Study on the coating glazing technology for printing surface

Both coating and special rubber blankets can be used for coating the varnish, and the photosensitive resin Plate can be selected for the fine spot coating.

1. Coating with Varnish

Many domestic printers still use ordinary blankets for the entire coating process. If only the material cost is considered, this method is certainly the most economical. However, this must be done frequently to clean the blanket, because the ink tends to accumulate on the blanket in a short period of time, resulting in multiple shutdowns.

From the point of view of the transfer of varnish, the use of special blankets for coating has better performance and is less prone to ink build-up.

Both of these blankets can be cut in different ways to the size of the sheet. One of the cutting methods is to first cut a standard format paper with a blanket lining size, and then cut the blanket with a standard format paper as a reference. Another method of cutting is to cut off the excess part of the blanket. This is necessary because it prevents the glazing oil from being transferred to the impression cylinder during the coating process, causing the press to become dirty.

With the blanket cutting method described above, it is also possible to cut out a simple localized polishing blanket (the regularized part is a regular geometry).

When calculating the costs of glazing and blankets, it is also necessary to take into account the downtime and accidental cuts caused by manual cutting of the blanket.

Gloss coating with a blanket, its service life is much shorter than the photosensitive resin plate.

2. Polishing version - photosensitive resin version

If you need to polish some of the subtle parts of the printed sheet, such as some independent patterns or fine graphics, it is recommended to use a photosensitive resin plate to make a partial glossy version.

When using a gold or silver lacquer, it is also necessary to make a glossy version with a photosensitive resin plate.

Photosensitive resin partial glazing can generally be produced using a platform exposure apparatus. When taking into account the deformation factor when the glazing plate is bent, or when making a local glazing plate with a high requirement for accuracy, a special curved surface exposure device can be used for the production. The roller used in this special exposure apparatus has the same roller diameter as the printer.

When the accuracy of localized light registration is very strict, it is recommended to use aluminum-based photosensitive resin to ensure its dimensional stability.

The photosensitive resin plate used to make the local glossy version should have the following characteristics:

(1) The thickness of the plate is uniform;

(2) It can evenly transfer coating oil;

(3) The glazing graphics network is clear, the dot quality is stable, and there are no burrs on the side of the dot.

(4) It can ensure long-term stable operation;

(5) Less tendency to produce ink build-up.

Professional plate-making service companies are constantly increasing the use of CAD drawing devices to produce local glazing versions and the use of special curved surface exposure devices to produce local glazing versions. This kind of service project can particularly meet the needs of small and medium-sized printing companies for local glazing. (to be continued)