c. Chemical treatment
There are many methods of chemical treatment, mainly for aluminum version. Commonly used methods of sulfuric acid solution treatment. During the operation, the pre-treated aluminum plate is placed on the anode for 15 to 20 minutes. This method is also called anodic oxidation. The treated result forms a firm layer of aluminum oxide on the surface of the aluminum plate, which can make the surface of the plate have a high degree of adsorption capacity and greater mechanical strength, and ensure that the printing part and the blank part of the plate surface have a great stability .
2, drying Yangtuo gravure
Yangtuo intaglio printing is the use of positive sun-printing positive printing plates. Because offset printing is indirect printing, the positive image on the printing plate is like a positive image printed on the blanket. The negative image on the blanket is transferred to the substrate and becomes the positive image required for printing. .
The printing plate produced by the positive-gravure intaglio plate printing method has a graphic (ink) part that is 0.005-0.008 mm deeper than the plate surface, and is called an intaglio plate.
The positive gravure plate is generally zinc skin. The mechanism of printing is: the blank part of the plate is hardened by light, and the part of the picture and text is not affected by light and the surface layer of the adhesive layer is removed during development to make the corrosion concave. The main equipment for the printing process is a baking machine and a printing machine.
The process of positive gravure printing is as follows:
(a) Coating photosensitive liquid
After the plate-cleaned plate is placed on the rotary frame of the plate-making machine, the rotary frame of the plate-making machine is started, and the photosensitive liquid (mainly composed of dichromate, polyvinyl alcohol, etc.) is poured on the plate. In the center of the material, the photosensitive liquid is evenly applied to the entire surface of the plate, and after drying in a baking plate, it becomes a ready-to-use plate with a photosensitive layer.
(b) Exposure
Exposure is done on the plate making machine. The printing plate is covered on the printing plate that has been coated with a photosensitive liquid, and the two are sealed by vacuum pumping, and then the light source is turned on for exposure.
After exposure, the photosensitive film in the blank portion of the printing plate is hardened by a photochemical reaction, and the hardened adhesive layer has a corresponding anti-corrosion force so as not to be corroded in the subsequent etching process. On the other hand, the image on the printing plate is easily removed and corroded because the colloid is not photosensitized.
(c) Development
It removes the photo-resist film that is not photo-hardened on the printing plate surface, so that the graphic part completely exposes the metal surface. The developer consists of calcium chloride, zinc chloride, and lactic acid (weak acid).
(d) Corrosion
That is to say, the exposed graphic points of the metal plate are corroded with an etching solution (generally formulated with acid and salt), so that the zinc surface of the graphic part is dissolved to form a firm foundation for the printing plate graphic.
(e) Coating of a fat sensor
Also called base paint (rubber). In order to make the layout graphic have a lipophilic property, it is necessary to coat a layer of oleophilic material on the surface of the eroded plate to increase the water resistance of the graphic part during printing and improve the resistance to printing (general gravure The resistance to India is about 20,000-5,000 prints.
Before adding the base paint, it is necessary to pay attention to the residual of the two solutions left on the plate during development and corrosion, thoroughly rinse it off, and use the glue to glue white spots, white lines (prints, etc.) or degumming parts around the picture. Substantially fill in, otherwise it will hinder the painting of ink and the formation of surrounding dirt and so on, resulting in waste version, can not print. After applying the base paint, the developing ink is applied.
(f) In addition to the film
Remove the hardened film on the plate (that is, the blank non-inked portion) so that the bare metal surface is exposed.