Printing ink drying abnormal seven reasons! Complete solution attached
Time:2023-02-03
Views:1956
1. The ink layer is too thick
In the process of large area field printing, because the amount of ink is too large and the ink layer is too thick, the ink layer on the surface of the printing product will appear in the drying process of the surface layer is completely dry and the bottom layer is not completely dry, that is, the phenomenon of false drying. In addition to the ink layer is too thick, paper speed, UV light exposure time is insufficient will also cause UV ink false dry phenomenon. Once the phenomenon of false drying ink, it is easy to cause the ink layer on the surface of the printing product to fall off during the post-processing process. This is because dry ink bottom and substrate surface combination fastness is poor, so that the ink layer under the action of friction and scraping off.
Solution:
For the use of spot color UV ink to print live parts, when matching ink, try to match the color of spot color UV ink with some dark, so that in the printing process can be through deep ink thin printing way to dry the bottom of the ink, increase its combination with the substrate surface fastness. At the same time, it is necessary to ensure the appropriate paper speed and adequate UV light exposure time, if the paper speed is faster, it is necessary to improve the power of UV lamp, in order to ensure the ink drying effect.
Solution:
2. The UV lamp power is insufficient
The lack of UV lamp power is also one of the reasons for the poor drying of UV ink, which is related to the daily production operation of enterprises, mainly manifested in the following aspects:
(1). All UV lamps have an effective service life (generally 800 ~ 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, the timer of the UV lamp is not returned to zero, resulting in the use time of the UV lamp has exceeded the service life.
(3). Do not pay attention to the surface of the UV lamp cleaning, long time after the use of UV lamp reflective cover is too dirty, resulting in UV lamp reflection energy loss (reflected energy can account for about 50% of the UV lamp power).
(4). UV lamp power configuration is not reasonable, such as the domestic full rotation self-adhesive label press each group of UV lamp power reasonable configuration is basically more than 3000 watts, foreign equipment due to its printing speed, each group of UV lamp power is basically more than 7000 watts, and some full rotation self-adhesive label printing press each group of UV lamp power is only 2000 watts.
Solution:
First of all, we must establish a complete and effective UV lamp use management system, to ensure that the UV lamp in the effective service life of the work, timely replacement has exceeded the service life of the UV lamp, and the replacement of the UV lamp unit pay attention to the use of the UV lamp timer return to zero; Secondly, regular cleaning UV lamp reflective cover, reduce the loss of reflected energy; Furthermore, the power of UV lamp is reasonably configured according to the structure characteristics of the equipment.
First of all, we must establish a complete and effective UV lamp use management system, to ensure that the UV lamp in the effective service life of the work, timely replacement has exceeded the service life of the UV lamp, and the replacement of the UV lamp unit pay attention to the use of the UV lamp timer return to zero; Secondly, regular cleaning UV lamp reflective cover, reduce the loss of reflected energy; Furthermore, the power of UV lamp is reasonably configured according to the structure characteristics of the equipment.
3. Ink over shelf life or excessive additives
In general, if the ink shelf life is exceeded, the printing ink may be poor drying due to the failure of the photoinitiator in the ink after printing. In addition, in the printing production, in order to improve the performance of ink, it is often necessary to add additives such as adjusting ink oil and removing adhesive in ink. If the proportion of additives is too high, it may lead to too thin ink and cause poor drying. UV ink itself has thixotropy, that is, under the action of the roller shear force will become more and more thin. Moreover, after the printing equipment runs for a period of time, the ink rollers will friction and heat, and then reduce the ink viscosity.
Solution:
First of all, to ensure that the ink in its shelf life; Secondly, pay attention to the amount of ink auxiliary agent and desiccant, UV ink additive ratio is recommended not more than 3% in summer, not more than 8% in winter.
4. Different colors of UV ink drying degree
The test shows that different colors of UV ink on the spectrum of absorption is different, so in the same power of UV lamp, different colors of UV ink drying degree is different. Such as white UV ink can directly reflect the light, black UV ink will form diffuse reflection of light, magenta UV ink on light absorption effect is better.
