Analysis of several factors affecting the printing effect of water-based ink
Release time:
2024-04-01
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Water-based ink is an environmentally friendly ink with water as a solvent. Compared with solvent-based ink, it greatly reduces the emission of volatile organic compounds (VOC), optimizes the operating environment of the printing workshop, and avoids environmental pollution and harm. At present, water-based ink is mainly used in flexographic printing and gravure printing. Due to its low toxicity, it occupies a considerable proportion in food packaging, pharmaceutical packaging, tobacco and alcohol packaging, children's toys and other packaging and printing fields. Recently, water-based ink has also been used in clothing printing. As a new type of "green printing material", the application of ink in the field of packaging and printing will be more and more extensive, therefore, the development prospect of water-based ink is quite promising, and the research and development of domestic high-grade ink is a top priority. This paper mainly discusses the main factors affecting the quality of water-based ink printing: ink fineness, viscosity, PH value, gloss, color concentration, drying speed and so on.
fineness
The fineness of water-based ink refers to the size of the pigment particles in the ink and the uniformity of the dispersion in the binder. It is usually completed in the process of producing ink paste. It is a very important quality index factor and directly affects the printing quality of ink. In the process of producing color paste, it is best to add dispersants and wetting agents, so that the fineness of ink to meet certain requirements. The fineness of the ink will not only have a certain impact on the tinting strength, hue and other properties of the ink, but also affect the rheology of the ink. Usually the fineness of the ink is better, the concentration is also
The greater the color, the stronger the color, the higher the quality of the product printing. On the other hand, the fineness of the ink is low, the pigment particles are coarse, the friction coefficient is large in the printing process, and the printing rate of the printing plate is low. And coarse particles of ink, in the printing dot pattern, easy to cause dot edge hair or emptiness, and may lead to paste plate, ink accumulation and ink transfer, ink distribution of uneven ills; but if the ink particles are too fine, the ink flow is too large, will cause dot expansion, will also affect the printing quality. Fineness according to GB/T13217.3-91 detection, general ink fineness in 5~25 microns.
Viscosity
Viscosity is the most important control indicator factor in water-based ink applications and is a property that prevents fluid flow. Since the viscosity directly affects the transfer and printing quality of the ink, it is very important to control the viscosity of the ink. In the printing process, the viscosity of water-based ink will affect: ink on the substrate spread, dot expansion rate, image gradation level of reproducibility, print color strength and so on. The viscosity of water-based ink is too low, it will cause the ink to produce a slow expansion before drying, or cause ink
Uneven spreading leads to uneven ink film, resulting in low gloss, light color, dot expansion, uneven ink transfer and other ills. However, if the viscosity of water-based ink is too high, the transfer performance of ink will be poor, and it will be difficult to transfer to the printing plate during printing, resulting in poor color strength of printed matter, and at the same time, dirty version, paste version and other ills will easily occur. Viscosity according to GB/T13217.4 detection, domestic commonly used coated 4# cup to measure viscosity, is a more convenient and accurate detection method. Generally, the viscosity is controlled at about 20 "(coated with 4# cups), the viscosity of ordinary ink is generally 50" ~ 65 "/25 ℃ (coated with 4# cups), and the viscosity of high-grade ink is controlled at 25" ~ 35 "/25 ℃ (coated with 4# cups). In a specific application, the size of the viscosity control must also be determined according to the condition of the substrate and the type of equipment and the printing speed. The faster the speed, the smaller the viscosity should be. Printing line products, in order to ensure the clarity of the dot, the viscosity can be slightly larger; and printing field products, the viscosity should be smaller, making the ink layer spread better.
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