Flexo printing for better ink transfer?
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At present, flexographic printing has reached an unprecedented height in terms of smaller high-gloss dots and optimized ink field density. However, in terms of color gamut and tonal range, especially image contrast, printing companies using flexographic printing are often difficult to stand out from the competition with offset and intaglio. In addition, the most challenging is how to achieve the above printing points while keeping the press running at high speed and minimizing downtime.
The accumulated experience tells us that effective ink transfer and minimal printing pressure are the keys to success. That is, the amount of ink capable of achieving the corresponding color density and hiding power is transmitted by the anilox roller having a smaller ink amount, so that the ink adheres only to the area where the ink layer is required to be transferred, thereby enhancing effective ink transfer. This method minimizes dot gain and allows the plate to run longer without wiping.
Achieving better ink transfer does not mean transferring as much ink as possible to the substrate. Increasing the density of the ink and improving the cleanliness of the printing can expand the color gamut range to a certain extent. However, if the density of the ink is too large, the range of color gamut that can be reproduced is reduced, and too much ink can cause a printable color tone. The scope is reduced. This will reduce the contrast of the image, making the appearance of the halftone print blurred. Therefore, the real goal is to increase the density or opacity to the desired target level while ensuring that the maximum color gamut and tonal range can be replicated.
If this goal is to be achieved on a press, the entire mechanism of ink transfer needs to be optimized, including how to transfer the ink from the anilox roll to the plate and how the ink is effectively transferred to the substrate. This period can be affected by many factors, such as the shape and depth of the cell, the material of the printed version, the surface characteristics of the plate, the surface tension of the ink and the substrate, and environmental conditions.
Suppliers in all areas are improving their ink transfer processes by constantly improving their technology. For example, ink manufacturers have optimized the proportion, viscosity, acidity and alkalinity of pigments in inks; anilox manufacturers have developed a variety of cell sizes and sizes, and introduced ceramic meshes. Roller, and is committed to the development of innovative laser and engraving processes, new substrates and coatings have come out. In addition, the printing factory can also use the flame and corona treatment methods to improve the coverage and adhesion of the ink through continuous exploration.
It is worth mentioning that plate suppliers offer solutions for texturing or mechanically texturing the surface of the plate, with the aim of improving the diffusibility of the ink, not just increasing the thickness of the ink layer.
Any of the above methods can increase the density or opacity of the ink. However, in terms of expanding the color gamut and the tonal range and improving the contrast of the image under the premise of the maximum printing amount, each method exhibits different abilities and is in the ink. The same is true for the ability to completely cover the performance of the substrate.
A solid black film is printed on the transparent film. After zooming in, you will find many gaps, holes or voids in the print (see Figure 1). This grid-like appearance may be caused by factors such as the surface tension of the material and the characteristics of the ink, but is mainly formed by the mesh walls separating the cells.
When the ink in these cells accumulates on the surface of the printing plate, the ink flows in the direction of the machine as the printing machine rotates. Unless there is ideal printing conditions, the ink will not easily spread laterally relative to the machine. The usual practice of trying to solve these problems is to increase the amount of ink and increase the pressure on the plate.
All in all, effective ink transfer and minimal printing pressure are key to making flexographic printing comparable to offset and gravure printing. For this reason, the amount of ink required to completely cover the surface can only be minimized without causing an increase in ink filling and transition dots in the non-printing area.
The goal is to print a strong, smooth color on the ground background, using white ink to cover the color of the product or the substrate itself, so as not to affect the image. The key factor is to maintain the openness of the gamut and tonal range in order to maximize image contrast and shelf impact. The solution we are looking for should give the image prints the best ink transfer, extended color gamut and tonal range and dynamic contrast to achieve print quality comparable to the gravure process.