Viscosity is also called stickiness (stagnation) or internal friction. A characteristic of a fluid (including liquids and gases) that hinders its relative flow. When a liquid is agitated, its flow rate is proportional to the used force (shear stress) = constant X shear rate.
The viscosity is mainly determined by the composition of the ink. If the viscosity of the binder in the ink is large, the viscosity of the ink is also large; in addition, the solvent content is large and the viscosity is small; the pigment content is large and the viscosity is large; the higher the workshop temperature, the lower the meal degree and many more.
The viscosity of ink is also called tackiness: it means that during the printing process, between the ink set and the ink roller, between the ink roller and the printing plate, between the printing plate and the object to be printed, when the ink film layer separates, the ink There is a force in the molecule that resists the separation of the ink layer, which is called the adhesion of the ink.
The low viscosity of the ink, from the printed paper, will cause the connecting material to penetrate too much into the paper, making the printed product lack of gloss, affecting the fixation of the print.
From the perspective of printing, the thin layer formed is too thin, which makes the color and gloss of the printed product thin. If the ink viscosity is too high. Printing paper and plastic will cause poor ink transfer, uneven ink filling, and even the phenomenon that the printing plate network cable is blocked. Therefore, the viscosity of the ink must be moderate.
Printing paper is adjusted with ink oil. When it is necessary to increase the viscosity of the ink, add No. 0 ink, and when it is necessary to reduce the viscosity, add No. 6 ink. Plastic film gravure printing and flexo printing, color plastic film quick-drying thinner and slow-drying thinner to adjust ink viscosity. Viscosity is related to printing speed. The higher the printing speed, the lower the viscosity.
Flexographic ink is more viscous than gravure ink. Gravure ink pigment content is 10-30%, viscosity (poise) 0.5-10; soft ink pigment content is 10-40%, viscosity (poise) 1-100.
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