The process of printing process overview (3)

After careful inspection, rinse the plate with acid solution, and the residual photoresist must be completely removed when flushing.
Etching is then carried out after layout, that is, the solution is treated with a solution of phosphate, chromic acid, etc. to react with the metal of the blank portion of the printing plate to form a thin and hard layer of hydrophilic salt to improve the layout. The hydrophilic properties of the blank part and the printing force of the printing plate.

After being dried, evenly rub a layer of gum arabic to prevent the metal plate surface from coming into contact with the air to cause oxidation, and to ensure that printing plates do not cause small dirt, paste, and other ills.

3, drying Yin Ying protein version

Using a negative image as the original, a positive-printing plate based on a hardened protein film as a graphic text is dried and called a negative-image protein plate.

The graphic (net) part of the original negative is transparent. The photosensitive colloid coated on the plate undergoes a photochemical reaction upon irradiation with light and begins to harden, forming a graphic basis. And the blank part around it, because the colloid is not sensitive, can't react with photochemical reaction, dissolves in water after being washed and developed, leaving only the hardened colloidal graphic (that is, positive image) part on the plate.

Protein version of the photosensitive solution is generally composed of protein, ammonium dichromate and ammonia.

The pre-corrosion of the proteic plates (the stencil plate to be subjected to sensitization), the application of the photosensitive liquid, and the exposure (shim) were the same as those of the plano-gravure. After exposing to drying, it is necessary to rub a layer of uniform black ink with strong oleophilicity, and then develop, remove film, wipe glue, and so on. The operation requirements, except that the layout can not be used with hard brush, basically with the intaglio plate The operation is similar. Because the proteolytic film hardened film is slightly protruding from the layout, the surface only rely on a thin layer of lipid-sensitive ink layer to absorb printing ink, so its wear resistance and resistance to printing force are not high, generally only printable Thousands to 10,000 prints, it is rarely used except for some special varieties.

4, drying Yang multi-layer metal plate

Offset printing plates made of two or more different metals are called multi-layered metal plates.

Multi-layered metal plate is generally based on zinc (or iron) skin as the base plate, using electroplating process, the plated surface is plated with one or several kinds of metal plating to form the plate of the composite layer, and is made by printing on the plate. The metal coating with a strong sense of fat is the graphic basis of the printing plate, and the hydrophilic metal coating is a blank portion.

The common multi-layer metal plate has two layers and three layers of metal. According to the height of the graphic part and the blank part, there are two kinds of plano-convex type and concave type. It consists of a double-layered flat plate made of zinc and copper, a double-layered gravure plate made of copper and chromium, and a three-layer (multi-layer) plate and intaglio plate made of iron, copper, and chromium.

The drying method of the multi-layer metal plate is divided into two types: electroplating, then printing, and first printing.

(1) First plate after electroplating

After grinding the plate base, a thin layer of metallic copper is plated in the alkaline copper plating solution, then a slightly thicker copper layer is plated in the acidic copper plating solution, and finally a chromium layer is plated in the chromium plating solution. When the original positive version is used, after processing such as development, hardening, and etching, if the chromium layer of the graphic part is etched away, the copper plating recessed on the layout becomes the graphic basis of ink, and the blank part that is not inked is Chrome layer, which is a flat intaglio plate in a multi-layered metal plate.

(2) Plating before plating

First print on the surface of the plate, after processing, and then electroplating. If the copper layer is plated in the graphic part, a multi-layer metal plate is obtained.

The printing and etching methods of multi-layered metal plates are basically the same as those of sun-burning plates.