According to experience, four primary color UV ink drying difficulty from difficult to easy is black, cyan, yellow and magenta, and gold and silver UV ink than four primary color UV ink more difficult to dry, white UV ink due to the reflection of light is also difficult to dry.
Solution:
According to the drying characteristics of different colors of UV ink, reasonable arrangement of printing color sequence, printing ink is difficult to dry, and then printing ink is easy to dry, which can solve the problem of poor ink drying to a certain extent.
UV ink drying mainly depends on the chemical reaction between the photoinitiator and resin to achieve, among which, the molecular structure of the resin is larger, and the molecular structure of the photoinitiator is smaller. If the density of cots is too low, there will be many holes on the surface, because the diameter of these holes is larger than the diameter of the photoinitiator, so some of the UV ink photoinitiator will be absorbed by cots, resulting in UV ink in the drying process, the chemical reaction of the resin and photoinitiator is insufficient, resulting in poor ink drying, but also accompanied by ink on the cots surface drying phenomenon.
Solution:
5. The density of cots is too low
In actual production, new equipment is more prone to ink drying failure. After careful inspection, it was found that because the density of the roller is too low to absorb UV ink in the photoinitiator, resulting in poor ink drying phenomenon.
UV ink drying mainly depends on the chemical reaction between the photoinitiator and resin to achieve, among which, the molecular structure of the resin is larger, and the molecular structure of the photoinitiator is smaller. If the density of cots is too low, there will be many holes on the surface, because the diameter of these holes is larger than the diameter of the photoinitiator, so some of the UV ink photoinitiator will be absorbed by cots, resulting in UV ink in the drying process, the chemical reaction of the resin and photoinitiator is insufficient, resulting in poor ink drying, but also accompanied by ink on the cots surface drying phenomenon.
Solution:
The easiest way is to replace the cots; If it is too late to replace the cots, you can also remove the cots and soak them in UV ink oil for 12 to 24 hours. At this time, the cots will gradually absorb UV ink oil, and when they reach saturation, it is difficult to absorb UV ink in the photoinitiator.
6. Other reasons
Glossy resin ink used for lithography. Under normal conditions, the imprint transferred to paper by blanket can be dried in a few hours. However, in daily production, slow drying of imprinting is often encountered, so the following reasons need to be investigated:
(1). Too much water supply?
(2). Embellish version of the liquid pH value is too small?
(3). Is the temperature in the printing workshop too low or the humidity too high?
(4). Paper absorption is poor?
Solution:
Occurrence of the above problems, to strictly control the size of the layout of water, master the pH value of the water version. Encounter imprinting is not dry, should be timely to air printing, ventilation, so that air into the paper, to speed up the time of conjunctiva.
Solution:
7. Ink drying too fast
When printing in monochromatic offset press, it often produces the former color imprinting drying too fast, forming "crystallization", so that the latter color overprinting, the main reason is that the drying oil is added too much or the semi-finished product stacking time is too long, and this phenomenon often occurs when printing yellow plate or light background color full plate.
Solution:
This problem, if the number of overprint not on the product is small, can be dipped in a clean soft cloth magnesium carbonate powder, gently wipe on the surface of each printed matter, so that its surface coarsening; With infrared radiation, the ink layer is heated and expanded to coarser; If the number is large, you can carry out humidification treatment, so that the ink layer hygroscopic expansion, surface coarsening.
After the surface of the ink layer thickens, the latter color ink is easy to adhere to, in order to prevent the phenomenon of printing, can be added in yellow ink in advance of the appropriate amount of dry waxy auxiliary agent, so that the ink layer will not crystallize, in the printing of light background color full version, can be mixed with vili oil and diluent, also can prevent the latter color printing.
After the surface of the ink layer thickens, the latter color ink is easy to adhere to, in order to prevent the phenomenon of printing, can be added in yellow ink in advance of the appropriate amount of dry waxy auxiliary agent, so that the ink layer will not crystallize, in the printing of light background color full version, can be mixed with vili oil and diluent, also can prevent the latter color printing.
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