Common printing failures and processing methods for gravure inks
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1.A53 type/A54 type ink has poor reproducibility
Reason: First, the viscosity of the ink is too low, resulting in poor transferability of the dark-adjusted part, and even the contrast of the level tends to decrease. Second, the ink is excessively permeated due to plastic unevenness or rough paper. Third, the gelation of the ink or the poor pigmenting power of the ink system leads to poor reproducibility of the printed ink film.
Treatment method: First, the proportion of pigment in the ink system is appropriately larger or a pigment with high coloring power is selected as a coloring agent, and the second is that the printed (web) cell is shallower at the time of plate making. The third is to increase the proportion of wetting and dispersing agent to improve its color development. Fourth, an anti-freezing organic solvent such as propylene glycol butyl ether or the like is appropriately added to avoid gelation and maintain the fluidity of the ink. Fifth, a non-surfactant such as stearic acid is appropriately added to prevent the ink from being affected by the penetration of the ink, especially the transfer property.
2. Ink film appears fog and paste
Reason: First, water intaglio (A53, A54) inks are printed at high speed (150 ~ 300m / min), resulting in fog or paste. This is often due to the slow drying of the ink, especially in the ink system, the water-based binder and the medium of the water or the formulation of the organic solvent of the ester and the organic solvent are unreasonable, resulting in the matte or fogging of the surface of the ink film after printing. shape. Second, due to the poor solubility of the thinner and ink, the solubility is poor after the addition, and the dried ink on the plate increases the resistance of the scraper or the paper powder on the substrate, and the paste caused by the mixing of the plastic powder.
Treatment methods: First, improve the accuracy (centality) and surface finish of the plate; second, increase the pressure of the blade; third, adjust the solubility of the diluent and ink.
3. Slow ink drying
Reasons: First, the slow drying of the ink is often caused by the slow evaporation rate of water. Usually, the ink is too thick or the ink film is too thick or the non-absorbent plastic, aluminum foil, etc. does not absorb the ink. It is caused by the condition of no wind or no drying equipment (including facilities) or drying (including infrared magnetic wave drying power), and so on.
Treatment method: First, it is to improve the ordinary hot air blowing method. The temperature of the hot drum type is 20~30°C higher than that of the solvent type; the second is the frequency of the electromagnetic wave heated by the high frequency dielectric in the past is changed from 10 to 150MHz to 300~3000MHz. Microwave heating and drying method; the third is to use preheating to improve the surface temperature of paper or plastic or aluminum foil for packaging printing; the fourth is to increase the ambient temperature (especially the printing plate).
4. Poor adhesion fastness
Reasons: First, the substrate is not processed well; second, the wrong ink is used; third, the ink system contains excessive surfactant; fourth, the printing pressure is too small; fifth, the ink viscosity is not suitable; sixth, the ink film remains excessive moisture or Solvent.
Treatment: First, re-process the substrate; second, change the appropriate ink; third, choose ink without surface activity; fourth, increase printing pressure; fifth, select ink with high resin content and low viscosity; In the ink system or in the thinner formula design, the gradient forming mixed solvent should be used as much as possible or the printed product should be cut into the drying room to remove excess water.