Screen printing sign technology is one aspect of the application of screen printing technology. Now all kinds of signs have been widely used in the electronic industry and household appliances, especially on the surface of various signs.
After adopting the new decoration technology, it has been displayed in front of people in a delicate and elegant form with many colorful decoration effects, which has improved the value and competitiveness of commodities.
The printing materials of signs are mainly aluminum and copper. Stainless steel and aluminum are used the most. There are also plastic, polyester, paper, etc. Aluminum signage is one of the most widely used signage varieties.
It has the characteristics of beautiful appearance, bright, high hardness, good wear resistance, wide application and large dosage. Used in machinery and electronics, instruments, meters, household appliances, daily hardware, clocks, daily cosmetics packaging, etc. There are various methods for the pretreatment of aluminum substrates. According to the application, there are mainly degreasing, sandblasting, wire drawing, polishing, and oxygen grease.
1. Degreasing: In order to make the surface of the aluminum substrate have a certain degree of ink affinity, the oil layer and oil stain on the surface need to be removed, and the cotton yarn can be used to wipe with gasoline. Alkaline solution can also be used for chemical degreasing, such as sodium sulfate 30-50g/L, sodium phosphate 40-60g/L, sodium silicate 10-15g/L, immersed in 60-70 degrees for 2-5 Degreasing in minutes.
2. Sandblasting: Sandblasting is to improve the adhesion between the ink and the metal material, usually a special sandblasting machine is used for the blasting treatment. Available river sand, filtered through a sieve before use.
3. Wire drawing: Also known as twisting, it is to process fine straight lines on the surface of the aluminum plate by mechanical friction. It is - a relatively new surface decorative treatment process that can overcome defects such as scratches on the surface of aluminum. Improve material usage. There are two types of wire drawing: thick wire method and fine wire pattern. Generally, a stainless steel wire brush with a diameter of 0.1 mm or a scouring pad with a brush is used.
Nylon abrasive belt processing.
4. Polishing: It is to overcome the surface defects of aluminum-based materials and improve the surface finish. Polishing is divided into mechanical polishing and chemical polishing. Mechanical polishing is carried out with a cloth wheel polishing machine, and chemical polishing is mostly carried out in an acidic solution, such as 15% sulfuric acid, 10% nitric acid, a temperature of 90-100 degrees, and a time of 2-3 minutes.
5. Oxidation: The polished surface of the aluminum plate has residual polishing soap, which should be wiped off with a plate gauze dipped in gasoline, then chemically degreasing, and then immersed in a nitric acid solution (1:1 ratio of nitric acid and water), taken out after 10 minutes, Then put it into the oxidation tank for electrochemical oxidation. Oxidizing solution formula: nitric acid 160-200 g/L, temperature 10-20 degrees, time 30 minutes. The oxidized aluminum plate is fully washed and dried, and a layer of oxide layer with uniform pores is formed on the surface, that is, the oxide film, which should avoid dirt pollution. The oxidized aluminum plate is best to be printed immediately. If it cannot be printed immediately, it should be wrapped with a soft paper spacer or placed directly on the air-drying rack, and the storage time should not exceed one week. The oxide layer on the surface of the aluminum plate can absorb dyes, water and other salts, so do not touch the surface with hands or greasy objects during silk screen printing. When the ink is printed on the oxide layer, the ink penetrates into the pores. The heating in the next process is to accelerate the penetration of the ink into the pores until all the surface pores covered by the ink are filled. The ink printed on the surface rarely spreads or does not spread, which ensures the accuracy and clarity of the text pattern.
6. Sealing: Its function is to seal the ink firmly in the pores and never overflow or disperse. For the parts that are not covered with ink, the function of sealing is to fill in the gaps of the oxide film and make them
Impermeable to water, enhancing the corrosion resistance of the surface. - Generally, nickel sulfate solution is used for sealing. Recipe: Nickel selenium 10-12 liters, temperature 80-90 degrees, 10-15 minutes. Use after sealing
Hands or other oily objects touch the surface and can be washed off with ordinary detergents.
