Common problems and countermeasures in UV varnish printing process
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1, the gloss is not good, the brightness is not enough, in addition to the specific matte, flat light and other effects of UV varnish, it is generally required that the higher the gloss of UV varnish is, the better:
main reason
A, UV varnish itself is too small, so the printed coating is too thin
B, ethanol, toluene and other non-reactive solvents are over-diluted
C, the gloss of the photo-solid resin itself is not enough
D, paper absorption is too strong
E, the texture is too fine, resulting in too little transfer of varnish. F scraper and mesh version are not properly selected.
Solution:
A. Use high gloss acrylic photocuring resin
B, appropriate increase of varnish viscosity
C. Strictly control the amount of ethanol and toluene added
D. For paper with strong permeability, you can apply a primer or choose a paper with good density.
E. Appropriately increase the diameter F of the anilox roller to reduce the hardness of the blade
G. When printing, you can also choose a lower mesh screen to increase the thickness of the coating.
2. Printing of UV varnish cannot be performed on the surface of the printed matter:
main reason:
A, UV varnish viscosity is small, the coating is too thin
B, the surface of the printed matter is oily
C, the surface of the ink is "vitrified", improper affinity with varnish
D, the surface of the ink contains too much anti-adhesive material (such as silicone oil, dusting)
E, coated anilox roller is too thin
Solution:
A. Take necessary cleaning measures for the printed matter to be glazed
B, properly adjust the viscosity of the varnish
C. The type and amount of additives in varnish can be added, and a small amount of wetting agent can be added.
D. Wipe the surface of the print with a 2% alkaline solution.
3. After the printed matter is glazed, the surface is sticky and dry:
main reason:
A, the UV power is not enough
B, UV lamp aging, weakened
C, UV varnish initiator is not properly selected
D, ethanol, toluene and other solvents added too much
E, the machine paper speed is too fast
F, UV varnish has poor photo-solid properties
Solution:
A, timely maintenance of equipment and replacement of lamps
B, adding a certain amount of photoinitiator and photosensitizer, such as ternary amine to accelerate photo-fixation
C, adjust the printing process
4, uneven surface coating, streaks and orange peel phenomenon:
main reason:
A, UV varnish viscosity is too high
B, the pressure is not uniform
C, the coating amount is too large
D, the leveling property of UV varnish is poor
E, the paper is not flat, and the absorption is too strong.
F, UV varnish surface is poorly flat
Solution:
A, reduce the viscosity of UV varnish
B, reduce the amount of coating, and adjust evenly in the dark
C, can add a small amount of leveling agent
D. Corona treatment of the surface of the printed matter to increase the affinity of the UV varnish to the surface
5, UV coating has pinhole phenomenon:
main reason:
A, the coating is too thin
B, the anilox roller is too thin
C, ethanol, toluene non-reactive diluent added too much
D, the surface of the print has dust
Solution:
A. Strengthen the cleaning of the working environment
B, can add a small amount of leveling host additives, wetting additives
C, choose a special UV thinner to dilute, prevent system components from being incompatible
D, try to increase the thickness of the coating when printing
6. The main reasons for the crater and fisheye on the surface of the printed matter:
A, the surface of the printed matter is unclean, there may be oil stains
B, poor leveling of UV varnish
C. The defoamer of varnish is not properly selected, and the defoaming performance is too strong.
Solution:
A. Clean the surface of the printed matter B. Reasonable use of defoaming and leveling additives
7, UV varnish adhesion is not good Main reasons:
A, the surface of the printed ink "crystallized" and varnish can not be affinity, wet
B, the choice of accessories in the printed ink is not suitable
C, UV varnish itself is not enough adhesion
D, the light curing conditions are not reasonably mastered, and the curing time is too short or too long
E. For unpolarized or low polarity substrates (such as PE, PP, PET, OPP, BOPP, etc.) untreated direct printing UV varnish
Solution:
A, printing ink should choose the model with lower wax
B. Select a photo-curable resin and reactive monomer with good flexibility and good adhesion.
C. Master a reasonable curing time, the curing time is too short, the surface of the UV varnish is solidified and the underlying curing is not completely caused by the adhesion; the curing time is too long, and the UV varnish excessively receives the ultraviolet ray to cause the aggregation and post-cure, so that the glazing The film is brittle, resulting in poor adhesion. 8. The main reason for the poor toughness of the glazing film layer:
A, UV varnish own resin, active monomer is not properly selected
B, the glazing coating is too thick
C, the curing process is not properly mastered
Solution:
A. Select a photo-solid resin and reactive monomer with good toughness, control the amount of monomer, and reduce cross-linking and density.
B. In printing, screen printing with a large number of meshes is selected to reduce the thickness of the coating.
C, master a reasonable curing time