What are the common causes of deinking in UV ink printing?
First, the printing substrate film and UV ink mismatch between.
A common situation is printed on the surface of the film material UV ink than printed on the surface of the paper UV ink is more likely to fall off. The main reason is because the surface tension of the film material is low, UV ink in its surface adhesion is poor, even in the UV ink formulation repeatedly debugging a variety of adhesion promoter is difficult to achieve satisfactory results.
Generally speaking, the surface tension of film materials must reach 38mN / m or more in order to be firmly combined with UV ink, film materials before leaving the factory, the material supplier must be corona and coating treatment to increase its surface tension. The cost of corona treatment is low, but the stability of the treatment effect is poor, and the corona treatment effect will gradually weaken with the extension of time, especially when the film material is stored in a humid environment, the corona treatment effect will weaken more quickly. Therefore, in the actual printing process, the film material to be corona treated is corona treated inline in order to achieve good printing results. The cost of coating treatment is higher, but its treatment effect is stable, and the surface tension is not affected by time.
Second, UV ink over-drying, the film layer appears crystallization phenomenon.
Ink false dry phenomenon will lead to the ink layer on the surface of the print in the post-processing process off, but excessive ink drying will also cause the ink layer on the surface of the print off. UV ink printing construction if the UV lamp power is too high, it will lead to excessive drying of UV ink, making the dried ink layer becomes brittle, resulting in the phenomenon of ink layer off.
UV ink overdrying will lead to ink layer off, but also on the UV varnish or lamination and other post-processes caused by a certain impact, so that after the UV varnish on the surface of the print blossom or lamination of the print surface film off. This is due to UV ink layer crystallization, the surface of the print is excessively smooth, the surface tension drops significantly, UV varnish or laminate film layer in its surface shrinkage caused. This phenomenon often occurs in large-area field or mesh tone graphics printing process, because the operator in the printing of such live pieces, in order to ensure the printing effect often add a thicker ink layer, and worry about ink drying is not complete, so they will increase the power of the UV lamp.
Third, the ink is not evenly mixed.
When the UV ink placed after a period of time, the various additives and pigments in the ink will be different due to their own density and the formation of different free layer. To avoid such problems, the ink must be evenly stirred before printing. Printing production often encountered due to uneven mixing of ink led to the printing of the ink layer is powdered off the phenomenon, even if the UV lamp power also does not help, the common cause is too much ink pigment components in the ink hopper, the ink hopper can be taken out of the ink in the ink cartridge, and then stirred with other ink, the problem can generally be successfully resolved.