Foil paper products are used in packaging and decorating, which can make the packaged products more noble and splendid and improve the quality of the products. Therefore, the printed products printed with aluminum foil are compared with other printed materials with gold and silver processing technology, and the visual effect becomes more beautiful. The history of printing on aluminum foil paper is not long, and it is not very common at present, because aluminum foil paper has obviously different printability compared with other ordinary paper.
On the surface of the paper is printed on aluminum foil, we call it aluminum foil printing. There are two kinds of aluminum foil, gold foil and silver foil.
First, the printability of aluminum foil
Aluminum foil is non-absorbent paper. It is made by sticking aluminum foil on the surface of the cardboard. Since the non-absorbing nature of the surface of the foil directly affects the dry form of the ink layer.
We know that the penetration, solidification and polymerization of ink on plain paper, and oxidized conjunctiva are the main forms of ink drying. However, after the ink layer is printed on the paper, the dryness of the ink layer permeating the paper is quick and obvious in terms of the drying time. After the dry vegetable oil in the ink layer is contacted with oxygen, The subsequent oxidation of the film-forming layer and drying of the polymerized form is a very slow process. It will take some time to complete the whole process of its chemical and physical reactions. It can be seen that the combined effects of the two have formed the final result of the complete drying of printed products. When printed on aluminum foil, the situation is different, mainly because of the significant changes in its dry form. Since aluminum foil cannot or cannot substantially absorb the solvent in the ink, solvents such as dry vegetable oil and high-boiling point kerosene in the ink binder cannot penetrate into the interior of the paper and have to stay in the ink layer on the surface of the paper, so that the ink layer cannot be compared. As soon as it thickens and sticks, the ink layer loses its initial drying time. This means that the ink layer slowly polymerizes and the drying process of the oxidized conjunctiva becomes the main dry form of the aluminum foil ink layer. The solvent retained in the ink layer not only fails to quickly thicken the ink, but also in turn hinders the polymerization and oxidation of the ink layer, thereby making the drying rate slower. This phenomenon is often referred to as "not work." The nature of the aluminum foil itself determines the nature of the ink layer that does not dry quickly.
Another feature of aluminum foil is its high smoothness and poor adhesion. The printed material is very prone to stickiness after printing. Once this happens, the smooth and smooth ink layer will become fragmented or incomplete at the moment of printing, seriously affecting the visual effect of the product and even becoming a waste product.
The previously mentioned phenomenon of “does not quit†has induced the sticky phenomenon to become more prominent. Therefore, it can be said that the phenomenon of “doing no work†and “viscous dirty†are the twin brothers that affect each other and relate to each other, and become an important part of our attention and concern during the printing process of aluminum foil. It is necessary to adopt corresponding technological measures and requirements around these two issues.
Second, aluminum foil printing process
1. Aluminum foil printing process
The temperature of the printing environment plays a major role in the drying speed of the ink layer. When the temperature is lower, the drying speed of the printing materials is relatively slow, and the drying time is also increased accordingly.
In order to make the ink layer "do not dry" phenomenon will not be excessively severe, aluminum foil printing has certain requirements on the temperature. The ideal ambient temperature is above 25°C. Printing under such a temperature condition is advantageous to the drying of the ink layer, and the operation is more convenient. If the natural temperature (such as winter) does not meet certain requirements, the necessary heating facilities can be used. Because a higher ambient temperature can accelerate the speed of movement of the material molecules in the ink layer, it is advantageous to contact the vegetable oil and oxygen in the ink layer to produce a film layer, thereby increasing the speed of oxidation and polymerization and accelerating the drying of the ink layer. On the other hand, since the drying process of the ink layer is also an exothermic reaction process, the heat generated by the reaction further promotes the drying of the ink layer, thereby forming a benign cycle of the ink layer accelerating the conjunctiva. This is a great advantage for the drying of the blots and the complete transfer of the ink layer. It is best to print aluminum foil in a relatively dry environment. This will dry the printed material and prevent stickiness. We know that the drying of the ink layer must first evaporate its internal moisture, because moisture has the effect of hindering and inhibiting the drying of the ink layer.
Only after the water evaporates, the ink layer can be effectively oxidized and polymerized until it is finally dried and filmed. The speed of water evaporation in the ink layer has a direct relationship with the ambient humidity. When the humidity of the environment increases, that is, when the air is relatively humid, the moisture evaporation rate in the ink layer becomes slow, and the ink drying time increases.
On the contrary, when the humidity of the environment is reduced, ie when the air is relatively dry, the evaporation rate of water in the ink layer is correspondingly accelerated, and the drying time of the ink layer is correspondingly shortened.
