UV Varnish Common Problems and Solutions

First, the gloss is not good, the brightness is not enough

main reason:

1. UV Varnish viscosity is too low and the coating is too thin.
2. Ethanol and other non-reactive solvents are diluted in excess.
3. UV oil coating is not uniform.
4. The paper is too absorbent.
5. The anilox roller is too thin and the fuel supply is insufficient.

Solution: Appropriately increase the viscosity and coating amount of UV varnish according to different conditions of the paper. For osmotic and absorbent paper, a primer layer can be applied first.

Second, poor drying, light curing is not complete, the surface is sticky

main reason:

1. UV light intensity is not enough.
2. UV lamp aging, strength weakened.
3. UV light oil storage time is too long.
4. Do not add too much diluent to the reaction.
5. The machine speed is too fast.

Solution: In the case of a curing speed requirement of less than 0.5s, it must be ensured that the power of the high-pressure mercury lamp is generally not less than 120W/cm, the lamp should be updated in time, and do not wait for the bad to change. If necessary, add a certain amount of UV varnish curing accelerator to accelerate drying.

Third, the printed surface of the UV light oil can not paint, hair

main reason:

1. UV Varnish has a low viscosity and the coating is too thin.
2. Ink contains excessive varnish or dry oil.
3. The ink surface has crystallized.
4 ink surface anti-stick material (silicone oil, dusting) and more.
5. The rubberizing roller is too thin.

Solution: When printing products that require UV coating, appropriate measures must be taken to create the conditions. When applying UV varnish, apply thicker coatings. If necessary, use oil on the base or replace special varnish to solve the problem.

Fourth, UV coating with white spots and pinholes

main reason:

1. The coating is too thin.
2. The anilox roller is too thin.
3. Excessive addition of non-reactive diluents such as ethanol.
4. Printed surface dust and more.

Solution: The production environment and printed surface should be kept clean and the thickness of the coating should be increased. A small amount of smoothing aid can also be added. The dilution is preferably a reactive diluent that participates in the reaction.

Fifth, uneven surface coating, striped and orange peel phenomenon

main reason:

1.UV varnish viscosity is too high.
2. The coating roller is too rough to be smooth.
3. The pressure is not uniform.
4. The coating amount is too large.
5. UV light oil leveling poor. Solution: Reduce the viscosity of UV varnish and reduce the amount of coating. Even pressure adjustment. The coating roller should be ground and polished. Light leveling agents can be added.

6, UN light oil adhesion is not good

main reason:

1. The surface of the printed ink is crystallized.
2. The auxiliary material in the printing ink is not suitable.
3. UV varnish itself has insufficient adhesion.
4. The light curing conditions are not suitable.

Solution: The printing process must be considered in advance glazing conditions. The printed product needs to be coated with an adhesion-enhancing primer.

Seven, UV Varnish thickens, there is a gel phenomenon

main reason:

1.UV light oil storage time is too long.
2. Varnish is not completely protected from light.
3. The storage temperature is high.

Solution: Pay attention to the effective period of use of UV Varnish and strictly avoid light storage. The storage temperature is preferably 5 °C ~ 25 °C.

Eight, residual odor

main reason:

1. Dry curing is not complete.
2. Insufficient UV light source or lamp aging.
3.UV varnish has poor anti-oxidation capability.
4. UV light oil in non-reactive diluent added too much.

Solution: UV varnish must be thoroughly dried and cured. And to strengthen ventilation, if necessary, change the UV Varnish varieties.