Eight problems that inks need to pay attention to during the printing process
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Question 1: How does the characteristics of the ink determine the amount of dampening solution used?
The fluidity of the ink can affect the amount of fountain solution used during printing. One of the reasons for using fountain solution in the printing process is to make it easier for water to form a water film on the non-printed portion, making it difficult for the ink to spread out to these portions. Assuming that the ink has a low fluidity, it spreads slowly on the printing plate, and the ink stays in the non-printed portion for a shorter period of time. In this case, we can use a lesser amount of dampening solution; on the contrary, assuming that the fluidity of the ink is large, we should appropriately increase the amount of dampening solution to prevent the ink from sticking to the non-printed portion.
Question 2: What happens after the ink is emulsified?
If the ink is emulsified, it will produce the following changes: (1) due to emulsification. The water is captured in the ink, occupying the space between its original parts, thus increasing the volume of the ink; (2) also because the water particles occupy the space of the ink, so that the pigment particles on the surface of the ink occupy The area ratio is reduced. Since the pigment reflects the color light in the air, and we see the color of the ink, the pigment particles are less, and the ink can reflect less light, which destroys the hue of the ink. Brightness and saturation; (3) Water penetrates into the ink and its viscosity decreases.
Question 3: What is the problem with printing with emulsified ink?
In fact, once the ink is emulsified, its hue. Brightness and saturation are destroyed by the infiltration of water molecules, so printing with these inks will definitely cause hue shift. Since the saturation of the ink is lowered, the amount of ink has to be increased during printing, which causes another problem of an increase in the density of the solid.
Question 4: What is the role of ink viscosity in printing?
Viscosity can also be called internal friction or cohesion. Physically, its direction of force is opposite to the direction of flow of liquid, and it is a resistance to flow. In the case of ink transfer, the viscosity is generated based on the fact that during the transfer process, the ink layer of the ink is pulled apart, and in order to counter this tension, another inward force occurs, which is the viscosity. Offset printing often requires the ink to have a certain viscosity so that the ink has a certain adhesion when spreading on a flat surface to make the dots clear; on the other hand, it can make the surface speed of the ink roller equal, helping the ink to be evenly transferred and maintained. A certain thickness of the ink layer.
Question 5: Is there any problem if the viscosity is too large or too small?
If the viscosity is too large, the ink transfer is uneven, the paper and paper powder are easily peeled off, and the paper is difficult to peel off from the rubber roller, and the printing quality is greatly affected; while the viscosity is large, the ink spreads slowly on the printing plate. After several rotations of the ink layer on the printing plate, the remaining ink layer is not enough to protect the layout, and as a result, the printing pressure and the dampening solution can not be withstood, so that the printing plate is easy to use. However, if the viscosity is too small, the ink will be too emulsified and dirty, resulting in poor printing quality.
Question 6: What is the effect of ink mobility?
The relationship between fluidity and viscosity is inversely proportional, the greater the fluidity, the lower the viscosity; the smaller the fluidity, the higher the viscosity. The ink has good fluidity and can guarantee the quality of printing to a certain extent, because under the same pressure, the ink can easily spread the ink film with uniform thickness on the surface of the ink roller, and maintain good transfer, so that it will not be printed. There are uneven prints.
Question 7: How many drying methods does the ink divide?
In fact, different inks use different methods to dry the ink according to its characteristics and different printing methods. Generally speaking, the following are not mentioned: (1) Ink oxidation. This polymeric coacervate dried form is the predominant dry form of offset printing; (2) osmotic drying. When the ink is printed on the paper, its binder will penetrate into the interior of the paper due to the capillary action of the paper fibers; (3) it will be dry. After the ink is printed on the paper, only part of it will penetrate into the paper, but most of it will be played out.
Question 8: Why do you want to use a drier in the ink?
When the drying ability of the ink material itself is insufficient to meet the time requirement of printing color, we need to add a drier to the ink to speed up the drying. The drier can be combined with the anti-oxidant in the ink to eliminate it and reduce the adverse effects of the anti-oxidant. In addition, the driers can directly absorb the oxygen in the air, making it easier for the ink to obtain the oxygen required for drying and accelerate the oxidative drying.