A high quality flexographic water-based ink must have the characteristics
Date: Sep 04 2023 From: Star Color
Stable pH value
The pH value of water-based ink is actually as unstable as the sawtooth curve.In order to stabilize, it is necessary to shorten the time of measuring pH value and adding stabilizer, that is, to increase the frequency of measuring pH value and adding stabilizer.Therefore, foreign label printing companies often use pH real-time control devices to measure pH values and add stabilizers at any time to maintain the stability of water-based ink performance.
The pH value of water-based ink is stable, and most of the water-based ink PH is between 8.5-9.5, and if it fluctuates between 8.25 and 8.5, the service is smaller.This water-based ink is more stable, with better transferability and viscosity (due to the high latent heat of water evaporation, the possibility of water evaporation in water-based ink causing an increase in ink viscosity is very low, and the increase in ink viscosity is often due to the evaporation of ammonia leading to a decrease in pH value), so the color concentration is stable.
Reasonable viscosity
In order to ensure that the ink stored in the anilx roller mesh hole is transferred to the plate smoothly, low-viscosity ink similar to the gravure process must be used, otherwise it is difficult to suck out the ink in the mesh hole.However, because the characteristics of flexographic anilox roller mesh holes are very different from the characteristics of electric engraving intaglio inverted pyramid mesh holes, the viscosity of flexographic UV ink does not need to be as low as gravure ink.
When developing water-based ink for flexible printing abroad, low viscosity single resin is used to achieve the current printing effect of water-based ink for flexible printing.Flexible printing water-based ink viscosity is reasonable, there is no need to deliberately pursue low viscosity.Imagine that the ink transfer mechanism of a flexible press is the same, but the drying mechanism is different.In this case, we do not need to reduce the viscosity of flexible printing water-based inks.
Increase the color concentration appropriately
The quality of flexible printing is limited by anilox roller technology.In order to achieve a high-lines printing, the anilox roller must also use a high number of lines.According to the optimal ratio of mesh depth to mesh opening in anilox roller technology, when the anilox roller has a high number of lines, the ink storage capacity will correspondingly decrease, and the BCM value will be relatively low.At this point, if we want to pursue high line count and high color density on the same printed matter, we must increase the color concentration of the ink.In short, we must increase the pigment ratio of the ink.
The pigment proportion of flexographic water-based ink is generally 25%, the pigment proportion of Zhongzhixing water-based ink can reach 35%, and the pigment proportion of flexographic solvent-based ink is about 20%.Due to the fact that the surface tension of soft printing solvent based inks is generally lower than that of soft printing water-based inks,its transfer rate from printing is slightly worse, and the color density of solvent-based inks with the same pigment ratio is slightly lower than that of water-based inks.Therefore, compared to water-based ink for flexographic printing, the requirement for the color concentration of flexographic water-based ink only increases the proportion of pigments.
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