Printing ink in flexographic printing with water-based ink can, solvent-based inks and UV inks. The quality of water-based inks has been greatly improved and harmless to the environment. Therefore, more emphasis has been placed on flexographic printing. Water-based inks today have almost as much print quality on paper as solvent inks. The water-based ink does not contain volatile organic solvents. It is proved to be a more suitable flexo ink by virtue of its abrasion resistance, printability, ink layer characteristics, and increased value of the outline points.
The printability of water-based inks should be suitable for printing inks that can achieve the desired ink layer thickness, print clearly, without markings, do not make water, non-stick, 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 binder, which allows the ink to flow and allows the pigment to adhere to the surface of the paper after drying. More than one type of pigment is often used when formulating inks, and the binder is often composed of several liquid materials. Be cautious when choosing ink ingredients, so that the formulated ink has the following characteristics:
1. The ink must contain enough pigment to print a dense, solid color.
2. The ink composition is dispersed evenly, and there is no unevenness of density when it is stored or used on the ink roller.
3. The printing should be cured and dried within the specified time, not sticky.
4. Have the desired printing fluidity.
5. Segmented ink performance is good.
6. Can be adhered to the designated 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, ultraviolet rays, 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)
Key ink film with a high concentration of ink in the case of film properties to ensure that the ink color strength of the ink film should be as thin as. This requires increasing the content of the pigment in the ink and the viscosity of the lowering binder. Another 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 density inks can be printed with a fine profile roller and a squeegee to obtain a thin ink film while maintaining a high viscosity. The printed sheets are of good quality and low cost. The volume of the roller of the stand roller and the line number of the line play a very important role. In order to obtain the desired printing effect with a fine roller, the viscosity of the ink must be moderate. The more number of outline lines, the higher the viscosity should be. However, the viscosity must be stable, and if the viscosity is too low, it will cause the stencil phenomenon to occur. High viscosity is easy to stick. In order to obtain the best print quality, the viscosity of the ink should be carefully adjusted. Do not use random solvents or water to infiltrate the ink to change the viscosity of the ink. Care should be taken to measure the amount of the ink, 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 polyamide inks with high solids content are used, the first step to improve printability is to check the solvent used to dissolve the resin and see if the solvent can make the binders have lower viscosity and lower surface tension. With extremely strong compatibility, does the last-used solvent evaporate from the ink?
In order to print clean, uncontaminated sheets, inks with good dissolving and re-dissolving properties should be used, so that the dried ink on the roller and the plate will be dissolved by the newly used ink, and the ink will not be deposited on it. Plate or dry solid on the 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 outline points will be damaged or lost when printing the outline; when printing solid colors, the quality of the ink transfer may be adversely affected, resulting in uneven printing or the generation of small holes. The drying speed of the ink is too slow, and the growth of the outline is more significant. At the moment of imprinting, if the ink color 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. In other words, there should be successively different drying speeds. The ink that is used first has the fastest drying speed, and the ink that is used later has a slower drying speed, but it should not be too slow, so as not to cause stickiness or bleeding.
(to be continued)