The surface of the polyethylene and polystyrene plastics is printed on a pad printer, and the same as the screen printing can be directly printed. However, corona and flame treatment must be performed before printing. Otherwise, the printed artwork can be easily erased, and the printing quality cannot meet the requirements. Therefore, the quality of prepress processing must be controlled.
First, surface treatment
1. High-frequency discharge treatment method. High-voltage (2 ~ 100kV), high-frequency (2 ~ 20kHz) is applied to the electrode and a corona discharge is generated between the two electrodes to generate a large amount of plasma gas and ozone, which directly or indirectly interact with the surface molecules of the plastic bottle to make the plastic surface molecules The chain introduces polar groups for surface treatment purposes.
2. Flame treatment. Using a flame processor, the surface of the bottle is subjected to a flame combustion treatment to oxidize the surface and increase the surface tension. The specific methods are as follows: (1) The ratio of air and gas is between 5% and 15%, so that the gas is completely burned in the most economical state of use. (2) The distance between the tip of the flame and the surface of the bottle is 10 to 15 mm, ie, the outer flame where the flame heat is highest is the best oxidation effect. (3) The correct contact time between the flame and the bottle can be determined by trial and error. Start the machine and process several samples. If there is no evidence of oxidation on the sample surface, or if it is not hot, the contact time is too short. If the bottle is deformed, it means that the time is too long and the contact time needs to be shortened.
Second, the identification of treatment effect
1. Submergence inspection method. The treated bottles were soaked or rinsed with water for more than 3 seconds. The observations were taken and the time for the continuous water film to remain on the surface of the bottle was calculated. If it is 4 to 9 seconds, it indicates that it has hydrophilicity, which is lower than this number. It indicates that the effect of the oxidation treatment is not good; if it is more than 12 seconds, the ink can adhere well to the plastic surface. The most appropriate degree of treatment is that the water film can remain until the water completely evaporates.
2. Surface tension test method. Ethylene glycol ether and formamide are mixed at a certain ratio to prepare a 40 dynes/cm surface tension test solution. The test solution is picked up with a cotton swab to apply a certain area to the surface of the treated bottle. If it does not break for more than 2 seconds, it means that the processing requirements are met; otherwise, it means that the surface tension of the bottle does not meet the standard.
Conclusion
The digital plate-making method was applied to the printing of the printing plate, the digital aperture printing machine was born, and the basic conditions for the production of the plate-making printing machine were created. Digital stencil printers will gain importance as high-speed printers connected to the Internet in the future. As a high-speed image output device that responds to the information society, it is expected to see further development.
Ricoh based on the simple plate-making method of the stencil technology, according to the requirements of customers to develop digital stencil technology, making it a graphic and more clear, simpler operation, higher reliability, better environmental adaptability and cheaper presses. As safety production and environmental protection will receive more and more attention, the low-power (power-saving) and ink-free (environmental) characteristics of digital aperture printing machines that do not require high-temperature fixing are in line with modern trends and continue to enrich peripheral devices. , to expand the printable paper varieties, improve the operating performance and other aspects of new technology development.