Part D Glazing process and analysis of quality factors
The glazing process is a technique and method for applying a layer of uncoated transparent coating on the surface of the printed product, after leveling, drying, calendering, and forming a thin and uniform transparent bright layer on the surface of the printed matter.
UV glazing process knowledge and troubleshooting
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Sixth, the effect of UV glazing on the color of printed matter
The use of UV glazing prints sometimes causes yellowing. There are two main reasons: one is that the UV varnish itself is yellow; the other is that during glazing, the varnish is only cured on the surface of the print. The interior is not completely cured.
The yellowing of the varnish is related to the fact that the oligomers and reactive diluents used are yellow in color, so colorless oligomers and reactive diluents should be used to formulate the varnish. In addition, the effect of photoinitiators is also very large. Some photoinitiators will make the system yellow after curing, such as benzoin dimethyl ether, so avoid using such photoinitiators to prepare varnish.
During the glazing process, when the varnish is not completely cured inside, the internal glazing thinner will gradually be absorbed by the ink and paper, and at the same time will affect the binder in the ink, resulting in loss of grease. The pigment is not adequately protected and the pigment particles are free. At this time, the smoothness of the surface of the paper coating and the ink layer is lowered. The rough surface will diffusely reflect the light, which will add some white components to the color, which will increase the brightness and decrease the saturation, giving the overall yellowing and lightening of the color. Therefore, the curing speed of the UV coating should be increased or an efficient UV curing source should be selected. In addition, the use of water-based UV coating can avoid the chemical action of the thinner ink layer and the paper coating, and avoid the yellowing of the printed matter.