Aluminum foil printing process

The common names of gold foil and silver plate paper are advanced high-grade packaging materials developed in recent years. This kind of paper has bright color, strong metallic sensibility, and elegant and bright prints. It has played a role of icing on the beautification of goods. Now it has been used for printing various trademarks and foods, especially for tobacco and wine packaging. The paper played a great role in promoting the protection of goods, beautifying the goods, and increasing the competitiveness of the goods in the market.

At present, there are many manufacturers of aluminum foil in China, and the quality of the products is comparable to that of imported products. Due to the availability of domestic supplies, the price is lower than that of imported paper, so in recent years tobacco and wine packaging has used a large amount of such paper. Aluminum foil is a kind of non-absorbent paper. It has relatively high printing requirements. At present, the domestic printing methods include gravure printing, offset printing and flexo printing. Since offset printing has the advantages of fast product rotation and low cost of plate making, the use of offset printing is often used for printing aluminum foil. Therefore, this paper focuses on the offset printing process.

First, the characteristics of aluminum foil

Aluminum foil is mainly composed of paper base, aluminum foil, coloring layer, etc. The paper base of the type of paper is thin and thick. The thickness is cardboard, and the thin one is coated paper. There are two types of foil: embossed and glossy. Aluminum foil is not coated with silver. It is called gold-plated paper with gold layer. It has many types of coloring. Users can negotiate with the manufacturer according to their own needs.

Second, printing ink

1. Selection of inks Since aluminum foil is non-absorbent paper, impermeability inks should be used, ie oxidized conjunctiva drying ink or UV drying ink. However, the use of this type of ink is limited due to the relatively high price of the UV-dried ink, the short storage period, and the need for a UV drying device for the printing press. Oxidation conjunctival inks are inexpensive and can be printed using ordinary offset presses, so most printing companies prefer this type of ink.

2. Quality requirements of ink (1) Good transparency and high color concentration; (2) Good anti-friction property and high firmness; (3) Good water resistance and fast print drying.

3. Commonly-used ink brands available in the domestic market Company name Brand Model Ink type Jindongyang Ink Co., Ltd. Kaishi Brand TSP Synthetic Paper Ink Japan Toyo Ink Co., Ltd. Feixiang Brand 300 Type 200 Synthetic Paper Ink Dainippon Ink Company DIC POS type synthetic paper ink Dainichi Seiki Co., Ltd. Butterfly brand SF-L Synthetic paper ink

Third, the choice of printing fountain solution

Offset printing is based on the principle that the blank part of the printing plate is hydrophilic and the graphic part is inked. The correctness of the fountain solution is crucial for the printing of synthetic paper ink. At present, most printing manufacturers in China use fountain solution and alcohol (content 8%-12%) fountain solution formulated with Shanghai Lide Run Powder, but when printing with synthetic paper ink, the product will be printed for several days and nights. Irrelevant situation. The following describes a printing fountain solution that has been used by dozens of printing manufacturers in China and has proven to be effective:
Ethanol 25%-30%
Water (tap water) 70%-75%
TPP-002 0.5%-1.5%
Adjust the PH value 4.5%-6%
The drying time of the product printed by the above fountain solution is shown in the following table:
Synthetic Paper Ink Color Initial Drying Time (h) Temperature (degrees Celsius) Humidity (%)
TSP-239 Yellow 4-8 25-28 40--70
TSP-139 Red 4-8
TSP-429 Blue 6-10
TSP-719 Black 6-10
TSP-815 White 4--8
The so-called Chugan is the print is not sticky, you can enter the second process, such as overprinting other colors or bronzing and other processes. And when using other dampening fluids, the prints often do not dry out.

Fourth, brush machine and printing speed

In the printing process, in order to prevent sticking and back phenomenon, it is necessary to spray powder, but when printing a multi-color pattern printing product with a single-color or two-color printing machine...

Printing speed: The best printing speed for printing aluminum foil is 5000-8000 sheets/hour. Because the paper surface of aluminum foil is relatively smooth, when the ink is poor in water resistance, the ink will be transferred badly when the water resistance is too fast, and at the same time, the operation will also be given. The replacement of the air baffle caused difficulties.

V. Discussion

1、Printing of halftone pattern

Due to the strong metallic luster of aluminum foil and its color, it can affect the realism and reproducibility of the pattern when printing a halftone pattern. There are many printing companies that have used the ink-priming method first, and then printed the halftone pattern on the white ink layer. This method has achieved good results. However, some colors are not printed during the wet-printing process. Examples are Xu black ink. The reason is that the stickiness of black ink stickiness is small. This time, the problem is solved by adding thinner to remove ink from the black ink.

2. Effect of dampening solution on drying speed of printing products

We know that synthetic paper inks are oxidized conjunctiva dry inks. The inks that are printed on paper with offset printing are actually aqueous inks that have been emulsified. Water, on the other hand, is a very polar substance that directly hinders the oxidative polymerization of the ink molecules. Only when the moisture in the ink evaporates does the print really dry. Therefore, reducing the degree of emulsification of ink is the key to ink drying. By using an ethanol fountain solution, the synthetic paper ink has a fast drying speed, and the fountain solution is easily spread on the plate surface. Therefore, the amount of water can be reduced, and the degree of emulsification of the ink can be reduced from the surface. Ethanol is a volatile solvent. When the ethanol in the fountain solution volatilizes from the emulsified ink, the water content in the emulsified ink is relatively reduced, and the drying speed of the printed matter is accelerated. Therefore, the ethanol fountain solution should be used when printing synthetic paper inks. In the fountain solution mentioned above, TPP-002 is an auxiliary drying agent that can increase the drying speed of printed products.

3, delivery thickness

Due to the slow fixing speed of the synthetic paper ink, the excessive delivery of paper during the printing process will cause the printed product to produce a sticky back phenomenon, so it is necessary to use a drying rack to receive the paper, and the delivery thickness is generally 8-20 cm. The printing manufacturer can determine the delivery thickness according to the size of the printing pattern and the printing environment at that time.

Reprinted from: Guangzhou Printing Network