When the printer orders the ink from the supplier, it is best to submit a sample of the substrate they are going to use. Ink manufacturers can formulate products that can achieve the best results based on the surface characteristics of the sample being printed.
Ink manufacturers can perform accurate composition of submitted sample surfaces and be sure that the complex inks they provide can adhere well to the surface to be printed, especially on coated surfaces. Because the ink analysis technology is currently very advanced, the results of the analysis are also more accurate, this phenomenon because the ink paper industry researchers are also increasing interest in the ink / paper interaction.
At the 1996 TAGA Annual Conference, two papers were read, one on how the paper coating affects the interaction between paper and ink in the offset printing process, and the other on the same issues as the publication of the gravure water-based ink. . The first paper considers smoothness, porosity, and ac- tivity in the surface properties of coated papers as important factors influencing the printing performance, especially the ink splitting mechanism. It found that these properties affected the flow properties of the ink and the viscosity over time (Tack buildUp). Understand the importance of this phenomenon
Because the effect of the final product will be affected by the structure of the coating layer and its chemical properties. The printer needs to understand and explain this phenomenon to the customer. Although highly coated paper may provide improved printing performance and the ability to accept and restore images, there is a loss in optical characteristics, especially in terms of gloss.
Among these variables, the chemical properties of the paper coating involve its binders, dispersed particles, and filler grades such as clay. For these variables, the binder level is the most critical because it has the greatest effect on the viscosity of the ink. The increase in adhesive composition reduces the porosity of the surface, which limits the capillary action of the ink in the paper.
If the ink manufacturer can test the paper used, they can develop the corresponding ink formulation to optimize the printing performance and optical performance of the paper. Problems with using water-based inks
The second paper discussed the issue of how printing performance was affected when gravure printing staff used water-based inks instead of traditional solvent-based inks. There are many benefits to this approach, including low levels of HAP and volatile organic components (VOCs). This ink also reduces press management and insurance costs, and reduces the risk of fire and explosion.
However, the development of water-based inks is very slow, partly because it is not the same as the chemical characteristics of solvent-based inks. If the moisture in the ink expands in the fiber of the material, the printing quality will be affected, resulting in ink glossiness. Decrease and tessellation dot distortion. The problem of drying with water-based inks is more critical than with solvent inks because if the ink is not dry enough, there will be a migration of the ink onto the shut-off roller and this will cause image distortion.
Paper surface properties such as smoothness, hygroscopicity, fastness and surface tension have a great influence on the smoothness of the print. Even if there is a small white spot on the surface of the paper, there may be distortion of the dots. The overall problem with the use of water-based inks is the webbing phenomenon and the ripple phenomenon.
In the second paper, it was also found that changes in the internal dimensions of non-coated paper enhance the printing properties and print quality of water-based inks, and the print quality changes as the degree of dimensional change increases. The effect of fiber expansion can be minimized by making the paper hydrophobic, but print quality may deteriorate quickly.