On the other hand, when printing in a relatively humid environment, the oxygen activity in the air becomes less active and will directly affect the inhalation of oxygen by the ink layer, resulting in a slow drying process in the oxidative conjunctiva process. This is the effect of ambient temperature on the ink. Another reason for layer drying.
2. Take dirty measures
1 Increase the amount of dry oil added. When we print aluminum foil, the amount of dry oil should be appropriately increased in the ink, and its dripping effect on the ink is used to accelerate the oxidation and polymerization reaction of the ink layer, promote the ink layer to dry and solidify, and prevent the occurrence of sticky faults.
2 Master the piled amount of printed products. Because the aluminum foil paper prints are extremely sticky, the wet ink layer of the prints is more prone to such failures due to the gravity of the paper. Therefore, it is a very important part to master the stacking amount of the prints. Generally speaking, it should be Take measures to clamp the air in order to minimize the pressure on the ink layer formed by each knife due to gravity, and to prevent the paper surface and the back surface from being dirty. In normal circumstances, the stacking amount of each piece of paper is generally about 30 sheets.
The 3 panels maintain a minimum amount of moisture. Absorption of water by paper is the main way of water consumption on offset printing plates. Aluminum foil does not absorb ink and it does not absorb moisture.
Therefore, when printing aluminum foil, the amount of water consumed in the bucket is very small. For this reason, we can keep the minimum amount of water in the layout on the premise that the layout is not dirty, so as not to dilute the ink and the ink stickiness of the printed ink layer. At the same time, less water on the layout is also very beneficial for maintaining the bright color of the ink and improving product quality.
3. Printing ink should not be too thick
Compared with plain paper, the aluminum foil surface is much smoother, and its ink adsorption performance is also significantly inferior to ordinary paper. Therefore, when the ink on the printing plate is finally transferred to the aluminum foil through the blanket, if the used ink is thick, ink “overprinting†or “under printing†on the aluminum foil paper often occurs. It is the reason why the ink and blanket have a much higher adsorption force than the ink and aluminum foil. In this case, we can use the varnish to dilute the ink properly. By increasing the fluidity of the ink, we can reduce the adsorption force between the blanket and the ink so that it can be transferred to the aluminum foil smoothly under the pressure. on.
4. Print processing
As mentioned above, the unique smoothness and non-absorbing properties of aluminum foil make it lose the initial fixing and drying process of the ink layer. The ink layer can only adhere to the surface of the paper and look forward to oxidizing the conjunctiva slowly. This determines the ink layer. After just printing on the paper, it will not stick and dry for a considerable period of time. This nature had to make it impossible for people to move or shake the newly printed paper during this period of time, otherwise it could easily cause the paper sheet and the back side to become dirty. Furthermore, even if the ink layer has not completely oxidized the conjunctiva for a certain period of time after the ink layer has been fixed on the paper, mutual fluttering between the paper sheets is avoided. If the paper is flicked during this time, the ink layer will not be smeared, but there will be spurious scratches. This will also damage the ink layer. Only when the ink layer is substantially fixed and the conjunctiva is dried can such conditions be eliminated.
Third, the use of special ink
The use of common inks for printing on aluminum foil paper is certainly not a bad idea, but the use of special inks (such as "POP special lithographic inks" that are already in use in the market) is more appropriate. Because the special ink compared with ordinary ink, it is more suitable for the adaptability of aluminum foil printing. Special inks have the following characteristics:
1. Better transfer performance, ink transfer performance, for the aluminum foil paper, the final reflection of whether the ink layer between the blanket and the aluminum foil to achieve the middle of the sensitive issue. If this can be achieved basically, it will provide a good guarantee for product quality, whether it is for printing on-site products or outlet products. In this respect, special inks are superior to ordinary inks.
2. Ink coloring power. Due to factors such as the degree of dispersion of the pigments used and the percentage of the pigments in the ink, "POP special lithographic inks" have strong coloring power. The author has done experiments in this area, and the experimental results show that, compared with ordinary inks, the color of special inks is obviously thick and bright. Because of this, due to its strong coloring power, it is also necessary to satisfy the color of the product.
3. Better drying performance.
4. Intensity of the ink conjunctiva is large. After using a special ink to print the ink layer conjunctiva, its ink film strength is better than ordinary inks, so in terms of its friction resistance, it is relatively better. When the paper encounters turbulence in the printing process, the resulting scratch condition is relatively lighter, which is beneficial for improving product quality and reducing waste loss. This is also in line with our suitability for inks when printing aluminum foil.
Aluminum foil printing offset printing process
December 10 23:59:48, 2024
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