Printing suitability of ink used by brochure printing factories

Printing suitability of ink used by brochure printing factories

The printability of ink refers to the performance of ink that matches printing conditions and is suitable for printing operations. The printability of ink mainly includes viscosity, yield value, thixotropy, flowability, dryness, etc.

(1) Viscosity.

Viscosity refers to a property that prevents fluid flow, measuring the ability of fluid molecules to interact with each other and hinder their relative motion.

The viscosity of ink is closely related to the transfer of ink during the printing process, and it also requires the properties and structure of the paper to match it. The ink viscosity is too high, making it difficult for the ink to transfer evenly during the printing process, and causing the paper to become rough, resulting in the layout becoming blurred; If the viscosity is too low, the ink is prone to emulsification and dirtying, which affects the quality of the product. The viscosity of the ink is related to the viscosity of the connecting material, the amount of pigment and additives used, the particle size of the pigment and additives, and the dispersion of the pigment and additives. The requirements for ink viscosity during the printing process are related to the printing speed of the printing machine, the softness of the paper structure, and changes in ambient temperature

(2) Yield value.

The minimum shear stress required to initiate the flow of a liquid is called the yield value. Ink with excessive yield value has poor flowability and is not easy to open; Ink with a yield value that is too small can cause blurred and unclear printed dots. The yield value is related to the structure of the ink, and the magnitude of the yield value has a direct impact on the fluidity of the ink.

(3) Thixotropy.

Ink is stirred by external force, and it will change from thick to thin with the stirring effect. After being stationary, the ink returns to its original viscosity, which is called thixotropy. Due to the thixotropy of ink, when the ink is subjected to mechanical rotation on the drum, its fluidity increases and its extension increases, making it easier for the ink to transfer. When ink is transferred to paper through printing, it loses the effect of external force, and the ink changes from thin to thick without flowing around, forming a good imprint. But if the thixotropy of the ink is too high, it will make it difficult for the ink in the ink hopper to transfer, affecting the ink transfer of the ink roller.

(4) Liquidity.

The ability of ink to flow like a liquid under its own gravity is called the fluidity of ink. The fluidity of ink is related to whether the ink can be poured out of the container, transported from the storage tank to the ink hopper of the printing machine, smoothly transferred from the ink hopper, well distributed and transferred to the layout of the printing machine, and transferred to the substrate, which also affects the printing effect. The fluidity of ink is determined by its viscosity, yield value, and thixotropy, and is also closely related to temperature.

(5) Dryness.

After ink adheres to the printed material to form printing marks, it must transform from a liquid or paste to a solid ink film, and this process is commonly referred to as ink drying. The drying of ink is achieved by the transformation of the connecting material in the ink from liquid or paste to solid. The connecting material and its ratio used in various inks are different, so their drying process is also different. After the ink is transferred from the printing plate to the surface of the printed product, a part of the connecting material in the ink penetrates, and the solvent in the connecting material begins to evaporate. Some connecting materials undergo chemical and physical reactions, gradually increasing the viscosity and hardness of the imprinting ink layer on the surface of the substrate, ultimately forming a solid ink film. Usually, relief printing ink is mainly dried by permeation, offset printing fast drying glossy ink is mainly dried by oxidation film, and gravure printing ink is mainly dried by volatilization.

Printing suitability of ink used by brochure printing factories