New metal ink research and application features

The new metal ink uses a large metal foil to reflect light to give metallic ink a gloss. For many years, metal inks were screen printed to produce metal gold or silver luster. Due to the slow screen printing speed and the slow printing speed, the cost of silk screen printing increases, and due to the improper use of the metallic ink during printing, defects such as poor ink drying, ink stacking and dullness are easily caused. The new metal inks are usually UV-UV inks and water-based inks. When these metal inks are printed on a sheet-fed offset or flexo printing machine, they can not only avoid the disadvantages, but also can be formulated according to needs. Colors.

Metal inks rely on the reflection of light by the metal foil particles to make the metal ink glossy. If the metal foil particles are large, more light is reflected and the metal effect of the ink can be better enhanced. Too fine metal particles, one is easy to cause the diffusion of light, so that the ink loses its metallic luster; second, it is easy to oxidize, not to mention the metallic luster.

In screen printing, the metal foil particles in the metallic ink must not be too large due to limitations of screen printing and screen printing processes. It is well known that in screen printing, the screen size of a screen determines the accuracy of the print, and also determines the size of the screen. The higher the number of meshes, the smaller the mesh size. The high-precision printing products require high-mesh screens. If the mesh is too low and the meshes are too large, the margins of the printed products will appear jagged, affecting the accuracy of the images and texts. However, if the size of the mesh is too small, the passage of larger particles in the ink will be blocked, and in severe cases, the color density of the printing will be reduced. Moreover, even if this is not the case, due to too many particles in the screen, the ink on the squeegee will gather too much and must be cleaned. This will cause work to stop, which is not worth the candle. Practice shows that the size of the mesh should be about 3 times the average size of the metal microchip, which is appropriate. At this time, the metal foil particles in the metallic ink can smoothly pass through the screen plate under the effect of the scraper. The average size of the general metal ink particles is 5 to 12 μm, and the principle is that the mesh size should be about 3 times the average size of the metal micro-sheet. The screen mesh used should have a mesh size of at most 275 L/cm (its mesh size is 33 μm). , obviously printed with 275L/cm mesh, the accuracy is not enough.

New metal inks can be used for sheetfed or flexographic printers, without the limitations of screen meshes, so they can be enhanced by the use of larger metal foil particles that use the light reflected by large foil particles The metallic effect of the ink, but due to the influence of the metal flake on the viscosity of the ink, the flake particles in the metallic ink cannot be too large. Metallic inks Unlike the organic pigment inks that we generally know, metallic inks do not make the ink thick because of the increased fineness of the ink particles. This is mainly because the required energy is higher than that of ordinary particles when the metal sheet is rotated or swayed during the flow. Larger micro-sheets need a large amount of thrust when they move in the ink medium, so the viscosity of the ink is required. Increased, if the ink is too thick, it will produce uneven printing density and filming. On the other hand, when the tiny microchips require only a small amount of thrust, the flow will be smooth and natural, and the viscosity will be very low. Larger metal microchips can better enhance the metallic effect of the ink, but in order to achieve low viscosity and print uniformity, smaller microchips are often required. Generally speaking, the size and shape of the metal sheet in the ink is not the same. In order to obtain a good printing effect, the metal sheet particles in the new metal ink are mostly long strips of micro-sheets, and the micro-sheets of this shape are satisfied. Under the premise of size, the thrust required for the movement of the microchip in the ink medium can be reduced, thereby achieving the purpose of reducing the ink viscosity.

Another feature of the new metallic ink is that it can effectively avoid the chemical reaction of the water-based ink with the same water-based ink carrier (ink fountain or other). This corrosive chemical reaction will often affect the storage and gloss properties of the ink, so the new The metallic ink is not only more metallic than the traditional metallic ink, but also can be matched with various colors of ink according to the needs, producing various metallic inks such as red, green, and blue, but it is necessary to pay attention to the arrangement of the color sequence when it is used, such as Improper arrangement will not only fail to achieve the desired results, but will also lead to the occurrence of printing failures.

Metal inks have many differences compared to ordinary inks. Most common inks are first mixed with dyes and then ground by a ball mill or roller mill before they are finished. However, it can be different for metallic inks. Its mixing process is very gentle and cannot be ground. The grind will cause the ink to lose its metallic luster. In addition, the composition of the metallic ink is very different from the ordinary pigment ink. The metallic ink is composed of a sheet-shaped micro-metal body, and the volume is larger than that of the particles in the common organic pigment ink. When printing, it is also necessary to make the ink sheet-like coating to achieve the reflection effect of the metal microchip. In contrast, organic inks are required to fully infiltrate organic ink particles in order to achieve enhanced adhesion and produce bright results. Another issue that needs attention is the uniformity of the distribution of the metal sheet in the ink medium. If the metal sheet is evenly distributed in the ink medium, the printing will achieve the best metal effect. The uniform distribution of the metal sheet depends on the characteristics of the resin and the solvent in the ink. A good resin can distribute the metal flakes very evenly. If you look under the microscope, you can see this distribution, and its printing effect is very good. However, the use of poor resin ink, its metal micro-distribution is very uneven, the observation under the microscope can see that the metal sheet is sticky, distinguishing a single micro-chip is very difficult, so print the printed matter , Its metallic luster effect will be greatly reduced.

Of course, specific issues need to be analyzed specifically. Different inks will have different performance capabilities on different prints. When using the best long-length water-based metal inks, different inks must be selected according to different products. Recipe.


Source: School of Information Engineering, Jiangnan University, Guangdong Printing