Screen printing suitability of the latest metal in

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Silk printability of new metal inks

new metal inks use large metal sheet particles to reflect light and make metal inks shiny. For many years, metallic inks have been printed with silk to produce metallic gold or silver luster. The cost of silk printing rises due to the slow speed of plate and printing, and due to the improper use of metal ink in printing, it is very easy to suffer from the disadvantages of poor ink drying, ink stacking and lusterless. New metal inks are usually UV ink and water-based ink. When using sheet fed offset printing machine or flexographic printing machine to print, this kind of metal ink can not only avoid those disadvantages, but also mix various colors according to needs

metal ink is made shiny by the light reflected by the metal sheet particles. If the metal sheet particles are large, the reflected light is more, which can better enhance the metal effect of the ink. Too fine metal particles, one is easy to cause light diffusion, so that the ink loses its metallic luster; Second, it is easy to oxidize, let alone produce metallic luster

in silk printing, due to the limitations of plate and silk printing process, the metal sheet particles in metal ink should not be too large. As we all know, in silk printing, the size of the plate determines the accuracy of the printed matter, but also determines the size of the hole. The higher the mesh number, the smaller the hole size. However, high-precision prints need a high-quality version. If the mesh is too low and the hole is too large, the edge of the print will appear jagged, which will affect the accuracy of the text. However, if the size of the hole is too small, the passage of larger particles in the ink will be blocked, and in serious cases, the printing color density will be reduced. In addition, the service life after each verification is 2 years. Even if this does not happen, because there are too many particles in the screen, the ink particles on the doctor blade will gather too much and have to be cleaned, which will cause work stoppage, which is not worth the loss. The practice shows that the size of the hole should be about 3 times the average size of the metal microchip, which is more suitable. At this time, the metal sheet particles in the metal ink can pass through the plate smoothly under the action of the scraper. The average size of general metal ink particles is 5~12 μ m. According to the principle that the size of the hole should be about 3 times the average size of the metal microchip, the mesh of the wire used is at most 275l/cm (its hole size is 33 μ m) Obviously, the accuracy of printing with 275l/cm mesh is not enough

because the new metal ink can be used in sheet fed offset printing machine or flexographic printing machine, there is no limitation of noise due to aging equipment. Therefore, larger metal sheet particles can be used to better enhance the metal effect of the ink by using the reflection of light from large metal sheet particles. However, due to the influence of metal chips on the viscosity of the ink, the metal sheet particles in the metal ink cannot be too large. Metal ink is different from the organic pigment ink we usually know. Metal ink will not become viscous due to the increase of ink particle fineness. This is mainly because when the metal sheet rotates or swings in the flow process, the energy required is higher than that of ordinary particles. Larger micro sheets need a lot of thrust when moving in the ink medium, so the viscosity of the ink will increase. If the ink is too thick, uneven printing density and flake phenomenon will occur. On the contrary, the flow of small micro pieces can be smooth and natural with only a small thrust, so the viscosity is very low. A larger metal microchip can better enhance the metal effect of the ink, but in order to achieve the effect of low viscosity and printing uniformity, a smaller microchip is often required. Generally speaking, the size and shape of the metal sheet in the ink are different. In order to achieve a good printing effect, the metal sheet particles in the new metal ink are mostly long strip-shaped microchips. On the premise of meeting the size, this shape of microchips can reduce the thrust required by the microchips when moving in the oil and ink medium, so as to achieve the purpose of reducing the viscosity of the ink

another feature of the new metal ink is that it can effectively avoid the chemical reaction between the water-based ink and the same water-based ink carrier (ink bucket or others). This corrosive chemical reaction often affects the storage and gloss characteristics of the ink. Therefore, the new metal ink not only has the excellent characteristics of graphene metal gloss than the traditional metal ink, but also can be reasonably matched with all kinds of inks according to needs, Produce red, green, blue and other colors of metal inks, but when using, we must pay attention to the arrangement of color sequence. If the arrangement is improper, it will not only fail to achieve the expected effect, but also lead to printing failure

There are many differences between metal ink and ordinary ink. Most ordinary inks are first mixed with dyes, and then ground by ball mill or roller mill before being made into finished products. But for metal ink, it is different. Its mixing process is very gentle and cannot be ground, because grinding will make the ink lose its metallic luster. Moreover, the composition of metal ink is very different from that of ordinary pigment ink. Metal ink is composed of sheet micro metallic bodies, and its volume is larger than the particles in ordinary organic pigment ink. When printing, the ink should also be coated in sheets as much as possible to achieve the reflection effect of metal microchips. In contrast, organic inks need to make organic ink particles fully infiltrate and mix in order to achieve the effect of enhancing adhesion and producing brightness. Another problem that needs to be paid attention to is the uniformity of the distribution of metal sheets 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 solvent in the ink. Good resin can make the metal sheet distribute very evenly. If you observe it under the microscope, you can see this distribution mode, and its printing effect is very good. However, for inks made of poor resin, the metal flakes are unevenly distributed. Under the microscope, it can be seen that the metal flakes are glued together, and it is difficult to distinguish individual flakes. In this way, the metallic gloss effect of printed products will be greatly reduced

of course, specific problems need to be analyzed in detail. Different inks will have different performance abilities on different prints. When using the best long strip water-based metal ink, we should also choose different formulas according to different prints

Guangdong printing, 2004, issue 5

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