Some common faults and solutions of UV varnish

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

main reason:

1. The viscosity of UV varnish is too small, and the coating is too thin.

2. Excessive dilution of non-reactive solvents such as ethanol.

3. Uneven coating of UV oil.

4. The paper is too absorbent.

5. The anilox roller is too thin and the oil supply is insufficient.

Solution: Properly increase the viscosity and coating amount of UV varnish according to different conditions of paper. A layer of primer can be applied to paper with strong penetration and absorption.

Second, poor drying, incomplete light curing, and sticky surface

main reason:

1. The ultraviolet light intensity is not enough.

2. The UV lamp is aging and its intensity is weakening.

3. The UV varnish storage time is too long.

4. Add too much diluent that does not participate in the reaction.

5. The machine speed is too fast.

Solution: In the case of curing speed requirements less than 0.5s, it must be ensured that the power of high-pressure mercury lamps is generally not less than 120w / cm. If necessary, add a certain amount of UV varnish curing accelerator to accelerate drying.

3. The UV varnish on the surface of the printed matter can not be coated or flowered

main reason:

1. The UV varnish has low viscosity and the coating is too thin.

2. The ink contains too much ink or dry oil.

3. The ink surface has crystallized.

4. There are many anti-sticking materials (silicone oil, powder) on the surface of the ink.

5. The glue roller is too thin.

Solution: When printing products that require UV glazing, appropriate measures must be taken to create conditions. When UV varnish is applied, it should be thicker. If necessary, the problem can be solved by applying primer or replacing special varnish.

4. UV coating has white spots and pinholes

main reason:

1. The coating is too thin.

2. The anilox roller is too thin.

3. Too much non-reactive diluent (such as ethanol) is added.

4. There is a lot of dust on the surface of the printed matter.

Solution: The production environment and the surface of the printed matter should be kept clean and the coating thickness should be increased. A small amount of smoothing aid can also be added. For dilution, it is best to use reactive diluents that participate in the reaction.

5. Uneven coating on the surface, streaks and orange peel

main reason:

1. The viscosity of UV varnish is too high.

2. The coating roller is too rough and not smooth.

3. The pressure is uneven.

4. The coating amount is too large.

5. Poor leveling of UV varnish. Solution: reduce the viscosity of UV varnish and reduce the amount of coating. The pressure is adjusted evenly. The coating roller should be ground and polished. Light leveling agent can be added.

Six, UN varnish adhesion is not good

main reason:

1. Crystallization of printed ink surface.

2. The auxiliary materials in the printing ink are not suitable.

3. The UV varnish itself has insufficient adhesion.

4. Light curing conditions are not suitable.

Solution: The printing process should consider the glazing conditions in advance. The printed product needs to be coated with primer to enhance adhesion.

7. UV varnish thickens and gels

main reason:

1. The UV varnish storage time is too long.

2. Varnish is not stored completely in the dark.

3. The storage temperature is too high.

Solution: Pay attention to the effective use period of UV varnish and store it strictly in the dark. The storage temperature is preferably 5 ℃ ～ 25 ℃.

8. Large residual odor

main reason:

1. Dry curing is not complete.

2. Insufficient UV light source or lamp aging.

3. The UV varnish has poor anti-oxygen interference ability.

4. Excessive addition of non-reactive diluent in UV varnish.

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

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