With the application of non-absorbent printing materials such as gold and silver cardboard and laser transfer paper on cigarette packets, the application of UV offset printing in cigarette package printing has become more and more extensive. However, the control of the UV offset printing process is also difficult, and various quality problems are apt to occur in the production process.
Ink roller glaze
In the UV offset printing process, the glaze phenomenon occurs when the ink roller runs for a long time at a high speed, which causes poor ink squeezing, and it is difficult to ensure the ink balance.
In actual production, it was found that a batch of new ink rollers will not produce glaze in the first month of use, so the ink roller can be immersed for 4 to 5 hours per month with the ink roller reducing paste, which can fully restore the performance of the ink roller. , thereby reducing the generation of the ink roller glaze.
Ink roller expansion
It is well known that UV inks are highly corrosive, so that the ink roller that is surrounded by the UV offset ink at all times will also swell.
When the ink roller is inflated, appropriate treatment measures must be taken in time to avoid adverse consequences. The most important thing is to prevent the expansion of the ink roller from being too large, otherwise it will lead to bubbles and colloid breakage. In severe cases, it will even cause fatal damage to UV offset printing equipment.
Improper printing
The problem of unrealistic printing in the UV offset printing of cigarette packets can be generally divided into the following two types.
(1) UV curing color group printing is not true.
In this case, to properly arrange the color sequence, you should try to avoid turning on the UV lamp between the color groups. Usually, the white ink layer printed in the first pass is thickened and UV cured; when the second ink is printed, the ink layer is thinned and UV curing is not performed, and after being overprinted by other color groups, the level can be achieved. effect.
(2) Large-scale field printing is not true.
There are many influential factors for large-scale on-site printing. In order to avoid large-scale on-site printing, it is necessary to check whether the pressure of the ink roller is correct, and ensure that the ink roller has no glaze; the process parameters of the fountain solution are correct; the surface of the blanket is not Dirt, pinholes, etc. . In addition, the test proved that after a large area of ​​solid printing and then a group of air pressure, there will be an immediate effect on improving the flatness of large areas.
Ink reverse
In UV offset printing, ink back-drawing is a common fault, mainly because the UV offset ink is not completely cured after being irradiated by ultraviolet light, and the adhesion on the substrate is not strong. Under the action of the post-order color printing pressure, the ink is Pull up and stick to the blanket of the other color set.
When ink back-drawing occurs, it can usually be solved by reducing the amount of UV-curing color, increasing the amount of water in the ink set, and reducing the printing pressure of the ink set; if it still does not solve the problem, by UV curing
This problem can be improved by adding an appropriate amount of a tensile agent to the ink of the color set. In addition, the aging of the blanket is also an important cause of the ink back-drawing phenomenon.
Bad barcode printing
Bar code printing quality is a key indicator for cigarette pack UV offset printing. Moreover, since the gold and silver cardboard has strong reflectivity to light, it is easy to cause bar code detection to be unstable or even not up to standard. Generally, there are two main cases in which the UV offset printing barcode detection of the cigarette pack is not up to standard: defect degree and decodability. When the defect degree is not up to standard, it is necessary to check whether the white ink printing is flat and whether the covering of the paper is complete. When the decodability is not up to standard, the ink emulsification of the bar code printing color group and the bar code have a ghost phenomenon. .
UV offset inks of different hue have different UV transmittance. Generally, UV light is more likely to pass through yellow and magenta UV offset inks, and it is difficult to pass cyan and black UV offset inks, especially black UV offset inks. Therefore, in UV offset printing, if the thickness of the black UV offset printing ink is increased in order to improve the printing effect of the barcode, the ink may be poorly dried, the ink layer may be poorly attached, easily peeled off, or even stuck.
Therefore, pay special attention to the thickness of the black ink layer in UV offset printing to prevent the barcode from sticking.
Storage of UV offset inks
The UV offset ink must be stored in a dark place below 25 ° C. If stored at a high temperature, the UV offset ink will solidify and harden. In particular, UV offset gold and silver inks are more prone to solidification and gloss deterioration than ordinary UV offset inks, so it is best not to store them for a long time.
In short, the UV offset printing process is difficult to master. The technicians of the cigarette package printing enterprise must carefully observe and conscientiously summarize in the printing production. On the basis of mastering some necessary theoretical knowledge, the theory and experience will be combined to better solve the UV problem. Problems encountered in offset printing.
　　 The above content is selected from the 4th issue of 2011, Printing and Printing , Packaging and Decoration, and more journal content, please pay attention to the journal channel.
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