When referring to the variables that affect the color of gravure ink, the industry will first point out that the fineness of the mesh on the mesh cylinder will affect the color. The answer is basically correct but not complete. In principle, the fineness of the mesh does affect the color, but the general gravure printing technicians will consider this problem. In fact, in addition to the fineness of the mesh, another factor that is forgotten is often overlooked. In gravure printing, ink viscosity is often overlooked by printing technicians, and viscosity is even more seriously ignored when formulating formulas. Even ink suppliers and printing houses will have ink color errors due to the effect of viscosity.
The high and low viscosity of the printing gravure ink is related to the printing speed. Generally, the faster the printing speed, the lower the viscosity of the ink will be to meet the high-speed operation of the printing machine. I once visited a gravure printing factory, and their technicians told me something that surprised me. He said that before the press operator neared work, they would speed up the printing process so that they could finish the work on their hands quickly. Add a large amount of solvent to the ink to reduce the draft and match the operation of the printing press. This does increase the printing efficiency, but the color of the printed matter is not guaranteed. Adding a large amount of solvent to reduce the viscosity will make the color of the printed matter lighter, that is, its printing density or density will be lower than normal. Because when a large amount of solvent is added to the ink, the pigment concentration in the ink (the amount of ink pigment per cubic meter) will decrease in real time. When printing on the same mesh cylinder, the amount of ink pigment per square centimeter of the color of the printed product will naturally decrease relatively, thus making The density or concentration drops rapidly or the color fades. Basically, the formulation of gravure ink must be adjusted according to different printing environment conditions, including printing speed, ink viscosity and mesh fineness.
Generally, after the gravure ink factory produces gravure ink, the stability and transportation cost of the ink are taken into consideration when shipping. The ink is not added with an appropriate solvent at the factory, that is, the ink is delivered to the customer in a state of high concentration and high viscosity. When the printing factory receives the ink, because the ink concentration and viscosity are too high, the technician of the printing factory will add the solvent by itself until the viscosity of the ink drops to the environment suitable for printing. This process leads to two problems. First of all, what criteria do technicians use to determine whether the viscosity of the ink meets the requirements? Most technicians will not use the viscosity flow cup to measure the viscosity. They will use an ink knife or stick to stir the ink, and then move the ink knife or stick together with the ink. Pull, and then feel the viscosity of the ink, so the viscosity of the ink changes by at least one to three seconds without being noticeable. If the viscosity of the gravure ink differs by two seconds, the entire printing color will also change. On the other hand, the quality and concentration of the solvent used by the printing plant may also be different from that of the ink plant. Therefore, the raw material may also change the color of the gravure ink. The ink factory generally only considers using its own solvent when preparing the ink. In fact, printing companies can use the raw materials of ink factories, and then use some standard viscosity testing equipment, such as viscosity flow cups. Moreover, it is necessary to inform the ink factory of the viscosity of the printing before the color matching of the ink factory, so that the ink factory can adjust the formula.
In addition to the viscosity of the gravure ink, the printing house will ignore the problem of whitening. Especially in the printing of plastic packaging, because the gravure ink is printed on the plastic film, its color is often transparent, so the color is more easily affected by the background. Therefore, in the printing process, a layer of white ink is often added to the ink printed with color, that is, whitening. The main reason is to increase the hiding power of the overall ink, making the color opaque and present in the same state. In order to avoid the color deviation caused by the background color. This layer of white ink has already affected the overall color. The situation is like that in lithographic printing, the color of the paper will affect the color of the printed matter and its ink formula. That is, the white ink used for white coating is like white paper, so the set must be clearly understood before color matching White and white ink color to adjust the formula.
Pay more attention to environmental conditions such as printing press speed, ink viscosity, mesh fineness, and whitening. Not only should computer color matching be considered, but even manual color matching should also be considered, so it is very difficult to manually adjust the color formula of gravure ink . During manual blending, the color can often be blended out, but the viscosity cannot be controlled to match the speed of the printing press. Finally, the solvent is added to adjust the viscosity, but the printing color is lighter. Therefore, as long as the computer color matching system can input the relevant environmental conditions such as ink viscosity, mesh fineness, and deposits in advance, the computer can calculate the appropriate formula. This formula can not only prepare accurate colors according to different mesh fineness and printing machine speed, but also control ink viscosity.
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