Water-based ink in water as a kind of environmental printing ink solvent, compared with solvent ink, greatly reduce the organic volatiles (voc) row to put, optimize the operating environment of the printing shop, but also avoid the pollution to the environment and harm.The water-based ink is mainly used in flexible printing and gravure printing, due to its low toxicity, in food packaging, pharmaceutical packaging, tobacco packaging, children's toys occupies a large proportion of the packaging and printing field, recently in the clothing also began to use water-based ink in print, as a kind of new green printing material, ink will be more and more widely applied in the field of packaging and printing, and prospects of the development of water-based ink quite bullish, research and development of domestic high-grade ink painting is the top priority.
This paper mainly discusses the main factors affecting the quality of water-based ink printing: printing ink fineness, viscosity, PH value, concentration of gloss, color, drying speed, etc.
Water-based ink fineness is refers to the size of the printing ink pigment particles and dispersed evenly in the connection of material, usually done in the process of production of ink printing ink, it is a very important quality index factors, directly affect the printing quality of the ink.In the process of production of printing ink to join the best dispersant and wetting agent, makes the fineness of the ink to certain requirements.Fineness of the ink may not only for ink tinting strength, hue, such as performance have influence, will also affect the rheological properties of ink.Usually the better ink fineness, the greater the concentration, the stronger the tinting strength also, the higher printing quality.On the other hand, the ink low fineness, pigment particles, the coefficient of friction in the process of printing, plate printing resistance rate is low.And particle coarse ink, when printing dot design, easy to cause the network edge hair or empty, and could lead to paste version, JiMo uneven ink and ink, cloth disease;But if ink particles is too thin, ink liquidity is too large, will cause dot enlargement, will also affect the printing quality.Fineness according to GB/T13217.3-91 test, general fineness of the ink in the 5 ~ 25 microns.
Viscosity of water-based ink is applied in the main control factors, is one of the types of the fluid flow properties.Due to the viscosity directly affects the transfer of ink and printing quality, so it is important to control of the ink viscosity.In the process of printing, water-based ink viscosity will affect: ink spreadability on substrates, network expansion rate, and the image of the levels of reproducibility, print color intensity, and so on.Water-based ink viscosity is too low, can make the ink in a dry before a slow growth, or the cause of ink spreading caused by uneven ink film is uneven, resulting in low gloss, color shallow, dot enlargement and uneven ink transfer of disease;And high viscosity of water-based ink, ink transfer performance is poorer, printing is difficult to transfer to a plate, cause color print strength is poor, and prone to dirty version, paste version.Viscosity according to GB/T13217.4 detection, domestic commonly used tu 4 # cup to measure viscosity, is a more convenient and accurate detection method.Usually viscosity control in 20 or so "(tu 4 # cup), ordinary ink viscosity in 50" 65 "/ 25 ℃ (tu 4 # cup), high-grade ink viscosity control in" 25 ~ 35 "/ 25 ℃ (with 4 # cup). In the specific application, the size of the viscosity control must be according to the situation of the substrates and the type of equipment as well as to determine the printing speed, the faster the speed, the smaller the viscosity should. Cable products, in order to ensure the site clear, viscosity can be slightly bigger; the printing field product, viscosity should be smaller and make the ink layer spreading property is better.