At present, the use of lithographic offset printing presses and resin (fast solid light) offset printing ink for aluminum foil printing has been quietly rising in the printing industry.
The unique charm and novel printing effect of aluminum foil packaging make the cosmetic boxes, gift boxes, high-grade tobacco and wine packaging boxes and other high-grade articles printed with aluminum foil papers, which also increase the value of the goods.
In the increasingly fierce market competition, a brand-new packaging display is undoubtedly the best choice for customers as long as they have conditions. In addition, due to the inherent metallic luster and metallic color of aluminum foil, it is not necessary to print gold, silver ink or hot stamping anodized aluminum to “make-up and decorate†the printed matter. Only a well-designed artwork and clever use of ink color can be obtained. Colorful print effect. This is also unmatched by any paper product printing.
However, for the moment, the use of offset printing machines for printing aluminum foil items has certain difficulties in application technology. In fact, regardless of any printing process or printing item, it is impossible to perfect the lack of a point. Although some problems are difficult to avoid in the printing process, they cannot ignore the defects that affect the quality of printing and the economic benefits. In general, the main difficulty is the stickiness and dryness of printed products. So, how can we eliminate the disadvantages and overcome these two difficulties in aluminum foil printing? It is worth exploring.
The basic concept of aluminum foil aluminum foil; commonly known as "gold cardboard, gold foil, metal foil." The term “steel fine paper, steel paper, aluminum paper†is essentially aluminum foil.
The so-called foil, in terms of metal material, refers to a specially processed metal foil. The thickness of this foil is 0.2 mm or less. Since the metal materials used for foil making are different, in order to show their properties, gold, silver, tin, nickel, aluminum, etc. are added before the foil words to show differences.
There are two methods for producing aluminum foil. One is a composite method in which aluminum foil and paper are adhered together. The other is that aluminum foil is coated on the paper by vacuum aluminum plating. However, no matter which way the aluminum foil is made, the surface layer is aluminum foil, and the paper is only its lining material.
It is very important for the printer to understand the printing suitability of aluminum foil paper. However, due to different views, the interpretation of printability has its own emphasis. To sum up, the principle of printability is important. Yes, the materials used in the printing process, production conditions and printing processes, etc., in their nature, function and mode of mutual adaptation. Its purpose is to improve the quality of printed products and operating efficiency.
The printability of aluminum foil is rather special because it is a composite of aluminum foil and paper, and its surface aluminum foil or aluminum foil has a metallic luster, a tough texture, and a smooth surface. In the printing process, the surface properties of the aluminum foil are directly related to the printability of the printing press, ink, and the like. Therefore, relatively speaking, the printability of aluminum foil is actually the printability of aluminum foil.
1. The surface strength of aluminum foil is very high. It can adapt to the speed of high-speed printing presses, and it can also withstand the pulling force generated by the added value of ink stickiness. It has good adaptability to improve the production efficiency and stabilize the printing quality.
2. The smoothness of aluminum foil is high, which is conducive to the transfer of ink. The imprinted ink film is flat and smooth, and the text and cable are clear and complete.
3. Aluminum foil structure is tight, there is no void, and its surface is similar to the mirror effect. Therefore, it does not have absorption properties like paper.
4. In the printing process of aluminum foil, it is sometimes found that fine oil is distributed in the ink layer in the field printing, which can be seen by the naked eye. The tiny one needs to be observed with a magnifying glass. Although this drawback has no major obstacles, it also has an impact on the quality of print in the field, the integrity of outlets, and the clarity of the artwork. The main reason for this is that the residual grease in the production of aluminum foil is in trouble. Therefore, the remaining grease must be removed before printing to improve the printability of aluminum foil.
5. The curling problem of aluminum foil is caused by the difference in physical properties between the material structures. Aluminum foil has high strength, high density, good stability, and is not easy to expand and contract; the paper has low strength, relatively small density, and poor stability and is easy to expand and contract. The properties of aluminum foil and paper are very different. These two kinds of materials with different properties are compounded by the curling factor. However, this is only its intrinsic factor. Generally, it will not curl when it is suitable for its conditions, but the ambient temperature and humidity will change, and in inappropriate conditions, aluminum foil will be induced to curl.
Printability of inks The printability of inks derives from their intrinsic structure and their inherent physical and chemical properties. However, in the application process, it must be confirmed by the entire journey on the printing press, the comprehensive drying process on the substrate, and the verification of the print quality. Of course, the printability of the ink is not isolated, but is reflected in the coordination of printing presses, printing materials, and other conditions.
The suitability of the ink in the press stroke is not discussed in this paper. The focus is on the fixation of the ink on the aluminum foil paper (ink initial drying), because it involves two key issues of stickiness and dry function of the printed product.
In a nutshell, infiltration is the basis for the fixation of the ink on the substrate; the fixation speed is the condition for the ink layer to dry in the medium term; the medium-term drying time is the key to the quality of the ink layer conjunctiva.
1. Infiltration is the basis of fixation. Resin-based medium and high-grade offset printing inks are mainly composed of resin, dry vegetable oil and ink oil. Among them, the resin is soluble in dry vegetable oils in the high-viscosity phase; ink oil is a low-viscosity phase, with miscible (not really soluble) state and high viscosity equal combination. Since the effect of the ink oil is only to dilute and reduce the viscosity of the front phase, the ink is adapted to the application on the printing press. Therefore, when the ink oil completes its "mission" (the moment when the ink is printed on the substrate), it must be immediately Leave the ink system and leave as fast as possible. This is the prerequisite for ink fixation - penetration.
2. The fixing speed is the condition of the ink layer drying in the middle. The fixing speed is mainly determined by the instantaneous penetration of the ink oil miscible in the ink system on the substrate. The greater the instantaneous penetration, the faster the separation of the high and low two-phase viscosities in the ink, the higher the concentration of the high-viscosity components of the resin and the dry vegetable oil can be sharply increased, and the instantaneous physical change causes the inner layer to form a gelled state to be fixed on the printing. Things. Whether the high and low phases can be completely separated not only determines the fixing speed of the ink layer, but also relates to the medium-drying time of the ink layer. (To be continued)