A summary of printing ink drying problems and solutions

In printing, the problem of poor ink drying or ink drying too fast often often occurs. If you want to solve this problem, you must first find out why. Small compilation of 7 factors, to help you check one by one

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01, the ink layer is too thick
in a large area of the field printing process, due to the ink is too large, the ink layer is too thick, the ink layer on the surface of the print will appear in the drying process of the surface completely dry and the bottom drying incomplete phenomenon, that is, the phenomenon of fake drying. In addition to the ink layer is too thick, walking paper too fast, UV light exposure time is not enough will also cause UV ink fake dry phenomenon. Once the ink false dry phenomenon, in the post-process processing process can easily lead to the printing surface of the ink layer off. This is because the drying of incomplete ink bottom and the seal surface of the binding fastness is poor, so that the ink layer under the role of friction is scraped and fell off.
Solution
For the use of spot color UV ink printing field live parts, with ink as far as possible will be spot color UV ink color with some depth, so that in the printing process can be through the way of dark ink thin printing to make the ink bottom completely dry, increase its binding with the seal surface fastness. At the same time, it is necessary to ensure the appropriate paper walking speed and sufficient UV light exposure time, if the paper speed is fast, the power of UV lamps must be increased to ensure the drying effect of ink.
02, UV lamp power is
UV lamp power shortage is also one of the causes of UV ink drying failure, which is related to the daily production operation of enterprises, mainly in the following aspects:
1, all UV lamps have an effective service life (generally 800 to 1000 hours), when the use of UV lamps exceeds its service life, although UV lamps can continue to work, but its power has been greatly reduced.
2, after replacing the UV lamp did not zero the use of UV lamp timer, resulting in UV lamp use time has exceeded the service life but completely unknown.
3, do not pay attention to the surface cleaning of UV lamps, after long-term use of UV lamp reflectors are too dirty, resulting in the UV lamp reflective energy loss (reflective energy can account for about 50% of UV lamp power).
4, UV lamp power configuration is unreasonable, such as the domestic all-wheeled sticker printing press each set of UV lamp power reasonable configuration is basically more than 3000 watts, foreign equipment because of its printing speed is faster, the power of each set of UV lamps is basically more than 7000 watts, and some full-wheel sticker printing machine each set of UV lamp power is only 2000 watts.
The solution
First, a complete and effective UV lamp use management system must be established to ensure that UV lamps work within an effective service life, timely replacement of UV lamps that have exceeded service life, and the unit that has replaced UV lamps pay attention to zeroing the use of UV lamps;
03, ink ultra-shelf life or excessive additives
in general, if the ink shelf life is exceeded, then after printing may be due to the failure of light triggers in the ink resulting in poor ink drying. In addition, in printing production, in order to improve the performance of inks, it is often necessary to add inks, adhesives and other additives. If the proportion of additives is too high, it may cause the ink to be too thin and cause poor drying. UV ink itself has tentacles, i.e. it becomes more and more thin under the effect of the shear force of the ink roller. Moreover, after the printing equipment has been running for some time, the ink rollers will rub and heat, which will reduce the stickyness of the ink.
A solution
First, to ensure that the ink is used during its shelf life, and secondly, to pay attention to the amount of ink aids and desiccants, it is recommended that the proportion of UV ink additives does not exceed 3% in summer and no more than 8% in winter.
04, different colors of UV ink drying degree is different
the test shows that different colors of UV ink on the spectrum absorption is different, so under the same power UV lamp, different colors of UV ink drying degree is different. Such as white UV ink can directly reflect light, black UV ink will form a diffuse reflection of light, the melano UV ink on the absorption of light effect is better.
According to experience, the difficulty of drying four primary color UV inks from difficult to easy in turn is black, cyan, yellow and magenta, while gold and silver UV inks are more difficult to dry than four primary color UV inks, white UV inks because of the reflection of light is also difficult to dry.
Solution
According to the drying characteristics of UV inks of different colors, reasonable arrangement of printing color sequence, first printing more difficult to dry ink, and then printing easier to dry ink, so that to a certain extent can solve the problem of poor ink drying.
05, roll density is too low
in the actual production, the new equipment is more prone to ink drying failure. After careful examination, it was found that it was because the low density of the roller absorbed the light trigger in UV ink, resulting in poor ink drying.
drying of UV inks is mainly achieved by chemical reactions between light triggers and resins, wherein the molecular structure of resins is larger and the molecular structure of light triggers is smaller. If the density of the roll is too low, its surface will appear many small holes, because the diameter of these small holes is greater than the diameter of the light trigger, so some of the light trigger in the UV ink will be absorbed by the roll, resulting in UV ink in the drying process, its resin and light trigger chemical reaction is not sufficient, resulting in poor ink drying, but also accompanied by ink drying on the surface of the roller.
Resolvation
The simplest way is to replace the roller, if it is too late to replace the roller, you can also remove the roll, put in UV ink soaked for 12 to 24 hours, at this time the roller will gradually absorb UV ink, when reached saturation state, it is difficult to absorb the light trigger in the UV ink.
06, other reasons
lit resin ink for litchography printing, under normal circumstances, by rubber cloth transfer to the paper imprint can generally be dried for several hours. But in daily production, often encounter the printing drying is too slow, then also need to check the following reasons:
1, water supply is too large?
2, moisturizing liquid pH is too small?
3, printing workshop temperature is too low or humidity is too high?
4, poor paper absorption?
solution
the above problems occur, to strictly control the size of the layout moisture, master the pH of the moisturizing liquid. In case the imprint is not dry, the print should be aired in time, ventilation, so that air into the paper, in order to speed up the conjunctivation time.
07, ink drying too fast
monochrome offset printing machine, often will produce the previous color imprinting dry too fast, the formation of "crystallization", so that the latest color overprinting, the main reason is that the dry oil over-filled or semi-finished product stacking time is too long, this phenomenon often occurs in the yellow plate or light background full plate.
National solution
this problem occurs, if the number of products not printed is small, you can use a clean soft cloth magnesium carbonate powder, gently rub on the surface of each printed material, make its surface coarse;
After the surface of the ink layer becomes thicker, the latest color ink is easy to attach, in order to prevent the production of imprint phenomenon, you can add a moderate amount of dry wax auxiliary agent in yellow ink, so that the ink layer will not crystallize, in the printing light base color full plate, you can mix and blend Willy oil and lightener, but also to prevent the latest color printing can not be printed.
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