1, offset printing water
Generally, water-based offset printing is based on the polarity principle that oil (offset printing ink) and water (wetting liquid) are incompatible.
From the viewpoint of polarity theory, matter is composed of molecules, which are divided into polar molecules, nonpolar molecules and amphiphilic molecules. The molecular (solid geometry) configuration of polar molecules is asymmetric, the center of gravity of molecular positive and negative charges does not coincide, the electron cloud molecules are uneven, and the dipole distance is not zero. The greater the dipole distance, the stronger the polarity. For example, the wetting liquid in water offset printing is a typical polar substance.
2, waterless offset printing
The waterless offset printing plate is a plane intaglio structure, and the blank part of the printing plate is raised and is silicone rubber (low energy surface) that does not absorb ink, while the graphic part has good ink absorption. Obviously, offset printing follows the laws of wetting, adsorption and selective adsorption of interface chemistry.
Extended data:
What we usually call offset printing now, perhaps in a narrow sense, is a three-roll lithography method (printing plate, blanket and impression), which is called offset printing in southern China.
definition
Offset printing is the main way to print paper stickers in label printing plants in China.
trait
Fine graphics and text, rich layers, suitable for mass printing, and printing equipment can be used for multiple purposes, suitable for the characteristics of China label market. However, sheet-fed offset printing is not suitable for printing films with no absorption on the surface, because film labels are mostly roll-to-roll printing, which requires volatile dry ink.
Blanket plays an irreplaceable role in printing, for example, it can make up for the unevenness of the substrate surface, make the ink fully transferred, and reduce the transfer of water on the printing plate (see below for the role of water in printing) to the substrate.
Baidu encyclopedia-offset printing