Printability and Variable Factors of Paper (3)

The printability of water-based inks should be suitable for printing inks that can achieve the required ink layer thickness, print clearly, without markings, do not make water, not sticky, do not paste version, non-graphic part is not sticky ink. Printing quality is the result of the combined effects of ink, paper, printing processes and printing equipment. In short, the ink consists essentially of two parts. The first part is a pigment that adheres to the surface of the paper to produce the desired visual effect. The other part is the link material, which can make the ink fluidity, and make the paint adhere to the surface of the paper after drying. More than one kind of pigment is often used to formulate the ink, and the link material is often composed of several kinds of liquid substances. Be cautious when choosing ink ingredients, so that the formulated ink has the following characteristics:
1. The ink must contain a sufficient amount of pigment to print a dense, solid color.
2. The ink components are dispersed evenly and there is no unevenness in density during storage or when used on an ink roller.
3. The printing should be cured and dried within the specified time, and it should not be dirty.
4. Has the desired printing fluidity.
5. Segmented ink performance is good.
6. It can be adhered to the specified surface after being wetted as required.
7. According to the need to produce a dark glossy effect or light effect, can be used for overprinting, can be glazing treatment.
8. The dried ink film is resistant to acids, alkalis, water, UV, abrasion, and not affected by alcohol and grease.
9. The odor after drying is minimal, especially when used in food packaging.
10. Does not contain harmful substances (such as toluene)
The key to ink film printing with high-concentration ink is to keep the ink film as thin as possible while ensuring the color strength and ink film properties. This requires increasing the pigment content of the ink and reducing the viscosity of the binder. One point is that the dispersion or wettability of the pigment is better. In most cases, when the pigment has the best wettability, the viscosity is the lowest, and the color depth and color intensity are the maximum.
High-concentration inks can obtain a very thin ink film with fine anilox and squeegee printing while maintaining a relatively high viscosity. The printed sheets have good quality and low cost. The volume of the anilox roller and the number of screen lines play a very important role. In order to obtain the desired printing effect with a fine anilox roller, the ink viscosity must be moderate. The more number of screen lines, the higher the viscosity should be. However, the viscosity must be stable. If the viscosity is too low, the stencil phenomenon may occur. If the viscosity is too high, it is easy to get dirty. In order to obtain the best print quality, the viscosity of the ink should be carefully adjusted. Do not take any solvent or water in the ink to change the viscosity of the ink. The dosage should be carefully measured, and then see how effective it is.
The dry and dry quality of the ink is related to the resin in the binder and the solvent that dissolves the resin. If a polyamide-based ink with a high solids content is used, the first step in improving the printability is to check the solvent used to dissolve the resin and see if the solvent can make the binder have a lower viscosity and a lower surface. Tension and extreme compatibility. Is the final solvent used to evaporate from the ink?
To print clean, unstained prints, inks with good dissolving and re-dissolving properties should be used. In this way, the dried ink on the anilox roller and the printing plate is dissolved by the newly used ink, and the ink is not deposited on the printing plate or the dry anilox roller. The water-based ink printed on the paper is dried and solidified by the ink absorption properties of the paper and the solvent, water evaporation. If the drying speed is too fast, the ink will quickly solidify, and the dots will be damaged or lost when printing dots; when printing solid colors, the quality of the ink may be adversely affected, resulting in uneven printing or small holes. The ink drying speed is too slow and the dot gain is significant. At the instant of imprinting, if the coloring power of the ink of the first color sequence is strong, the ink film is thin, and the drying speed is fast, a good overprint effect will be obtained, that is, there should be successively different drying speeds. The ink used for drying should be used at the fastest speed, and the ink used for drying should be slower, but it should not be too slow so as not to cause dirty or bleeding. (To be continued)