Characteristics of printing ink
Liquidity: refers to the ink under its own gravity, will flow like a liquid, by the viscosity of the ink, yield and thixotropy of the decision, but also with the temperature is also closely linked. Ink flow affects the ink from the container, can pour from the ink storage tank in conveying to ink printing machine, smooth transmission, from the ink fountain on a printing press for good distribution, to the layout of the transfer and transfer to the substrate, but also affects the printing effect."Length: refers to the ink at the beginning of stretch without breaking the filamentous, its length by the degree of thixotropy, yield value and plastic ink viscosity. "Short is the good performance of the ink printing ink in offset printing and letterpress printing, ink flying will not cause the phenomenon, in the printing process in China at the same time, the printing ink layer is uniformly thick. "The length is a commonly used method to measure the performance of ink.
Thixotropic ink: refers to the external force of mixing with the stirring action by the thick thinning, when stirring motion stops, and return to the original time consistency phenomenon. The thixotropic ink, the ink by the rotation of the roller in the printing machine, will increase the liquidity, increase the ductility, easy to transfer ink; when the ink is transferred to the paper after printing, lost the effect of external ink changed from thin to thick but not around to flush, the formation of good imprinting. If the thixotropism is too large, the ink in the ink is not easy to turn, will affect the function of the ink roller.
Yield value: the minimum moving stress needed to direct the flow of liquid. Ink yield value is too large, liquidity will become worse, but not easy to open, the yield value is too small, the printing of dot and easy to halo, and the printed matter is not clear. The magnitude of the yield value is related to the structure of the ink, and has a direct impact on the flow of ink. It is an important indicator of the quality of offset printing and gravure printing ink. Generally speaking, the pigment particles in the ink increase, the amount increases, and the force and viscosity that hinder the flow of liquid will also increase. For example, the letterpress printing and flat printing inks used in packaging and printing contain large amounts of pigments, and their forces must be greater than a certain value to flow. Therefore, the force of the ink must be greater than a certain value to flow, this value is the yield value of ink.
Ink is a kind of pulp with a certain fluidity. The viscosity, negative value, thixotropy, fluidity and dryness all determine the properties of the ink.Viscosity: a property that prevents the flow of fluid. It is a measure of the relative motion of molecules between molecules of fluid, i.e., resistance to fluid flow. There are significant relationship between nature and structure, transfer paper and ink viscosity and ink in the printing process, the ink viscosity is too large, the transfer of ink in the printing process is not easy to be uniform, and the occurrence of paper galling phenomenon, the layout of hair; ink viscosity is too small, easy emulsification, dirty, affect the quality of printing products the. In the printing process, the requirements of the viscosity of the ink depend on the printing speed of the printing press, the degree of public software on the paper structure, the changes of temperature and humidity in the surrounding environment, and so on.
