For example, if the particle size is too large, the ink cannot be transferred smoothly during the printing process, which may cause the screen clogging or ink accumulation of the squeegee during screen printing. The ink may also be thickened, which affects the printing color and printing uniformity. . On the other hand, if the particle size is too small, it will easily cause diffusion of light, which will cause the ink to lose its metallic luster and cause the printing effect to be not bright.
Experiments show that when screen printing, the mesh size should be about 3 times the average size of metal particles. The metal foil particles in the metallic ink can smoothly pass through the mesh under the action of a scraper. The average size of general metal ink particles is 15-20 μm, and the principle is that the mesh size should be about 3 times the average size of the metal particles. The screen mesh used should have a mesh size of at most 400/mm (its mesh size is about 60 μm). ), but with a 400/inch mesh, precision is not.
There are obvious dog teeth in the picture and text, but if you want a clear picture, you must sacrifice the shiny effect of large particles, and switch to fine-grained metal ink in exchange for a smooth print.
Distribution of metallic pigment particles
In addition, the particle distribution of the metallic pigment is also a factor that affects the optical properties of the metallic ink. When using different manufacturers of metal inks, although the particle size shown in the technical data is the same, the hiding power and metal gloss of metal inks after printing may sometimes differ greatly because different ink manufacturers are manufacturing metal inks. The particle distribution of the metallic pigment is sparsely dense.
The same average particles, the denser the distribution of particles, the more uniform the overall arrangement of the pigment, the better the gloss and hiding power of the produced metal ink, so the different metal pigment manufacturers technology for the distribution of particles, will be the metal ink The effect has a great influence.
The uniform distribution of the metal sheet is based on the characteristics of the resin and the solvent in the ink. A good resin allows the metal sheet to be distributed very evenly. However, using a poor resin ink, the metal particles are unevenly distributed. Now, under the microscope, it can be seen that the metal pieces stick together and it is very difficult to distinguish the individual particles, so that the metallic gloss effect of the printed matter is greatly reduced.
Metal ink innovation
The shape of the metallic pigment particles in the conventional metallic ink is irregular, but due to the irregular shape of the metallic pigment particles and the edges are not smooth, the specular reflection effect of the particles is poor, and the diffuse reflection of the edges is severe, so the metallic luster and covering of the metallic ink are covered. The force is also poor. The new metal pigment is a nearly circular structure with uniform size and mirror reflection, while the metal effect and hiding power are excellent.
In addition, some new metal inks contain more long-sized particles in the metal flakes. Under the premise of satisfying the size, the particles of this shape can reduce the thrust required for the particles to move in the ink medium, thereby achieving The purpose of reducing the ink viscosity. Because the metallic ink does not make the ink sticky due to the increase in the fineness of the particles.
This is mainly due to the fact that the required energy is higher when the metal sheet is rotated or oscillated during the flow, and the larger particles need a lot of force when they move in the ink medium, so the viscosity of the ink is increased. If the ink is too thick, not only will the ink be affected by the mesh of the screen, but also the uneven density of the print and the phenomenon of sheeting will occur on the gravure or flexo plate. (To be continued)