Five Common Problems in UV Polishing Process and Solutions

UV glazing, also known as UV glazing or curing glazing, UV glazing oil consists of photosensitive resin, reactive diluents, photoinitiators and additives. The principle is that in a certain wavelength of ultraviolet ray irradiation, the system of light induced The free radical of the reagent initiates the unsaturated double bond in the resin, and the key-locking polymerization reaction occurs rapidly, so that the crosslinked conjunctiva cures.

Its advantages are: high speed of coating, high film brightness, firm film surface after drying, high production efficiency, small occupied space, good mechanical and heat resistance, cold resistance, water resistance, abrasion resistance, etc. After the application of the coating, the surface of the printed product can be very bright and smooth, and the refraction effect produces a strong three-dimensional effect on the graphic text. The color is more vivid, and the printed product has a high-grade sense.

The disadvantages are: the UV oil itself has a high degree of polymerization, the polarity of the surface molecules is poor, and there is no hair pores, so the affinity of the UV film layer is poor.

Common problems include the following:

1. "Pin point"

the reason:

a. The ink has crystallized.

b. The surface tension is large and the ink layer does not wet well.

solve:

a. Add 5% lactic acid to UV oil to destroy the film, remove oil or roughen it.

b. Decrease the surface tension value and add surfactants or solvents with lower surface tension values.

2. Streaks and wrinkles

Reason: UV oil is too thick, coating amount is too large, mainly in the roller coating.

Solution: Reduce the viscosity of UV oil and add appropriate amount of alcohol solvent to dilute.

3. Orange peel

the reason:

a, UV oil viscosity, poor leveling.

b. The coating roller is too rough and the amount of coating is too large.

c. The pressure is not uniform.

solve:

a, reduce the viscosity, the national leveling agent and the appropriate solvent.

b, choose a fine coating roller and reduce the coating amount.

c. Adjust pressure.

4. Sticky

the reason:

a. Insufficient UV light intensity or excessive speed.

b, UV light oil storage time is too long.

c. Excessive diluent added to the reaction.

solve:

a, when the curing speed is less than 0.5 seconds, the UV power should not be less than 120w/cm.

b. Add a certain amount of UV varnish curing accelerator or change the varnish.

c, pay attention to the rational use of thinner.

5. Can't paint or flower

the reason:

a、Printing ink surface produces crystal oil, dusting and so on.

b. Too many ink and dry oils are blended in ink.

c. The viscosity of the UV varnish is too low or the coating is too thin.

d, rubberized anilox roller is too thin.

e, light curing conditions are not suitable.

f. The poor adhesion of the UV varnish itself and the poor adhesion of the printed material.

solve:

a. Eliminate the crystallized layer, roughen it, remove grease or add 5% lactic acid.

b. Select the ink auxiliary material that matches the UV oil process parameters, or wipe with a cloth.

c. Use high-viscosity UV Varnish to increase the amount of coating.

d. Use an anilox roller that matches the UV varnish.

e. Check whether the UV lamp is aging, or the speed is inconsistent. Select the appropriate drying conditions.

f. Apply primer or replace special UV Varnish or choose a good surface finish.