Intaglio ink printing failures and solutions

1, stripping paper

Symptom: When the paper is peeled off after printing, the paper surface is stuck by ink and one layer is peeled off.

Cause: The viscosity of the ink is greater than the tightness of the paper; or the surface of the paper is loose.

Solution: Use a low viscosity binder as the ink; add a detackifier to reduce the viscosity to an appropriate level. Use good paper instead.

2, intolerance friction

Symptoms: After the prints are dry, the printed ridges are wiped out when they are subjected to various frictions during handling, cutting, and use, and the surrounding blank areas or paper marks are wiped off.

Cause: The ink conjunctiva is too soft and does not dry thoroughly; the ink does not adhere well to the paper after conjunctiva. This problem is most prominent in securities, such as the renminbi, due to the fact that the products are subjected to thousands of times and different occasions. Too much of the wax additive will cause the ink to loosen and the powdered ink film will be less resistant to friction.

Solution: First of all, make ink faster and dry completely. The dried ink should be smooth and certain strength. And have some flexibility. This requires the use of a hard resin and a soft resin that are just right. When using a wax additive, it can't be done. (The wax additive can play a smooth role in a certain range to reduce the friction.) That is, the ink will not be resistant to friction when it is dry. Appropriately increase the pressure so that the ink and paper are tightly bound.

3, wipe clean

Symptom: After the plate is wiped, ink or grease residue remains on the non-patterned part and is printed on a position other than the pattern on the paper.

Cause: When the ink is wiped, the cohesive force of the ink must be considered. The adhesion force between the layout and the ink and the force of the wipe are greater than the adhesion between the layout and the ink and the cohesion of the ink itself is greater than between the layout and the ink. The adhesion of the force, it is easy to clean the layout. When the cohesion of the ink itself is less than the adhesion between the plate and the ink, it will not be clean. Specifically, the viscosity of the ink is too large and the yield value is too large. At this time, the wiping shear force is difficult to exceed the high yield value of the ink, so that the wiping does not occur.

Solution: The ink should be fine and delicate. The addition of a viscosity-reducing agent reduces the viscosity of the ink. At the same time, high-viscosity varnish cannot be used, or the drying time can be reduced. When the grease is not clean, increase the viscosity of the linking material, and use less additives in the wax. When using ink, use a pigment with a small amount of oil absorption.

4, wipe excessive (erase)

Symptoms: Under normal circumstances, the ink in the net points or lines after wiping is slightly lower than the concave concave surface of the printing plate. At this time, the lines appearing on the print are not full and isolated, and the amount of ink in the ink dot and lines is insufficient.

Cause: Too much force is applied during wiping, and if the object to be wiped is large in ink absorption, excessive wiping results; the cohesive force of the ink is too large, or the viscoelastic plasticity is too large, and tends to be wiped off from the pattern portion. Poor ink transfer can also be caused.

Solution: When the force to wipe is appropriate; reduce the viscosity of the ink, add wax adhesion, so that the ink becomes a little loose and not sticky, reduce cohesion, silk becomes "brittle", wipe clean.

5, printing products flash

Symptoms: Netting, irregular lines on both sides, and thick burrs.

Reasons: ink flow is too large, more dilute, more ink, wipe does not meet the requirements, that is, not to the right degree, the pressure is great when printing, the ink is pressure-like flow or paper is pressed into the cable to squeeze the ink and fly Out.

Solution: Replace the ink with good fluidity and viscoelasticity; wipe it so as not to cause excessive ink retention; adjust the light pressure or adjust the pad on the pressure roller.

Source: China Ink Technology Network