1. Poor luster and insufficient brightness
The main reason
The viscosity of the UV varnish is too low and the coating is too thin
2. Excessive dilution with non-reactive solvents such as ethanol
3. Uneven coating
4. The paper has too strong absorbency
5. The anilox pattern on the glue-coated anilox roller is too fine and the oil supply is insufficient
Solution
Increase the viscosity and application amount of UV varnish appropriately according to the different conditions of the paper. For paper with strong absorbency, a primer can be applied first.
Second, poor drying, incomplete curing, and sticky surface
The main reason
1. The ultraviolet light intensity is insufficient
2. The ultraviolet lamp tubes have aged and their light intensity has weakened
3. The UV varnish has been stored for too long
4. Too much diluent that does not participate in the reaction was added
5. The machine is running too fast
Solution
When the curing speed is less than 0.5 seconds, it is generally necessary to ensure that the power of the high-pressure mercury lamp is not less than 120W/cm. The lamp tubes should be replaced in a timely manner. If necessary, add a certain amount of UV varnish curing accelerator to accelerate the drying process.
Three, the UV varnish cannot be applied to the surface of the printed matter, resulting in mottling
The main reason
The viscosity of the UV varnish is too low and the coating is too thin
2. The content of ink thinner or drying oil in the ink is too high
3. The surface of the ink has crystallized
4. Excessive anti-sticking materials (silicone oil, powder coating) on the ink surface
5. The screen lines of the glue-coated anilox roller are too fine
6. Issues with construction techniques (The technical personnel are not very skilled)
Solution
For products that require UV coating, corresponding measures should be taken during printing to create certain conditions. UV varnish can be applied a bit thicker. If necessary, apply a primer or use a special varnish formula.
Four. There are white spots on the UV coating
The main reason
1. The coating is too thin
2. The glue-coated anilox roller is too thin
3. Excessive addition of non-reactive diluents (such as ethanol)
4. There is a lot of dust and other substances on the surface of the printed matter
Solution
Keep the production environment and the surface of printed materials clean; Increase the coating thickness; Add a small amount of smoothing agent; The diluent is preferably an active diluent that participates in the reaction.
Five. Uneven application of UV varnish, with streaks and orange peel phenomena
The main reason
1. The viscosity of the UV varnish is too high
2. The screen lines of the glue-coated anilox roller are too thick (with excessive coating) and the surface is not smooth
3. Uneven coating pressure
4. The leveling property of UV varnish is poor
Solution
Reduce the viscosity of the varnish and decrease the coating amount; Adjust the pressure evenly; The coating roller should be ground finely and polished. Add the bright leveling agent.
Six. Poor adhesion of UV varnish
The main reason
1. Crystallization of the ink surface on printed matter
2. The additives in the printing ink are inappropriate
3. The adhesion of the UV varnish itself is insufficient
4. The conditions for light curing are not appropriate
Solution
The printing process should take into account the varnishing conditions in advance. Apply a primer to enhance adhesion on the already printed products.
Seven. The UV varnish thickens and gels
The main reason
1. The UV varnish has been stored for too long
2. The UV varnish was not stored completely away from light
3. The storage temperature of UV varnish is too high
Solution
Pay attention to the effective usage period of UV varnish and store it strictly away from light. The storage temperature is preferably between 5 and 25 degrees Celsius.
Eight. Strong residual odor
The main reason
1. The UV varnish does not cure completely
2. Insufficient ultraviolet light or aging of UV lamp tubes
3. The UV varnish has poor antioxidant interference resistance
4. Excessive addition of non-reactive diluents in UV varnish.
Solution
The curing of UV varnish must be thorough, and ventilation should be enhanced. If necessary, the type of varnish should be changed.
