° is appropriate; reduce the imprinting force.

Second, stick back, adhesion

the reason:
1. The pearlescent ink on the print is not completely dry.
2. The winding tension is too large or the curl length is too long.
3. Film corona treatment is improper or damp.

Approach:
1. Add fast-drying thinner to the ink, or increase the power of the drying device to make the ink dry thoroughly.
2. Reduce winding tension and shorten curl length.
3. Reprocess the film and prevent it from getting wet.

Third, pearl ink printing uneven

the reason:
1. Pearlescent ink viscosity is too high, it is not easy to evenly apply, resulting in ink layer uneven phenomenon after imprinting.
2. Pearl powder is easy to precipitate.
3. Bad contact between impression cylinder and plate cylinder.
4. The proportion of pearl powder in pearlescent ink is insufficient.

Approach:
1. Reduce the viscosity of the ink and select the appropriate diluent.
2. Thoroughly stir the pearlescent ink.
3. Increase the pressure on the impression cylinder or replace it with a new one.
4. Select high-quality pearl powder and diluting agent, so that the pearl powder accounted for 30% to 35%.

Fourth, there is pearl effect but no luster

the reason:
1. The diluent volatilizes too fast.
2. The oven temperature is too high or the cold air is too large.
3. Pearlescent ink viscosity is too low.

Approach:
1. Slow-drying thinner should be added to suit the machine speed.
2. Reduce the oven temperature or reduce the amount of cold air.
3. Increase the viscosity of pearlescent ink and adjust it with the same gold adjustment oil.

Fifth, often appear knife line

the reason:
1. The squeegee has a gap or angle.
2. Insufficient fineness or viscosity of pearlescent ink.
3. The plate hole is too deep.

Approach:
1. Replace the squeegee or adjust the angle of the squeegee to scrape the excess ink on the plate.
2. Adjust the viscosity of the ink to match the machine speed.
3. After the plate, add two cold air ducts to send the hair to the layout.

VI, paste version, blocking version

the reason:
1. The ink dries too quickly.
2. There are impurities mixed in.
3. The squeegee angle is not accurate or the distance from the impression cylinder is too large.

Approach:
1. Add the appropriate diluent to the ink.
2. Pay attention to the surrounding environment and control the humidity in the workshop.
3. Adjust the angle of the squeegee and the distance from the impression cylinder to reduce the dry time.

VII. Inconsistent prints after pearlescent printing

the reason:
1. Pearlescent ink appears discoloration.
2. Inconsistent pearlescent effect.
3. Stirring is uneven and pearlescent powder accumulates.

Approach:
1. Control the drying of the ink of the previous color, prevent the ink of the first few colors from mixing into the pearl ink and cause the color change.
2. Diluent should not be added to the ink pump alone, it should be added together with pearl ink.
3. When stirring with the ink pump, it is necessary to clean the pearl powder accumulation phenomenon in time to prevent uneven coating.

Eight, the peel strength after printing compound is poor

the reason:
1. The film corona treatment did not meet the requirements.
2. Adhesives and thinners are not compatible with pearlescent inks.
3. The amount of glue on the compound is uneven.

Approach:
1. Grasp the type of film and corona treatment standards.
2. Choose a pearlescent ink to make it compatible with the adhesive.
3. Control the gluing amount, temperature, tension and so on when compounding.

Source: "Printing Technology"