The phenomenon of ink-off phenomenon in the
printing of paper self-adhesive materials is relatively low, and is mostly
found in film materials. This is mainly due to the unstable surface tension of
film materials. Under normal circumstances, the cause of film-type materials to
print off the ink due to film materials, low surface tension, poor UV curing,
ink additives, such as excessive use.
Low surface tension of film material
results in ink loss
In general, the surface tension of the
film-like material needs to be more than 38 dyne to ensure normal printing. To
make the ink adhere firmly, it is required to reach 42 dyne or more. If there
is ink off during the printing process, you can use the Dyne pen to test the
surface tension value of the material. If it is lower than the above criteria,
it is recommended to use online corona or base oil coating method to increase
the surface tension of the film material. In order to achieve better ink
adhesion.
If there is no condition to use the above
two methods to solve the problem, you can also use low surface energy ink to try
to solve. At present, many ink manufacturers provide inks that are specially
designed for low surface energy materials. Printing
companies can use tests to find a suitable ink for the label materials used
to solve this problem.
Poor UV curing leads to ink loss
Dropping ink also has a lot to do with the
curing effect of UV inks. If the power of the UV lamp is insufficient, or if
the printing speed is too fast, a “sham dry� phenomenon will occur, which can
easily cause ink fall off. The so-called "sham dry" means that the
surface layer of the ink has dried/solidified and the interior is not
completely dried/cured.
It should be particularly noted here that
the phenomenon of ink loss caused by this phenomenon occurs in the printing of
large-area solid patterns. This is because the solid pattern has a large amount
of ink and it is not easy to completely cure the interior of the ink layer. In
addition, sometimes the ink that is printed at the same time only has a certain
color, and the ink is more obvious. The most common one is that the black ink
has dropped heavily. This is because it is difficult for UV light to penetrate
the black ink layer. In most cases, the black ink is arranged to print in the
last color group. The total curing time is the shortest and it is not easy to
completely cure.
If you encounter such problems, you can
first check whether the UV lamp has exceeded the rated service life. If it
exceeds the need to replace the lamp. If the UV lamp is in normal service, then
the power of the UV lamp should be insufficient, the power of the UV lamp can
be appropriately increased, or the printing speed can be reduced.
However, for film adhesive materials, such
treatment may cause new problems - when the printing speed is too low or the UV
lamp power is too high, it is very likely that the film type adhesive material
will receive heat in a unit time. Larger and deformed.
When such problems are encountered, the
amount of ink supplied can be appropriately reduced, and the printing speed or
the power of the UV lamp can be appropriately increased to ensure that the ink
is completely cured. If the amount of ink supply is reduced to cause the
printing in the field to be imaginary, two printing methods can be used to
solve it if necessary.
Too much ink additive to cause ink loss
In northern China, when the weather is
relatively cold in winter, some printing companies may encounter
the problem of ink thickening, stickiness, and poor inking during the
production process. Therefore, many operators use the method of adding ink to
increase the fluidity of the ink. However, if too much ink is added to the
varnish, it can easily cause ink fallout.
In general, the proportion of varnish to be
added is 3% to 5%. If it exceeds this range, it needs to be carefully added.
