The graphic portion of the lithographic printing plate surface is almost in the same plane as the blank portion. It utilizes the principle of water and oil repelling, so that the graphic part is resistant to water and oil, and the blank part is resistant to oil and hydrophilic without ink, and the ink of the inked part is transferred to the surface of the printed matter under pressure to complete the printing process.
After the indirect printing method, the lithographic printing machine has developed rapidly and has many varieties, such as office micro-offset printing machines, large-scale, multi-color, high-speed newspapers and magazines offset printing rotary machines, for flat sheets or webs, Single-sided or double-sided lithographic printing presses. Among them, monochrome offset presses and web offset presses are representative. The lithographic printing press has widely adopted electronic computer control devices, and the technology is becoming more and more advanced. Plate-making equipment has also been developed to use electronic color separation machines, and pre-coated photosensitive plates are widely used.
