The PS plate meaning is pre-sensitized plate used in offset printing. In offset printing, the image to be printed comes from a coated
aluminium sheet, placed around the printing cylinder. The aluminium is treated so that its surface is hydrophilic (attracts water), while the developed PS plate coating is hydrophobic.The PS plate has two types: positive PS plate and negative PS plate. Of them, positive PS plate accounts for the large share, which is used in the majority of medium to large-scale printing tasks today. Its making technology is also matured.The PS plate is made of substrate and the PS plate coating, that is, photosensitive layer. The substrate is mostly aluminum base plate. The photosensitive layer is a layer formed by coating the photosensitive liquid on the base plate.Its main components are photosensitizer, film-forming agent and auxiliary agent. The photosensitizer commonly used in positive PS plates is soluble diazonaphthoquinone type photosensitive resin while that in negative PS plate is insoluble azide-based photosensitive resins.The positve PS plate has the advantages of light weight, stable performance, clear images, rich layers, and high printing quality. Its invention and application are a major change in the printing industry. At present, the PS plate has been matched with electronic typesetting, electronic color separation, and multicolor offset printing, which has become the mainstream platemaking system today.