Stencil Process Operation Process (4)

However, the use of phosphoric acid during corrosion also has a long corrosion time.

The main advantage of the multi-layer metal gravure is that the copper layer (ie, the inking layer) is recessed in the chromium metal plating layer, and the copper has a good ink-receptive and ink-transmitting performance, thereby greatly improving the printing efficiency. In addition, the chromium layer (ie, the blank hydrophilic portion) has a high degree of erosion resistance. Hydrophilic wettability is also good, and it has high hardness and high mechanical abrasion resistance. In this way, the ink printed on paper can be made thick and bright, and its resistance to printing can reach 50 to 1 million prints or more.

Therefore, the multi-layer metal gravure plate is especially suitable for printing machines with high printing speed, and is suitable for printing a large number of print products with high quality requirements. However, its production is complicated and requires a complete set of electroplating equipment, and the use of copper, chromium, nickel and other metals in large quantities is relatively costly. Therefore, there is a certain limit to its development.

5, drying pre-coated version

Pre-Painted Photographic Abbreviation, PS Edition, refers to a plate that has been coated with a photosensitive layer in advance. Like photographic film, it can be stored in a dark room for a long period of time. When it is needed, it can be removed, and it can be printed, developed, and slightly trimmed, and the plate can be printed. production. It has many advantages:

(1) Easy to operate. Only exposure, development, gluing, etc. can be printed on the machine. And can also use automatic development machine development, high production efficiency.

(2) High resistance to printing force. In general, the resistance of the positive gravure is about 30,000 impressions, and the pre-finish version is generally up to 100,000 impressions. If it is baked, it can reach 20 to 500,000 impressions.

(3) stable performance. The pre-coated sensitized plate is not susceptible to climate change, has no dark reaction, is relatively stable in quality, and has a long shelf life, so it can be produced in batches.

(4) Good quality. Because it uses a photosensitive resin, has a very good resolution, made of printing plate dot smooth, rich layers, exposure latitude, especially suitable for printing fine prints.

The commonly used pre-coated version mainly has the following two types:

(1) Positive-coated version (indicated by P).

The positive-printing positive-working plate is printed on the positive chart. The photosensitive part of the printing plate (blank space), using the principle of disazotization after diazo compounds are seen, then developed and dissolved by dilute alkali solution, exposing the aluminum plate base to form the hydrophilic part of the printing plate, and the photosensitive part is not sensitive to light. The layer does not change, is not dissolved by the dilute alkaline solution, and forms the oleophilic (graphic) portion of the printing plate directly to affinity with the ink.

P-type photosensitizers are often mixed with alkali-soluble phenolic resins or other high-molecular compounds, and the graphic parts formed are relatively strong and do not need to be weighed on. Therefore, they are also called inner type.

(2) Negative pattern pre-coating (indicated by N).

The negative plate is used to make the printing plate, and the photosensitive part of the plate (photos) is decomposed by diazo compounds to become water-insoluble. After exposure, it is developed with water to remove the photosensitive agent of the unexposed part and become The hydrophilic part; and the photosensitive part is insoluble in water and becomes the basis of the picture.

Most of the molecular weight of N-type sensitizers is not high, so it is necessary to additionally apply a lipophilic base paint (upper gram) to the graphic part, so it is also called appearance.

Preprinted plates are generally made of aluminum plates.

The equipment for drying PS plates mainly includes printing plates and developing machines.