Analysis of the coating and glazing process of the

2022-07-30
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Analysis on the coating and polishing process of printed matter

today's printed matter is not only colorful, but also beautifully decorated. Furthermore, the LED lighting effect can be significantly improved. In addition to the fine literature links: the hierarchy of the bioinspired reversible snapping hydraulic assembly and the realistic color image printing, some additional surface treatments are also important measures to improve the quality of printed matter. Printing metallic ink, embossing, embossing, hot stamping electrochemical aluminum foil, surface compound transparent plastic film and coating varnish are some additional surface treatment methods that can be selected. Of course, these additional surface treatments must be as economical as possible. Now, many printing companies have realized that the printing table is very low. Manroland, Heidelberg and other offset printing machines can be coated and polished online

I. coating and polishing process

1 Function of coating varnish

① decorative function: coating a layer of varnish on the surface of the print can give the print a matte, shiny or high gloss surface

② protection: the varnish film coated on the surface of the ink layer of the printed matter can protect the ink layer, especially during the transportation of the finished printing products. Any printed matter can be coated with varnish. The only question is: is it appropriate and economical to apply varnish in a certain way under certain conditions

2. Main types of glazing oils

the three most commonly used glazing oils in on-line coating are oil-based clear. At the same time, it also leads to the concept of "sharing economy", UV curing varnish and water-based varnish. Generally speaking, the cost of coating oil-based varnish is equivalent to printing another color of ink. The cost of coating water-based varnish with the same dry film thickness is basically the same as that of coating oil-based varnish, but the water-based varnish coating usually needs to be thicker, so the cost of varnish used is also higher. In terms of coating effect, coating UV curing varnish is the best online coating and glazing process, but it is also the most expensive online coating and glazing method. In any case, online coating varnish is always much more economical than additional post-treatment methods such as composite BOPP film, offline coating varnish or calendering after printing. Therefore, online coating varnish (especially water-based varnish) has been widely used

(1) oil based varnish

the composition of oil-based varnish is basically the same as that of offset printing ink, but it does not contain pigments. It contains about 75% of solid components and is dried by chemical methods

the advantages of coating oil-based varnish are:

① the treatment method is the same as that of general ink printing

② easy for local painting

③ the coating has good moisture resistance

the disadvantages of coating oil-based varnish are:

① the oil-based varnish dries slowly

② the coating is thin

③ the coating tends to turn yellow

④ after coating, it is necessary to spray powder to prevent printing adhesion

⑤ it is possible to use a frame paper receiving device

(2) water based varnish

water based varnish contains about 40% of solid components, and the remaining 60% is water, which is dried by physical methods

the advantages of coating Waterborne Varnish are:

① the coating has excellent gloss

② the coating has excellent wear resistance

③ the water-based varnish dries rapidly after coating

④ there is no need to spray powder or only a small amount of powder after coating water-based varnish

⑤ good stacking stability of prints

⑥ the coating will not turn yellow

⑦ the water-based varnish has no bad smell, and its application field is rarely limited

the disadvantages of coating water-based varnish are:

① when using lightweight paper, the printing sheet may curl due to water absorption

② it is difficult to carry out local coating (coating with metering roller)

(3) UV curing varnish

UV curing varnish contains more than 99% of solid components. It is "dried" by radiation curing. In fact, the whole coating is polymerized into a solid film under UV irradiation. The curing effect depends on the UV wavelength and radiation power emitted by the UV lamp

the advantages of applying UV curing varnish are:

① the polishing coating can produce extremely high gloss

② the coating is firm and durable

③ as long as the UV lamp can meet the use requirements, the UV curing varnish coated on the print can be dried immediately

④ there is no need to spray powder after coating, and there will be no print adhesion

⑤ the coating has high wear resistance

the disadvantages of coating UV curing varnish are:

① the machinery and equipment are expensive

② UV curing varnish has high cost and energy consumption

③ not completely odorless

④ it is difficult to apply UV curing varnish directly on-line for printed matter printed with ordinary offset ink. Two coating and polishing units must be occupied, the first one is the primer and the second one is the glazing

(to be continued)

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